Host and Husbandry Factors Related to Coccidiosis

Coccidiosis is a multifactorial disease, and the severity and manifestation of the disease varies from one farm to another. Therefore, while developing a control program, it is important to consider several factors for each particular case, such as:

1. Susceptible animals
The usual age range for animals suffering from coccidiosis is from three weeks to one year of age, but cattle remain susceptible to coccidiosis throughout their lives or till they develop acquired immunity.

The susceptibility of the animals is influenced by nutritional status (colostrum supply), stress (overstocking, transport, climate, hygiene, etc.), immune status and the occurrence of concurrent diseases.   

2. Presence of pathogenic coccidia species
Infections with multiple Eimeria species (pathogenic and non-pathogenic) are common in real life situations. The most important species related to the clinical manifestation of the disease in the stable are Eimeria bovis and Eimeria zuernii, although other pathogenic coccidia species may also affect the cattle in the stables, such as Eimeria alabamensis (animals fed on contaminated hay), which is commonly associated with diarrhoeic problems in animals that are released to pasture.

3. Herd history
It is important to determine which animals are at risk on the farm. In some herds, the manifestation of the disease may be related to certain cattle management practices, such as regrouping and transportation, or to weather or feed variations that precipitate the disease in the herd. 

4. Spread of the disease
Boughton (1945) suggested that “carrier hosts” shed relatively fewer oocysts and the susceptible “multiplier hosts” pick up the infection and shed many-fold oocysts into the environment. Exposure to multiplier hosts leads to subclinical or mildly clinical infection in animals exposed to a large number of oocysts in the environment. Calves exposed to a large number of oocysts are likely to develop severe coccidiosis.

Fitzgerald (1962) hypothesized that in feedlots where few oocysts are present, stress factors such as weaning, diet, temperature extremes and other variables make the calves more susceptible to infection and under such conditions the reproductive potential of coccidia in the gut greatly increases.