DNA OF BOVINE PAPILLOMAVIRUS TYPE-1 AND TYPE-2 IN EQUINE SARCOIDS - PCR DETECTION AND DIRECT SEQUENCING

Nucleotide sequences of bovine papillomavirus (BPV) DNA amplified by t he polymerase chain reaction (PCR) from samples of equine sarcoid skin tumours were determined. All naturally occurring sarcoids (n = 58 tum ours from 32 horses and 2 donkeys) contained BPV-DNA. All but 3 of the genome fragments belonged to the BPV type 1 strain (BPV-1); the remai ning were BPV type 2. Similar results were obtained with cutaneous bov ine papillomas used as controls (n = 20). One of the horses, carrying 2 sarcoids, was particularly interesting; one tumour contained BPV-1 D NA whilst the other sarcoid yielded BPV-2 DNA, suggesting that horses are not immune to super-infection. BPV-DNA was even amplified from the sarcoid samples which had yielded negative results in previous invest igations when DNA isolated from the lesions was used in Southern blot hybridization with BPV probes. In addition, there was no detectable BP V-DNA in any equine or bovine tissue examined other than sarcoids or c utaneous bovine papillomas. Biopsies of normal skin surrounding lesion s yielded exclusively negative results. The described nucleotide diffe rences represent a natural genomic variation of this BPV type between geographically distant locations. The identical variations recovered f rom cattle and horses in Switzerland, a finding of great epidemiologic al interest, strongly suggest that a uniform variant of BPV-1 is one o f the etiologic agents of equine sarcoid and bovine papilloma in a giv en region.