Coccidiosis in Chickens

By Amy Barkley, Livestock Specialist SWNYDLFC

Coccidia is one of the most misunderstood internal parasites that I work with. It is a protozoa that can wreak havoc on a flock over the span of a week, and leave survivors with stunting and production setbacks that will make them much less efficient over the course of their lifetimes. Because this disease can make or break a flock, it's important to understand the disease cycle, preventative measures, and treatment options in the face of an outbreak.

How do coccidia cause disease?

While coccidia are mostly species specific, they are found naturally in the environment. They live in the soil and in the feces from infected individuals. The protozoa survive outside of the host as oocysts, which is basically a parasite egg. Once it gets picked up by a host, it'll start to sporulate as it passes through the gut. The animal will defecate the sporulating oocyst, and once it's picked up again, it'll develop further within the bird and environment into an infective agent with the capacity to reproduce. The third time it's consumed, it will set up residence in the intestines and then shed infective offspring. Each cycle through the bird takes 4-7 days.

During that time, the population of infective protozoa within the birds' environment will increase, resulting in more of these infective coccidia organisms being consumed. Once the population is high enough within the birds' guts, the physical damage from the organism buying into the intestines causes a decrease in nutrient absorption and bleeding into the intestinal tract. The resulting feces of severely infected birds can range from a small amount of blood in solid formed feces to pure blood.

Images caption: Feces from 4 week old laying pullets infected with coccidia. It's important to recognize the difference between sloughed intestinal tissue (this is likely normal!) and bloody feces. Sloughed intestine is pink or reddish in color and tends to be chunky. Click photos to enlarge them.

What birds are at risk?

Chickens, both layers and broilers, are at risk of contracting this infection. If they are not vaccinated or fed a coccidiostat and are put in a challenging environment, you may see the effects of coccidia occur as soon as 3-4 weeks of age. Most chickens develop natural immunity once they are 8-12 weeks old if placed in an environment with a light or moderate challenge. If they are placed in a challenging environment where they are infected at a young age, the infection will overwhelm the immune building response, and they may succumb to the disease rather than build a gradual resistance. Young birds that survive an infection will also develop immunity, but not without lasting damage to the intestine and subsequent performance deficits.

What Makes a Challenging Environment?

Challenging environments are those that have a high population of the organism and/or are susceptible to rapid sporulation and replication of the protozoa. These include:

• Warm temperatures in combination with a wet or moist environment
• Coops where chickens have lived in the last year
• Areas or coops where you have had an outbreak in the past
• Pens where chicks that were previously vaccinated for coccidia have lived
• Increase air flow in pens, especially in brooders
• Clean and disinfect brooders between each flock
• Clean brooders frequently while chicks are present to keep the bedding clean and dry
• Decrease stocking density to aid in keeping bedding dry
• Do not allow young chickens and waterfowl to live together. Waterfowl make the brooder consistently wet, setting you up for failure.
• Keep pens or pastures empty for one year between flocks to reduce the oocyst load in the soil

Managing the Environment to Reduce Exposure

Coccidia will survive in many environments, but reproduce best in warm, humid environments. This can be in the brooder, in the coop, and even on pasture. It's most commonly seen in the brooder where the stocking density of chicks is high, which prevents optimal air circulation and results in retained moisture. You can make the environment less hospitable to the organism by changing some of the following:

• Increase air flow in pens, especially in brooders
• Clean and disinfect brooders between each flock
• Clean brooders frequently while chicks are present to keep the bedding clean and dry
• Decrease stocking density to aid in keeping bedding dry
• Do not allow young chickens and waterfowl to live together. Waterfowl make the brooder consistently wet, setting you up for failure.
• Keep pens or pastures empty for one year between flocks to reduce the oocyst load in the soil

Prevention Through the Use of a Vaccine

Vaccines have been developed for chicks, and many commercial hatcheries give you the option to vaccinate your chicks at hatch. The vaccine is usually cheap - less than $0.50/chick. It's typically applied as a colored gel, which is sprayed on the backs of the chicks as they're packed. The chicks will pick the gel off their box mates during transport and will swallow it. The gel is laced with a low dose of live oocysts, which will naturally develop in the flock, giving the chicks immunity to larger environmental challenges later on. All chicks that are raised in one group should be vaccinated, else the chicks that didn't get the vaccine may become infected naturally with a larger dose of the parasite than what they can handle to build natural immunity. If you opt to vaccinate your chicks, do not provide a medicated feed, or it will negate the vaccine.

Prevention Through the Use of Coccidiostats

If you have had a coccidia outbreak in the past or know that you can't keep a perfectly clean, dry environment, you can elect to feed a coccidiostat in the feed for the first 8-12 weeks of life. There are many feeds available with the additive. Check the tag of the product you're using to ensure that there is no meat or egg withdrawal. This is especially important for meat chickens, which will be slaughtered prior to developing full resistance at 8-12 weeks of age, and will need to be fed medicated feed for the duration of their lives. If you have vaccinated your birds for coccidia at the hatchery, do not feed a coccidiostat - it'll negate the vaccine.

Another important item to note is that coccidiostats aren't classified as antibiotics and are accepted by some organic certifying organizations for use. If you're raising chickens organically, check with your certifying organization to see if you can use this tool.

Treatment in the Face of an Outbreak

While vaccines and coccidiostats are excellent tools, they can't overcome poor environmental management. Sometimes, extreme parasite loads from especially warm, wet environments where chicks are constantly grown out can overwhelm the immune system and cause clinical disease. If You start seeing bloody feces, hunched/ruffled/depressed birds, and death in the flock (especially simultaneously), it's imperative to treat immediately to help resolve the infection.

Dr. Jarra Jagne from the Cornell University College of Veterinary Medicine shares the following over-the-counter treatment options:

• 20% Amprolium soluble powder (Corid) at rate of 1oz/gallon drinking water. Treat for 5 days, mixing new water daily.

OR

• 9.6% Amprolium solution (Corid) at a rate of 1 fluid oz/2.5 gallons of water. Treat for 5 days, mixing new water daily.

You should only need to treat the flock once. All individuals sharing a space must be treated, regardless of if they are showing clinical symptoms. Check the label to ensure that there are no meat or egg withdrawal times, and if there are, adhere to them. It's recommended to contact your veterinarian to test the flock to ensure they are positive for coccidia.

For more information on coccidiosis and other parasites of poultry, you can review Dr. Jarra Jagne's lecture at https://www.youtube.com/watch?v=eoyrnpPYy8M&list=PLxejmk0aFCq_EHp5VBA7jlXGkRqPca7wC&index=5