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A preliminary study has shown that the marshy terrain and brackish water bodies associated with mangrove forests contributed profuse breeding of mosquitos in Vypeen island, causing a severe menace to the island population. A total of 14 species belonging to four genera viz, Aedes, Anopheles, Armigeres and Culex was recorded from different habitats. Culex sitiens was found to be the predominant mosquito in all the perennial breeding habitats. The extent of different habitats in the production of mosquitos, and its possible abatement, using environmental and/or biocontrol methods are discussed.

Prevalence of various aquatic vegetation and their role in supporting vector breeding were studied by drawing plant samples from natural fresh water habitats in Shertallai region which is endemic for Brugia malayi. As many as 30 aquatic plant species were identified in addition to the most abundant and preferred host plants such as Pistia stratiotes, Salvinia molesta and Eichhornia crassipes which are of major concern due to their contribution for vector proliferation. Fallow lands and paddy fields recorded relatively a higher number of plant species. Natural breeding of Mansonia, the vector mosquitos was observed in 16 of them. Using the data on the prevalence, proportion of samples positive for Mansonia breeding and immature density, two indices viz, natural hospitability Index (NH) and Mansonia host plant Index (MHI) were developed for each plant species. Ranking of these plants in relation to Mansonia breeding was done based on these indices. Monochoria vaginalis has been identified to be one of the most important auxiliary host plant. Three grasses viz, Hygrorhiza aristata, Sacciolepis interrupta and Leersia hexandra were found to support all the three species of Mansonia viz, Ma. annulifera, Ma. uniformis and Ma. indiana with considerable immature density. The inclusion of these plants for weed/vector control is emphasized.

Investigations on the biology of Phlebotomus papatasi were carried out under laboratory conditions at 28 +/- 2 degrees C and 80 +/- 1% RH. Fecundity of the female varied between 61 and 48 (mean 56.2 +/- 5.46) and the incubation period of eggs ranged from 7-9 (mean 7.81 +/- 0.61) days. The developmental duration of larvae and pupae varied from 24 to 31 (mean 28.57 +/- 2.71) and 9 to 11 (mean 10.38 +/- 1.51) days, respectively. The rate of insemination, determined from the females that laid fertile eggs, was found to be maximum when the females were three days old. Autogeny was observed from female sandflies, emerged from the larvae fed on animal liver powder. The duration of first and second gonotrophic cycles under ambient conditions was shortest in summer and longest in winter. Studies on adult longevity showed that the females fed on mouse blood survived for 6 to 27 days (mean 14 +/- 12.5 days).

The source of blood meal of wild caught Phlebotomid sandflies collected in areas around Pondicherry was identified using an agarose gel diffusion method. A total of 497 blood samples obtained from freshly engorged Phlebotomid sandflies were tested. Of these 66.8% were positive to human antisera, 29.2% to bovine antisera and the remaining 4.0% to avain antisera. The human blood indices of P. papatasi and P. argentipes were 0.91 and 0.04, respectively.

Mansonia annulifera, was recorded to be an endophilic species, preferring to rest indoors, while Ma. uniformis was exophilic, having a predilection for outdoor resting habitats, eg bushes and shrubs. Ma. indiana did not show a clear preference to either of these biotopes. In indoor resting collections, the unfed proportion of Ma. uniformis was significantly higher during post-dusk compared to day hours (p < 0.05), indicating that this exophilic species enters houses during dusk hours for feeding. The full fed proportion was higher during day hours compared to dusk/night hours. The semigravid proportion showed a significant reduction during post-dusk hours (p < 0.05). These findings suggest that after having a blood-meal this species rest indoors and leave the houses for outdoor resting sites during the dusk hours on the subsequent night.

Effectiveness of two types of granular formulations of fenthion (Baytex) was evaluated in controlling the breeding of Mansonia mosquitos in polluted pond habitats. Calcium carbonate and sand granular formulations, when applied at 2.50 g/m2 surface area with an average depth of 0.5 m were found to be effective in keeping the habitats completely free from Mansonia breeding for 14 days and 18 days respectively. Release of insecticide was slow and the effective duration of control after a single application was relatively longer in the sand formulation when compared to the calcium carbonate formulation. Single application of calcium carbonate and sand granular formulations of fenthion could effectively prevent Mansonia adult emergence for 23 and 30 days, respectively in polluted pond habitats, without causing any adverse effect on non-target insects.

Annual and biannual mass single dose diethylcarbamazine citrate (DEC) at 6 mg/kg body weight was administered to people in a Brugia malayi endemic area in Shertallai part of Kerala, India, in 1987 and 1988. The coverage of population ranged between 41.33% and 66.01% in different rounds. The highest percentage of treated population developing side reactions was 8.4%. Both annual and biannual regimens were effective in reducing the microfilaria prevalence significantly from 4.90% to 1.23% and from 6.27% to 0.62% respectively and the incidence of infection was minimal in the adult population and zero among children. There was significant reduction in mean microfilaria count in both annual (81.08%) and biannual (98.00%) areas. Marked reduction in the proportion of high density carriers and infectivity index of the population after DEC therapy was also observed. Beneficial effect of mass single dose DEC on clinical cases of filariasis was evident from the reduction in the prevalence of acute manifestations, recent edema cases and the proportion of chronic cases with acute episodes. Results obtained from mass treatment areas were compared with those of the control area.