Pyrethroid treatment of cattle for tsetse control: reducing its impact on dung fauna.
BACKGROUND
African trypansomiases of humans and animals can be controlled by attacking the vectors, various species of tsetse fly. Treatment of cattle with pyrethroids to kill tsetse as they feed is the most cost-effective method. However, such treatments can contaminate cattle dung, thereby killing the fauna which disperse the dung and so play an important role in soil fertility. Hence there is a need to identify cost-effective methods of treating cattle with minimal impact on dung fauna.


RESULTS
We used dung beetles to field bioassay the levels of dung contamination following the use of spray and pour-on formulations of deltamethrin, applied to various parts of the body of cattle in Zimbabwe. Results suggested that dung was contaminated by contact with insecticide on the body surface as the cattle defecated, and by ingestion of insecticide as the cattle licked themselves. Death of dung beetles was reduced to negligible levels by using only the spray and applying it to the legs and belly or legs alone, i.e., places where most tsetse feed.


CONCLUSIONS
The restricted applications suitable for minimising the impact on dung fauna have the collateral benefits of improving the economy and convenience of cattle treatments for tsetse control. The demonstration of collateral benefits is one of the surest ways of promoting environmentally friendly procedures.
Natural Resources Institute, University of Greenwich, Chatham, United Kingdom; South African Centre for Epidemiological Modelling and Analysis, University of Stellenbosch, Stellenbosch, South Africa.
Glyn A
GA
Vale
South African Centre for Epidemiological Modelling and Analysis, University of Stellenbosch, Stellenbosch, South Africa.
John W
JW
Hargrove
Division of Tsetse Control, Harare, Zimbabwe.
Andrew
A
Chamisa
Natural Resources Institute, University of Greenwich, Chatham, United Kingdom.
Ian F
IF
Grant
Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Warwick Medical School, University of Warwick, Coventry, United Kingdom.
Stephen J
SJ
Torr
D000818:Animals; D002417:Cattle; D001517:Coleoptera / Q000187:drug effects; D005243:Feces / Q000469:parasitology*; D007300:Insect Control / Q000379:methods*; D007306:Insecticides / Q000494:pharmacology*; D009570:Nitriles / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology*; D015030:Zimbabwe
D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin