Wolbachia Infection Reduces Blood-Feeding Success in the Dengue Fever Mosquito, Aedes aegypti

Abstract

The mosquito Aedes aegypti was recently transinfected with a life-shortening strain of the endosymbiont Wolbachia pipientis (wMelPop) as the first step in developing a biocontrol strategy for dengue virus transmission. In addition to life-shortening, the wMelPop-infected mosquitoes also exhibit increased daytime activity and metabolic rates. Here we sought to quantify the blood-feeding behaviour of Wolbachia-infected females as an indicator of any virulence or energetic drain associated with Wolbachia infection. In a series of blood-feeding trials in response to humans, we have shown that Wolbachia-infected mosquitoes do not differ in their response time to humans, but that as they age they obtain fewer and smaller blood meals than Wolbachia-uninfected controls. Lastly, we observed a behavioural characteristic in the Wolbachia infected mosquitoes best described as a “bendy” proboscis that may explain the decreased biting success. Taken together the evidence suggests that wMelPop infection may be causing tissue damage in a manner that intensifies with mosquito age and that leads to reduced blood-feeding success. These behavioural changes require further investigation with respect to a possible physiological mechanism and their role in vectorial capacity of the insect. The selective decrease of feeding success in older mosquitoes may act synergistically with other Wolbachia-associated traits including life-shortening and viral protection in biocontrol strategies. The primary mosquito vector of dengue virus, Aedes aegypti, has recently been artificially infected with a symbiotic bacterium called Wolbachia pipientis. This bacterium occurs naturally inside the cells of ∼66% of insect species. The Wolbachia used to infect A. aegypti shortens the insect's lifespan. Because only old mosquitoes are capable of transmitting dengue virus, the Wolbachia infection could theoretically reduce dengue virus transmission if infected mosquitoes were released into the wild. Here we have examined the effects of this Wolbachia infection on the mosquito's ability to obtain blood meals from human hosts. Blood is required for females to produce eggs, and so successful completion of this behaviour is necessary if Wolbachia-infected mosquitoes are to be competitive in the wild. Blood feeding on humans is also the time when viruses like dengue are transmitted, so changes in this behaviour can have consequences for the transmission rate of viruses. We show that Wolbachia-infected mosquitoes are less able to obtain blood meals, but only in old age. The reduced feeding success may be explained by a defect in the insect's proboscis. The finding is exciting as it may allow young mosquitoes to breed as normal but help reduce the lifespan and success of old mosquitoes, which are the primary transmitters of virus.