"What is Coccidiosis and How Does it Affect Chickens?

"What is Coccidiosis and How Does it Affect Chickens?

Health & Safety

Keeping chickens in the back garden has many rewards apart from giving you eggs. Chickens are lovely little birds which if well cared for can live for a very long time. They become attached to the people who keep them and will follow you around the garden in the hope of a titbit falling their way. A constant source of amusement, these raptor-like birds are always very comical unless they are unwell that is.

When chickens are ill although to begin with it can be quite hard to spot, any time you see a bird hunched over, their tails down or just preferring to be on their own – then you know something is not quite right with them. More often than not a chicken will have very loose droppings when they are sick and this could be the first sign of a very nasty disease that affects poultry taking hold namely coccidiosis.

What Coccidiosis is and How it Affects Chickens

The coccidiosis parasite is a particularly nasty creature that causes serious damage to a chickens' gut and in particular the guts' wall. Unfortunately, there are quite a number of coccidiosis and the effects they have on poultry range from being harmless to dangerously life threatening. The six types of coccidiosis (Eimeria) are as follows:

  • E. tenella
  • E. brunetti
  • E. necatrix
  • E. maxima
  • E. mitis
  • E. acervulina

Each of the coccidiosis lives in a preferred area of the gut causing the damage to that specific region but for treatment purposes and the prevention of them taking hold, this is unimportant because more often than not, it is more than one of them that is causing the damage and making your birds so ill.

Understanding the Life Cycle of Coccidiosis

Understanding the life cycle of coccidiosis helps know how to keep on top of this parasite which ultimately means you stand a better chance of controlling it. The first part of the cycle is called an unsporulated oocyst"" which in short is where the egg containing the parasite has yet to develop and it's at this stage that the disease cannot take hold if a chicken ingests any oocysts.

However, it does not take long for the oocyst sporulates to develop and therefore become infectious – this can be as quick as 24 hours if the conditions are right for the parasite to thrive in - namely an environment that's pretty humid and damp. The problem is that the oocyst boasts a thick wall and as such this protects them from both the heat and the cold as well as many commonly used disinfectants. Add all this up and they can survive for years and it makes it incredibly hard to kill them off.

The next stage of the cycle is when a sporulated oocyst gets ingested by a chicken and when chemicals found in their gut start to break down the thick protecting wall thus releasing the sporocyst which is the infective type of the coccidiosis. The sporocysts then transforms into sporozoites and it is these that invade gut wall cells where they replicate causing cells to burst, releasing the next stage of the coccidiosis parasite known as the merizoites.

Once the merizoites are released, they invade and continue to damage and destroy more gut wall cells which in turn means an infection sets in where more oocysts can reproduce. They are then passed out in a chickens' droppings which go on to infect other birds. The frightening thing about coccidiosis is that one occyst can destroy several thousand gut cells in its life cycle. Should a bird ingest a large volume of oocysts, this is really bad news for the bird whereas if they only eat a few and a few thousand of their gut cells are destroyed, they will survive and will even develop a much needed immunity to coccidiosis.

An Extremely Painful Condition

When chickens eat a lot of coccidiosis and a large number of their gut cells are destroyed, it is extremely painful and as such they stop eating and go into a hunched up posture with ruffled feathers looking very sorry for themselves. Any food they do eat will be wasted because the gut is so damaged, they cannot absorb any goodness or much needed nutrients which then leads to weight loss and bad diarrhoea. Blood may even seep into their gut through the damaged gut walls which then leads to the birds suffering from anaemia. If this is the case, birds will have very pale wattles and combs so it's quite easy to see there's a real problem.

Gut Damage Disrupts Natural Balance of Bacteria

When a chickens' gut is damaged, this can disrupt the natural balance of the bacteria found within the gut. If there is an overload of ""bad"" bacteria it can lead to a very serious condition namely blood poisoning and in chickens this is usually fatal.

Good Management is Essential

Good management is essential when keeping chickens and this means that birds are only ever exposed to very low levels of coccidiosis which allows them to build up their own immunity to these nasty parasites. The problem is that some chickens may build up an immunity but they become hosts to the oocysts which they then pass on to other birds in a flock infecting them with larger numbers of oocysts which can prove very damaging.

The chickens most at risk of contracting coccidiosis are battery hens when they are re-homed because they are never exposed to coccidiosis in their young lives so have not built up an immunity. Hence when battery hens are re-homed, they more often than are infected and will develop clinical signs of the disease.


There are three components to treating coccidiosis which are as follows:

  1. Firstly, to kill the coccidiosis in infected birds to prevent further damage. Birds would be treated with an anticoccidial medication
  2. Secondly, it is essential that bacterial disruption in the gut is controlled which can be achieved by treating infected birds with an antibiotic therapy
  3. Thirdly, infected chickens need a tremendous amount of TLC – they need to be kept in a warm, dry environment and be given a probiotic and multivitamins which helps restore the natural flora in their gut – a good product to give recovering chickens is Beryl's.

Prevention is Easier Than Cure

Sheds and chicken houses need to be kept clean and routinely disinfected with a poultry friendly product which will kill off any coccidiosis oocysts. All dirt and grease needs to be removed and then a disinfectant like Interkokask which is a Defra approved product, should be used as this will effectively kill oocysts. You also need to ensure coops and other housing is not too humid which is the perfect environment for coccidiosis to thrive in.

Chickens may need to be kept warm but the humidity levels need to be controlled and lots of ventilation is needed so bedding is kept as dry as possible. There is a vaccine available but for this to be effective, the environment chickens are kept in has to be just right. The way the vaccine is administered is rather complex too which means it is not always a viable option for people who just keep a few chickens in the back garden.


Newsletter icon
Get free tips and resources delivered directly to your inbox.


Pets for StudWanted Pets

Accessories & services


Knowledge Hub


Support & Safety Portal
All Pets for Sale