Ornithosis, also called psittacosis or chlamydiosis, is a common disease of pigeons and other birds worldwide. It can pass to humans, so it is classed as a zoonotic disease. How pigeons catch it, the symptoms, diagnosis and treatment are set out below.
Please note: this article is general information and is not a substitute for advice from an avian vet or a licensed wildlife rehabilitator. If you have found an injured or sick bird, contact a vet or your local rescue (see our list of pigeon-friendly rescue centres).
What Causes Ornithosis in Pigeons?
Ornithosis is caused by a bacterium, mainly Chlamydia psittaci. Pigeons can also carry Chlamydia avium, a related species found in pigeons and parrots whose risk to people is not yet clear.
C. psittaci has several genotypes (strains), and each tends to be linked with particular groups of birds.
For example, genotype A is typical of parrots, while genotype D is highly virulent in turkeys and can cause high mortality.
Genotypes B and E are the ones most often found in pigeons.
There are also several different species of Chlamydia, and they tend to affect different birds. Pigeons are mostly affected by C. psittaci and sometimes C. avium, whereas chickens are more commonly affected by Chlamydia gallinacea.
Since chlamydiosis is a bacterial disease, it usually responds to treatment with antibiotics.
How Do Pigeons Become Infected?
Many pigeons are Chlamydia carriers even though they are completely asymptomatic.
This means that other birds can pick up the pathogen from them, whether outdoors or in their living enclosures.
However, most healthy pigeons do not develop any symptoms if they have a well-functioning immune system and if other factors aren’t present, either.
There are several different ways in which this infectious disease is transmitted — horizontally from one bird to another and vertically from the parents to the baby pigeons, for example.
Since ornithosis is a zoonotic disease, and besides humans, other mammals can pick it up from birds, too, this means that they can also be vectors for the pathogen.
Some studies suggest that mites and other arthropods may carry it too. However, more often than not, a pigeon will become infected while outdoors and will bring the pathogen to their environment.
There, the rest of the birds will become infected and begin showing symptoms, too, especially if their living enclosures are heavily contaminated, if the weather is cold, if their diets have been changed recently, or if they don’t have enough food or clean water.
When pigeons are transported to racing competitions, for example, they are kept close to other pigeons, so they have a higher likelihood of becoming infected with the pathogen.
The main way the bacterium is transmitted from one bird to the other is by fecal-oral route or by inhaling the pathogens from the contaminated air.
Unfortunately, some birds can be carriers but might not show any symptoms for months or even years.
Symptoms of Ornithosis in Pigeons
While ornithosis causes a number of clinical signs in sick pigeons, the pathogen mostly affects the respiratory and gastrointestinal systems.
Some of the most commonly seen symptoms are the following:
- Nose and eye discharge
- Sinusitis
- Persistent sneezing
- Conjunctivitis
- Strange droppings color (green or yellow)
- Ruffled feathers
- Weakness
- Lack of appetite
- Weight loss
In pigeons, the digestive symptoms are rarely more noticeable compared to the respiratory ones. Some birds can have an inflamed third eyelid, especially if they are young.
Their heads are swollen, they might have persistent inflammation in one eye, and they might try to alleviate their discomfort by scratching the sides of their heads.
Other birds might have severe inflammation of their eyes, some can lose their eyesight, their eyelids are completely closed, and other potentially pathogenic bacteria are involved — so the eye becomes additionally infected with pus-forming germs.
Another respiratory sign that owners can notice is breathing with a half-open beak. Some birds will actually yawn frequently, but they will do so to try to make their breathing more effective.
There are two forms that ornithosis can have in pigeons — acute and chronic.
Typically, the acute form affects young pigeons, and they tend to develop respiratory signs such as wheezing and conjunctivitis, as well as diarrhea.
The chronic form mostly affects adults whose immune system is fully developed.
Many don’t show any symptoms at all, but that does not mean that they are healthy. They could merely be asymptomatic.
Ornithosis Diagnosis
If you see any of the symptoms that we have described above in your pigeons, get in touch with your veterinarian right away.
Ornithosis is a zoonosis, so you might be putting your health in danger by not paying attention to strict hygienic measures that can prevent you from becoming infected or from becoming a carrier.
The vet will collect a number of secretions from your pigeons.
Swabs from the eyes, throat and cloaca, and droppings, are usually tested by PCR. Chlamydia lives inside cells and does not grow on standard culture plates, so routine culture and sensitivity testing is not used to diagnose it.
However, the vet also needs to perform a differential diagnosis between ornithosis and other pigeon diseases, such as infectious catarrh, Paramyxovirus, or Salmonellosis.
Some of these conditions cause similar symptoms, but they have different treatments, so your vet needs to make sure that your pigeons are indeed suffering from ornithosis and not another disease.
How To Treat It
The most common antibiotic used against chlamydiosis in pigeons is doxycycline. There are several different ways in which you can administer the medication to your pigeons.
The vet can recommend the sachet form that you can add to your pigeons’ water, but this can be a relatively unsure way of treating the disease since you have no control over how much water each pigeon drinks.
Giving the birds pills individually is usually a good way of treating them, and this is also done because some might be unable to drink enough water.
Another note we have to make with regard to the antibiotic is that pet owners should avoid giving their pigeons calcium powder supplements during the treatment period.
Unfortunately, calcium binds with doxycycline, which means that it makes the medicine less effective.
Sick pigeons should not be allowed to fly, also because they can easily spread the disease to other birds.
Treatment usually lasts several weeks. Follow your vet’s instructions, as course length depends on the drug, the dose and how badly the flock is affected.
Can ornithosis in pigeons be prevented?
In many bird species, including pigeons, Chlamydiosis is endemic, which means that the likelihood of there existing many adult carriers of the pathogen is very high.
However, you can make sure that you care for your pigeons as best as possible, offer them the best food, and keep their living enclosures always clean.
When you see a bird that shows any respiratory symptoms whatsoever, isolate it from the rest and disinfect the places where the birds spend their time.
One of the worst things about this pathogen is that it can be carried on the host and can dry as a dusty substance that can be carried by wind or can remain on the walls of your pigeons’ living enclosure, for example.
For this reason, excellent hygiene is paramount, and a standard sodium hypochlorite solution and hot water are usually effective enough to kill the bacterium.
Zoonotic Risk
Humans can catch psittacosis from pigeons, sometimes even after brief contact with a single infected bird.
Pigeon fanciers, vets, farmers, as well as wildlife rehabilitators are the categories that are most affected by this disease.
If one of your birds is showing any symptoms, start wearing gloves and a face mask when cleaning your pigeons’ living enclosure or when handling them.
Get in touch with your veterinarian as soon as possible, and make sure that you thoroughly wash your hands before coming in contact with any other surface or person.
In people, the pathogen causes respiratory symptoms, and sometimes even pneumonia.
Rarely, it can spread to other organs and cause complications such as myocarditis or hepatitis. Older people and those with weakened immune systems are at greater risk of severe illness.
Resources:
- Efficacy of doxycycline for treatment of chlamydiosis in flocks of racing and fancy pigeons (opens in new tab)
- Chlamydial infections in feral pigeons in Europe: Review of data and focus on public health implications (opens in new tab)
- Multiple sites of exposure in an outbreak of ornithosis in workers at a poultry abattoir and farm (opens in new tab)
This guide is general information. If a bird is injured or seriously ill, contact an avian vet or a wildlife rescue as soon as you can.
Last updated 1 November 2026 · Health