Seasonal prevalence of malaria vectors and its relationship with malaria transmission in three physiographic zones in Uttaranchal State, India.

Anopheles minimus (Diptera : Culicidae) has been reported as a principal malaria vector in district Nainital1. An. fluviatilis and An. culicifacies (Diptera: Culicidae) were later incriminated as malaria vectors and An. minimus was reported virtually absent2–4. Recently, in forest ecotype, An. fluviatilis has been incriminated as malaria vector and its sibling species ‘S’, which is a potential vector of malaria, was recorded for the first time in this area5. The data collected from District Malaria Office for the years 1998 and 1999 revealed that the annual parasite incidence (API) and slide positivity rate (SPR) was 0.2 and 0.3, and 1.0 and 1.1, respectively in Nainital and 1.0 and 0.6, and 1.3 and 1.0, respectively in Udham Singh Nagar districts. The transmission dynamics of malaria in such geographical zones is also likely to differ requiring specific vector control strategies. Therefore, the present study was undertaken in three different zones in Kumaon region such as hilly, bhabar (foothill area with very low water table) and terai (plain area with high water table) zones from April 1998 to March 1999 to study the seasonal prevalence of vectors and parasite load in the community.