Development of physiological resistance and its stage specificity in Culex quinquefasciatus after selection with deltamethrin in Assam, India

The study investigated the development and stage specificity of physiological resistance to insecticides in a colony of Culex quinquefasciatus Say (Diptera: Culicidae) mosquitoes, which are vectors of bancroftian filariasis in India, after selection with deltamethrin. Resistance was selected by exposing the larvae to the concentration of deltamethrin that caused 50 percent mortality in the tested population (i.e., LC50). Under continuous selection pressure, the LC50 increased steadily in subsequent generations. The estimated LC50 for the F0 generation was 0.409 μg/L; the LC50 first displayed a substantial increase in the F5 generation (5.616 μg/L) and reached 121.902 μg/L in the F10 generation. The objective of this study was to establish a deltamethrin-resistant colony to develop a research programme that will study the evolution of physiological resistance patterns and stage-specific resistance responses in Cx. quinquefasciatus larvae and adults under laboratory conditions. An approximately 298-fold increase in resistance was recorded after 10 generations, as evidenced by the resistance ratio (RR50). The progress and effect of the selection pressure in the adult stage was monitored with the World Health Organisation (WHO) diagnostic test. The mortality, as observed using the WHO diagnostic test, declined significantly from the F5 generation (85 percent) onwards and the highest rate of survival (65 percent) was observed in the F10 generation.

Parasitosis: a study among Nepali children in the district of Darjeeling.

A cross-sectional study carried out among 370 school-going children of the Nepali community, aged 5-10 years, in the Siliguri subdivision of Darjeeling district revealed the prevalence of parasitic infestation to be 51.4 per cent of which 28.2% and 23.2% had single and multiple parasitism respectively. In the group of single parasitism, A. lumbricoides was the commonest infestation (31.73%) and in multiple parasitisms, A. lumbricoides and T. Trichiura combination was found to be the most prevalent (36.05%). A significant statistical association was observed in the decrease of worm infestation rate among children with the increasing educational status of their mothers. The study also revealed that 19.73% and 18.91% of the mothers had no knowledge about mode of transmission and prevention of worm infestation respectively.