Yarmouth Veterinary Center

75 Willow Street
Yarmouth , ME 04096




Coccidia are single-celled microscopic creatures. There are many species of coccidia and some can be found in almost every environment. Most chickens have coccidia in their intestines, even the healthiest birds in the healthiest flocks.


Infected birds pass coccidia oocysts (eggs) in their droppings. In a warm, damp environment the oocysts develop for a day or two and then can infect any chickens that are exposed to them. Oocysts survive many months in the environment and are only killed by freezing or very high temperatures.


Oocysts are spread around in the soil, feed, water and bedding by the chickens, rodents and other animals, and people. Because coccidia are ubiquitous chickens are exposed early in life, usually by 3 to 6 weeks of age. Whether or not a chicken develops coccidiosis (disease caused by coccidia), and how serious the illness is, depends mostly on the bird’s general health status and the number of oocysts it ingests.



Symptoms of coccidiosis can include:

  • Birds often less than 6 weeks old
  • Long or short duration of illness
  • Bloody or white watery diarrhea
  • Slow growth and weight loss
  • Decreased egg production
  • Sudden death



We diagnose coccidia with a fecal test (microscopic exam of the chicken’s dropping.) Infected birds do not consistently pass oocysts in their droppings, so multiple fecal tests from the same birds, or several birds, are sometimes needed.



Careful attention to all aspects of flock management is the key to preventing or minimizing illness due to coccidia; there is not a single treatment or management technique that will control the problem. Factors to consider include:

  • Coccidia cannot be completely eliminated from the environment
  • All chickens are exposed to, and infected by coccidia
  • All chickens have the ability to develop natural immunity to coccidia, and this will usually happen unless the chicken’s immune system is compromised and/or it is exposed to a particularly large amount of coccidia.
  • Chicks brooded on wire are unlikely to develop natural immunity
  • Good nutrition is vital for developing natural immunity
  • Food and water stations should be kept free of droppings
  • There are many theories on ideal management of bedding in the coop and yard; at a minimum, it should be kept reasonably clean and dry by being changed regularly and having the coop properly ventilated.
  • Free-range chickens have fewer problems with coccidia.
  • If coccidia is suspected or diagnosed in one or a few chickens in a flock, moving the entire flock to a fresh pasture or enclosure may prevent a more serious problem.



Amprolium is an over-the-counter medication that can be used for preventing or treating coccidiosis. (The feed company Nutrena has a thorough description of amprolium at http://scoopfromthecoop.nutrenaworld.com/tag/amprolium/) It is not an antibiotic, and there is no issue with drug residue in eggs or meat, so there is no withdrawal time and no prescription required.


For coccidia prevention amprolium-medicated feed is fed to chicks.


For coccidia treatment amprolium powder can be added to the drinking water at ⅓ oz per gallon daily for 2 weeks. If you are considering this option we also recommend that you consider having an exam and fecal test, or at least a fecal test, because of the significant possibility that the problem is not coccidiosis, or that there are problems in addition to coccidiosis.



Sulfa antibiotics, in particular sulfadimethoxine (Albon), can be used to treat coccidiosis. They are not approved for pullets more than 14 weeks old, and cannot be used in egg-laying hens. We have had some success treating severely ill chicks with injectable fluids, syringe feeding and Albon.


Yarmouth Vet Center