Eco-epidemiological characteristics of an unstable peri-urban focus of falciparum malaria.

Two fever surveys were carried out in Shahbad dairy, Delhi in the post-monsoon months of October and November, 1996. Shahbad dairy is a peri-urban locality in the northern periphery of Delhi. The prevalence of fever was found to be 11.6% in October and 2% in November. In the two surveys a total of 21 (28%) fever cases were found infected with malaria (17 with P. falciparum and 4 with P. vivax). The prevalence of malaria in the surveyed population was lower (25%) in October than in November (36.8%). More adults and males suffered from malaria than other age groups and the females. In November the mean asexual parasitaemia, for P. falciparum infection, sharply declined among 5-14-years old children by 68%, but among adults it increased by 32%. Collection of adult mosquitoes, from human houses, revealed the presence of 5 species of anopheline mosquitoes comprising Anopheles culicifacies, An. stephensi, An. annularis, An. subpictus, and An. nigerrimus, and a culicine mosquito Culex vishnui complex. Extensive breeding of these mosquitoes was detected in the vicinity of Shahbad dairy. Characteristic ecological support system (ESS) for malaria transmission was identified at the peri-urban focus of Shahbad dairy.