Bovine papillomavirus DNA in neoplastic and nonneoplastic tissues obtainedfrom horses with and without sarcoids in the western United States

Objective-To determine the incidence of bovine papillomavirus (BPV) type 1 or 2 in sarcoids and other samples of cutaneous tissues collected from hors es in the western United States. Animals-55 horses with sarcoids and 12 horses without sarcoids. Procedure-Tissue samples (tumor and normal skin from horses with sarcoids a nd normal skin, papillomas, and nonsarcoid cutaneous neoplasms from horses without sarcoids) were collected. Tissue samples were analyzed for BPV-1 or -2 DNA, using a polymerase chain reaction (PCR) and restriction fragment l ength polymorphism. The PCR products from 7 sar cold-affected horses were s equenced to evaluate percentage homology with expected sequences for BPV-1 or-2. Results-Most (94/96, 98%) sarcoids contained BPV DNA. Sixty-two percent of the tumors examined had restriction enzyme patterns consistent with BPV-2. Thirty-one of 49 (63%) samples of normal skin obtained from horses with sar coids contained BPV DNA. All samples subsequently sequenced had 100% homolo gy with the expected sequences for the specific viral type. All tissues fro m healthy horses, nonsarcoid neoplasms, and papillomas were negative for BP V DNA. Conclusions and Clinical Relevance-Bovine papillomaviral DNA was detected i n essentially all sarcoids examined. There appears to be regional variation in the prevalence of viral types in these tumors. The fact that we detecte d viral DNA in normal skin samples from horses with sarcoids suggests the p ossibility of a latent viral phase. Viral latency may be 1 explanation for the high rate of recurrence following surgical excision of sarcoids.