Calves show early indicator of Johne’s disease exposure
Researchers discovered differences in antibody levels through blood tests.
Researchers from the Royal Veterinary College (RVC) have discovered how blood samples could act as an early indicator of Johne’s disease in calves.
Samples revealed antibodies, thought to have transferred from the calves’ mother through colostrum, gave the calves protection from the bacteria which causes Johne’s disease. This could support researchers in discovering when calves are first exposed to the disease.
Johne’s disease is a chronic and incurable infectious disease, which progressively damages the lining of a cow’s small intestine. This will cause chronic inflammation, which can lead to severe weight loss, low milk yields, diarrhoea and death.
It is caused by Mycobacterium avium subspecies paratuberculosis (MAP). While calves are thought to become infected during the first few weeks or months of their lives, symptoms of the disease may not develop for several years.
To understand this exposure, researchers from the RVC analysed blood samples, taken as part of routine monitoring, from 38 newborn dairy calves and their dams on a commercial dairy farm in the south-west of England.
The team measured the levels of MAP-specific antibodies in the remaining (residual) serum samples. They used statistical modelling to examine how these antibody levels related to the dam’s Johne’s disease status, as well as exploring the efficiency of antibody transfer from colostrum.
Calves which had been born to cows with MAP antibodies had higher levels of MAP-specific antibodies than those born to cows without detectable antibodies.
Researchers also discovered differences between the relationship between antibody levels and the amount of antibody absorbed from the colostrum. This appeared to differ depending on whether the mother was MAP-seropositive or MAP-seronegative.
These findings have therefore been concluded as consistent with MAP-specific antibodies being passed from cows to their calves through colostrum.
It is hoped that these discoveries will support a better understanding of a Johne’s disease spreads and how vets can improve disease control and cattle welfare. Although antibody measurements can not be used as a diagnostic test, they may complement existing herd surveillance and risk assessment strategies.
Jonathan Hedgecock, lead author of the study and an RVC graduate, said: “Continued research into new testing strategies for Johne’s disease is important with more work still needed. Many calves are already blood sampled for serum total protein at a young age, so being able to test calves at this age would be straightforward as we wouldn’t need to take additional blood samples nor would we have to wait until they develop disease as adults.”
The full study can be found in the journal Animals.
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