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Other Names: Avian Coccidiosis

Coccidiosis is the clinical illness caused by infection with the protozoan parasite genus Eimeria (coccidia). The nine coccidia which infect chickens are E. acervulina, E. brunetti, E. hagani, E. maxima, E. mitis, E. mivati, E. necatrix, E. praecox and E. tenella. Most of these parasites invade the chicken’s intestinal tract, but some invade other organs, such as the liver and kidney.

Chickens become infected by ingesting sporulated oocysts (coccidia "eggs") from the surrounding environment.
When chickens are exposed to Eimeria early on, as long as there are not excessive levels present in the environment, they will usually develop a natural immunity, without any treatment necessary. However, if their immune system is lowered due to infection with another disease, stress, or exposure to a new species of Eimeria, they may develop coccidiosis.

Large numbers of Eimeria cause damage to the bird's intestinal lining, resulting in leakage of proteins, including plasma into the bowel. This causes a disruption of digestive processes or nutrient absorption, dehydration, anemia, and increased susceptibility to other disease agents.

Clinical Signs

One of the first signs of coccidiosis is reduced feed and water consumption, resulting in slower growth. The bird will be less active and often goes off on their own and appears hunched up with ruffled feathers. Other signs include a change in the appearance of their droppings, which may be runny and an off-color, or tinged with blood.
Signs of Coccidiosis in Chickens


Coccidiosis is diagnosed in chickens through a fecal test on the chicken's droppings. Eimeria eggs can be identified in the feces under a microscope. A Complete Blood Count (CBC) may show decreased red blood cell and total protein level counts in affected birds.


Treatment of coccidiosis involves several important components:
  • Anticoccidial agents. It is initially important to control the coccidia with an anticoccidial agent such as amprolium or toltrazuril, in accordance with the manufacturer's recommendations.
  • Antibiotics: It is important to control secondary bacterial growth by concurrently administering antimicrobials such as tylosin or amoxicillin. When coccidiosis damages the intestinal wall, it leaves the bird more at risk of developing secondary infections, such as necrotic enteritis.
  • Supportive care: It is very important to keep the bird hydrated and comfortable.
  • Environmental/Management Changes. Slow down oocyst sporulation within the environment where birds live by regularly cleaning the area where chickens live, by removal of the feces and soiled bedding, ensuring it is kept dry (perhaps install better drainage or roof to prevent rain), and/or rotate birds to different areas often. Do not overcrowd birds.
There has been an increased emergence of drug-resistant strains of Eimeria, especially after prolonged uses of the drug. Therefore, it is important to conduct a follow up fecal test following treatment, to evaluate whether the drug was effective against the particular strains of Eimeria present.

Clinical Signs

Hunched up with ruffled feathers
Change in droppings (water, mucous, and blood)
Loss of appetite
Loss of condition
Diarrhea/watery droppings
Stunted growth rate


  • History
  • Clinical signs
  • High fecal oocyst counts (over 50,000 oocysts/gram of feces)

Reported Cases

  • Case 1: Necrotic enteritis with coccidiosis in a Broiler chickens Necrotic enteritis associated with coccidiosis was diagnosed in 25-day-old broilers. Six live broilers with a history of increased mortality with birds dying with their legs straight out were submitted for laboratory examination. At necropsy, the mucosa of the jejunum and ileum had a “cloth towel” appearance with loose, small mucosal flakes. Moderate numbers of coccidia were detected by the wet mount technique. The diagnosis of necrotic enteritis was confirmed by histopathology, which revealed necrosis of the upper part of the intestinal mucosa associated with large numbers of both rod-shaped bacteria and coccidia. Ref


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
AmproliumMost be given for 5 days straight to be effective. Dosage should be in accordance with the instructions by the manufacturer.
Toltrazuril6 mg/kg added to drinking water for 2 days. Note - When Toltrazuril is administered, it is important NOT to concurrently give supplements that contain vitamin B, for it will override the effects of the drug.
Sulphonamides2-3 days of daily treatment and repeated in 5 days.
Supportive careKeep hydrated and comfortable. Make sure bedding stays DRY to slow down oocyst sporulation.
Environmental modificationsImprove sanitary practices by regularly cleaning the environment where birds are kept, minimizing persistent mud and wetness, and risk of fecal contamination in feeders and waterers. Do not overcrowd birds. Rotate runs. Treat the ground with dilute bleach or lime to reduce oocysts, followed by monthly rototilling of the soil.
AntibioticsTylosin or amoxicillinMay be beneficial to help control secondary bacterial growth, which could otherwise lead to necrotic enteritis.
Bidens pilosaAdded to the diet at 100 ppm for 3 daysQamar Memon, Fareed et al., 2020; Yang, Wen-Chin et al., 2019
CurcuminAdded to the feed at 100 to 200 mg/kg dailyYadav, Sudhir et al., 2020
L-ArginineAdded to the diet at 1.24 to 1.44%Castro, Fernanda L S et al., 2020; Yazdanabadi, Fatemeh Izadi et al., 2020
Oregano essential oilAdded to the dietSidiropoulou, Erasmia et al., 2020
Supplemental vitamins - Copper and ZincAdded to the dietDos Santos, Tatiane Souza et al., 2020; Bortoluzzi, Cristiano et al., 2020; Bortoluzzi, C et al., 2019
Khaya senegalensis stem bark extractAdded to the diet at 200 mg/kgMuraina, Issa A et al., 2020



  • Clean, disinfect, and refill waterers with fresh water daily. Position them so as to minimize water spillage onto bedding litter, as moisture promotes the growth of cocci.
  • Keep area dry.
  • Do not overcrowd birds.
  • Rotate area where chickens are kept.
  • 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.

Scientific References

Good Overviews


Age Range

Usually occurs in chickens between 1-4 months of age. Chicks under 1 week cannot have coccidiosis.

Risk Factors

  • Chronic wet environment
  • Overcrowding
  • Unsanitary living conditions (large accumulation of feces)
  • Chickens confined to a given area that isn't managed properly.
  • Wet bedding