Chicken Health For Dummies
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Coccidiosis is such a common and serious problem for flock keepers everywhere. Microscopic coccidia parasites are the archenemies of poultry farmers, who must spend tremendous amounts of effort and money to keep coccidiosis at bay. The parasites can multiply to overwhelming numbers in the digestive tracts of chickens, usually young ones, causing bloody or watery diarrhea, poor growth, and death.

Every chicken carries a few coccidia around. You can see what the eggs, or oocysts, look like at the microscopic level in a sample of the droppings.

Most common types of parasite eggs.
Credit: Illustration by Barbara Frake

What makes the difference between healthy chickens with a few coccidia and a flock that’s really sick with coccidiosis? Check out these factors:

  • The number of oocysts eaten: Chickens raised in crowded or unsanitary conditions are exposed to heavy doses of oocysts every day.

  • The strain of coccidia: Some strains are more vicious than others and burrow deeper into the gut.

  • The environment: Coccidia like warm, wet conditions. Freezing weather and drought conditions kill oocysts.

  • The chicken’s age and health status: Chickens develop immunity to coccidia as they grow older. Young chickens between 3 to 5 weeks of age are most susceptible. Chickens that are run down by other diseases or poor nutrition are also more susceptible to coccidiosis.

How to prevent coccidiosis

Besides taking no action and hoping for the best, you have these two choices for preventing a coccidiosis outbreak in your young chickens (you can do one or the other, but not both):

  • Use a medicated starter feed for chicks until they’re 4 months old. The anticoccidial medication in the feed doesn’t kill all the oocysts, but it keeps them down to a dull roar while chicks develop immunity.

  • Have your day-old chicks vaccinated with a coccidiosis vaccine. Some hatcheries offer this service, or you may be able to purchase the vaccine and do it yourself. The vaccine is actually a live, mild strain of coccidia that stimulates chicks’ immunity to natural infection with more aggressive versions of coccidia. After vaccinating chicks, don’t feed medicated feed; doing so defeats the purpose of the vaccine.

Here are important steps to controlling coccidiosis, regardless of whether you medicate, vaccinate, or neither:

  • Keep pens clean and dry, and avoid overcrowding. Keep poop out of feeders and waterers. Coccidia love wet conditions, especially sloppy areas around waterers. Remove wet bedding frequently and replace with dry stuff.

  • Raise chicks on wire-floored brooders. You may need to take this step if the flock has had coccidiosis problems in past years and the environment has become heavily contaminated with oocysts.

  • Treat birds with signs of coccidiosis immediately. Amprolium or sulfa drugs beat back coccidiosis. Check out the appendix for more information about coccidiosis treatments.

How do you know if chickens are suffering from coccidiosis? Chicks are pale and droopy, with ruffled feathers and no appetite. They pass bloody or watery diarrhea. You notice the greatest amount of blood in the droppings four or five days after the signs start, which is also when most deaths occur.

You may see the poor birds walk back and forth to the feeder, crying pitifully, but not eating. Chicks that survive longer than a week are on the road to recovery.

Treatment of coccidiosis

Amprolium or sulfa drugs effectively treat coccidiosis outbreaks. The parasites can develop resistance to these drugs, but so far, resistance isn’t a common problem in backyard flocks. Organic poultry farmers have a tough time controlling coccidiosis, but they have used vinegar in the drinking water or the dried leaves of the wormwood plant in the feed with some success.

Be careful though when administering sulfa drugs. Your birds can easily overdose on it, causing toxic effects, so take care to mix sulfa drug solutions according to label directions.

About This Article

This article is from the book:

About the book authors:

Julie Gauthier is board certified in veterinary preventive medicine. Rob Ludlow is the coauthor of Raising Chickens For Dummies and Building Chicken Coops For Dummies. He runs the leading chicken information resource on the web,

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