Susceptibility of the sandfly Phlebotomus argentipes Annandale and Brunetti (Diptera: Psychodidae) to insecticides in endemic areas of visceral leishmaniasis in Bihar, India.

We present the results of susceptibility tests conducted on the sandfly Phlebotomus argentipes, the vector of visceral leishmaniasis in India. Adult P. argentipes insects were collected from 42 villages in 6 districts of the state of Bihar, India, as follows: Patna, Vaishali, Muzaffarpur, Samastipur, Sheohar, and Sitamarhi. These adult insects were exposed to 4% DDT-, 5% malathion-, and 0.05% deltamethrin-impregnated papers using a WHO test kit by following the standard procedures. In 16 (38.1%) of 42 villages surveyed, the P. argentipes populations developed resistance to DDT. Susceptibility tests using the organophosphate malathion in 22 villages revealed that in 1 (4.5%) village, the species developed resistance to this insecticide. P. argentipes was, however, highly susceptible to the synthetic pyrethroid deltamethrin. For long-term vector control of P. argentipes, it will be necessary to overcome the threat of insecticide resistance in this species.