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Porcine Reproductive and Respiratory Syndrome (view source)
Revision as of 19:22, 27 August 2010
, 19:22, 27 August 2010→Pathology
==Pathology==
==Pathology==
PRRS virus produces a multisystemic infection in pigs, but gross lesions are usually only observed in
respiratory and lymphoid tissues. Both gross and microscopic lesions are most marked in neonatal and young
weaned pigs. The gross pathology observed after uncomplicated infection of PRRS virus in finishing pigs may
be anything from severe to unremarkable.
In severe disease, lungs are mottled, tan and red, and fail to collapse; the cranioventral lobes are most affected.
Lymph nodes are moderately to severely enlarged and tan in colour and, for some strains of virus, may be
haemorrhagic. Under field conditions, most PRRS virus infected pigs are co-infected with one or more
pathogens, which complicates the diagnosis of PRRS based on pathology.
Gross necropsy lesions are minimal in the uncomplicated respiratory form of PRRS. Microscopically, interstitial pneumonia is the typical finding. There is a mononuclear infiltration of the alveolar walls with type 2 pneumonocyte proliferation, and necrotic debris and macrophages accumulate in the alveolar spaces. In lymph nodes, follicular hyperplasia and necrosis may be seen. Non-suppurative meningoencephalitis and choroiditis is commonly present, but severity is highly variable.
Gross necropsy lesions are minimal in the uncomplicated respiratory form of PRRS. Microscopically, interstitial pneumonia is the typical finding. There is a mononuclear infiltration of the alveolar walls with type 2 pneumonocyte proliferation, and necrotic debris and macrophages accumulate in the alveolar spaces. In lymph nodes, follicular hyperplasia and necrosis may be seen. Non-suppurative meningoencephalitis and choroiditis is commonly present, but severity is highly variable.