Changes

==Pathology==

==Pathology==

PRRS virus produces a multisystemic infection in pigs, but gross lesions are usually only observed in

Although PRRS virus is capable of infection many organs of the pig, but gross lesions are usually only observed in the respiratory and lymphoid tissues. Both gross and microscopic lesions are most marked in neonatal and young weaned pigs.

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

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.

After an uncomplicated PRRS infection  in finishing pigs, gross lesions can vary from unremarkable to severe. In severe disease, lungs are mottled red and tan, and fail to collapse properly. The cranioventral lobes are worst affected. Lymph nodes appear moderately to severely enlarged, tan in colour and may be haemorrhagic with some strains of virus. Most PRRS virus-infected pigs are co-infected with one or more secondary pathogens, so pathology can vary quite widely depending on these. 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.

There are no gross lesions noted in aborted or stillborn fetuses, but histopathology inconsistently interstitial pneumonia, myocarditis anr pulmonary arteritis. However, these changes are not specific or diagnostic for PRRS.

There are no gross lesions noted in aborted or stillborn fetuses, but histopathology inconsistently reveals interstitial pneumonia, myocarditis and pulmonary arteritis. However, these changes are neither specific nor diagnostic for PRRS.

==Control==

==Control==