Bovine Papillomavirus Type 2 the key cause of sarcoids in New Zealand horses – study

An equine sarcoid.
An equine sarcoid. Image: Malcolm_Morley, CC BY-SA 3.0, via Wikimedia Commons

Most sarcoids in New Zealand horses are caused by Bovine Papillomavirus Type 2, the evidence suggests.

Equine sarcoids are common skin cancers of horses caused by bovine papillomaviruses (BPVs). Previous studies have suggested that most sarcoids are caused by either BPV1 or BPV2, with the proportion caused by each type dependent on the country in which the horse lived.

Some studies also suggest that other papillomavirus types could cause equine sarcoids.

John Munday and his fellow researchers, in a just-published study, conducted molecular-based testing on sarcoids from 104 New Zealand horses to determine the prevalence of the different bovine papillomavirus types. The horses were from three defined regions within the country, with the samples from two time periods separated by 15 years.

The study team tested for four bovine papillomavirus types, as well as one papillomavirus type that affects sheep.

Papillomavirus virus DNA was detected in 94 of the sarcoids, representing 90.4% of the samples tested.

Of the sarcoids containing papillomavirus DNA, 88.3% — 83 of the samples — contained only BPV2 DNA. Nine of the samples (9.6%) contained both BPV1 and BPV2 DNA, while two samples (2.1%) contained only BPV1 DNA. No other papillomavirus types were detected.

Photomicrograph of an equine sarcoid.
Photomicrograph of an equine sarcoid. Image: Munday, Orbell et al

“The predominance of BPV2 is consistent with studies of sarcoids from North America, but dissimilar to studies of sarcoids from Europe and Australia,” the study team reported in the open-access journal Animals.

“Detection rates of BPV1 and BPV2 were similar in sarcoids from different regions of New Zealand and in sarcoids from different time periods,” the authors said.

“These results suggest that most equine sarcoids in New Zealand are caused by BPV2,” they concluded. Thus, if vaccines are developed to prevent sarcoids, one that provides good protection against BPV2 will be required in this country, they said. Ideally,  a combined BPV1 and BPV2 virus-like particle vaccine would appear to be required for optimal protection for New Zealand horses.

The New Zealand results were most similar to a study of sarcoids from Canadian horses, in which 81% of 74 sarcoids contained only BPV2 DNA while 19% contained only BPV1 DNA. Similarly, 55% of 54 sarcoids from horses in the western United States contained only BPV2 DNA.

In contrast, studies of European horses revealed that most sarcoids are caused by BPV1, with only BPV1 detected in 88% of 99 sarcoids from Dutch horses, 95% of 58 sarcoids from Swiss horses, 100% of 10 sarcoids from British horses, and 95% of 21 sarcoids from horses in Poland.

In a similar manner, 70% of 10 sarcoids from Japanese horses contained only BPV1 DNA.

Interestingly, in a study of sarcoids from horses from Australia — the country geographically closest to New Zealand — 82% of 34 sarcoids contained only BPV1 DNA, while 18% contained only BPV2 DNA.

The cause in New Zealand is more similar to that of sarcoids in North America than in Europe or Australia, they said.

The study team comprised Munday, with the School of Veterinary Science at Massey University in Palmerston North; and Geoff Orbell, Rob Fairley, Michael Hardcastle and Bernie Vaatstra, with Gribbles Veterinary Ltd.

The research was funded by the New Zealand Equine Trust.

Munday, J.S.; Orbell, G.; Fairley, R.A.; Hardcastle, M.; Vaatstra, B. Evidence from a Series of 104 Equine Sarcoids Suggests That Most Sarcoids in New Zealand Are Caused by Bovine Papillomavirus Type 2, although Both BPV1 and BPV2 DNA Are Detectable in around 10% of Sarcoids. Animals 2021, 11, 3093.

The study, published under a Creative Commons License, can be read here

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