The wMel strain of Wolbachia Reduces Transmission of Zika virus by Aedes aegypti

Abstract

Zika virus (ZIKV) is causing an explosive outbreak of febrile disease in the Americas. There are no effective antiviral therapies or licensed vaccines for this virus, and mosquito control strategies have not been adequate to contain the virus. A promising candidate for arbovirus control and prevention relies on the introduction of the intracellular bacterium Wolbachia into Aedes aegypti mosquitoes. This primarily has been proposed as a tool to control dengue virus (DENV) transmission; however, evidence suggests Wolbachia infections confer protection for Ae. aegypti against other arboviruses. At present, it is unknown whether or not ZIKV can infect, disseminate, and be transmitted by Wolbachia-infected Ae. aegypti. Using Ae. aegypti infected with the wMel strain of Wolbachia that are being released in Medellin, Colombia, we report that these mosquitoes have reduced vector competence for ZIKV. These results support the use of Wolbachia biocontrol as a multivalent strategy against Ae. aegypti-transmitted viruses.

Figure 1. Vector competence of WT and (COL)wMel mosquitoes orally infected with 6.02 log₁₀ PFU/ml of ZIKV.

Mosquitoes were allowed to feed on ZIKV-infected mice and were examined at days 4, 7, and 10 post feeding to determine infection, dissemination, and transmission efficiencies. Infection efficiency corresponds to the proportion of mosquitoes with virus-infected bodies among the tested ones. Dissemination efficiency corresponds to the proportion of mosquitoes with virus-infected legs, and transmission efficiency corresponds to the proportion of mosquitoes with infectious saliva among those infected. *significant reduction in infection rates (*p < 0.05, **p < 0.01, ***p < 0.001) (A). Four days post feeding (n = 20) (B). Seven days post feeding (n = 20) (C). Ten days post feeding (n = 30).

Figure 2. Vector competence of WT and (COL)wMel mosquitoes orally infected with 4.74 log₁₀ PFU/ml of ZIKV.

Mosquitoes were allowed to feed on ZIKV-infected mice and were examined at days 4, 7, 10, and 14 post feeding to determine infection, dissemination, and transmission efficiencies. Infection efficiency corresponds to the proportion of mosquitoes with virus-infected bodies among the tested ones. Dissemination efficiency corresponds to the proportion of mosquitoes with virus-infected legs, and transmission efficiency corresponds to the proportion of mosquitoes with infectious saliva among those infected. *significant reduction in infection rates (*p < 0.05, **p < 0.01, ***p < 0.001) (A). Four days post feeding (n = 20) (B). Seven days post feeding (n = 20) (C). Ten days post feeding (n = 20) (D). Fourteen days post feeding (n = 20).

Figure 3. Vector competence of WT and (COL)wMel mosquitoes orally infected with 8.00 log₁₀ PFU/ml of ZIKV.

Mosquitoes were exposed to a ZIKV-infected bloodmeal via water-jacketed membrane feeder and were examined at days 10 and 17 post feeding to determine infection, dissemination, and transmission efficiencies. Infection efficiency corresponds to the proportion of mosquitoes with virus-infected bodies among the tested ones. Dissemination efficiency corresponds to the proportion of mosquitoes with virus-infected legs, and transmission efficiency corresponds to the proportion of mosquitoes with infectious saliva among those infected. *significant reduction in infection rates (*p < 0.05, **p < 0.01, ***p < 0.001) (A). Ten days post feeding (n = 18 for (COL)wMel and n = 19 for WT) (B). Seventeen days post feeding (n = 15 for (COL)wMel and n = 20 for WT).