Diagnosis of Coccidiosis in Piglets

Various factors should be considered in diagnosing piglet coccidiosis:

• Herd history
  Persistent diarrhoea during the second and third week of life, as well as uneven litters at weaning age.
  
• Clinical picture
  Pasty to watery faeces, white to yellow in colour. No blood in faeces. Low mortality.
  
• Treatment
  Unresponsive to antibiotics.
  
• Demonstration of the parasite according to other signs
  It is not possible to detect oocysts in faeces during the acute phase of neonatal coccidiosis when the first clinical signs appear in a litter. However, presence of the endogenous stages of the parasite in the intestinal epithelium may be confirmed through smears of the small intestine or histopathological findings.
  After the acute stage, examination of the faeces becomes a valuable tool for diagnosing the disease in the herd.

Special care must be taken during faecal sampling and examination in order to ensure an accurate diagnosis of the disease.

Faecal Sampling: Faecal samples should be taken in the second or third week of life. The probability of finding the pathogen in the sample does not necessarily increase by selecting piglets with diarrhoea; diarrhoea can develop before oocysts are excreted in the faeces, and even firm faeces often contain large numbers of oocysts. A certain number of samples is required in all situations. The more samples taken, the greater the probability of identifying a positive farm.  

The sampling of 3 to 5 pigs per litter and at least 10 litters per farm is recommended. Samples from the same litter may be pooled. On large farms, 5 to 10% of litters should be examined.

Faecal examination: Direct examination of faecal smears for oocysts under an optical microscope is not conclusive, but certainly can be successful where massive infestation is present. However, it will generally be necessary to concentrate the samples first. When flotation is carried out, it should be remembered that flotation solutions with higher specific gravity are more suitable.

Flotation solutions with higher specific gravity are more suitable for use when flotation is to be carried out. A saturated NaCl solution with 500 g added glucose per litre can be used as flotation medium. This yields higher numbers of oocysts, which are also more clearly visible (Henriksen et al.).

Other diagnostic techniques, such as autofluorescence or PCR, are also available for Isospora diagnosis, but are not as commonly used.

Piglet coccidiosis should be differentiated from nutritional deficiencies and viral or bacterial infections.