Successful application of deltamethrin pour on to cattle in a campaign against tsetse flies (Glossina spp.) in the pastoral zone of Samorogouan, Burkina Faso.

1,500-2,000 head of cattle were treated with deltamethrin 1% Spot On in an area of high tsetse densities, notably of Glossina morsitans submorsitans. After four treatments at monthly intervals, the time between two treatments was increased to two months. 11 months after the commencement of the campaign the fly population had decreased from initially 54.2 flies/trap/day to densities varying between 0.06-2.0 flies/trap/day, mostly G. palpalis gambiensis. Blood-meal analysis showed that this species was surviving in limited areas, mainly feeding on monitor lizards; consequently it is unlikely that this species can be eradicated solely by the use of cattle treated with a pyrethroid. The resistance of Trypanosoma congolense to all commercially available trypanocides necessitated the epidemiological monitoring of calves which were born after the start of the campaign in order to reasses the real challenge. The risk of new infections was low, basically due to contracts between the cattle and tsetse outside the ranching area. A weight increase from 122.3 kg to 213.6 kg of calves aged 6-12 months was recorded from October 1993 to October 1994. An average daily weight gain of more than 400 g was observed from the end of April 1994 to the beginning of August 1994.

The residual effect of deltamethrin Spot On when tested against Glossina palpalis gambiensis under fly chamber conditions.

Groups of single zebu cattle were exposed to infestations of the tsetse fly Glossina palpalis gambiensis in fly chambers following treatment with a pour on formulation of deltamethrin, Coopers* Spot On. During the experiment one animal was maintained in a stall, the other exposed at intervals to sunlight. Both mortality and knockdown of exposed flies was demonstrated. Mortality rates of greater than 90% were recorded during the period 0-20 days after treatment and values in excess of 50% during the period, 41-59 days after treatment. Knockdown was more marked with rates in excess of 90% and 65% being recorded for respectively 45 and 75 days after treatment. Exposure to sunlight did not significantly effect the performance of Spot On. Flies were observed to repeatedly land on the deltamethrin treated cattle, so contributing to the overall pick-up of effective concentrations of the chemical. It was considered that this effect of the chemical could considerably reduce the risk of transmission of trypanosomosis from the start of a tsetse campaign.

Simultaneous control of ticks and tsetse flies in Satiri, Burkina Faso, by the use of flumethrin pour on for cattle.

Treatments of 2000 cattle at monthly intervals with flumethrin pour on (1 mg active ingredient/kg b.w.) resulted in a rapid decrease of African Animal Trypanosomosis (AAT). After an initial curative treatment of the sentinel herd with diminazene aceturate (7 mg/kg b.w.) only positive cases were treated. Three applications of flumethrin were sufficient to reduce the prevalence of AAT to below 5%. Apart from a slight increase at the end of the first year the infection rate varied between 0 and 5%. A tsetse population disappeared from a heavily infested habitat after six treatments. The average tick infestation was 3-10 times lower than in a control site inspite of the repeated use of another acaricide. Between 3282 and 8624 animals were treated five times in the second year at intervals of about two months. 130 monoconical insecticide impregnated traps were deployed in habitats which were inaccessible for the cattle. The highest infection rate of the sentinel herd was 1.4%. Among another 150 eartagged cattle scattered over a district of about 1000 m2 the prevalence of AAT dropped to 4.8% at the end of the second year. Emphasis is put on an active and financial participation of the rural communities to ensure a viable campaign and good prospects of a taking over by local organizations once the external interventions have stopped.

Effects of Flumethrin Pour-on against Glossina palpalis gambiensis (Diptera, Glossinidae).

1920 males and females of Glossina palpalis gambiensis were fed 3 times on a Zebu treated with Flumethrin Pour-on. This resulted in a significant increase of the mortality and abortion rate of the flies. The fly-specific effects of Flumethrin Pour-on were time-dependent: Clear effects on the performance of the flies were observed during the first 20 days after treatment of the Zebu; an initial 90% "knock down" effect decreased to 40% during the first 15 days.