Insecticide susceptibility status of Phlebotomus argentipes, a vector of visceral leishmaniasis in different foci in three states of India.

BACKGROUND & OBJECTIVES Phlebotomus argentipes is the vector for visceral leishmaniasis in India. The development of resistance in kala-azar vector to DDT has been reported from various parts of India. The main objective of this study was to generate information on insecticides susceptibility status of P. argentipes to DDT, malathion and deltamethrin in different parts in three states of India. METHODS Phlebotomus argentipes were collected from different villages, identified and used to investigate the susceptibility status against DDT, malathion and deltamethrin as per the WHO standard methods. RESULTS Phlebotomus argentipes was resistant to DDT in different areas, viz. PHCs Murumgaon in Maharashtra; Ramgarh in Jharkhand; Kodah, Falka, Mahua and Lalganj in Bihar. In Phulwari Shareef PHC of Patna district in Bihar, DDT produced 89% mortality in P. argentipes, indicating resistant/tolerance (verification required) to DDT. The corrected percent mortality to malathion (5%) in different areas ranged between 98 and 100%; and to deltamethrin (0.05%) between 98.4 and 100%. The results showed that the tested P. argentipes are susceptible to malathion and deltamethrin. CONCLUSION Phlebotomus argentipes are still susceptible to malathion and deltamethrin, but resistant to DDT. The susceptibility status of P. argentipes should be monitored regularly in diversified situations to ascertain the judicious use of insecticides being used for indoor residual spraying in the programme for rational use of appropriate insecticide.