Researchers at The Pirbright Institute in the U.K., in collaboration with partners at the U.S. Department of Agriculture-Animal & Plant Health Inspection Service's Foreign Animal Disease Diagnostic Laboratory on Plum Island, N.Y., have shown that foot and mouth disease (FMD) virus can be detected in milk samples using a method that is potentially sensitive enough to identify the virus in pooled milk stored in bulk tanks or milk tankers.
According to the announcement, these results indicate that testing milk samples could contribute to disease surveillance both during and after outbreaks.
Pirbright researchers recently confirmed the efficacy of testing environmental samples for FMD.
FMD has a large economic impact, costing an estimated $11 billion globally each year in direct losses and vaccination costs. Outbreaks in countries that are usually free from FMD can have devastating consequences, such as the 2001 outbreak in the U.K., which resulted in the slaughter of 6 million animals and losses of more than £8 billion.
FMD control is heavily reliant on the rapid and accurate detection of the virus, Pirbright said. Current tests normally use tissue or blood samples, the collection of which can be invasive and require the expertise of a veterinarian or an animal health professional.
On the other hand, Pirbright noted that collection of milk is far less invasive and can be carried out daily, if needed. This method, described in Veterinary Microbiology, could be applied to disease surveillance in dairy herds, as testing of bulk milk samples is potentially sensitive enough to detect an infected cow in a typically sized herd of 100-1,000 animals, the institute said.
The test is able to generate a result in about four hours and can detect the virus genetic material in milk up to 28 days after the animal becomes infected, which is far longer than the 10 days afforded by traditional surveillance samples such as serum, the researchers said. This makes the technique a very promising surveillance tool for use during potential outbreaks in FMD-free countries or for studying the distribution and spread of the virus in regions where it is constantly present.
Sampling from bulk storage tanks also removes the need to test each animal individually and also does not require a veterinarian to be called out for sampling, thereby reducing the cost of testing as well as preventing animals from becoming stressed, Pirbright said.
Bryony Armson, first author of the research at Pirbright, said, “Milk is already used as a surveillance tool for a number of diseases, such as bovine viral diarrhea and brucellosis, so it makes sense to investigate this approach for the detection of FMD virus. We were able to detect virus in milk from FMD-infected cows during a real outbreak, and virus could be detected for a longer period in milk than in serum. We have also shown this FMD detection method can detect the virus in dilutions equivalent to those that would be present in bulk milk storage, highlighting the potential for milk to be used as a surveillance sample.”