Abstract
Tsetse control is required in Africa to reduce the incidence of trypanosomiases in man, and domestic animals which provide human food. Control of tsetse has so far been achieved through the use of insecticides but problems of resistance and environmental non-selectivity have stimulated the search for both alternative compounds and biological methods of control. Numerous species of parasites, pathogens and predators are being considered as suitable control agents of tsetse. Research is recommended towards the recognition and use of biological j\gents, their health and environmental safety as well as relevant aspects of tsetse ecology, physiology and behaviour, and mass production. It is recommended that the development of integrated control. (pest management), training programs be treated as a priority.
Resume
11 est necessaire, en Afrique, de !utter contre la tse-tse afin de reduire la frequence de la trypanosomiase tant chez l'homme que chez les animaux domestiques servant a son alimentation. Jusqu'a present, cette lutte a revetu la forme de l'emploi d'insecticides, mais !'apparition de problemes de resistance et leur non-selectivite ecologique ont stimule les recherches en faveur d'atltres composes et de methodes de lutte biologique. 11 semble qu'un grand nombre de parasites, de pathogenes et de predateurs puissent etre des agents efficaces de lutte contre la tse-tse. L'auteur recommande !'orientation des recherches vers !'identification et l'utilisation des agents biologiques, leur securite pour la sante et le milieu, ainsi que vers les aspects connexes de l'ecologie, de la physiologie et du comportement de la tse-tse et de leur production en grand. 11 recom mande egalement que l'on accorde la priorite a la mise au point d'un programme de formation a la pratique de la lutte anti-parasitaire integree.
ISBN: 0-88936-039-1 UDC: 595.77 © 1974 International Development Resear,ch Centre Postal Address: Box 8500, Ottawa, Canada. KlG 3H9 Head Office: 60 Queen St., Ottawa Microfiche Edition $1. IDRC-034e
Tsetse Control: the role of pathogens, parasites and predators
(Report of a Scientific Advisory Group Convened at The Memorial University of Newfoundland, St. John's, Canada, 25-29 March 1974)
This meeting was sponsored by the International Development Research Centre, Ottawa, Canada. The views expressed in this publication are those of the participants and do not necessarily represent the views of the Centre. CONTENTS
Introduction 5
The Problem 6
Current Status of Tsetse Control 7
Tsetse Ecology, Physiology and Behaviour 8
Predators of Glossina 9
Parasites of Glossina 10
Pathogens of Glossina 12
Potentials for Mass Production 13
Research Needs 16
Training Needs 19
Summary 20
List of Participants and Observers 21
INTRODUCTION
A scientific advisory group met at the Memorial University of Newfoundland (MUN), St. John's, Canada, from 25-29 March 1974, to consider the role of pathogens, parasites and predators in future integrated control methodologies for the control of tsetse flies. These vectors, all referable to the genus Glossina and restricted to the "fly-belt" of Africa, transmit sleeping sickness to man and other trypanosomiases to domestic and wild animals. Their consequences to human health and economic development in that continent have been, and remain, incalculable. Seventeen participants including representatives of specialized agencies of the United Nations (the World Health Organization, and the Joint Division of the Food and Agriculture Organization/International Atomic Energy Agency) were invited by the International Development Research Centre (IDRC). There were also three observers from the National Research Council of Canada, the Canadian government Department of Industry, Trade and Commerce, and from industry. This report was prepared for consideration for possible support by funding agencies in order to foster and accelerate research activities. These activities would be designed to improve the capacity to implement such measures of tsetse control as are required to interrupt transmission without posing needless hazards to man and his general environment.
Adult tsetse ( G. palpalis) trapped near Yaounde, Cameroun
5 THE PROBLEM The latter, it should be noted, have some times proved valuable elements in the control of certain insects of economic importance, in Several species of Glossina, each of them which (as in tsetse and other muscoid flies) responsible for distinctive disease problems they are commonly present in nature. This and differing on behavioural and other fact certainly extends the range of candidate grounds from locality to locality, have been biological control agents which can be con the subject of naturalistic control programs sidered for possible field use against tsetse, since the early years of this century. In the by comparison with, for example, mosquitoes years since World War II, synthetic organic from which no insect parasitoids have ever pesticides have generally proved the most been isolated (the small size, brief life-history effective single means of combatting these and aquatic phase of this most important of insects. More than in some other vector all vector groups, presumably militate against borne disease situations, though, tsetse con such parasitization). trol programs have involved what is now adays termed a "pest management" or "inte Through the use of known metho·ds, endo grated control" approach - one calling for parasi tic Diptera and Hymenoptera can be the conjoint use of chemical, biological, mass-produced in the laboratory for field mechanical and other measures, applied release. Verification of the apparent absence against a background of adequate ecological of one whole group of these parasitoids (the understanding of the particular problem un mutillid wasps) from West Africa would cer der attack. tainly make a case for adapting this tech nology to enable introductions of Mutilla Lately, there have been some encouraging spp. into the region from Glossina elsewhere. developments towards more effective and environmentally selective procedures for In contrast to parasitoids, a great deal tsetse control by means of chemical pesti less is known of pathogens of tsetse than of cides. Ther.e have also been advances in such other vectors as mosquitoes and black other aspects of relevant integrated con flies. This may partly reflect behavioural trol procedures. Modern autocidal tech traits predisposing against infection (for niques have attracted ·and are attracting much example, by microsporidan Protozoa, the attention and support in this context. Bio usual route of entry being oral). There has logical control (in the "classical" sense of not yet been a general and intensive search using natural enemies against Glossina) has for pathogens and non-insect parasites of been much talked of, and experimented with tsetse. For example, specific inquiry has occasionally. Also, ther.e is growing recogni doubled the meagre number of mermithid tion of the importance of safeguarding such nematode records from these hosts over the natural regulatory factors bearing upon past ·two or three years. These facts suggest tsetse populations, as predators and insect that a coordinated survey o.f tsetse popula parasites (or parasitoids). tions for viral, ·bacterial, fungal, protozoa!
6 and nematode agents should add materially and therapeutic agents to control trypano to the present obviously inadequate knowl somiasis, and the field availability of these edge of these pathogens and parasites in procedures and substances. Local potentials Glossina. for land management and properly-planned economic programs for the exploitation of Representatives of all the groups of micro agricultural and other natural resources must bial pathogens and nematode parasites just also be taken into consideration. It is noted, named can be mass-cultivated in vivo, and too, that control programs require adequate in vitro methods suitable for industrial ex monitoring and that certain past failures ploitation are already available in some have been due to logistic and economic prob instances and ar.e being explored in others. lems and poor planning rather than to the Applied entomology may therefore be ex techniques employed. pected to contribute practical biological con trol procedures for use together with chemical Tsetse control through the application of and other measures in future integrated tsetse persistent organochlorine. ins,ecticides (no control methodologies. tably DDT) has been achieved in various parts of Africa. Recently, though, widespread problems of resistance and environmental CURRENT STATUS OF TSETSE non-selectivity associated with the employ CONTROL ment of some chemical pesticides for insect control, have stimulated the search for al The meeting of the Joint FAo/wHo Ex ternative compounds. A number of these pert Committee on African Trypanosomiases have already been tested against G lossina in in 1968 reviewed the status of the associated both the laboratory and the field. Synthetic human and domestic animal diseases as well pyrethroids are highly toxic to tsetse when as the known presence of the various Glos used in topical applications. As these com sina species-complexes in the countries con pounds are not residual, they may have cerned. Subsequently, degrees of short-term future use as space sprays. Several organo expansion and/ or contraction of the Glossina phosphates offer good possibilities for use as fly-belts have been observed. However, these either space or residual sprays. All these are difficult to quantify because of the in compounds have low mammalian toxicity. equity in reporting and the sparseness of Most carbamates tested have been only mod regular surveys in certain areas. erately effective against tsetse. The purpose of tsetse control is to reduce The number of new candidate chemical the incidence of trypanosomiases in man, and pesticides for vector control has lessened in in domestic animals which serve as a major recent years. Over the past two years, insec human food source. At the present time, this ticides available for Simulium control in can best be accomplished not on a conti West Africa have been tested for degradabil nental scale but by tsetse control in those ity and effect on non-target organisms, re areas of infection where the highest risk sulting in the rejection of sev,eral compounds. occurs. In each such area, the cost of tsetse The experience gained will be of value in control must be weighed against potential planning subsequent campaigns against riv socio-economic developments as well as erine Glossina in these areas. against the existing disease problems. Inev Advances have recently been made in the itably, the solution will differ in the various development and testing of insecticide appli regions of Africa. cation equipment on fixed-wing aircraft and The cost of development, testing and helicopters, allowing usage of smaller quan application of any new tsetse control agents tities of insecticides, more precisely and must ,be considered against the background effectively placed, to achieve the desired of the improvement of diagnostic techniques levels of control. Tests with ultra low vol-
7 ume application show insecticide penetration The essential behavioural characteristics through forest and woodland canopy, and and the variations of these under the in effectiveness against Glossina. The available fluence of physical and biological factors equipment and insecticides ensure that chem have already been described. At present, there ical control of tsetse, properly applied will are some data for the major species ( G. continue to be effective in areas where hu palpalis, G. f uscipes, G. tachino·ides, G. mor mans are at risk. sitans, G. pallidipes, G. longipalpis, and G. swynnertoni). These concern activity, host Indirect control of tsetse by altering the preferences, feeding grounds, resting places habitat is no longer as widely employed as (diurnal and nocturnal), breeding sites and formerly, and where used, bush clearing is emergence times. generally integrated with the application of insecticides. In recent years, the destruction of Extended observations have identified the wildlife has seldom been practised as a chief elements of Glossina's biological cycle routine control measure. Preliminary results (duration of pupal stage and of the reproduc of studies on the possible use of genetic con tive cycle, insemination rate, frequency of trol of tsetse are promising, and field experi feeding), and of relevant seasonal factors. ments on the use of the sterile male tech nique as part of the campaign against cer The population composition (sex-ratio, tain Glossina are currently being implemen age groups, and various physiological cate ted or prepared in East and West Africa. gories) has been analyzed. A survival curve calculation has •been attempted using a meth od for determining physiological age. TSETSE ECOLOGY, PHYSIOLOGY, fluctuations in the apparent density of AND BEHAVIOUR populations have been observed over periods of several years - for some species, for Tsetse species occupy an area of 10 more than 15 years. These have been related million square kilometres in tropical Africa, to climatic factors and in some circumstances representing one-third of the continent and to biotic ones (e.g. predators, and bovine one-half of its inhabited area. epidemics). Nevertheless, there are still some unknown features. These could be clarified The distribution of the 30 described by taking into consideration density-depen species and sub-species is now quite well dent factors which to date have been little known due .to various surveys which have studied. resulted in the preparation of maps on national, regional and continental scales. Population sampling methods now make it Certain of these maps are revised periodically. possible to establish only relative values. Very The close association of tsetse taxa with low densities are hardly detectable. There well-de.fined types of vegetation, even to have been attempts to evaluate true densities, particular phytocenoses, permits differentia but it is evident that fully satisfactory re tion between riparian, savanna, savanna/ sults must await the availability of a really forest and forest examples. adequate sampling method. Studies of the environment and its action ,Dispersal patterns of .tsetse (linear distri on individuals and populations has enabled bution for riparian species, and wide disper the definition of the ecological requirements sion for savanna species) have been studied, of the main vectors of trypanosomiases and although for a few species only. Throughout development of the concept of permanent their entire life, they live within a very and temporary habitats (not to mention restricted ·area (the "ambit"). Tsetse are not clarification of the ecological consequences "migrant" insects in the ecological sense of of favourable and unfavourable seasons). the word, although they sometimes cover
8 long distances very rapidly. In the dry sea used to attract Glossina to decoys or traps, son, populations are concentrated in favour it would not only improve trapping tech able habitats, which individuals rarely leave. nology but might lead to new control methods. During the rainy season, the flies disperse, With regard to larvae, there are three entering more open country. distinct types of chemoreceptor (possibly Locality learning has not been demon serving as .entry points for pathogens), for strated in Diptera - but the tsetse is an which only a response to humidity has yet unusual fly; it is long-lived, it must find been demonstrated. At least two other be hosts consistently throughout its life, and it havioural responses can thus be predicted, must care for and deposit larvae which rep although their nature remains completely resent an enormous biological investment. It unknown. could be of selective value for the fly to be able to return to frequently used resting places of hosts, such as warthogs, and to PREDATORS OF GLOSSINA good sites for larviposition. The diurnal Many predators from a broad spectrum of activity of preferred hosts may influence its zoological groups prey on immature tsetse population fluctuations. Consequently, an (larvae and especially pupae) as well as the understanding of the adjustment of Plossina adult flies. Among them, some stand apart activity to any reduction in availability of in terms of the frequency of relevant refer preferred hosts is an important ecological ences from widely separated parts of Africa. parameter. Nevertheless, it must be remembered that present knowledge indicates the predatory Knowledge of tsetse ecology has long activities of these animals are generally acci provided a basis for the designing of control dental or seasonal rather than specifically methods effective against the main vectors directed. of human and animal trypanosomiases. The Notable among the predators attacking continuing improvement of research methods tsetse pupae are Hymenoptera (especially and techniques will facilitate further studies Formicidae) and carnivorous Coleoptera. prerequisite to the implementation of prac Diptera (e.g. Asilidae) and spiders deserve tical biological control methods. particular attention because of their occa While our knowledge of pheromones has sional remarkable reduction of adult tsetse rapidly increased in recent years, deeper un populations. derstanding of this topic as regards tsetse Spiders of the family Hersiilidae appear to flies would be very relevant to the develop play a major role in this regard, readily at ment of new approaches to control. Thus tacking Glossina resting on tree trunks and pheromones are of potential application to large branches. The intensity of such preda mass trapping, population assessment, and tion is much greater where climatic condi confusion by disorientation. Analysis of sound tions favour the concentration of predator emission by Glossina and their responses to . and prey species together in the same places. it is also important in this context. Unlike Thus, these conditions have been noted in sight, sound is omni-directional, and perhaps the hot season in the northernmost areas of less subject to hindrance by obvious, natural, the distribution of G. tachinoides. limiting factors (e.g. wind, bush) than are Asilid flies observed as predators of adult olfactory and visual stimuli. Active males tsetse, or considered likely to be such, are and teneral females emit the "alerting" and permanent inhabitants of the range of these "prefeeding'' calls whenever a prospective vectors. Behaving like birds of prey, these host is perceived, thereby announcing to other Diptera capture in flight all insects passing tsetse the fact of their having been attracted. through their field of vision. Asilidae of If this intercommunicating system could be numerous species station themselves close to
9 resting sites where Glossina are in danger of side of the continent). The two species coin being caught as they take flight. cide in Kenya, Tanzania and Malawi. The life cycle lasts from 20-40 days, about 30 Quantitative studies on the effect of these adult parasitoids ,being produced from each two groups of predators have not been pre invaded puparium. At emergence, the male: cise and pose a considerable task. The effects female ratio is about 1 :6. Because of the of predation by hersiilid spiders are undoubt ease with which these little wasps may be edly important, although less evident than bred in captivity in puparia of diverse groups those of the asilids whose prey is more varied of Diptera, some attention has been directed by comparison with those organisms suscep to the possibility of using them in the control tible to capture by spiders. of Glossina populations. Although all invertebrates or vertebrates Field experiments in Malawi and Tan recorded in Jenkins'l compilation must be zania, between 1922 and 1932, indicated considered in field studies of predation upon that no marked increase in the rate of para Glossina, it is urgently necessary to foster sitization of puparia of G. morsitans occurred fresh investigations on all carnivorous arthro after the release of laboratory-bred Syntom pods whose habitats coincide at one time or osphyrum; despite the fact that in the latter another in the year with that of tsetse flies. case, 13,750,000 parasites were released over 14 months. In retrospect, these biological PARASITES OF GLOSSINA control field trials can be criticized on the grounds that too much attention was paid ( 1) ARTHROPOD PARASITES (PARASITOIDS) to the ease with which Syntomosphyrum can Some 33 species of Hymenoptera, repre be bred in captivity, and too little to the fact that rates of natural parasitism above senting 10 families, have been recorded as 3 % have not been recorded. parasitoids of Glossina. Most of them, being but rarely recorded, are probably only facul Three species of Murilla have been re tative parasites of tsetse puparia. N everthe corded from Glossina, and the biology of M. less, the common occurrence of insect para glossinae has been investigated in some de sitoids in Glossina poses biological control tail. Natural rates of parasitism of Glossina possibilities entirely lacking in the major puparia by Murilla can be much higher than group of arthropod disease vectors; for mos those involving Syntomosphyrum, despite a quitoes, presumably through their small size, longer life cycle (2-4 months) and lower generally short life history and the aquatic fecundity (one parasite per puparium). While nature of the immature stages, appear to lack rates of parasitism vary with locality and endoparasitic insect enemies altogether. season, values in excess of 50% have been Among the parasitoids of tsetse, Syntom reported. The male:female ratio on emer osphyrum and Mutilla have been studied in gence is again 1 : 6, the females being apterous. some detail. Some success with breeding M utilla in the The species formerly known as Syntom laboratory has been achieved, although the osphyrum glossinae is now sub-divided into problems of large scale rearing have not been two - S. glossinae (with an east-west dis resolved. Mutillidae are common parasites of tribution across Africa from Senegal to the Glossina in East, East/Central and Southern Indian Ocean) and S. albiclavus (with a Africa; but they have not been recorded from north-south distribution along the eastern Glossina puparia in West Africa. Apart from a single record of a species of 1 Jenkins, D. W. Pathogens, Parasites and Preda Conopidae, all known dipterous parasites of tors of Medically Important Arthropods. Supple· Glossina puparia belong to the Bombyliidae. ment to Vol. 30 of the Bulletin of the World At least 12 species of Thyridanthrax have Health Organization. 1964. been recorded from this group of hosts. Life
10 cycles within the.genus Thyridanthrax (which cases the levels of infestation have been low. is difficult to maintain in the laboratory) Fifteen infestations in 9,000 observations of have not been completely elucidated. The G. fuscipes were reported from Uganda early time spent within the tsetse puparium can in the century. Larvae of Trombidium have vary from about one month to more than been reported on G. palpalis and G. tach eight months. It is likely that some individu inoides in northern Nigeria, and larvae of als go through a larval diapause, perhaps re Erythraeoidea on G. fuscipes from Kenya. lated to season. Only one parasite is produced (3) NEMATODE PARASITES per puparium. Rates of parasitism vary ac Probably, all the nematodes which have cording to locality and season. Exceptionally, been found in tsetse flies can be assigned to rates in excess of 50% occur. Males and the family Mermithidae. Reports of the oc females emerge in approximately equal num currence of these nematodes in tsetse flies bers. Some 10 of the species of Thyridan date back to 1910, when a specimen was re t hrax recorded from tsetse have been found ported from Glossina fuscipes in Uganda. in East and Central Africa, by comparison with only two from West Africa. Since then, there have been a few published records of nematode occurrence. These re Care should be exercised when interpret ports, though, have concerned various species ing published data for percentage parasitism. of tsetse in various African countries. In Some authorities base such values on the per Uganda, two species of tsetse (namely, G. centage of parasites in all puparia collected, fuscipes and G. brevipalpis) have been and others on the incidence of parasitoids shown to harbour nematodes. In Katanga deduced from the total number of parasites (Zaire), Zambia and Tanzania, nematodes and tsetse that emerge. Neither method can have been discovered in specimens of G. give an exact estimate of the percentage of a morsitans. tsetse population that is parasitized. Whereas the second one has the advantage of exclud In West Africa, nematodes have been re ing dead puparia, both have a major draw ported as parasites of G. palpalis in Liberia, back; namely, that as many parasitoids (in Nigeria, and Upper Volta, and of G. mor cluding Mutilla and Thyridanthrax) can re sitans and G. longipalpis in Nigeria. main enclosed within the puparium for much The published records generally indicate longer periods than the developing tsetse fly that the incidence of nematodes as parasites itself, there will always be a bias in favour of of tsetse flies is low. In most cases the reports parasitized whole puparia in any one sample. have been based on the discovery of only a Lack of a prolonged free-living larval stage few nematodes, often after dissection of many and the normally well-protected puparium thousands of tsetse flies. render Glossina relatively free from attack Only in Liberia and Nigeria have the rates by insect parasitoids. In many areas, the in of incidence been rather higher. In the first cidence of parasitism is negligible. However, instance, dissection of 4,000 flies revealed in some areas (e.g. parts of East, Central that fifteen harboured nematodes. All these and Southern Africa) high rates of parasit tsetse were G. P'alpalis. In the second; 43 in ism have been recorded. Under such circum fected flies were found during the course of stances, parasites probably play a part in dissecting approximately 11,000 tsetse. Of regulating the numbers of Glossina. It is con these 43 flies, 38 had originated from a single sidered very possible that the incidence of locality. Two species (G. palpalis and G. natural parasitism might be enhanced by the longipalpis) were present in this locality and introduction of further parasites. both contributed some of the infected speci ( 2) PHORETIC MITES mens. There are only a few records of mites from Opinions differ concerning the effect of Glossina. Their role is unknown, and in all nematode parasitism on the health of the host
11 tsetse. There is little doubt, though, that the the stability of A. repens and its pathoge latter is killed by the departure from it of nicity to invertebrates and vertebrates, includ the fully developed nematode larva, for exit ing man, are therefore indicated. is by means of penetration of the body wall of the host. The resulting hole would allow Fungi found in other dipterans should be leakage of body fluids from the host and examined as possible pathogens of Glossina. also, perhaps, entry of other infective agents. Examples are the entomopathogens of the genus Coelomomyces. Once thought to be The limited amount of information avail restricted to mosquitoes, these are not only able indicates that, in the case of female tse now known from other Nematocera, but C. tse flies, reproductive cycles are not seriously milkoi was recently described from Tab:m affected by the presence of a nematode. idae in the ussR. Parasitic worms found in tsetse have been widely variable in size, up to a maximum of (2) OTHER MICROBIAL PATHOGENS about eleven centimetres. Studies in Nigeria Bacteria, Protozoa, and microsporidan have led to the conclusion that there is no like organisms have occasionally been iso correlation between the age of parasitized lated from tsetse. female G lossina and the size of the contained In 1935, Bacterium mathisi was isolated nematode. However, the possibility must from G. morsitans in Tanzania. The organ always be kept in mind that individual nema ism was easily maintained in culture, and todes vary greatly in both size and rate of proved non-pathogenic to a variety of small development. mammals and to mosquitoes. However, ex While there is no strong evidence relating amples of both G. morsitans and G. palpalis to the ecological site where infection of Glos died within three days of being infected by sina by nematodes takes place, it should be this bacterium. Unfortunately, the original noted that in other hosts, it is usually the im cultures of this bacterium were lost. Efforts matures that are invaded by mermithids. to re-isolate the organism are considered highly desirable.
PATHOGENS OF GLOSSINA More recently, two further bacteria have been reported from G. tachinoides puparia. (1) FUNGAL PATHOGENS Also, Treponema glossinae has been described from the gut of G. palpalis, and similar or Fungal infections of Glossina were first ganisms have been found in G. brevipalis. noted many years ago, but cultures of these strains were not maintained. The organisms Haemogregarines have been obtained from were reported as belonging to the genus Cic specimens of G. palpalis originating from adomyces (from G. morsitans and G. pal various areas, including Senegal and Ghana palis) and the Phycomycetes group (from (crocodiles are the vertebrate hosts of the G. morsitans). Their pathogenic effects were tsetse-borne Hepatozaon pettiti). not elucidated. While rates of infection were Myxosporidium heibergi is an organism of sometimes recorded, this information is of uncertain standing, described nearly 70 years little use in the absence of valid identification ago. It is mentioned here as it is the only par of the fungi. asite possibly referable to the protozoan order More recently, Absidia repens and Pen Microsporida yet recorded from tsetse. The icillium lilacinum have been reported from interest of this lies in the fact that micro Glossina. Mortality of puparia in nature has sporidans are currently considered as candi been attributed to A. re pens. However, re date biological control agents for eventual lated fungi (A. ramosa and A. corymbifera) use against mosquitoes and blackflies, in are vertebrate pathogens. Thorough studies of both of which groups they occur commonly.
12 Among the above organi~m~. only Bac t rc:11) .md Africa ( N:1irobi, K:lllun;1, T:ing.1. terium 11wrhisi h:1s been clc:1 rly ~1s~oci:1tcd Bol'w-Dioulasso) brccLI snH1llcr number!. of with bosl mort:ility. lsctsc. Ccrlain of lhe!>e, 1hm1gh ( p;irticulurly Alric:111 ones) arc plunning early increase\ There :ire no puhlishcd acCl"lunt~ of cntomo in their oulput. pathogcnic viru~cs isol;itcd from Glu.fsitw. Their close as~oeiation with other group~ of All cxis1ing colonic' 11\c li,ing an1111.1b Diptcrn suggc~ts that they might '.'Cl! be found (r.thbil~. goats, guinc.1-pigo;) for bloo~I me.1b. once l.e.m:hcJ for. In thil> contcxl, very re However, progrc!>s is being moillc toward~ lhc cent work has rcv1rnled virus-like p:ir1iclcs in fcei..ling of Glossirw thrnugh artifici
• Jnstitut d'Elcvage ct de MCJecinc V~1Crinaire des Par' Tropicaux While the low reproductive rate of tsetse field. For this, the numbers required for flies curtails their mass-production, the main adequate introductions into a number of rearing laboratories in Europe can (without ecologically different areas, and at different reducing the size of their colonies) divert seasons, would necessarily be large. To pro more than half the production to other uses. duce Glossina puparia in the required num Thus, both Langford and Maisons-Alfort are bers would be difficult, and certainly very able to make available over 100,000 puparia expensive. per year. It would thus be preferable, in connection ( 2) p ARASITOIDS with all such parasitoid breeding, to develop One of the advantages of this aspect of methods based upon the use of alternative biological control of Glossina is that many hosts (e.g. Sarcophaga, Chrysomyia, Lucilia, of their insect parasites (parasitoids) are Musca). Representatives of these genera are already known and identified. Moreover, for easily produced in any numbers required, several of the more common species, their either on inexpensive naturally-occurring general distribution is known and their life substances, or on artificial diets. The basic cycles are understood. In a few instances, facilities for small initial production exist at there is some knowledge of methods of breed crnc stations. They could be expanded very ing based upon experience with actual easily, as and when required. parasitoids of tsetse, and there is wider The necessary numbers of the different experience from parallel work in economic parasitoids in question would vary with such entomology to be drawn upon. factors as their biological characteristics, the Therefore, there are certainly possibilities number and diversity of sites for field libera for breeding a number of these parasitoids tions, the manner of use (e.g. inoculative, which could be exploited with little delay, inundative). The last-mentioned point is of using currently available facilities in both prime importance. Simple inoculative re Africa and Europe. Glossina breeding units leases into small selected areas require few could be utilized, for example. Various parasitoids (several hundred on each occasion, African stations could become sources of with perhaps 20 releases at each introduction Glossina parasitoids for mass production site over a year, or concentrated within the units elsewhere, and Commonwealth Institute most favourable seasons). The required num of Biological Control ( crnc) stations could bers of parasitoids would be small enough cooperate in the development of rearing tech for production in Glossina puparia at present niques up to the level required. supply levels, if alternative hosts could not be found. Similar releases over wider regions It must be borne in mind, too, that a less densely populated by Glossina (e.g. number of parasitoids are known from other savannas) would require far greater numbers Diptera, particularly muscoid flies elsewhere of parasitoids, the production of which would than in Africa. One or more of these, if be impractical with Glossina puparia as hosts artificially established there, might possibly (failing radical advances in production tech become important parasites of Glossina in nology). Inundative releases designed to sup some areas. Relevant laboratory experimen press Glossina numbers following each r,e tation and field trials are necessary. Prelim lease, rather than to lead to permanent estab inary exploration of this field would require lishment of the parasitoids in the new locality, the availability of limited quantities (of the would have to be repeated periodically. Such order of hundreds a week) of puparia rep an approach would require extremely large resenting a range of tsetse species. numbers of parasitoids and hence of hosts. The ultimate aim of any such work is Therefore, it is less practical than the previous to make liberations of parasitoids in the two methods.
14 Actual breeding techniques and output ii) mermi.thids may infect approxi- would naturally vary from one parasitoid mately 1 % of the adult flies. species to ·another. Among the parasitoids of It is not known if larvae and puparia are Glossina, the mutillids and bombyliids should infected, or whether significant mortality be the first groups to be tackled; in full really does occur. A detailed discussion per realization that the latter would prove diffi taining to the mass-cultivation of tsetse mer cult to breed, and that the operation might mithids would therefore be premature, since not be feasible outside of Africa. At least their potential impact on the host populations three known species of mutillids and at least has not been established. ten bombyliids are available for consideration, and there are a number of other parasitoids (4) MICROBIAL PATHOGENS (chalcidoids, etc.. ) that should certainly be looked into as well. Superficially, it could be argued that the tsetse fly is not an ideal candidate for micro On the basis of present knowledge, a bial control. After all; dozen parasitoids from other hosts are avail able fo~ testing against Glossina. The relevant i) s.everal species of Glossina are impor breeding techniques have already been devel tant vectors and must be controlled with the oped, and material is readily available for means now available; laboratory and field trials against tsetse. It is confidently predicted that investigation will ii) the insects have widely varying distri rapidly produce a substantially wider range butions and behaviour patterns; of candidates. Preliminary trials could indeed iii) their developmental stages have yielded be undertaken prior .to the development of few microbial pathogens and might be con suitable mass-breeding techniques, the work sidered as unusually unavailable to such being centred upon existing facilities having organisms. the necessary expertise and near to existing sources of Glossina puparia (e.g. crnc sta On the other hand, it is self-evident that tions - the station at Delemont, Switzerland, success in tsetse control by means of micro has the required staff and facilities, and bial control agents depends upon a number could - via short and reliable air links - of factors - and, notably, upon the produc very easily obtain material from Maisons tion and distribution of these organisms in Alfort, Langford, Anvers, and Vienna). adequate quantities. Past experience with insects other than (3) NEMATODE PARASITES tsetse has indicated that multiple or periodic There is no current capability for mass introductions of micro-organisms are the rule producing mermithid nematode parasites of rather than the .exception in ensuring the tsetse. As yet, too, the necessary preliminary continuation of desired levels of control. field and laboratory studies remain to be Means for the mass production of microbial undertaken. Not one species of mermithid pathogens of tsetse are therefore prerequisite has yet been described from tsetse flies. to the attainment of meaningful degrees of Indeed, it cannot yet be stated with certainty tsetse suppression. that more than one mermithid species is involved. Host-parasite relationships require Although in vivo and in vitro techniques exploration as well. All of our relevant are now being successfully employed in the knowledge may be summed up in the obser production of insect microbials, the latter is vations that; preferred as it opens the way to adequate regulation of product standardization. i) several species of tsetse from a wide geographical swathe of Africa harbour mer Assuming that some form of culture can mithids; be realized for the production of candidate
15 microbials for tsetse control, the following PATHOLOGIES, PATHOGENS, PARASITES AND points need careful consideration in explor PREDATORS OF GLOSS/NA ing the potential for mass production: (a) Inventories of biological agents and i) costs, including both operational costs non-infectious pathologies3 affecting the suc and capital investment; cess of Glossina in specific localities should be implemented without further delay. The ii) the amounts of microbial needed and objectives for such inventories would be: the frequency of production; i) to establish basic information on the iii) product purity; distribution of biological agents and non iv) product virulence; infectious pathologies in advance of ma nipulation of indigenous biological agents v) product - including formulation - sta or introduction of exotic ones; bility; ii) to detect the existence of potential vi) production location; and agents for biological control, and the inci vii) method of distribution. dence of non-infectious pathologies, for example, genetically-determined reproduc Few, if any, immediate research concerns tive anomalies; impede the development of mass-cultivation techniques toward tsetse control. The most iii) to elucidate infectious and non-in obvious potential candidates (i.e. microbial fectious causes of abortion in tsetse. agents with high virulence to several species (b) Existing studies of the widest possible of Glossina, notably Bacterium mathisi and range of individual biological control agents fungi of the genus Absidia) have already merit acceleration, and new ventures in this been cultured in vitro. Once one of these field should be fostered and adequately sup pathogens (or another such candidate for ported. These studies should include: tsetse control) has been characterized suffi ciently for full appreciation of its potential i) research within Africa toward the as a significant control agent, it will be pos adequate characterization of such orga sible to increase production toward mass nisms, with further attention to their nat cultivation. ural habitat, host preferences, behaviour, development, distribution, and the construe-
RESEARCH NEEDS 'An existing global inventory system for biolog ical agents affecting vector species is operated Research toward the recognition and use by the World Health Organization through the of candidate biological agents for develop International Reference Centre for the Diagnosis ment of addition al control methods against of Diseases of Vectors, at the Ohio State Univer G lossina, is recommended in four categories: sity, Columbus, Ohio, U.S.A. For this Centre's purposes, the term "diseases" embraces patho ( 1) pathologies, pathogens, parasites and gens, parasites, predators and non-infectious predators of Glossina; diseases. The Centre has been largely concerned (2) relevant aspects of tsetse ecology, phys with the isolation of pathogens and parasites of iology and behaviour; the mosquito vectors of malaria, yellow fever, and other human diseases to date. Such a Centre (3) revelant aspec.ts of mass production; might conceivably play a role in a network or and program related to the recommendation cited above in implementation of an inventory of bio ( 4) health and environmental safety of bi logical agents associated with Glossina and of ological control agents. potential value for biological control.
16 tion of relevant life-tables (from the results groups harming all stages of Glossina (which of this work, priorities could be established also, however, have been reported at times for trial inoculative introductions of candi to suffer from bacterial attack). The detec date biological control agents from one tion of pathogens (and mutualistic symbionts) region of Africa to another, and/ or their associated with tsetse must of course provide propagation in very large amounts for in for systematic examination of the various life undative field releases); history stages (with particular attention to immature forms) in both field and labora ii) a comprehensive review of parasites tory. The provision of tentative identifica and pathogens of muscoid flies from else tions and the referring of pathogens to spe where than Africa should be directed to cialists should be the responsibility of an en wards exposure of the puparia of various larged network of laboratories serving for species of Glossina to a variety of candi mally in an inventory system. date agents, in the interests of selecting particularly promising organisms for trial The examination, characterization and against Glossina - first under simulated identification of candidate biological control field conditions wherever facilities were agents, and the screening of pathogens, once available, but eventually through actual isolated, should be pursued by specialists pilot projects in Africa; (e.g. virologists, bacteriologists, protozoolo gists) collaborating with public health and iii) further studies of short-listed candi veterinary entomologists handling tsetse in date parasitoids brought to light under i) the laboratory and field. and ii) above, towards their propagation in very large quantities - such studies to Furthermore, the isolation of particularly involve alternate hosts in place of actual promising strains of identified pathogens; tsetse flies wherever desirable, and to be the development of methods for the formula scaled up to a fully operational level either tion of materials to be used in pilot programs in Africa or elsewhere, as dictated by cir and eventual field applications; together with cumstance; and proper monitoring of effectiv.eness and safety; must be the result of collaboration iv) the building up of a panel of col between entomologists specializing in tsetse laborating specialists with the requisite problems, biological control workers, inverte skills for taxonomic identification of non brate pathologists and mass production ex target invertebrates associated with Glos perts. Also, there must be continuing sina, and of those predacious organisms liaison between representatives of all inter (vertebrates as well as invertebrates) rec ested groups from the governmental, univer ognized to affect Glossina; and the co sity and industrial sectors, and at both ordination of these experts' services with national and international levels. in the context of this report. Where invertebrate pathogens already in ( c) Viewed as no less promising than the use and commercially available are known invertebrate parasites affecting Glossina (e.g. to affect Diptera, their effects on Glossina parasitoid Hymenoptera, Diptera) and these should be ascertained. It is also specifically insects' invertebrate and vertebrate preda recommended that such studies be conducted tors (e.g. spiders, rodents) are the non-insect with respect to the activity of already parasites such as mermithid nematodes, and isolated and available metabolic products the microbial pathogens (viruses, bacteria, resulting from the fermentation-production of fungi, protozoa, and possibly the rickettsiae) . strains of Bacillus thuringiensis (a pathogen According to published reports, the nema now widely-employed for the manufacture of todes and fungi appear to be the predominant first-generation "microbial pesticides").
17 RELEVANT ASPECTS OF TSETSE ECOLOGY, v1s10n (pattern, colour movement); PHYSIOLOGY AND BEHAVIOUR hearing (communication); All behavioural activities which will help chemoreception (attraction, re in predicting the location of tsetse puparia pellence, resting, larviposition) ; and adults are germane to biological control mechanoreception (resting, larvi research. Through such studies, methods will position). be devised for attracting tsetse to locations where adults or immature forms can be infected with parasites or pathogens. The RELEVANT ASPECTS OF MASS PRODUCTION emphasis in such investigations should be There is a need for improved mass-produc ethological, pertinent observation and experi tion technology to ensure the availability for ment being combined in both the laboratory field application of adequate amounts and and nature. Subjects for investigation under continuing supplies of selected insect and this heading should include: other parasites, and pathogens, of Glossina. Pertinent field application procedures will i) factors determining selection of larvi require attention too. Improved mass-produc position sites by pregnant tsetse; tion capabilities within Africa itself are ii) factors determining selection of rest viewed as fundamental to the above require ing sites by males and females at various ments; as are further diversification of the stages of their activity and reproductive number of tsetse species being reared in the cycles; laboratory (with special reference to forest species of economic importance), and the iii) the isolation and testing of poten early perfection of artificial feeding methods. tial attractants from host animals; It is also recommended that whenever iv) the basis of interspecific and inter pathogenic microorganisms accidentally ap generic communication; pear in tsetse colonies, the obvious urgency v) distribution of adults in the field (Is of correcting the problem should not be an distribution random in both sexes? Do excuse for neglecting the opportunity for females return to larviposit at the same isolating, identifying and evaluating what site as used previously?); might prove to be additional candidate bio vi) the development of adequate tech logical control agents. niques (e.g. reliable procedures permitting the accurate estimation of low densities of HEALTH AND ENVIRONMENTAL SAFETY OF tsetse) for sampling Glossina populations BIOLOGICAL CONTROL AGENTS (studies of tsetse population composition All candidate biological agents being con by age group: determination of the popu sidered for tsetse control must be assessed lation structure in relation to research on from the standpoint of their safety to non the effects of the introduction of sterile target organisms. males, natural enemies and diseases among Glossina adult populations and assemblages The evaluation of e.g. microbial control of larval and pupal forms); agents has centred upon their manipulation as active ingredients in formulated prepara vii) elucidation of life-tables to detect tions for area application or inoculative in and rank the mortality factors for Glossina; troductions. At the same time, there has been and increasing recognition of the need to follow viii) improved understanding of the sound quarantine practice and to ensure the sensory mechanisms of adults and imma safe practice of operational biological con tures, towards the prediction of orienta trol procedures. It cannot be too strongly tion behaviour patterns, notably studies of: emphasized that the use of microorganisms
18 for tsetse control must be evolved in accor organisms under operational conditions. The dance with an orderly sequence. At each step, possible effects on man must also be consi research and assessment are necessary to dered in a presumptive sense when reviewing furnish the proper safeguards covering the the status of a pathogen in advance of proposed use. Thus, following the detection, limited use. isolation, and characterization of a promis The totality of safety of entomopathogens ing pathogen, the active principle must be and related research needs, thus rests on identified and an original isolate must be three issues: maintained as a reference culture. In order to assure the capability to control or destroy (i) the identification of the active prin a microbial pathogen, in case a dangerous ciple; situation should occur despite careful safety testing, there must be prior knowledge of (ii) vertebrate and invertebrate infec tivity studies emphasizing why a pathogen appropriate anti-microbial agents. affecting an invertebrate is non-pathogenic A further stage towards the assessment of for vertebrates; and hazards involves investigation of the possi (iii) studies of short-term and long bilities .of mammalian, and general verte term consequences to the environment. brate and invertebrate, response to the pathogen. This phase can be divided into empirical studies, the testing of selected verte brate and invertebrate species, and basic re TRAINING NEEDS search designed to elucidate the reasons for apparent non-infectivity of insect pathogens This section of the report refers to training to vertebrates. On reaching this point in the needs for both professional and expert tech development of candidate microbial control nical personnel. agents, the results should be reviewed by an Some problems of the present situation m impartial panel of experts, charged by the Africa are: responsible agency with recommending whether or not a limited field use of the ( 1) scientists working with the tsetse candidate is acceptable. Such limited use problem are seldom trained in the should be designed to serve two purposes: theory and practice of integrated con firstly, to gather data on the pathogen's ef trol (pest management), and many of fectiveness; and secondly, to obtain data on them are self-taught in vector control; its short-term environmental consequences, if (2) information on educational opportuni any. ties potentially available to those con Provision should be made at this point cerned does not always reach their for the detection of any long-term conse level; quences of field applications of pathogens, (3) in some research centres indigenous if findings from limited use suggest such an personnel are still a minority among eventuality. Results of the laboratory and the scientific staff; and limited-use field studies would of course be basic to any decision on the approval of ( 4) there is often inadequate communica relevant applications concerning operational tion between tsetse research centres in field use. different countries, especially between the francophone and anglophone states. The monitoring of any human effects of exposure to entomopathogens demands pro Integrated control (pest management) pro grams specifically devised for persons occu grams are given at some universities m pationally or incidentally exposed to such North America (in Canada, the Master of
19 Pest Management - MPM - program at Simon pation in them of students and scien Fraser University, British Columbia). The tists from all relevant countries; and development of a similar program oriented ( 6) that communications dealing with the towards tropical integrated control (pest man availability of all such educational op agement) would be most timely. There is an portunities be improved (e.g. via the urgent requirement for short-term intensive Liaison Officer of the International courses in practical management of specific Scientific Council for Trypanosomiasis kinds of pests and vectors (including tsetse). Research and Control at Nairobi, Such courses should include techniques for Kenya). survey, rearing, etc., given by experts in the field, in Africa. Finally, it is desirable to en courage African students and scientists to take integrated control (pest management) SUMMARY training, and for the relevant administrations to facilitate their doing so. Measures against pests and vectors in fu ture will clearly involve the increasing ap RECOMMENDATIONS: plication of integrated control (pest manage ( 1) that scientists working or planning to ment) approaches. Equally clearly, biological work on the tsetse problem in Africa control will comprise an essential component be encouraged and financed to take of integrated methodologies used against training in integrated control (pest tsetse, as against other harmful insects. There management) where it is now available, fore, funding agencies interested in early and that steps be initated to set up a solutions to the pressing problem of the major integrated control (pest manage African trypanosomiases would do well to ment) training centre oriented towards give the most serious consideration to sup tropical problems at an appropriate porting relevant research as detailed in this location, perhaps with initial guidance report. and cooperation from the faculty of an existing centre in North America; As indicated, there are inequalities in our present understanding of the different fields (2) that a system be organized to provide that will contribute towards eventual biolog short-term (two weeks to two months) ical control methods for use against Glos integrated control (pest management) sina. It would be presumptuous at this early courses in the field, in Africa; stage to attempt the identification of an ex-. ( 3) that for reasons of language and geo tended list of research and training priorities; graphy such courses be organized in a few of which will nevertheless be cited, different parts of Africa in different purely as examples. years; The first three are self-evidently prere ( 4) that the instruction be given by ex quisite to many other needs individually in perts on the various aspects of inte dicated in the report; to inventory and grated control (pest management) of characterize pathologies, pathogens and para which scientists of the crnc represent sites of tsetse through the promotion of colla one of a number of potentially-avail boration within a network of suitably-equip able groups, and that these provide ped and staffed research laboratories; by a re.fresher courses for working scien similar approach, to facilitate the identifica tists as well as training for students en tion of other organisms associated with tering the profession; G/ossina (particularly predatory invertebrates) ( 5) that financial support be provided for through fostering the provision of skilled the above programs and for the partici- systematic advice; and to further integrated
20 control (pest management) training courses is emphasized that confirmation of the ap for African students and scientists concerned parent absence of mutillid wasp parasitoids with tsetse control. from West African Glossina would open the way to early westward field introductions of Finally, because of the relatively advanced already-known species of M utilla from else state of knowledge of this particular issue, it where in the continent.
LIST OF PARTICIPANTS AND OBSERVERS
Dr. A. A. Arata Dr. J. P. Eouzan Vector Biology and Control ORSTOM Centre de Yaounde World Health Organization B. P. 193 1211 Geneva 27 Yaounde Switzerland Republique Federale du Cameroun
Dr. B. P. Beirne Dr. D. C. E. Ferguson Director, Pestology Centre Associate Director Department of Biological Sciences Population and Health Sciences Simon Fraser University International Development Research Centre Burnaby 2, British Columbia P.O. Box 8500 Ottawa, Ontario KlG 3H9 Dr. John D. Briggs Head, WHO International Reference Centre for Diagnosis of Diseases of Vectors Dr. L. H. Finlayson Department of Entomology Dept. of Zoology and Comparative Physiology The Ohio State University University of Birmingham Columbus, Ohio 43210, U.S.A. P.O. Box 363 Birmingham B15 2TI Dr. A. Challier England Entomologiste medical Mission Entomologique ORSTOM aupres de l'occoE Dr. J. Gruvel B. P. 171 Laboratoir.e de Farcha Bobo-Dioulasso, Haute-Volta B. P. 433 N'Djamena, Tchad (Rapporteur) Dr. Reto Engler Dr. J. Itard Toxicology Branch lnstitut d'Elevage de Medecine Veterinaire Registration Division des Pays Tropicaux Environmental Protection Agency 10, rue Pierre Curie 94 Washington, D.C. 20460, U.S.A. Maisons-Alfort, France
21 (Chairman) (Vice Chairman) Dr. A. M. Jordan Dr. s. M. Toure Tsetse Research Laboratory Laboratoire National de l'Elevage University of Bristol et de Recherches Veterinaires Langford House B. P. 2057 Langford, Bristol BS18 7DU Dakar-Hann, Senegal England Dr. H. Wetzel Dr. J. Losos Insect and Pest Control Section Program Officer International Atomic Energy Agency Population and Health Sciences Karntner Ring 11 International Development Research Centre P.O. Box 590 P.O. Box 8500 A-1011 Vienna Ottawa, Ontario KlG 3H9 Austria
Dr. R. F. Myers Research Unit on Vector Pathology OBSERVERS Memorial University of Newfoundland Mr. Dale Blair St. John's, Newfoundland, AlC 5S7 Dept. of Industry, Trade & Commerce Government of Canada Dr. R. A. Nolan 210 Water Street Department of Biology St. John's, Newfoundland AlC 1A9 Memorial University o.f Newfoundland St. John's, Newfoundland AlC 5S7 Dr. E. G. Gemrich II Insecticides and Fungicides Dr. S. N. Okiwelu Agricultural Division National Council for Scientific Research The Upjohn Company P.O. Box 49 Kalamazoo, Michigan 49001 Chilanga, Lusaka U.S.A. Zambia Dr. William A. Turnock Mr. Kevin Riordan Head of Ecology & Population Dynamics Principal Research Officer (Entomology) Integrated Pest Control Nigerian Insitute for Trypanosomiasis Winnipeg Research Station Research Canada Agriculture P.M.B. 2077 25 Dafoe Road Kaduna, North Central State Winnipeg, Manitoba R3T 2MP Nig.eria
Dr. F. J. Simmonds Director, Commonwealth Institute of SCIENTIFIC SECRETARY Biological Control Dr. Marshall Laird Gordon Street Director, Research Unit on Vector Pathology Curepe, Trinidad Memorial University of Newfoundland West Indies St. John's, Newfoundland AlC 5S7
22 Credits
Cover design: Opaque Graphics, Ottawa
Photographs: Marshall Laird IDRC MODQgr8phs
IDRC-OlOe Chronic cassava toxicity: proceedings of an interdisciplinary workshop. London, England, 29-30 January 1973. Barry Nestel and Reginal Macintyre (ed.), 162 pp., 1973. IDRC-012e Three strands of rope, Clyde Sanger. 24 p., 1973. IDRC-013e The first 100 projects. 29 p., July 1973. IDRC-013f Les 100 premiers projets. 30 p., juillet 1973. IDRC-014e Research policy: eleven issues: outline statement to the Board of Gov ernors of the International Development Research Centre at their meeting in Bogota, Colombia, March 19, 1973, W. David Hopper. 16 p., 1973. IDRC-014f La recherche pour le developpement: onze principes fondamentaux: re capitulation des principes fondamentaux gouvernant !es activites du Centre. Discours prononce le 19 mars 1973, devant le Conseil des Gouverneurs reuni en Assemblee a Bogota (Colombie), W. David Hopper. 21 p., 1973. IDRC-015e Aquaculture in Southeast Asia: report on a seminar at the Freshwater Fishery Research Station, Malacca, West Malaysia, 17-25 April 1973. 22 p., 1973. IDRC-016e Consumer food utilization in the semi-arid tropics of Africa: report of an interdisciplinary workshop, Zaria, Nigeria, 30 April-4 May 1973. 16 p., 1973. IDRC-017f Durabilite naturelle et preservation de cent bois tropicaux africains, Yves Fortin et Jean Poliquin. 143 p., 1974. IDRC-018f Education sexuelie en Afrique tropical. 124 p., 1973. IDRC-019s Administracion Universitaria; Aspectos fundamentales sobre Ia admin istracion academica universitaria, Henrique Tono T. 25 p., 1973. IDRC-020e Cassava utilization and potential markets, Truman P. Phillips. 184 p., 1974. IDRC-021e Nutritive value of triticale protein, Joseph, H. Hulse and Evangeline M. Laing. 183 p., 1974. IDRC022e Consumer preference study in grain utilization, Maiduguri, Nigeria, Jean Steckle and Linda Ewanyk. 47 p., 1974, IDRC-023e Directory of food science and technology in Southeast Asia. 194 p., 1974. IDRC-025e, f, s AGRIS and the developing countries: recommendations of the FAO/ IDRC meeting held in Rome, 26-28 September 1973; AGRIS et !es pays en voie de developpement: recommandations de Ia reunion FAO/CRDI qui s'est tenue a Rome du 26 au 28 septembre 1973; AGRIS y los paises en desarrollo: recom mendaciones de la reunion de! FAO/CIID celebrada en Roma de! 26 al 28 de Septiembre de 1973. 35 p., 1974. 1DRC-026e Food crop research for the semi-arid tropics: report of a workshop on the physiology and biochemistry of drought resistance and its application to breeding productive plant varieties: University of Saskatchewan, Saskatoon, Canada, 22-24 March 1973, Michael Brandreth. 16 p., 1974. IDRC-027e .Technology policy study centres in Africa: report on the IDRC/ECA meeting on the creation of centres for technology policy studies in Africa, Ile-Ife, Nigeria, 5-10 December 1973. 35 p., 1974. IDRC-028e Rural water supply and sanitation in less-developed countries: a selected annotated bibliography, Anne U. White and Chris Seviour. 84 p., 1974. IDRC-029e International Development Research Centre, programs in agriculture, fisheries, forestry and food science: reviewed at a symposium, Ottawa, 12 Sep tember 1973. 55 p., 1974.