Saturday, April 20, 2024

Facial eczema lab test sought

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A simple laboratory test could one day be available for farmers to test their livestock’s tolerance to facial eczema.
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AgResearch scientists have begun researching the feasibility of such a test in a pilot study being launched this month.

Results are expected by March in the study led by AgResearch’s Dr Axel Heiser and funded by Beef + Lamb.

The first phase investigates how cells from easily accessible samples such as blood, saliva and skin react to the toxin sporidesmin that causes eczema. The study involves taking samples from 20 animals from AgResearch’s farms that are a mix of both FE tolerant and FE susceptible and exposing them to the sporidesmin.

The cells’ reaction is measured for markers that change in response to sporidesmin and can show at a cellular level whether the animal is FE tolerant, Heiser said.

“We have really good analytical methods to look at everything these cells do so I’m quite confident that we’ll get a signature out of these cells.”

The marker tests will not be breed specific.

“In the past when we have looked for signatures of these markers for other diseases we have found that breed does not have such a huge influence.

“We do know there are breeds that are more and less susceptible and we will come back to that when we validate the tests.”

If the pilot is successful then work will start on creating a simpler, faster and more affordable way for the method to be done in a diagnostic laboratory.

The final phase is to validate the test on a larger group of animals.

FE has been known in New Zealand for more than 100 years and is caused by the sporidesmin, produced by the fungus Pithomyces chartarum. This spore-producing fungus sits in the litter at the base of pasture swards.

It causes damage to the bile system of the liver of sheep and cattle. A secondary effect of the liver damage is photosensitisation, which causes skin reddening and peeling, leaving affected areas susceptible to other infections. It is suspected that for every clinical case of FE there are 10 more with the disease.

The disease causes significant production losses and impacts on the welfare of affected animals. The Facial Eczema Working Group, comprising of farmers and researchers have estimated that in a bad year FE can cost the country $266 million in lost production.

And the changing climate means FE, which is more common in warm, moist environments, is likely to spread further into southern regions over time.

Heiser sees a test as a tool for ram and bull breeders and dairy genetics companies to indicate how FE tolerant their sires are.

“You would select your bulls or rams based on this new test. I think it can be a quick and affordable test so the farmer that usually gets the bull or the semen can also test the ewes or the dams and make a selection on the female side of the breeding as well, which would mean the success of the breeding programme would come much faster. You could select on both parents’ sides and that’s really my goal.”

Commercial farmers could then request the test results from their ram or bull breeder or from genetics company if it is semen when buying a new sire.

“If it works we should be able to give it a proper score.”

He sees it sitting alongside the spore count tests farmers regularly do in late summer if their farm is in a high spore count area.

It could also mean an end to the annual zinc treatments.

The pilot will take about six months followed by another six to nine months of validating the test with animals before a decision will be made to move to the next phase in two years.

The study is part of a larger research proposal Heiser and others are preparing to further investigate FE. It will include testing, treatments and the spores that cause FE and why it is a problem in NZ but not anywhere else.

“I think that if we want to solve the problem we need to solve it before the toxin gets into the cow or the sheep. I think, ideally, we solve it in the pasture.”

He hopes to obtain funding early next year.

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