The effects of oviposition-site deprivation on longevity and bloodfeeding rate in Anopheles gambiae.

BACKGROUND

The African malaria mosquito, Anopheles gambiae, needs surface water in order to lay their eggs. In many parts of Africa, there are dry periods varying from days to months in length when suitable larval sites are not available and female mosquitoes experience oviposition-site deprivation (OSD). Previous studies have shown that egg-laying and egg-hatching rates were reduced due to OSD. Here, we assessed its effect on longevity and bloodfeeding rate of Anopheles gambiae. We predicted that OSD will increase mosquito longevity and the aptitude of mosquitoes to take additional blood meals; importantly, these changes will increase its vectorial capacity.

METHODS

To measure the effect of OSD, four treatments were utilized: two oviposition-deprived groups, one of which was bloodfed once (OBOD) and one that was bloodfed weekly (MBOD); a non-oviposition-deprived, weekly bloodfed control group (MBC); and a blood-deprived age-control group (BD). Mortality was assessed daily and bloodfeeding rate was measured at weekly intervals.

RESULTS

Under OSD, survival of female A. gambiae was reduced by 10-20%, reflecting reduction of the MBOD and OBOD groups from the MBC group, respectively. Likewise, bloodfeeding response during three weeks of OSD was reduced but the reduction varied as a function of time from the last blood meal.

CONCLUSIONS

These results indicate that OSD is expected to reduce A. gambiae vectorial capacity and that OSD alone does not act as cue used by female mosquitoes to switch into a dormant state of extended survivorship with reproductive quiescence.