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The term Ascariasis refers to disease caused by nematode worms of the genus Ascaris. This disease can occur in a number of different species as described below.
In Pigs
Ascaris suum is the primary cause of ascariasis in pigs.
Diagnosis
The disease is most commonly identified by the presence of milk spots on the liver. This is usually an incidental finding at post mortem or during the slaughter process. The discovery of milk spots on the liver will lead to the comdemning of the infected tissue.
Gross Examination
In the early stage of the disease haemorrhagic tracts will be visible through the liver due to the migratory activity of the larvae. In later stages of the disease diffuse white spots on the capsular surface of the liver will be visible due to the fibrosis of these tracts.
- initial haemorrhagic tracts through the liver attributed to the migration of ascarid larvae
- later stages show fibrosis of these tracts as poorly defined, diffuse, white spots on the capsular surface
Microscopic Examination
- initial haemorrhage and necrosis of parenchyma along the tracts
- later repair by fibrous tissue at foci
- inflammatory cell response contains many eosinophils, as well as lymphocytes and macrophages