Zoonotic visceral leishmaniasis is caused by transmission of a parasite, Leishmania infantum, from animals (mostly domestic dogs) by blood-sucking sandflies. In people, clinical symptoms of the disease, which is often fatal if left untreated, include fever, swollen liver and spleen, and anaemia.
Clive Davies from the London School of Hygiene and Tropical Medicine and colleagues from the University of Tabriz, Iran, fitted deltamethrin-impregnated collars to domestic dogs in 18 villages in Iran for the L Infantum transmission season. They hoped that the dog collars would discourage sandflies from feeding on dogs, which would in turn, cut the chance of people being infected with L infantum by sandfly bites. After 1 year, the authors measured the incidence of infection in children and in dogs, and compared these rates with those in villages outside the programme. Davies and colleagues estimate that dog collars resulted in a 42% reduction in transmission to children and a 54% drop in infection in dogs.
Collaring dogs offers an alternative to current control methods, such as dog culling and spraying houses with insecticide, both of which are logistically difficult to sustain and not completely effective. For example, in Brazil, the incidence of zoonotic visceral leishmaniasis has increased steadily during the past 10-20 years, despite spraying 200 000 houses and killing 20 000 dogs every year.
Clive Davies comments that "the protective effect of dog collars against Leishmania transmission was as good, or better, than that shown in dog culling trials".
Although collaring programmes would not prevent transmission of L Infantum from wild animals, such as jackals and foxes, they would offer a practical and effective way to reduce the burden of this disease.
Contact: Dr Clive Davies, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK; T) +44 (0) 1691 828 779; Mob) +44 (0) 77 6347 3528.