Researchers at The Pirbright Institute in collaboration with partners at the USDA Animal and Plant Health Inspection Service (APHIS) Foreign Animal Disease Diagnostic Laboratory on Plum Island USA, have shown that foot-and-mouth disease virus (FMDV) 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. These encouraging results indicate that testing of milk samples could contribute to disease surveillance both during and after outbreaks.
Foot-and-mouth disease (FMD) has a huge economic impact, costing an estimated US $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 UK 2001 outbreak which resulted in the slaughter of six million animals and losses of over £8 billion.
The control of the disease is heavily reliant on the rapid and accurate detection of the virus. 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. Collection of milk is far less invasive and can be carried out daily if needed. This method, described in Veterinary Microbiology,(Science Direct: Detection of foot-and-mouth disease virus in milk samples by real-time reverse transcription polymerase chain reaction: optimisation and evaluation of a high-throughput screening method with potential for disease surveillance.) 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 typical sized herd of 100-1000 individuals.
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 ten days afforded by traditional surveillance samples such as serum. 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.
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 diarrhoea and brucellosis, so it makes sense to investigate this approach for the detection of FMDV. 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.”