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''Ascaris suum'' is a member of the Ascarididae family and is the major cause of [[ascariasis]] in pigs. Its life cycle, like all ascarids, is not typical of nematodes as the infectious stage is within the egg. Due to the migratory life cycle of the larval stages this parasite can be the cause of [[Pigmentation and Calcification - Pathology#Post-Hepatic (Obstructive) Icterus|post-hepatic jaundice]] and [[Respiratory Parasitic Infections - Pathology#Ascaris suum|pneumonia]]. The nematode may also be a reservoir of [[Respiratory Viral Infections - Pathology#Swine influenza|Swine influenza]].

''Ascaris suum'' is a member of the Ascarididae family and is the major cause of [[ascariasis]] in pigs. Its life cycle, like all ascarids, is not typical of nematodes as the infectious stage is within the egg. Due to the migratory life cycle of the larval stages this parasite can be the cause of [[Pigmentation and Calcification - Pathology#Post-Hepatic (Obstructive) Icterus|post-hepatic jaundice]] and [[Respiratory Parasitic Infections - Pathology#Ascaris suum|pneumonia]]. The nematode may also be a reservoir of [[Respiratory Viral Infections - Pathology#Swine influenza|Swine influenza]]. The major detremental effects of ''A. suum'' is in the economic loss due to the damage to liver tissue, white spot, and the decreased growth rate of the pigs. Up to 7% of pig liver in the UK is trimmed or condemned at slaughter due to the presence of white spot due to ''A. suum'' infection.

Eggs are shed in the feaces of the host and have a thick proteinacious coat that allows them to exist on pasture for extended periods of time, up to 4 years. The proteinacious coat allows this long survival on pasture and also makes the eggs extremely difficult to destroy with common disinfectants.<br/>

Eggs are shed in the feaces of the host and have a thick proteinacious coat that allows them to exist on pasture for extended periods of time, up to 4 years. The proteinacious coat allows this long survival on pasture and also makes the eggs extremely difficult to destroy with common disinfectants.<br/>

'''Larvae'''<br/>

'''Larvae'''<br/>

The larval stages are migratory, moving through several organ systems before becoming adults. This is the stage of the parasite that is mainly responsible for the clinical signs of ''A. suum'' infection. The larvae hatches from the egg at the L2 stage, from here is migrates from the small intesting to the liver via the hepatic portal vein. Whilst migrating through the liver the larvae create heamorrhagic tracts, these are later repaired with fibrous tissue causing the appearance of '''milk spots'''. From the liver the larvae move to the heart and lungs where they cause the major clinical signs of ''A. suum'' infection. In the heart a high worm burden will seriously reduce the cardiac output and may also cause blockage which can be fatal. The larvae in the lungs will move up towards the treachea which will stimulate the coughing reflex and cause them to be coughed up into the pigs mouth to be reswallowed as adults into the gastrointestinal system.<br/>

The larval stages are migratory, moving through several organ systems before becoming adults. This is the stage of the parasite that is mainly responsible for the clinical signs of ''A. suum'' infection. The larvae hatches from the egg at the L2 stage, from here is migrates from the small intesting to the liver via the hepatic portal vein. Whilst migrating through the liver the larvae create heamorrhagic tracts, these are later repaired with fibrous tissue causing the appearance of '''milk spots'''. From the liver the larvae move to the heart and lungs where they cause the major clinical signs of ''A. suum'' infection. In the heart a high worm burden will seriously reduce the cardiac output and may also cause blockage which can be fatal. The presence of larvae in lungs can lead to diffuse [[Lungs Inflammatory - Pathology#Interstitial pneumonia|interstitial pneumonia]] with haemorrhage, [[Lungs Ventilation - Pathology#Atelectasis (Collapse)|atelectasis]], [[Lungs Circulatory - Pathology#Pulmonary oedema|interlobular oedema]] and [[Lungs Ventilation - Pathology#Emphysema|emphysema]]. The larvae in the lungs will move up towards the treachea which will stimulate the coughing reflex and cause them to be coughed up into the pigs mouth to be reswallowed as adults into the gastrointestinal system.<br/>

*May cause severe pneumonia in calves housed where infected pigs were housed previously

*May cause severe pneumonia in calves housed where infected pigs were housed previously