Preventing Coccidiosis In Chickens – Backyard Poultry

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Coccidiosis in chickens has been a legitimate problem for farmers since the dawn of commercial poultry farming, especially in chicks. Unfortunately, it’s also a common problem for backyard coops and homesteaders alike. Thankfully, today we have some excellent tools at our disposal to control coccidiosis, and these tools are available to us as small poultry keepers.

Coccidiosis in Chickens

Before you tackle the prospect of coccidiosis in your flock, it’s important to understand the challenge at hand. Coccidiosis is not a virus, nor is it a bacteria. Coccidiosis is a protozoan parasite (microscopic single-cell bug). An infection of coccidiosis in chickens occurs when a bird ingests a sporulated oocyst (an infectious coccidia egg), usually from the ground or coop floor.

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What Coccidiosis Does

Coccidia parasites begin to colonize the lining of the gut by infiltrating a single cell in the gut wall. Once inside, these parasites multiply until the cell bursts. When that cell bursts, all the parasites go in search of a new cell. Once the colony establishes itself, it produces new oocysts that shed from the host bird in the feces. This infectious manure goes on to infect the next bird, or reinfect the host bird.

Subclinical Coccidiosis

Coccidiosis in chickens is somewhat inevitable. Chickens that range outside inevitably ingest coccidia from the wild. Mature chickens will build immunity to coccidiosis, much like your body makes antibodies in response to a virus. A bird who has coccidiosis but shows no apparent signs of illness is considered to have a subclinical infection.

Clinical Coccidiosis

When a flock has a clinical infection, you’ll start to see sick chick symptoms such as depression, lethargy, and hunching. Diarrhea and bloody stools are hallmarks of coccidiosis in chickens. These signs are caused by the compounding chain reaction of bursting cells, which breaks down the gut lining and causes gastrointestinal bleeding. Mortality is likely, especially in chicks, mostly due to septicemia (infection of the bloodstream) or hypovolemic shock (bleeding to death). Juvenile birds are far more fragile than adult birds and can’t build immunity to coccidiosis quick enough, which is why coccidiosis kills chicks so easily.

How to Prevent Coccidiosis

Coccidiosis in chickens is avoidable. The best prevention is biosecurity in conjunction with inoculation (vaccination) or the use of coccidiostats. Inoculation and coccidiostats are mutually exclusive, however, so pick one or the other.


First and foremost, you should be buying chicks from an NPIP certified hatchery. These birds are tested and certified to be clean of disease and should arrive sans any infection. Once they’re in your barn, if you follow proper biosecurity measures, you can keep them free of contamination.

Some of the standard biosecurity measures, such as boot washing as you enter the coop, segregation of differently aged flocks, controlling traffic in and out of your barn, and disinfection of equipment will reduce the likelihood of your flock contracting coccidiosis, or any other disease for that matter.

Litter Management

Don’t underestimate the importance of litter management! Wet bedding in poorly ventilated coops gives coccidiosis the perfect environment to reinfect your flock. Infected chickens shed the coccidia oocysts in their manure, and once those oocysts enter the wet bedding of a coop, they sporulate (transition from non-infectious to infectious). If you keep your litter dry, you can stop oocysts from sporulating in the bedding, breaking the cycle of reinfection.


Many commercial hatcheries now offer coccidiosis vaccine options when ordering chicks. I think the word vaccine is a bit misleading, but not entirely incorrect. Much like we receive weakened versions of viruses (known as a modified-live vaccine), chicks are sprayed at one day old with a solution that contains coccidia oocysts. These oocysts are a weakened version of the wild varieties, just like a modified live-virus vaccine. The most common coccidiosis vaccine available from commercial hatcheries is CocciVac® from Merck Animal Health.

Weak Strains

Once the chicks start to preen themselves, they ingest these oocysts, and the weakened coccidia do exactly what wild coccidia do, only to a lesser extent. This weak coccidia strain results in a safe, predictable immune response that will give chicks the opportunity to build an immunity, so when they finally encounter wild full-strength coccidia, they have the tools to combat the infection.

Preventing Coccidiosis In Chickens Backyard Poultry
Medicated chick starter is medicated with a product called amprolium and is specifically used to control coccidiosis in chickens.


Medicated chick feed has long been the standard method of fending off coccidiosis in chickens, and it has a proven track record. The medication in these feeds is usually a product called amprolium, which is designed to control coccidiosis. Using amprolium in chick feed does not kill the coccidia, but instead starves the population in the gut. By weakening the population of coccidia, it stops the colony from completing the entire life cycle, slows them down and gives the chick a chance to build immunity.

Medicated Chick Starter

If you opt to use medicated chick feed, you need to use it starting day one and continue it uninterrupted until the feed manufacturer says to switch. Unfortunately, if you run short of feed and grab a bag of non-medicated feed, you’ve lost the protection of the coccidiostat, so be sure to keep an extra bag just in case.

Amprolium is sold under different names and labeled for different uses. Always use the product appropriately labeled for your species.


Amprolium is the most popular coccidiostat I’ve seen, but it’s not the only one. Additionally, amprolium is also marketed under the name Corid® by Huvepharma. Corid® is used in other species to treat coccidiosis in goats, cattle and other livestock. Corid® is not approved for use in all livestock, so be sure to talk to a veterinarian before medicating animals with Corid®.

Pick One

Anticoccidiaststats and CocciVac® don’t play well together. You’ll need to pick one or the other, because if you feed coccidiostats to a bird that received CocciVac®, then you’ll kill the modified strain of coccidia, defeating the purpose of inoculation altogether.

Natural Alternative

A generally accepted, natural alternative to preventing coccidiosis is adding apple cider vinegar to your chick’s water. The theory goes that the vinegar acidifies the water, making the gut an uninviting environment to coccidia. I believe the apple cider part merely is for palatability. I’ve never seen a university study on the effectiveness of this alternative, and the general opinion of veterinarians and poultry scientists I’ve asked is “Can’t hurt, might help.”

Have you experienced coccidiosis in your flock? Have you used any of these methods of control? Tell us about your experiences in the comments below!

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