Changes

===Clinical Signs===

===Clinical Signs===

There appears to be two distinct clinical phases to PRRS: reproductive failure and post-weaning respiratory diseases. When sows are infected, period of acute disease is seen which is characterised by lethargy, inappetance and pyrexia. Severe infections may also be associated with vestibular signs, and death of up to 10% of the sow stock can occur. Reproductive failure is results in increased numbers of stillborn piglets, mummified foetuses, abortions, premature farrowings and weak piglets. Lactating sows often display anorexia and agalactia, which leads to a rise in preweaning mortality. Signs are also seen in the piglets themselves, including a "thumping" respiratory pattern which on post-mortem examination is revealed to be associated with ls a severe, necrotising, interstitial pneumonia. Oedema may be seen around the eyes, and there is considerable variation in the size of piglets within litters.

There appears to be two distinct clinical phases to PRRS: reproductive failure and post-weaning respiratory diseases. When sows are infected, a period of acute disease is seen which is characterised by lethargy, inappetance and pyrexia. These signs are generally mild, but occasionally severe infections can occur which are associated with vestibular signs, and death of up to 10% of the sow stock. The reproductive aspects of the syndrome are seen when sows become infected in the last trimester of pregnancy. Reproductive signs include increased numbers of stillborn piglets, mummification, abortions, premature farrowings and the birth of weak piglets. Lactating sows often display anorexia and agalactia, which leads to a rise in preweaning mortality. Signs are also seen in the piglets themselves, including a "thumping" respiratory pattern which on post-mortem examination is revealed to be associated with a severe, necrotising, interstitial pneumonia. Oedema may be seen around the eyes, and there is considerable variation in the size of piglets within litters.

Post-weaning performance is also affected, with daily live weight gain reduced by up 85% and increases in mortality by up to 25%. Lethargy and a loss of appetites is seen as in adult pigs, and weanling fail to thrive. Breathing is laboured and there may be obvious respiratory distress. The skin can appear red and blotchy, with a rough hair coat.

Post-weaning performance is also affected, with daily live weight gain reduced by up 85%. Mortality in growing pigs can be increased by up to 25% when PRRS is present in the herd. Lethargy and a loss of appetite is seen in weaned pigs, as well as a failure to thrive. Breathing is laboured and there may be obvious respiratory distress. The skin can appear red and blotchy, with a rough hair coat.

Outbreaks of the reproductive form of PRRS reportedly last between one and four months, depending on the initial health status on the pigs and the management of the outbreak. However, the post-weaning respiratory phase can become chronic, creating major production problems.

Secondary infections commonly occur concurrently to PRRS. Bacteria previously reported to be associated with PRRS include ''Streptococcus suis'', ''Escherichia coli'', ''Salmonella choleraesuis'', ''Haemophilus parasuis'' and ''Mycoplasma hyopneumoniae''. Viral infections such as porcine respiratory coronavirus and swine influenza virus are also possible.

Secondary infections commonly occur. Bacteria previously reported to be associated with PRRS include ''Streptococcus suis'', ''Escherichia coli'', ''Salmonella choleraesuis'', ''Haemophilus parasuis'' and ''Mycoplasma hyopneumoniae''. Viral infections such as porcine respiratory coronavirus and swine influenza virus are also possible.

Outbreaks of the reproductive form of PRRS reportedly last between one and four months, depending on the initial health status of the pigs and the management of the outbreak. However, the post-weaning respiratory phase can become chronic, creating major production problems.

===Laboratory Tests===

===Laboratory Tests===