Evaluation of mosquito transmission of equine hepacivirus in laboratory and field studies

Equine hepacivirus (EqHV) is a hepatotropic virus, closely related to human hepatitis C virus (HCV), that can cause acute or chronic infection in horses. As with HCV, transmission is thought to occur primarily through parenteral, particularly blood-borne, routes. Vertical transmission from mare to foal has been reported but appears to be uncommon. The high seroprevalence in horse populations and the occurrence of infection in isolated horses indicate efficient horizontal transmission routes exist. One such possibility is biological or mechanical transmission by arthropods, such as mosquitoes, stable flies, or ticks. Here, we conducted 2 complementary studies to evaluate the possible role of mosquitoes as EqHV biological vectors. In the laboratory, we orally exposed Aedes albopictus (Skuse) females to EqHV through artificial bloodfeeding with blood collected from 2 chronically infected horses. Mosquito samples (body, legs, and saliva) were collected at multiple time points post-exposure and tested for EqHV RNA by molecular assays. In the field, 2,138 mosquitoes were collected from New York and Florida, United States, and screened for EqHV RNA. No EqHV RNA was detected in any samples from the laboratory experiment or among field-collected mosquitoes. These findings indicate that the Ae. albopictus strain evaluated here is unlikely to serve as a biological vector of EqHV and corroborate previous negative findings in field-collected mosquitoes. Nevertheless, low infection rates may have gone undetected. Laboratory studies of additional horse-feeding mosquito species and expanded field collections in EqHV-endemic regions are needed to further clarify any potential role for mosquitoes in EqHV transmission.