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==Introduction==

==Introduction==

Porcine reproductive and respiratory syndrome (PRRS) first appeared in the USA in 1987, although subsequent serologic evidence indicated that it had been circulating for some time prior to being recognised. The disease was seen in Europe in 1990 and reported in Humberside in the UK in 1991. PRRS is caused by an arterivirus, and leads to abortions, mortality and reduced growth, significantly impacting pig welfare and production economics worldwide. This disease has emerged as one of the most important diseases of the pig industry across the globe in recent times. Besides Europe and North America, it was identified in China in 1995 and is present in Japan, Vietnam, the Philippines, Malaysia, and Korea among other countries in Asia. Australia, New Zealand, several European countries are currently free of the disease.

Porcine reproductive and respiratory syndrome (PRRS) first appeared in the USA in 1987, although subsequent serologic evidence indicated that it had been circulating for some time prior to being recognised. The disease was seen in Europe in 1990 and reported in Humberside in the UK in 1991. PRRS is caused by an arterivirus, and leads to abortions, mortality and reduced growth, significantly impacting pig welfare and production economics worldwide. This disease is now found in most areas of the world where pigs are raised. Besides Europe and North America, it was identified in China in 1995 and is present in Japan, Vietnam, the Philippines, Malaysia, and Korea among other countries in Asia. Australia, New Zealand, several European countries are currently free of the disease.

==Aetiology==

==Aetiology==

PRRS is an immunosuppressive disease. The virus that causes the disease, PRSS virus, is an arterivirus, within the [[:Category:Arteriviridae|Arteriviridae]] family. The arteriviruses are the only genus contained within the Arterivirdae family, and other members include the agent responsible for [[Equine Viral Arteritis|equine viral arteritis]] and lactate dehydrogenase-elevating virus of mice. The viruses are host-specific and antigenically distinct, and establish persistent infections after invasion.

The virus that causes PRRS is an arterivirus, within the [[:Category:Arteriviridae|Arteriviridae]] family. The arteriviruses are the only genus contained within the Arterivirdae family, and other members include the agent responsible for [[Equine Viral Arteritis|equine viral arteritis]] and lactate dehydrogenase-elevating virus of mice. The viruses are host-specific and antigenically distinct, and establish persistent infections after invasion.

==Transmission and Epidemiology==

==Transmission and Epidemiology==