Coccidiosis in Chickens

Coccidiosis in Chickens

Coccidiosis can kill your chickens within days if not treated very quickly. Follow Anne's guide on what causes it, how to prevent it and how to treat it.

Coccidiosis - Causes, Treatment & Prevention

What is Coccidiosis?

Poorly hen

Coccidiosis, pronounced cock-sid-ee-oh-sis, is a disease caused by a coccidial oocyst (pronounced oost) the most common of which is 'Eimeria tenella'.

In simple terms, a microscopic parasite (a coccidia) is ingested by the bird, it attaches itself to the lining of the gut, multiplies and becomes an oocyst feeding in the digestive tract of the bird and consequently will make it bleed.

Most of us keeping a few hens will enjoy a lifetime of blissful feathered friendship without ever coming across the lurking nasties that can afflict even the fittest of fowl.

To help with diagnosing all kinds of symptoms we have created a Chicken Checkup Guide.

But forewarned is forearmed ...

Once infected, the bird will be passing these parasites in its poo days before symptoms occur. The most common tell-tale sign, from the most common type of coccidia, is blood in the poo because the parasite makes the gut lining bleed.

There are many types of coccidia but one type will only infect one type of animal i.e a poultry coccidia will not infect a calf or lamb and vice versa. However, treating and curing one type of poultry coccidia does not mean that they cannot be later infected by another type.

The oocyst eggs are passed out through the droppings and this is how it infects other birds. Adult birds can live perfectly well with small infections their whole lives and if you use a preventative tonic like Apple Cider Vinegar & Garlic this can certainly help (I emphasise help) to keep on top of any oocysts and other worms. This 'acid' in the gut will help prevent the formation of the oocyst which does the damage.

However, when egg production drops, there is blood in the poo, the bird is lethargic and generally looking unwell then another treatment is needed. If not treated quickly at this point the bird may die.

Quote from UK DEFRA document (2010) about coccidiosis in poultry:
Coccidiosis caused by E. tenella first becomes noticeable at about three days after infection. Chickens droop, stop feeding, huddle together, and by the fourth day, blood begins to appear in the droppings. The greatest amount of blood appears by day five or six, and by the eighth or ninth day, the bird is either dead or on the way to recovery. Mortality is highest between the fourth and sixth days. Death may occur unexpectedly, owing to excessive blood loss.
More information - DEFRA (AHVLA) Common Diseases in Poultry.

Symptoms and Causes

Hen staying in the nestbox
  • Passing blood in their poo.
  • Drop in egg production.
  • Droopy, hunched, withdrawn chickens with ruffled feathers.
  • Not feeding or drinking.
Causes of infection:
  • Coccidiosis is caused by a parasite (coccidia) found in contaminated ground and damp bedding. It can be transferred on contaminated boots, feedsacks, insects and rodents.
  • Poultry are exposed to the parasite via their droppings, dirty drinkers and damp litter in their housing. Wet areas around drinkers are particular areas of infection.
  • Coccidia can also be found in water that is not kept clean and free of chicken droppings.
  • Young birds and chicks (of all kinds) are most prone to infection and will quickly die if not treated.
  • Overcrowding and intensive rearing of chickens leads to infection passing quickly throughout the flock.
  • Infectious parasites can live in housing that was previously contaminated for a number of months and so will infect new birds when they are introduced.

Cure and Prevention

The Cure:

Lemon Pyle Brahma CockerelAn often used medication, and advised by Vets, is Coxoid*. It is a liquid added to their drinking water for seven days, the egg withdrawal period may be up to 28 days or as advised.

Cleaning their house, their run area, and all utensils regularly with a disinfectant like Nettex Virocur or Virkon S will help eliminate parasites. Virocur and Virkon are DEFRA approved for Poultry Diseases, however, DEFRA does not have an approved list of disinfectants for killing coccidia although there are some available.

For the ground we recommend Stalosan F Powder or Net-tex Ground Sanitising Powder which dries up the area where they live and prevents the dampness that oocysts thrive in. Regular use of a sanitising powder will prevent any further infections. Parasites can live in empty houses, and the ground, for several months.

(Image above: our beautiful Lemon Pyle Brahma Cockerel - Sir Walter)


The answer is vaccination at the earliest age, usually day-old. One commercial vaccine has a brand name of Paracox. If buying birds from a breeder ask if they have been vaccinated or fed on a feed containing a coccidiostat. If buying from an auction - beware!

During growing stages, feed the birds with a feed containing a coccidiostat so that they have built immunity by the time they reach adulthood. However, this type of feed is preventative, not a cure, and there are differences of opinion as to its effectiveness.

If hatching eggs yourself, treat with Coxoid* in their early days, or keep the chicks on a wire floor so they do not stand in their own poo. Birds under three weeks old are seldom infected.

Keep litter dry when housed indoors, particularly with young birds. Clean brooders every day and do not allow birds to walk around in their own poo. If possible, put drinkers on a wiremesh stand so that the birds do not stand in wet bedding.

For adult birds housed outdoors - keep the bedding in the house clean and dry. We do not advise putting drinkers and feeders inside the house unless absolutely necessary (damp contaminated litter is one of the causes of infection). Unless the birds live indoors on a semi-permanent basis, they will only use the house to lay eggs and sleep at night. They do not feed or drink once they have gone to bed.

Honeypot Tripod Drinker with hensIf birds are housed indoors then consider a watering system that will not allow contamination from poo or debris, and that will not spill and make the bedding damp. e.g. Maxi-Cup Poultry Drinker or a large Honeypot Tripod Poultry Drinker.

Outdoor birds need clean ground, their run will need moving regularly so that the ground does not become 'poisoned' (fowl sick). If this is not possible, then a regular cleaning of the ground in the run is necessary to prevent infections.

Oocysts are not necessarily killed by freezing, extreme dryness or high temperatures, and most disinfectants do not work against all coccidia. Apart from specialist disinfectant treatments; steam cleaning, boiling water, or a 10% ammonia solution, are alternatives to eliminate coccidia.

Vigilance is necessary to watch for tell-tale signs. Coccidiosis is most common in young birds over three weeks and their first year or so. Older mature birds are likely to have built up some immunity.

In short, keep the house bedding dry and clean, do not allow contamination of drinking water, and wash drinkers and feeders regularly in disinfectant. Keep the ground in their run clean, dry and disinfect regularly.

I hope you have found this helpful. If you have any questions though please feel free to Message Us.

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Coccidiosis in Chickens is ©Flyte so Fancy 2010, Updated 2023. Author: Anne Weymouth (Director, Flyte so Fancy). Reproduction of part or all of this text is only possible with the express permission of Flyte so Fancy.

* Coxoid is not licenced for use on poultry because it has not been tested on poultry regarding a meat withdrawal period, although it does have a 28 day egg withdrawal. We cannot therefore advise on its use for poultry as we are not qualified to do this and to do so would breach VMD rules. We strongly advise consulting a vet before use.