Gamma irradiated female Aedes aegypti mosquitoes exhibit greater susceptibility to Mayaro virus

Authors: TREFRY, STEPHANIE - Us Army Medical Research Institute Of Infectious Diseases; Aldridge, Robert; SPRAGUE, THOMAS - Us Army Medical Research Institute Of Infectious Diseases; STUART, JOSEPH - Us Army Medical Research Institute Of Infectious Diseases; LOWEN, ROBERT - Us Army Medical Research Institute Of Infectious Diseases; ERASMUS, JESSE - University Of Washington; PITT, MARGARET - Us Army Medical Research Institute Of Infectious Diseases; HAHN, DANIEL - University Of Florida; NASAR, FAROOQ - University Of Texas Medical Branch; Gibson, Seth; Linthicum, Kenneth - Ken

Submitted to: Journal of American Society for Tropical Medicine and Hygiene
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Aedes aegypti mosquitoes transmit multiple different pathogens to humans causing disease and death worldwide. Mayaro virus is emerging as an Aedes aegypti borne virus that threatens human health and no vaccines yet exist. One way to protect humans from Mayaro and other pathogens is to reduce contact between humans and this mosquito. In the past, pesticides have been widely used to reduce populations of mosquitoes. However, mosquitoes are becoming resistant to pesticides and the availability of pesticide varieties that could overcome resistance is dwindling. One solution is to leverage new technology to reduce mosquito populations such as the sterile insect technique in which male mosquitoes are reared in large numbers, sterilized with controlled doses of radiation, and then released in the wild. The objective of this technique is to overwhelm female mosquito mate choice, reducing matings with wild males that are fertile, and therefore force most females to produce sterile eggs. Although this technique shows great promise, sometimes irradiated females are released alongside males and could possibly contribute to the numbers of mosquitoes seeking and biting humans. Also, it is unknown whether the presence of a pathogen such as Mayaro virus in mosquitoes reared for irradiation could interfere with the sterilization process and reduce the efficacy of the approach. In our investigation we found that although higher doses of radiation made female Aedes aegypti mosquitoes more susceptible to infection by Mayaro virus, their behavior and longevity were also altered such that transmission of this virus would be less likely than in non-irradiated wild female mosquitoes. This means that colony-reared females accidentally released with males in a sterile insect program would be unlikely to contribute to risk of transmission of this virus to humans.

Technical Abstract: Mayaro virus (MAYV) is an alphavirus endemic in many parts of Central and South America transmitted to humans by Aedes aegypti. Currently there is no vaccine nor treatment for Mayaro infection, and therefore it is essential to control transmission by reducing populations of vector mosquitoes such as Ae. aegypti. In light of diminishing vector control options due to dwindling registered insecticides and an increase in insecticide resistance, new options must be explored. One option is the sterile insect technique by radiation. In this investigation we exposed female Ae. aegypti pupae to radiation and evaluated vector competence following inoculation with MAYV. Infection and dissemination rates of irradiated (10 gy and 40 gy) Ae. aegypti were higher than that of the mock (i.e., non-irradiated) cohorts at 7 days post infection (dpi) and 14 dpi. Although these results indicate a need to maintain effective sorting prior to irradiation and release of Ae. aegypti to ensure only males are released, our results confirm previous observations that vectorial capacity and vector competence is likely lower in irradiated than non-irradiated females.