Mission Entomologique 0.R .S .T .O .&5 o aupres de 1 O .C .C .G .E Biology and Control of Tsetse Flies (1) JeHamon , A,Challier , J.Mouchet & J,Rageau --h--------------------,-------------------------------------------~ (1) Ce document est bas4 sur un cours fait lors du S6minaire 0.T'tPn.S. .inter+r6gional sur les m6thudes entomologiques de contrble des vecteurs qui a eu lieu en U.R.S.S. en Septembre-Octobre 1965 I1 est diffus6 car il pourrait être utile aux entomologistes devant faire des cours sur les glossines dans les pays d'af- fectation . IC1 conviendrait alors de compl6ter la bibliogra- phie ' nQ Ia 8)iology and Control of Tsetse plies . _.. * .. "... _, . .. I' by J .Hamon -I. , A .Challier', J and J ,Rageau+' Medical Entomologists, Office de la Wecherche L. Scientifique & Technique Outre Yer I. 1. IlYTEODUCTIOR . For centuries human and animal trypanosomiasis have ravaged vast areas of tropical Africa. As recently as 20 years ago sleeping-sick- ness was considered one of the most terrible of all endemic diseases affecting the African continent, Animal trypanosomiasis,render stock- raising difficult, if not impossible, in *any areas, and in cattle- grazing arieaa bordering on the Glossina zones livestock is weakened and does not supply any draugh$-anima$ (VAU@EL.~&al.,f963 - WILSON & al., - FOED, 11963) . liesearch efforts undertaken both in the Laboratory and in the field have supplied in recent years better methods of prevention, detection and treatment of trypanosomiasis. During the same period spreading possibilities of the disease have increased through comfiu- nica tion improvements and development ok workers migrations between neighbouring countries (ABEDI & I!AXLLBB, 1964). Human sleeping-sickness prevalence has been reduced to an extremely low level, but the disease is far from eradicated and many small foci either remain active or even,appear in previously cleared areas. The situation is slightly / ... -----I--------_----____l_l________e____l-~----------------~,---------- . + Q.L<.S.T.O."F. Team near O.C.C.G.E., P.O.B. 171, Bobo-Dioulasso, Upper - Volta . ++ O.B.S.T.0.:~. 70-74, route d'Aulnay, 93-Bondy, France . '. 6etter in West Africa, where the parasite Trypanosoma gambiense has apparently no aninal reservoir, than in East Africa where occurs also T.rhodesiense with both human and animal hosts (ROFBRTSQN, 1963 - WLL- LETT, 1963). Glossina-borne animal trypanosomiasis are always very wides- pread and hinder econornic developmeni of the majority of African states, ~ Chemotherapy cannot be extended to all domestic animals and has its .l setbacks, including drug resistance of the trypanosomes, Co tsetse fly control has an important part to play in the development oi the bfri- .; caan continent . 2. GEOGRAPHIC DISTRIBUTION OF TSETSE FEfiS . - Glossina sp. infest about 16.000.000 km' on the Airrican mainland. The,ir present distribution has been recently summarized by POBP (1963) but more accurate data for french-speaking states of \?est Africa can be found in MAILL6T i1952), RAGEAU & ADAPI (19SrS)j RICHEM- 3ACH (196%) and FINIBLLB i& al.(P963). Tsetse fly distribution is.,not en- tirely stable, even in absence of man interference. For exanlple seve- ral species retreated from large areas of south-east Africa during the Great Rinderpest of 4896,' and sinc'e this period d.pal1idipe.s and G, morsitans, followed by G.austeni, move slowly south in :!ozambique and .Rhodesia, restoring the situation i,rior to the rin'derpest . In West Africa, during the last P5 years, G.submorsitans has extended northwards its distribution ('dILSOPd, 1958). Such changes in distribu- ir tion are probably of comnon occurence, but escape detection by lack of accurate base data and surveys . \ Tsetse f1ie.s are classified into three groups, kypifhedi res- I pictively by G.palpalis, C.morsitans and G.fusca; their distributions are the following ones : I ni , 2.1. Glossina palpalis group (.. .. The palpalis group includes five species and four sub-spe- cies and is'restricted to idest and Central Africa, witb relics in E- thiopia arLd Arabia. L G.tachinoides occurs in the sudanese savannah and in the southern part of the sahelian area of West Africa, with residual foci 'in north-eastern Africa and in the South-east of the Arabian peninsula, It can withstand very dry conditions, but congregates in the dry sea4 son around water holes, residual pools of temporary rivers', and so On. .. 3 G.palpalis and G.fuscipes occur in the forest as well as in the guinean and sudanese savannahs. In the savannahs they are res- 'tricted to the inmediate vicinity of rivers and rivulets. In fores- ted areas also they congregate along watercourses, but not as stric- tly a6 in savannah, using them more for the flight linesthat they ef- fer than for their microclinate, 9 L , i G-pallicera occurs in rain forest areas, but can be encoun- * tered sometimes in the gallery forests of the guinean savannah . G.caliginosa is restricted to the coastal rain forest and to the mangrove areas . G.tachinoides, G.palpalis arid G.fuscipes are the main vec- tors of the human sleeping-sickness caused by T.gambiense . I 2.2. G.morsitans group . The morsitans group ihcludes seven species and three sub- \ species, all inhabiting savannahs , Gjmorsitans complex occurs mainly in sudanese savannahs, with C.submorsitans in Nest and Central Africa, and G.morsitans in East Africa , G .longipalpis is restricted to guiniean savannahs and to sou,.. partly deforested areas of the forest zone of +lest Africa . G.austeni is mainly a lowlands and coastal species of East Africa . G,swynnertoni and G.pal1idipes aro highland species of 3ast Africa. The,first one restricted to Kenya and Tanzania. The seconu H is species occurs from-Bthiopia to Yozaanbique and is present in some has the but r coastal areas; it occured in past in ïlata1 has been era- dicated there . 4 G .borgesi has been recently described from ?"ozambique (FIXEL .1 1960). G .niorsitans and G.swynnertoni are the normal vectors of the normal vectors of tile second form of human sleeping-sickness, caused 4 by T.rhodesiense; they are also, with G.pallidipes and G.submorsitnnf very importaitt vectors of' several aninal trypanosomiasis (caused by T.brucei, T.vivax, T.congolense) T.rhodesiense has beeil also rece- 1 vered f roin G,pallidipes since 1940 (;-acK1CC'IiAM, 1944) and more recen- tly froln G.fuscipes (80UTI33N & XOG'E&TSilPJ, 1961 - WICLETT & A1.,1964-I WPEL3TT, 1965) , .. 4 2.3. G.fusca group,' The fusca group includes 12 species and two sub-species, " Which inhabit mainly densely forested areas . Gknnshi, G.schwetzi, C,tabnniformis, C.haningtoni, G.seve- rini, G.vanhoofi a'nd G,fuscibleuris occur in the Lower guinean forest: sonetimes in very restricted area's 1 G.f~scaoccurs in all forested areas, from Sierra Leone to Uganda and in some of the larger gallery forests of the guinean sa- vannah . G.nigrofusca is widespread in the Upper guinean forest and in the northern gart of the Lower guinean forest, from Guinea to Ugar - da. G.inedicoruiii is restricted to the Upper guinean savnnnah anC forest . G,brevipalpis is very widespread in gallery forests and sa- vannahs of Prlali Bast Africa from Natal to Bastern Congo (Leopoldvil- le) and to Southern Ethiopia and Somalia . G.longipennis also an eastern savannah species) but Pes- is C tricted to Kenya, Ethiopia Southern Soinalia, South-eastern Sudan, North-western Uganda ar,d Northern Tanzania . The most common species belonging to the fusca group are important vectors of animal trypanosomiasis caused by ?'.vivax and T.congolense (J02DAN,P961 & 1965 a). 3. BIOLOGY OF TSETSE FLIES . 3.1. Keproduction cycle . Tsetse flies mate during the days following emergence, when the females are teneral. One insemination is sufficient for the who- le life of the female, but ;'*ales mate several times during their lif~ , and probably some females do the same; recent investigations carried out in Upper by one of us (A.C.) on G.galpalis have shown that Volta - non-teneral wild caught females are almost always inseminaled; howe- ver the percentage of inseminated females with incompletely filled - spermathecae reaches about amongst teneral flies, against only 51% in flies belonging to. the next two older age groups; so it is very probable that females cf C.palpalis several tisnes during their first days of life. Jemales yresect thsir.:naxinum attractive- ness for males When they are only 3 days old, andiare less attracti- ve with increasing age, although being always able to mate (NkSEi,l95f 5 JOhDBN, 1958 *) * ,Homologous matings are the rule, but sometimes :nating occurs in na- ture between closely related species; such matings are generally not fertile and can be lethal for the female The two ovaries are composed of two ovarioleg each, and each ovariole develops in turn (SBUHDERS, 1962 - CWALLIBW, 1963 b). The first ovulation occurs S to'U days after the emergence of the female; the mature ovocyte is not laid, but paskes into the female utr rus where fecundation occurs; then the larva grows inside the uterus, the food being supplied by the "milk glands" of the feaale; the la- te third instar larva is laid on the ground and pupates usually two :..& to five centimeters below the surface, some hours later. Larval de- velopment, in utero, takes about 10 days, during which the females bites at least three times, but the first larva is laid when the fe- male is about 16 days old, or moro. Yhen the first larva is laid the I secor,d ovocyte passes into the uterus, and so on. The duratiou; of the pupal life varies from 2Q to 60 days, according to temperature, The adult can fly some hours after its emergence from the pupariun and is able to bite the following day ., 3.2.