When animals are showing symptoms of FMD, a rapid test for the virus particles is undertaken to confirm the presence of FMD virus [Test 1]. Two additional tests are used to seek confirmation of the presence of the virus [Tests 2 and 3] and establish the serotype. Further forensic characterisation (“sequencing”) helps to determine which farm the virus may have spread from. Symptoms of FMD virus can be difficult to observe in some cases, especially in sheep and goats. It is essential that these animals are identified; otherwise they could perpetuate the disease by spreading virus. In order to rapidly survey many animals in the Control Zone and Surveillance Zone, blood tests are done. The target is the antibodies that would most likely be present if an animal was, or had previously been, infected with FMD virus.
We are performing two rapid antibody detection tests during the UK outbreak. One (Ceditest® FMDV Type O) detects antibodies specific to serotype O FMD virus, which is the type of virus in the UK 2007 outbreak. The other test (Ceditest® FMDV-NS) detects antibodies against all of the seven serotypes of FMD virus. Final confirmation of any positive findings is by the gold standard “virus neutralisation test” which takes two days before giving results.
The picture shows results obtained with the Ceditest® FMDV-NS kit (left) and Ceditest® FMDV Type O (right). In these tests, the yellow colour indicates the absence of FMD virus antibodies i.e. it is the colourless samples that are indicative of an animal that has antibodies to FMD virus.
During the 2007 UK outbreak of FMD virus, sheep from the fifth infected farm (Infected Premises 5 or IP5) were first shown to be positive for FMD using these tests. Symptoms of FMD had not been observed in these animals, but blood samples were taken from them as they were in the 3 kilometre Protection Zone around IP4. The blood tests gave a positive result. Subsequently a vet from IAH went to IP5 to get samples from the oesophagus of the animals where the virus can persist after recovery from the disease. These samples were used in the very sensitive test that detects the genetic material of the virus even before symptoms have developed (Test 3 in LINK to piece already on web). This test also gave a positive result. Identifying this farm has been a key step in linking the August and September phases of the epidemic.