Signs & Symptoms of Coccidiosis in Chickens

Coccidiosis is a severe parasitic infection that can have long-term negative effects on your chickens. Recognize its symptoms so you can provide effective treatment for the disease in a timely manner, minimizing the number of birds who become seriously ill or die.

Free range chickens
Free range chickens on a farm.
credit: AndyRoland/iStock/Getty Images

The 11 Known Species of Coccidia

Coccidiosis is a severe illness that develops in chickens and other birds after they have consumed a parasitic protozoa of the phylum Apicomplexa, family Eimeriidae. Chickens can be affected by 11 known species of coccidia, including:

Eimeria tenella Eimeria necatrix Eimeria acervulina Eimeria brunetti Eimeria maxima Eimeria mitis Eimeria brunetti Eimeria praecox Eimeria acervulina Eimeria hagani *Eimeria mivati

Your vet will determine the exact type of coccidiosis your chickens are suffering from. He will closely examine the size of the oocysts. According to the Centers for Disease Control and Prevention, oocysts are "a hardy, thick-walled stage of the life cycle of coccidian parasites." Oocysts are shed in the feces of chickens who have contracted these parasites.

To formally diagnose coccidiosis, your veterinarian will also examine the location and appearance of internal lesions within the affected bird's body.

Symptoms of Coccidiosis

Chickens develop coccidiosis by consuming oocysts shed in the feces of affected birds. Symptoms typically appear after one to four days. The severity of symptoms may be affected by how many oocysts a specimen has consumed.

The most easily identified symptom of coccidiosis is diarrhea that may or may not contain blood. Other symptoms of coccidiosis are slow growth, decreased feed and water consumption, weight loss and decreased egg production. A significant number of visibly ill birds within your flock signifies coccidiosis. In the event of a severe coccidiosis outbreak, a large number of birds may die.

Oocysts Lurking Everywhere

Birds that have recovered from coccidiosis continue to shed oocysts, which can survive inactive within the environment as long as they are not subjected to extreme temperatures. Oocysts are capable of contaminating virtually everything within your chickens' environment, including the feed, bedding, water and ground. Oocysts can travel if they become attached to items that move, such as your shoes, clothing or equipment.

Treating Your Flock

Young birds are more likely to suffer from coccidiosis; older birds have built up immunity. Chickens who survive coccidiosis infections typically recover within 10 to 14 days.

You can vaccinate a young flock against coccidiosis as well as use anticoccidial medications to prevent and treat outbreaks.