WORLD HEALTH ORGANISATION MON D~ALE ORGANIZATION DE LA SANTE

Uganda 17 AFR/Oncho/8 Rev.l

~~. : ·~:·~ . WHO/Oncho/30.65 Rev.l . .. ·.. ENGLISH ONLY

(Conclusions et recom­ mandations en fran9ais)

ONCHOCERCIASIS AND.ITS CONTROL IN UGANDA

by . 1. 2 M. J. Colbourne and R. W. Crosskey WHO Consultants

.. CONI'ENTS

1. Introduction • • • • • • ...... 3 ,. 2. General description of Uganda ...... 4 Onchocerciasis distribution • ...... 6

Uganda- and Africa as· a~ whole • •. . • • • • • • • • • • • . c... . . 6 Broad pictUre of onchocerciasis in U~anda ...... 6 Onchocer~iasis foci in Uganda •.•••••• ...... 8 3.3.1 The main proven foci • • • • • • • • • • • • • • • • 8 ~.,.2 Lfttle known ahd suspected foci · • • • • • • • • • • 10 3.3.3 Known vector areas without known disease • • • • • • 11 3.3.4 . Negative· areas • • • • • • • • • • • • . . . . 11 4. Onchocerciasis· s\lrvey ·and control to date in Uganda ...... 11 4.1 · Vector· Contr.ol Division ·(vCD) •••• ...... 11 4.1.1 Constitution and.functions •• ...... 11 4.1.2 Work of the Division to date • ...... 12 4.2 Clinical work ...... 16 4.3 Other work •• ...... 18 5. Importance of onchocerciasis to Uganda ...... 18 1 Department of Social Medicine, University of Singapore. 2 Conunonweal th Inst;itute of Entomology, London. AFR/Oncho/8 WHO/Oncho/30. 65 page 2

~

6. Discussion of special problems in Uganda . . • • • ...... 22 6.-1" The border problem • ...... 22 6.2 Non-anthropophily of vectors • . . . . ' ...... 22 6.3 Place of drug treatment ...... 24 6.4 Eradication by attrition • . . . . . • • • ...... 24 6.5 Do-it-yourself dosing ...... • • • • • • • • 26 Conclusions and recommendations ...... Conclusions and recommendations ...... Z7 7.1.1 Main conclusions • • • • • • • • • • • • • • ...... 27 7.1.2 Additional technical conclusions •••••• ...... 29 7.1.3 Conclusions on priorities ...... 30 7.2 Phasing of control and its integration into a communicable disease service ...... 31 Conclusions et recommandations (en fran9ais) • ...... 33 7.1 Conclusions et recommandations ••• . . . - ...... 33 7.1.1 Principales conclusions • • • • • • • • • • • • • • • • • 33 . 7 .1.2 Conclusions techniques supplementaires • • • • • • • • • • 35 7.1.3 Conclusions rel.a~ives aux priorites ••••••••••• 36

8. Acknowledgements • ·• • • • • • ·• • . . . • • ......

References ...... • . . . ~· ...... 39

Ann,ex 1. .. I.t1ne~ar'Y, • • • • • . • • • • • • • • • • • • • • • • • • • 42

Annex 2. Detailed review of main onchocerciasis foci • • • • • • • • • 45 Annex 3. Historical resume of work to date...... 76 Annex 4. List of personal entomological findings ••••••••.•.•••• 8o

Map. Approxim~te known distribution_of onchocerciasis in Uganda

::. AFR /Oncho/8 WHO/Oncho/30.65 page 3

··r-·· \.' .

.. ; ;- .·. ,._ 1. INTRODUCTION ..; ! :.,_. The writers visited Uganda from 9 October until 14·Noverriber 1964, and the terms of reference were "to make a preliminary assessment of the onchocerc-iasis problem in that country and to advise on control methods with a view to establishing priorities for the initiation of control campaigns in the various foci".

This assignment required investigation into every aspect of past and present work on onchocerciasis and its Simulium vectors·, ~d this report is iri part a' digest of all · that is known of the disease in Uganda and of the control work that has already been carried out. The conclusions presented in this report (Section 7) derive from the · threetypes of available infoma.tion: firstly from,consultation and discussion with every­ one interested in or in any,~ .way. ·concerned with onchocerciasis and its control (officials of the Ministry of Health, personnel of the Vector Control Division, senior and district medical officers responsible for regions and districts where the disease occurs, d!strict health inspectors, medical assistants, staff of mission hospitals and

speciali~ts at _the ~kerere University College); secondly fx-om c;locumenta.ry info~tion including departmental files, published scient~fic papers and semi-published documents '; • · ..1· • •. .·· • • . • . • ·' -··.· such a~ WHO. 7eports; and thirdl;y: from the writers'- extensive study tour .of all the .main

~reas . .. : onchocerciasis in. the country.. .,, . . . '. Three and a half weeks.rwere spent in the field; all the'tnain onchocerciasis areas being visited: by a single· long•.circuit safari (full d~tails of the itinerary are given in Annex 1). This tour- of.· the foci ·was paJ7ticularly valuable in demonstrating the different types of environment in which the disease occurs, the varied topography influencing the prospects for control, and ~e diverse ways in which onchocerciasis and • • : !'• ·.'' . .'.. • .·• Simulium can impinge on the economic well-peing of Uganda. While on safari in the ----- ·.. - ...... ~ , .. - . : . various foci, collectiol)S were made of vector. Simulium and these are enumerated in Annex 4. '. . . . ~~------~ Attention should be drawn to a few points concerning the report. It was considered undesirable to burden the body of the report with too' much detail about the main onchocerciasis foci, and therefore most •of·. the factual data on these foci has been ·placed in Annex 2, where it is readily available for• the· more specialist reader. AFR /Oncho/8 WHO/Oncho/30.65 page 4

The Vector Control Division figures frequently in the report, and to avoid repetition of the name in full the abbreviation VCD has been adopted.

Throughout the report, following a practice of the VCD, the name Murchison Nile has been used for that stretch of the River Nile between Lake Kyoga and Lake Albert, and the Murchison Nile Focus is used for that onchocerciasis area centred upon it; however, it should be pointed out that on maps both the stretches of the Nile from Lake Victoria to Lake Kyoga and that from Lake Kyoga to Lake Albert are called the Victoria Nile. Since there are foci on both stretches it is far the _most convenient for the purposes rJf this report to distinguish the Kyoga-;~1 bt:rt s t.retch by the name Murchison Nile.

The very greatest co-operation and courtesy was received from all concerned with this visit to Uganda, and the writers have pleasure in acknowledging this more fully in Section 8.

2. GENERAL DESCRIPl'ION OF UGANDA

Most of Uganda lies between 3000 and 4500 feet aboye sea-level and forms part of the ancient landmass of Africa which has not been overlain by the sea, but the periphery of the country consists in part of mountain massifs which rise far above the flat or undulating hinterland. In the east on the Kenya border Mount Elgon attains more than 14 000 feet, and the Ruwenzori on the western (Congo) border rises to nearly 17 000 feet with perpetual glaciers; in the south-west the irregular highlands of Kigezi are in part over 8ooo feet arid the extinct volcanoes of Mufumbiro (forming the frontier with Rwanda) reach over 13 000 feet.

Uganda is land-locked (bordered to the south-east by Lake Victoria) and its rivers are ~ithout direct outlet to the sea, feeding almost entirely to the Nile wbich bisects the central·table-land of Uganda in a meandering course from Lake Victoria to the Sudan border in the ·extreme north of the country. The Nile within Uganda is in three parts; a first stretch frOm Jinja to the swampy Lake Kyoga in the south central part of the country, a second stretch from Lake Kyoga to Lake Albert, and a third stretch from the northern outlet of Lake Albert to the Sudan "bend" at Nirnule. The first two stretches AFR:/Oncho/8 WHO/Oncho/30 .• 65 page 5

(Victoria Nile and Murchison Nile) flow over precarnbrian basement and are largely rocky with rapids.and falls: the third stre~ch (Albert Nile) is broad and smooth, flowing over sedimentaries. The western boundary of Uganda with the Congo lies to a larg~ extent along .watersheds, that part of the boundary in We~t Nile District lying on the • 4. ' •• divide betweeQ headwaters of the Congo and:Nile rivers; on~y in a few places do rive~s . ' - -··· originating o~ts~de.en.ter Uganda territory.. On the other hand virtually all the waters of Uganda.leave it by the Nile.

Most -of Uganda, being densely populated by African standards,' is heavily cultivated (principally with banana, cassava, cereals, sugar, coffee, tea and cotton) and the natural .vegetation has been correspondingly reduced. Large stands (some 60oo square miles altogether) of undisturbed tropical forest still exist, mainly as follows: in crescentic bands on the slopes of Mount Elgon and Ruwenzori; Budongo, Siba and Bugoma Forests (Bunyoro District); Kibale Forest (Toro District); Kalinzu Forest (Ankole District); and the Maramagambo and impenetrable forests (Kigezi District). In other areas where there is no cultivation the natural vegetation consists of open savannah woodland or. 'rolli.ll8: grassland With only scatt~red trees ~

The rain(all i~ between 35 and 70 inches a year in almost all qf Uganda, eJ(ceeding •. . . : ~ ;. •. . .'. . . ~ 70 in.ch~ only on ,Mo~:t El.gon and in parts of Kige~i. The rainfall distribution is · •. • • • ~ •- ~ I • .. ,." • • .

sea~ons seas.qnal.;. ,.· .. . but . .the dry . ... ·:. are much less severe than in the. savannahs of West Africa • The rainfall and relief is such.that almost all the rivers and streams .flow throughout ·' ~ · , • '· ., . t : •.• 'i . ; 1. ' • ·•- _ ·-· ~ •. ·· • • tll,e year; ~ost watercours,e,~;·:~-~.;;, Sl'rift,, . rocky and turbulent where theY. traverse the uplands or x:un down from,"l!r~ mountain massifs, but many.of them degeqe,rate into papyrus-choked swamps on reaching the base plains.

The area of Uganda is 93 000 square miles, but the land surface only 80 000 square miles; almost all the land area is inhabited except for the two National Parks. The population 'is no~ about 6 500, ..-ooo .Md the me~~ populatio~ density appr~imately 80 to the ; ,, square mile. Distribution ~fpopulation is irregular and density is lo~est (0?59 per square mile) in the north-east and west-central parts of the country; in the south-east . ' against Lake Victoria and northwards to Mount Elgon, in southern Kigezi District, parts AFH /Oncho/8 WHO/Oncho/30.65 page.6 of the Ruwenzori and West Nile District many areas have more than 300 or 400 inhabitants per square mile. Almost everywhere the rural population lives in scattered homesteads, often dotted on the hillsides among banana groves, and large close-knit villages are very exceptional; as a rule there is no population actually within the true forest, but the cultivated areas abutting the forest are often densely settled. The main occupation is subsistence farming and production of cash crops such as cotton, sugar, coffee and to a lesser extent tea; other occupations include fishing, hunting, cattle droving, lumbering, and mining. Some of these occupations involve substantial migrations of population from their home districts into distant areas. As yet there is little industrialization, although this is beginning in the Jinja area following the generation of hydro-electric power from the Owen Falls dam. Tourism is an infant industry with some potential.

3. ONCHOCERCIASIS DISTRIBUTION

3.1 Uganda and Africa as a whole .· Onchocerciasis is endemic over much of the tropical regions of Africa from Liberia and Guinea in the west through equatorial Congo to East Africa. Uganda now virtually lies on the eastern extremity of this distribution; the only areas of onchocerciasis existing further to the east are the small pockets of infection remaining inwestem Kenya among persons infected there before eradication of the vector (a very small area of Simulium neavei infestation probably still exists in Kenya at the southern tip of the "Elgon crescent") • There are two vectors of African onchocerciasis, SimuliUm damnosum and Simulium neavei, both of which occur in Uganda and are responsible for disease transmission there.

3.2 Broad picture of onchocerciasis in Uganda

Onchocerciasis in Uganda occurs in relatively small foci and nowhere in the truly enormous and diffuse endemic areas which are characteristic of the disease in West Africa. . . ' . The pattern of the Uganda foci is determined entirely by the factors governing the distribution of the vectors, and there is a very definite localization of the disease to ar~~. around the periphery of Uganda where sui table breeding conditions for S • darnnosum and S. neavei exist. AF'.R /On.,;l.~o/8 WHO/Oncho/30.65 page 7

The vectors require freely flowing rivers and streams for their development~ and adult~ neavt"! commonly require the presence of forest cover; neither of these conditions is provided by much of the central area of Uganda with its sluggish rivers or p:.~.pyrus swa.mps 1 and onchocerciasis is almost certainly absent from much of the interior plains. Significant exceptions to this are the two onchocerciasis foci centred upon ~~he Nile 1 where the exposure of resistant rocks along the Victor5.a Nile und the I~urch:tson Nile -orovides tut•bulent stretches of water suited to ------S. damnosum develor mcnt 1 with the consequent appearance of the disease. The peripheral foci are mainly

' . . , I associated with hilly or mountE.~.inous country penetrated by swift rocky streams and rivers 1 and onchocerciasis mainly affects the population living on the irregular·slopes

O'-" in th~ foothill valleys of the border mountains (Mount Elgon~ Ruwenz<>ri; Kigezi highlands); elsewhe're the disease is not obviously associated with a heavily dissected ter~ain 1 but only with undulat5.n~ or slightly hilly country as in West Nile District or Budongo Forest. It is probable that some of the onchocerciasis foci on the western side of Uganda extend in places across the Congo border (e.g. in. the Goli area of southern West Nile District and in +he Kayonza area of Kigezi) 1 but this has not yet baen established.

It is noteworthy that in Uganda the transmission of onchocerciasis does not coincide v1:!. t!1 the breeding distribution of the vectors. For example on Elgon th~~e·· .i"s 1i ttle breeding of s. ne~ above about 4500 feet_,. and on eastern Ruwenzori slopes lfttle bre~d.ing of S. damnosum above about 4100 feet 1 yet on both mountain massi'fs heavy iricidences of the disease occur to altitudes of 6ooo feet and more. In some of its ioci (e.g. Elgon and Kigezi) S. neavei bites in forest at altitudes above those of the breeding sites and this largely accounts for the discrepancy between vector breeding di$tribution and disease incidenc.e~ but in other areas it is not easy to correlate onchocerciasis survey findings satisfactorily with fly behaviour. In some foci it has so far proved extremely difficult to find the Simulium vectors as adults, even though the.ir ~arval distribution is known in some detail. AFR /Oncho/8 WHO/Oncho/30~65 page 8

3.3 Onchocerciasis foci in Uganda

3.3.1 The main proven foci

Onchocerciasis as at present known in Uganda occurs in eight main areas which the writers consider to be separate proven foci of the disease on the evidence available (see accompanying map). Seven of the foci were visited omitting the minor focus of Bugoma Forest about which little is yet known; only a brief stop was made at the JinJa Focus.

In Table 1 the main features of each of the eight foci are detailed, including estimates of the area and population at risk. A few words of explanation are necessary concerning these estimates: none of the foci listed, with t11e possible exception of Jinja, has been investigated in sufficient detail for precise figures to be given either of the size of the focus or of the number of persons at risk within it, and in any case it is of course always difficult to delimit a focus very exactly. In the absence of any one reference source the figures shown in the table have been compiled from a combination of documents such as literature references, census reports, and maps, combined with discussions with VCD personnel; the figures are very approximate only,

and the writers are aware that they may later prove substantially inaccurate, bu~ for the present it is believed they are the best that can be given and that they provide· a reasonable means of comparing the scale of-one focus with another and of appreciating the magnitude of the onchocerciasis problem as a whole .in Uganda.

Originally it was intended to include in the table some detail of the incidence of the disease and eye involvement in each focus, but it .. was found that insufficient data is as yet available to permit any useful numerical tabulation.

Itshould be noted here that Barnley has recently compiled figures for the population living in the various foci which are different from those of the writers, . . :· .-. and Barnley's figures are given in a footnote to Table 1. The differences in the two estimates are due to the difficulty of defining the limits of the foci. The biggest difference is in the Victoria Nile focus which has already been controlled. AFR /Oncho/8 WEO/Cncho/JC.65 page 9

TABLE 1. THE ONCHOCERCIASIS FOCI IN UGANDA

Estimated . Es·timated ... .. ~wame -·or-- .... -·AOiiiiiiiStrS.ti·ve · · ·a·rea 1n ·· Brief focus population Vector species foous districts square at rl.·sk*· description : ~1~

Jinja** Busoga and 1 6oo 225 000 S. damnosum. .. . ~l..~t._op_en .country. • ··· Merigo · ·- · · · bisected by river Districts Nile. Cultivated or with forest relicts

Mount Elgon Bugisu and 600 120 000 S. neavei Mountain slopes Sebei and foothills, Districts heavily settled. and cultivated below forest

, Murchison Acholi and 400 10 000 S. damnosum Open undulating Nile Bunyoro inhabited grassland or wood­ Districts area land, largely_ uninhabited .. National.Park - . I West Nile West Nile 2000 220 000 S. neavei ,Open country, hilly District I? S. darnnosum or undulating savannah with wooded valleys. No true forest, · · grass ·plains agains.t Congo border

Budongo** Bunyoro 300 7 000 S. neavei Pense rain forest Forest District and some adjacent scrub and c·u1tivation. Not mountainous.

Bugoma Bunyoro 200 3000 S. neavei . Thin forest and Forest District adjacent scrub and cultivation. Not mountainous.

Bamley estimates populations as follows: Victoria Nile (Jinja) 618 583; Mount·· Elgon 209 108; Gulu (Uurchison Nile) 33 067; West Nile 170 851; Escarpment forests (Budongo and Bugoma) 41 897; Ruwenzori 130 362; Kigezi area 124 730; total population of foci by Barnley's estimate 1 328 598. ** These foci controlled. ·• ' ~.. •. :: AFR /Oncho/8 WHO/Oncho/30.65 page 10

TABLE 1. THE ONCHOCERCIASIS FOCI IN UGANDA (continued)

I Estimated Estimated Name of Administrative area in Brief focus population Vector spec_~-~~ districts .. ~ .. square description focus at risk* miles

Ruwenzori Toro District 1 000 100 000 s. damnosum Flattish or ? s. neavei undulating foothill area below mountain massif, open .savannah forest on higher slopes .· .. .. Kigez1 Kigezi 6oo 40 000 s. neavei Precipitous hill- Highlands District ? s. damnosum sides and irregular mountain ranges, partly cultivated, dense forest at high levels I All eight main foci 1 6 700 725 000 * Barnley estimates populations as follows: Victoria Nile (Jinja) 618 583; Mount Elgon 209 108; Gulu (Murchison Nile) 33 067; West Nile 170 851;· Escarpment forests (Budongo and Bugoma) 41 897; Ruwenzori 130 362; Kigezi area 124 730; total population of foci by Barnley's estimate 1 328 598.

3.3.2 Little kno~m and suspected foci

In addition to the eight major foci enumerated above there are some other areas in which Onchocerca volvulus infections are known in the human population but wh~~e no adequate surveys have yet been done to assess the extent of the disease. These areas include: Rhin9 Camp and Rigbo on the Albert Nile (West Nile District); Ndaiga Bay area at southern end .of Lake Albert (now Bunyoro District); Kibale Forest area south-east of Fort Portal (Toro Dbtrict); Kalinzu Forest area (Ankole District); and the i•1oyo ! ,-' ' ••• • •· .•• area of Madi Dist~ict.

From the terrain and its affores~ation a few other areas are suspected as having onchocerciasis but there is no evidence at the moment: examples are the northern tip of Karamoja District, the area on the Sudan border north of Madi Opei in Acholi District, and .. Kadam area in southern Karamoja •. AFR./Oncho/8 WH9/0ncho/30.6~ page 11

3.3.3 Khown vector areas without known disease

Simulium damnosum occurs in some localities where no onchocerciasis has yet been

demonstrated1 for instance on the Kagera River near Kikagati (the boundary of Ankole

District with Tanganyika) 1 near the Kafu and Muzizi river crossings on the Hoima-Fort

Portal road1 at the Aswa River crossing on the Gulu-Kitgum road and the crossing of the

same river on the Lira-Kitgum road 1 at the crossing of the Angweji River on the Gulu-Moyo

road~ and on the lower Ora River in West Nile District near the Albert Nile. In some of these localities S. damnosum is certainly non-anthropophilic.

3.3.4 Negative areas

It cannot be asserted positively that onchocerciasis is absent from any area~ but it is thought useful to indicate briefly those areas which are most probably completely ' I • • ' ~ ; free from the disease (judging from the absence of anr record of o. volvulus and from the unsuit~ble nature of the terrain for the vectors). The main areas almost certainly negative are: almost all of Buganda except the west bank of the Victoria

Nile (Jinja focus); all of Teso.·:·. and Bukedi Districts; almost all of Lango District; most of eastern Acholi and possibly all of Karamoja District; grass-plains of eastern Ankole District.

4. ONCHOCERCIASIS SURVEY AND CONTROL TO DATE IN UGANDA.

4.1 Vector Control Division (VCD)

Until now almost all the survey and control of onchocerciasis in Uganda has been

carried out by the Vector Control Division of the Ministry of Health 1 and the functions and achievements of this unit are detailed below.

4.1.1 Constitution and functions

The VCD is a primary unit of the Ministry of Health directly responsible to the chief medical officer. It is directed by a senior entomologist who is assisted by two entomologists; in addition there is a parasitologist now in training. The D.i vision has four field officers~ and it is upon their reliability that the success of the Divisio work very largely depends. About twelve junior staff fulfil various functions. The AFR /Oncho/8 WHO/Oncho/30.65 page 12 annual budget of the Division in recent years has been between £ 10 000 and £ 14 000 ...... exclusive of salaries~ of which half or more is spent on sleeping sickness work in Busoga District. A reserve fund may be called upon in emergency ~-·and was used f-or instance when re-dosi~ of the Victoria Nile became necessary. The headquarters of the VCD are in Kampala and it has its o~m buildings and transport. Three outstations of the Division are planned~ for Fort Portal (Western Region), Mbale (Eastern Region) and Gulu (Northern Region); the first of these may open at Fort Portal during 1965.

The Division now has both advisory and executive functions~ but originally was formed only to advise on the control of vector-borne disease; in addition to

onchocerciasis it deals at present with malaria~ schistosomiasis 1 relapsing fever and

plague 1 and is responsible for the surveillance of certain sleeping sickness areas. Because of its many duties it is unavoidable.that it has to act as a fire-brigade to

deal on reque~t with outbreaks of disease as they occur; much of its onchocerciasis control work has followed requests of this nature even though this disease is essentially an endemic one without exacerbations. The Division has responsibility for training otner cadres of the Ministry of Health in the elements of vector control.

4.1.2 Work of the division to date

It will be convenient to consider the work of the Division focus by focus~ but this does not imply that the picture of the disease as a whole in Uganda has been in any way neglected by the Division. Some general accounts of onchocerciasis in the country have appeared (e.g. Barnley 196la). Annex 2 to this report is largely a resume of the work of the Division.

·The Division's work has been undertaken in the following main foci:

{a) Jinja (Victoria Nile) (b) Mount Elgon (c) Murchison Nile, (d) West Nile (e) Budongo Forest (f) Bugoma Forest (g) Ruwenzori (h) Kigezi. AFR /Oncho/8 WHO/Oncho/30 .65 page 13

· •• 1 Each of these isconsidered in turn below. In-addition minor surveys and observa~ions haVe })een made in. many other parts of the country with the object of completing the. picture .of onchocerciasis and vector distribution in Uganda.

(a) Jinja (Victoria Nile)

The existence of onchocerciasis and of S. damnosum as an iJ1tens.e ~~-~ing nuisance had been known at Jinja for many years, but the decision to build the Owen ~alls dam with consequent industrialization of the Jinja area made it necessary in 1948-1950 to consider the c.ontrol of S. damnosum (which bred for many miles along the rapids of the Victoria Nile). Aerial spraying. of DDT was carried out in 1951 and produced_ only temporary diminution in fly incidence, but showed considerable larvicide effect. Thereafter DDT was used only as a larvicide, initial applications being made in 1952 .. . .. which seemed .to eradicate the fly completely from Lake Vi?toria t~ Lake Kyoga. ···--· ...... However a few flies were caught between 1953 and 1956.. and the Nile was re-dosed. in 1956 ...... through the sluices of the Owen Falls dam {by then completed) • Follo~ing .t}l~s. ~f:>sing no flies were foun~ until. November 1960 when small numpers were biting again, pJ'9mpting . .• . . . ; ~ .... a re-dosing in 1961. Flies then disappeared until 1964, and this year the river was dosed once more; at the time of writing flies ha7e not reappeared. A full report on the work at Jinja is being prepared by McCrae. The picture at Jinja is of "intermittent eradication" for periods of about four years; . the spurce of reinfestation has not been determined.

(b) Mount Elgon

Onchocerciasis was recognized in this focus in 1951 but only small surveys \'rere car~ied out until 1955.when the proposal to build a coffee research station at Bu:f"wnbo (in the most heavily _infected area) brought about an attempt.to deal with the problem. A large-scale survey took place in 1956 in preparation for the erad.ication of S. neavei from Mount Elgon. From January to April 1957 eradication by DDT as a_larvicide.was attempted but failed. It appears that there were two main reasons for this failure: firstly that S. neavei immature stages occurred on a second crab species living at higher altitudes than Potamon niloticus (to which S. neavei was then thought 'tO .be AFR /Oncho/8 WHO/Oncho/30 .65 page 14

confined) in undosed streams, and secondly that not all of the smaller tributaries had been discovered. An incidental finding from the Elgon work was that DDT adsorbed on vermiculite and placed in the streams was much less satisfactory than freely run in liquid insecticide. The division has as yet no plans for further control in the Elgon focus, pending opening of the Mbale outstation.

(c) Murchison Nile

Preliminary work in this area between 1953 and 1958 showed that S. damnosum was breeding in large numbers along a fifty-mile stretch of the Nile from Amenyi rapids to Murchison Falls and in limited parts of a few tributaries (especially the Aiago); little biting of the flies was occurring at the Nile itself, but severe biting was taking place many miles from the main river at Koich where a heavy incidence of onchocerciasis was found. A proposal to construct a hydro-electric plant at Karuma Falls on the Murchison Nile led to an attempt by the division to eradicate S. damnosum by dosing the main river from a perforated polythene pipe stretched from bank to bank. This attempt failed and breeding was fully re-established in the Murchison Nile within six months. The possible reasons for failure were incomplete dosing of the main Nile or missed breeding sites in unsurveyed tributaries. The problem of transmission in the Murchision Nile focus is at present being investigated. This focus was the scene of experimental aerial bombing of rivers with larvicide enclosed in various types of containers; some encouraging results were obtained but have not yet been followed up.

(d) West Nile

The VCD foundS. neavei in this area in 1951 and during a later survey (1954) concluded that this species was responsible for transmission in the Bondo-Arivu area, where onchocerciasis had already been shown by Nelson to be a severe health problem. In 1955 a pilot control scheme was carried out in the Bondo-War area, with initial disappearance of larvae; however slow reinfestation of crabs occurred after about 18 months. The control area formed only a small part of the whole West Nile focus and various other surveys (both parasitolocical and entomological) have been made from time to time to gain more inforwation about the focus. S. damnosum has·· more recently been found in several rivers in the West Nile focus but is considered, in the absence of known man-biting, to be non-anthropophilic here. AFR /O!lcho/8 WHO/Oncho/30.65 page 15

(e) Budongo Forest ''

Following reports of onchocerciasis and Simulium biting in the Budongo Forest area the VCD found on a survey in 1955 a high incidence of the disease, particularly among the labour force of the Budongo sawmills and among the students and staff of the Forestry Training School (all persons with three-year residence in the area being infected). Extensive breeding of S. neavei was found in three stream systems flowing through the Budongo and Siba Forests and adjacent scrub, and a control scheme was planne~! mainly designed to protect thqse persons working in and near the forests. DDT dosing began in November 1955, and continues at present at six-weekly intervals; no adult flies have been found despite repeated assessment since November 1957. Dosing is carried out by four interested parties on the recommendations of the division, who also supply the insecticide; assessment of the effectiveness of control is made by ... ····· the VCD about three times,a year. Because of the good results (no flies at all for seven years) the division _j.s considerin.g stopping dosing to determine ,~thether . . . . . ' eradication has been achieved, but is,understandably he~itant because ,oneS. neavei larva was found on a crab during an assessment survey in 1961. S. damnosum has been found during surveys of the Budongo area in the Waki River, but apparently does not bite man.,

(f) Bugoma Forest

Little is yet known of this focus. The VCD carried out a survey of the area in May 1963, w~ch showed the p:resence of abundant S. neavei adul,~s, but remarkably little onchocerciasis (perhaps of the order of six per cent. among persons_ living ar~und the forest).

(g) Ruwenzori

Surveys by the VCD between 1950 and 1960 showed that onchocerciasis occ_urred around the foothills of the Ruwenzori mountains and that .the. main vector. was S. damnosum breeding in a radial series of rivers, chiefly the Ruimi, ff!Ubuku, Sebwe, · Nyamagasani, Kanyampara and Lubilia. Some of these rivers have been dosed and some of the valleys surveyed for onchocerciasis. On the Ruimi River the establishment of a prison farm AFR /Oncho/8 WHO/Oncho/30.65 page 16 required the control of S. damnosum which was an intolerable biting nuisance at the prison site; a scheme of fortnightly dosing, worked out by the Division and put into operation by the prison authorities, continues successfully. In 1960 the D.ivision started experimental dosing of the Nyamagasani River to find out whether local health staff could operate such a scheme successfully by dosing the main river and some of its infested tributaries themselves; at first there was some success but flies later reappeared. In 1962 the Nyamagasani experiment had to be abandoned because of civil disturbance in the area. In the Mubuku valley members of the VCD took part in a detailed survey of onchocerciasis at Bugoye carried out in 1960 (Woodruff et al., 1963). On the Kilembe River the Division has found that no S. damnosum occurs, although the river would normally be suitable,_because of pollution with tailings from the Kilembe copper mines. The VCD has carried out other investigations on rivers round the north side of Ruwenzori where s. damnosum appears to be completely non-anthropophilic, and also in the S. neavei areas on the flanks of the massif; so far they have foUnd no evidence that S. neavei bites man in the Ruwenzori area. Further developments await the opening-of the Fort Portal outstation, scheduled for 1965.

Onchocerciasis and S. neavei were originally discovered in this area in 1948, and an extensive survey was undertaken by Barnley in 1949. Thereafter no work was done in this area until 1962, when (following a request from the District Medical Officer) another detailed survey was made by the Division with particular concentration on the tea-growing area of Kayonza; a high·-incidence of onchocerciasis was confirmed and adultS. neavei obtained in numbers in one area of the impenetrable forest. No dosing has been done in Kigezi.

4.2 Clinical work

Some information about onchocerciasis in Uganda is available from medical records, contained for instance in the reports of clinicians, either as the result of observations made during their routine work or as the result of special surveys. For convenience all this is referred to as "clinical work". AFR /Oncho/8 WHO/Oncho/.30.65 page 17

Among the publiahed work two surveys are of special interest, that of Nelson. (1958b) from Bondo in. West Nile District and that of Woodruff et al. (1963) from Bugoye in.the.Ruwenzori foothills of Toro District. -Both these reports give full information about the patients examined, but they are essentially_clinical accounts and make no attempt to estimate the ~tent or prevalence of the. disease in these districts (although Nelson shows that at least one third of a population of 1200 living in the Nyara valley were suffering from the disease).

An extensive investigation, as yet unpublished, has been made in West Nile District by Dr Peter Williams of the African Inland Mission situated at Kuluva, a few miles south of Arua. Full details must await publication but Dr Williams has· kindly mad~ available to the writers some of the more important findings. He has found onchocerciasis distributed evenly in the villages of the Anyau'and Ora river·systems and in the river valleys south of the Ora system. He has not found cases·· in the area between the Anyau and Ora. He has seen a few cases at Rigbo and Rhino

He has been1particularly interested in the effects of the disease on the eyes and has carried out careful ophthalmological examinations on. -1000 patients with positive skin snips. Of th~se patients 511 were over the age of 31 years., 334 were ·between 16 and30 years old, and 155 were under the age of 15 (including one infant of nine months).

Of the youngest group 32 per cent .• had eye signs, an~ of .the oldest. group 76 per cent.

In 25 per cent. of the whole g~QUP m!crofilariae were present in the anterior chamber; 2.6 per cent. were economically blind. In.another survey he found that 26 per cent. of an infected group from r-1adi county had a v;s\Ui,l acuity of less than 6/24.

Dr Williams' figures do not give an indication of the prevalence of the disease in West Nile District but it is of interest that he was able to find between lOO 'and 120 patients with a positive skin snip each day and that the thousand cases came trom 10 local! ties in only a small part of the focus. Dr Williams thinks that the incidence · of the disease is increasing. People are now moving into areas that wel"e left uncultivated previously •.

:· ·. ( . . ~ AFR /Oncho/8 WHO/Oncho/30.65 page 18

Another source of information about the disease is the Annual Report of the Ministry of Health. These reports have given accounts of the increasing awareness of the importance of the disease, of investigations into its prevalence and of measures taken to control it: they also record the numbers of cases reported annually. For the years 1955-1959 the numbers of cases reported were:

1955 1956

558 661 779 298

It is obvious that these figures merely represent the cases diagnosed in medical treatment units. Figures given else\'lhere in this report will show .that they bear no relation to the actual number of people in Uganda suffering from the disease. The fluctuations probably represent changes in awareness on the part of clinicians, not of course any actual change in the incidence of the disease.

4 .3 Other \'lork

In addition to the work of the VCD and the observations of clinicians mentioned above there have been a few other studies of onchocerciasis and its vectors in Uganda. These include the work of Gibbins & Loewenthal (1933) on onchocerciasis near the Victoria Nile; of Gibbins between 1933 and 1942 on the Simuliidae of Uganda (various publications); of the Department of Microbiology at the Makerere University College; of the Mulago Hospital clinicians who have been interested in special aspects of the · disease (not related to control); of the "Liverpool Group" including Hynes and l;Jilliams on problems of crab ecology in relation to S. neavei; and of Isabella Gordon on the taxonomy of crabs associated with the S. neavei complex.

5 • IMPORTANCE OF ONCHOCERCIASIS TO UGANDA

The direct medical effects of onchocerciasis are considerable. In addition the disease interferes with the economy of the country by preventing the effective use of land for agriculture or industry. Closely associated with the problem of control is the state of awareness of the problem, which affects both popular co-operation in the control of the disease and the provision of the necessary funds for carrying out control. Both may be lacking unless the effects of the disease are understood. AFR /Oncho/8 WHO/Oncho/30.65 page 19

In the absence of a nation-wide survey it is not possible t'o give exact figures for the numbers of people suffering from the disease, but some useful estimates are available. It is probable that between 700 000 and 8oo 000 people 11 ve in areas affected by the disease; of these some 225 000 living near the Victoria Nile have been freed from risk of further infection. The majority of the remainder live in two large infected areas, about 220 000 in West Nile District and about 120 000 on the slopes of Mount Elgon; the rest are in the other foci listed in Table 1. The risk of infection is not equal everywhere, and Prentice (Senior Entomologist of the VCD) estimates that about 175 000 people live in areas where the risk of infection is'ver,Y high.

'. ·~ 'j . The commonest pathological results of infection are to be found in the skfn; t~ey are premature ageing and intolerable itching. These effects are not negligible. and· · ·-·· cause much misery, possibly to some extent through lack of sleep. It seems probable that skin symptoms are often confused with leprosy arid other skin diseases. Fortunately the effects of the disease on the eyes do not seem to be as severe in Uganda as in some parts of West Africa but they are by no means negligible and must not be ignored. Figures on eye involvement iri West Nile have been given in Section 4.2 above. During the visit· to Mount Elgon 20 people from the small village of Bukiborogoto (with a population of 292) were found to have greatly impaired vision; they were certainly suffering from onchocerciasis and this is by far the most likely cause of the impaired vision, although in the absence of ophthalmological examination this remains slightly in doubt.

The other effects of the disease which cause severe disability such as elephantiasis and "hanging groin" are quite common, though the writers have no idea of the numbers of persons who may be 'suffering from these gross changes; dwarfism was seen in onchocerciasis foci, but whether "Nakalanga" is related to Onchocerca volvnlus is still very much in doubt.

In general those suffering from onchocerciasis "get old before their time". AFR /<>ncho/8 WHO/Oncho/30 .. 65 page 20

In some places the nuisance caused by the bites of Simulium {generally known throughout Uganda as the'Mbwa fly')is a greater cause of complaint than the disease itself, for the flies can be a very intense biting pest making life miserable in the worst areas.

Interference with the economic development of Uganda by onchocerciasis is particularly striking; in fac.t almost all the control campaigns undertaken by the VCD have been started for economic rather than social reasons. The hydro-electric development project at Jinja made it necessary to control the Simulium nuisance on the Victoria Nile, and the work of the sawmills and forestry school at Budongo Forest was hampered by onchocerciasis. Tourism and hydro-electric development were being threatened on the Uurchison Nile, and still are, by the serious possibility that Simulium although at present quiescent may take seriously to man-biting with consequent transmission of onchocerciasis. The prison farm project by the Ruimi River in Toro District was impracticable until the Simulium nuisance had been brought under control.

These specific examples underline the economic effects of the disease, but its less direct results are probably as great. The major foci in Mount Elgon and \

These conclusions are supported by the observations of McCrae in Kigezi. He found that only 21 per cent. of the labo4r of local origin employed at the tea estate were infected with onchocerciasis, whereas 73 per cent. of a comparable group who were not employed were infected. fvJcCrae concludes that onchocerciasis is an important factor in reducing the amount of labour fit to undertake such employment. Tea is the only cash crop of Kigezi District and the development of the tea industry of growins importance in the economy of the area. AFR /Oncho/8 WHO/Oncho/3().65 page 21

In many countries forecasts of improved production following disease control are rather vague and do not impress the economists. In Uganda successful_ controL.has already been achieved in two areas, Jinja and Budongo Forest, and in both existing industries have developed and immigrants from other parts of Uganda are now farming areas that were previously uninhabitable.

During this short visit it was not possible to gain an accurate idea of the attitude to onchocerciasis in Uganda but the impression was gained that the problem is underestimated. S<~me think that it is only a prt"Jblem on the bN'Clers with the Congo, that not much can be done without international aid and co-operation and that this may be difficult to obtain. This underestima·~c of the extent of the disease may result from the low figures appearing in the annual medical reports or it may be due to the great success against the vector obtained at Jinja (the impression being that by far the greater part of-the problem has been solved).

If this impression is correct it may be difficult to get support for large-scale control until the disease is recognized as an important brake on the development of the country as a whole.

At the periphery of the country, within the foci themselves, awareness of the problem is uneven. Host riistric't medical officers recognize the importance of the disease, but, with few exceptions, most clinicians do not consider it a serious medical problem in their hospitals. People living in the foci. are aware of the considerable nuisance caused by the disease or by the fly or both. Where treatment is available, for instance in the area of the African Inland Missions in West Nile District, awareness is much more obvious. Measures to control the disease would be answering a "felt need" and that, provided tactful explanation of objects and methods was given, full local co-operation would be assured. AFR ./Oncho/8 WHO/Oncho/30.65 page 22

6. DISCUSSION OF SPECIAL PROBLEMS IN UGANDA

6.1 The border problem

In eastern Uganda the Mount Elgon focus just extends at its southern end into Kenya and on the western side of Uganda the \Jest Nile focus~ the Ruwenzori focus and the Kigezi Highlands focus each abut• closely to the frontier with the Congo.

The writers know of no survey work in the border areas of the Congo~ but Dr Williams stated that onchocerciasis is seen among Congolese patients attending an African Inland Mission station in the Congo not far from the West Nile boundary.

S. damnosum breeds in at least three rivers which make the frontier with the Congo~ the Nyarwodo near Goli in West Nile, the Lubilia at the southern end of Ruwenzori and the Ishasha in Kigezi. The fly may be non-anthropophilic in West Nile District but is certainly man-biting on the Lubilia and Isbasha. Foci of S. neavei may occur on the Congo side of the border as extensions of the foci in Uganda. From knowledge already obtained on the Uganda side and from known vector requirements it must be assumed that onchocerciasis occurs in the Congo near the southern end of Ruwenzori and across the border from Kigezi: Dr Williams' observations leave no doubt that at least a small pocket of infection exists in the Congo near \'Jest Nile District.

Under present circumstances there appears to be little hope of obtaining international co-operation for survey work on both sides of the Congo frontier. However in West Nile the boundary runs mainly along the Congo-Nile watershed and probably it will be possible to obtain satisfactory control by working only on the Uganda side. In Ruwenzori control on the Lubilia River might prove difficult. The situation in Kigezi requires further definition.

No difficulty is anticipated in arranging co-ordinated survey and control with Kenya in the Mount Elgon focus.

6.2 Non-anthropophily of vectors

In Uganda foci exist both of anthropophilic and non-anthropophilic S. damnosum with the result that this vector species occurs in several places where onchocerciasis is apparently absent. Non-anthropophily is usually not absolute, a very few flies occasionally biting man but in minute numbers compared with the astronomical number of larvae and pupae in the river (as at Kikagati in Ankole District). AFR /Oncho/8 WHO/Oncho/30.65 page 23

Foci of non-anthropophHic S !._j.amnosum have to be considered.. in Uganda, even though there is no onchocerciasis around them becattse they can provide potential sources of

reinfestation of controlled areas ~~d bec~USd there is no certainty that the flies will always be non-anthropophilic. The factors governing non-anthropophily are not under- stood, and 'it. is possible that introduction of a large human population into an area of non-anthropophilic ~damnosum might induce the flies to start biting man (with the consequent risk of disease transmission); a normally non-anthropophilic population of flies might also become man-biting in a changed environment, for instance if it became established in a controlled area from which the normally anthropophilic "race" had been eradicated.

The significance of anthropophily and non-anthropophily is underlined by the puzzling situation in the Murchison Nile area. Here heavy breeding of S • damnosum occurs along fifty miles of river, but flies will not bite man near the Nile itself; on the other hand flies which seem to originate in the Nile or in lower parts of tributaries very near the Nile will bite man voraciously at Koich, about 30 miles from the main river. Tnls anomaly is being investigated by the VCD at present because onchocerciasis is being transmitted at Koich and a new tourist hotel is being built at Chobi on the north bank of the Nile right besideS. damnosum breeding places. A change in the feeding habits of the fly in the Chobi Lodge area might menace tourism here, ~lthough the fact that a large labour force introduced into the Murchison Nile area for the building of the Karuma Falls bridge was not bitten gives good reason to hope that S. damnosum may not rP-adily change its ways •

The main areas where S. damnosum occurs but is non-anthropophilic are on the Kagera River (boundary with Tanganyika) near Kikagati, along the Murchison Nile itself, on certain rivers floldng northwards from nuwenzori, on the Waki River near Budongo Forest, on the ~fuzizi and Kafu rivers, and perhaps in West Nile District.

It is possible that non-anthropophilic races of S. neavei exist but it is much more difficult to be certain about this species than s. damnosum. Even in areas where S. neavei must be responsible for onchocerciasis transmission it is often very difficult to find adult flies, which appear to assemble for biting only at a few spots not obviously related to the br~~ding sites and perhaps to bite only at limited times of day such as the very early morning. The unmasking of non-anthropophi ly in S. neavei is therefore difficult, but it seems possible that this species is not a man-biter in the Ruwenzori area. AFR./Oncho/8 WHO/Oncho/}0.65 page 24

6.3 Place of drug treatment

The methods available for the control of the vectors of onchocerciasis are so superior to the drugs available for the treatment of the disease that the latter can play little part in large scale control. Nevertheless the subject of drug treatment requires consideration for two reasons: firstly~ even after vector control the parasite will remain in the infected patient and cause symptoms for many years~ and secondly patients suffering from the disease will more and more demand some form of relief.

A great difference was found in the amount of treatment being given in the different foci. In most foci the existence of the disease was recognized~ but it was considered that there was little point in giving treatment before transmission could be interrupted~ especially as treatment with the carbamazines is unpleasant and relatively ineffective. In two places~ Hoima (where patients from Budongo Forest come for treatment) and West Nile District~ considerable interest is shown in treatment. In the latter area Dr Williams is convinced that treatment even in the presence of continued reinfection is worth while~ particularly when the eyes are affected~ and there is no doubt that provision of treatment in West Nile has much increased awareness of the disease in the area.

Until better drugs are available there seems no point in emphasizing the need for providing treatment everywhere~ but priority should be given to people living in areas that have been cleared of the vector so that the maximum number can benefit from the success of control measures.

6.4 Eradication by attrition

In recent years a new approach to the control of S. neavei has been considered by the VCD. This approach has evolved from the successful control project in the Budongo Forest (Prentice, in press).

The object of the Budongo project was to obtain control of disease transmission by dosing th~ main streams where breeding occurred. Some small streams where a little breeding was taking place was left undosed. It was realized that dosing might have to AFR /Oncho/8 WHO/Oncho/30.65 page 25

be continued indefinitely but it was thought that: .the number .. of flies remaining would be so small.that disease transmission could not take_ pla9e. ,The.results were unexpectedly ' 'I . ~ good; _after 24 months no flies could be found at all. It seemed that S. neavei could not maintain itself if most of its breeding places were under attack.

Whether eradication has occurred in Budongo Forest focus can be confirmed by stopping the dosing of the streams and watching to see whether any reinfestation occurs; this will probably be done after a possible source of reinfestation in

"Bugoma ~crest has been controlled. If it is confirmed that eradication has been achieved_, this opens a nettt approach to the control of S. neavei_, which may be termed control or eradication "by attrition".

By this method it would be possible to tackle large foci gradually_, the worst affected rivers being dealt with first and the smaller and less accessible tributaries being omitted. When assessment showed that no more breeding was occurring in the originally dosed system_, the dosing could be extended to other river systems until the whole focus was being covered. The attrition method could have several advantages over the more orthodox eradication scheme which is usually based on mass attack over the whole focus with simultaneous dosing of all infested rivers and streams (aiming at eradication in a few weeks): it would be much more economical in staff and could be

carried out by a smaller unit relying on its o~m resources. Absolutely complete coverage o,f streams might not be necessary_, the small missed tributary that could wreck an eradication scheme by short sharp mass onslaught being unimportant. Attri t;J.on _is not an "all-or-none" scheme. During the period of control short of eradication, people living in the river systems being dosed would be relieved of the greater _part of the fly'nuisance and transmission of the disease would be reduced or possibly interrupted altogether.

It is felt that the attrition approach shows promise and ~ight be appropria~e.in some of the Uganda foci. If it is shown that eradication has in fact been achieved in Budongo Forest_, though not originally envisaged_, by long-continued control on parts only of the originally-infested stream system, the method should certainly be tried out elsewhere; what would be needed is a research experiment to confirm the validity of the attrition method as a means of eradication. At the moment we cannot be sure that it works. AFR /Oncho/8 WHO/Oncho/30.65 page 26

Attrition is only a feasible approach for the eradication of S. neavei which appears to have a short flight range and to stick very largely to its "home" stream or valley system without much crossing of watersheds; it would be inappropriate against S. damnosum because of the long flight range and power of dispersal of this species.

6.5 Do-it-yourself dosing

In large scale disease control schemes that make big demands on limited resources~ the possibility of using voluntary labour is often considered. Possible fields for such assistance must be regarded critically. The task to be done may be simple or complicated; the assistance available may or may not be trained for the type of work required.

In the successful Budongo Forest control scheme several bodies have been responsible for the six-weekly dosing~ including the Forestry Department and the S_·hool of Forestry~ working under the direction of the mill engineer of Buchanans Sawmills~ and the District Health Inspector working independently. At Ruimi Prison Farm a warder has been made responsible for dosing. Both projects are under the general supervision of the VCD.

This delegation of duties has made control possible beyond the present resources of the division.

The results of the control scheme in the Nyamagasani valley using local health staff are equivocal as the project had to be terminated for other reasons·before the effectiveness of such staff could be gauged.

It has been suggested that such delegation of control duties could be further extended and that local communities could be made responsible for their own control schemes. The writers cannot support this suggestion. Control to be successfUl demands accurate dosing and precise timing outside the experience of such local organizations. AFR /Oncho/8 · WHO/Oncho/30.65 page 27

There may be scope for voluntary labour in a well planned control scheme but selection.of suitable tasks requires careful consideration. It might well be that the expensive and tedious task of cu~:ting paths along streams during surveys or access tracks for dosing during control could be undertaken by voluntary community labour and would give the community the benefits of control before it might otherwise be economically possible. Cn the whole~ however 1 pessimism rather than optimism seems advisable in considering the possibility of using voluntary labour in th~ control of onchocerciasis.

1. CONCLUSIONS AND RECOMMENDATIONS

7.1 Conclusions and recommendations

From this review of onchocerciasis in Uganda and personal visits to all the main foci~ the following conclusions have been reached which bear on the control of the disease.(the writers consider these recommendations to be embodied in and implicit in the conclusions given and it is not necessary to stipulate any recommendations separately):

7.1.1 Main conclusions

(1) That onchocerciasis is a serious hazard to health in Uganda and should be controlled as far as possible. It affects many thousands of people and is a serious cause of blindness. There is good evidence that it is acting as a brake on economic development in several parts of the country.

(2) . That a satisfactory technical method of interrupting transmission by controlling the two vectors (Simulium damnosum and Simulium neavei) exists. Provided that the vector breed!~ sites are properly dosed DDT as a larvicide will eliminate breeding.

An equally e~ily 'applied method does not exist for controlling other important communicable diseases such as schistosomiasis. However measures must either result in eradication or lo~-continued control~ otherwise they will have no effect on onchocerciasis which is a long-lasting disease. AFR /Oncho/8 WHO/Oncho/30.65 page 28

(3) That control must be paid for. Although the technical method is relatively cheap it cannot be expected that large foci can be dealt with by the VCD on its present resources. The experience of the division suggests that a figure between 10/- and£ 2 per square mile per year may be taken as the probable cost of control.

(4) That onchocerciasis exists in Uganda to a large extent in distinct foci. These are often reasonably isolated and can be dealt with one by one. Access to foci does not present a problem because of the good communications system to all parts of Uganda where the disease occurs.

(5) That there are eight main foci of the disease which differ in size, vector species, terrain and degree of isolation. Each focus therefore presents a different control problem.

(6) That considerable progress has already been made in controlling the disease and its vectors in Uganda by the VCD. The division is controlling or can be expected to control with existing resources five of the eight-main foci: Jinja, Budongo Forest, Bugoma Forest, Murchison Nile and Ruwenzori. The first two of these are at present being controlled and the prospects are good for control on Ruwenzori and in Bugoma Forest once the outstation at Fort Portal is opened.

(7) That there are three major foci in the country, Mount Elgon, West Nile and Kigezi Highlands, and that there is no prospect of valuable onchocerciasis control in these

~1 with the present constitution of the VCD.

(8) That the VCD is not a perfect instrument for control in these three major foci because of its raison d'etre. It w~s set up to deal with outbreaks of vector-borne disease, and has therefore to cope with emergencies; its fire-brigade nature makes it essential for it to deal with emergencies as promptly as possible, and therefore it cannot carry out uninterruptedly the carefully programmed survey and control measures necessary in the three large foci.

(9) That an organization specifically intended for the control of onchocerciasis in these foci is required. Such a new organization must be devoted full-time to onchocerciasis control and must carry out all necessary pre-control surveys, control measures and immediate post-control assessment; it must formulate its own control plan AF.R /Oncho/8 WHO/Oncho/30.65 p~~

{e.g. whether eradication is aimed at or long-term control and whether river systems are to be dealt with separately) and be responsible for finding solutions to all technical and logistic problems that may arise. It should work to a carefully prepared plan of operations and be a sufficiently stable organization to attract and retain reliable staff.

{10) That the setting up of a new onchocerciasis control organization could be a subject for international assistance {the i~ea implicit in the original request of the Uganda Government to WHO). The formation of an onchocerciasis control unit either as a part of the VCD or independently could be assisted by an international team. The international team should include an epidemiologist, and entomologist and two sanitarians. Members of the international team should have experience of planning and operating large scale field control projects; their function would be to give assistance to the national onchocerciasis control unit in its early stages. National counterparts to members of the international team should be available and the present senior entomologist could become director of the new unit as well as remaining in charge of the residual VCD. In addition there is scope for short-term consultants to assist in solutions.of carefully defined specific problems.

{11) That some of the onchocerciasis foci extend into neighbouring countries and con~rol will require a joint effort. Agreement ·on co-ordinated survey and control operations will be required between the countries conce~ed. International organizations cannot do more than promote and support such agreements.

{12) That control operations in any focus will be locally acceptable and welcome.

7.1.2 Additional technical conclusions

{1) That larvici_ding is the only practicable method of vector control. Despite the misgivings that have been expressed about the use of DDT it is still the most suitable insecticide for use in Uganda at_ the moment. Miscible liquid formulations are more satisfactory than technical DDT carried in fuel oils.

(2) That in most foci aerial application of larvicide is not feasible. It could however prove very satisfactory for control in the Murchison Nile focus. AFR /Oncho/8 WHO/Oncho/30.65 page .30

(3) That seasonal variation in river and stream flow is usually not extreme and in most foci will.not preclude initiation and continuance of control operations at any time of year.

7.1.3 Conclusions on priorities

(1) That the first priority is the setting up of an onchocerciasis control team, of the kind envisaged in 7.1.1, to deal with the three main foci.

(2) That the team once set up should deal with the foci in the following order of priority:

First: Mount Elgon focus Second: WestNile focus Third: Kigezi Highlands focus

The reasons for this order of priority are given below.

The Mount Elgon focus is placed first because:

(a) It is the most isolated focus in Uganda.

(b) The border problem is less severe than in the other foci.

(c) Only Simulium neavei is involved as a vector.

(d) Elimination of S. neavei from Mount Elgon would leave no focus of this vector east of the Nile, the natural divide of the country.

(e) Success here will consolidate the eradication already achieved in Kenya.

(f) It is advantageous for a new unit to start its operations in a place particularly easily accessible from the capital.

It is considered that West Nile should be dealt with before Kigezi Highlands because: (a) The.foctis is larger and has more severe disease.

(b) There is more local awareness and demand for action.

(c) Extensions of the focus into the Congo are probably on a narrower front than in Kigezi. AFft ;oncho/8 WHO/Oncho/30.65 page 31

Note: It is worth noting here that economic considerations seem to be the same in the three foci; no single focus clearly demanding action first on economic grounds. Also that in placing MountElgon first it is fully recognized that access to rivers and streams is likely to be more arduous here than in other foci~ especially as there will be far more watercourses to be dosed here than elsewhere.

7.2 Phasing of control and its integration into a communicable disease service

The planning of control measures and the pre- and post-control survey and assess­ ment must be the responsibility of the new onchocerciasis control unit, but it is thought useful to give some thoughts on how it might function. It is felt that at least one year would be needed for pre-control survey of the disease and the vector in each focus. A control scheme in each focus will involve three stages: firstly, pre-control survey; secondly, control measures against the vector; thirdly, assessment of results. The international team working in concert with the national counterpart should be sufficiently large to allow these stages to be phased so that after the first year work can be carried on simultaneously in more than one focus. For example a programme on the following lines can be envisaged.

Year 1 Year 2 Year 3 Year 4

Mount ElgQn pre- West Nile pre­ Kigezi pre­ Kigezi control survey control survey control survey control measures Mount Elgon West Nile West Nile control measures control measures assessment Mount Elgcn Mount Elgon assessment assessment

The foregoing plan is given merely to indicate the way in which it might be possible to dovetail work in the different foci; it must not be taken as a hard and fast plan of campaign. Whether such a scheme could be operated at all would depend very much upon the control policy of the new unit in any area (for instance whether short-term mass eradication or long-continued repetitive control was decided upon), and whether, for instance, one year was a long enough period in which to obtain all the pre-control information required. AFR /Oncho/8 WHO/Oncho/30.65 page 32

The terms of reference in undertaking this consultantship dealt only with the problem of onchocerciasis in Uganda and no inquiries have been made into programmes aimed at the control of other communicable diseases. It is obvious~ however~ that the control of onchocerciasis - wh~ther phased in the manner outlined above or not - must not conflict with the general pattern of communicable disease control in Uganda as a whole and it has been thought worth while to consider how far the writers' proposals can be fitted into a general plan for "Communicable disease services on a 1 country basis" •

It is clear that the V'.;D cf the Uganda MinistJ.~:; ·Jf Hc.::J.th would form the basis .

of any proposed "Epidemiological Unit" with the functions defined in paragraphs 3~ 4 and 5 of the above-cited paper. The onchocerciasis unit would be one of the "Specific disease control services" mentioned in paragraph 6.

It seems therefore that there is ne conflict between the writers' proposals and the broader picture of general communicable disease control. Discussion of the order of priority in which specific diseases should be attacked is far outside the scope of this report. but it seems that the case for an early attack on onchocerciasis is a strong one for the following reasonz:

(a) it is a well-defined problem;

(b) an effective and cheap method of control is available;

{c) it can be dealt with in stages (focus by focus);

(d) considerable control "know-how'' is already available in Uganda;

(e) staff who have been trained in the field control of onchocerciasis will be available and can eventually be used for the control of other insect-borne· diseases.

1 WHO Regional Office for Africa, document issued 26 September.1963. AFR/Oncho/8 WHO/Oncho/30.65 page 33

7. CONCLUSIONS ET lmCCM-1ANDATIONS

7.1 Conclusions .et recommandations

Apres avoir etudie la situation de l'onchocercose en Ouganda et avoir personnelle­ ment visite tous les principaux foyers d'endemicite, les auteurs sont parvenus, en ce qui con9erne la lutte contre. cette maladie, aux conclusions indiquees ci-a~es : (Ils ne jugent pas necessaire de formuler separement des recomma.ndations a ce sujet, celles-ci se degageant implicitement des conclusions.)

7.1.1 Principal~~-conclusi~

1) En Ouga.nda, 1' onchocercose est une cause importante de morbidi te qu' il faut datiS toute la mesure du possible s'efforcer d'eliminer~ Elle fait ·des milliersde victimes et p~ovoque souvent la cecite. Il y a tout lieu de penser qu'elle r8.1entit le develop- . '. pernent economique de plusieurs regions du pays.

2) On dispose d'une methode technique efficace pour interrom~e la transmission en luttant contre les deux vecteurs (Simuliuni· damnosum et s. neavei). A condition que tous les gttes de vecteurs scient traites correctement, le DDT employe comme larvicide permet de stopper la ~bliferation des simulies. Il n' existe pas de methode aussi facile a appliquer pour combattre d'autres maladies transmissibles importantes, la schistosomiase, par exemple. Il faudra cependant que lea mesures ~ises p~ssent assurer l'eradication complete ou une inteiTUPtion prolongee de la transmission, faute de quoi ~lles seraient inoperantes contre,.,l' onchocercose etant donne le caractere per­ sistant de cette maladie.

3) Des credits seront necessaires pour appliquer ces mesures. Bien que la methode technique soit relativement peu coOteuse, on ne peut srattendre que la Division de la

Lutte cont:re. lea Vecteurs parvienne a elirr!~er le~ foyers importants avec lea seules ressources dont elle dispose actuellement. L' experience acqui,se par la Division pennet de penser que lea mesures de lutte coOteront ~obablement de 10/- a £2 par mille carre {US $0,54-2,16 par metre carre) et par an.

4) En Ouga.nda, 1' epidemiologie de 1' onchocercose se caracterise danS une gra.nde me­ sure par l'existence de foyers distincts. Ceux-ci sont souvent sUtfisanment isoles pour ., . . ' \ .. '·~ AFR/Oncb.o/8 , .-. WHO/Oncho/30.65. page 34 qu'il soit possible de les traiter successivement. L'acces aux foyers ne presente pas de difficulte, un bon reseau de communication menant a toutes les regions ou se ren­ contre la maladie.

5) Il existe huit grands foyers d'endemicite, qui different par la superficie, la topographie, le degre d'isolement et les especes vectrices qui s'y rencontrent. Il faudra done appliquer dans chacun d1 entre eux des mesures de lutte differentes.

6) La Division de la Lutte contre les Vecteurs a deja accompli des progres conside­ rables dans la lutte contre l'onchocercose et les vecteurs de cette maladie. Avec les ressources dont elle dispose actuellement, elle est parvenue, ou peut parvenir, a interrompre la transmission dans cinq des huit grands foyers : Jinja, For~t de Budongo,

For~t de Bugoma, _Chutes de Murchison et Ruwenzori. La transmission est en passe d'~tre interrompue dans les deux premiers et il y a tout., ·. lieu d'esperer qu'elle. pourra l'~tre egalement dans le Ruwenzori et la For~t de Bugoma lorsque le poste de Fort Portal aura ete ouvert.

7) Dans les trois pnncipaux foyers du pays - Mont Elgon, Nil accidental ~t Ma~sif du Kigezi - il est exclu que, sous sa forme actuelle, la Division de la Lutte contre les Vecteurs puisse combattre efficacement l'onchocercose.

8) La Division n'est pas parfaitement adaptee a la lutte contre l'onchocercose dans CeS trois fGyers, n'ayant pas ete creee pour mener des operations de ce genre mais potlr combattre des poussees de maladies transmises par les vecteurs. Etant co~ue pour parer le plus rapidement possible a des situations d'urgence, elle n'est pas en mesure de mener de fa«;on con~inue les enqu~tes et les mesures de lutte soigneuse:nent planifiees qui seraient necessaires dans les trois grands foyers.

9) Il est indispensable de c~eer une organisation specialement con9ue pour lutter contre l'onchocercose dans les ~oyers en question. Cette organisation devra se consa­ crer entierement a cette tiche et mettre en oeuvre toutes les mesures necessaires : enqu~tes prealables, operations de lutte et evaluation immediate des resultats obtenus. Elle devra etablir son propre plar. de lutte (par exemple : decider s 1 il faut chercher a eradiquer la maladie ou a interrcmpre durablement la transmission et si les bassins Ai•1Vvncnot o WHO/Oncho/30.65 page 35 fluviaux doivent faire l'objet de mesures distinctes). Elle devra, d'autre part, re­ soudre e11~.-m~e tous les problemes techniques et logistiques qui pourront se poser. : . . . . . ~ . 11 faudra qu',~lle suive; un plan d' operations soigneusement etabli et qu' elle soit sutfi­ samment stable pour 3tre a m3me de recruter et de conserver du personnel competent.

10} La. creation d'une nouvelle organisation pour·la lutte contre l'onchocercose pourr,ait faire 1' objet d' une assistance inter~ationale ( cette idee etait implieite dans la demande que le Gouvernement de l'Oug~ avait initialement presentee a l'or-13). La formation d'un service de lutte contre l'onchocercose, integre ou non a la Division de la Lutte contre les Vecteurs, pourrait se faire avec le concours d'une equipe inte~­ nationale qui devrai~ comprendre un epidemiologiste, un entomologiste et deux techni- ..... ciens sanitaires. Les membres de cette equipe devraient avoir l'experience de l'orga­ nisation et de la mise en oeuvre de vastes projets de lutte sur le terrain; ils seraient charges de pr3ter leur concours au service national de lutte contre 1' oncho- .: . cerco~e dans la periode qui suivra la creation de celui-ci. Pour chaque membre de 1' equipe internationale, il conviendrait de designer un homologue national. Le chef (<~~ \ ... actuel des services d 1 entomologie (Senior Entomologist) pourrait prend~e la direction du nouveau service de lutte tout en continuant s'occuper des activites reduites a . . .• qui demeureraient assurees par la Division de la Lutte contre les Vecteurs. En outre~ • 1 /,. ·• il y aurait inter3t a faire appel a des consultants a court terme pour aider a resoudre certains problemes particuliers soigneusement definis. 11) Comme certains foyers d'endemicite debordent sur le territoire de PaYs voisiris, il sera necessaire d' envisager une _action commune. Les pays interesses deyront sJ en­ tendre pour mener de concert les enqu3tes et mesures de lutte necessaires. Les organi-· sations internationales pourront seulement promouvoir et soutenir de telles ententes.

12) Dans tous les foyers, les operations de lutte seront acceptees et m3me favora- blement accU:ei·llies par la population~

7.1.2 Conclusions techniques supplementaires

1) La destruction des larves est la seule methode applicable pour lutter contre les vecteurs. En depit des apprehensions qui ont ete exprimees touchant l'emploi du DDr, ·•··. \. AFR/Oncho/8 WHO/Oncho/30.65 page 36

c'est encore ce produit qui convient le mieux a la situation existant actuellement en 0Uganda. Les preparations liquides miscibles sont preferables au DDT technique en suspension dans le mazout.

2) Dans la plupart des foyers, il n'est pas possible d'envisager la dispersion de larvicides par aeronefs. Cette methode pourrait toutefois donner d'excellents resul­ tato dans le foyer des Chutes Murchison.

3) Les variations saisonnieres du debit des cours d'eau ne sont generalement pas tres accentuees. Dans la plupart des foyers, il sera done possible d'entreprendre et de poursuivre les operations de lutte a n'importe quel moment de l'annee.

7.1.3 Conclusions_!elatives aux prior}tes

1) .. La priorite absolue doit ~tre donnee a la creation d' une equipe de lutte contre l'onchocercose (voir 7.1.1) qui sera chargee d'eliminer les trois principaux foyers.

2) Une fois creee, cette equipe devra s'attaquer aux foyers dans l'ordre suivant : Premierement Mont Elgon Deuxiemement Nil occidental Troisiemement : Massif du Kigezi

Les raisons pour lesquelles cet ordre a ete choisi sont les suivantes

Le Mcnt Elgon vient en premier parce que

a) c'est le foyer le plus isole qui existe en Ouganda,

b) le probleme frontalier y est moins aigu que dans les autres foyers,

c) on n'y rencontre qu'un seul vecteur (Simulium neavei), d) une fois S. neavei elimine, il ne restera plus aucun foyer de ce vecteur a l'est du Nil, lequel constitue une barriere naturelle a l'interieur du pays,

e) les succes remportes dans ce foyer consolideront l'~radication deja realisee au Kenya,

f) 11 est preferable qu'un service qui vient d'~tre cree fasse ses debuts dans un endroit facilement accessible a partir de la capitale. AFR/O~cho/8 WHO/Oncho/30. 65 page 37

Le foyer du Nil accidental devrait passer avant celui du Massif du Kigezi parce que a) sa superficie est plus grande et la maladie y est plus grave~ b) la population y est plus consciente du danger que constitue l'onchocercose et insiste davantage pour que des mesures soient prises~ c) les prolongements sur le territoire du Congo sont probablement plus etroits que dans le secteur du Kigezi.

~ : Il convient de remarquer que les imperatifs economiques paraissent identiques pour lea trois foyers et que, dans aucun cas~ ils n'incitent nettement a donner la priorite a l'un ou a l'autre. D'autre part~ en.accordant la priorite au secteur du Mont Elgon~ les auteurs ont pleinement tenu compte du fait que l'acces aux cours d'eau y sera vraisemblablement plus malaise que dans les autres foyers et que, de surcrott, le nombre des cours d'eau a traiter y sera beaucoup plus eleve. AFR/Oncho/8 WHO/Oncho/30•65 page 38

8. ACKNOWLEDGEMENTS

The writers wish to acknowledge the interest shown in their work by the senior officials of the Uganda Ministry of Health who were met in Entebbe, particularly Dr Kadama, Chief Medical Officer and Permanent Secretary; Dr Muganwa, Deputy Chief Medical Officer; and Mr Kabbwa, Chief Health Inspector.

Thanks are due to Mr H. A. Prentice, Senior Entomologist, and Mr A. W. R. McCrae, Entomologist, of the Vector Control Division for the assistance given in every aspect of the work and for the excellence of the arrangements made for the tour of the foci. The writers acknowledge the help given by Mr G. Ealden, Field Officer of Vector Control Division, who accompanied them while on safari.

During field survey the writers met regional senior medical officers, district medical officers, district health inspectors .. and medical assistants in charge of dispensaries tci"b:· numerous to name individually but whose helpfulness and courtesy is gratefully acknowledged.

Finally thanks go to Dr Peter Williams of the African Inland Mission for much useful information on West Nile Jistrict, and Mr G. R. Barnley and others of Makerere University College for very helpful discussions. AF'R/Oncho/8 l:JHO/Oncho/30. 65 page 39

REFERE~~CES . : . :. ~. ' The following list of refe:cencos includ.es al:i. th& UJD.in works ~n onchocerciasis and 1 ts Simulium vectors in Uganda which havE; come to ;.;he i.Jri te:rs' P.t.tention. rllost of the late E. G. Gibbins' papers on Uganda Simuliidae h~ve been c:r.ittf)d as they have no relEwanc.e· .to_..onchocerciasis and arc all 'listed in Freemr>.n & d'3 i'4eillon· (1953).

Barnley, G. R. (1949) Onchocerciasis; in K5.gazi Distr~ct, Uganda, ~-=- Af_£:.._1~_c!. ., 26, - ...308.,..310 I .'

Barnley, G. R. (1953) The cont!'ol of S:Li:lulium dam"'lcsui1 .. (''.he-:-~l "11<1) c;.1 t:1e Victoria Nile, Uganda, unpublished mimeographed document\'ffioionchocer<.;~.ar:ds/),.8

Barnley, G. R. (1958) Control of Simulium vc.:c"i;o:r·s c:1 c~~ho~:sre.lc-sis ~n Uganda, Proceedings of the: Xth Inter:1at:i.onal Cong1 e:s~ of E~to;;.1ology, 3 .. 535-5Yf

Bamle:y; G. R. (196la)- G~ographical dis·~ributj.on and inc!dmc~ oi o:.:-tchocerciasis in Uganda: geographical distribution o~ c.nchoce:rcF~.l cy~ L'sio:1s in Ugand:::..: transmission potential of Simu.L~.um vectors of onchccerc.ic.::;::s in U.!and.a, l.U'l,ubl!shed mimeographed w'f10 ·;.·-;:;,~~nt .!'.F'R/Crt!':c)cz:"ciasts (:~.961)/2 ..• ':.. • .i

Bamle:y, G. R. (196lb) Control of S:1.t 1TJliurn vectors o·:: o':lcho-.!::•ci~sis by local repetitive measure::;, Unpublis·h~ni.i.rr.;ograp;ied viHO doc;Jr,:ent AF:'R/0nchocerciasis (1961)/29 . .

Ba:rnley ~ G. R. (1962) Px-actica 1 •r.~ t-hcd,s for the r::ont7>ol of Sim•.!!:!.u~n damnosum (':'heobald) and Simulium ncnvci (Roubaud) t 1·w ·:r-,r~".;.0rs of c:1:.:hoc~r~·a.-:ds in Uganda, Proc-;edings ~ ·:;helntematio:::J.al Con3::~s:; or' :l1':.:c;aob::;6:; .. Vj ~nm=c; ?;.~ -··374-377

Bamle;,•, G.• R. (1963) Observati<'i1S on t:ne de,_:-el<'pment c::: Cac~10.Jel"Cet, volvulus Le.ucY.art ill Simu.liu:n dam."'losum n.eob. and Sl,hllium neave::. Ibub~:-;·-B.i.cc:nc·;:.;:--y:-,;.89~ 70 pp. ·------···---·-~·--·--·--'- ~- .... _._._____ .. _ Bamley:, G. R. &Prentice, M. A. (1958) E.~~CD.V'35. ::.n t.Jc;r.nda, E. Afr. med.

Br·o~m, .A~-- !.f .•. A. (l962) A survey of SimuHum con":.rol ::.n Africc-.. BuJ.l. Hld Hlth Org., 27, ---·- .. _._.._ ...... ______.._ ,_,.- 511-527

Corbet, P. S. (1958) Some effects of DDT on the fatma of tr.c Victoria Nile, Re·1. Zool. Bot. ari'., 57, 73 .. --~ ·- Corhet, P. fi. (1961) Tne biological significar.ce of tb-) o.tt?.c:·..:na·.1t of immature s·i;ages of Simu~ to .. mayflies and crabs, Bu_L!_:_~~~---~~E. ~ ;>_?, !595-699 : ,; ...... - .. ···---·····- ----~·- ··~·· ~·· AFR/Oncho/8 WHO/Oncho/30.65 Page 4o

Fleming, A. M. & Hennessey, R. S. F. (1932) A dermatosis occurring among East African natives , Brit • J • Derm • , 44, 173

Gibbins, E. G. (1934) "Mbwa" flies, Uganda J ., _g, 272-277 Gibbins, E. G. (1939) Simuliidae and onchocerciasis in Uganda, E. Af'r. med. J., 12, 378-384

Gibbins, E. G. & Loewenthal, L. J. A. (1933) Cutaneous onchocerciasis in a Simulium damnosum-infested region of Uganda, Ann. trop. Med. Parasit., gr, 489-496

HYnes, H. B. N. & Williams, T. R. (1962) The effect of DDT on the fauna of' a central African stream, Ann. trop. Med. Parasit., 12, 78-91 Hynes, H. B. N., Williams, T. R. & Kershaw, W. E. (1961) Freshwater crabs and Simulium neavei in East Africa. I. Preliminary observations made on the slopes of Mount Elgon in December 196o and January 1961, Ann. trop. Med. Parasit., ~~ 197-201 McCrae, A. W. R. & Prentice, M. A. (1963) Some recent studies on the biology of Simulium vectors of' onchocerciasis in Uganda, Biochem. J., 89, 78-79

McLaren, D. S. (1961) Geographical distribution and incidence of onchocercal eye lesions and blindness in East Africa, unpublished mimeographed WHO document AFR/Onchocerciasis(l961)/3

Nelson, G. S. (1958a) "Hanging groin" and hernia, complications of onchocerciasis, Trans. roy. Soc. trop. Med. Hyg., 52, 272-275

Nelson, G. S. (1958b) Onchocerciasis in the West Nile District of' Uganda, Trans. roy. Soc. trop. Med. Hyg., 52, 368-376

Nelson, G. S. & Pester, F. R. N. (1962) The identification of infective filarial larvae in Simuliidae, Bull. Wld Hlth Org., 27, 473-481

Prentice, M. A. (1963) Economical local control measures against Simulium neavei, a vector of onchocerciasis, in the Budongo Forest, Uganda. In: Proceedings of the Seventh International Congresses on Tropical Medicine and Malaria, vol. 2, pp. 142-143

Raper, A. B. & Ladkin, R. G. (1950) Endemic dwarfism in Uganda, E. Afr. med. J., gr, 1-21

Speke, J. H. (1863) A Journal of the discovery of the source of the Nile

Wilkinson, P. R. (1949) Some observations on microfilariae in Africans at JinJa, E. Af'r. med. J ., 26, 344-346 AFR/Oneho/8 WHO/Oncho/30.65 page 41

Williams, T. R. (1961) The diet of freshwater crabs associated with Simulium neavei in East Africa. I. Crabs from west and east Uganda collected by the Cambridge East African ~pedition, 1959, Ann. trop. Med. Parasit., 55, 128-131

\villiams, T. R. (1962) The diet of freshwater crabs associated with Simulium ne.avei in East Africa. II. The diet of Potamon berardi from Mount Elgon, Uganda, Ann. trop. Med. Para~it., 56, 362-367 .. \- Williams, T. R. &·Hynes, H. B. N. (1961) Freshwater crabs and Simulium neavei, unpublished mimeographed WHO document AFR/Onchocerciasis(l961)/A-2

Williams, T. R., Hynes, H. B. N•. & Kershaw, W. E. (1964) Freshwater crabs aric(Simulitun neavei in East Africa. II. Further observations made during a second visit to East Africa. in February-April, 1962 (the dry season), Ann. trop. Med. Parasit., 58, 159-167

Woodruff, A. W. et al. (1963) Onchocerciasis and the eye in westem Uganda, Traris. roy. Soc. trop. Med. ayg., 21, 50-63

... 1 ,I AFR/Oncho/8 WHO/Oncho/30.65 page 42

ANNEX 1

ITINERARY -Date Place· Purpose 9 October · ··· · · -- Arrival at Entebbe

10 October Entebbe ) Study or·vcD files ) 11 October· ·Entebbe )

12 October Entebbe Visit to senior officials of Ministry of Health

···Kampala· · Discussions with VCD personnel

13 October .. Kampala ) Dis9u~sions with VCD. Further ) study of files. ·Arrangements for 14 October Kampala ) tour .of .onchocerclasis foci . .

15 October Mbale ) Discussions with SMO Eastern Region ) and DMO Bugisu District. 16 October Mbale ) Study of Mo•.mt Elgon focus. ) Visit to Bukiborogoto (Colbourne) 17 October Mbale ) and Bufumbo Forest (Crosskey) ) 18 October Mbale )

19 October Gulu Visit to SMO Northern Region

20 Oc"tcb'3r Gulu Visit to DMO Acholi District

Arua Visit to DMO West Nile District

21 October Arua ) Study of West Nile focus. ) Discussions with Dr Williams ru1d 22 October Arua ) visits to African Inland Mission ) stations at Kuluva and Goli 23 October Paidha )

24 October Paraa ) Rest week-end ) 25 October Paraa )

26 October Koich ) Visit to VCD safari camp in ) heavy onchocerciasis area of 27 October Koich ) Murchison Nile focus. Study of ) Murchison Nile focus AFR/Oncho/8 WHO/Oncho/30.65 page 43

Annex l

Date Place Purpose

28 October ~sindi Visit to MO, Masindi hospital

29 October Masindi Study of Budongo Forest focus: discussions with· sawmill engineer (responsible for dosing) and Officer i/c Forestry School

30 October Fort Portal En route discussions with DMO Bunyoro District and clinicians at Hoima. Visit to SMO Western Region

31 October Fort Portal Visit to Ruimi prison farm accompanied by DHI Toro. Visit to Kibale forest with vector collection

1 November Kichwamba Inspection and collection on Ruwenzori focus rivers

2 November Kayonza ) Study of Kigezi Highlands focus. ) Visits to Katete dispensary and 3 November Kayonza ) tea-estate dresser

4 November Kisoro Inspection en route of difficult terrain of impenetrable forest where Kigezi control will be needed

5 November Kikagati Visit to Kabale hospital en route (DMO Kigezi not available). Visit to remarkable focus of non­ anthropophilic s. damnosum

S November Kampala Return from safari round onchocerciasis foci

7-13 November at Kampala Preparation of first draft of Joint report. Final discussions with VCD personnel. Visit to Barnley and Wilks at Makerere University College for discussions. Brief visit to Virus Research Institute, Entebbe AFR/Oncho/8 WHO/Oncho/30.65 page 44

Annex 1 Annex 1

Date Place Purpose

13 November Entebbe Preparator,y to departure

14 November Entebbe Final visit to senior officials of Ministry of Health. Departure of Colbourne for Brazzaville and Crosskey for Geneva Affl/Onqho/8 .wao/oncho/30. 65 page 45

ANNEX 2

DETAILED REVIEW OF MAIN ONCHOCERCIASIS FOCI.

'" CON'lENTS ·~··~------~-· ..

; '· :·, '· :·:· P!ge ,-.·4.. 1 1. West Nile Focus . • • • •

2. Jinja Focus • • • • ~ )46

'·\~i. 3· Mount Elgon Focus • • ·' • -···4'9

4. Murchison Nile Focus • '· • • • 53 ... 5. Budongo Forest ·Focus • • • • • • • • • 57

·.:. ... • -· '1 - 6. Bugoma Forest Focl.ls • • • • • • • • 59 . . .. . Ruwenzor~ Focus . 1· . • • • • • .J • . . . • • • 62 "!'' .. , • : ~- . ··''·· ·. • _j .. 8. Kigezi Focus • • • • • .. .. -~ .. .·_i. ~ ..... :_·.~ .- . .. • • 67

;•.. '

(l rf ~ \ ' ·.· .. . - •;; ··- ,, ...

.. ~·~. - ·.~

:I ~· ' • ~ . • ' .•.i

~: ~ ._: , .:?1 .-•. :. ',:;'

'J.' AFR/Oncho/8 WHO/Oncho/30. 65 page 46

Annex 2

1. WEST NILE FOCUS

1.1 Description

Administrative district: West Nile.

Area 2000 $Quare miles.

Population at risk 2?0 000.

Tribal gr9ups Alur and Lugbara.

Main Cr?PS Cassava1 tobacco~ cot~on.

Populatio~ ~vement : Emigration to ot.her. distr~cts, Buny9ro ,. etc.

Vegetation Mainly open savannah~ well-wooded yalleys~ stream sides choked with exceptionally long dense elephant grass, open

grassland above 5000 f~~t near Congo border just outside

focus~ no rain forest.

Relief and drainage : Hilly or undulating country with open vistas~ not

mountainous~ drained by streams and rivers originating in west near Congo border and flowing eastward 1n several parallel systems to Albert Nile; in south-west Nyarwodo system rising in Congo and entering area near Goli.

Altitude : 3000-4800 feet, to just over 5000 feet near Congo border just outside focus.

Roads System good, but following watersheds between valleys and along Congo border; main Arua road crossing lower parts of main river systems; little or no access to upper part of streams.

Isolation Good within Uganda 1 nearest Budongo Forest~ possibly extending into Congo. AFR/Oncho/8 WHO/Oncho/30.65 page 47

Annex 2

1.2 The disease

The main sources of information are the observations of Nelson (1958a and b), of Dr Peter Williams and of members of the VCD who have visited the area.

Nelson, who was District Medical Officer (DMO) Arua from 1950 to 1955, made a special study of four-villages in the'Nyara valley with a total population of 1275. He found very different rates of skin infection in the four villages, in the worst· every individual over six years old was infected. In the four villages together 728 were examined and 408 were positive. He gives details of infectioJ)_by age-groups and illustrates how differences in examination technique can affect the results.

He found 12 blind people in the valley, but considered onchocerciasis the cause in only two. Of 169 whose eyes were specially examined, he found changes due to onchocerciasis in eight. He also observed cases of hanging groin.

Williams has been working at the Mission hospital at Kuluva for more than 15 years, he visits other mission hospi ta.ls in the district and has made a special study of the eye signs of onchocerciasis. He considers that the disease is found in the Anyaw river system north of Arua, both above and below the escarpment and in the Ora ri\•er system above and below the escarpment. The streams south of the Ora system are also sources of infection. He (as well as Nelson) has noted that the severity of the disease is patchy within the affected area. Two particularly bad areas are Madi and Erusei Hill. His clinical approach precludes an accurate esti~a.te of disease incidence, but he has no trouble in finding 100 positive skin snips in a day and he was able to collect 1000 from 10 localities for ophthalmological study.

Of this 1000, 25 per cent. had microfilariae in the anterior ch~er and 2.6 per cent. were economically blind. One hundred and fifty-five were ung~r 16 years of age, 334, 16 to 30, and 511 were over 30. Eye signs were present in 32 per cent. of the youngest group and 76 per cent. of the oldest (one infant nine months old had_a positive skin snip). In another survey in the Madi area, 29 per cent. of those with positive skin snips had a visual acuity of less than 6/24. AFR/Oncho/8 WHO/Oncho/30.65 page 48

Armex 2

Williams is convinced that treatment of those with eye signs is well worth while and he finds that 80 per cent. complete a course of treatment. He has also seen the later complications of the disease, such as elephe.ntitis in the scrotum.

The government hospital at Arua and dispensaries at Koboko Paidah and Goli were visited.

At the hospital about one case of onchocerciasis is diagnosed each month. At Koboko, it is not seen, though the dispenser knew the disease and had heard of it occurring at Yembe. At Paidah the disease is not seen but at the mission dispensary at nearby Goli (about five miles away), about one or two new cases were seen each week, coming from the Narntini, Nyarwodo and Angole River valleys. The dispenser considered that }:oca.tients preferred Goli Paidah because accurate microscopic diagnosis was available at· the fonner. It may be due to the regular treatment given at Goli under the supervisio~ of Dr Peter Williarns.

The conclusion reached is that the disease is a serious health problem in the south part of the district and that it occurs north of Arua and possibly in other localities near the Albert Nile. Its distribution is very patchy so that no estimate of the nUmber affected is possible, but it must number many thousands.

There is consider~ble local awareness of the disease, particularly skin cQanges and hanging groin, also of eye effects and the benefits of treatment. Questions have been asked about i~ in parliament.

The principle parasitological requirements appear to be surveys to define the areas where transmission is occurring and identification of the most severely affected villages •

. This work could be done most easily in co-operation with Dr Peter Williarns whose clinical duties do not give him time to prepare his valuable observations for publication. AFR/Oncho/8 WHO/Oncho/30.65 page 49

Annex 2

1.} . -Entomology

The main sources of information are the survey of the VCD in 1954 and the brief notes by Barnley (1961). s. neavei was originally found in West Nile in 1951, and Nelson (1958) recorded this species as vector. Nelson also stated that S. damnosum t-las absent, but later work, including our own observations, shows that this species breeds in several West Nil-a rivers.

VCD surveys showed that s. neavei breeding occurred in most rivers and streams between about 3000 and 4500 feet, attachment being to two crabs, P. ni~~ and

P. ? aloysiibaudii. Adult .s. neav~ have so far proved very hard to·-rlna .. in West Nile, except .. for one freak occasion at a,point on the Nyara river when some 50 flies were incidentally found during a picnic lunch; at one stage in the 1954 survey it was even thought that s. ·neavei could not be the vector and various othe~ biting flies wex:_e __ dissected in a search for developing 0. Yolvulus. Even now it is not certain beyond all doubt that S. neavei is the only vector, especially as S. damno~ is now known from many scattered places in the area. The VCD personnel consider that S. neavei probably move up· and down stream in West Ni~.e, but that there is little movement across watersheds separating stream systems; this needs v~rifying. Because of the extreme difficulty of finding adult flies biting in West Nile, it is thought that feeding must occur at a few particular spots, perhaps for only a very short·time

(? early morning); at present it is baffling how so much infection of the hum~ population occurs in the apparent absence of biting. No information is available on thn ~1chocerca infection rate in the flies.

During the writers' stay in West Nile several hours were spent at And ne~ breeding areas of S. neavei and of S. darnnosum and stops were m~e at several likel~. biting places; however, we found no flies. The rivers during our visit were ~n flood and unsatisfactory for crab catching, but searches were made for S. neavei and S. damnosum breeding wherever possible. A heavy infestati~n of s. neavei larvae and pupae was found on a single crab (P. niloticus) collected in the Ora River at cr?ssing of Uleppi-Off'akS: road, &1d. .Dr Williams was particularly glad, to see this ·: . ·' as h~s first experience of seeing S. neavei breeding. Crabs from the Oli and Lobo

:av:;i'~; also were collected and from a tributary of the Nyara but these were un:l.nfc~teo .. AFR/Oncho/8 WHO/Oncho/30.65 page 50

Annex 2

S. damnosum larvae and pupae were collected from the Rivers Nyara, Ora, Ala and Agoi in the general area of Bondo, and from the Nyarwodo River where this forms the Congo frontier at Goli; Mr Bamley states that S. damnosum also is found on the lower part of the Ora near the Albert Nile.

There !s little local awareness of the fly, but the dispenser at the Goli Mission said that people complained of being bitten in parts of the Namtin and Nyarwodo valleys; the dispenser gave a description suggesting Simulium. Dr Williams, with more than 15 years at Kuluva, said that he had never seen any flies which he would take to be Simulium.

The main entornologi cal requirements are a more thoro·..tgh survey to delimit the extent of S. neavei .. breeding, an intense effort to locate the places· and times at which S. neavei bites and its infection rate (to relate if possible to the patchy picture of human infection), a survey of the breeding distribution of s. damnosum end confirmation beyond all doubt that this species is non-anthropophilic in West Nile. The information at present available is very scrappy atld incomplete and the need is for a full-scale survey to be mounted in this area lasting for a minimum of one year; in our view no useful control in this area can be contemplated until such a thorough reconnaissance has been made and adequate pre-control data on adult flies obtained as base-line data with which to compare post-control fly incidence.

1.4 Control

So far the only control in this focus has been the dosing in 1955 of streams in a small part only, the heavily infected Bondo-Lazebu area; this was a pilot control project only largely designed as a guide for control in Budongo Forest focus. The Ala, Agoi, Nyara and Ora Rivers, the Adoka tributary of the Ora and a tributary of Agoi were dosed; there were eight dosing points, three on the Agoi and one each on other watercourses. Each point was dosed once a week for a control period of 12 weeks, using Shell Arcotine SO 18 water-miscible DDT concentrate applied over 30 minutes at 0.5 ppm. S. neavei larvae d~sappeared and were not found on assessment surveys of the treated rivers until 18 months latlr, suggesting a slow rate of ,, reinfestation in this area. '!he only source·of information on this control work is a VCD departmental report. AFR/Oncho/8 WHO/Oncho/30.65 page 51

Annex 2

West Nile is a large,- as yet poorly·· defined';· focus where cross-country access to rivers and streams should not be·' tocf'dif'ficult~ although most roads run on the watershed~-with-few ·stream'crossi~' suff1ciently high up; movement along rivers will be excessively difficuit'because of tall dense cane-grass. Maps of the stream system are accurate, and streams should be easily enough found. Whether the focus -...... ~ extends into the Congo at its southern end is not known and will be difficult to find ·- . ·. . .. . out. The country is open and aircraft could be operated there, but aerial larvi- ciding of such small watercourses might not be practicable; but the possibility might be kept in mtnd during the extensive preliminary survey which will certainly be needed in this focus before a large-scale control campaign can start.

2. JINJA FOCUS

2.1 Description

Administrative districts: Busoga and Buganda. Area· . 1600 square miles.

Population at risk 225 000.

.·. ; -~/~. Tribal groups Baganda ·anaBisoga.

Main crops Banana, sugar, coffee.

Population movement : Considerable influx since control, sug~r estate labour from Kigezi and West Nile.

Vegetation Largely cultivated, elephant grass and forest relip~s.

Relief and drainage Rather flat or undulating open country bisected by Rocky stretch of Victoria Nile below OWen Falls Dam, main river receiving only storm-water erosion gullies, no signifi- cant tributaries.

Altitude 3400-3750 feet.

Roads : System fair_, access to dam (from which dosings made) excellent. AFR/Oncho/8 WHO/Oncho/30.65 page 52

Armex 2

Isolati,on , · Apparently good, but reinfestation occurs from unknown source, nearest known point 85 miles distant in Kenya (Broderick Falls) or 105 miles between lowest point on Jinja stretch and highest on Murchison stretch.

2.2 The disease

The details of onchocerciasis in the Jinja focus before control have been recorded by Barnley (1953).

Surveys showed th~t about 65 per ~ent~ of the inhabitants of the focus were

infected. In some vill~ges the. figure was.· . . as . high. . . ~s 80 per cent. '·' :· ·. A survey of 1400 covering all age-groups showed the following rates:

Age 0-5 20 per cent. Age 6-15 40 per cent. Age over 15 80-100 per cent.

Red inflamed eyes and cloudiness of the cornea were. commonly seen, probably

10 per cent. of those over 30 were blind. In one grou~ of children numbering 70, 28 Nakalanga dwarfs were seen. Simulium damnosum was an intolerable nuisance.

Ten years after control was achieved, some parts of the area were re-surveyed (Barnley & Wilks, personal communication). About one per cent. of positives were found 1n· those under 10 years. No· Nakalanga was found bom since contrQ~:· .,. In one locality it was possible to survey a school which in 1952 had the following rates:

Age 6-10 years 53 per cent. Age 11-15 years 69 per cent.

In 1963~ two of 140 were positive and their age was doubtfully under 10 years.

It seems that a small amount of transmission has occurred, presumably during the months when Simulium became re-establish~ and before re-dosing was carried out.

Infections are still found in the older age-groups though these have been diluted by immigrants who are now prepared'to settle in the area. .: ' AFR/Oncho/8 WHO/Oncho/30.65 page 53

Annex 2

The residual problem is the treatment of. these pld cases,. but there is no easy

way of doing this • .. Apart from suffering from the symptoms.of the d~sease, they can . ~il. . serve as a reservoir of reinfection if the Simulium returns.

2.3 Entomology

The main source of information is Barnley ( 1954, 1958) • A report on all the Mr work done. !: at Jinja from 1949. to 1964. is being. prepared.. by. McCrae.

Th~ vec.tor Simulium damnosum in this focus; 'has been under control since 1952. Deta:f.ls of pre-control. fly··incidence and infect-ion are given by Bamley ( 1954) and It is of interest to.note •. however, that flies had been well known to be a biting menace in the Jinja area for many years before control., and the Victoria Nile area is the type-locality of s. damnosum which was originally described from here in 1903.

Because of successful control, no personal observations were made in the JinJa focus, other than to stop briefly at the Owen Falls Dam and the submerged Ripen Falls (aboye the dam).

Before control there was much local awareness of the fly, both among the inhabitants on either side of the Victoria Nile stretch of the river and among expatriates living in Jinja. Although, since control, the fly is virtually eradi- cated for periods of four or five years at a time, there... i.s still some local awareness of flies when they do reappear and local people draw the attention of the VCD to a reappearance if the continued assessment surVeys of the VCD faii to fiDd them.

The only ento~ological needs in the area are for continued surveillance in case re-dosing should become necessary, and if possible to determine the source of reinfestation of the Victoria Nile (at present much in doubt).

2.4 Control

Eradication of the vector from this focus has been achieved, though reinfestation has occurred on three occasions. success has been achieved by the use of DDT as a larvicide. Low-level aerial spraying aimed at the adult was not successful. Dosing AFR/Oncho/8 WHO/Oncho/30.65 page 54

Armex 2 has been done in 1952, 1956, 1961 and 1964. The last successful dosing in 1964 employed Murphy 25 per cent. DDT in emulsifiable oil fed into the-sluice in the Owen Falls Dam. TWelve applications were made at seven-day intervals to.give a concen­ tration of .036 parts per million of p-p DDT.

Full details of the dosing of the Nile below Jinja have been prepared by McCrae. A report on the early work has been made by Bamley (1954, 1958).

There are no particular difficulties in this focus: all that is ,required is continued surveillance so that reinfestation may be dealt with as .. i. t occurs. This is the policy of the VCD and no difficulty is foreseen in carrying it out •.

The cost of control at Jinja has worked out at about five shillings per square mile per year.

}. MOUNT EWCN FOCUS

:;.1 Description

Administrative districts: Bugisu and Sebei.

Area : 600 square miles.

Population at risk : 120 000.

Tribal groups : Bagisu and Sebei.

Main crops : Banana, coffee, some sugar and tea.

Population movement Very little, no immigrant labour.

Vegetation· Montane forest about 7000 feet in north, down to 5000 feet in centre; in north below 7000 feet acacia savannah, some cultivation; in centre and south below forest, almost all heavily cultivated with banana and coffee.

Relief and drainage Irregular lower slopes of mountain, in south and centre some steep rounded hills, in north irregular sharp cliffs, drained by radial streams running through forest in upper parts and cascading in high falls down cliff sides, then

usually levelling. Altit~de 3500-7000 feet. AFR/Oncho/8 WHO/Oncho/30.65 page 55

Armex 2

Roads ·Fair, penetrating Bulucheke basin and valleys near Mbale, in north two curving parallel roads, one about 4000 feet, the other following 6000-foot contour towards Kenya border.

Isolation Very good, nearest known neavei focus about 200 miles away (unless undiscovered foci exist in Karamoja).

3.2 The disease

The main source of information about the disease is the survey by the VCD in 1955· In foUr· localities in the central part of the focus 328 people were ~xamined. Over 80 per cent. were infected in each locality, but Barnley notes that the samples were probably biased ta-~ards those suffering from the disease.

He recognized 16 patients with swelling of the inguinal glands in this group and four Nakalanga dwarfs.

Since this survey, skin snips have been done at dispensaries in the focus and the presence of the disease confirmed from the Kenya border in the north to the Kenya border in the south, but the proportion infected is not known.

During our consultantship, we visited the small vi·llage of Bukiborogoto (population 292) in company w-ith the DMO Mbale.. Twenty patients were seen with grossly defective vision and obvious signs of oncho.cevQiasis (nodules and onchoderma- titis). This observation is strongly suggestive that on'chocerciasis is a serious cause of eye disease in this. focus. One Nakalanga .. was_ s~e~~

There can be no doubt that onchocerciasis is a serious cause of ill-health in this focus.

The inhabitants are aware of the disease and its association with the. Simulium for which they have a local name. The DMO recogniies the disease as one of the important health problems in the district. On the other hand, few cases are . . recognized in the hospital at Mbale. AF:H/Oncho/8 WHO/Oncho/30.65 page 56

Annex 2

The interest of the DMO and the presence of an ophthalmologist at Mbale suggest the possibility of a small-scale but intensive survey, similar to that carried out at Bugoye, to give an indication of the amount and type of ill-health caused by the disease in this focus.

Additional information about the prevalence of the disease at the extremes of the focus would be valuable.

3.3 Entomology

s. neavei was first found on the Uganda side of Mount Elgon in 1951 when Mr Bamley accompanied by Mr J. P. McMahon from Kenya made . an initial aurvey. Since theri Mount Elgon has been the scene of many further investigations and several sources of information are available. The main ones are: Barnley & Prentice (1958) on breeding, adult incidence, and control; Nelson (1962) on infection of ~ult flies with different filariae; and the papers of the i'Liverpool Gro~p" on ~rabs associated with S. neavei, e.g., Williams (1961), Williams & Hynes (1961), Hynes,. Wtlliams & Kershaw (1961).

Surveys of the VCD and others have shown that s. neavei breeds in all the radial rivers and streams flowing off Elgon, in a crescent-shaped area between about 3500 feet and 6000 feet altitude, which just overlaps the Kenya·border, at least at its southern. end. In places breeding distribution extends higher, to some 7000 feet, but around northern Elgon does not occur higher than the 6000 feet contour. Originally, following McMahon's experience in Kenya,·it was believed that S. neavei occurred only on the crab P. niloticus, but. it was later discovered (after the dosing failure of 1957) that much breeding occurred on another crab species living at altitudes higher than P. niloticus: in the prevailing taxonomic confusion various names have appeared for this second species of crab, but at present the most fashi(?~al:>.~-~. is P. berardi (? = P. granviki) • Despite the wide breeding range repeated·:surveys for adult flies have shown that in manY areas, especially northern Elgon and in the Bulucheke basin, it is practi'cally impossible to find S. neavei as adults, but that two particular pockets exist where flies occur in enormous numbers, on the track beside the Namatala niver and on the path through the montane forest above Bufumbo at an altitude of about 5000-5500 feet. In these places it is possible AFR/Oncho/8 WHO/Oncho/30.65 page 57

Annex 2

to. catch 200 or 300 flies in abou~ an hour from a small group:. of people. As an example of density in another ~pot .. may be cited one record of 258 flies per catcher per 10-ho~r day, or about 26 F.BH. In general biting occurs in dense forest at altitudes somewhat above the general level of breeding. At peak times near the Namatala over 200 F.BH. High infection rates with filariae occur among flies caught on Mount Elgon, but Nelson's work in 1959 has shown that at least two filariae other than o. volvulus occur here in S. neavei: for full details of numbers of flies dissected and infection rates, reference may be wade to Nelson's paper. S. damnosum is absent from the Mount Elgon area.

Personal observations on Mount Elgon include the following: collection of S. neavei larvae and pupae from crabs in the Sume, Manafwa, Nakokolo and Zuzu streams, and the collection of over }00 adult s. neavei in one and a half hours spent in the forest above Bufumbo. One of the writers found five s. neavei engorging on his thighs while crouching down examining a stream in the forest. Some 50 crabs were collected from five or six streams between Sipi and Kapchorwa at about 6000 feet and found no s. neavei attached to them, the findings tending to confirm all VCD experience that s. neavei breeding around northern Elgon in Sebei District is below this level.

People in the Bufumbo area are very well aware of the Mbwa fly, and a group of young boys was most co-operative and eager to act as bait and point out flies for capture.

Probably more is known about the vector on Elgon than elsewhere, especially as the forest above Bufumbo is the most intense s. neavei biting area known in Uganda. But the 1957 control work partly foundered because of inadequate study of higher reaches of streams, and renewed survey in detail would be needed before any further control is tried, especially an eradication programme on a large scale. The maps of Elgon are by no means sufficiently reliable for the refined planning of a control scheme involving dosing of every stream, and we consider that in this area particularly, any onchocerciasis control· team would need to make the most diligent reconnaissance of every bit of the ground. As in West Nile and Kigezi, it would be AFR/Oncho/8 WHO/Oncho/30.65 page 58

Annex 2 necessary to spend at least a complete year of pre-control study and survey to ensure that no mistakes were made through missed tributaries, and for the acquisition of immediate pre-control fly-round data for comparison with post-control data.

}.4 Control

An attempt was made to control on Mount Elgon in 1957 in order to protect a proposed coffee research estate. The attemp~_!/as made by the VCD personnel with voluntary assistance from the local Bugisu. Departmental staff dosed 140 points with DDT at the rate of one part per million. The voluntary helpers were to place mosquito netting bags containing DDT suspension absorbed on vermiculite in the head waters of their own streams. The operation continued from 4 January to 17 April. It was unsuccessful for two reasons. The Kenya experience that P. niloticus is the only phoretic crab does not apply to Mount Elgon. Some of the smaller tributaries .. .. were not dosed (Barnley & Prentice, 1958).

In this large focus in difficult terrain the discovery and access to all the small' streams remains a problem, especially in the south and west. It is the only focus where it has been suggested that full public support for the control,.. operations might not be forthcoming.

· Agreement between Uganda and Kenya will be required so that the small extension of the focus into Kenya can be dealt with simultaneously. This has been obtained before and there should be no difficulty in obtaining it again. The best approach would be for the Uganda VCD to deal with the extension with permission from Kenya. ·~ - Control measures involving the use of aircraft are not feasiQle in this focus.

4. MURCHISON NILE FOCUS

4.1 Description

Administrative districts: Acholi and Bunyoro, perhaps just into Lango.

Area 400 square miles (inhabited area, including empty game park very much larger).

Population at risk 10 000.

Tribal groups Mainly Acholi. AFR/Oncho/8 WHO/Oncho/30.65 page 59

Annex 2

Main crops . Millet, cotton •

Population movement Settled villagers, local poaching and tribal h\mts, tourist visitors.

Vegetation Open savannah woodland north of Nile, open grass plains to south, .no forest but slightly more developed cover along rivers.

Relief and drainage Rather flat or slightly rolling open landscape, drainage by several tributaries not carrying much water into main Nile from north and south, tributaries sometimes not flowing in dry season.

Altitude Land rising very gradually .from 2500 feet in west to 3100 feet in east.

Roads : Main roads very good but few and crossing Nile only at Karuma Falls, otherwise only a few motorable tracks in game park.

Isolation Not well isolated from nearest s. damnosum areas, but far from nearest areas where the fly is man-biting, l()5·miles from Victoria Nile.

4.2 The disease

The VCD has carried out surveys of the disease in the inhabited eastem end of this focus and have found a skin snip positivity rate of between 70 and 80 per cent. at Koich and Atura.

There is no information· available about the il~-health caused by the disease or its complications.

The population is more aware of the Simulium nuisance than the disease. The DMO Gulu is aware of the problem and realizes that the solution of the problem of continued transmission must be solved before the question of treatment is considered.

It would be advantageous if a more detailed para&itological survey could. be undertaken to provide base-line data. AFR/Oncho/8 WHO/Oncho/30.65 page 60

Armex 2

4.3 Entomology

A brief account of this area is given by Barnley (1961), but no detailed account is yet available: the main source of information is therefore the VCD files.

The VCQ between 1953 and 1958 found s. damnosum breeding all along the Murchison stretch of the Nile from Amenyi Rapids to the Murchison Falls, and in parts of some tributaries entering the Nile between these two points. Almost no biting could be found near the river itself, despite heavy larval populations in the Nile, but much biting was found near the village of Koich some 30 miles away, largely across uninhabited game park. Here the biting fly density is very high, especially in early morning, and infected flies have been found. The area is at present being intensively investigated by the VCD which is obtaining data on all aspects of S. damnosum entomology in this area, particularly on where the flies biting at Koich

originate .(whether in the main Nile or in trib~taries) and on transmission. Consider­

ation i~ also being given to the mystery of where and on what S. damnosum near the Nile are feeding.

The Murchison River near Murchison.Falls, near its point. of entry into the: Nile was visited, .. put no. S. damnosum were found biting; the Murchison River was unusually full and no breeding survey could be made. At Koich numerous adult damnosum were collected biting in the early morning between 7.30 and 8.30. A brief visit was made to the new Chobi Lodge site on the Nile bank below Karuma Falls Bridge ahd the Karuma Falls, but ·no adult flies were seen; one adult s. damnosum was caught in the Land­ rover at a stop by the Karuma Bridge.

There is almost no human population along the Murchison Nile, as it runs through the Murchfson Falls National Park, but workers at the Chobi Lodge site are unaware of the fly, and the labour force building the Karl.''lla Falls Bridge (completed 1963) were never trou:t>led by biting. · However, at Koich there is considerable local awareness of the fly, .where it is biting persistently.

Some of the main entomological needs are to determine the source of flies biting in the Koich area, to try to find put whether non-anthropophilic flies near the Nile are likely to take to man-biting if large numbers of people such as groups AFR/Oncho/8 WHO/Oncho/30.65 page 61

Annex 2

of tourists enter the area, and on what animals the flies ne~r the Nile are subsisting; for future control it is essential to locate all the places where S. damnosum is breeding in the rivers such as the Aiago running into the Nile. All of' ·these points are being actively investigated by the VCD at present.

4.4 Control

VCD departmental files are the only $Ource of information yet on control in this focus. Proposals to build a hydro-electric plant at Karuma Falls, together with occurrence of onchocerciasis near Koich presumed to be transmitted by flies from the Nile, inspired the attempted control of S. damnosum on the 50-mile stretch of rapids along the Murchison Nile. Electricity transmission towers were erected on either s~de of the river above the highest breeding rapid and insecticide delivered into the water from a perforated polythene pipe stretched between the towers; 12 per ~e~t. DDT ~~s used in a 50/50 mixture of dies_eline and power kerosene, the formulation being mixed on s:f.te at Amenyi. Preparations for dosing were attended by some publicity before the first dose of 1000 gallons weni in in J~uary 1959; this first dose was followed by 11 weekly doses of 500 gallons. At first there appeared to be great success with apparently total clearance of all larvae to the end of the infested stretch at Murchison Falls, but within six months of dosing there was extensive reinfestation with adult fly densities at Koich greater than before. Barnley attributed the failure to separating out of solid DDT which floated in lower reaches and failed to eliminate larvae; there may also have been reinfestation from unlmown breeding sites 'in tributarieS.···· No further control has been attemptec. on Murchison Nile.

The main difficulty in the focus is that it is not yet clear whethel' ·successful control would necessitate dosing of tributaries as well as the main Nile, and this problem is under investigation by the VCD. Eradication might involve simultaneous dosing of all tributaries as well as the Nile in the wet season; the tributaries flow largely through trackless long grass plains in Murchison Falls National Park where access from the ground will be difficult and larviciding from aircraft may be required. Aerial control should prove feasible in such open country. AFR/Oncho/8 WHO/Oncho/30.65 page 62

Annex 2

5. BUDONGO FOREsT FOCUS

5.1 Description

Administrative district: Bunyoro.

Area 300 square miles.

Population at risk 7000.

Tribal groups Banyoro.

Main crops Cassava.

Population movement Little, immigration from West Nile.

Vegetation Dense moist forest (Budongo and Siba Forests) with elephant grass and scrubby forest remnants and savannah outside.

Relief and drainage Undulating with a few hills, rather flat in main forest areas, streams draining through forest towards north-west and forming two main rivers flowing to Lake Albert.

Altitude 3200-3900 feet.

Roads Good to and on outskirts of area, logging tracks only within forest.

Isolation Fairly good for s. neavei focus, southern edge of Siba Forest 22 miles from northern side of Budoma Forest.

5.2 The disease

Transmission .in this focus has been stopped (Barnley & Prentice, 1958, Prentice, 1963) so that the pre-control situation is of only historical interest.. A pre,­

control survey showed t~at 78 per cent. of 250 labourers at Budongo sawmills and the entire staff, plus 46 per cent. of the students at the Forestry school, were infected.

The residual problem is the treatment of those who were infected before control. AFR/Oncho/8 WHO/Oncho/30.65 page 63 Annex 2

At Hoima both the DMO and the med:i.cal staff of the hospital were interested, but disturbed by the difficulties of treatment. The concll..isioii :reached was that there

was no alternative to repeated course~ of hetrazan treatment~· in spite.of the unpleasant symptoms following the first dose.

An interesting observation was the ::l.mmigration into the area now controlled on

the ed6e o~ the forest of settlers from West Nile. Many were infected with oncho-

cerciasis. They recognized the cause of th~.disease and.,demanded treatment.

5.3 ~omoio~

The main source of information is the paper of _Bamley & Prentice (1958).

Th~ VCD found at its first survey in this area in 1955 that s. neavei was an

intense biting nuisance in the Budongo Forest where th~ labour and staff of the

sa:;r.l5.lls and Forestry Department esta}:)lishm~l)ts were much afflictE!'d by the pest.

Searches for breeding showed. tha:t .:!leavy inf~s.tations. of larvae and pupae occurred on

two speoi_es of cre.b, f:_E.iloJ~iQus .and P. granviki (? 0. berardi) , . in the streams : · meandering through the Budongo and Siba Forests and in stretches of larger rivers formed by these streams outside the forest; up to 36 larvae and 10 pupae Jtere found ' ~ ._· . on a single medium-sized crab. A control scheme was planned for the protection of those \'torking in and around the forest, initiated in November 1955, .cu.:td continued to date: S. darrinosum has beeT'. found on WA.ki River, but does not bite man.

During the v::l.sit about 60 crabs were collected (all P. niloticus and mostly very large specimens, in one case 14 on a single trap) from the Sonso River in Budongo

Forest, but all were negative for S. neavei; a few crabs ca1~t in the Waki River in Siba Forest (the other species) were also all uninfested. Control thus appears

to continue completely e~.ectively.

People newly resident in the area were, as one would expect, through the great success of control, unaware of the fly; on the other hand, people with long residence in th9 area to whom the writers spoke such as Mr Kershaw, the mill engineer at

Buchanan's Sawmills, rem(~bered all too well what a frightful pests. neavei had been before 1955. AFR/Oncho/8 WHO/Oncho/30. 65 page 64

Annex 2

The only entomological requirements here now are continued surveillance of the effects of control, and possible stopping of dosing to see whether eradication has been achieved by the gradual attrition effect of repeated dosing over a protracted period.

5.4 Control

·rhe main source of information is Bamley & Prentice {1958) • A control scheme against s. neavei was started in the Budongo Forest focus in November 1955, and has continued to the present time. Several but not all of the streams running through the forest are dosed, originally at intervals of 10 days, but now every six weeks. Initial dosing was with 0.5 ppm DDT applied over 30 minutes, Shell Arcotine SO 18 water-miscible concentrate being used. The control scheme has been extremely successful and no adult flies have been obtained since November 1957, two years after dosing began: s. neavei may in this area have been eradicated in fact by a process of attrition despite the fact that not all its breeding sites were dosed, but the finding of an s .. neavei larva on a crab collected during assessment inspection in 1961 makes thi a uncertain.

As control has been achieved, the only problem here is to find out if total eradication of the vector has also been obtained quite incidentally. This would necessitate the stopping of dosing, but if this was done, it might be difficult to

; get the dosing procedure resumed so successfully. Aerial control is not relevant.

The cost of control in Budongo Forest has worked out at about two cents per acre per year.

6. BUGOMA FOREST FOCUS {not seen personally)

6.1 Description

Administrative district: Bunyoro.

Area 200 squ~e miles.

Population a~ risk · : 3000.

Tribal group Barworo. AFR/Oncho/8 WHO/Oncho/30.65 page 65

Annex 2

Pop~ation.movement : Little • . ~ . ·. '~ . .

Vegetation Moist· semi~deciduous· forest,· sparser than Budongo Forest/' elephant gr.ass and forest remnants.outside main forested areas.

Relief and drainage . Rather flat country with a few scattered hills, streams ; araining north and north-west to Now a River and south and south-west to Nkusi River and thence to Lake Albert.

Altitude : 3400-3800 feet i ·few hills· reaching over 4000 feet.

Roads Only two rather poor, lead1ng'• westwards' from main Hoima- ,· ·.: '-· :··: Fort Portal road. .::; ;._ :!.....::. _. ..•. . Northem edge of forest, ~ miles from southem edge of

•·l• t. ..,. ····; ... Siba Forest.

6. 2 · The dfs'ease .: .! -., .- "- . r The. source of information is a survey''by vco' in 1963. At the Sikh sawmills 58 employees were examined and five ·round infected, of these three had probably been infected elsewhere. Of a group of 157 living in the focus, nine were inf'ectedj three of these were immigrants _from West Nile. As the forest is apparently very similar to Budongo, these low rates are surprising.

The DMO Hoima, was, in no doubt. that. there were very few complaints from Bugoma;

.most of the complaints about onchocerci~sis came fro~Budongo.

It seems that infection is occurririg at ·a ·low -ra:te', but that there is little awareness of the disease.

Bugoma will probably be controlled more to protect Budongo than to deal with the local problem.

6.3 Entomology

Only source of information is VCD file. Only survey here in any detail is that made by the VCD in May 1963, when s. neavei was found to bite freely in a logging clearing in the forest where two people collected nearly 500 flies in two days. Of AFR/Oncho/8 WHO/Oncho/30.65 page 66

Annex 2

these flies 466 were dissected, of which 32 per cent. were parous: among the parous flies two per cent. were infected and 0.67 per cent. had infective forms of filariae which may have been 0. volvulus: however, as S. neavei may harbour at least three different filariae in some parts of Uganda, the identity of the worms seen is not certain.

Bugoma Forest is a relatively minor focus, not yet studied in very much detail,

and we did not visit the area pe~sonally.

Main entomological requirements if control is contemplated will be study of the breeding distribution of S. neavei in the area to determine focus limits and dosing points, and more information on pre-control·adult biting density to compare with post- control firtdings. The S. damnosum situation would also need assessment, as this species occurs on lower Nkusi River (southern edge of Bugoma Forest) and may exist in other rivers in the area: in this area it may, however, be non-anthropophilic. (The writers found that S. damnosum breeds in large numbers in the Nkusi/Kafu River

at the crossing of the Hoima-Fort Portal road, not far from the Bug~~a Forest, but did not find biting; police at a road barrier post here said they were not bitten.)

6.4 Control

No control has yet been carried out in this focus.

~e Pr9blems here for future control are likely to be much the same as those for the Budongo Forest focus, though the lack of a severe disease problem may make it more difficult to obtain the ready collaboration of those working in the forest. Aerial control would not be appropriate in this focus, largely because of forest cover. AFR/Oncho/8 WHO/Oncho/30. 65 page 67

Annex 2

7. RUWENZORI FOCUS

7.1 Description .. ·: ,.· Administrative district: Toro.

Area 1000 square miles.

Population at risk : 100 000.

Tribal groups : Batoro, Bakonjo, Baamba ... .· -,

Main crops Banana, cotton, cassava.

Population movement · :· Very little ·among people living lower down, Bakonjo stay on mountain but move a little up and dawn valleys, immigration of refugees and mine workers.

Vegetation Scattered scrubby·f~rest'up to'1ooo feet ~ith gallery forest along rivers, dense forest above-7000 feet, some woodland savannah and grassland savartnah• aroUnd' southem end.

Relief and drainage Part of base plain and foothills below mountain, and partly lower mountain slopes, traversed by radial or subparallel s'e:de'$ Of fast cold turbulent rivers which flow separately '. eastwards and southwards and dwindle to .swamps before entering Lakes George and Edward.

Altitude 3000-7000 feet.

Roads. Good main road skirtiJl6 m()untain. to east and south with some spur roads penetrating valleys. .. . ~ Isolation Doubtful, not far from- source of s. neavei in.Kibale Forest and from source of non-anthropophilic damnO$Jllll· at north end

of massif, s~tuation over Congo border a?ross Lubilia River not known. AFR/Oncho/8 WHO/Oncho/30.65 page 68

Annex 2

7.2 The disease

The main source of information is the investigations of the VCD and a special intensive survey carried out at Bugoyein# 1960 (Woodruff et al.# 1963}-r . -···

Surveys have been carried out by the VCD at Bugoye in 1950 and 1958 and in the Nyamagasani valley in 1961.

At Bugoye in 1950, 230 were examined and 54 per cent. found positive. Of those over 30 years of age 90 per cent. were positive; in 1958, 728 adults were examined and 91 per cent. found positive.

In the Nyamagasani valley in 1961# 54 per cent. of 1356 examined were infected. Examinations were carried out in six localities; infection rates ranged from 15 to 67 per cent.

In the special survey carried out at Bugoye in 1960, 85 persons were examined and 75 found positive. Most of these 75 were given an intensive clinical and ophthalmological examination. Those examined were volunteers and biased towards diseases of the eyes.

The intensity of infection rose with age, but ·reached a maximum intenSity in the fourth decade. The main complaint was pruritus# though many with heavy skin infections did not suffer from this symptom. Skin thickening, depigmentation and presbydermia showed. in 26, 14 and 13 patients respectively. Of 67 patients, eight showed inguinal and femoral lymphadenopathy, sometimes in pendulous sacs of skin.

Of 67 patients given a careful ophthalmological examination, anterior segment lesions were found in 29, posterior in eight and both in 16. In 14 there were no ocular lesions. The posterior lesions were considered to be of indeterminate origin. Of the 67 patients, 27 had a visual acuity of less than 6/60 in one or both eyes; in 13 the cause was considered to be onchocerciasis.

There was no evidence that vitamin A deficiency played any part in causing choroido-retinitis. !iFR/Oncho/8 WHO/Oncho/30. 65 page 69

Annex 2

Altho~'this.survey covered only a small area·andonly relatively few patients . . were examined~ it seems reasonable to accept it as an indication of the effects of onchocerciasis in places where the intensity of infection is similar. It does·not give an·indication of prevalence of eye disease as the sample was biased.

At Fort Portal Hospital onchocerciasis is not considered an important medical problem. The District Health Inspector has received complaints of Simulium biting from areas where damnosum is known to occur. At Ruimi the nuisance has vanished following control.

Surveys at the mine at Kalembe :have shown the disease to be absent, but one min~ engineer based on that mine was: encountered·who had suffered from the disease, but as he had prospected widely in th.e ~~~a:, his·source of·infect1on could not ce ascertained.

It seems reasonable to assume that~:iri· ·the valleys infested with damnosum the effects of the disease are the same as at Bugoye. The writers have no information as to whether onchocerciasis exists in the· neavei areas. Barnley found some of the patients attending the dispensary at Bundibugyo (north-west slopes of mountain) positive for onchocerciasis, but he could .not be sure where they had been infected.

There is no doubt of the awareness of the d~nosum nuisance. The skin changes found at Bugoye are also a cause of complaint. The District Health Inspector has received complaints of biting from most cif the infested river valleys. He has also received complaints from Bovassba, but the insects biting have not been identified.

The most urgent parasitological requirement seems to be the assessment of the part played by neavei in causing onchocerciasis in this area and confirmation of the absence of the disease in the areas to the north of Ruwenzori where damno~ is considered to be non-anthropophilic.

7.3 ~tomology

.. 'Ihe main sources of information are Ba.mley (1961) and the survey~ of the VCD. ·, The paper of Woodruff et. ·ai. (1963) includes entomological notes. AFR/Oncho/8 WHO/Oncho/30.65 page 70

Annex 2

Surveys have shown that S. damnosum breeds in and bites in very large numbers near several rivers in the area, particularly the Ruimi (before control), Hima, Mubuku, Sebwe, Nyamagasani, Kanyampara and Lubilia, but not in the mine-polluted Kilembe. Round the north end of Ruwenzori this species also breeds in some northward flowing rivers in the Bundibugyo area, but appears there to be non-anthropophilic. On the Ruwenzori foothills S. damnosum is an intense biting pest occurring in densities of up to 200 FaH and more-near the rivers; biting rate declines to about 20 F.8H some two-and-a-half miles from the rivers, and to about 5 F.BH some five rniles away. · In some rivers in this area S. neavei occurs as well as S. damnosum, but is more generally widespread at altitudes above those where s. damnosum is found; evidence that

S. ne~vei bites man around Ruwenzori is so far inconclusive. In general S. neavei breeds between 4500 and 6500 feet, and S. damnosum below 4500 feet. At Bugoye the S. damnosum dens! ty varied between 3 F.8H and 62 F.BH ace ording to the hour of <;lay (midday lull). In Mubuku valley 1110 S. damnosum have been caught in 10-hour catch, and of these 3.8 per cent. had infective forms of a filaria, presumed 0. volvulus; in another sample of 388 flies 6.7 per cent. had infective forms.

Duri~ the visit it was confirmed that there was no breeding in the controlled

Rui!fii FU.ver, and fo~d. breeding of S. damnosum in the Mubuku, Sebwe and Nyamagasani; at all of these numerous flies were found biting. Many flies biting were also obtained at the Kanyampar and Lubilia Rivers~ but no search was made for breeding. Time did not permit getting up to the S. neavei areas.

Awareness of the flies is very intense in this area. A Sikh contractor at the Ruimi Prison Farm site spoke of the intolerable biting (which forced those working there to wear long trousers) before the dosing of the Ruimi began in 1963.

The main..... entomological·. . requirement is the study of s. neavei to find out whether this species is actually non-anthropo?hilic in the Ruwenzori area, or whether it bites and transmits. That S. damnosum should be intensely anthropophilic all round the eastern and southern side of the mountains yet apparently non-anthropophilic to the north is a curious paradox and further investigation of s. darnnosum in the Semliki AFR/Oncho/8 WHO/Oncho/30. 65 page 7l

Annex 2

Forest area is desirable. It may be mentioned here that the Kibale Forest area south-east of Fort Portal needs further· ~urvey for S. 'tte:av.-ei; very abundant larvae and pupae of presumed S. neavei were foUnd on crabs collected in the Kibale Forest at the c:- :>ssing of the Dura River about 20 miles south of Fort Portal.

7.4 Control

Apart from departmental files, the main source of information is Barnley (196lJ. The object of control here has been to determine whether anything could be done to ·.. · ··. control S. damnosum in a river in the centre of a more or less continuous focus. The first experiment was made on Nyamagasani River flowing off southern Ruwenzori and started in April 1961; a 10 per cent. solution of DDT in a 50/50 mixture of Dieselene and power kerosene (with Teepol added as a wetting agent) was applied to the river at a concentration of about 0.1 ppm over 30 minutes. Dosings were made weekly until June 1961 and from July onwards were made at four-weekly intervals. In later work

several tributaries. of the Nyamagasani in which breedifi8.. occurred were .~Jso Aosed,<.:J but th~ experimental work was discontinued in 1962 because of civil disturbance in _.. . :·;~ .. .i. ::· ...._, the area. Preliminary findings on reduction of adult flies were qncouraging. In 1963 control of S. damnosum on the Ruimi River began for protection of the Prison Farm site newly established there, and is continuing·· at present; the r-iver is dosed once every four weeks at a point several miles aoove·the prison site, at a rather theoretical dosage of 1 ppm DDT applied over 30 minutes. Responsibility for dosing rests with the prison, and a member of the prison staff applies the DDT in a quantity determined from a chart supplied by the VCD; though rather ad hoc, the system seems to be working very satisfactorily •

. 'I'h~ .success of the .Ruimi control suggests that s. damnosum can be similarly

controlled on all the infested river~ of the focus. Once started, however, dosing of any river would have to be maintained continuously because reinfestation would othen1ise rapidly recur as a consequence of the known long flight range of the vector in this area. The border problem of s. damnosum on the Lubilia River and the uncertainty as to whether s. neavei is involved make eradication impracticable at AFR/Oncho/8 WHO/Oncho,/30.65 page 72

Annex 2

present. Even successful control will requ~re freedom from civil disturbance in ..•. ·.'' the area and responsible supervision of dosing (.th,e eQ\l~VQcal results of the . ~ ' ...... Nyamagasani work leave some doubts as to whether_qosi~ can be satisfactorily delegated to local health staff).

8. KIGEZI FOCUS

8.1 Description

Administrative district: · Kigezi.

Area 600 square miles. ... ;. . Population at risk 40 000 •

Tribal groups : Bakiga and Banyaluanda.

Main crops : Bananas, tea, coffee.

Population movement : Very little, some emigration to other districts.

Vegetation : Moist evergreen forest on mountains, some savanDah, ~ultivatio~ on.steep slopes below forest tea plantations.

Relief and drainage : Irregular ste~p-sided mountains penetrated by deep forested valleys coQtaining northward draining streams of Ishasha- . : ' -. - ~ ~· [· . Chiruruma systems going to Lake Edward • . . ·' · .... ; · ... __ . . Altitude 3500-8000·feet.

Roads : Moderate to good, within area several good roads· bilt these are inevitably mountain roads as much as possible following

wa~er~heds and clinging to hil~sides, crossing streams in relatively few places.

Isolation Hard to assess, focus presumed to extend. into Congo, possibiy not muCh isolated from Maramagambo and Kalinzu . . . forests where·~ocir:may exist. AFR/Oncho/8 WHO/Oncho/30.65 page 73

Annex 2

8.2 The disease

A survey on onchocerciasis in North Kigezi was carried out by Barnley in 1949· A more intensive survey was made by McCrae in 1962 but it was limited to Kayonzo Gombolola.

Seven localities in Kayonza were stirveyed by Barnley in 1949 with skin snip positivity rates ranging from 42 per cent. to 80 per cent.

In addition he surveyed three localities in Kirima (59 per cent. to 80 per cent. positive) and two in Kambuga (36 per cent. and 72 per cent. positive).

McCrae's surveys in the Kayonza Gombolola showed results somewhat different but of the same order with ,one important exception. In one locality, not surveyed by Barnley, he found an infection rate as low as six per cent.

McCrae came to the conclusion that the skin lesions were causing severe symptoms a~d that there was an association between heavy infection and blindness. He was particularly interested in the effect of the disease on the developing tea industry. He concluded thetea estate was free from risk of infection but that those working as out-grO\'lers were liable to infection. He also showed that the presence of the disease made it less likely that an individual would undertake work on the tea estate.

The tea estate dresser told us that he had not diagnosed any cases on the estate but freely admitted that he had not been trained to recognize the disease. The dresser at Katete who had worked in· several localities in the district and had been trained in the diagnosis of skindisease had f~equently (four or five times a week) recognized the disease at Kayonza, but not at Katete or Kanungu.

It ceems that the disease is a public health problem in Kayonza and is threatening the develop!~ tea industry, reducing the amount of efficient labour available. The . ' extent of the focus eastward from Kayonza is uncertain. The medical authorities in Kigezi are aware of the problem both economic and medical. McCrae's survey was carried out at the request of the district medical officer. The Gombolola chief and people of Kayonza are aware of it as a cause of skin disease and debility.

The main parasitological requirement seems to be a survey to delimit the extent of the focus. AFR/Oncho/8 WHO/Oncho/30.65 page 74

Armex 2

8.3 Entomology

Adult s. neavei were first found in Kigezi in 1948 when De Meillon and Barnley visited Kayonza, before the unusual breeding habitat on crabs was discovered. Since then the only sources of information are departmental reports of the VCD.

In 1949 Barnley returned to the Kigezi focus, and using local children as bait was able to obtain seven adult flies in over lOO boy-hours catching time; five of the flies were obtained on Ishasha River in Kayonza and two on the Chiruruma River in Kambuga. No further entomological observations were made in Kigezi until 1962, when McCrae surveyed the Kayonza area in some' detail. By this time, the crab associati-on being lmown, it was possible to search for breeding distribution; larvae of s. neavei or probably this species were obtained from crabs in the Munyaga,

Bu~, Ntengyere and Mbwa rivers. An unexpected complication was the finding in some watercourse of larvae on crabs which appear to be those of S. ovazzae, a phoretic species presumed harmless and originally described from the Cameroon Republic. McCrae experienced Barnley's earlier difficulty of finding adult flies; only at one place, the upper Mbwa River in thick forest (map ref. 047882 on 1:50 000 series) could any number be found, and here 45 flies were collected in an hour. McCrae's survey showed also that s. damnosum was biting in the Kayonza area in very small numbers, an unexpected finding probably attributable to breeding of this species in the Ishasha River on the Congo border; one S. damnosum adult was caught by a

customs officer at the Ishasha border post. No ~amnosum has yet been proved to be infected in the Kigezi focus, but in McCrae's survey three out of 46 S. neavei dissected were infected (6.5 per cent.), one of these containing an infective form of Onchocerca in the head. The usual crab host, P. niloticus, is absent from the Kigezi focus, and s. neavei attached to another species not yet certainly identified, possibly P. johnstoni.

No adult flies were found during the visit despite some time spent in likely biting sites, including the impenetrable forest and the Ishasha River at the customs post, but larvae (presumed to be s. neavei) were obtained on crabs caught at two places, the crossing of the Chiruruma (Ibalya} River between Kambuga and Kanungu and in the Munyaga River on the Congo border just west of Kayonza; the later site was AFR/oridho/8. . WHO/oncho/36 ~· P5. page 75 .... ·

Annex 2

•.·· •.. _;__ visited between 7.15 and a.,l5 a.m. in case adult s. neavei were biting at this time. A few crabs caught on the Chiruruma River between Bulema and Katete, in the Ntengyere and Ihihizo Rivers, and; a small stream betweelf .. Katete and Kambuga were all negative. ' . I . .,. •· • ·.

The di,~pe~er at.Katete, the te~ estate dresser at Kayonza and other local people questioned knew nothing of the fly, and our impression is that there is little if any local awareness of Simulium biting.

The surveys so far done in Kigezi Highlands were preliminary ones only, and the main entc>rnbi·ogical needs are for much more ·thorough and extensive survey to define -- the areas of S. neav!i and S. damnosum breeding and to detennine more exactly wh~r.~, flies a~ bi ~ing ~ likely to be transmitting. With the very scanty infonnation

•. available it is still, as McCrae in his report points out, only speculation that s. neavei is the principle vector in Kigezi, and it is very necessary to find out in this area what part 1 if· a.riy, S. damnosum is playing in transmission·~ A large-soal,e survey of every entomological aspect 1 preferably lasting at least one year would be ne9essary before a satisfactory plan of operations for control could be evolved. ·.··' .. · ... \ . . Ideally, the extent of vector distribution across the Munyaga-Ishasha border with the Congo needs assessment but we see no hope of this being seriousiypossible in the immediate future.

, •• '.,~ , , I. 8.4 Control ·1}.'! ''

No control has yet been carried out in this focus.

Rivers and streams in this area arise on inaccessible mountain slope:s covered tdth dense forest 1 . @lld f'low through deep valleys where access to breedillg sites and . . ·.·.. : '. . dosing points will be very difficult; however, the number of streams to be reached is fortunately not large. It is a large and poorly defined focus which must be .. ~. _:_. . . presumed to extend into the Congo; infested areas across the border preclude eradication 'from the Uganda side at least_ for the time·being. Aerial control is out of the question in sucll ~rrain. AFR/Oncho/8 WHO/Oncho/30.65 page 76

HISTORICAL RESUME OF WORK TO DA'!E

1862 Speke encountered "Jinja fly" on Nile source exploration.

1863 Speke described the fly, undoubtedly S. damnosum, in his joumal.

1899 Cook noted Onchocerca nodules in Busoga District.

1902 Christy collected "Mbwa flies" near Jinja.

1903 Original description of s. damnosum from flies collected by Christy. 1915 Original description of s. neavei, from Western Ankole.

1921 Uganda railway affected by wood shortage because labour would not cut in area of "Mbwa fly".

1926 Entomological Division of Medical Department. formed.

1932 Fleming and Hennessey described lichenification of skin from Uganda.

Director of Agriculture referred to break in cultivation by Victoria Nile attributable to presence of "Mbwa fly". _,_ Gibbins began work on Uganda Simulium.

1933 Work of Gibbins and Lcewenthal in Jinja focus.

19}4 Gibbins' main account of "Mbwa flies" in Uganda.

1942 Gibbins killed.

1943 Loewenthal established connexion between skin changes and presence of microfilariae in Uganda patients.

1946 Bamley appointed entomologist.

1948 De Meillon's visit to advise on Simulium control on Victoria Nile.

Onchocerciasis and S. neavei found in Kigezi District.

Dr Peter Williams started work in West Nile District.

1949 Onchocerciasis survey in Kigezi District. AFR/Oncho/8 WHO/Oncho/30.65 page 77

Annex 3

1950 Nelson started work as District)-1~ical Officer, West Nile•.

Onchocerciasis found in Ruwenzori area.

1951 Prentice appointed entomologist.

s. neavei found in Wes~Jil'ile District, minor onchocerciasis ·sur-vey •. · s. neavei found on Uganda side of Mount Elgon during visit of McMahon. First dosing of Victoria Nile (by aerial· spraying).

1952 First larviciding of Victoria Nile· (from fire-launch).

Assessment of control on Victoria Nile.

Work by Nelson in West Nile District.

1953 Onchocerciasis found at Mutundu near M\lrchison Nile. s. damnosum found breeding along Murchison Nile.

Onchocerciasis found in Ndaiga Bay area.

Onchocerciasis found at Eondo, Nelson's main survey.

Onchocerciasis surveys at Paidha in West Nile.

1954 Experimental control of Simulium in r1Y~l".. ~n. Toro District.

Srna:ll n\irnbers of s. damnQs.um reappearing in' Victorla Nile focus.

Entomological surveys in Bondo-Arivu area of West Nile.

S. neavei confirmed as vector in West Nile.

Preliminary survey of breeding sites on Mount Elgon.

Antrypol tried in treatment of onchocerciasis in West Nile.

First survey in Budongo Forest area.

1955 Continuation of first Budongo Forest. survey •..

Pilot control project on streams in West Nile.

Control started in Budongo Forest AFR/Oncho/8 WHO/Oncho/30.65 page. 78

Annex 3

1955 Preparations for large-scale Simulium survey on Mount Elgon.

Further onchocerciasis survey in West Nile.

1956 Second larviciding of Victoria Nile (through dam sluices).

Small-scale survey of Kibale Forest and S. neavei confirmed.

First reported onchocerciasis cases from Lango District.

Pre-control vector survey of Mount Elgon.

Post-dosing asse~sment in West Nile.

Dosing continued in Budongo.Forest.

1957 Attempted eradication of s. neavei from Mount Elgon.

Investigations continued in Kibale Forest.

Dosing continued in Budongo Forest.

Last adult S. neavei seen in Budongo Forest focus.

1958 Simulium survey of Ruwenzori.

Simulium survey of Muchison Nile.

Full reinfestation of S. neavei on Mount Elgon.

Researches of Lewis on biting habits of s. neavei on Mount Elgon.

Work of Nelson on Mour.t Elgon on identity of nematodes in S. neavei.

Surveys on Karamoja District without definite result.

McCrae appointed entomologist.

Dosing continued in Budongo Forest.

1959 First dosing of Murchison Nile.

Reinfestation of Murchison Nile.

Dosing continued in Budongo Forest. AFR/Oncho/8 WHO/Oncho/30. 65 page 79

Armex 3

1960 Reinfestation of Jinja focus.

Work of Liverpool group on crabs ;on Mount E:lgori.

Onchocerciasis survey by Woodruff et ~1. at Bugoye. -. . ~ ~: ; : •" . . ' . . Sim\llium surveys of. Ruwenzori· riv.ers. .

Doslng continued in Budongo Forest~···

.. · ...... 1961 Onchocerciasis survey of Nyamagasani area.

First dosing of Nyamagasani system. Third ·dosing or Victoria 'N':fi'e. · --- ·· ·- ·

Li:v:erpo:ol -group· working on 'crabs oii Mount. E:igo~·•.

Dosing continued in Budongo Forest.

1962 Onchocerciasis and Simulium survey of KaY?rtza.area in Kigezi~

Nyamasasanidosing discontinued because of civil disturbance.

onchocerciasis and Simulium survey ·a.t Ruimi River near Ruwenzori • .. ____ ,.._ ~ ··---~ ...... --··. Bamley left _Vector Contr()l Di v;l.sion.

Dosing continued i~ Budongo Forest.

1963 Dosing startPd on Ruimi River.

Onchocerciasis arii Simulium survey of Bugoma ~orest.

Simulium survey of Chobi Lodge site at Murchison Nile.

Onchocerciasis re-survey in Jinja focus·by Bamley and Wilks.

Dosing continued in Budongo Forest.

1964 Dosing continued on Ruimi River.

Dosing continued in Budohgo Forest.

Reinfestation of Jinja focus confirmed. . . Fourth larviciding of Victoria Nile.

Simulium survey of Koich area of Murchison Niie focus.

Colboume and Crosskey visit Uganda for WHO. AFR/Oncho/8 WHO/Oncho/30.65 page 8o

ANNEX 4

LIST OF PERSONAL ENTOMOLOOICAL FINDmGS

Entomological collections were made in each focus during our study tour. These are detailed below for vector species. Most of the records are not new but are given so that the VCD has ready access to the writers' findings. The discovery of S. damnosum breeding in the Nyarwodo River on the Congo border at Goli is believed to be a new finding extending the known distribution of this species in West Nile District.

Species District Locality. Stage

neavei Bugisu Montane forest on Mount Adult flies (about Elgon above Bufumbo 300 in 1-1/2 hours)

neavei Bugisu Sume, Manafwa and Zuzu Rivers Larvae and pupae on near Bulucheke Potamon berardi and P. niloticus I neavei West Nile Ora River on Uleppi-Offaka Larvae and pupae on road P. niloticus

l1 damnosum West Nile Ala River at crossing of Larvae and pupae Arua-Bondo road 1 j damnosum I West Nile Agoi River at crossing of Larvae and pupae : I Arua-Bondo road I ' ! 1 damnosum I West Nile Nyara River at crossing of Larvae and pupae Bondo-Logiri road

damnosum West Nile Nyara River at crossing of Larvae and pupae Uleppi•Offaka road

damnosum West Nile Ora River at Okollo on Arua­ Larvae ! Pakwach road

! damnosum West Nile 1 Nyarwodo River on Congo border Larvae , near Goli ! damnosum Acholi Koich village area Adult flies (anthropophilic)

damnosum Bunyoro South end of Karuma Falls Adult fly (on Land­ bridge rover) . . ... AFR/Oncho/8 WHO/Oncho/30.65 page 81

Annex 4

Species District Locality Stage damno sum Bunyoro Waki River at crossing of Larvae and pupae Hoima-Butiabb road damno sum Bunyoro Kafu River at crossing of Larvae and pupae Hoima-Kyenjojo road (innumerable) neavei Toro Dura River in Kibale Forest Larvae and pupae on at crossing of old Fort Portal Potamon sp. (very to Mbarara road abundant) damno sum Toro Mubuku and Sebwe Rivers at Adult flies crossings of Fort Portal­ (anthropophilic) Kasese road larvae and pupae damn osurn Toro Nyamagasani River at crossing Adult flies of Kasese-Katojo road (anthropophilic) damn osurn Toro Kanyampara River at crossing Adult flies of Kasese-Katojo road (anthropophilic) damnosurn Toro Lubilia River at Congo border Adult flies (anthropophilic) neavei Kigezi Chiruruma River between Larvae on Potamon sp. Kambuga and Kanungu neavei Kigezi Munyaga River on Congo border Larvae and pupae on near Kayonza Potamon sp. damno sum Ankole Beside Kagera River on grasses Adult flies (non­ and abundant breeding in river anthropophilic, very at and near Kikagati on abundant) larvae and Tanganyika border pupae APPROXIMATE KNOWN DISTRIBUTION OF ONCHOCERCIASIS IN UGANDA

ACHOL/

KAIAHOJA ...... l''·,-;.'\.,·'·· I. JINJA FOCUS 2. liT. ELGON FOCUS 3. IIURCHISON NILE FOCUS LAN60 •• WEST NILE FOCUS S. BUDONGO FOREST FOCUS 6. BUGOIIA FOREST FOCUS 7. RUWENZORI FOCUS

BU6ANOA

MILES 0 20 ..0 j I 1 I ! KMS.

Pol .. oreo ift Murchison Nile focus ..,.Mftts oNO coveted by vutor but uninhol:»ited ontl -..tote without onchoctrcioaia -- A..oa of vectots without known disease o-itttd fz:: Ateol ...... diMOH possibly OCCUfS