Bovine papilloma virus (BPV) has been implicated as one etiology for the development of equine sarcoid. Researchers at Belgium’s Ghent University School of Veterinary Medicine looked at possible transmission of equine sarcoid via stable flies (Stomoxys calcitrans) by evaluating for BPV DNA [Haspeslagh, M.; Vlaminck, L.; Martens, A. The possible role of Stomoxys calcitrans in equine sarcoid transmission, The Veterinary Journal 231 (2018), pp. 8-12].
The proboscis of stable flies is able to pierce the skin, particularly in thin-skinned areas like the axilla, inguinal region and the head. In this experiment, 96% of flies caught were stable flies. The study exposed 420 stable flies to both BPV-positive bovine papilloma tissue and equine sarcoid tissue.
Their findings using quantitative PCR stated: “There was a significant rise in BPV load after tissue exposure both in sarcoid and papilloma-exposed flies, but the viral load was 10-fold higher and remained high for a longer time after exposure to papilloma tissue compared to sarcoid tissue.”
The researchers concluded that transmission occurs shortly after exposure to infected tissue, with viral levels declining quickly, typically within a couple of hours. The rapid decline of measurable BPV DNA indicates that the opportunity for transmission is limited in time, which therefore limits the distance an infected fly can travel to a new host. The authors further suggest that viral spread is more likely from cattle to horses than between horses. That means sufficient separation of horses away from cattle might serve to minimize sarcoid transmission by fly vectors.