Coccidia are parasites that produce infectious sporocysts or oocysts and undergo a characteristic generational change.

These sporocysts or oocysts predominantly affect the gastrointestinal tract of the chickens and thus cause diarrhoea, which can also be bloody depending on the severity of the infection.

After implantation in a host cell, they carry out asexual reproduction and destroy it during cell division (schizogony/merogony). The form of cell division depends on the type of parasite. After asexual reproduction, gametes, the large plasma-rich macrogamets and the flagellated microgamets, multiply sexually. The fertilized female cell, which is surrounded by an envelope, is excreted, where it divides again. As a result of the reduction division, the spores are formed, in which then again the infectious sporozoites are formed.

Coccidiosis has different subspecies. The following three of them are especially important for chicken farmers:

Blind Bowel Coccidiosis

Appendix coccidiosis, also known as red chick clock, mainly occurs in chicks aged 6-8 weeks and causes inflammation of the appendix. Older chickens are hardly ever affected.

Small Bowel Coccidiosis

Again the chicks are the main victims. This type of coccidiosis causes an inflammation of the small intestine, partly with punctiform bleeding and tissue decay of the intestine.

Rectal Coccidioses

This type of coccidiosis preferentially affects the chicken’s rectum and cloaca. Signs of this often fatal infection are, as in the previous types of coccidiosis, watery-mucilaginous, rarely bloody diarrhoea.

The mortality rate in chicks is 80% for coccidia infection and 30% for adult chickens. As a result, the economic damage for fattening farms is enormous. Also the laying performance of infected hens reduces by up to 40%. Coccidiosis is meanwhile the most frequently diagnosed disease.


Coccidial parasites usually spread in a warm, humid and oxygen-rich environment. Here, too, often accompanied by a lack of hygiene. Coccidia are taken in by poultry feed contaminated with excrements or soiled bedding. The tissue parasites, belonging to the genus Eimeria, are extremely resistant and can survive for up to one year, even on the soles of shoes.


If coccidia is suspected, the vet should be consulted directly. It can be determined by a microscopic examination of the chicken excrement, whether it is coccidiosis or not. As mentioned, this chicken disease affects chicks and young hens first and foremost.

Visible warnings would be:

  • Decline in food intake
  • Lethargic behaviour
  • Diarrhoea, sometimes even bloody
  • Puffed-up feathers
  • Dying of chicks and young chickens
If some chicks or young hens with puffed-up plumage are sitting in the corner, it often is already too late, if you do not have the right medication directly at hand!


Infected chickens, in which the disease is not yet too advanced, can be treated with sulfonamides such as sulfachchlorpyrazine or sulfadimidine by coccidieneffective drugs. Toltrazuril and Cloazuril are also considered very effective.

Red chick dormancy is preferably treated with amprolium.


As with many chicken diseases, hygiene is the be-all and end-all of prevention. Regular disinfection and the avoidance of a high occupation density, as well as vaccinations of the chicks cannot completely rule out an infection by the coccidial parasite, but it can contain it and simply minimize the risk.

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