The most likely reason your chickens are pooping blood is coccidiosis, a parasitic gut infection caused by tiny organisms called Eimeria that invade and destroy the intestinal lining. This is by far the most common cause of bloody droppings in backyard flocks, and it moves fast. The disease course runs just 4 to 7 days from infection to severe damage, so acting quickly matters.
Before you panic, though, it’s worth knowing that not every reddish dropping is actually blood. Normal cecal droppings (the ones chickens pass a few times a day from a different part of their gut) can look orange, rust-colored, or even brownish-red. These are sometimes mistaken for blood. True bloody stool is bright red, dark brown-black, or has visible clots or mucus mixed in. If what you’re seeing fits that description, keep reading.
Coccidiosis: The Most Common Cause
Coccidiosis is caused by single-celled parasites in the Eimeria family. Seven species infect chickens, and each one targets a specific stretch of the digestive tract. The species that cause the most visible bleeding are Eimeria tenella, which infects the ceca (two pouches near the end of the intestine), and Eimeria necatrix, which attacks the middle of the small intestine. Both burrow deep into the gut wall to reproduce, rupturing blood vessels and causing extensive hemorrhage in the process.
With E. tenella infections, blood literally pools inside the ceca. With E. necatrix, the inside of the small intestine fills with blood, mucus, and fluid. Another common species, E. maxima, causes a reddish-orange or pink discharge rather than frank blood, so the color of what you’re seeing can hint at which parasite is involved.
Infected birds typically eat less, lose weight, look hunched or lethargic, and produce watery or bloody droppings. Young birds between 3 and 12 weeks old are most vulnerable because they haven’t built up immunity yet, but adult birds under stress or exposed to a new strain can also get sick.
How Chickens Get Infected
Eimeria parasites spread through droppings. An infected bird sheds microscopic egg-like structures called oocysts, which need warmth and the right conditions to become infectious. Interestingly, research on E. maxima found that oocysts sporulate (become capable of causing infection) most efficiently in drier litter, around 16% moisture content, and least efficiently in wet, soggy litter above 60% moisture. This means a coop with moderately damp, warm bedding is prime territory for the parasite to thrive and cycle through your flock.
Chickens pick up the oocysts by pecking at contaminated litter, soil, or feeders. Once ingested, the parasites invade gut cells, multiply, and burst out to infect more cells. Each cycle causes more damage to the intestinal wall.
Other Causes of Bloody Droppings
While coccidiosis accounts for the majority of bloody stool cases, a few other conditions can look similar.
Necrotic enteritis is a bacterial infection that sometimes follows or overlaps with coccidiosis. It’s caused by a toxin-producing bacterium that damages the small intestine. The droppings tend to be more brown than bright red, ranging from slight orange to deep brown depending on how much blood is mixed with bile. The intestine itself becomes fragile and filled with foul-smelling brown fluid. The biggest red flag for necrotic enteritis is a sudden spike in deaths with little warning. Birds may appear depressed with ruffled feathers, but some die before showing obvious symptoms. The lesions from necrotic enteritis are typically more severe than those from coccidiosis alone.
Intestinal worms can also cause bloody droppings, particularly with heavy infestations. Small roundworms that live in the lower intestinal tract cause inflammation, hemorrhage, and erosion of the gut lining. A light worm load might not produce visible blood, but a severe infestation can cause bloody stool along with weight loss, reduced egg production, and in extreme cases, death.
Moldy feed containing mycotoxins doesn’t typically cause bloody droppings on its own, but research has shown that certain mycotoxins make coccidiosis significantly worse. Birds exposed to contaminated feed and then challenged with Eimeria develop more severe gut damage and a higher incidence of bloody diarrhea than birds dealing with either problem alone. If your flock’s feed smells musty or looks clumped, it could be compounding an existing infection.
How to Treat an Active Outbreak
The standard treatment for coccidiosis in backyard flocks is amprolium, sold under the brand name Corid. It comes in both liquid and powder forms that you mix into the flock’s drinking water. Amprolium works by starving the parasite of a nutrient it needs to reproduce, which slows the infection enough for the bird’s own immune system to clear it.
Treatment typically runs for 5 to 7 days. During this time, remove all other water sources so every bird drinks the medicated water. Even birds that aren’t showing symptoms should be treated, since they’ve almost certainly been exposed.
One important detail: amprolium works by mimicking and blocking thiamine (vitamin B1). This is how it kills the parasites, but it can also deplete your birds’ B1 levels. After you finish the treatment course, give your flock a vitamin supplement that specifically contains thiamine. Check the label carefully, because some poultry electrolyte products (like Sav-A-Chick) don’t actually include it. A probiotic supplement during recovery also helps the damaged gut lining heal and re-establish healthy bacteria.
If you suspect necrotic enteritis rather than coccidiosis (brown, foul-smelling droppings with sudden deaths), that’s a bacterial infection requiring a different approach. A poultry veterinarian can help distinguish between the two and recommend the right treatment.
Preventing It From Happening Again
Coccidiosis is almost impossible to completely eliminate from an environment where chickens live. The oocysts are remarkably tough and can survive in soil for months. The goal isn’t eradication but management: keeping parasite levels low enough that your birds develop natural immunity without getting overwhelmed.
Litter management is your most powerful tool. Keep bedding dry and clean. Replace wet spots around waterers frequently. Good ventilation helps keep moisture levels down, which disrupts the parasite’s life cycle. Overcrowding concentrates oocysts in a smaller area, so give your birds adequate space.
For chicks, you have two main prevention strategies. Medicated chick starter feed contains a low dose of amprolium that lets chicks build immunity gradually while keeping the parasite in check. The alternative is a coccidiosis vaccine, often given at the hatchery. These two approaches work against each other: the amprolium in medicated feed can interfere with the vaccine’s effectiveness, since the vaccine relies on a controlled low-level infection to build immunity. Choose one or the other, not both.
For adult birds, rotating your flock’s outdoor range when possible reduces parasite buildup in the soil. Regular fecal checks, either through a vet or with a simple microscope setup, let you catch rising parasite counts before they cause clinical disease. Keeping feeders clean and off the ground minimizes contamination from droppings. And if you introduce new birds, quarantine them first, since they can bring Eimeria strains your existing flock has no immunity to.