Relationship between Anopheles fluviatilis & A. stephensi (Diptera: Culicidae) catches & the prevalence of malaria cases at Kalsi area in Dehradun district (Uttaranchal).

BACKGROUND & OBJECTIVE Though the relationship between mosquito density and transmission of malaria in different regions of the country is known, no studies are available on the relationship between mosquito catches and malaria cases in Kalsi area of Dehradun district in Uttaranchal. Hence, the present study was done to evaluate the role of anopheline mosquitoes catches and prevalence of malaria cases in this area. METHODS During three consecutive years (2000-2003) mosquitoes were collected from 10 villages in Kalsi area twice a month, during the morning and evening hours. Identification of anopheline mosquitoes was done. Indoor collected female mosquitoes were dissected to see infection. Sporozoites were fixed and stained. Data on temperature and rainfall were also collected. RESULTS As many as 10 species of anophelines were collected during three consecutive years - January 2000 to December 2002 at Kalsi block in district Dehradun (Uttaranchal). Proportion of the total anopheline species as well as the abundance of Anopheles stephensi was found more in the year 2002 than in 2000 and 2001. Incrimination studies revealed malarial infection (sporozoite positive) in A. fluviatilis and A. stephensi. Of the 5450 blood smears examined, only 50 (0.91%) were found positive for malarial parasite i.e., Plasmodium vivax. There was no case of P. falciparum during the study period. Highest slide positive rate (SPR) of 1.107 per cent was recorded in 2002 while in 2001, highest month-wise malaria positive cases were recorded in the month of August. September shared highest positive cases during 2000 and 2002. While correlating a relationship between mosquito catch especially infected ones and monthly parasite incidence, the density of A. stephensi showed significantly high correlation (r = 0.819; P<0.001). A slight variation in this type of relationship was seen in A. fluviatilis. Both temperature and rainfall were found to be positively correlated with malaria incidence. INTERPRETATION & CONCLUSION Our findings showed that A. fluviatilis and A. stephensi played a significant role in transmission of malaria in Kalsi area of Dehradun.