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Avian Coccidiosis

Coccidiosis is a very common protozoal disease of poultry caused by different species of coccidia (Eimeria), which are single celled parasites that live in and damage different parts of the gut wall of their host resulting in nutrient malabsorption, dehydration and blood loss, and make the bird susceptible to secondary infections. Outbreaks in flocks often occur when birds are stressed, overcrowded, and living in poor sanitary conditions. Even seemingly healthy flocks may be infected with coccidia, without showing any signs of disease. Adult chickens exposed to small amounts of coccidia gradually or who have recovered from a previous infection, may develop immunity in their environment. However, if their immune system is lowered due to infection with another disease, stress, or exposed to new species of coccidia, they may develop coccidiosis.

There are seven different species of Eimeria (coccidia) that affect chickens which include E. acervulina, E. brunetti, E. maxima, E. mitis, E. necatric, E. praecox and E. tenella. The majority of coccidia cause intestinal coccidiosis, and one species causes caecal coccidiosis. More than 1 species of coccidia can infect the same chicken at the same time. The severity of the disease in affected chickens varies from mild to severe, depending on the levels of coccidia present, site of infection, and the age and health status of the bird.

Eimeria Life Cycle

Eimeria are maintained in flocks through a complex life cycle. Chickens become infected initially by consuming sporulated oocysts present in contaminated environments. Once infected with the parasite, these chickens will shed the oocysts produced by the organism, thus contaminating the environment. The cycle continues.Eimeria have a short life cycle, varying between 4 to 6 days depending on the species.
Oocysts can survive for up to 18 months in the environment under optimal soil moisture and temperature conditions.

Coccidiosis Treatment

Coccidiosis has traditionally and is still currently primarily treated or controlled through anticoccidial drugs. However, due to their frequent and irrational use, it as caused the development of anticoccidial drug resistance to different Eimeria species. Exploration of alternative treatment methods is currently underway by many researchers worldwide. Some potential alternative methods identified include:
  • Botanicals: Contain several useful compounds such as tannins, flavonids, natural polyphenols, and essential oils which have shown great promise.
  • Vaccinations: Vaccines are available in certain geographic areas, and are available in both live and attenuated forms.

Clinical Signs

Depression (droopiness)
Pale comb
Change in droppings (water, mucous, and blood)
Loss of appetite
Ruffled feathers
Loss of condition
Pasty whitish soiling around the vent
Stunted growth rate
Reduced egg production
Poor egg shell quality


  • History
  • Fecal exam - Identification of oocysts under microscopy.
  • Necropsy


Anticoccidial drugsAmprolium, toltrazuril, and sulphonamides2-3 days of daily treatment and repeated in 5 days.
Supplemental vitaminsMany anticoccidial drugs interfere with the chickens ability to absorb important nutrients; also helps boost their immune system to help them fight off the infection.
AntibioticsMay be needed in some cases depending on the severity of the disease.
Supportive care
Environmental modificationsImprove sanitary practices by regularly cleaning the environment where birds are kept, minimizing risk of fecal contamination in feeders and waterers, and expand enclosure or coop area if overcrowding birds.


  • Clean, disinfect, and refill waterers with fresh water daily, to prevent buildup of potentially pathogenic organisms. Position them so as to minimize water spillage onto bedding litter, as moisture promotes the growth of cocci.
  • Do not overcrowd
  • Don't keep birds in the same enclosed area for extended lengths of time, rotate them periodically to another area
  • Keep chickens of different ages separated
  • Practice good sanitation and minimize accumulation of feces by cleaning at least once a week.
  • Design roost areas over screened dropping pits for feces, to minimize contact birds have with feces.
  • Provide apple cider vinegar in the drinking water (1 tablespoon per 5 gallons of water)
  • Purchase resistant poultry breeds, such as the New Hampshire, Rhode Island Red or Leghorns

Scientific References

Good Overviews


Age Range

Coccidiosis occurs most frequently inchickens between 4 to 5 weeks of age.

Risk Factors

  • Overcrowding
  • Mixing chickens of different ages together
  • Unsanitary living conditions (large accumulation of feces)
  • Stress (recent transport, change of ownership or flock mates, sudden temperature change, bullying, stalking predators, improper handling, injury, etc.)
  • Concurrent disease
  • Poor immune status
  • Introduction of a new chicken into the flock
  • Letting chickens recovering from an illness or injury back out into the flock prior to finishing the course of medication