Estimation of Vectorial Capacity of Anopheles dirus (Diptera: Culicidae) in a Forest-Fringed Village of Assam (India)

Abstract

To estimate the vectorial capacity of Anopheles dirus, the main vector of forest malaria in the northeastern region of India, in order to gain an understanding of entomological factors related to malaria transmission in forest-fringe areas of Assam, India, an isolated village in the tropical rain forest-fringed area in the district of Dibrugarh, Assam, under the influence of An. dirus alone was studied. Data on various entomological variables required for computation of the vectorial capacity were generated in each month from June 1999 to May 2000 in the field using standard techniques. Malaria prevalence was also studied during the same period in the study village and correlated with the estimated vectorial capacity of An. dirus. Vectorial capacity of An. dirus was highest, 0.779 for Plasmodium vivax (Pv) and 0.649 for Plasmodium falciparum (Pf), during the hot-monsoon season (June-September) and decreased to 0.08 (Pv) and 0.07(Pf) in the temperate postmonsoon season (October-November) before attaining zero values in the cool-dry season (December-February). With increasing temperature in the temperate premonsoon season (March-May), vectorial capacity recorded was 0.119 and 0.82 for Pv and Pf, respectively. Significant positive correlation was seen between the estimated vectorial capacity of An. dirus and the number of new Pf (r = 0.86, p < 0.001) and Pv (r = 0.69, p < 0.02) cases in the study village in different months. Thus, this study highlights the pattern of malaria transmission by An. dirus in a forest-fringe area of Assam that begins in March, peaks in July/August, subsides by November, and remains interrupted between December and February. Measures for controlling malaria in forest-fringe areas should be scheduled accordingly.

Revision of the Leucosphyrus group of Anopheles (Cellia) (Diptera, Culicidae)

“…In an isolated village in a tropical rain forest-fringe area in Assam, India, the vectorial capacity of An. baimaii for P. vivax was higher than for P. falciparum during the monsoon season, decreasing in post monsoon and reaching zero in the cold and dry season (Prakash et al 2001). In Naga Hills, India, the prevalence of malaria is related to the vector density thus it was higher in localities closer to the forest where An.…”

“…leucosphyrus , An. baimaii (Rahman et al 1977;Rosenberg & Maheswary 1982b;Dutta et al 1991;Prakash et al 2001), An. dirus (Eyles et al 1964;Scanlon & Sandhinand 1965;Sloof & Verdrager 1972;Ismail et al 1974Ismail et al ,1975Wilkinson et al 1978;Deng et al 1982;Trung et al 2004), and An.…”

The Global Public Health Significance of Plasmodium vivax

“…P. vivax and P. falciparum are commonly found in An. baimaii (Sallum et al, 2005;Obsomer et al, 2007), but original sources do not differentiate the members of the Dirus Complex (Prakash et al, 2001). An.…”

“…The vectorial capacity of An. dirus for P. vivax has been estimated (Prakash et al, 2001). Experimental infection from humans (Wirtz et al, 1985), monkeys (Collins et al, 2009) and membrane feeding has been shown (Coleman et al, 2004;Junkum et al, 2005).…”

Diversity and seasonal densities of vector anophelines in relation to forest fringe malaria in district Sonitpur, Assam (India)

“…is responsible for hyper-endemic malaria (Rosenberg and Maheswari 1982) and its importance as an efficient malaria vector in the northeastern states of India was well documented (Sen et al 1973;Dutta et al 1989). Prakash et al (1997) reported that deep forest areas in northeastern India offer favourable breeding grounds for this species and that the abundance is determined by the pattern of rainfall. Hence, the villages near the forest, which are under the influence of An.…”