Entomological and rodent surveillance in plague-suspected areas during September 1994 and thereafter

Studies carried out in the states of Maharashtra, Gujarat, Uttar Pradesh and Union Territory of Delhi after the bubonic plague outbreak during 1994 revealed the presence of seven species of rodents, viz. Rattus rattus, R. norvegicus, Mus. musculus, Tatera indica, Suncus murinus, Bandicoota bengalensis and B. indica. The flea species encountered were Xenopsylla cheopis and X. astia. The X. cheopis and X. astia index recorded in different areas of Beed district of Maharashtra; Surat, Vadodra and Baruch districts in Gujarat and Varanasi district in Uttar Pradesh and their implications have been discussed. Insecticide suspectibility tests carried out against DDT, dieldrin, malathion and deltamethrin with X. cheopis collected from Maharashtra, Delhi and Varanasi revealed that this vector species is resistant to DDT and dieldrin but susceptible to malathion and deltamethrin. The prevalence and distribution of rodents species, high cheopis index and prevalence of Tatera indica just at the door steps of houses in village Mamla of Beed district provides highly congenital conditions for the intermingling of wild and domestic rodents and transfer of flea population from wild to domestic rodents and vice-versa. These conditions were found to be highly supportive for bubonic plague transmission in the district. The presence of Yersinia pestis antibodies in Rattus rattus collected from Beed, Surat and Varanasi areas are also indicative of bubonic plague in Beed and Varanasi and pneumonic plague in Surat during 1994.