The possible role of Stomoxys calcitrans in equine sarcoid transmission.

This research explores the possibility of stable flies (Stomoxys calcitrans) serving as a vector in transmitting the bovine papillomavirus (BPV), believed to cause equine sarcoids, between horses. The study found that both sarcoid and papilloma-exposed flies showed a significant increase in BPV load after exposure to the respective tissues, indicating possible BPV transmission, with the probability higher after contact with bovine papilloma than equine sarcoid.

Research Objective and Methodology

• The research aimed to understand whether stable flies that initially did not have BPV could contract the virus after exposure to equine sarcoid or bovine papilloma tissue, and how long it retained the virus.
• A total of 420 stable flies were caught live and exposed to BPV-positive equine sarcoid or bovine papilloma tissue.
• Over the following week, researchers collected those flies that had died every day and determined the BPV loads in them by performing quantitative PCR.

Key Research Findings

• The results showed a significant increase in BPV load in the flies after they were exposed to either sarcoid or papilloma tissue.
• It was observed that the viral load was higher and lasted longer in those flies exposed to papilloma tissue compared to those exposed to sarcoid tissue.
• However, the viral loads decreased again within a few days and became indistinguishable from the loads observed before exposure.
• The study deduced from these observations that BPV transmission by stable flies seems possible, and is more likely to occur after contact with bovine papillomas than with equine sarcoids.
• Moreover, the data indicates that such transmission may only be possible shortly after tissue exposure.

Recommendations for Further Research

• Additional investigations could involve attempting to induce sarcoids experimentally using BPV-positive stable flies.
• Another qualitative leap in this research could be to repeat the experiment by micro-dissecting the flies prior to conducting PCR on them. This could reveal more about how the virus persists within the flies, providing a more comprehensive understanding of how this insect species might serve as a potential vector for BPV transmission.