Impacts of infectious dose, feeding behavior, and age of Culicoides sonorensis biting midges on infection dynamics of vesicular stomatitis virus

Authors: ROZO-LOPEZ, PAULA - Kansas State University; LONDONO, BERLIN - Kansas State University; Drolet, Barbara

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2021
Publication Date: 6/29/2021
Citation: Rozo-Lopez, P., Londono, B., Drolet, B.S. 2021. Impacts of infectious dose, feeding behavior, and age of Culicoides sonorensis biting midges on infection dynamics of vesicular stomatitis virus. Pathogens. 10(7):816. https://doi.org/10.3390/pathogens10070816.
DOI: https://doi.org/10.3390/pathogens10070816

Interpretive Summary: Culicoides sonorensis biting midges are agriculturally important pests of US livestock and wildlife. They are also able to transmit vesicular stomatitis virus which causes disease in cattle, horses and swine. Yet, little is known about how much virus is required to infect midges, nor how their feeding behavior or age affects viral replication and their ability to transmit it to another animal. We determined that midges were able to become infected after ingesting a dose of virus at least 10,000 times lower than what is typically found in vesicular lesions on the animal's skin where they blood-feed. Once midges are infected, and blood-feed again in order to lay another batch of eggs, virus replication is greatly enhanced. We also found that the older the midge is at the time of infection, the faster virus replicates. This research highlights how midge feeding behavior and physiology affect how much virus midges produce which ultimately predicts how well they will transmit the virus between animals. This information is important for epidemiologists to more precisely estimate the risk of vesicular stomatitis virus transmission by Culicoides midges, and to inform pest management practices for reducing disease risk by controlling midge populations.

Technical Abstract: Culicoides sonorensis biting midges are important biological vectors of vesicular stomatitis virus (VSV) in the U.S. Yet, little is known about how much virus is required to infect midges, nor how their feeding behavior or age affects viral replication and vector competence. The minimum infectious dose, effect of multiple blood-feeding cycles, and the effect of midge age at the time of virus acquisition on VSV infection dynamics were investigated. Infectious dose studies showed a minimum dose of 3.2 logs of virus/mL of blood resulted in midgut infections, and 5.2 logs/ml resulted in a disseminated infection to salivary glands. For blood-feeding behavior studies, ingestion of one or two non-infectious blood meals (BM) after a VSV infectious meal (VSV-BM) resulted in higher whole-body virus titers than midges receiving only the single infectious VSV-BM. Interestingly, this infection enhancement was not seen when a non-infectious BM preceded the infectious VSV-BM. Lastly, increased midge age at the time of infection correlated to increased whole-body virus titers. This research highlights the epidemiological implications of infectious doses, vector feeding behaviors, and vector age on VSV infection dynamics to more precisely estimate the risk of transmission by Culicoides midges.