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Severe outbreaks of malaria occurred in the coastal villages of the Candolim Primary Health Centre (PHC) of Goa, India, in 1993 and 1994. These outbreaks were associated with accelerated construction activity with an influx of migrant laborers. The weekly application of Bacillus thuringiensis var. israelensis (B.t.i.) strain 164 at 1 g/m2 and introduction of the indigenous larvivorous fish Aplocheilus blocki in major breeding habitats of Anopheles stephensi replaced ongoing DDT spraying and pyrethrum fogging in June 1994. The objective of this study was to evaluate the effects of B.t.i. and larvivorous fish on An. stephensi and subsequent transmission of malaria in the Candolim PHC, Goa, India. In 1995 the populations of an. stephensi in larger habitats (habitats with immatures: t = 5.19, P = 0.0017; immature density: t = 3.57, P = 0.007) and smaller habitats (habitats with immature: t = 3.86, P = 0.005; immature density: t = 4.93, P = 0.002) and malaria incidence declined substantially (malaria cases: chi 2 = 712, P < 0.001; slide positivity rate: chi 2 = 10.36, P < 0.001; annual parasite index; chi 2 = 15.1, P < 0.001), whereas the incidence of malaria continued to increase in other nearby towns.

In a locality (Sada) of Vasco City, Goa, India, that was highly infested with mosquitoes, weekly spraying of Bacillus sphaericus (strain 101, serotype H 5a 5b) at the rate of 1 g/m2 in polluted water habitats, viz, surface drains, cess pits, cess pools, and septic tanks, resulted in a sharp decline in the immature and adult populations of Culex quinquefasciatus. The per man-hour adult densities, percent habitat positivity, and immature densities were significantly lower (P < 0.001) in the treated area compared to the control area through out the study period.

Bacillus thuringiensis (H-14), strain 164 (Bactoculicide) when applied at 1 g/m2 surface area successfully controlled Anopheles stephensi breeding in construction sites, abandoned overhead tanks, and curing waters. Subsequent to application, no pupal production was observed in these habitats for 3, 18, and 21 days, respectively. Based on these findings, inclusion of Bactoculicide in the bioenvironmental vector control strategy is suggested and fortnightly spraying in construction sites at 1 g/m2 surface area is recommended for the containment of vector breeding. However, frequent retreatment of abandoned overhead tanks would be uneconomical and operationally impractical.

In a large malaria endemic area in Panaji city, Goa, India, the weekly application of the biolarvicide Bacillus sphaericus (Strain 101, Serotype H 5a 5b) at the rate of 1 g/m2 in the main Anopheles stephensi larval habitats, viz., curing waters, masonry tanks, and sump tanks (under construction), from April to December 1993 resulted in a sharp decline in the habitat positivity (range 0.13-8.0%) as compared with the rest of the Panaji (range 2.2-30.6%) where temephos (Abate) was used as the larvicide. Bacillus sphaericus spraying also led to a significant decline in anopheline densities in positive habitats (range 0-7.3/10 dips) as compared with control habitats (range 0.9-53.0/10 dips). Concurrently, malaria incidence observed in the experimental area (slide positivity rate [SPR] range 2.3-7.8%; monthly parasite index [MPI] range 0.18-1.44) was lower than in the control area (SPR range 14.3-25.5%; MPI range 1.75-6.12).