Newborn calf blood tests could help improve Johne’s disease surveillance
Researchers at the Royal Veterinary College (RVC) have shown that antibodies against Johne's disease can be detected in newborn calves after they receive colostrum from their mothers, a finding that could provide a new way to investigate when animals are first exposed to the disease.
The study suggests that measuring these antibodies in calves shortly after birth could eventually complement existing surveillance programmes, helping researchers better understand how Johne's disease spreads and supporting improved disease control and animal welfare.
Johne's disease is a chronic and incurable infection caused by Mycobacterium avium subspecies paratuberculosis (MAP). Although cattle are thought to become infected during their first weeks or months of life, clinical signs often do not appear for several years. The disease damages the lining of the small intestine, leading to chronic inflammation, weight loss, diarrhoea, reduced milk production and, ultimately, death.
More than half of UK dairy herds are estimated to be affected, but current surveillance programmes primarily focus on identifying infection in adult animals, leaving uncertainty about when calves first encounter the pathogen.
To investigate early-life exposure, the RVC team analysed blood samples from 38 newborn dairy calves and their mothers on a commercial dairy farm in south-west England. The samples had originally been collected as part of routine monitoring to confirm that calves had successfully absorbed antibodies from colostrum.
Researchers measured MAP-specific antibodies in residual serum samples before using statistical modelling to examine how antibody levels related to both the mother's Johne's disease status and the efficiency of antibody transfer through colostrum.
The analysis showed that calves born to cows with MAP antibodies also had higher levels of MAP-specific antibodies. The relationship between antibody levels and the amount of antibody absorbed from colostrum also varied according to whether the mother tested positive or negative for MAP antibodies, findings consistent with antibody transfer from cow to calf through colostrum.
While the researchers stress that these measurements do not diagnose infection in newborn calves, they believe the approach could eventually support herd surveillance and risk assessment by providing new insights into exposure during the earliest stages of life.
Jonathan Hedgecock, lead author of the study and an RVC veterinary student graduate, said the approach could be straightforward to introduce because many calves already undergo blood sampling shortly after birth.
"We wouldn't need to take additional blood samples nor would we have to wait until they develop disease as adults," he said.
Dr Steven Van Winden, Associate Professor of Population Medicine at the RVC and supervisor of the research, added: "Johne's disease is unusual because infection typically occurs very early in life, yet we often cannot detect its consequences until years later. Our study shows that antibodies against the disease can be transferred from cow to calf and measured in newborn calves.
"While much more work is needed, this opens up an intriguing possibility for studying exposure risk during one of the most important periods in a calf's life."
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