Unexplained neurological illness in cattle and sheep – assessing the potential risks to human health

Following a recent announcement by the Department of the Environment Food and Rural Affairs (DEFRA) concerning cattle and sheep with an undiagnosed encephalitic illness, the Health Protection Agency were tasked with convening a group of experts to assess the potential risk to human health.

At the meeting, which was held on 21st June, experts reviewed information about the original case in a heifer, another unrelated case in a bull and 20 cases in sheep which had occurred over a 10 year period. They were also informed of a further 7 adult cattle submitted under BSE Orders between 2000 and 2003. Recent laboratory investigations from the original case in a heifer identified an enterovirus as the most likely cause of infection, which is unlikely to pose a threat to human health. Samples from the other cases will now also be tested for enteroviruses.

Dr Dilys Morgan who led the group on behalf of the Agency said; “It is reassuring that the cause of illness in the heifer has been identified. Enteroviruses are a common cause of illness in both animals and humans, however they do not usually cross between species. This combined with the fact that animals are examined prior to slaughter by a veterinary surgeon and any with symptoms of acute viral disease are prevented from entering the food chain, and that enteroviruses are killed by heat, means that this case is thought unlikely to pose any risk to human health”

In considering the available data on all the cases, the group of experts agreed that due to a variety of reasons they also didn’t pose a significant risk to human health. These reasons included the fact that there was no increasing trend in the low number of samples being submitted for testing from cows and sheep with neurological illness over the last 10 years, and that no apparent link has been identified between these cases and the cases represented a variety of clinical and pathological findings.

Dr Morgan concluded, “As more evidence becomes available we will continue to assess the risk, but the information we have so far suggests that these cases are unlikely to pose a significant risk to human health”.