The Vector Competence and Vectorial Capacity of Aedes albopictus for Ross River Virus in the United States as a Function of Temperature

Abstract

Ross River virus (RRV) is a medically significant arbovirus endemic to Australia where it causes an average of 5000 reported human cases per year. Due to concern for possible transmission outside of its endemic range, we examined the vector competence and vectorial capacity of RRV by Aedes albopictus (Skuse 1894) to contribute to risk assessments for outbreaks in the United States. We tested Ae. albopictus mosquitoes exposed to RRV at three temperatures and five time points post-infection for infection and dissemination. We also collected saliva from exposed individuals incubated at the same three temperatures to determine the presence of viral RNA. Additionally, we assessed the impact of viral infection on life expectancy as a function of temperature. Rates of infection were unaffected by time and temperature and 89.3% of individuals were infected. 85-100% of infected individuals displayed dissemination by day 7 at all temperatures. The extrinsic incubation period as determined by the saliva collection was approximately 6 days and 78.6-100% of individuals tested expressed salivary viral RNA at some point in the experiment which is comparable to the rates of overall infection. The vectorial capacity of RRV with Ae. albopictus as a vector ranged from 10.23-23.37 indicating that these mosquitoes are competent potential vectors for RRV. Due to prior outbreaks RRV has caused outside of its endemic range, these findings warrant further investigation in the transmission potential of RRV in the United States. Author SummaryThe last 30 years has seen a steady increase in mosquito-borne illness globally, much of which has been driven by viruses such as dengue establishing in new areas as a consequence of the spread of its primary vectors and environmental changes. In order to mitigate the continued increase in the prevalence of mosquito-borne illness, it is necessary to determine which viruses are likely to spread beyond their native range. Ross River virus (RRV) is a mosquito-borne virus which, while nonlethal, commonly causes a litany of debilitating side-effects for extended periods of time. RRV is endemic to Australia, however the recent introduction of a known RRV vector to California as well as the widespread prevalence of a suspected RRV vector, Ae. albopictus, across the country, could prime RRV for an outbreak in the continental United States. As part of a risk assessment for the outbreak potential of RRV in the continental United States, we investigated the vector competence and vectorial capacity of Ae. albopictus. We find that this species is a competent vector for this virus across a range of relevant temperatures.