Transmission of equine infectious anemia virus by Tabanus fuscicostatus.

The research explored the mechanical transmission of a virus called equine infectious anemia (EIA) by a type of horsefly known as Tabanus fuscicostatus. The study concluded that these horseflies can transmit the virus and that typical control measures may not be sufficient to prevent transmission, particularly in areas with numerous horseflies.

Investigation of virus transmission

• The research focused on the mechanical transmission of equine infectious anemia (EIA), a viral disease that affects horses, by a horsefly species known as Tabanus fuscicostatus.
• The researchers set up 7 transmission trials where a single horsefly transmitted the EIA virus from an acutely infected pony to a susceptible one. From these trials, transmission of the virus occurred in one instance.

Timing and virus transmission

• The study also investigated the effect of isolation time on the horsefly’s ability to transmit the virus. They compared transmission rates of horseflies isolated for 3, 10, or 30 minutes before refeeding to those isolated for 4 or 24 hours. The data showed that horseflies could transmit the virus if they were isolated for short periods (3, 10, or 30 minutes) but could not do so if isolated for 4 or 24 hours.

Implications for virus control measures

• From field studies, it was observed that horseflies can travel more than 4 miles. Keeping this data in perspective with their research observations, the researchers indicated that currently accepted control measures for EIA, such as segregation of infected horses by at least 200 yards from susceptible ones, may not suffice to prevent transmission, especially in areas where horseflies are abundant.
• The distance horseflies can travel and their ability to transmit the virus within certain time frames, suggest that control measures may need to be reevaluated and potentially revised to effectively impede the transmission of EIA.