An introduction to Coccidiosis in poultry

What is coccidiosis?

Coccidiosis is caused by a protozoan parasite called Eimeria or Isospora. There are many different genus’ and species that can infect a wide variety of mammals, birds, reptiles and fish. Typically, Eimeria or Isospora parasites are host specific and cannot infect other species than their target species.

How does coccidiosis occur?

Coccidian parasites must reproduce within cells inside the digestive tract. In poultry, a bird will consume a sporulated oocyst (this means infective, if it is unsporulated it will not cause a productive infection) which will then go on to reproduce inside the lining of the gut. This is where the pathology occurs in the disease, as some Eimeria species when present in sufficient numbers cause severe enteritis and necrosis of the gut. After replicating in the gut, the infected animal will then shed unsporulated oocysts into their environment. Oocysts need the right conditions (wet and humid) to sporulate (this is a change that occurs within them to enable them to enter animal cells). Once sporulated, the oocyst can infect further birds, with the cycle repeating over and over!

The length of time between consuming an infective oocyst to pathology seen can be anywhere from 4-7 days, dependant on the species of coccidia. Therefore, the infection can start and result in disease in huge numbers of birds in a short space of time, due to its short life cycle. Furthermore, it does not require an intermediate host to replicate in, making the parasite more effective at infecting its chosen host.

What are the signs of coccidiosis?

It is good practice to keep a close eye on your poultry – coccidiosis signs can spring up out of nowhere and before you know it you may have some mortalities. If you spot any of these signs, be sure to investigate further.

Common signs seen in poultry are:

Bloody faeces

Mucous in faeces

Loose faeces/diarrhoea

Ruffled feathers

Quick to shut down

Hunched appearance

Less interactive than peers

Unresponsisve to stimulation

Not eating or drinking

Loss In bodyweight

These signs are not unique to coccidiosis so don’t assume a bird is infected due to seeing one of these. We suggest if you do see any of these signs, don’t hesitate to investigate further and keep a close watch.

What can I do to mitigate coccidiosis infections?

You could investigate a potential coccidia outbreak by calling a vet to do a physical examination, getting the vet to necropsy some of your flock to see if you have widespread infection, or sending faecal samples off for a faecal oocyst counts. Unfortunately, coccidiosis can be hard to treat if widespread and so you should do all you can to prevent infection.

How can I prevent coccidiosis?

Coccidia can live in the environment unsporulated for some time, as long as conditions are suitable, and once the conditions are right it will sporulate. Ideal conditions would be a chicken shed, around drinkers and feeders or in the litter where it is wet and humid due the number of birds. This may be worse in winter as birds will be cooped together in sheds without proper ventilation. This is a breeding ground for coccidia, especially if naïve young birds are exposed. Therefore, ensure your environment is as least suited as possible for coccidia sporulation. Poultry that are kept outdoors will have much lower risk of coccidial infection.

As well as this, good cleaning is essential during and in between housing flocks. The most effective ways of getting rid of oocysts (which are very hardy!) is washing with high temperatures, burning and chemical cleaning with an anti-coccidial disinfectant such as Bio-ocyst.

It is probably best to avoid mixing flocks and different aged birds as they could pass on different coccidial strains and/or some flocks may or may not have immunity. Especially if the birds are young, they will be at much higher risk of mortality due to the disease.

Lastly, you can either vaccinate your flock or provide a coccidiostat in their feed (note this is not common practice for all poultry).

Is coccidiosis really that bad?

After infection the animal itself may recover or die due to the infection. Even if they recover, this will impact weight gain and the feed conversion ratio, leading to economic impact. If the bird survives, they will build some immunity but may still be able to become infected subsequently. They may have survived this outbreak, but an outbreak with a more deadly strain may not be so forgiving.   

The disease is less of an issue in older birds that have been exposed before as they will build up some immunity. Nevertheless it can still be highly pathogenic given the correct circumstances and strain.

If you want to find out more about how to combat coccidiosis, check out the NADIS website for a great summary.