Mosquitoes Inoculate High Doses of West Nile Virus as They Probe and Feed on Live Hosts

PLoS Pathogens

Laura D Kramer¹  Corey J Bennett¹  Rebecca G Albright¹  Linda M Styer¹  Kim A Kent¹  Kristen A Bernard² 

[1] Arbovirus Laboratories, Wadsworth Center, New York State Department of Health, Slingerlands, New York, United States of America;Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America

关键词: Mosquitoes;    West Nile virus;    Blood;    Capillary tubes;    Toes;    Viremia;    Thorax;    Viral load;   

DOI  :  10.1371/journal.ppat.0030132

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

West Nile virus (WNV) is transmitted to vertebrate hosts by mosquitoes as they take a blood meal. The amount of WNV inoculated by mosquitoes as they feed on a live host is not known. Previous estimates of the amount of WNV inoculated by mosquitoes (101.2–104.3 PFU) were based on in vitro assays that do not allow mosquitoes to probe or feed naturally. Here, we developed an in vivo assay to determine the amount of WNV inoculated by mosquitoes as they probe and feed on peripheral tissues of a mouse or chick. Using our assay, we recovered approximately one-third of a known amount of virus inoculated into mouse tissues. Accounting for unrecovered virus, mean and median doses of WNV inoculated by four mosquito species were 104.3 PFU and 105.0 PFU for Culex tarsalis, 105.9 PFU and 106.1 PFU for Cx. pipiens, 104.7 PFU and 104.7 PFU for Aedes japonicus, and 103.6 PFU and 103.4 PFU for Ae. triseriatus. In a direct comparison, in vivo estimates of the viral dose inoculated by Cx. tarsalis were approximately 600 times greater than estimates obtained by an in vitro capillary tube transmission assay. Virus did not disperse rapidly, as >99% of the virus was recovered from the section fed or probed upon by the mosquito. Furthermore, 76% (22/29) of mosquitoes inoculated a small amount of virus (∼102 PFU) directly into the blood while feeding. Direct introduction of virus into the blood may alter viral tropism, lead to earlier development of viremia, and cause low rates of infection in co-feeding mosquitoes. Our data demonstrate that mosquitoes inoculate high doses of WNV extravascularly and low doses intravascularly while probing and feeding on a live host. Accurate estimates of the viral dose inoculated by mosquitoes are critical in order to administer appropriate inoculation doses to animals in vaccine, host competence, and pathogenesis studies.

【 授权许可】

CC BY