The potential for dengue in South Africa: vector competence tests with dengue 1 and 2 viruses and 6 mosquito species

Abstract
Six mosquito species, selected because their prevalence, distribution and ecology favoured them as potential vectors of dengue (DEN) in South Africa, were tested for vector competence with DEN 1 and 2 viruses. After intrathoracic inoculation with DEN 1, head squash infection rates (HSIRs) by the indirect fluorescent antibody test were 92-100% in all species except Aedes demeilloni, for which rates were < 40%. After an infective blood meal containing DEN 1 and DEN 2 virus respectively, Ae. demeilloni, Ae. simpsoni and Eretmapodites quinquevittatus were refractory to infection, while the 3 other species became infected. Five populations of Ae. aegypti each 'transmitted' both serotypes into capillary tubes. With DEN 1, HSIRs and transmission rates (TRs) varied from 11% to 54% and 67% to 100%, while with DEN 2 they ranged from 19% to 46% and 71% to 86%. The mean vector competence index (VCI) was highest for Durban (0.47 for DEN 1 and 0.34 for DEN 2), while VCIs for the remaining populations varied from 0.13 to 0.28 (DEN 1) and 0.18 to 0.23 (DEN 2). With DEN 1, HSIRs for Ae. strelitziae and Ae. furcifer were 33% and 3% respectively, but no transmission occurred. With DEN 2, results for Ae. strelitziae were HSIR = 56%, TR = 29% and VCI = 0.16, while values for Ae. furcifer were HSIR = 12%, TR = 50% and VCI = 0.06. It is concluded that populations of Ae. aegypti are potentially the best vectors for both serotypes of the virus and that the Durban population could act as the most efficient vector in an urban or peri-urban epidemic.(ABSTRACT TRUNCATED AT 250 WORDS)