Subclinical infection of vaccinated pigs has been reported,

but other vaccinated pen-mates showed disease [33]. Studies on experimentally infected pigs showed that there is a rather short duration of NSP seroreactivity in infected pigs with declining levels of reactors after 9 weeks [40]. If the serosurvey aimed at demonstrating freedom from FMD finds evidence of NSP reactors within herds, then following retesting and use of confirmatory tests, the number and strength of the seroreactors will influence the degree of suspicion that infection occurred [49]. It can be argued that if farm visits for the initial collection of serum samples have already included careful inspection of all the animals without Selleck Alectinib finding any signs of disease and if isolated NSP positive reactors are subsequently found at a level consistent with that expected (from the known specificity of the test used) there should not need to be any follow-up visits for inspection and resampling/testing as

prescribed in the OIE Code and the EU Directive [9] and [19]. Other factors that would mitigate against the need for a follow-up farm visit include the availability of location data for individual animals to rule out clustering of positive cases, samples originating from pigs that do not become long-term virus carriers Tyrosine Kinase Inhibitor Library chemical structure and only weak positive test reactor findings. Such decisions need to be taken on a case-by-case basis. If the level of suspicion warrants a follow-up visit, this should check for clinical signs and clustering of positive animals and to examine and resample the initially seropositive Metalloexopeptidase animals along with in-contact animals. If clinical or epidemiological evidence for infection or disease were then found, the usual measures for investigating a suspect case would be followed. Past infection would be distinguished from non-specific reactors by presence or absence

of clustering and by the number and strength of seroreactors relative to that predicted from the known specificity of the test [55]. Recent infection would be confirmed by clinical checks and/or evidence of seroconversion from the second round of sampling [19] and [56]. IgM tests could also be helpful in this situation [57]. Oral or nasal swabs could be collected from pigs and oesophagopharyngeal fluids collected from ruminants for virological testing to look for evidence of infection [58]. However, the virological techniques have low sensitivity whilst a false positive test finding could be difficult to identify. Use of an IgA test has been proposed as a proxy for the probang virus test [59] and [60] as FMDV-specific IgA antibody in mucosal secretions of the upper respiratory tract of cattle is mainly associated with the continued presence of detectable virus in a probang cup sample. However, despite the potential logistic advantages, the IgA test is not yet commercially available.