Background: The most important factor for effective zooprophylaxis in reducing malaria transmission is a predominant population of a strongly zoophilic mosquito, Anopheles arabiensis. The feeding preference behaviour of Anopheline mosquitoes was evaluated in odour-baited entry trap (OBET).
Methods: Mosquitoes were captured daily using odour-baited entry traps, light traps and hand catch both indoor and in pit traps. Experimental huts were used for release and recapture experiment. The mosquitoes collected were compared in species abundances.
Results: Anopheles arabiensis was found to account for over 99% of Anopheles species collected in the study area in Lower Moshi, Northern Tanzania. In experimental release/capture trials conducted at the Mabogini verandah huts, An. arabiensis was found to have higher exophilic tendency (80.7%) compared to Anopheles gambiae (59.7%) and Culex spp. (60.8%). OBET experiments conducted at Mabogini collected a total of 506 An. arabiensis in four different trials involving human, cattle, sheep, goat and pig. Odours from the cattle attracted 90.3% (243) compared to odours from human, which attracted 9.7% (26) with a significant difference at P = 0.005. Odours from sheep, goat and pig attracted 9.7%, 7.2% and 7.3%, respectively. Estimation of HBI in An. arabiensis collected from houses in three lower Moshi villages indicated lower ratios for mosquitoes collected from houses with cattle compared to those without cattles. HBI was also lower in mosquitoes collected outdoors (0.1-0.3) compared to indoor (0.4-0.9).
Conclusion: In discussing the results, reference has been made to observation of exophilic, zoophilic and feeding tendencies of An. arabiensis, which are conducive for zooprophylaxis. It is recommended that in areas with a predominant An. arabiensis population, cattle should be placed close to dwelling houses in order to maximize the effects of zooprophylaxis. Protective effects of human from malaria can further be enhanced by keeping cattle in surroundings of residences.