Coccidiosis is probably one of the worst parasitic infections and accounts for a high percentage of digestive tract infections in birds of prey. Many falconers know it well from personal experience; others (the luckier ones) have only heard about it; yet there are still some who aren’t fully aware of its most dangerous traits. So let’s summarize them.
Coccidiosis is a parasitic disease caused by a parasite known as coccidia. This statement may sound quite basic, but the fact is that there are several groups of coccidia, and not all of them are dangerous for raptors. For instance, coccidiosis that affects poultry or rabbits is never a threat to birds of prey. Raptors have their own specific group of parasitic coccidia known as Caryospora. These are pathogenic (disease-causing) especially for falcons and owls.
• Caryospora infect birds of prey through microscopic oocysts—essentially tiny eggs—that the bird ingests with food. Inside the intestine, these eggs release larvae that burrow into the intestinal lining and multiply, leading to inflammation (enteritis). The clinical signs of coccidiosis include loss of condition, diarrhea (which may be bloody), vomiting, lethargy, loss of appetite, or even sudden death (this is quite typical for hobbies, for example).
• As mentioned, the disease mainly affects falcons and owls—but not all age groups equally. The most vulnerable are young birds (around up to 90 days old). At this age, the stress of starting training can weaken their immune system, making them more susceptible to new infections from the environment or to the flare-up of previously hidden (subclinical) infections.
• But how does a young bird even get infected with coccidia? The most common source is the parents, who shed the parasite’s „eggs“ into the environment through their droppings—without becoming ill themselves. The chick encounters the parasite at a time when its immune system is not yet fully developed; as long as it isn’t under stress, the disease itself doesn’t manifest. The infection source is therefore often a subclinically infected adult bird, but coccidiosis can also develop in a young bird newly brought from a breeding facility.
Diagnosis is primarily based on faecal examination (coprology). It is necessary to collect droppings over three consecutive days and ideally keep them refrigerated until testing. This is because oocysts are shed irregularly, and at room temperature they can mature, which would distort the result.
Can coccidiosis be treated?
Yes, it can. Currently, the recommended treatment is to give sick birds toltrazuril at a dose of 25 mg/kg for three consecutive days, and then repeat the treatment depending on follow-up faecal test results. Other medicines are still described, but at present, toltrazuril appears to be the only reliably effective option due to growing resistance (the pathogen becomes immune to the drug). As a supplement, it is also advisable to give birds probiotics or certain vitamins (e.g., thiamine).
However, it is definitely not a good idea to give toltrazuril preventively without first testing the droppings!
This is because of its significant toxicity to the kidneys and liver, and also because of the high risk of developing resistance.
One of the biggest challenges of coccidiosis is disinfecting the environment. Coccidia oocysts remain infectious in the environment for up to 12 months after being shed and are very resistant to many disinfectants, sunlight, heat, drying, etc. Some authors even use the word „impossible“ when describing efforts to completely eliminate coccidia from a breeding facility. If coccidiosis is already present in the facility, a certain degree of „controlled“ infection is recommended, where young falcons in a contaminated breeding site are regularly treated—and this must be supported by a number of management measures.
The key, therefore, is prevention.
This includes collecting droppings for just three consecutive days, having them tested (in most cases they can even be mailed), and ideally keeping new birds quarantined in relation to others (using dedicated gloves, discarding uneaten food, etc.) until negative test results are confirmed.
Summary:
• Coccidiosis dangerous for birds of prey is caused by different parasites than coccidiosis in poultry or rabbits
• The disease is confirmed in falcons and owls—mainly in young birds
• It manifests with diarrhea, loss of condition, vomiting, or sudden death
• The infection source is another bird of prey (parent, new bird in the collection)
• Diagnosis: faecal examination over three consecutive days
• Treatment: toltrazuril only after proper diagnosis!
• Coccidiosis cannot be completely removed from the environment
• Prevention: see diagnosis + quarantine
