Trichomonosis: A Deadly Disease in Finches


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by Fiep de Bie

Trichomonosis or trichomoniasis disease in finches has been in the news a lot this summer, as there seem to be more cases than usual. Pathologists and technicians at the Canadian Wildlife Health Cooperative (CWHC) received many calls from concerned bird-watchers all over the Maritimes with reports of sick or diseased birds.

The CWHC have been working hard to identify the cause of the outbreak, and have determined that trichomonosis is the most likely culprit. This common disease is caused by the single-celled parasite Trichomonas gallinae, which can spread from bird to bird through contact with contaminated food or water, or by direct contact with an infected bird. Symptoms of trichomonosis in finches can include lethargy, weight loss, difficulty breathing, and diarrhea, and can be fatal if left untreated. To prevent the spread of this disease, experts advise bird-watchers to avoid feeding wild birds and to keep their bird feeders clean and disinfected.

Trichomonosis: What are the signs of the disease?

Around the feeder, sick birds look puffed up and very lethargic, to the point where they will not even fly away. Frequently, affected finches are seen to have matted wet plumage around the face and beak. The birds’ throats are blocked by the characteristic cankers (nodules or plaques) composed of dead tissue and inflammatory reaction to the parasite. The cankers grow so large that they prevent the bird from swallowing and result in eventual starvation. Diagnosis of trichomonosis relies on post-mortem examination and follow-up laboratory testing. While the lesions of the disease at post mortem are fairly characteristic, confirmation of the presence of the parasite requires microscopic examination of tissues and sometimes additional tests.

Signs of trichomonosis may include difficulty swallowing, regurgitation, weight loss, diarrhea, increased thirst, and an enlarged crop. If the infection is left untreated, affected birds may have difficulty breathing, increased mucus in the mouth, and a discharge from the nares. In addition to these physical symptoms, birds with trichomonosis may show signs of neurological issues, such as circling, head-tossing, or abnormal behavior. In advanced cases, affected birds may be unable to stand or move due to extreme weakness.

Trichomonosis can be difficult to diagnose, as some of the symptoms may correspond to other illnesses or conditions. As such, it is important to seek veterinary advice if there is a suspicion of trichomonosis. A veterinarian can confirm the presence of the disease through a variety of tests, such as a microscopic examination of tissues, blood tests, and culture of the organism.

Trichomonosis: Where did the disease come from?

Trichomonas gallinae is the protozoan parasite that cause trichomonosis. It is a well-known disease in the UK, where an epidemic affected birds (most frequently Greenfinch and Chaffinch) throughout much of the country in 2006 and 2007. Later, it spread throughout Europe.  It is probable that the original parasitic infection in finches originated from pigeons and doves, which can carry the parasite but don’t usually become sick. 

However, it is likely that the majority of current transmissions are from finch to finch. The disease first emerged in the Maritime provinces in 2007 and has since caused summer to fall mortality in regional Purple finch and American goldfinch populations1. In 2016, we had the first confirmed cases from Newfoundland, making the disease present in all Atlantic provinces. 

It is notable that the Atlantic provinces have the closest geographical proximity to the UK and that finch trichomoniasis emerged immediately after the onset of epidemic mortality in British finches2. Research revealed that the genotype found in the parasite affecting Maritime finches is the same as the one that one caused the epidemic in the UK, but it is uncertain how it was transmitted, as bird migration from Europe is an unlikely route of introduction of the disease.

The movement of captive birds by humans, whether deliberate (e.g. cage and aviary birds, game birds, zoological collections) or accidental (e.g. wild bird stowaways or stray racing pigeons) could have occurred; however, there is no available evidence to support or refute this hypothesis. Therefore it remains a big unknown as to why the disease emerged after the epidemic in the UK, an ocean apart.

In recent years, trichomonosis has become an increasingly concerning issue in the United States and Canada. It has been found in wild bird populations throughout the country, most commonly among finches, as well as in doves, pigeons, and passerines. It is known to be spread through direct contact with the parasite, and due to the high prevalence of wild birds, it is likely that it has been transmitted through the movement of infected birds.

It is also possible that the disease has been spread through the importation of infected birds, or the use of contaminated food or water sources. Regardless, it is clear that this disease is a growing problem and further research is necessary to understand the dynamics of transmission and potential methods of control.

The parasite is spread by birds feeding at the same feeding station and dropping food from their mouth, or drinking water contaminated from an infected bird. Feeding platforms may spread the disease more quickly because affected birds will drop or regurgitate seeds. Other birds then end up eating the infected food.

With hanging feeders, the food will fall away from the feeder, but it is still possible to spread the disease. Affected birds feed their offspring and will consequently spread the disease. Raptors can also acquire the disease by eating prey that is affected.

Trichomonosis: What do I do when there are sick finches at my feeder?

It is recommended to stop feeding for at least 2-4 weeks, as feeding stations encourage birds to congregate, thereby increasing the potential for disease spread between individuals when an outbreak occurs. Water can serve to promote survival of the organism. Consider leaving bird baths empty until no sick or dead finches are seen (drying kills the Trichomonas parasite). Discard remaining birdseed into the garbage; wash feeders and bird bath with a bleach and water solution, (then rinse thoroughly and air dry), to keep the birds safe.

It is also important to keep the feeders and bird bath away from areas where feral cats or other wildlife can access them. Feral cats may become infected with Trichomonosis and spread the disease to other birds. In addition, it is important to dispose of carcasses of dead birds correctly (e.g. double bagging, and placing in the freezer for at least 24 hours) to prevent the spread of the disease. Regularly check your feeders for sick or dead birds, and remove them as soon as possible. Finally, contact your local wildlife conservation or health agency for further information and advice.

Trichomonosis: When is it safe to start putting the feeders back up?

The number of outbreaks in our region typically peaks in the late summer to fall, but this year it already emerged at the end of June. Research done by the CWHC suggested that temperature and humidity play a role in the survival of the parasite. Transmission may be more likely during the summer months as trichomonads have better survival in warmer temperatures.

It is important to wait until the late fall before putting the feeders back up, as the risk of infection is still present during the summer months. If possible, it is recommended to wait until after the first frost, which typically occurs in early to mid-October in our region. The CWHC also recommends taking steps to reduce the chance of transmission, such as providing fresh water in a shallow dish and regularly cleaning feeders with a 10% bleach solution. Taking these steps can help reduce the chances of transmission and ensure a safe environment for the birds.

Trichomonosis: To feed or not to feed?

There is a lot of discussion about this and opinions are divided. We all love to see our birds and feeders allow us to see birds at close range. However, considering the risk of the spread of a disease such as trichomonosis or other diseases such as salmonellosis, it is probably better to not feed birds in the summer or perhaps not at all. In the summer, there are adequate food sources in our natural environment.

It is also important to clean bird feeders regularly, as bird droppings can contain both trichomonosis and salmonella. Cleaning bird feeders not only helps prevent the spread of diseases, but also helps keep our birding areas safe and enjoyable for everyone. Additionally, it is important to keep birdbaths and bird baths clean and free of standing water to help prevent the spread of disease. Finally, it is important to avoid overcrowding at bird feeders, as this can lead to spread of disease among birds.

Trichomonosis: Is it there a health threat for humans and pets?

Trichomonas gallinae is a parasite of birds and there is no known health threat to people or to other mammals such as dogs and cats. But it is recommended to wear rubber gloves when cleaning feeders and avoid handling sick or dead birds directly. For instance, use disposable gloves or pick the bird up through an inverted plastic bag.

Let’s hope that with the help of sensible hygiene precautions as a routine measure and the help of considerate bird watchers, the disease won’t be as prevalent as it was earlier this year and years to come.

Trichomonosis is an important disease to be aware of, especially in birds. It can be spread from bird to bird through contact with a contaminated environment or with an infected bird directly. The most effective way to reduce the risk of spread is to practice good hygiene and clean bird feeders regularly. Additionally, bird watchers should avoid handling sick or dead birds directly and use disposable gloves or pick up the bird through an inverted plastic bag. If an infection is suspected, it is important to take the bird to a veterinarian for diagnosis and treatment. An early diagnosis is the key to successful treatment and preventing the spread of this disease.

If you have questions about the disease or about the work the CWHC is doing visit: http://www.cwhc-rcsf.ca/ or download the Trichomonosis fact sheet.

Fiep de Bie Wildlife Technician Canadian Wildlife Health Cooperative Atlantic Veterinary College

Charlottetown, PEI

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