ABSTRACT
In the past Assam was devastated by epidemics of Kala-azar. However, inspite of resurgence of this disease in Bihar and neighbouring areas Assam has remained untouched by this disease since the mid 1950s so far. The study undertaken in Kamrup district, sought to provide an entomological explanation for Assam's present freedom from Kala-azar. Sandfly collections were made in 15 villages. Three different methods were used; namely hand collections by aspirator and torch, sticky traps and examination of soft parts of cattle in the villages for mating swarms. 1049 sandflies were collected which did not include any specimens of P. argentipes. The vector of Indian Kala-azar has either been eliminated by continuous insecticide spraying in this high P. falciparum, and chloroquine resistance area or reduced to such low levels of prevalence that routine sampling methods are unable to reveal its presence. The implications of this finding are discussed in relation to Kala-azar control in India, in general.
Subject(s)
Animals , Cattle , Humans , India , Insect Control/methods , Insect Vectors , Leishmaniasis, Visceral/prevention & control , Phlebotomus , Population Density , Random AllocationABSTRACT
S. shorttii, a common phlebotomine sandfly species of Assam, was tested for susceptibility to commonly used insecticides, D.D.T., malathion and Fenitrothion in Kamrup district, Assam. Tests carried out by WHO test kits showed 100 per cent mortalities against discriminating concentrations of malathion (5 per cent) and Fenitrothion (1 per cent). With D.D.T., in 1 hr. exposure mortalities recorded were 54.5 and 64.4 per cent, whereas in 24 hr. exposure mortalities were 75 per cent and 90 per cent. The area has been under continuous D.D.T. spraying since the beginning of NMEP in 1958, and high selection pressure appears to have precipitated D.D.T. resistance in this partly exophilic species.