Vector abundance and behaviour in an area of low malaria endemicity in Bataan, the Philippines

Abstract

The vectorial importance of known and potential vectors in Morong, Bataan, Philippines was assessed based on human and animal baited collections of adult mosquitoes and on larval collections. Anopheles flavirostris, the principal vector in the Philippines, was the most abundant among human landing catches, followed by An. maculatus sensu lato (s.l.). Both showed similar seasonal abundance with a peak during the early drier part of the year, which coincided with the peak in malaria cases. Both An. flavirostris and An. maculatus s.l. fed throughout the night with the broad peak of capture from 00:00 to 04:00 and from 22:00 to 00:00, respectively. The two species had similar parous rates (0.76 and 0.72, respectively) giving an average life span equivalent to four feeding cycles. Neither vector was abundant with average human landing rates on collectors of 0.6 and 0.4 mosquitoes per person per night, respectively over the study period. An. maculatus s.l. showed a stronger preference for outdoor feeding compared to An. flavirostris. An. maculatus s.l. was markedly zoophilic with a biting rate on water buffalo 50 times the human landing rate. An. flavirostris was less zoophilic with a corresponding ratio of 7.5. It was concluded that in this area, An. flavirostris is the principal vector. The combination of localised transmission, late night biting pattern and localised breeding sites of An. flavirostris suggest that the use of bed nets and environmental management are relevant control measures that can be implemented through community participation.