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Porcine Reproductive and Respiratory Syndrome (view source)
Revision as of 19:24, 27 August 2010
, 19:24, 27 August 2010→Laboratory Tests
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 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.
The following specimens should be collected.
– For virus isolation and RT-PCR — whole blood (EDTA) and also serum, lung, respiratory tract, spleen
and tonsils of affected animals. Samples from mummified or aborted litters are unlikely to yield virus, but can
still be useful for RT-PCR.
– For antibody testing (serology) — serum from up to 20 exposed animals in the herd.
Specimens should be chilled and forwarded unfrozen on water ice or with frozen gel packs.
Virus isolation
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
passages for maximum sensitivity.
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.
Serological tests
IgM can be detected within 7 days of infection and IgG can be detected within 14 days. Humoral
antibody titres reach a maximum about 5–6 weeks after infection. Antibody can be detected by ELISA
and by the indirect staining of pre-prepared monolayers of infected cells (IPMA and IFA). Antibody
levels can drop quite quickly in the absence of circulating virus.
==Pathology==
==Pathology==