Common, sometimes deadly for hens

What is it?

Coccidiosis is a common, and sometimes deadly, intestinal disease caused by a parasitic organism that attaches itself to a chicken’s intestinal lining. This parasitic invasion damages the intestinal tract, preventing the host chicken from absorbing nutrients vital to their survival.

Coccidiosis starts with an oocyst, or microscopic egg, that is passed through a chicken’s droppings. The oocyst can lay dormant in soil for up to a year and doesn’t become infectious (sporulate) until the surrounding conditions support its survival.

Sporulation generally occurs in wet, humid conditions between 70 and 90 degrees Fahrenheit that are present for several days. Areas around feeders and waterers are prime real estate for these parasites, especially if these areas are not cleaned and maintained properly.

After sporulation, the oocyst will be ingested by a chicken, typically through eating, drinking, or scratching the ground. Once in the stomach, stomach acid begins breaking down the hard, protective layer surrounding the oocyst. The oocyst then hatches and invades the cell lining of the chicken’s small intestine. The oocyst goes through several life stages and multiplies rapidly, rupturing bowel cells as it continues to proliferate.

All chickens are carriers of various strains of the coccidiosis organism, but not all become infected with the disease. Coccidiosis can also be spread by unknowingly carrying the eggs (oocysts) of these parasites on clothing or equipment, such as shovels or pails, into the flock environment.


Coccidiosis develops quickly, with an incubation period of 4 to 8 days. Symptoms may develop gradually or appear suddenly. It is not uncommon for a chicken to seem fine one day and become very sick or even die the next.

The most common symptom of the disease is blood or mucus in chicken droppings. However, reddish chicken droppings aren’t always an indicator of coccidiosis. Chicken droppings may also appear brownish red in color due to the normal shedding of cecal cells. The only way to know if the droppings indicate an infected bird is to have the droppings tested by a veterinarian.

Other symptoms of coccidiosis can include:

  • Diarrhea
  • Weakness and listlessness
  • Pale comb or skin
  • Blood located at the vent site of the bird
  • Decreased food or water consumption
  • Ruffled feathers
  • Weight loss (in older chickens)
  • Decreased growth rate (in young chickens)
  • Failing to lay eggs or laying eggs inconsistently


Fortunately, coccidiosis is treatable if caught early enough. It is important to treat every bird in the flock to contain the outbreak.

The most popular treatment for coccidiosis is Amprolium, which blocks the parasite’s ability to uptake and multiply. An amprolium product called coccivet is readily available.

Treatment is usually administered by adding Amprolium to the chickens’ water supply, however in some cases, where sick chickens aren’t eating or drinking enough, the medication is given orally.

Treatment usually proceeds for 7 days, though sick chickens often show improvement in as little as 24 hours. In particularly warm, wet, or humid environments, a second dose of the treatment is recommended after a break in between to ensure complete eradication of the infection.

1 drop (.o5ml) to 30ml water and crop feed to the one hen each day for 7 days.  Consider treating the whole flock because if one hen has it, likely others may be incubating that nasty little oocyst too.  Treating a flock is 1 teaspoon (5ml) per 3 litres of water (1.7ml per 1 litre of water).  Make sure this is the only water source they have and keep doing this for 7 days.  There is no information on having to replace the water daily, so if you make up a 3 litre batch, keep it stored and keep using till gone.  Wait a couple of weeks and do the treatment again for 7 days, to get rid of any little buggars that are still incubating. 

Amprolium can also be given on an ongoing basis, as a disease preventative when it’s wet, humid & warm. For more information on treatment and prevention options for your flock, consult your veterinarian.


Observation is your best defence.  Keep your eye on your hens when it’s wet & humid and take action quickly if you see any these symptoms. 

Keep their area clean, especially around the feeders & waterers.   Poo makes great fertiliser so clean up all the poo regularly (check out other posts on hen poo composting). 

You can also use Coccivet as an ongoing preventive too when it’s warm, wet & humid. 

The other thing to consider is probiotics by fermenting their grain.  You can check out our other posts about this.