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Coccidiosis in Chickens and Hens

Posted by Justin - Dine A Chook New Zealand on

Microscopic Parasites called Coccidia causes coccidiosis in chickens.

Coccidia infects the digestive tract of all chickens. Yes, that’s right, all chickens. A small number of 'familiar' coccidia is typical in a healthy, adult chicken.

The cause of coccidiosis in chickens is exposure to unfamiliar coccidia. Hens or poultry which are unwell can not fight high levels of coccidia infection. Coccidiosis infection in chickens is a problem, and it is a big problem. It spreads rapidly through the flock as can cause death within a couple of days.

If you are a backyard chicken keeper, it is essential to learn how to recognise the signs of coccidiosis in chickens coccidiosis in chickens. If you already know the signs and symptoms, you need to start immediate treatment with Amprolium or Baycox by Bayer

Coccidiosis in chickens - The Signs

All chickens naturally carry some coccidia in their intestine. The coccidia parasites in small numbers do not cause any symptoms or ill-health. However, signs of coccidiosis that needs treatment include:

  • Bloody or watery diarrhea
  • Lethargy
  • Lack of appetite
  • Pale combs and wattles
  • Droopy posture and wings
  • Ruffled or puffed up feathers
  • Droopy, dull or glazed eyes
  • Poor growth in chicks
  • Death

Most vulnerable chickens are generally:

  • Recently hatched chicks and younger birds that have not yet developed sufficient immunity to the parasite
  • Sick or unwell meaning they are immunocompromised
  • Suffering malnutrition
  • Afflicted with other diseases affecting their immune system
  • Suffering high parasite loads or stress

Coccidiosis is unlikely to harm an average, healthy, adult chicken unless you introduce a new strain of the parasite into the chicken coop. Your hens build a resistance to the coccidia they live with over time. They have little to no resistance or immunity to newly introduced coccidia strains. It is the primary cause of a coccidiosis outbreak in the coop and is more common than you’d think.

Coccidia varies greatly between sites. So much so that your neighbour most likely has different strains than your coop. It is because of this it is so easy to introduce new coccidia. Even dirty shoes from someone else’s coop are enough. Introducing new birds without treating them first is the number one cause.

Coccidiosis in chickens - The Causes

Like most intestinal parasites, the spread of coccidiosis is from the eggs (oocysts). These are laid in the gut of the infected host and passed out through their faeces. The life cycle begins again when these eggs are consumed and hatch in the new host’s intestine. The parasite burrows into the gut lining and impairs digestive function as it multiplies as well as actively produces more oocysts.

Chicken and wild bird faeces spread oocysts. So even if you have the most stringent plans in place, a stray wild bird poop can introduce new Oocysts to your flock. They survive for up to a year in warm, wet conditions. Maintaining a clean, dry coop can significantly reduce the exposure your birds have to oocysts.

Coccidiosis outbreaks occur more frequently with:

  • Warm, wet conditions
  • Unsanitary and overcrowded coop
  • Stress caused by illness, high parasite loads, malnutrition
  • Environmental changes

As “new” coccidia are the leading cause of coccidiosis in healthy chickens, you should be aware of the most common ways they are introduced to your coop. New coccidia can come from:

  • Introducing new birds to the flock – this is the most common cause and can occur even when the birds appear perfectly healthy. Remember, the new birds have resistance to the strain they have, but this can be lethal to your flock.
  • Travelling with your birds and bringing them home again, for example attending a chicken show.
  • A visiting chicken keeper with oocysts on their shoes, clothing or even vehicle tyres.
  • Using equipment that comes from another chicken keeper. Such as buying a preowned coop, feeder or even egg cartons. Any pre-used things coming in must be sanitised, disinfected as well as thoroughly cleaned.

Practising good chicken coop biosecurity is a must. Once you are in the hang of it, honestly it becomes second nature.

Coccidiosis in chickens - Prevention

There are two critical ways to helping prevent coccidiosis in chickens.

  1. Treat young chickens until they can develop immunity to coccidia.
  2. Good coop management, including biosecurity.

See the bottom of this article for the best ways to clean and disinfect a chicken coop without chemicals.

Young chicks must be treated to prevent coccidiosis. While some chicken keepers, in particular, organic chicken keepers, may choose not to treat their younger chicks for coccidiosis, doing so is good practice. Two treatment options available:


Usually, poultry and chickens are vaccinated against coccidiosis when commercially purchased. But don't just assume, ask the question before taking them home. This vaccination is effective against most strains of the parasite. Most importantly, vaccinated chicks should never be fed a medicated feed as this will nullify the protective effects of both treatments.

Medicated feed

Rather than vaccinate, many backyard chicken keepers raise their chicks on a medicated chick starter. This feed contains a coccidiostat also known as anti-coccidiosis medication. It is not strong enough to completely protect the chicks from the disease but is enough protection to help them build the immunity that exists in an adult chicken. Medicated feed should be fed only to chicks. Administer the treatment for up to 8 weeks. This treatment plan aids in preventing Coccidiosis infection in chickens.

Do not consume eggs from chickens that are being treated with medicated feed.

Good coop management can also help prevent coccidiosis in chickens:

  • Provide a nutritious, balanced diet
  • Treat illness and disease
  • Prevent contamination of feed, and water supply chickens consume. A Dine A Chook Feeder and Water system can help with prevent contamination.
  • Regularly clean dishes or feeders
  • Keep the coop dry and clean
  • Avoid overcrowding
  • Prevent contact with wild birds if possible. Bird netting can help.
  • Practice good biosecurity, for example having other chicken keepers change their shoes
  • Only using clean tools in the chicken coop
  • Quarantine and treat new birds before introduction in the flock
  • Give probiotics, especially if they suffer from stress or are likely to be exposed to new coccidia, e.g. when introducing new birds
  • Use Apple Cider Vinegar in the drinking water to help prevent the disease.

Below zero temperatures, direct exposure to sunlight, also, hot, dry conditions will kill oocysts.

How to treat Coccidiosis infection in chickens

Coccidiosis spreads quickly, and the survival of poultry depends on immediate treatment.

While you should always isolate sick birds immediately to prevent the spread of disease if one bird is sick chances are high that the whole group soon will be.

Treatment for coccidiosis is with sulfa drugs or anticoccidial drugs. Amprolium is an anticoccidial drug available without a prescription and is a fast and highly effective treatment for coccidiosis. Use caution when using Sulfamonaides also know as Sulfas. Sulfa drugs can cause a toxic overdose.

The emergence of drug-resistant strains of coccidia may present a significant problem. New methods currently being trialled to help stop the development of drug resistance in coccidia include changing the type of drugs and the "shuttle program" which is a planned change of the first drug in the middle of the bird's growth period.

Recent Scientific Evidence to Support Apple Cider Vinegar as reported in the Polish Journal of Veterinary Sciences showed evidence supporting Apple Cider Vinegar usage. In short, their findings indicated:

  • ACV has an anticoccidial effect in poultry
  • Causes a decrease in the number of coccidial oocytes in the faeces
  • aids in lowering the resistance to drug treatment

Although this study was limited, further research and investigations continue. But so far, that's an enormous thumbs up for ACV and those backyard chicken keepers who want a more holistic approach and not solely rely on drugs or commercially available medications alone. Read the full study

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