Effect of Environmental Temperature on the Vector Competence of Aedes Aegypti and Ae. Taeniorhynchus for Ockelbo Virus

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  • U.S. Army Medical Research Institute of Infectious Diseases, Fort Detrick, National Bacteriology Laboratory, Karolinska Institute, Frederick, Maryland, Sweden

Studies were conducted to determine the effect of environmental temperature on the ability of Aedes aegypti and Ae. taeniorhynchus to transmit Ockelbo (OCK) virus. Temperatures tested were 10°C, 17°C, 24°C, and a cyclic (10–24°C, mean = 17°C) regimen designed to mimic continuously temperatures to which a mosquito might be exposed in July and August in central Sweden. Both species were highly susceptible to oral infection, with no consistent association between incubation temperature and infection rates. However, dissemination of OCK virus to the hemocoel in infected mosquitoes was directly related both to the dose of virus ingested and to the extrinsic incubation temperature. After ≥ 14 days extrinsic incubation, once a disseminated infection was achieved, transmission by bite to a susceptible chick did not appear to be affected by either the initial dose ingested, the holding temperatures of 17°C, 24°C, nor the cyclic regimen. When re-fed, 93% (68/73) and 82% (67/82) of the disseminated Ae. taeniorhynchus and Ae. aegypti, respectively, transmitted virus. In contrast, when mosquitoes were held at 10°C, fewer disseminated Ae. taeniorhynchus (0/5) and Ae. aegypti (2/6) transmitted virus. There were no significant differences in infection, dissemination, or transmission rates for Ae. taeniorhynchus held at the cyclic temperature regimen vs. those held at a constant 17°C. Environmental temperature affected the vectorial capacity of Ae. aegypti and Ae. taeniorhynchus for OCK virus, with transmission occurring earlier and at a higher rate in mosquitoes held at higher temperatures.