Abstract:
BACKGROUND : Mosquito lifespan can influence the circulation of disease causing pathogens because it affects the time
available for infection and transmission. The life-cycle of mosquitoes is determined by intrinsic and environmental
factors, which can include the availability of hosts and suitable resting environments that shelter mosquitoes from
extreme temperature and desiccating conditions. This study determined the parity rates (an indirect measure of
survival) and plant resting preference of vectors of Rift Valley fever (RVF) in northeastern Kenya.
METHODS : Resting mosquitoes were trapped during the rainy and the dry season using a Prokopack aspirator from
vegetation, whereas general adult populations were trapped using CDC light traps. At each site, sampling was
conducted within a 1 km2 area, subdivided into 500 × 500 m quadrants and four 250 × 250 m sub-quadrants from
which two were randomly selected as sampling units. In each sampling unit, plants were randomly selected for
aspiration of mosquitoes. Only Aedes mcintoshi and Ae. ochraceus were dissected to determine parity rates while all
mosquito species were used to assess plant resting preference.
RESULTS : Overall, 1124 (79 %, 95 % CI = 76.8–81.1 %) mosquitoes were parous. There was no significant
difference in the number of parous Ae. mcintoshi and Ae. ochraceus. Parity was higher in the rainy season
than in the dry season. Daily survival rate was estimated to be 0.93 and 0.92 among Ae. ochraceus and Ae.
mcintoshi, respectively. Duosperma kilimandscharicum was the most preferred plant species with the highest
average capture of primary (3.64) and secondary (5.83) vectors per plant, while Gisekia africana was least
preferred.
CONCLUSION : Survival rate of each of the two primary vectors of RVF reported in this study may provide an indication
that these mosquitoes can potentially play important roles in the circulation of diseases in northern Kenya. Resting
preference of the mosquitoes in vegetation may influence their physiology and enhance longevity. Thus, areas with
such vegetation may be associated with an increased risk of transmission of arboviruses to livestock and humans.
