Malaria control utilizing Bacillus sphaericus against Anopheles stephensi in Panaji, Goa

Area of Science:

• Medical Entomology
• Public Health
• Environmental Science

Background:

• Malaria remains a significant public health concern in endemic regions.
• Anopheles stephensi is a primary vector for malaria transmission in urban and semi-urban areas.
• Effective larval control is crucial for malaria prevention strategies.

Purpose of the Study:

• To evaluate the efficacy of Bacillus sphaericus as a biolarvicide against Anopheles stephensi.
• To compare the effectiveness of Bacillus sphaericus with the chemical larvicide temephos in a field setting.
• To assess the impact of larvicidal interventions on malaria incidence.

Main Methods:

• Weekly application of Bacillus sphaericus (1 g/m2) in Anopheles stephensi larval habitats (curing waters, masonry tanks, sump tanks).
• Comparison of habitat positivity and anopheline densities between Bacillus sphaericus treated areas and temephos treated areas.
• Monitoring of malaria incidence through slide positivity rate (SPR) and monthly parasite index (MPI).

Main Results:

• Bacillus sphaericus application led to a sharp decline in habitat positivity (0.13-8.0%) compared to temephos (2.2-30.6%).
• Significant reduction in anopheline densities was observed in Bacillus sphaericus treated habitats (0-7.3/10 dips) versus control habitats (0.9-53.0/10 dips).
• Lower malaria incidence (SPR 2.3-7.8%; MPI 0.18-1.44) was recorded in the Bacillus sphaericus treated area compared to the control area (SPR 14.3-25.5%; MPI 1.75-6.12).

Conclusions:

• Bacillus sphaericus is a highly effective biolarvicide for controlling Anopheles stephensi populations.
• Biological control with Bacillus sphaericus offers a superior alternative to chemical larvicides like temephos for malaria vector control.
• The use of Bacillus sphaericus can significantly contribute to reducing malaria transmission in endemic areas.