May 27, 2016
A retro-viral wolf in sheep’s clothing
By Kyra Lightburn
An effective, non-invasive and inexpensive method for diagnosing the nasal tumour-causing virus in sheep and goats has been developed at the University of Guelph.
The virus, known as enzootic nasal tumor virus (ENTV -1), has been the target of Prof. Sarah Wootton and her University of Guelph colleagues.
They studied a flock of 80 horned Dorset sheep with a history of Enzootic nasal adenocarcinoma in Ontario throughout 2014. Wootton developed a diagnostic technique, known as reverse transcriptase PCR (RT-PCR), to detect pre-symptom ENTV with what she calls “perfect sensitivity and specificity.”
The technique involves taking double nasal swabs from live animals, followed by further lab analysis to identify viral RNA associated with the disease. It’s easily performed by producers or veterinarians and can be done before symptoms arise enabling early diagnosis and, when necessary, quarantine to prevent further viral spread within a flock.
Animals showing symptoms of the contagious tumors, including excessive mucus production, respiratory difficulties and in some cases death, are often misdiagnosed or go un-diagnosed. Wootton estimates that prevalence rates are 10 per cent in North America and parts of Europe, making ENTV an economically important virus to combat.
Traditionally, diagnosis was complicated by the fact that copies of ENTV retrovirus have been integrated into the sheep genome over millions of years. As a result, sheep form inconsistent immune responses to the presence of the virus, making blood cell analysis for antibodies ineffective.
Going forward, Wootton sees many opportunities for related research — some that look at other sheep viruses in an effort to create vaccines, and some addressing the mechanisms by which retroviruses transform cells causing tumors.
In particularly, she is interested in Jaagsiekte Sheep Retrovirus (JSRV), a seemingly mutually exclusive disease, but genetically very similar to ENTV. It predominantly affects sheep and goats in Europe, South Africa and Asia causing fatal lung tumors.
The lung tumors caused by JSRV are very similar to non-smoking related tumors in humans that disproportionately affect women, says Wootton. “We are interested in looking at what host proteins are interacting with the virus to create this cancer. The goal being that such research can eventually relate back to human therapy studies.”
Moreover, Wootton notes she is interested in further investigating the similarities between ENTV and JSRV. Both these viruses use the same receptors to bind to cells, she says. “The immediate question that arises is then “why do they cause such different disease symptoms?”
Wootton is now looking to partner with Ontario abattoirs to study discarded sheep heads, to better pin down exact ENTV prevalence rates in the province.
Collaborators on Wootton’s ENTV research projects include Scott Walsh, Kevin Stinson and Prof. Paula Menzies.
Funding for the project was provided by The Gartshore Memorial Sheep Research Fund.
Article Source: Office of Research