Abstract
BackgroundThe 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.MethodsTo 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.ResultsUnder 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.ConclusionsThese 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.
Highlights
The African malaria mosquito, Anopheles gambiae, needs surface water in order to lay their eggs
These results suggest that oviposition-site deprivation (OSD) by itself does not serve as a cue used by mosquitoes to switch their physiology from reproduction to long-term survival
All three treatments were again relatively high and not significantly different from one another (P > 0.18, Exact test; Figure 3). These results suggest that bloodfeeding rates in mosquitoes subjected to OSD is reduced compared with non-deprived females that undergo normal gonotrophic cycles
Summary
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). We assessed its effect on longevity and bloodfeeding rate of Anopheles gambiae. Larval sites are unavailable during short and long dry spells when mosquitoes endure oviposition-site deprivation (OSD). The effects of OSD on the mosquito and her capacity to transmit disease are poorly understood. In areas such as the Sahel, when no larval sites are available during the dry season for two to seven months, mosquitoes must ensure their survival until the resumption of rains [1,2,3,4]. Infection of the vector requires at least one bloodmeal followed by oviposition (gonotrophic cycle), and disease transmission further requires survival of the female for enough time to become infectious before she can inoculate the pathogen into a new host [10,11]
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