Bionomics of malaria vectors in two physiographically different areas of the epidemic-prone Thar Desert, north-western Rajasthan (India)

Entomological and parasitological investigations were carried out on malari a vectors and disease prevalence in two sets of villages, the highly irriga ted Indira Gandhi Nahar Pariyojana (IGNP) command-area villages (Madassar a nd Awai), and the truly desertic non-command (unirrigated) area villages (K anasar and Khetusar), located in different ecological conditions in the Tha r Desert, north-western Rajasthan (India). Malaria prevalence, as determine d through sustained fever surveys, was higher in the IGNP villages with a s lide positivity rate (32%) marginally more than that of the unirrigated vil lages (25.5 %), but with a high proportion of Plasmodium falciparum (76.6%) in the former villages as compared to the latter (16.6%). Anopheles stephe nsi, A. culicifacies and A. subpictus were amongst the eight anopheline spe cies collected from all the four villages which were found positive for mal arial parasites. Anopheles stephensi was the predominant species in the uni rrigated villages ( > 95%), although in the irrigated villages A. culicifac ies was also found. The major ecological changes associated with irrigation in the Thar Desert are understood to be playing an important role in accen tuating the transmission of malaria by improving vector breeding conditions and survival in an otherwise hostile arid environment. (C) 2001 Academic P ress.