Bull. Org. mond. Sante | 1954, 11, 679-723 Bull. Wld Hlth Org.

MALARIA CONTROL IN ,

L. MARA, M.D. Senior Adviser and Team-leader, WHO Malaria-Control Demonstration Team, Suleimaniya, Iraq formerly, Senior Adviser and Team-leader, WHO Malaria-Control Demonstration Team, South Malabar

Manuscript received in January 1954

SYNOPSIS The author describes the activities and achievements of a two- year malaria-control demonstration-organized by WHO, UNICEF, the Indian Government, and the Government of Madras State- in South Malabar. Widespread insecticidal work, using a dosage of 200 mg of DDT per square foot (2.2 g per m2), protected 52,500 people in 1950, and 115,500 in 1951, at a cost of about Rs 0/13/0 (US$0.16) per capita. The final results showed a considerable decrease in the size of the endemic areas; in the spleen- and parasite-rates of children; and in the number of malaria cases detected by the team or treated in local hospitals and dispensaries.

During December 1949 a malaria-control project, undertaken jointly by WHO, the United Nations Children's Fund (UNICEF), the Govern- ment of , and the Government of Madras State, started operations in the malarious areas among the foothills and tracts of Ernad and Walavanad taluks in South Malabar. During 1951 the operational area was extended to include almost all the malarious parts of Ernad and Walavanad as well as the northernmost part of Palghat taluk (see map 1 a). The staff of the international team provided by WHO consisted of a senior adviser and team-leader and a public-health nurse. This team was matched by a parallel Indian team consisting of a malariologist, a senior entomologist, two lady health-visitors, a sanitary engineer (provided by the Madras Government for a period of two months during the first year), and the following junior technical and administrative staff: 6 entomological assistants; 7 health inspectors; 2 lady health-visitors; 3 midwives; 22 field assistants; 6 laboratory assistants; 1 laboratory technician; 1 office

a In this map, villages with numbers 1-4 and 24-37, and village no. 30, belong to Ernad taluk; villages with numbers 5-16 and village no. 38 belong to Walavanad taluk; and villages with numbers 17-23 belong to Palghat taluk.

337 - 679 12 680 L. MARA assistant; 1 upper division clerk; 5 lower division clerks; 1 draftsman; 1mechanic; 5 drivers; 3 cleaners; 2 chowdikars; 23 peons; 6 laboratory boys; and 3 ayahs.

MAP 1. AREA UNDER JURISDICTION OF MALARIA-CONTROL DEMONSTRATION TEAM

______------Taluk boundary Rivers and streams Vi Village boundary ^A ^ ^A Foothills Metalled road with milestones . .. Water edge Unmetalled road with milestones

Equipment and supplies were received from UNICEF, which also- together with the Madras Government--provided transport facilities. The Madras Government, in addition, participated by supplying the team with some additional equipment and assuming responsibility for replacing the expendable supplies when they were used up. Since even the most fundamental information about malaria epidemiology was lacking in the areas where the teams were to operate, MALARIA CONTROL IN SOUTH MALABAR 681 a great deal of research had to be carried out in addition to the scheduled control work. It is calculated that two-fifths of the work was devoted to the study of the area during the first year, and one-third during the second year, when the project was extended to new areas. During the first operational year, the cost of the project to the Madras Government represented a total expenditure of Rs 1,16,592/11/-, and during the second year, Rs 1,69,755/5/1. The WHO team withdrew from the operational area at the beginning of December 1951, after handing over all activities and transferring all respon- sibility for their continuation to the parallel Indian team.

Area of Operations (First and Second Operational Years) Description of the area (see map 1) Malabar, which with South Kanara District represents the westernmost part of Madras State, is divided administratively into two distinct parts and South Malabar. Organizationally, consists of several taluks (adminis- trative divisions) within which the villages (" amsoms " in the local idiom) are the first step of the administrative framework of the country. Only in a few cases is the village itself divided, for administrative purposes, into sub-villages (" desams "). The term " village " in South Malabar does not indicate merely a rural agglomeration more or less comparable to a hamlet, but refers to the paddy-fields, rivers, hills, jungle, forests, and all surveyed or unsurveyed land within an administrative boundary. The size of these villages is extremely variable, some covering only a few square miles, some as many as 40 square miles (104 kM2) and some even as many as 300 square miles (777 kM2), as in the case of . The inhabitants of the villages are scattered throughout the entire area and show little tendency to congregate. The edges of the paddy-fields and the network of roads are the only natural gathering-places, and it is here that one finds the highest population density. The distribution of the houses in a village is always very irregular, especially when the geographical area is large and the population relatively small. Malaria in South Malabar is found chiefly along the narrow foothills strip running north and south which follows approximately the very winding contour line of 250 feet (76 m). Beyond the limits of that strip, malaria, as a general rule, does not exist. To the east is the western slope of the , a territory consisting entirely of dense jungle and solid virgin forest which is, in fact, completely uninhabited. To the west of the foothills line malaria decreases very rapidly as soon as the plain begins, and this can be considered a healthy area. However, some minor spots of autochthonous malaria can be found (exception confirming the rule) even within the 682 L. MARA healthy areas of the plain and in limited areas on the western slope of the Ghats. House-to-house visiting in the course of the preliminary surveys in the different sectors showed that of all the cases of sickness found, 27.8 % were due to malaria. The location of the malarious tracts of South Malabar in which the WHO team operated during its two-year stay is approximately between 10045'N. and 11032'N. and 75055'E. and 76050'E. The total surface of this area is more than 800 square miles (2,075 kM2), of which about 500 square miles (1,295 km2) are completely uninhabited and about which very little is known. During 1950 the demonstration was carried out in the malarious villages of and all the others numbered from 2 to 16 in the list on map 1. This area under the jurisdiction of the team located along the foothills of the Western Ghats measured about 140 square miles (360 km2). During 1951 the area was expanded by the inclusion of an additional -175 square miles (455 kM2), incorporating the malarious tracts of 15 more villages in Ernad taluk (24-37 and 39), the village of Attappadi (38) in Walavanad taluk, and the malarious portion of seven other villages (17-23) in the taluk of Palghat. Thus, the total inhabited malarious areas brought under the jurisdiction of the team amounted to approximately 315 square miles (815 km2), representing five-sixths of all the malarious areas of South Malabar. This extension of the activities of the team to new sectors, how- ever, was followed by the loss of the physiographical uniformity throughout the whole scheme because of the differences existing either between the new sectors and those of the first year or between the new sectors themselves. Whereas during 1950 it was possible to claim considerable physiographical uniformity throughout the entire foothills area (which lies at a constant altitude of between 200 and 250 feet (61-76 m)), during the 1951 programme this uniformity disappeared with the inclusion in the scheme of areas such as Attappadi on the eastern slopes of the Western Ghats at an altitude of between 1,500 and 3,000 feet (457-914 m), and the isolated malarious spot around Arimbra and Uragam Melmuri which lies within the healthy area of the Ernad sub-coastal plain. The total extent of cultivated land within the project area at the end of 1949 was 50,547 acres (20,456 ha), which was increased to 52,631 acres (21,299 ha) by the end of 1950. To synthesize in a clear way the description of the physiographical features of the areas under the jurisdiction of the team, together with their most relevant aspects, it is necessary to divide the entire project into three well-defined sectors and to describe the ecology of each. These sectors are: (a) the sector of the highlands, within the Attappadi valley; (b) the foothills line, which is the very narrow strip separating the Malabar plain from the Ghat range; and (c) the isolated area of Arimbra-Uragam Melmuri. MALARIA CONTROL IN SOUTH MALABAR 683

(a) Attappadi (38). This valley, which is very wide and deep, is the beginning of the course of the . It consists of a single village, the largest in the entire project area within Walavanad taluk, and lies on the opposite side of the watershed of the Western Ghats with its open side towards District. Its surface is about 360 square miles (930 kM2), of which roughly only one-third is inhabited. The entire area is very wild, and the general economy of the valley is among the most undeveloped in the entire State of Madras. The valley is very rich in dense jungle and virgin forest, mainly on its western side which, because of its proximity to the watershed, is influenced by the humid and rainy climate of the western coast. The soil is extremely fertile with abundance of water in the western half of the valley. Eastward this abundance decreases and the landscape becomes a good deal drier. The people in the valley cultivate mainly rice, though many other food-grains are produced here and there by the local landowners. An extensive timber- cutting industry is steadily developing in the western side of the valley. The different hamlets are linked only by very rough footpaths, and the sole means of travel within the valley was by foot until a " jeepable " track 18 miles (29 km) long was opened across the valley, by the landlords and local tribes, to facilitate the work of the WHO team after the first spraying campaign, in 1950, with which they had been very satisfied.

(b) The western foothills along the Western Ghats (1-27). In this sector the physiographical features are dominated by the orographical morphology, which winds the foothills line in such an irregular way that it reaches a linear development of about 250 miles (400 km) in an area where the maxi- mum distance between the opposite points is hardly 60 miles (96 km) in a direct line. The existence of special ecological conditions which favour the presence of malaria here is imputable to the very numerous " pockets " that the foothills line makes in surrounding some portions of the easternmost part of the Malabar plain during its winding course. The chief feature of this sector is that it is a transition area. Geographically, in fact, it is the point where the mountain and the plain meet, each giving to the other some of its peculiarities; ethnographically, it is the point where the aboriginal tribes of the hills meet the more evolved populations of the plain; and ecologically, it is the point where the surround- ing conditions of the plain are deeply altered by the existing conditions of the overhanging mountains. The area is very rich in water, which is abundant close to the mountains and mainly in the pockets. Here, a large number of springs and rivulets are the tributaries of a main stream, which generally runs along the axis of the pocket itself. This network of small watercourses, which represents the radical system of the big streams and rivers which flow westward through the Malabar plain as far as the , disappears very rapidly owing 684 L. MARA

to the flowing of the smaller watercourses into main streams and rivers. It is within the first couple of miles from the mountains that the physiography of the plain takes its full individuality, and the new resulting ecology reveals itself to be actually different from that still existing in the near-by mountains. Almost all the inhabitants of the foothills earn their living as agricul- turists. Rice is the main crop, but there is also an important acreage of land cultivated with tapioca; some rubber estates and the timber industry, mainly in Ernad, help the economy of this sector considerably. The network of motorable roads which penetrate the malarious area of the foothills is very poor and is completely inadequate. The extent of the entire sector is about 170 square miles (440 km2). (c) The Arimbra-Uragam Melmuri area (28-37 and 39). This isolated area, which geographically speaking varies considerably from the two others already mentioned, is indeed a very small one. It consists of the innermost part of 10 villages in Ernad which surround a minor hill 9 miles (14 km) from the sea-shore and 15 miles (24 km) in a straight line from the foothills. The ecological conditions here are quite different from those of the foothills of Attappadi, and the difference is at first sight noticeable in the general aspect of the area. Huge plantations, alternating with extensive paddy-fields with a crowded population, contrast with the varied vegetation of the other two areas, while the nakedness of the slopes and the top of the overhanging hill (which reaches the height of 1,500 feet (460 m) contrasts with the dense jungle and the afforested areas of Attappadi and of the western slopes of the Ghats. Water is not so abundant as it is in the foothills region, but, nevertheless, it is sufficient to deal with the agricultural needs of the area. The people earn their living mainly from rice cultivation and from the coconut industry, but an important pepper crop adds considerably to the economic well-being of the area. The total inhabited malarious area in this sector is about 20 square miles (50 km2).

Census and vital statistics The census of the population, as established by the house-to-house visiting of the team staff at the time of the spraying operations and during the various surveys, showed a total number of 120,000 persons living within the jurisdiction of the project. Of these, 90,000 were concentrated in the foothills sector, 18,000 in the Arimbra-Uragam Melmuri'area, and 12,000 in the Attappadi valley. Except for the 12,000 inhabitants of Attappadi valley and the 1,000 per- sons belonging to the hill tribe of the Muttan, which lives on the slopes of MALARIA CONTROL IN SOUTH MALABAR 685

the mountains west of Nilambur, the bulk of the population assisted by the project lives in the low-lying plain. During the first operational year the total population living in the area of operations was approximately 75,000, whereas during 1951 the final target figure of 120,000 was reached with the addition of 45,000 more. Moslem and Hindu are the chief religions throughout the area, with only a very small minority of Christians. The Moslems are mainly con- centrated in Ernad taluk, whereas the Hindus prevail in Walavanad and Palghat. Unlike most of the Moslem communities, the Moslems of Malabar, who belong to the Moplah sect, do not follow the purdah system. Within community, besides the most evolved castes living in the plain, there are some very undeveloped hill tribes, who live in Attappadi, on the slopes of the mountains west of Nilambur, and all along the eastern edge of the foothills, and who, in effect, should be considered pagans. The total number of these aboriginals is about 20,000, of which approximately three-fifths live in the Attappadi area. The local idiom spoken within the project boundaries is , which is the official language throughout the whole of Malabar. In Attappadi, however, the people speak mainly Tamil, thus increasing even more the natural difference existing between this area and Malabar, which lies on the opposite edge of the Ghats range. As a rule the inhabitants of the area do not undertake any mass migra- tory movements. But in spite of this, they have a marked tendency to leave their habitual living-place on several occasions: for instance, the mother who has recently given birth to a child returns for several weeks to her parents' house; the agricultural manpower shifts seasonally to the less inhabited areas or to uninhabited forest, in order to attend to the rice harvesting or to the timber cutting; etc. In addition to this, a Christian Syrians' immigration has been started, mainly in the Attappadi and foothills areas. These Syrians come chiefly from the neighbouring State of -Cochin, being attracted by the cheap cost and good quality of the land. They have already reclaimed from the unproductive jungle a con- siderable acreage of very fertile soil. Considering the marked physiographical differences between the various sectors in which the project operated, it is easy to understand why the social organization, the traditional habits, and the way of living of the local population also differ markedly from one point to another in the area. In Attappadi, for instance, where the population is composed of very pri- mitive aboriginal tribes, the people gather together and live in small hamlets, since this mode of living affords them some protection against the local wildlife. In other places, on the contrary, the people live sparsely distributed throughout the whole area of a village. The houses also differ considerably according to the social status of the owner and the community to which he belongs. Those of the very unde- 686 L. MARA

veloped aboriginals are built of bamboo lattices, plastered or unplastered, with a thick layer of solid mud, while those of the Moplahs and Hindus in the plain are generally much better built, many of them being made of local stone and even having two storeys. The walls of these houses are mainly mud-plastered, though there are some which are also limewashed. The walls in the houses are generally re-surfaced once a year, but, owing to the social and religious differences among the communities, there is no kind of synchronism ruling the practice of this habit throughout the whole project area. Whereas the Moplahs, for instance, usually re-surface walls during Ramazan, Bakrid, or one of their other religious festivals, the Hindus re-plaster for Vishu', , Divali, etc. In addition, both have the habit of re-surfacing their houses after births, marriages, or deaths. In general, every house has a cattle-shed which is located in the imme- diate neighbourhood of the house itself; this, however, does not apply to Attappadi, where in every hamlet there are two or more cattle-sheds at the disposal of the local cattle owners, who assemble their cattle there in a collective way. The concentration of the population also changes considerably from one point to another in the area (see map 2). In fact, from the average of 100 inhabitants per square mile (40 per km2) in the inhabited part of the Attappadi valley, we reach 465 (180 per kM2) in the foothills sector and even 900 (350 per km2) in some parts of the Arimbra-Uragam Melmuri area. Yet a further observation deserves to be made on the distribution of the inhabitants of the foothills sector. Here, along the easternmost edge of the area, in a narrow strip where the plain has not yet started and which is still a part of the mountain and is inhabited only by aboriginal tribes, the con- centration is the lowest in the whole area, reaching about 50 inhabitants per square mile (20 per km2). On the western side of the same sector, in that part where the plain has already started and where the more evolved Moplahs and Hindus live, the density of population increases rapidly westwards until it reaches the average of about 700 inhabitants per square mile (270 per kM2) at the extreme western boundary of the malarious tract of the foothills. The difference in the population densities of the three sectors, as well as being attributable to geographical conditions, seems to be, to some extent, imputable to the peculiar trend of the births and deaths of the population. This is substantiated by the vital statistics (see table 1) compiled by the writer for the three sectors.b

b We were compelled to deal with the problem of the collection of the vital statistics by a direct inquiry, because the data existing with the administrative authorities of the villages were found unsuitable for our purpose, since: (1) the figures collected by the village headmen referred to the whole area of the village, whereas we needed those of the malarious portion only; and (2) the recording of the data was very aleatory, being left to the discretion of the inhabitants, who in fact did not always take care to notify the births or the deaths which occurred in their families, especially when they lived far from the administrative centre of the village, or when the declaration of a death could have been followed by some kind of unwelcome compulsory health measures. (Continued on page 688) MAP 2. DISTRIBUTION OF POPULATION IN AREA UNDER JURISDICTION OF MALARIA-CONTROL DEMONSTRATION TEAM

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b liliiliUlilL Foothills - .------Village boundary . Taluk boundary .___.__, Boundary of the areas in which the team worked Note. - Each dot represents 20 inhabitants. MALARIA CONTROL IN SOUTH MALABAR 687

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The analysis of table I demonstrates that: (a) The birth-rate is high throughout the whole area, although lower in Attappadi than in the Arimbra-Uragam Melmuri area. (b) The infant mortality rate reaches its highest figures in Attappadi and its lowest ones in Arimbra-Uragam Melmuri, and is followed by a dramatic reduction of mortality in the next group (children from 1 to 14 years) which continues to be orientated in the same direction (i.e., higher in Attappadi and lower in Arimbra-Uragam Melmuri). (c) The adult age-group (15-39 years) has the lowest mortality rate of the four groups. The orientation of the adult morbidity rate is also in the opposite direction to the two former groups (i.e., higher in Arimbra- Uragam Melmuri and lower in Attappadi). This, together with point (b), clarifies the different composition of the population in the three sectors, revealing the existence of an adult population proportionately higher in Attappadi than in the foothills, and higher in the foothills than in the Arimbra-Uragam Melmuri area. (d) The category grouping the persons of 40 years of age and over is represented by a very small minority when compared with the other cate- gories. It is also the category, after the infant group, showing the highest death-rate. (e) There appears to be a trend towards an increase of births, and a decrease of deaths and a better distribution of the age-groups, in the three sectors after the epidemic season which followed the spraying operation. From the first four points, we can infer that the population living within the project area has a short average life, mainly because of the high mortality among infants and persons over 40 years of age. This is most apparent in Attappadi, but it is also very evident in the other sectors. However, if it is true that this high mortality rate at the two extremities of life is able to reduce the rhythm of the growth of the population, it is to be pointed out that the death-rate does not succeed in threatening seriously the general increase in population, because, even in those sectors where the

b (Continued from page 686) The way chosen for the recording of the vital statistics through the direct investigation was as follows. In the course of a malariometric survey, the census was taken of all the family members living within a number of houses selected at random. The persons recorded in this way were next classified into four main categories: infants, children, adults, and old persons. This classification, which differs from the usual one, was adopted because it was the only one likely to facilitate our inquiry among the local people, who could not answer our questions about the age of the absent persons more precisely, since they knew neither the age of their relations nor even their own. When all the members of the family living in a selected house had been recorded, the investigation was continued by inquiring about the births which had occurred within the family during the past 12 months and the deaths of infants, children, adults, and old persons during the same period. This investi- gation was carried out during the first malariometric survey of the area, and was repeated during the final survey. Of course the method we followed is to be considered rather incomplete, since the " memory factor " on which it is based results in figures which are only a certain percentage of the total events. However, owing to the fact that the " constant of error " remained more or less invariable, this method was found to be suffi- ciently practical under the existing local circumstances. MALARIA CONTROL IN SOUTH MALABAR 689 birth-rate is lowest and the death-rate highest, the natality is always so strikingly overwhelming that the density of the population still continues to be represented by a constantly rising curve. Point (e) on the other hand, by revealing the changes which occurred after the DDT spraying operations, bears witness, among other things, to the sensitiveness of the method followed for the recording of the vital statistics in these underdeveloped areas, where it was necessary to collect the required data through direct investigation.

Climate From graphs 1 and 2, it is evident that the whole meteorology of the area is influenced by the rainy period, which deeply alters the physiognomy of the seasons, mainly in respect of the distribution of temperature and relative humidity throughout the year.

GRAPH 1. CLIMOGRAMS AND RAINFALL FIGURES FOR TWO TYPICAL LOCALITIES IN THE FOOTHILLS SECTOR

A = Nilambur B - Pottasseri 690 L. MARA

The highest rainfall occurs during the period June-August, when, under the influence of the south-west monsoon, about three-quarters of the total yearly rain falls in the area. Some little showers in April and May, however, may precede the south-west monsoon, while some others may follow it in September. The September showers link the south-west monsoon rain with that falling during October and November under the influence of the north-east monsoon. But both the April-May showers and the Septem- ber and north-east monsoon rains are always very small, as a rule not

GRAPH 2. CLIMOGRAM AND RAINFALL FIGURES FOR THE ATTAPPADI SECTOR

exceeding, altogether, one-quarter of the total yearly rainfall. Further, they have the characteristic of being inconstant and extremely variable from year to year, in respect of both their quantity and their time of ap- pearance. The yearly rainfall varies from one point to another in the project area and from year to year. The greatest quantities fall just at the extreme eastern edge of the foothills, where, in Estate, over the period MALARIA CONTROL IN SOUTH MALABAR 691

1945-9, an average of 173 inches (4,394 mm) has been recorded; in the other parts of the area the yearly average ranges from 80 inches to 100 inches (2,030-2,540 mm). The monthly frequency usually matches the monthly intensity of the rains, which generally show their heaviest fall during July. The yearly curve of the temperature appears to depend on the special trend of the rain. From a period of intense heat during March, April, and May, a dramatic fall of the temperature follows in June, when the south- west monsoon rains start. The minimum average temperature of the year is reached in July. After this month the slow steady rise of the yearly curve starts, bringing the temperature again to its highest values during March to May. A small notch in the curve may be recorded in some cases during December. In Attappadi, however, where the altitude influences the thermal gradient, the fall of the temperature, starting in June, steadily continues throughout the second half of the year, and the yearly minimum is reached in December, thus coinciding with the astronomical winter. After this month the temperature increases very rapidly and reaches its maximum during March to May, as it does in the other areas. The relative humidity shows, throughout the year, a curve which is in inverse ratio to that of the temperature. Its maximum coincides with the maximum of the rains, when the temperature is at its minimum, whereas the minimum is reached in February, when the temperature is already near to reaching its highest point. The following are the most relevant temperature and relative humidity monthly averages recorded in different parts of the project area during the period in which the WHO team operated

Highest monthly temperature 94.50F (34.70C) Nilambur May 1950 Lowest monthly temperature 69.0°F (20.60C) Attappadi W. December 1950 Highest monthly relative humidity 95.3 0/0 * Attappadi W. July 1951 Lowest monthly relative humidity 49.6 0/0 * Anulli (Pottasseri) Februarv 1951 * These figures refer to the mean of the relative humidities recorded at 8 a.nm. and 4 p.m.

Organization of the Area under the Jurisdiction of the WHO Team In order to cope with the special features of the areas, which necessitated travelling long distances between opposite points of the project and resulted in wide ecological variations among the different geographical sectors, the work had to be decentralized. The area was thus organized as shown in map 3. 692 L. MARA

MAP 3. ORGANIZATION OF OPERATIONS UNDERTAKEN BY MALARIA-CONTROL DEMONSTRATION TEAM

Headquarters - Temporary children's clinic 0 Sub-headquarters A Children's clinic Catching station (adults and larvae) * Schools visited regularly 0a) Health inspector's post * Schools visited irregularly Lady health-visitor's post * Point where only rainfall was recorded WHO midwife's post o Point where only temperature was recorded District Board midwife's post e Complete meteorological station Foothills Taluk boundary Village boundary Boundary of the areas in which the team worked

Operations (see map 4)

Spraying operations were started after adequate training had been given to the staff chosen to participate in the campaign. During 1950, owing to the urgency of starting the operation, a WHO sanitary engineer spent one week with the team to organize the spraying campaign, while the malariologist of the international team was busy with the pre-opera- MALARIA CONTROL IN SOUTH MALABAR 693 tional surveys. On this occasion, a malaria engineer was posted by the Madras Government to the parallel Indian team to supervise the conduct of the whole campaign.

MAP 4. DDT-SPRAYING OPERATIONS, 1950 AND 1951

[ Malarious area with spleen-rate Area sprayed in 1950 and 1951

1951 check area 1950 check area (sprayed in 1951) Area sprayed with 50 mg per square foot E 1951 extension area EM (0.54 g per ml) in 1951 Foothills Taluk boundary Village boundary - Boundary of the areas in which the team worked

During the second year, the operation was organized by the WHO team- leader and carried out under the supervision of the Indian malariologist. The personnel were trained by making them spray, in the correct time, a measured area, using water in the pump to the normal capacity and 694 L. MARA keeping the range of pressure between 20 and 35 pounds per square inch (1.4-2.5 kg per cm2). The unit for the work was the spray squad, consisting of one field assistant, two men with pumps, and two others for assistance. From 4 to 6 of these squads were put under the supervision of a health inspector, who was responsible for the proper carrying-out of the operation within a fixed area. The field assistants (squad leaders) were responsible for: (a) weighing the DDT for the day's work; (b) cleaning the pumps and keeping them in good condition; (c) preparing the suspensions from the concentrate in the field; (d) measuring the area sprayed and recording in a book all the details about the number and nature of structures, number of persons living in them, owners' names, etc.; and (e) submitting in the evening a report on the day's work. During the operations, the inner walls and roofs of the houses and cattle-sheds were all sprayed. The sprayed houses were then marked with tar, in order to indicate the date of spraying and the form of DDT used. The spraying mixture used had a strength of 3 % DDT.

.Spraying operations in 1950 and in 1951

The first spraying operations were conducted in the demonstration area c from 17 January through 4 March 1950; the dosage of DDT was 200 mg per square foot (2.2 g per m2); DDT emulsion and suspension were used with Hudson and Lofstrand sprayers respectively. Between 10% and 30% of the sprayed houses were re-plastered before the spraying was completed, but these were re-sprayed by the team from 15 June to 4 July, and the DDT then employed amounted to 14.30% of the total quantity shown in the following figures. Four hundred and fifty-three houses, which were left unsprayed during the regular spraying campaign, were treated in April. During 1951, the spraying operations were extended to the previous year's check area and to the following new areas : Attappadi, Arimbra- Uragam Melmuri, the foothills west of Nilambur, and one northern portion of Palghat taluk. Thus, in all, 315 square miles (815 kM2), having a total population of 115,500, were covered during that year. The rate of application of DDT was 200 mg per square foot (2.2 g per m2), except in a small area (11 square miles (28 kM2); population, 1,250), where a dosage of 50 mg per square foot (0.54 g per m2) was employed. A comparative analysis of the work done and of the costs incurred in the 1950 and 1951 spraying campaigns is given below:

c In this report, the term " demonstration area " refers to the sprayed area, and " check area " to the area left unsprayed for control purposes. MALARIA CONTROL IN SOUTH MALABAR 695

ANALYSIS OF WORK 1950 1951 Total number of structures treated ...... 10,784 24,082 Total number of premises (rooms, stables, latrines, etc.) treated ...... 38,110 83,990 Superficial area treated (m2) ...... 1,514,600 3,665,600 Number of inhabitants directly protected . . . 52,500 115,500 DDT consumed (kg), expressed as 100% DDT (a) emulsion ...... 263 4,536

(b) suspension ...... 2,730 2,732 total ...... 2,993 7,268 Man-hours of labour (including squad leaders) . 32,509 64,535 Man-hours of disinfestors (actual spraying time). 9,763 18,102 Area of treatment operations (km2) ...... 238 812

Average number of premises per structure . . . 3.5 3.5 Superficial area per structure (m2) ...... 141.02 151.87 Inhabitants per structure ...... 4.76 4.75 Technical grade (100%) DDT per structure (g) . 283.0 304.9 Total man-hours of labour (including squad

leaders) per structure ...... 3.02 2.67 Man-hours of disinfestors (actual spraying time) per structure ...... 0.91 0.73 Superficial area treated per capita (m2) . . . . 29.54 31.94 Superficial area treated per man-hour (including squad leaders (m2) ...... 46.59 56.88 Superficial area treated per man-hour of disin- festors (actual spraying time) (m2) . . . . . 155.14 204.41 Actual dosage expressed as technical (100%O) 2.011 2.006 DDT (g per m2) . in the 50-mg experimental area . . . . . 0.53 0.52 Technical grade (100 Y.) DDT consumed per capita (g) ...... 59.6 64.1 Proportion of time spent in travelling to total time required for DDT operations (Y.) . . . 27.6 30.4 ANALYSIS OF COSTS d Rupees 1950 1951 Materials: DDT wettable powder (Rs 0.95 per pound) 13,586 20,280 DDT emulsion (Rs 5.57 per gallon) . . . . 1,534 15,609 Personnel and labour ...... 16,930 29,860 Spraying equipment: Depreciation of 100 sprayers (25% of cost) 1,082 1,352 1)epreciation of auxiliary equipment . . . . 150 300 Transport (including depreciation of vehicles (2% per month) and petrol and oil . . . . 2,193 7,317 Freight charges (including repairs) ...... 6,134 13,492 Total cost of operations ...... 41,609 88,210

d These costs have been calculated in accordance with the instructions issued to leaders of WHO malaria- control demonstration teams in Circular Letter No. 15 (unpublished working document MH.540.50).

13 696 L. MARA

It can be seen, therefore, that the total expenditure in 1951 was more than double that in 1950. But, on the basis of the number of inhabitants protected in the two campaigns (52,500 and 115,500, respectively), the cost per capita was approximately the same in 1951 as in 1950-namely, about Rs 0/13/0 (US$ 0.16). It should be pointed out, however, that the internal freight charges have not been included in the statements, as we have not succeeded in getting them, and that, for both the 1950 and the 1951 operations, the rate of exchange between US dollars and Indian rupees has been calculated on the basis of US$ 1.00 = Rs 4.75. The following analysis shows, for the two campaigns, the percentage of the total cost accounted for by each of the main items: Percentage of total cost Item 1950 1951 Insecticide ...... 46 48 Personnel and labour ...... 41 33 Equipment ...... 2 2 Transport ...... 8 10 General overhead expenses . . . . 3 7

Surveys e Malariometric surveys From the many spleen- and parasite-rates which were recorded in almost every part of the project area during the period of stay of the WHO team, very valuable information has been gathered on the distribution of malaria endemicity in different parts of the area under the jurisdiction of the team, and on the real extent of the success achieved by the spraying operations. Map 5, which shows the malaria distribution within the boundaries of the project at the time the team started operations, very clearly demonstrates how malaria endemicity decreased from east to west in a rapid and uniform regression, and when compared with map 2, which shows the distribution of the population, it brings to evidence the fact that, in the area where the team was posted, the higher endemicity of malaria corresponded to the lower density of population. This is also apparent from the following figures: Spleen-rate Area in Population Density ofpopulation per (%) square miles km2 of the area square mile km' Below IO 0 0 10-19 34 88 31,500 962 371 20-49 82 212 56,750 692 267 50 and over 199 515 29,618 149 58

e These surveys have been carried out according to the technique suggested in unpublished working document Mal/Dem/l Rev. 1, i.e., the persons were examined standing up. The data referring to the mala- riometric indices were recorded in children aged from I to 10 years. MALARIA CONTROL IN SOUTH MALABAR 697

MAP 5. DISTRIBUTION OF MALARIA IN AREA UNDER JURISDICTION OF MALARIA-CONTROL DEMONSTRATION TEAM, DECEMBER 1949

0 Malarious area with spleen-rate below 10% Foothills 3 m Area with spleen-rate from 10% to 19% Taluk boundary Area with spleen-rate from 20% to 49% Village boundary Area with spleen-rate of 50% and over Boundary of the areas In which m the team worked As regards the classification of the various degrees of malaria endemicity, it can be said that hyperendemic and mesoendemic malaria were the types chiefly represented in the area before spraying operations were started. Hyperendemic malaria extended over 63 % of the whole territory where only 25 % of the population of the project were living, whereas mesoendemic malaria was distributed over not more than 37 % of the total area which, in contrast, was much more densely inhabited, having about 75 % of the entire population. No definite tendency to holoendemicity existed in the areas where the values for the spleen-rates were 50 % and over. The adult population in fact participated in the epidemic waves as much as the children did. Only in Attappadi, perhaps, was there a tendency for some kind of tolerance to be acquired by the adult population, who showed spleen-rates somewhat lower 698 L. MARA than those of the children, but not to such an extent that it could allow this area to be classified as definitely holoendemic. On the other hand, the way that transmission occurred-it was also discontinuous in Attappadi, even if it was more intense than in the other sectors-interfered with the possibility of creating a status of the adults' tolerance to malaria. The following figures, showing the spleen- and parasite-rates (by age- group) in the three sectors of the project, clearly give the position of the existing degrees of malaria endemicity before the start of the DDT cam- paigns. Age-group Spleen-rate /°. Parasite-rate % (years)(ye-group examinednumber positivenumber positive examinednumber positivenumber positive A. Foothills sector (survey: December 1949-March 1950) 1- 5 243 98 40.3 141 10 7.1 6-10 397 142 35.8 201 7 3.5 11-20 78 24 30.8 78 2 2.6 21-30 81 27 33.3 81 3 3.7 31-40 56 16 28.6 56 1 1.8 41 andover 41 8 19.5 41 0 0 B. Arimbra-Uragam Melmuri sector (survey: January-March 1951) 1- 5 278 78 28.1 218 8 3.7 6-10 392 99 25.3 392 14 3.6 11-20 62 12 19.4 62 1 1.6 21-30 72 11 15.3 72 2 2.8 31-40 40 5 12.5 40 1 2.5 41 and over 32 3 9.4 32 0 0 C. Attappadi sector (survey: April and May 1950) 1- 5 101 87 86.1 101 38 37.6 6-10 158 143 90.5 158 50 31.6 11-20 27 17 63.0 27 6 22.2 21-30 32 15 46.9 32 5 15.6 31-40 29 12 41.4 29 3 10.3 41 and over 16 4 25.0 16 1 6.3 As regards the prevalence of malaria parasites within the project limits, analysis of the data supplied by the positive blood smears collected in un- sprayed areas during the various parasite surveys shows that, whereas Plas- modium vivax prevailed over P. falciparum in the foothills sector, the terms of the proportion were reversed in the Attappadi valley, the second species dominating the first, as shown by the following figures: Total Plasmodium Plasmodium Plasmodium positive] falciparum vivax malariae Foothills sector ...... 143 42 94 7 Attappadi valley . . . . . 155 94 59 2 P. malariae, as these figures show, accounted for a very low proportion compared to the other two species, and its presence is to be considered of infrequent occurrence. MALARIA CONTROL IN SOUTH MALABAR 699

If the knowledge of malaria distribution throughout the project area before the spraying operations were started is of very great interest, the knowledge of the variations induced in the spleen- and parasite-rates as a result of the DDT campaigns is even more interesting, on account of the dramatic changes which occurred in the general physiognomy of the malaria endemicity throughout the entire project area. Maps 6 and 7, when compared with map 5, are very demonstrative of the regression of malaria endemicity during 1950 and 1951. In fact, they show a clear trend towards the disappearance of the hyperendemic areas, together with the substitution of the mesoendemic ones by areas of hypoendemicity, which were not present within the boundaries of the project at the beginning

MAP 6. DISTRIBUTION OF MALARIA IN AREA UNDER JURISDICTION OF MALARIA-CONTROL DEMONSTRATION TEAM, DECEMBER 1950

Em Malarious area with spleen-rate below 10% Foothills * Area with spleen-rate from 10% to 19% Taluk boundary M Area with spleen-rate from 20% to 49% Village boundary Boundary of the areas In which M Area with spleen-rate of 50% and over the team worked 700 L. MARA

MAP 7. DISTRIBUTION OF MALARIA IN AREA UNDER JURISDICTION OF MALARIA-CONTROL DEMONSTRATION TEAM, DECEMBER 1951

II- ILfE7. .

ap ---Is I, I 4''e

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- El Malarlous area with spleen-rate below 10% Foothills N Area with spleen-rate from 10% to 19% Taluk boundary * Area with spleen-rate from 20% to 49% Village boundary Boundary ofthe areas In which * Area with spleen-rate of 50% and over the team worked of the operations. The extent of these changes is clearly shown in the following figures: Spleen-rate (Y.) Area at the beginning of operations Area by the end of 1950 * Area by the end of 1951 square miles % square miles Y. square miles % Below 10 0 0 38 12.1 102 32.4 10-19 34 10.8 54 17.1 37 11.7 2049 82 26.0 50 15.9 119 37.8 50 and over 199 63.2 173 54.9 57** 18.1 * Only 92 square miles were sprayed during the first year's campaign. ** Of these 57 square miles, 29 belong to the check areas. Table II, which shows the results of the spleen and parasite surveys carried out at different times in the different sectors of the project area, also bears witness to the reductions that have been recorded in these rates MALARIA CONTROL IN SOUTH MALABAR 701

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a) u- ac* Q)C a- L / 0,w a) '' a) .0 Qa) a)a*E a) EE Ea Sc .as 702 L. MARA

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c)C 2 (-) _x _'O 0OU) ,E) E (D a) E a a) 0 IC -4 (° ) U') MALARIA CONTROL IN SOUTH MALABAR 703 as a result of the spraying campaigns. Furthermore, the effectiveness of the DDT operations is even more clearly demonstrated by the comparative analysis of the trend of the rates in the unsprayed areas, which showed a general tendency to increase during the very period when the dramatic drop occurred in the sprayed areas. In terms of an overall estimate, covering the entire area of operations, the rate of fall of the spleen indices amounted to 56.80% and that of the parasite ones to 78.00%, the former having dropped from 33.60% to 14.5 % and the latter from 4.1 to 0.9%. The mesoendemic areas recorded the highest rate of reduction, whereas the hyperendemic ones showed some tendency to record lower reductions, although they, too, reported most satisfactory results. The maximum reduction was noticed in the Arimbra-Uragam Melmuri sector, where the rate of reduction in the spleen indices was 79.00%; the minimum was recorded in the area sprayed with 50 mg per square foot (reduction rate, 43.5%). This reduction of the malariometric indices, which was more marked in the mesoendemic areas than in the hyperendemic ones, is very probably imputable to the higher density of population in the former as compared with the latter. In fact, the higher population density, by resulting in a greater number of houses and therefore in a larger surface sprayed with insecticide, actually caused the control to be more effective.

!nfant parasite-rate The infant parasite-rate recorded in the course of the pre-operational surveys of 1950 and 1951, when compared with the data collected in the post-operational surveys, showed the following figures in the demonstra- tion and check areas:

1950-51 operational area (a) Pre-operational surveys (December 1949-March 1950): Demonstration area Check area Number of infants examined ...... 153 102 Number positive ...... 4 5 Percentage positive ...... 2.6 4.9 Percentage positive for P. falciparum ...... 25.0 0 Percentage positive for other species ...... 75.0 100 (b) Post-operational surveys (April 1950-February 1951): Demonstration area (after a single spray) Check area Number of infants examined ...... 708 339 Number positive ...... 3 16 Percentage positive ...... 0.4 4.7 Percentage positive for P. fakciparum ...... 33.3 43.7 Percentage positive for other species ...... 66.7 56.2 704 L. MARA

(c) Second year's post-operational surveys (March-October 1951): Demonstration area Check area (after two sprays) Number of infants examined ...... 54 19 Number positive ...... 0 1 Percentage positive ...... 0 5.3 Percentage positive for P. falciparum ...... 0 0 Percentage positive for other species ...... 0 100 1951 extension area (a) Pre-operational surveys (December 1950-February 1951): Demonstration area Check area Number of infants examined ...... 44 10 Number positive ...... 5 1 Percentage positive ...... 11.4 10.0 Percentage positive for P. falciparum ...... 80.0 100 Percentage positive for other species ...... 20.0 0 (b) Post-operational surveys (March-October 1951) Demonstration area (after a single spray) Check area Number of infants examined ...... 224 31 Number positive ...... 11* 8 Percentage positive ...... 4.9 25.8 Percentage positive for P. falciparum ...... 18.1 0 Percentage positive for other species ...... 81.9 100 * Of these 11 infants, two belonged to the sprayed locality of Veeranur (which is only one furlong (200 m) distant from the unsprayed locality of Chindaki), and a third left the sprayed area and lived for some time in the check area during the transmission season. For the remaining eight infants no investigation could be carried out, since the results of the analysis of their blood-tests were supplied after the international staff had withdrawn from the project area.

Monthlv infant parasite-rates Table III shows the monthly parasite-rates of infants born after the spraying campaigns of 1950 and 1951. This table demonstrates very clearly that the main period of transmission occurs between May and August. It is to be pointed out, however, that evidence has been recorded of some transmission occurring even in the last quarter, or at the beginning, of the year. For example, three positive infants, born in December, January, and April and aged 40 days, 4 months, and 4 months respectively, were found in the course of the infant parasite survey, and a 6-month-old infant, belonging to the group of infants periodically visited, showed parasitaemia in October 1950, after its blood had been found negative in the course of the previous examinations. As a matter of fact, the physiognomy of the malaria transmission within the project boundaries is very peculiar. The extremely varied geo- graphical aspects and the annual meteorology of the area being the chief MALARIA CONTROL IN SOUTH MALABAR 705

TABLE III. PARASITE-RATES OF INFANTS BORN AFTER THE SPRAYING CAMPAIGNS OF 1950 AND 1951

Number Number falciparum Other Month Area Percentage fliau examined positive positive species (%)

1950

June Sprayed 5 0 0 0 0 Unsprayed 3 0 0 0 0

July Sprayed 26 0 0 0 0 Unsprayed 5 0 0 0 0

August Sprayed 65 0 0 0 0 Unsprayed 23 0 0 0 0

September Sprayed 66 0 0 0 0 Unsprayed 23 0 0 0 0

October Sprayed 68 1 a 1.5 0 100

Unsprayed 25 0 0 0 0

November Sprayed 53 0 0 0 0 U nsprayed 23 0 0 0 0

December Sprayed 54 0 0 0 0

Unsprayed 24 0 0 0 0 1951

January Sprayed 65 0 0 0 0 U nsprayed 28 0 0 0 0

February Sprayed 123 0 0 0 0 Unsprayed 50 3 6.0 0 100

March Sprayed 132 0 0 0 0 Unsprayed 60 0 0 0 0

April Sprayed 21 0 0 0 0 Unsprayed 2 0 0 0 0

May Sprayed 27 3 b 11.1 66.7 33.3 U nsprayed 5 0 0 0 0

June Sprayed 30 2 c 6.7 100 0 Unsprayed 12 3 25.0 33.3 66.7

July Sprayed 36 2 b 5.6 100 0 Unsprayed 12 4 33.3 75.0 25.0

August Sprayed 45 d 2.2 100 0 Unsprayed 7 14.3 0 100

September Sprayed 26 0 0 0 0 Unsprayed 6 0 0 0 0

October Sprayed 46 0 0 0 0 Unspraved 10 0 0 0 0

a This infant was 6 months old, and was living in the demonstration area near the boundary with the check area. b These infants were living in the area which was sprayed with 50 mg of DDT per square foot. c These infants were living in the sprayed locality of Veeranur, which is only one furlong (200 m) from the unsprayed locality of Chindaki. d This Infant left the sprayed area and lived for some time in the unsprayed area during the transmission season. 706 L. MARA influencing factors, the general trend of the transmission varies from one point to another in the area as well as from year to year. Broadly speaking, it is possible to identify a well-shaped main transmission peak between May and August, which has the characteristic of being widespread through- out the whole territory and which reappears every year owing to the annual constancy of the south-west monsoon's return. Complementary to, and occasionally interfering with, this main peak, some degree of transmis- sion, variable from year to year, can be found in isolated spots beyond the May-August transmission season. In general these isolated spots are the points where the first signs or the last traces of the main transmission season can be found before or after spreading throughout the entire area. They are also the points where the higher values of endemicity can be currently recorded.

Morbidity The morbidity figures collected by the staff of the team in the 1950-1 project area during the period April-October 1950, and during the corre- sponding period of 1951, are shown below: Malaria cases recorded during the period April-October 1950 Demonstration area Check area Population at risk ...... 52,500 22,500 Fever cases detected ...... 906 1,173 Number positive for malaria parasites . . . . . 58 118 Percentage positive ...... 6.4 10.1 Percentage positive for P. falciparum ...... 52.6 55.0 Percentage positive for other species ...... 48.4 45.0 Malaria cases recorded during the period April-October 1951 Demonstration Check area 1950 Check area area (sprayed 1951) Population at risk ...... 52,500 20,000 2,500 Fever cases detected ...... 265 371 133 Number positive for malaria parasites 29 74 25 Percentage positive ...... 10.9 19.9 18.8 Percentage positive for P. falciparum 68.9 66.3 72.0 Percentage positive for other species 31.1 33.7 28.0 The extent of the successful reduction of malaria morbidity following the spraying operations becomes evident when the analysis of the figures recorded during 1950 and 1951 is carried out on the basis of the total population at risk in the different areas. By using this yardstick it may be realized that, whereas the part of the 1950 check area which was left un- sprayed also during 1951 showed an increased rate of malaria morbidity of 48.0%, the portion which was sprayed during 1951 showed a rate of reduction of 32.6%. On its own side, the demonstration area sprayed MALARIA CONTROL IN SOUTH MALABAR 707

TABLE IV. MORBIDITY FIGURES RECORDED IN THE HOSPITALS AND DISPENSARIES SERVING THE PROJECT AREA

Hospitals and dispensaries Hospitals and dispensaries directly connected with the connected with the entire first year's operational area * project area ** Month general malaria general malaria morbidity morbidity morbidity morbidity 1949 January 4,859 683 11,953 1,328 February 3,799 674 10,680 1,310 March 5,205 957 13,628 1,885 April 5,666 659 12,691 1,320 May 6,558 859 14,139 1,570 June 5,775 1,287 13,682 t 2,022 July 4,714 1,295 12,451 t 2,075 August 4,528 930 11,775 1,608 September 4,133 871 11,492 1,562 October 4,197 788 12,683 1,548 November 4,798 747 13,023 1,467 December 4,796 702 12,361 1,331 Total 59,028 10,452 150,558 19,026 1950 January 4,166 597 12,667 1,246 February 3,257 479 9,961 t 1,092 March 4,107 546 12,183 1,222 April 5,007 564 12,288 1,258 May 6,471 746 15,933 1,523 June 6,133 1,048 14,471 1,813 July 5,230 1,096 13,841 2,011 August 4,401 670 12,195 1,298 September 4,358 797 12,603 1,348 October 4,648 758 12,972 1,434 November 4,768 581 11,583 1,068 December 4,951 471 11,293 847 Total . 57,497 8,353 151,990 16,160 1951 January 4,841 383 11,422 843 February 3,646 364 11,317 963 March 4,397 329 12,403 1,007 April 4,726 424 13,070 1,051 May 6,743 494 15,474 1,069 June 4,819 410 11,849 1,025 July 4,587 420 12,258 992 August 4,173 302 11,558 900 September 3,284 182 10,024 531 October 3,611 180 11,541 659 Total 44,827 3,488 120,916 9,040

*The figures refer to the hospitals and dispensaries of Nilambur, Pullangode, Kalikavu, Kerala Estate, and Mannarghat. ** The figures refer to the hospitals and dispensaries of Palghat, Mundur, Mannarghat, Malapuram, Kerala Estate, Kalikavu, Pullangode, Nilambur, Areacode, Edivanna, Munderi Estate, and Siruvani. t The figures for June and July 1949 and for February 1950 are missing for Munderi Estate. 708 L. MARA in 1950 and in 1951 benefited from a reduction in malaria morbidity as high as 50.0%. These figures also concur with the general feeling of the local population, who acknowledged with much satisfaction the high reduction of fever cases, and match very closely the striking drop in the number of malaria cases treated in hospitals and dispensaries connected with the project area. This reduction is shown in table IV, which gives the monthly general and malaria cases treated during 1949, 1950, and the first ten months of 1951 in the 5 hospitals and dispensaries directly connected with the first year's operational area, and in the 12 hospitals and dispensaries directly serving or somehow connected with the entire two years' operation. From this table it can be calculated that the malaria cases treated in the five hospitals of Nilambur, Pullangode, Kalikavu, Kerala, and Mannarghat during the period January-October 1951 showed a reduction rate of 61.3 % over those treated during the same period in 1949; and that a corresponding reduc- tion of 44.2 % was recorded in the 12 hospitals and dispensaries connected with the entire operational area. Entomologicalfindings Twenty anopheline species were individuated within the team's opera- tional area; namely: A. aconitus, A. aitkeni, A. annularis, A. barbirostris,

GRAPH 3. MONTHLY ANOPHELINE CAPTURES PER MAN-HOUR IN THE FOOTHILLS SECTOR

1951 Sp,oyi,v Eop.-to..o

A = A. fluviatilis (area sprayed in 1950 and 1951) D = other species (area sprayed in 1951) B = other species (area sprayed in 1950 and 1951) E = A. fluviatilis (check area) C = A. fluviatilis (area sprayed in 1951) F = other species (check area) MALARIA CONTROL IN SOUTH MALABAR 709

GRAPH 4. MONTHLY ANOPHELINE CAPTURES PER MAN-HOUR IN THE ATTAPPADI SECTOR

195 J s1A 1951 W-0 203

A = A. fluviatilis (sprayed area) C A. fluviatilis (unsprayed area) B = other species (sprayed area) D other species (unsprayed area)

A. culiciJacies, A. fluviatilis, A. hyrcanus, A. insulaeflorum, A. jamesi, A. jey- poriensis, A. karwari, A. leucosphyrus, A. maculatus, A. pallidus, A. philip- pinensis, A. splendidus, A. subpictus, A. tesselatus, A. vagus, and A. varuna. Among them the prevailing species were A. vagus, A. jeyporiensis, and A. fluviatilis. In terms of general anopheline density, Attappadi represented the leading sector since it showed an average of 12.3 captures per man-hour against 6.7 and 7.2 in the other two sectors; these averages were, for A. flu- viatilis, 10.9, 1.0, and 1.2 captures per man-hour in the Attappadi, foothills, 710 L. MARA

and Arimbra-Uragam Melmuri sectors, respectively. With regard to the place A. fluviatilis occupied among the other species in the different sectors, Attappadi was the only area where this species was strikingly predominant, accounting for more than 86 % of the total anopheline population. In the foothills and Arimbra-Uragam Melmuri areas, the proportion was reversed, A. fluviatilis representing only 17.8 % and 20.4%, respectively, of the local anopheline fauna, and A. jeyporiensis and A. vagus being the predominating species there (see graphs 3 and 4).

GRAPH 5. DISTRIBUTION OF ANOPHELES FLUVIATILIS ADULTS IN CHECK AREAS

IowE I 0 i

C-'l- i a 8 0 ~~~~u 8 I,

05,__ . DISPEltsiom of found -ith Pwconto" premises positive A. fl"iatilis out of th. total prem.ses searched .1*0 4201 The prevalence of A. fluviatilis in Attappadi and the minor place this species occupied among other anophelines in the foothills and Arimbra- Uragam Melmuri sectors is clearly shown in graphs 5 and 6. In these graphs the monthly average captures per house (" concentration ") and the per- centage of houses found positive (" dispersion ") have been expressed diagrammatically, in a way somewhat similar to that followed when drawing the climograms, the abscissa and the ordinate corresponding to the " dispersion " and " concentration " values, respectively, and the Roman numbers to the months to which the figures refer. This way of expressing the results of the captures of the anopheline mosquitos is supplementary to that expressing densities in terms of man-hours. However, in this special instance, it was found that it gave a better indication of the real fluctuation ofthe mosquito population in large areas and during long periods of observa- MALARIA CONTROL IN SOUTH MALABAR 711 tion. In fact, this diagram takes into account both the percentage of the total number of premises visited which was positive with anophelines, and the average density of mosquitos in all the premises which yielded positive captures. It is obvious that this method has the advantage over the man-hours method of making it possible to distinguish between the periods when the increase of the capture is due to the spreading of the species over

GRAPH 6. DISTRIBUTION OF ADULT ANOPHELINE MOSQUITOS OTHER THAN ANOPHELES FLUVIATILIS IN CHECK AREAS

XS X EArmbra -Lk gm MlmuriC sector

@66

0 l0 20 30 40 50 60 70 80 % * DISPERSION E

Aa eootaghillss 1cto

bL10 10 24_b " _ 2

0- 1 0 30 40 5 201._ ~~~~~~~~~~~~~~~~~DISPEtESION 70D

0 _ 8 2

A 2 0 i ' ',9.-O 10 30 n R l DISPlESION - DISPERSION Percentage of premises found positive with anopholint species othw thon A. fluviatilis out of the total premises searched WHO 4202 larger areas (increased positive premises = increased dispersion of the species over the territory), and the periods when the increased captures are merely the result of increased concentration of mosquitos in limited areas, owing to the existence of a favourable local ecology. Moreover, graphs 5 and 6 also show that in Attappadi the A. fluviatilis population had a tendency to increase, starting between June and August, by spreading in a progressive way throughout the entire sector, and reaching its highest numbers between November and December. In the foothills area and in the Arimbra-Uragam Melmuri sector, on the contrary, the increase of the vector population was rather restricted to ecologically favourable areas, A. fluviatilis showing a tendency to appear in more 14 712 L. MARA catching-stations during the period from March to October, and to continue to increase in a smaller number of localities, where higher concentration values were reached, during the last quarter of the year. In these two areas, however, the dispersion of the species never succeeded in reaching the extent of that observed in Attappadi. Twenty-nine A.fluviatilis were found to be infected with malaria parasites (14glands and 15 stomachs) out of5,989 dissected (infectivity rate about 0.5 %); thus, this species can be considered responsible for the malaria transmission in the area (see table V). However, as one specimen infected with very young oocysts was found out of 1,353 A. culicifacies examined, there is a possibility that this species participates in malaria transmission when exceptional conditions favouring the increase of the species density above the current level existing in the area occur. No infection was recorded in the 10,020 mosquitos other than A.fluviatilis and A. culicifacies which were examined during the period of the WHO team's stay in the area. The months during which the infected anophelines were found were March- September inclusive, this infective period thus matching very closely the trend of the parasite-rates among infants. The study of the behaviour of A. fluviatilis throughout the project area shows that, during the daytime, this mosquito prefers to shelter in human dwellings, where it can be found on the inner walls of the rooms resting mainly at a height below six feet (1.8 m) from the floor. In the course of capturing 9,708 A. fluviatilis the following preferential-resting places were recorded

Walls ...... 76.6% Roofs ...... 20.3% Movable and hanging objects not pertaining to the body of the house ...... 3.0%

This species can be found in cattle-sheds from time to time, but this is a very rare occurrence, since the specimens captured there represent only 0.4% of the total captures of A. fluviatihis. This also corresponds to the anthropophilic index shown by this species in the area which reached 65 % out of 243 specimens tested with the precipitin reaction. With regard to the effect of the spraying operations upon the local anopheline population, it can be said that a dramatic fall in the adult mosquito captures followed the DDT campaigns. During 1950, in fact, the A. fluviatilis man-hour captures were 2.1 and the " other species " 7.8 (1,124 hours' search), in the check areas, whereas the figures in the demonstration area were 0.008 and 2.0, respectively (683 hours' search).

f The precipitin tests were carried out at the Istituto di Malariologia " E. Marchiafava ", Rome, by the writer while on leave in Italy. He wishes to acknowledge here his indebtedness to this institute for having kindly supplied him with the needed equipment and reagents. MALARIA CONTROL IN SOUTH MALABAR 713

a, >0( IIIIIIIIlooo oIoooooooI 0 a, I 0 0oo0000000 0 . ooo 0 a)0._ a) -| - n cn -a, a, a,0c 0C .0.- O IC) 00t E Ea) 000o (D co) 0 T t c (0 an 0 C CO - 0 a) m- a,) l l- m (: 00 00 0 o o o0000o 0 D 0._ o E O_ 0 oI o 0 1 (0

0. 040) 0)0 U Q) 00 I-a) .0. N co 0 0- co 0)CO 0D I U-)UI U0t)Ct U) a, Q E E 0) Q C X m ;l:-a a, z > (D II 00 0000000000 0 4 - 00 0 1 00 0000000000 0 Fz'U 2)

0 .A 0 0 N (-O 0 \ 0 0 EE t (0 (O 0 0- z O C)0 co T Cn 'a ._ > ( co I-4c - 000000 00 -0000000 UJ a E E co U, 0 000000 00 -0000000 U, ,na) c: z co UY q 4- 0 z I 0 N 40 041-> 0- 100 r- 0 4O1 0 A. co Lr) c\ t r co CS)t0 C\l - D0N 0) EEE - \ N1- C\J N 0 0) m 0 'IC 0 a,C a) IL 000000000000 0 (I) O ( qC 0 OD ( M ( C\J 0 co C._ 0000ot 000000 4- 0 0 Q. "' M c\ M ; LO M I- Qn co O -1 0O 0 0 0) 04 z-: 0 0) 'N 0 I- 0 (\0 C10 0t 0 O 1r) 00 L1) (. CY) N Nl N Cf) U tJ N\ N\ N\ CY) CO U\DL 10 0 0000000000 a1) U) a, U) 4- -C 0 0 0 0 000LY0 0 'U LO0-m 010(001004 0-m EEE CI 0404040 0) LO 0410 \ 0) c LL. 0 0C\ C)0 0r0U1 O-IIO LU co O\OC'I NtOM M'I M C\O

4( _C 0 L._ .c CY) 0) I- c a, c c o> U

. O 10 (0)0)0 00->1000) U> 040-00 -01 75 40 , o (Uco

> 0 0 0 0 0 -00 11 ,,,z , (E E M _ c E a) ~E, E 0...- C2) c -a)C 0 0L.-3-3< UL 0- ClO 714 L. MARA

TABLE VI. MOSQUITO CAPTURES AND LARVAL COLLECTIONS

Imago collections Month Area man-hour | concentration dispersion

Aa Bb A B A B

1950 January Unsprayed 0.40 5.7 2.3 3.8 4.7 36.2 February C c 0.62 6.8 2.8 4.8 5.2 35.4 Dd 0 0 0 0 0 0

March C 0.39 8.6 3.9 3.8 2.4 55.7 D 0 1.4 0 1.6 0 21.6

April C 1.5 9.2 3.8 4.6 9.6 49.8 D 0 1.1 0 3.0 0 9.5

May C 2.1 5.4 4.4 3.5 12.0 39.0 D 0.009 0.72 1.0 1.9 0.2 9.2

June C 1.4 5.8 3.1 2.1 11.3 68.2 D 0.03 0.43 2.0 2.0 0.9 10.8

July C 1.3 4.7 2.6 2.4 12.8 44.7 D 0 0.95 0 2.4 0 9.8 August C 0.8 4.4 2.1 2.6 9.3 41.5 D 0 0.32 0 1.8 0 4.2

September C 2.8 4.8 5.9 2.9 12.5 41.0 D 0.01 1.1 1.0 2.9 0.28 18.4

October C 2.1 6.1 6.5 3.4 8.2 44.5 D 0 3.1 0 3.7 0 21.0

November C 0.67 8.5 2.7 4.4 6.6 47.5 D 0 3.9 0 3.5 0 28.8

December C 0.68 6.0 5.2 3.9 3.2 38.4 D 0 3.9 0 3.5 0 27.8 1951

January C 0.43 4.5 5.7 3.3 4.1 34.8 D 0 1.5 0 2.4 0 15.3

February C 0.53 3.4 3.9 2.9 3.4 29.2 D 0 1.3 0 1.0 0 17.6

March C 0.76 12.5 5.6 7.0 3.3 44.6 D 0 6.3 0 17.5 0 9.1

April C 2.8 6.3 11.5 4.7 6.3 27.6 D 0 0.02 0 1.0 0 0.06

May C 1.1 3.7 5.2 3.4 5.9 26.4 D 0.02 0.3 2.0 2.0 0.3 4.0

June C 1.7 3.7 3.3 3.1 8.1 29.6 D 0.04 0.48 1.1 1.7 0.9 6.7

July C 1.7 1.8 6.7 4.8 4.0 9.7 D 0.03 2.8 2.0 1.4 0.003 4.7

August C 0.6 1.7 3.5 5.4 4.1 7.8 D 0 0.19 0 1.6 0 2.9

September C 1.1 4.5 8.5 6.4 3.4 17.7 D 0.01 6.3 1.0 1.7 0.49 9.1

October C 1.9 8.3 7.7 7.3 6.3 28.2 D 0 5.5 0 2.2 0 6.0

b B = other species~~~~~~ a A = Anopheles fluviaiilis b B = other species MALARIA CONTROL IN SOUTH MALABAR 715

IN THE FOOTHILLS SECTOR, JANUARY 1950-OCTOBER 1951

Larval collections man-hour concentration dispersion Area Month A B A B A B 1950 3.0 10.0 8.0 6.7 6.2 25.0 Unsprayed January 0 26.0 0 8.6 0 50.0 C c February 0 40.0 0 15.2 0 50.0 Dd 0.87 14.4 3.5 7.3 1.1 32.6 C March 0.05 3.7 1.6 6.3 0.5 10.1 D 0.09 4.9 0.1 4.8 14.0 25.3 C April 0.1 3.1 1.5 4.2 1.9 18.7 D 1.5 15.2 5.3 12.3 6.6 30.8 C May 0.2 6.6 3.4 6.4 7.1 26.1 D 0.04 2.3 1.6 7.0 0.5 8.2 C June 0.05 1.7 3.0 3.5 0.003 8.1 D 0.04 0.53 2.0 1.1 0.4 7.6 C July 0 0.15 0 1.5 0 1.7 D 0.04 0.47 1.2 1.4 0.9 7.5 C August 0 0.43 0 2.4 0 4.4 D 0.01 2.6 1.0 3.6 0.001 12.1 C September 0 2.1 0 3.1 0 10.9 D 1.8 4.9 2.5 4.8 1.2 17.0 C October 0 4.4 0 4.0 0 18.0 D 0.05 8.5 2.5 5.8 0.002 24.2 C November 0 7.4 0 4.0 0 29.1 D 0.09 11.8 3.0 7.3 0.5 26.6 C December 0 8.2 0 4.0 0 34.0 D 1951 0.1 4.7 1.7 3.4 0.9 21.1 C January 0 3.7 0 3.6 0 35.0 D 3.1 3.8 2.0 2.9 2.6 22.6 C February 0 5.6 0 3.5 0 24.2 D 2.4 3.9 1.0 5.2 0.6 18.6 C March 0 22.4 0 8.5 0 48.5 D 1.7 17.6 2.4 14.7 6.3 20.0 C April 0.2 15.0 5.5 10.4 0.9 24.9 D 6.0 14.0 5.9 8.8 13.6 26.6 C May 1.1 14.3 3.0 7.2 6.2 32.6 D 1.3 5.6 3.9 6.3 4.3 14.8 C June 0.58 9.6 3.0 6.4 3.2 24.8 D 0.45 4.6 2.6 6.2 2.8 12.2 C July 3.8 7.9 3.0 5.0 2.1 26.4 D 0.21 5.6 4.6 6.2 0.7 15.0 C August 0.22 7.5 3.0 5.2 1.2 23.2 D 6.7 4.7 4.5 3.9 1.5 20.0 C September 6.0 8.2 2.1 7.3 0.9 18.4 D 0 2.5 0 5.6 0 7.5 C October 0 5.5 0 6.9 0 13.6 D

area d D = demonstration C C = check area d = c C = check area D demonstration area 716 L. MARA

TABLE VIl. MOSQUITO CAPTURES AND LARVAL COLLECTIONS

Imago collections Month Area man-hour concentration dispersion I Aa Bb A B I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~A B 1950 July Unsprayed 3.3 1.4 2.2 0.5 37.9 4.5 August Unsprayed 10.8 0.8 4.3 0.1 62.0 3.0 September U nsprayed 18.1 0.1 6.5 0.1 68.6 0.1 October Unsprayed 21.0 1.8 7.0 0.6 74.4 0.4 November Unsprayed 24.9 0.4 8.0 0.1 77.5 0.9 December Unsprayed 21.6 0.9 6.2 0.2 84.6 2.3

1951 January Unsprayed 9.4 0.1 5.0 0.1 47.0 1.1 February C c 14.6 1.1 4.9 0.2 73.6 2.4 D d 0 0 0 0 0 0 March C 14.2 7.2 5.0 1.7 70.0 9.9 D 0 1.2 0 2.1 0 14.1 April C 15.6 1.4 6.2 0.4 62.3 4.3 D 0.04 2.3 1.0 0.8 1.0 31.3 May C 9.3 4.1 3.5 1.7 65.0 6.7 D 0 6.1 0 1.7 0 8.8 June C 0.70 0.15 1.3 0.1 14.2 2.5 D 0 0 0 0 0 0

July C 1.4 0 2.1 0 16.6 0 D 0.03 0.04 2.0 2.0 0.4 0.5 August C 0.8 0.4 1.3 0.2 11.1 3.7 D 0 0 0 0 0 0 September C 5.0 1.1 2.9 0.3 43.6 2.5 D 0 0.25 0 1.2 0 45.5 October C 5.1 2.0 2.6 0.49 50.0 7.4 D 0 4.3 0 4.4 0 2.3 October 7.4~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

a A = Anopheles fluviatilis b B = other species

During 1951 these values went down further in the demonstration area after the second year's spraying operation (during 294.5 hours' search, A.fluviatilis, 0.006; other species, 0.6), while in the area which acted as control during 1950 and was then sprayed in 1951 (A. fluviatilis 2.1 and other species 7.8), a remarkable drop was recorded with A.fluviatilis coming down to 0.1 per man-hour capture and other species to 1.4 during 389.25 hours' search. The monthly trend of the captures in the sprayed and unsprayed areas in the various sectors of the project is clearly shown in tables VI, VII, and VIII, and in graphs 3 and 4. MALARIA CONTROL IN SOUTH MALABAR 717

IN THE ATTAPPADI SECTOR, JULY 1950-OCTOBER 1951

Larval collections man-hour concentration dispersion Area Month A B A B A B

1950 0.4 0.5 2.5 0.8 3.0 1.5 Unsprayed July 1.8 0.9 2.0 0.6 15.6 1.0 Unsprayed August 0.25 8.5 2.0 5.0 2.0 26.8 Unsprayed September 0.1 5.1 1.5 3.5 1.1 16.1 Unsprayed October 6.4 10.3 7.2 1.4 14.7 18.3 Unsprayed November 6.5 4.4 5.2 1.4 20.5 5.6 Unsprayed December

1951 4.7 4.4 5.0 0.7 15.6 9.0 Unsprayed January 1.1 13.1 1.7 3.3 13.3 33.3 C c February 0 2.7 0 3.8 0 11.6 Dd 2.3 8.1 2.8 3.4 13.1 16.4 C March 0.2 8.6 1.5 4.1 2.3 22.9 D 2.1 22.0 3.6 8.1 10.0 24.0 C April 4.4 1.1 4.2 2.6 17.6 17.4 D 0.5 6.5 1.6 4.7 5.0 13.3 C May 0.29 7.1 2.0 4.5 2.4 16.1 D 0 0 0 0 0 0 C June 0.5 2.6 6.0 0.6 1.2 6.5 D 0 0 0 0 0 0 C July 0.06 2.2 2.0 8.8 0.5 2.9 D 1.6 5.3 2.3 2.9 11.1 11.2 C August 0 1.8 0 3.6 0 8.3 D 0.6 7.0 2.5 3.6 4.2 16.6 C September 0.06 7.8 1.0 5.8 1.0 15.2 D 1.5 6.9 6.7 0.7 5.6 11.1 C October 0.02 5.6 1.0 4.6 0.4 16.3 D

c C = check area d D = demonstration area

It should be mentioned, however, that the dramatic reduction of adult anopheline captures was not followed by a parallel reduction of larval densities in all the areas. It was noticed, in fact, that in several pockets along the foothills line (where the population is very scattered), and in some parts of the Attappadi sector, larvae of A. fluviatilis and other ano- phelines still continued to be captured rather easily even after the spraying operations. This lack of parallelism between the reduction of adult and larval captures in sprayed areas is well illustrated in tables VI, VII, and VIII, which show the monthly average figures of adults and larvae captured in the three sectors of the project area. 718 L. MARA

TABLE VIII. MOSQUITO CAPTURES AND LARVAL COLLECTIONS IN THE ARIMBRA-URAGAM MELMURI SECTOR, OCTOBER 1950-OCTOBER 1951

Imago collections Larval collections concen- Month Area man-hour c°ontcen-tration|B | bdispersionAA B man-hourA |B tration|ondispersion ______~~a__Aap B A B AI B A IB A B

1950

October uc 0.12 8.8 1.5 2.6 2.0 83.5 2.0 7.9 2.5 14.2 14.2 100.0

November U 0.45 8.9 3.7 3.5 2.9 63.5 0.5 10.0 3.5 3.1 2.7 52.1

December U 2.3 9.6 8.4 4.8 6.9 50.0 0.3 7.4 1.5 3.2 4.1 39.0

1951

January U 0.72 9.5 2.9 4.5 6.1 53.3 0 1.5 0 3.5 0 9.2

February U 1.8 3.2 1.5 2.7 3.1 28.9 0 0.1 0 1.0 0 1.6

March U 0.1 18.6 1.5 8.1 2.2 54.0 0 25.9 0 8.5 0 50.7

April C d 0 6.0 0 5.2 0 29.0 0.6 76.5 1.0 21.2 10.0 60.0 0 0 0 0 0 0 0 22.5 0 12.7 0 29.2

May C 0.1 2.6 1.6 2.3 2.0 28.5 3.6 13.6 7.9 13.6 11.1 16.7 D 0 0.09 0 1.4 0 0.01 0.04 16.5 2.0 10.5 0.3,1: 26.2

June C 0.7 3.4 4.0 2.8 4.6 30.0 0.08 5.2 2.0 14.4 0.6 6.0 D 0 0.01 0 2.4 0 1.9 0.17 11.5 2.0 10.2 0.4 18.8

July C 0.7 1.1 2.0 2.0 4.8 9.6 0.3 6.4 3.0 16.0 1.6 6.7 D 0 0.3 0 1.4 0 3.8 0 14.8 0 13.6 0 18.2

August C 0.6 0.6 5.4 5.4 3.1 3.1 0 2.9 0 10.9 0 4.4 D 0 0.06 0 1.0 0 1.5 0.6 3.8 3.9 8.6 2.6 7.5

September C 2.6 4.6 15.6 7.2 4.1 15.9 0.5 3.2 4.0 10.1 2.2 6.5 D 0 0.2 0 2.0 0 3.2 0.3 3.6 2.5 7.5 2.3 8.0

October C 5.8 2.1 3.6 4.1 3.5 13.1 0 0 0 O 0 0 D 0 0.5 0 3.6 0 3.9 0 1.2 0 1.0 0 1.7

a A = Anopheles fluviatilis b B = other species c U = unsprayed d C = check area e D = demonstration area

The presence of an anopheline larval population in some sectors of the sprayed areas was carefully investigated, and it was found that: (a) the larvae found immediately after the end ofthe spraying campaign represented the output of the last adult generations before the latter were eliminated by the toxic action of the residual insecticide ; and (b) when larvae were found to persist or even to increase in several small sectors of treated areas some time after the end of the spraying operation, it was very likely that a foreign factor had been introduced within the sprayed area, and that this factor had exercised its adverse influence on the residual toxic action of the insecticide. MALARIA CONTROL IN SOUTH MALABAR 719

In the first case, it was found that, after a period varying from two to four weeks, the reduction of the larval population followed the disappear- ance of the adults. In the second case, there was not a well-established rule, since several elements, both favourable and adverse to the larval density, were involved. It was realized that certain conditions, such as the building of new houses, the washing or re-surfacing of sprayed walls, and the avail- ability in the area of temporarily built shelters, were all factors which favoured the persistence of a larval population of anophelines, provided that the extent of the new condition introduced into the area concerned was wide enough to match the action of the sprayed surfaces. It is easy to understand, in fact, that a few houses newly built in a densely populated area are to some extent neutralized by the total sprayed surface available in the area itself, whereas a similar number of such houses may play a more important part in a sector where the population is scarce and the total sprayed surface available in the area very small.

Spraying Operation with 50 mg of DDT per Square Foot During 1950 a small sector of the demonstration area was sprayed at the rate of 50 mg of DDT per square foot (0.54 g per m2) in order to assess the effectiveness of such a dosage under the malaria endemic condition existing in Malabar. However, the investigation could not be continued during that year, owing to the fact that the area was wrongly re-sprayed with 200 mg of DDT per square foot (2.2 g per m2) when it was found that some of the houses had been re-surfaced shortly after the end of the main campaign. In 1951, the experiment was repeated in a new sector belonging to the area that had been left unsprayed during the previous year for control purposes. In this new sector, inhabited by a population of 1,250, DDT wettable powder was applied at the rate of 50 mg per square foot in March-April 1951, and the evaluation of the results was carried out by comparing the malario- metric indices recorded during the final survey (October 1951) with those recorded in the same area in October 1950, when the sector had been a part of the check area. As a result of these surveys it was found that there was a reduction in the spleen- and parasite-rates of 43.5 % and 64.5 %, respectively, as a consequence of the DDT operation. But, in spite of this remarkable reduction of the malariometric indices, there was clear evidence that malaria transmission still continued to take place in the 50-mg area, since 4 infants out of 21 were found to have contracted malaria, and some morbidity occurred during the epidemic season following the spraying campaign. In the light of these findings it was therefore justifiable to claim that, although malaria was not eliminated from the area sprayed with this low dosage of DDT, a good reduction in the incidence was achieved. 720 L. MARA

Other Activities Public-health nursing The work of the team's public-health nurse and of her Indian under- studies has been of very valuable assistance in the development of the malaria-control programme. Through a continuous and sound propaganda campaign, which was carried out when local conditions allowed it, these nurses succeeded in explaining the scope of the malaria-control operation to almost all the population living in the areas where the team was operating. A great spirit of co-operation on the part of the local people was thus gained for the team's work, and this was most helpful, especially when the spraying squads had to spray the houses with DDT. The public-health nurse and the two Indian lady health-visitors, besides participating in a direct way in the malaria-control work by collecting the blood smears from infants and fever cases, performed a great deal of maternal and child health work, and developed extensive health-education programmes. These activities were carried out in the field, during the periodic house-to-house visiting in the various areas of the project; in the schools; and in the five clinics which were established by the WHO team within the boundaries of the project, and which were run thanks to the donation of equipment and supplies either from UNICEF or from the Madras Government. The short analysis given below shows very clearly the immense amount of work carried out by the nursing section of the WHO team, and fully justifies the great popularity it gained among the local people:

Skimmed milk distributed . . . . . 440 pounds (200 kg) Malaria treatments given ...... 2,554 Minor ailments treated ...... 15,301 Clinic sessions held ...... 137 Visits paid to schools ...... 268 Visits paid to midwives ...... 310 Blood smears taken from infants . . . 2,840 Health talks given (excluding the lessons given in the schools) ...... 196

Training Besides the training given to the staff posted to the national team by the Madras Government, training was given to two WHO Fellows in Malariology from the South-East Region who spent one and three weeks with the team respectively and were shown all the main aspects of our field work.

Other investigations At the request of the Madras Government a plan for an antifilariasis cam- paign (to be carried out in the coastal town of Calicut, some 45 miles (72 km) MALARIA CONTROL IN SOUTH MALABAR 721 away from the project area) was drawn up in September 1950, and in December 1950 an extensive survey was carried out in the Agency Tracts in the easternmost part of Madras State, in order to investigate the possibility of starting there a new antimalaria project on the same lines as the one already working in Malabar. Moreover, in addition to the routine investigation of the behaviour of the local anopheline, investigations were carried out on the reaction to DDT and BHC of other mosquito species. A large-scale checking of the persis- tence ofDDT in sprayed areas was also carried out by means ofAlessandrini tests. Finally, it should also be mentioned that a rapid survey was carried out in the Ernad area where the team was working, in order to ascertain the prevalence of intestinal worms among the local population. Four hundred and eighty-four samples of stools were examined and an infection rate of from 1.3% to 69.5% for hookworm, and from 16.6% to 66.6% for Ascaris lumbricoides, was found.

Conclusions Before closing this report, it will be useful to recapitulate the main results of the operation carried out by the WHO malaria-control demonstration team in the malarious tracts of South Malabar. It should be remembered, however, when considering these results, that the team was working in these areas for only two years-a very short period. It cannot be said, therefore, that many of the changes recorded can be isolated from the possible effect that other unknown factors or natural causes, varying from one year to another, may have produced. Nevertheless, the parallel observa- tions carried out in the check and demonstration areas seem to speak in favour of the importance of the DDT campaigns. In the light of the data given in this paper it can be inferred that: (a) A slight increase in the birth-rate and a slight decrease in the death- rate was already noticeable in the sprayed areas during the period 1950-1, when the spraying operations against malaria were carried out. (b) After the two years of operation by the WHO team, the size of the endemic area, according to the level of the spleen-rate, was as follows

Spleen-rate Area before 1950 Area by the end of 1951 (%) square miles km' square miles km' Below 10 0 0 102 264 10-19 34 88 37 96 20-49 82 212 119 308 50 and over 199 515 28* 73 * The 29 square miles belonging to the check areas have been excluded. 722 L. MARA

(c) By the end of the demonstration, a rate of overall reduction as high as 56.8% and 78.0% was recorded in the spleen- and parasite-rates, respectively, among children. (d) The infant parasite-rates dropped from 3.3 % to 0% in the areas sprayed twice (during 1950 and 1951), and from 11.3% to 4.0% in the areas sprayed only in 1951. (e) The malaria cases detected by the team's staff during their periodical visiting of the various areas showed a reduction rate of 50.0 % in that part of the project which was sprayed in 1950 and in 1951, and a reduction rate of 24.5 % in that treated during 1951 only. (f) The malaria cases treated by hospitals and dispensaries serving the project area dropped from 9,003 (January-October 1949) to 3,488 (January- October 1951) in the 5 hospitals and dispensaries directly connected with the first year's operational area, and from 16,228 to 9,040 (during the same periods) in the 12 hospitals and dispensaries more or less directly connected with the entire project area. (g) The number of adults of the vector species captured fell to about nil in the sprayed areas, but was not followed by a parallel reduction in the larval captures. However, since the whole operation was successful in controlling malaria, complete elimination of the vector species does not seem to be essential for suppressing the disease. Besides demonstrating the effectiveness of malaria control by a single yearly application of DDT at the rate of 200 mg per square foot (2.2 g per m2) in the malarious areas of South Malabar, the team carried oUt an extensive study of the epidemiological trends in the area and of the biono- mics of the local vector species, and gave valuable training to the Indian staff who were posted to the international team by the Madras Government.

RJ-SUMJ!

L'auteur decrit les experiences faites et les resultats obtenus dans la r6gion sud de la cote de Malabar (Etat de Madras, Inde) au cours des ann&es 1950 et 1951, par une equipe de demonstrations de lutte antipaludique organisee par 1'OMS, le FISE, le Gouvernement de l'Inde et le Gouvernement de l'Etat de Madras. D'apres le recensement effectue par l'equipe, la population de la zone de d6monstrations, forte de quelque 120.000 habitants, est clairsem6e et n'a guere tendance a se grouper. Le mode de transmission du paludisme varie d'une partie de la r6gion a l'autre, en raison des diff6rences physiographiques et meteorologiques annuelles. La courbe de la transmission a son sommet entre mai et aout dans tout le territoire, et comme elle est en rapport avec le retour de la mousson du sud-ouest, elle se repete chaque annee a la meme epoque. En certains points, la trans- mission a ete observ&e avant et apres cette periode. Avant la campagne, le paludisme etait hyperendemique dans une zone representant 63% de la superficie de la region et 25% de la population; il etait mesoendemique dans 37 % de la region, correspondant a 75 % de la population. Dans les zones ou la valeur MALARIA CONTROL IN SOUTH MALABAR 723 de l'indice splenique etait de 50% et plus, la population adulte, lors des poussees epid6- miques, etait affectee dans la meme mesure que les enfants. Dans la region d'Attappadi, on observait une certaine tol6rance des adultes au paludisme. Au cours des campagnes de pulverisation de DDT (a raison de 2,2 g/m2), 52.500 personnes furent protegees en 1950 et 115.500 en 1951; le cofit des operations s'est eleve it US$0,16 par personne. A la suite des pulverisations, on a observe une diminution sensible des zones d'ende- micite, les zones hyperendemiques tendant meme 'a disparaltre et les aires d'hypoende- micit6 se substituant 'a celles de mesoend6micite. Dans l'ensemble du territoire, l'indice splenique a passe de 33,6 i 14,5 (baisse de 57%) et l'indice parasitaire de 4,1 a 0,9 (baisse de 78 %). La diminution du nombre des cas cliniques observes par l'equipe ou soignes dans les dispensaires et hopitaux locaux est all&e de pair avec la baisse des indices. Vingt especes d'anopheles ont 6te identifiees par l'equipe, les principales etant: A. vagus, A. jeyporiensis et A. fluviatilis. Cette derniere espece predominait dans le secteur d'Attappadi, oiu la densite anophelienne 6tait la plus 6lev&e. A la suite de la campagne, le nombre des captures de moustiques adultes est tombe a pres de zero, mais les recherches de larves sont restees fructueuses. Le succes de la campagne semble indiquer que l'eradi- cation de l'espece vectrice n'est donc pas une condition indispensable a l'elimination de la maladie. Parallelement aux travaux de lutte antipaludique, l'equipe a entrepris des recherches sur 1'epidemiologie du paludisme dans la region et sur la biologie des vecteurs. De plus, elle a donne une formation technique au personnel que le Gouvernement de Madras lui avait adjoint.