Up to date tsetse control or tsetse eradication programmes have been recorded from 23 African countries: Botswana, Cameroon, Central African Empire, Chad, Ethiopia, Ghana, Ivory Coast, Kenya, Malawi, Mali, Mozambique, Niger, Nigeria, Rwanda, Senegal, Somalia, South Africa, Tanzania, Togo, Uganda, Upper Volta, Zambia and Zimbabwe (see fig. 2.2.).
In general chemical control or eradication is achieved by applying, as selectively as possible, a relatively persistent deposit of an insecticide to the potential resting sites of the flies (socalled residual applications). So far in the majority of the operations either DDT, Dieldrin, Endosulfan and pyrethroids have been used. Very probably the most discriminative method of application is the groundspray procedure where the pesticide is applied either directly to distinct parts of the vegetation, e.g. tree-trunks up to a certain height, underside of inclined branches, by means of knapsack spraying equipment. For economic reasons and because of the extensiveness of certain flybelts, aerial applications have become widely used during the last decade. Also in aerial spraying many efforts have been made to transfer the insecticide as efficiently as possible to the target organism. The latter may be achieved by a proper selection of type of aircraft, atomizers and spray formulation. In this connection extensive use is made of the vast amount of knowledge which is available at present about the ecology of the tsetsefly species concerned. A major breakthrough has been the development of various ULV (Ultra Low Volume) aerosol formulations in recent years. It is not the intention to form residual deposits. Fly populations are eliminated by five or six serial applications with intervals in the order of 1 to 3 weeks.
Below an account will be given of the chemical control and eradication procedures which have been or are being applied in the various countries listed above. Special attention will be given also to the type of habitat treated and the success obtained. It must be mentioned that the brief summaries only cover the main activities and therefore do not necessarily refer to all the reports and publications which might be availabele.
Botswana
In the literature before 1972 only little information is available on tsetse control in Botswana. Graham (1964) refers to Dieldrin (Unimog applications of Dieldrex) applications against G. morsitans in an area near Maun, but provides no details on fly distribution, application rates etc. According to Davies (1979 a) thereafter, 12 500 km2 have been cleared and protected from tsetse, using knapsacksprayers and the selective application of Dieldrin and DDT. Lee et all. (1975) refers to groundspray operations in parts of the Okavango Delta with 5% DDT and 3% Dieldrin in residual applications (formulation not described).
According to Bowles (1979), the total area infested by G. morsitans centralis amounts to approximately 28000 km2 in the Okavango Delta plus 5000 km2 of the adjoining Kwando/Linyanti/Chobe river system on the country's northern border. It is reported in this publication that aerial spraying started with a series of small scale trials in 1972 and an experimental control spray in 1973 with fixed-wing ULV applications of endosulfan.
From 1974 onwards approximately 1500-4000 km2 have been treated annually, the spraying techniques being modified and refined every season. In the 4000 km2 area treated in 1977 total eradication of the fly seemed to be achieved (Davies 1979 b). Detailed knowledge on meteorological conditions and physiography of the area make it possible to take full advantage of drift of the sprayed insecticide (Bowles 1979). Endosulfan is used in five sequential applications of 6–12 g/ha each, at three week intervals.
In 1979 Decamethrin (dose rate 0.2 g/ha) was planned to be used for the first of the five cycles, as Decamethrin will have better results in the eradication of pregnant females present in a pre-spray population. The rest of the spray cycles were planned with Endosulfan at 9.5 g/ha.
Parallel to the main program, trials were undertaken to test new insecticides or different formulations (Lee et all. 1977, Allsopp and Coutts 1977), sometimes accompagnied by a monitoring team to evaluate the effects on nontarget animals (see Chapter 3). A range of organo-phosphorous compounds, pyrethrum and synthetic pyrethroids were evaluated, but only Decamethrin seemed to be comparable on a cost-efficiency basis with Endosulfan. It was also mentioned that trials were planned with Cypermethrin (Bowles 1979).
Technical details:
| Insecticide | : Endosulfan 35% in Xylol, ultra low volume (ULV)1) formulation |
| Dose rate | : 9.5–12 g active ingredient (a.i.)1) /ha |
| Insecticide | : Decamethrin |
| Dose rate | : 0.2 g/ha, first round in serial applications |
| Aircraft | : Twin-engined Rockwell Aero Commander |
| Atomizer | : Micronair Rotary Atomizer AU 3000 |
Cameroon (United Republic of)
Results of the use of Dieldrin groundspray in the Chari River basin in the far north of Cameroon are discussed under: Republic of Chad.
A tsetse control programme for the years 1976–1978 was launched to reclaim approximately 10 000 km2 of the Adamaoua Highlands west of Ngaoundéré by chemical means. Insecticides were sprayed by helicopter in single application to the dry season concentration areas of G. morsitans and G. palpalis, viz. riverine forests and comparable habitats.
The concentration areas were estimated to form 15% of the total area for 1976/1977, but after the operation actually 23% of the area had been treated. Based on previous experiences in Nigeria, it was decided that approximately two thirds of the tsetse habitats was to be sprayed with Dieldrin and one third with Endosulfan (the drier parts of the habitat). The northern boundary of the project area will be cleared from bush, to prevent tsetse infestation from the northern lowlands (G.T.Z. personal information).
By 1979, an area of 6500 km2 was free of tsetse. During the 1979 spraying season some observations were made on the side effects of a Dieldrin application (750 g/ha) on a gallery forest for the control of G. morsitans submorsitans (see Chapter 3).
Technical details:
see Nigeria: Technical details of aerial helicopter applications
Habitat: Southern Guinea Zone
Central African Empire
Tsetse control operations with Dieldrin groundspray started in 1960 in the Baboua Sous-Préfecture at the River Nie and its tributaries. As the results were satisfying it was decided to treat a more important area, viz. the Valley of the river Topia. The actions were directed against G. fuscipes fuscipes Newst. The whole vegetation of the valley was sprayed. Preliminary results were encouraging. (Yvore et al., 1962). Side effects were not studied.
Technical details:
| Insecticide | : Dieldrin |
| Formulation | : 2% a.i. solution of Dieldrex 20% |
| Equipment | : pressure retaining knapsack-sprayers |
| Habitat | : Guinea Savanna |
Chad (Republic of)
The results of a small scale control campaign with Dieldrin in the Logone and Chari River systems of Chad and North Cameroon are discussed by Mouchet (1962). During the dry seasons of 1972/1973 experiments with sterile males of G. tachinoides were carried out in two sites in the neighbourhood of N'Djamena (Cuisance and Itard, 1975). In cooperation with the Republic of Cameroon, from 1971–1974 a tsetse control operation eradicated the riverine population of G. tachinoides from the whole of the Assale-Serbewel area situated in between N'Djamena and Lake Chad for the control of animal trypanosomiasis. The technique employed was selective application of DDT to the preferred resting sites by groundspray application (Tibayrenc, 1977). A total of 12 500 ha of tsetse habitat was reclaimed.
Within this large scale eradication campaign field trials with Decamethrin were performed in the Chari Valley south of N'Djamena in 1976–1977. Decamethrin was applied from the ground in concentrations varying from 1.25 to 40 mg a.i./l. As they used 400 l/ha, it can be calculated that 0.5 to 16 g a.i./ha was used. Spraying of 7.5 mg a.i./l, which corresponds with 3 g/ha gave immediate total control but its persistence proved low and the residual activity was limited. For comparison Endosulfan was applied at 2 g/l, which implies a calculated dose rate of 800 g/ha (Gruvel and Taze, 1978).
Technical details:
| 1962 | Insecticide | : Dieldrin |
| Formulation | : 1.8% watery solution of Dieldrin 50% WP single application, discriminative spraying | |
| Equipment | : Knapsack sprayers | |
| Habitat | : Sudan Savanna | |
| 1971-1974 | Insecticide | : DDT |
| Formulation | : 2.5% wettable powder, 75% a.i. selective and discriminative handspraying | |
| Dose rate | : 4-13.5 kg/ha, mean 5.7 kg/ha | |
| 1976-1977 | Insecticide | : Decamethrin |
| Formulation | : A solution of 20–25 g a.i./l | |
| Dose rate | : 1.25–40 mg a.i./l, applied at 400 l/ha | |
| Insecticide | : Endosulfan, 365 g a.i./l | |
| Dose rate | : 2 g a.i./l | |
| Habitat | : Gallery forest, bordering rivers, lakes and waterholes |
Ivory Coast (Republic of)
DDT and Dieldrin were used in the gallery forests of Abengourou and Daloa for the eradication of G. palpalis gambiensis (Challier, 1971).
In field trials two methods of tsetse control were tested in and around coffee plantations in Vavoua, north of Daloa. Blue tissue screens 130 × 90 cm2, impregnated with Decamethrin (75 mg a.i./m2) were placed at 10 screens/ha, and a 3m wide vegetation belt was treated by selective handspraying of Decamethrin at 30 g a.i./km. No full eradication of G. palpalis was achieved (Challier and Gouteux, 1978; Laveissière et al., 1979).
The third phase of a WHO research project for the evaluation of various insecticides for the control of riverine Glossina vectors of human trypanosomiasis was carried out in the central part of Ivory Coast in 1978–1979 (Bouaflé area). Phase I and II of this project consisted of small-scale field trials in Upper Volta. The spraying program of the third phase involved residual Endosulfan applications (267 g a.i./ha) as barrier sprays around infected villages in conjunction with five sequential aerosol applications (10 g a.i./ha) on the villages themselves.
The fringing forest along the Marahoué River and its tributaries were treated with Decamethrin (12.5 g a.i./ha) in residual applications. The residual sprayings were repeated three times at monthly intervals, whereas the aerosol application was repeated at two week intervals. The vegetation in the area consists mainly of dense rain forest and savanna woodland. Reduction of tsetse fly populations was not satisfactory. Even an increase of the Endosulfan dose rate around the villages to 563 g a.i./ha did not result in a further reduction of fly numbers (Kuzoe, 1979). These trials were accompanied by side effect studies (see Chapter 3).
Technical details:
Aerial spray Bouaflé 1978–1979
| Insecticide | : | Endosulfan, Decamethrin |
| Formulation | : | Endosulfan - Hoechts oil based ULV (Thiodan 25%) in Diesel Decamethrin - Procida oil based ULV (1.5%) in Diesel |
| Dose rate | : | Endosulfan aerosol 10 g a.i./ha Endosulfan residual 256 g a.i./ha Decamethrin residual 12.5 g a.i./ha |
| Equipment | : | Bell 47 6 AA helicopter Electrically driven rotary atomizers operating at speeds of 5000-15 000 rpm, each with two 1.0 mm nozzles |
| Droplet size | : | Aerosols VMD1) 35–40 μm Residual VMD 150 μm |
| Habitat | : | Dense humid rain forest and savanna woodland |
Kenya
In Kenya tsetse control has been directed mainly to G. fuscipes and G. pallidipes, which are responsible for the transmission of human trypanosomiasis in the Nyanza provinces. Some of the preliminary applications of Dieldrin groundspray were reported by Thomson et al. (1960). Both in Central and South Nyanza spraying operations have been carried out reclaiming part of the shore-line of Lake Victoria and some of the valleys which were formerly heavily infested by tsetse. In certain places bushclearing was applied to create barriers against re-invasion of reclaimed areas (e.g. Bertram, 1969). In the Lambwe Vally in South Nyanza Dieldrin applications by means of fixed-wing aircraft and helicopters were made which gave reductions of 99% for periods up to several months of the local G. pallidipes population (Willett, 1972; WHO, 1976). Some observations were made on side effects (see Chapter 3).
Technical details:
Groundspray
| Insecticide | : | Dieldrin |
| Formulation | : | 1.8% solution from Dieldrex 15 T (18.2% Dieldrin emulsion) in water |
| Equipment | : | Kiekens Dekker portable mist blowers |
| Dose rate | : | 4 applications of a 1.8% Dieldrin solution (1960), 2 applications of: 2.5 to 5% Dieldrin solutions (1967–1970) |
Aerial spray
| Aircraft | : fixed-wing and helicopter |
| Equipment | : Bi-Flon equipment |
| Dose rate | : Two applications of Dieldrin resulting in a total of 144–409 g/ha |
| Habitat | : relatively moist Savanna woodland |
Malawi
There is a record from Steele (1956), in which the use of γ-BHC against G. brevipalpis Newst. is reported. A 4% solution of γ-BHC in diesel oil is applied in six applications with intervals of 10 days, by means of a ‘Swingfog’ spraying apparatus. According to FAO 1976 sporadic human sleeping sickness cases are probably imported, while animal trypanosomiasis does not constitute a serious problem.
Mali
The need for tsetse control has only occurred in the most southern part of the country, alongside the river Niger and its tributaries. In 1962, riverine forests around Bamako were treated with single applications of residual insecticides, to eradicate G. palpalis gambiensis, vector of human trypanosomiasis. To prevent reinvasion, chemical barriers were laid with 4% Dieldrin solutions. The campaign was successfully continued from 1963–1968. Approximately 400 km of fringing forests were kept under control with either DDT of Dieldrin (Challier, 1962 and 1971).
In 1972–1973 trials were carried out by WHO to study the effectiveness of several insecticides in ULV formulation or in powdered formulation with residual action. The operation was performed on gallery forest bordering watercourses and other permanent waterholes against G.palpalis gambiensis and G. tachinoides. Among the insecticides tested were pyrethroids, organophosphorous compounds and methoxychlor (Challier e.a., 1974).
In 1977 vector control was limited to a few localised spraying programmes in riverine areas for the reduction of human sleeping sickness (Gruvel 1977). Since 1977 a second (USAID) Mali Livestock tsetse eradication program is in operation. Approximately 30% of the cattle is in danger of trypanosomiasis infection. So far a zone of 19 000 km2 along the River Niger north of Bamako is selected for treatment against G. morsitans (Coulibaly and Diallo, 1978; Okiwelu et al., 1978, 1979).
Side effect studies are not included in the program.
Technical details:
Groundspray (1963–1968)
| Insecticide | : Dieldrin, DDT |
| Formulation | : 3% solutions in water of Dieldrin 20% EC1) DDT: no details recorded |
| Equipment | : Swingfog sprayer |
| Habitat | : Sudan Savanna |
Aerial spray (1972–1973)
| Insecticide, formulation and dose rate | : | NDRC 119 ULV formulation, 5–40 g a.i./ha Bromophos (Nexion) ULV formulation, 200–1000 g a.i./ha Fenitrothion ULV formulation, 10–1000 g a.i./ha Jodfenphos (Nuvanol) ULV formulation, 160–800 g a.i./ha Tetrachloorvinphos (Gardona) and Metoxychlor residual formulation 100–3000 g a.i./ha |
| Equipment | : | Bell 47 G-4A Helicopter |
| Droplet size | : | ULV formulation VMD 80–100 μm Residual formulation VMD 50–300 μm |
| Habitat | : | Wooded Sudan Savanna |
Mozambique
The only record of tsetse control operations in Mozambique, which has come to our knowledge, was the eradication of G. morsitans in the Govuro district, south and near the mouth of the Suave River (Silva and Silva, 1960). From 1949 to 1956 an area of approximately 1200 square miles (3008 km2) has been reclaimed by means of game eradication, settlement of local people, dipping of cattle with DDT and γ-BHC, controlled grass fires and deflying of the traffic. Habitat: an undifferentiated, relatively dry Savanna woodland (Sudan type).
Considerable areas of Mozambique near the Rhodesian border were treated by knapsack spraying in the early 1970s but this operation was discontinued a few years ago (N.J. Alsop, pers. communication). Animal trypanosomiasis is an important economic problem in Mozambique now, covering an area approaching 80% of the land. Approximately 70% of the country is now infested with G. morsitans and G. pallidipes in a tsetse belt continuous with that in Tanzania and Zambia. Human Sleeping Sickness is limited to the Northern Provinces (Tryp. Bureau Min. of Health, 1979).
Niger
An area of almost 3500 km2 in and to the west of the River Niger valley is infested with Glossina morsitans submorsitans and G. tachinoides and trypanosomiasis threatens the 400 000 transhumant cattle that pass through the region each year. Efforts to control trypanosomiasis have been in operation since 1942 and have principally involved the clearing of vegetation from the banks of the River Niger, and the spraying of insecticides from helicopters in the dry season (Nababa, 1978). In the 1967/1968 dry season a groundspray operation was started with several residual insecticides. At the confluence of the River Tapoa and River Niger a cleared barrier was made, to prevent reinvasion of flies from the south in reclaimed areas. Helicopter spraying of approximately 1200 ha of riverine vegetation was carried out successfully with Dieldrin in groundspray operations to form deposits with residual action of 2 to 3 months (Van Vegter, 1976).
In 1976 a joint UNDP/FAO campaign was initiated and in February 1977 a chemical control program using helicopter application was performed in the Parc National du W du Niger. Endosulfan was sprayed once at 900 g a.i./ha onto the riverine forest vegetation where, in the dry season, the Glossina are concentrated. 2500 km of riverine forest along the Tapoa and the Mekron were treated. The campaign however was not successful since, within two weeks, teneral flies were being trapped in field surveys (Park, 1979). Observations on the side effects of this application were carried out (see Chapter 3).
Technical details:
Groundspray
| Insecticide | : | DDT, γ-BHC and Dieldrin mixture |
| Formulation | : | Multanin liquide 3 (DDT 23%, γ-BHC 9%, Dieldrin 9%), 3% watery solution Multanin (DDT dissloved in Kerosine) pur DDT powder Dieldrin 20% (Shell) dissolved in water, 1 kg a.i./15 l |
| Equipment | : | Solo knapsack sprayer (3% Multanin liq. 3) Swingfog back sprayer (Multanin) Schupze-Eckel duster, mounted on a vehicle (DDT powder) |
Aerial spray
| 1969/1970 | Insecticide | : | DDT, γ-BHC and Dieldrin mixture formulated as Multanin liquide 3, 12.5% watery solution; 5.0 l/ha; two applications with three-week intervals |
| Aircraft | : | Helicopter Bell 47 G4 | |
| Equipment | : | electrically driven twin discs, VMD 100–300 μm | |
| Habitat | : | Sudan Savanna | |
| 1977 | Insecticide | : | Endosulfan (Thiodan 25 ULV) |
| Dosage | : | 900 g a.i./ha | |
| Aircraft | : | Helicopter Bell 206 B | |
| Equipment | : | 6 micron electrically driven spraying disc atomizers, VMD 30–300 μm | |
| Habitat | : | Riverine forest and woodland in Sudan Savanna |
Nigeria
Tsetse control and eradication in Nigeria with chemical means has been undertaken since 1954. Different methods were used depending on the vegetation zone and the Glossina species present. In the treated areas, three main species of tsetse occur: G. morsitans submorsitans, G. tachinoides and G. palpalis.
Two major vegetation zones are to be considered, the Northern Guinea Savanna and the Sudan Savanna, which are distinct in some parts and overlap in the Sub-Sudan zone. Until 1970, only groundspray methods with residual insecticides were used. The various spraying techniques which were developed, are described in detail by Aitchison and Glover (1970).
During the years 1954–1970 a total of 27 570 km2 of tsetse infested country in north-eastern Nigeria has been reclaimed, making 68 740 km2 safe for grazing of cattle (Davies, 1964 and 1971). Insecticide barriers have been successfull in protecting sprayed areas from fly reinvestation between spraying seasons. It is reported that cleared barriers have, so far, succeeded in providing permanent protection to completed projects. Periodic checks indicate that all the country reclaimed is free of fly.
In 1970 insecticide spraying by means of helicopter was introduced when a small area was successfully treated with 4% Dieldrin against G. morsitans. Since 1971 helicopter applications of both Dieldrin and Endosulfan have become a regular means of tsetse eradication in Nigeria, in combination with groundspraying of DDT and Dieldrin. Dependent on vegetation density and the fly species concerned, 8–16% of the totally infested area is actually sprayed. The degree of reinvasion encountered per annum is approximately 25% for each project area. All reinfested areas were successfully resprayed (Spielberger et al., 1977).
Apart from the main program, field trials were carried out continuously to improve spraying techniques and to test new formulations or insecticides. The fixed-wing ULV application technique as known from Botswana, was tried out in March 1976. Endosulfan 25% ULV in cotton-seed oil was applied in five sequential applications of 14 g a.i./ha at 10 to 12 day intervals. However, complete tsetse knockdown was not achieved (Allsopp, 1977).
In 1977 and 1978 field trials were conducted with the synthetic pyrethroids Permethrin, Cypermethrin and Decamethrin against G. palpalis and G. tachinoides. The insecticides were applied successfully from the ground at 0.5%, 0.3% and 0.075% respectively, to fly resting sites on vegetation using pressurised knapsack sprayers, populations of both species being eradicated after a single application. Following residual spraying from a helicopter, only Decamethrin at 30 a.i. g/ha achieved complete eradication. It was thought that Permethrin wettable powder at 200 g a.i./ha and Cypermethrin at a dosage over 150 g/ha could be successful in the future (Spielberger et al., 1979).
By the end of the 1975–1976 spraying season some 194 500 km2 had been reclaimed, mainly by the application of residual insecticides from the ground, but including some 9800 km2 cleared by the application of residual insecticides from helicopters. Plans have been made to complete the clearance of tsetse from almost 259 000 km2 by 1986 (quoted by Jordan, 1978).
Observations on side effects were carried out during the groundspray and aerial operations of Dieldrin and Endosulfan and during the pyrethroid trials (see Chapter 3).
Technical details:
Groundspray
| Insecticide | : | DDT (drier areas) and Dieldrin (wetter areas) |
| Formulation | : | 2.5-5% DDT WP (70% DDT) 2% Dieldrin (from Dieldrex 15 T) in water |
| Equipment | : | knapsack, motorized mistblower |
| Habitat | : | Sudan and Northern Guinea Savanna |
| Insecticide | : | 0.5% Permethrin (WP 25%), 0.3% Cypermethrin (EC 40%) and 0.075% Decamethrin (WP 2.5%), all formulated in mineral oils |
| Equipment | : | Knapsack sprayers |
| Habitat | : | Sub Sudan Savanna |
Aerial aerosol spray
| Insecticide | : | Endosulfan (Thiodan 20% EC) Endosulfan (Thiodan 25% ULV HOE 2958) |
| Dose rate | : | 14 g a.i./ha, blanket spraying; 5 sequential applications with 12 day intervals |
| Aircraft | : | Piper Aztec PA 23/250 |
| Atomizer | : | Micronair AU 3000 |
| Droplet size | : | VMD 27–37 μm |
| Habitat | : | Southern and Northern Guinea Savanna |
Technical details Nigeria (continued):
Aerial residual spray:
| Insecticide | Dieldrin | Endosulfan | Pyrethroids | ||
| Formulation | Ensodil EF 4220 18% ULV in Shellsol R/Dutrex | Thiodan HOE 2958 25% ULV | Permethrin (NRDC 143 25% WP) dilued with water to 3–5% | Cypermethrin (NRDC 149 40% EC) 2.5%–3.75% solution (ULV) | Decamethrin (NRDC 161 2.5% WP) 0.75%–1.0% solution (ULV) |
| Dose rate | 500–1500 g a.i./ha | 800–1200 g a.i./ha | 200–300 g a.i./ha | 60–150 g a.i./ha | 20–40 g a.i./ha |
single application only 5–16% of habitat | single applications | ||||
| Aircraft | Bell helicopter 47G4A | Bell helicopter 47G4, 280 HP | |||
| Atomiser | electrically driven twin discs | 6 electrically driven single discs | |||
| VMD of spray | 150 μm | 150 μm | 150 μm | ||
| Habitat | Sudan and Northern | Sub Sudan Savanna | |||
| Guinea Savanna | |||||
Rwanda
In Rwanda tsetse control by chemical means took place for the first time in the Bugesera region (S.E. Rwanda) in 1960. From August 1960 till March 1961 an area of 190 km2 (3 568 ha tsetse biotope) was reclaimed by discriminative aerial spraying of Dieldrin (Buyckx, 1965).
As Telodrin is 2.5 times as toxic to the Rwanda species of tsetse (G. Morsitans centralis Machado) as Dieldrin costs of the campaign were supposed to be reduced by replacing Dieldrin by Telodrin. In the season 1961/1962 trials were made with both insecticides in two different areas. Tsetse elimination was reached over 430 km2 (5 321 ha biotope).
Finally, in 1963/1964 Dieldrin was applied during the first half of the campaign and later replaced by Telodrin within the same area. Thus 500 km2 of flybelt (13 240 ha biotope) were reclaimed of tsetse eventually (Buyckx, 1965). In the first season series of 8 successive applications with 28 day intervals were usual, but this was changed to 24 day intervals in the '61/62 and '63/64 campaign due to shorter duration of pupal life.
Studies on side-effects were not presented.
Technical details
| Insecticide and dose rate | : | Dieldrin 44 g a.i./ha or Telodrin 16.5 g a.i./ha, sequential applications |
| Formulation | : | Dieldrin FL 20% dissolved in illuminating Kerosene (1:7.5) Telodrin 15% EC dissolved in Diesoline and illuminating Kerosene (1:1:8) |
| Aircraft | : | PA-18 A |
| Atomizer | : | Micronair A 100 |
| Habitat | : | Relatively moist Savanna Woodland |
Senegal (Republic of)
From 1970 until 1973 a succesful groundspray operation against G. palpalis gambiensis had been directed in the so-called area Niayes of Senegal as to improve conditions for cattle breeding and to eradicate residual foci of Sleeping Sickness. Niayes are fertile areas of land characterised by dense palm growth or cultivated gardens and orchards. The area actually sprayed amounted to 850 ha, making 36 500 ha safe for grazing (Toure, 1973).
Tsetse flies have been found in other more urban environments, notably at the Zoo at Dakar-Hann where control by selective Endosulfan application is underway. It is recommended to control other small populations along the Nougouna River and in some Niayes by the use of pesticide impregnated traps or screens before tsetse dispersion occurs (Laveissière and Traore, 1979).
Technical details:
Groundspray (1970–1973)
| Insecticide | : Dieldrin 20% |
| Dose rate | : Dieldrin 2%, resulting in 160 mg a.i./m2 |
| Equipment | : Cosmos sprayer |
| Habitat | : Guinea type forest vestige |
Somalia (Somali Democratic Republic - SDR)
Four species of tsetse fly occur in Somalia, notably G. pallidipes, G. longipennis, G. brevipalpis and G. austeni. No cases of human trypanosomiasis have ever been recorded from Somalia (FAO, 1979). Animal trypanosomiasis occurs in the basins of the Giuba and Scebeli Rivers. During 1977, at the request of the SDR the Overseas Development Administration (ODA) of the British Government sent a reconnaissance mission to obtain information relevant to the possibility of implementing a tsetse and trypanosomiasis control project in the SDR, (COPR, 1979) and a pre-project training course was introduced in early 1979.
South Africa
An elaborate description of the use of organichlorine insecticides in tsetse control operations in South Africa is given by Du Toit (1954).
From 1945 to 1953 aerial spraying of γ-BHC in smoke form (described as Thermal exhaust aerosol method) against G. brevipalpis and G. pallidipes took place in Zululand, being the only tsetse infested area in South Africa at that time. As this happened in the early phase of aerial spraying in tsetse control, trials were made with helicopter and fixed-wing aircraft. Eventually sprayings with a Piper Super-Cub gave the best results.
Areas inaccessible to fixed-wing aricraft were initially treated with groundspray methods, but ultimately these were replaced by aerial spraying with helicopter. The groundspray teams were applying 5% DDT in dust form. To prevent tsetse from extending its territory, a barrier was established by bush clearing an area of approximately 2 miles wide and 94 miles in total length (Du Toit, 1954). No cases of either human or animal trypanosodiasis have been observed in recent years (FAO, 1979).
In Namibia (South West Africa) the Eastern Caprivi Zipfel, bordered by Botswana, Angola, Zambia and Zimbabwe is constantly invaded by tsetse flies from foci in the Okavango Swamps in Botswana and in Angola and Western Rhodesia.
Up to 1978 groundspray operations were conducted every winter using Dieldrin, to minimize penetration of tsetse into the country from outside its borders (Dent, 1979).
No side effect studies have been reported on any of these operations.
Technical details (Du Toit, 1954):
Groundspray
| Insecticide | : DDT |
| Formulation | : 5% DDT dust powder |
| Dose rate | : 7.9 kg/ha |
Aerial spray
| Insecticide | : | γ-BHC |
| Aircraft and dose rate | : | - twin-engined Anson, 100 g a.i./ha emitted through the exhaust stacks by gravity; 8 applications - single-engined Piper Cruiser, 40 g a.i./ha emitted through the exhaust stacks by fuelline pump; 8 applications - Sikorsky S 51 helicopter, 80 g a.i./ha emitted through the single exhaust stack by gravity; 8 applications |
| Habitat | : | Dry woodland savanna |
Tanzania
In the early fifties game eradication was practised on a large scale in Shinyanga-North. It is no longer considered an important control method anymore (Potts et al., 1952).
Apart from South Africa, early research on the use of aircraft in tsetse control has been reported from Tanzania (Yeo and Thompson, 1954). Initially the aircraft were equipped with gravity-fed exhaust injection systems using the hot gases from the aircraft exhaust to atomise the insecticide formulation. Extensive research with different types of aircraft led to the development of the Micronair Rotary Atomisers now being used in Botswana, Nigeria and Rhodesia (Lee, 1969; Lee et al., 1969).
At the Tropical Pesticide Research Institute (TPRI) in Arusha many different pesticides have been tested experimentally for tsetse control, mostly in small pilot projects (Burnett, 1962 a,b; Burnett et al., 1964; Hocking et al., 1966; Irving et al., 1969; Irving and Beesely, 1969; Tarimo et al., 1971).
A combined Tanzanian/USAID project on tsetse control by the sterile male technique is conducted at the Tanga Tsetse fly laboratory. The test site of 200 km2 was sprayed twice, at one months interval, with an aerial application of Endosulfan at 20 g/ha. Each application reduced the tsetse population by 95%. A 1 km barrier around the site reduced the risk of reinvasion.
In November 1977 the release of sterilised male G. morsitans pupae was initiated, resulting in a population of only 7% of its pre-spray level in July 1978.
However, the G. pallidipes population had fully recovered to its pre-spray level. The influence of the sterile males appears to have successfully prevented the recovery of the G. morsitans population in the test site (Dame and Williamson, 1979).
DNOC, used as a defoliating agent in tsetse control was aerially sprayed on a 1000 ha area. Side effects were studied (See Chapter 3).
Uganda
A total area of 39 583 km2 was successfully reclaimed from tsetse infestation between 1947 and 1973. Various methods have been used, like bushclearing for barrier zones and game eradication. Up to June 1974 areas in Uganda totalling 8600 km2 have been successfully reclaimed by discriminative groundspraying 3% Dieldrin water emulsions.
Control methods are mainly directed to the elimination of trypanosomiasis from cattle. An area of approximately 48 000 km2 still remains under tsetse occupation (Wooff, 1969; Kanwagye, 1975).
Trials to control tree regeneration in tsetse barrier zones with Tordon 101 arboricide are being investigated. Results are reported to be encouraging (Oliaka, 1975).
A study on analysis of residues resulting from 10 years of Dieldrin groundspraying was carried out from 1972–1974 (see Chapter 3).
Technical details:
| Insecticide | : Dieldrin Endosulfan (only 351 km2 in 1971) |
| Fromulation | : 3% Dieldrin from Dieldrex 15T 18% EC 2.5% Endosulfan from Thiodan 35% EC |
| Dose rate | : Dieldrin: 90–180 g a.i./ha Endosulfan: no detailed information |
| Equipment | : Leo-colibri CP 201 and CP 148 pneumatic knapsack sprayers and CP 40 knapsack mistblowers |
| Habitat | : Woodland savanna |
Upper Volta
In the dry season of 1962/1963 trials with γ-BHC fogging were carried out near Sénoufo de Kankalaba, Western Upper Volta, to exterminate G.palpalis gambiensis. Riverine forests were sprayed six times (3% solutions of γ-BHC in diesel oil) at 15 day intervals. Two months after the last application fly density was reduced to 2% of the pre-spray figures. A barrier was created by daily treatment with 3% DDT during three weeks (Challier, 1964).
In recent years agricultural development and resettlement in the moist savanna zones south of the Sahel requires an effective control of human Sleeping Sickness. Vectors are the riverine species G. tachinoides and G. palpalis.
In 1976 WHO started a three year research project on the Comoe and Volta Noire Rivers in the South West, treating riverine forests by helicopter. In phase I various insecticides were tested for their potential against G. tachinoides on the Comoe River (see fig. 2.3, area 2). The data on the various tests are summarized under: technical details. The aerosol unilateral spray technique with two atomizers along a boom on the left side of the helicopter allows the helicopter main rotor downwash to direct the spray droplets more effectively into the riverine canopy, to obtain penetration of insecticide droplets into parts of the G. tachinoides habitats considered important as resting sites. Endosulfan, Decamethrin and Permethrin aerosols gave good fly reductions, as did the residual application of Decamethrin, controlling G. tachinoides for a period of almost 40 days (Molyneux et al, 1978; Lee et al, 1978, Baldry et al, 1978 a,b; van Wettere et al, 1978).
During phase II in 1977–1978 trials with Endosulfan and the pyrethroids were continued on the fringing forests of the Volta Noire and the Comoe (fig. 2.3, area 2 and 3). Endosulfan and Permethrin were tried as aerosols in five sequential applications. Both Endosulfan and Permethrin and also Decamethrin were tested in repeated residual sprayings. All of the applications were effective in eliminating tsetse populations for a period of at least 4 months. Phase III of this research project was located in the more humid forest savanna and fringing forests of Ivory Coast (WHO 1978).
Environmental studies were carried out to assess the impact of the various insecticides on non-target organisms (see Chapter 3).
The biological control of tsetse flies by the steril male release technique is studied in the C.R.T.A. in Bobo Dioulasso. An integrated control combining chemical and biological control methods seems to have practical potentials.
MAP OF UPPER-VOLTA AND IVORY-COAST.
Fig. 2.3. Map showing study areas
 | Areas in which tsetse control research programs were carried out | ||
| 1 | 1963 | γ-BHC | |
| 2 | 1977 | phase I trials | |
| 1978 | phase II trials | ||
| 3 | 1978 | phase II trials | |
| 4 | 1979 | phase III Endosulfan Decamethrin | |
| 5 | 1977 | Release of sterile males | |
| Bioclimatic zones: | |||
| I | Sudan | ||
| II | Northern Guinea | ||
| III | Southern Guinea | ||
| IV | Forest/Savanna | ||
| V | Rain Forest | ||
 | |||
Small scale trials show promising results in reducing G. palpalis gambiensis population levels after one Endosulfan treatment and the introduction of sterile males (Cuisance et al., 1978).
Technical details (1976–1978):
| Insecticide | : | Endosulfan Hoechst ULV Thiodan (25%), diluent Shellsol A Decamethrin Procida ULV (0.5%), diluent Shellsol A and Procida EC 25 (2.5%), diluent filtered riverwater Permethrin Wellcome (4%) in Diesel, and (50%) in water Azamethiphos Ciba Geigy ULV (25%), diluent Diesel Tetrachlorvinphos Shell Gardona EC (24%), diluent Shellsol A Fenthion Bayer (95% solution), diluent Diesel |
| Dose rates | : | See table 2.1. |
| Equipment | : | Bell 47G-4A helicopter Electrically driven rotary atomisers, making up to 16 000 rev/min |
| Droplet size | : | Aerosol 40 μm VMD, spray 150 μm VMD |
| Habitat | : | Southern Sudan and Northern Guinea Savanna |
Table 2.1.: Dose rates of insecticides applied in the WHO research project in Upper Volta during 1976 to 1979 and their effectiveness in reducing the G. tachinoides population
| Insecticide | Year | Dose rate in g a.i./ha | Good reduction | ||
| Aerosol | Residual spray | Aer. | Res. | ||
| Endosulfan | 1977 | 5.4, 9.0 | + | ||
| 1978 | 5(1×) + 10(4×) serial application at 12 day intervals | 100(2×),and 200(2×),both at one month interval | + | + + | |
| Decamethrin | 1977 | 0.12,0.36 | 12.5 | + | + |
| 1978 | 0.2 | 12.5(2×), one month interval | + | + | |
| Permethrin | 1977 | 1.9,4.3 | + | ||
| 1978 | 2.5(1×) + 3.0(4×) | 50.0 | + | + | |
| Fenthion | 1977 | 2.6 | - | ||
| Azamethiphos | 1977 | 3.3 | - | ||
| Tetrachlorvinphos | 1977 | 6.7 | - | ||
Zambia
The Zambian Veterinary and Tsetse Control Services have extensively used bush-clearing as a means of tsetse control in various parts of the country. Groundspraying has been carried out with vehicle-mounted mechanical equipment and with knapsack sprayers. It is intended to intensify the last method. (R.S. Hacizenge, personal communication, 1976).
From 1962 to 1964 parts of the Chipangali area of Eastern Zambia were sprayed with a Dieldrin emulsion. The effect of Dieldrin on wildlife was reported (see Chapter 3).
Large scale aerial ULV application of Endosulfan takes place in Zambia since 1968, G.morsitans morsitans being the target organism. In 1968 an area of 1600 km2 was sprayed from aircraft, five times, at approximately three week intervals, with an Endosulfan aerosol. Postspray flyrounds showed that tsetse eradication was apparently achieved except near an unsatisfactory isolation barrier (Park, Gledhill, Alsop and Lee, 1972). The environmental impact of this operation was assessed (see Chapter 3). In 1970, 1971 and 1972 areas of 1500 km2 yearly were sprayed using the same techniques (Kendrick and Alsop, 1974).
Over 60% of Zambia's cattle are exposed to trypanosome challenge, limiting animal production in over a third of the country. Human trypanosomiasis may also restrict development. From 1974 to 1979 a large area has been cleared from tsetse by both aerial and groundspray operations. Some of the data are summarized below:
| Area covered by Aerial spraying (km2) | Area covered by Groundspraying (km2) | |||
| Unimog sprayers | Knapsack sprayers CP 148 | |||
| 1974 | 1222 | |||
| 1976 | 1100 | 1300 | ||
| 1978 | 2000 | 516 | 260 | |
| 1979 | 700 | 400 | ||
| .. | ||||
| planned | 16 000 | 2500 | to be linked up eventually with the aerially treated area | |
(Dept. Vet. Tsetse Control Serv. Zambia, 1977, 1979 a,b,c).
A UNDP/FAO project for Africa, sponsored by the Governments of 12 African countries, with other countries expected to join in due course, was set up in Zambia recently. This project is directed to the control of African Animal Trypanosomiasis in the Dry Savanna Zone. A research project will be set up for the control of G. morsitans, G. submorsitans and G. pallidipes with biodegradable insecticides having a minimal impact on non-target organisms.
Technical details:
Groundspray:
| Insecticide | : | DDT 38 g/l from DDT 75% WP1) Dieldrin 18 g/l from Dieldrex 15T 20% EC (added to the DDT solution during the last 3 months of spraying season) |
| Equipment | : | Unimog (Mercedez Benz) tractors carrying 750 l spray tanks connected with pump and atomizers Knapsack sprayers CP 148 |
Aerial spray:
| Insecticide | : Endosulfan 25% and 35% EC |
| Formulation | : 200 g/l in SHELLSOL AB |
| Dose rate | : 4 or 5 serial applications at 15–28 g a.i./ha/application |
| Aircraft | : 1968: Cessna 180 and Piper Pawnee From 1970 Beech Baron Aircraft |
| Atomiser | : Exhaust Injection, Micronair AV 3000 rotary atomisers |
| Droplet size | : 20–100 μm VMD |
| Habitat | : Dry deciduous forest and savanna on the Kalchari Sands |
Zimbabwe
Bushclearing and game eradication have been a widely adopted method of tsetse control in Zimbabwe (Lovemore, 1961). Game eradication for the control of tsetse is reported from this country from as far back as 1920 (Roth, 1967). Residual insecticides have been applied since 1959, when the vegetation of the Lundi River system was sprayed with a 3.6% Dieldrin solution. The extension of the south-eastern flybelt was successfully stopped after only one application (Farell, 1960). Dieldrin and DDT have been used widely ever since for tsetse control, applied either by aircraft (Cockbill et al., 1963) or groundspray equipment (Vale, 1968; Casewell, 1969). As bushclearing did not arrest the advance of the tsetseflies, part of the 4900 km2 flybelt of Inyanga North and south-eastern Mtoko was sprayed in 1966 and 1967.
However the use of Dieldrin and DDT applied either alone or in combination, did not result in complete eradication of the G. morsitans population (Casewell, 1969). In the 1968 spraying operations only 5% DDT WP suspensions were used because of lower insecticide costs (Vale, 1968). Following the successfull ULV aerial applications of Endosulfan in Zambia (Park et al., 1973) and Botswana (Kendrick and Alsop, 1974), 500 km2 of bush infested by G. morsitans morsitans and G. pallidipes was sprayed in 1974/1975 in Zimbabwe using the same techniques (Chapman, 1976). Around the Endosulfan area a barrier was created by DDT groundspraying. Although a marked decrease of the fly population was observed, total eradication was not achieved. The reoccurrence of flies was supposed to be caused by reinvasion of vehicle-carried flies. Side effects of an ultra low volume aerial application of Endosulfan to Savanna woodland were studied (see Chapter 3).
Experiments with biological control have been carried out in the Lake Kariba region. The first results were reported to be promising (Dean et al., 1969).
Technical details:
Groundspray:
| Insecticide | : | Dieldrin, DDT |
| Formulation | : | 3.1 and 3.6% Dieldrin emulsion in water from Dieldrex 15T (containing 18.6% Dieldrin EC) 5% solution in water of DDT 75% WP |
| Equipment | : | motorised, shoulder mounted mist-blowers |
Aerial spray (1974/1975 operations only):
| Insecticide | : | Endosulfan |
| Formulation | : | Endosulfan 20% and 25% EC in Shellsol AB |
| Dose rate | : | 6 or 7 1/km2 (14 g a.i./ha) 5 applications with 12 to 18 day intervals |
| Aircraft | : | Piper Aztec (1974), Piper Pawnee (1975) |
| Atomiser | : | Micronair AU 3000 |
| Habitat | : | Miombo woodland (comparable to Guinea Savanna of West Africa) |
Conclusions
Only a few pesticides have been used succesfully so far. It concerns especially those pesticides which form relatively persistent deposits on the leaves and branches, e.g. Dieldrin, DDT and Endosulfan. However, during the last years, very promising results have been obtained with aerosol applications of Endosulfan and certain pyrethroids such as Permethrin, Decamethrin and Cypermethrin.
In the former periods most control operations were carried out by ground spray units. At present there is a strong tendency to replace groundspraying, at least partly, by aerial spraying. In connection to the latter both helicopters and fixed-wing aircraft are being used. One of the advantages of aerial spraying is that larger areas can be treated during one season than is possible by groundspraying.
Most operations carried out sofar were directed to dry savannas (the Sudan Savanna in West Africa and the Miombo woodland in East and South-east Africa) (see fig. 2.1). It is to be expected that as soon as most of the dry areas have been reclaimed in certain countries the spraying activities will be extended to the moister savanna areas (the Guinea savanna zone in West and North-central Africa). In this connection it should also be remarked that in most areas one cannot distinguish easily between dry and moist savannas because most types of habitat occur together (e.g. Doka woodland with G. morsitans submorsitans and riverine forest with G. tachinoids and G. palpalis).
