Coccidiosis Disease in Poultry: Symptoms and Prevention

Coccidiosis Disease is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue.

Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.

While coccidia can infect a wide variety of animals, including humans, birds, and livestock, they are usually species-specific. One well-known exception is toxoplasmosis caused by Toxoplasma gondii.

Coccidiosis in chickens can be a potentially life-threatening illness in your backyard flock. Chicks are particularly susceptible to coccidia, but chickens of any age can become ill. Coccidiosis disease affects chicks at an early age between 3 – 4weeks old or more depending on the type involved.

1. What is Coccidiosis?

Coccidiosis is caused by a tiny protozoan parasite called coccidia. Coccidia can only be seen with a microscope, but are bigger than bacteria.

They can be found naturally in the environment and there are hundreds of different types of coccidia and each one infects a different species of animal. Chickens have 7 different coccidia species that can infect them.

2. Symptoms of Coccidiosis Disease

Chicks affected by coccidiosis disease will always close their eyes with feathers flying over and will not be able to feed or drink well as usual. There may also be bloody droppings, pale comb and ceasation of egg production in layers.

Coccidia causes illness in chickens by attacking the intestinal lining, causing diarrhea (sometimes bloody, but not always) which then leads to dehydration and malnutrition, and eventually death if not caught and treated immediately.

In some cases, the damage to the intestinal lining can be permanent and the bird may not grow or maintain body weight. Since a chick must eat a coccidia cyst to be infected, it takes a minimum of 2 to 3 weeks for a chick to begin showing symptoms. General lack of vigor or inactivity is usually the first sign, followed by loose, watery stools

3. Clinical Signs of Coccidiosis Disease

Coccidia which are deep tissue invaders such as E. maxima, E. necatrix and E. tenella cause severe necrosis, haemorrhage of the intestinal mucosa, and bloody diarrhoea and may result in death.

Signs include watery and/or bloody droppings, mortality (0-50%), and morbidity (0-100%). Culls appear as pale birds with anaemia, depression, poor weight gain and feed conversion, and a drop in egg production.

4. Prevention of Coccidiosis Disease in Chickens

Poultry farmers should ensure that litter are dried at all times. There should not be spillage of water on the floor. Good brooder hygiene is the best way to prevent an outbreak of coccidia in your chicks. Keep the litter in your brooder dry at all times. Replace the litter if it becomes saturated.

Since newly hatched chicks must be kept at a warmer temperature, the brooder is potentially the perfect environment to allow coccidia to explode in population and quickly infect your chicks. Many chicken keepers prefer to use anti-coccidiosis medications to help prevent a coccidiosis outbreak in their chicks.

One of the best ways to prevent a coccidiosis outbreak is by practicing responsible sanitation and litter management. Coccidia thrive in damp, warm conditions, so wet litter around the waterer is a virtual parasite paradise.

Believe it or not, when the conditions are just right, coccidia can survive for up to four years outside a bird’s body. And these hardy little organisms can be transmitted via boots, equipment, insects and rodents. So you’re going to need a multi-tiered approach to minimize the threat. Here are some suggestions:

• Keep the premises as dry as possible. Coccidia love moisture.
• Never introduce new adult birds into your flock. Birds that appear healthy can be carriers of a number of deadly diseases. Quarantine them first.
• Raise chicks in isolation. Mature birds can pass along diseases and parasites to vulnerable young birds.
• Thoroughly clean and disinfect the brooder between broods. This includes any equipment the chicks will come in contact with. Once the premises are dry, place four to six inches of dry, fresh litter material (wood shavings or a commercial absorbent litter material) on the floor.
• Provide clean water at all times. A typical problem is that brooder bedding or dust (containing feces) gets scratched into the water source. If possible, elevate the waterer slightly. Clean waterers relentlessly. If you wouldn’t be willing to drink the water yourself, it’s not clean enough. And never let the waterer run dry—it will force the birds to search for water in puddles, which are almost certainly contaminated.
• Provide clean bedding. Coccidia are spread through the feces of infected birds. If feces are in the bedding, they’re on the birds’ feathers. And if feces are on the feathers, the birds will ingest them while preening (using their beaks to clean themselves). Replace wet bedding around waterers and add bedding to any problem spots.
• Let sunlight do some of the work. Coccidia hate sunlight. It’s a natural disinfectant. Incorporate as much natural sunlight into your brooder as possible.
• Ask your veterinarian about vaccinating. A commercial coccidiosis vaccine is available, but it’s not beneficial for every flock. Consult your veterinarian before using the vaccine.

Remember, exposure to coccidia isn’t the threat—frankly, it’s unavoidable. Even wild birds carry coccidia. Instead, the serious threat comes from prolonged over-exposure to coccidia in a stressful, unsanitary environment that can overwhelm a bird’s immune system.

5. Treatment of Coccidiosis Disease in Chickens

If your chicks show signs of coccidiosis, you want to treat them immediately. To help reduce the coccidia population and limit the exposure to your chicks, do a complete change of bedding.

Also empty and disinfect all drinkers and feeders with a 10% bleach in water solution before beginning the treatment with an anti-coccidiosis medication. Treat the entire group of chicks by adding the medication to their drinking water according to label directions.

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6. List of Symptoms/Signs of Coccidiosis Disease

Summary on Coccidiosis Disease: Symptoms and Prevention

Frequently Asked Questions About Coccidiosis Disease: Symptoms and Prevention

1. What exactly causes coccidiosis in poultry and how is it different from bacterial or viral diseases?
Coccidiosis is caused by protozoan parasites of the genus Eimeria, making it a parasitic disease rather than a bacterial or viral one. Unlike bacteria or viruses, Eimeria are single-celled organisms with a complex multi-stage life cycle that takes place partly inside the host’s intestinal cells and partly in the environment. This distinction matters because the treatments, preventive drugs, and vaccines used for coccidiosis are completely different from antibiotics or antiviral agents. Standard disinfectants used against bacteria and viruses are largely ineffective against Eimeria oocysts.

2. How do chickens become infected with coccidiosis?
Infection occurs when a bird ingests sporulated oocysts (the infective stage of the parasite) from contaminated litter, soil, water, or feed. Oocysts are shed in the feces of infected or carrier birds and become infective (sporulate) within 1-2 days under warm, moist conditions. Because oocysts are present in virtually every poultry environment, exposure is essentially inevitable for birds raised on litter. The key factor determining whether exposure leads to disease is the dose of oocysts ingested relative to the bird’s level of immunity.

3. Why do some flocks develop coccidiosis even when they are on medicated feed?
Several factors can cause coccidiosis breakthrough even on medicated feeds. The most common reason is the development of drug-resistant Eimeria strains through prolonged use of the same anticoccidial compound without rotation. Other causes include underdosing (birds not consuming sufficient medicated feed due to heat stress or feed refusal), using medicated feed containing ingredients other than the intended anticoccidial (such as probiotics marketed as “medicated”), wet litter conditions creating an overwhelming oocyst challenge, and concurrent immunosuppressive diseases such as Infectious Bursal Disease or Marek’s Disease reducing the bird’s immune response.

4. What is the difference between subclinical and clinical coccidiosis, and which causes more economic damage?
Clinical coccidiosis produces obvious signs such as bloody diarrhea, high mortality, and birds visibly sick. Subclinical coccidiosis produces no visible illness but causes reduced growth rate, poor feed conversion, weight unevenness, and slightly reduced egg production. Subclinical coccidiosis is widely regarded as more economically damaging overall because it goes undetected for longer, affects entire flocks continuously, and its cumulative production losses (feed wasted, reduced weight gain, increased days to market) far exceed those of dramatic but short-lived clinical outbreaks that are quickly recognized and treated.

5. Can coccidiosis infect humans or other animals on the farm?
No. Eimeria species are strictly host-specific, meaning the species that infect chickens will not infect turkeys, ducks, other livestock, pets, or humans. This is a fundamental biological characteristic of the parasite. However, humans, clothing, boots, and equipment can physically carry oocysts between flocks and houses, making farm workers an important vehicle for spreading the disease between pens and farms even though they cannot themselves become infected.

6. How does coccidiosis vaccination work and is it better than using anticoccidial drugs?
Coccidiosis vaccines contain live Eimeria oocysts, either attenuated (weakened by precocious selection) or non-attenuated (full-virulence). When administered at hatch or day 1, the vaccine oocysts undergo a limited cycle of replication in the gut, stimulating a natural immune response. Repeated field exposure through normal litter contact then boosts and maintains this immunity. Vaccination is particularly valuable in long-lived flocks (breeders, layers), antibiotic-free and organic production systems, and situations where drug resistance has become a significant problem. The main advantage of vaccination over drugs is that it establishes sustainable, naturally renewed immunity. The main disadvantage is that immunity takes 3-4 weeks to develop fully, leaving young chicks temporarily vulnerable.

7. Why are ionophore anticoccidial drugs toxic to turkeys but safe for chickens?
Turkeys are inherently sensitive to polyether ionophore antibiotics (monensin, lasalocid, salinomycin, narasin, maduramicin) at doses that are safe and effective in chickens. The exact mechanism of this species difference involves how turkeys metabolize these compounds and their greater cardiac sensitivity to ionophore-induced ion transport disruption. Accidental feeding of ionophore-containing chicken feed to turkeys can cause leg weakness, paralysis, heart failure, and death. This is a critical practical concern in mixed-species poultry operations, and all feed bags must be carefully checked for ionophore content before being given to turkeys.

8. How do I know if my birds have coccidiosis or necrotic enteritis, since the signs can look similar?
Both diseases cause intestinal damage, diarrhea, depression, and mortality, and they frequently occur together since coccidiosis is the primary predisposing factor for necrotic enteritis. Key differences: coccidiosis typically shows bloody or mucoid diarrhea with hemorrhagic intestinal lesions and visible oocysts on microscopy; necrotic enteritis (caused by Clostridium perfringens) produces a characteristic “Turkish towel” appearance of the small intestinal mucosa with a foul-smelling necrotic membrane, and bacteria are seen on smear. Mixed infections are common and require both anticoccidial treatment and appropriate antibiotics. A veterinarian and laboratory confirmation are advisable for accurate differentiation.

9. How long do Eimeria oocysts survive in the environment and how can I reduce their numbers between flocks?
Eimeria oocysts are exceptionally resistant and can survive for months to over a year in moist soil and litter, even at low temperatures. They are resistant to most common disinfectants. Complete eradication from a production site is virtually impossible. However, their numbers can be significantly reduced by complete removal and composting of used litter between flocks, thorough cleaning and drying of housing (desiccation kills oocysts), application of ammonia-releasing compounds (quicklime) or formaldehyde-based disinfectants, and maintaining dry conditions throughout the flock cycle. A downtime period of at least 2 weeks between flocks, combined with litter cleanout, substantially reduces the oocyst challenge for the incoming flock.

10. What are the most important steps to prevent coccidiosis on a poultry farm?
A comprehensive coccidiosis prevention program rests on four pillars. First, use either a properly chosen and rotated anticoccidial drug program in feed (remembering that birds on vaccination must not receive anticoccidials) or a licensed coccidiosis vaccine administered correctly at hatch. Second, maintain dry litter through good ventilation, proper drinker management, and prompt replacement of wet patches. Third, apply all-in/all-out management with thorough cleanout and downtime between flocks. Fourth, avoid or manage risk factors including overcrowding, immunosuppressive diseases, stress, and sudden diet changes that lower the bird’s natural resistance and allow overwhelming oocyst challenge to cause disease.

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