Changes

The most frequently used diagnostic tests are an ELISA and an indirect fluorescent antibody test. In order for meaningful results to be generated, serum should be collected from around 20 exposed animals in the herds.  Both of the ELISA and the IFAT tests measure antibodies against PRRS virus. Anti-PRRS specific IgM can be detected within 7 days of infection, and IgG can be detected within 14 days. Titres peak about 5–6 weeks after infection, and can persist for up to 144 days while circulating virus is present. Once virus ceases to circulate, antibody levels quickly drop. If titres are particularly high, exposure may be recent exposure and the sampled population could currently be shedding virus.

The most frequently used diagnostic tests are an ELISA and an indirect fluorescent antibody test. In order for meaningful results to be generated, serum should be collected from around 20 exposed animals in the herds.  Both of the ELISA and the IFAT tests measure antibodies against PRRS virus. Anti-PRRS specific IgM can be detected within 7 days of infection, and IgG can be detected within 14 days. Titres peak about 5–6 weeks after infection, and can persist for up to 144 days while circulating virus is present. Once virus ceases to circulate, antibody levels quickly drop. If titres are particularly high, exposure may be recent exposure and the sampled population could currently be shedding virus.

Tests for the PRRS virus itself also exist. These include PCR and virus isolation on clinical samples, and immunohistochemistry on tissues. Nucleic acid sequencing of the 5' end of the virus is commercially availabe ans is useful for comparing isolates recovered from different sites in order to facilitate epidemiological investigations.

Tests for the PRRS virus itself also exist. These include RT-PCR and virus isolation. For virus isolation, buffy coat, serum, lung, lymph nodes, spleen and tonsils are the specimens of choice. The virus is incubated with swine pulmonary alveolar macrophages, and cytopathic effect are seen in around four days. RT-PCR can be performed on whole blood, buffy coat and clarified homogenates of the tissues appropriate for virus isolation. The test is particularly useful for examination of mummified or aborted litters. Immunohistochemistry is also possible, and nucleic acid sequencing of the 5' end of the virus has recently become commercially available. This is  useful for comparing isolates recovered from different sites in order to facilitate epidemiological investigations.

 

– For virus isolation and RT-PCR — whole blood (EDTA) and also serum, lung, respiratory tract, spleen

Buffy coat, serum, lung, lymph nodes, spleen and tonsils are the specimens of choice. The virus

replicates well on swine pulmonary alveolar macrophages and some strains, particularly those of

genotype 2, on Marc 145 cells. Cytopathic effects are evident in 1–4 days. Perform two 7-day

􀂃 RT-PCR

Whole blood (EDTA), buffy coat and clarified homogenates of the above tissues are best. At this

time, there is no fully validated PCR that has international acceptability. Please consult the OIE

Manual for suggested methods.

==Pathology==

==Pathology==