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Coccidiosis

Coccidia are a group of intracellular protozoan parasites of the phylum Apicomplexa.  Amongst the genera are Eimeria, Isospora, Neospora, Sarcocystis, Toxoplasma and Cryptosporidium.

Although several species of Eimeria are known to infect swine, causing mild transient diarrhoea in individual cases, the major causal agent of swine coccidiosis is Isospora suis, which usually infects piglets within their first week of life. 

Isospora suis goes through development stages both inside the host animal and in the environment.  The target organ of this parasite is the small intestine, where it develops in the mucosal tissue.  Here, the developmental stages give rise to a microscopic egg, called an oocyst.  The oocysts of Isospora suis is excreted with faeces.  It is often impossible to detect oocysts in the faeces of infected piglets during the acute phase of the disease because they are not yet developed, which makes confirmation of a diagnosis difficult. 

Clinical coccidiosis occurs most commonly in piglets in the 2nd and 3rd week of life.  The initial clinical sign is a pasty diarrhoea which becomes fluid (can be slightly frothy) and lasts for up to 5 to 6 days.  The faeces are white to yellow and fatty or creamy, but can also be brownish or greyish.  Blood is never present.  There are typically piglets with diarrhoea and with normal faeces in the same litter.  The piglets affected most will be in poor condition, with a hairy coat.

A diagnosis of neonatal swine coccidiosis due to Isospora suis is based on the clinical signs, herd history, and the demonstration of the parasite.  Faeces should be examined for oocysts.  The disease has to be differentiated from nutritional disturbances and viral or bacterial infections.