Suspected cases of mycoplasmosis in wild passerine birds

Recently, some birdwatchers from the regions of Laval and Trois-Rivières (Quebec) sent us photographs and videos of sick birds. The examination of these documents leads us to believe that these birds are affected by a Mycoplasma gallisepticum infections. This suspicion is based on the presence of ocular lesions highly characteristic of this infectious condition. That being said, for now we have not been able to confirm the presence of this infection.

Mycoplasmosis, also known as house finch eye disease, is an infectious bacterial disease that affects the eyes and upper respiratory tract of birds. The house finch (Carpodacus mexicanus) is by far the most commonly affected species. This infection has also been documented in other passerines, such as the American goldfinch (Carduelis tristis), the purple finch (Carpodacus purpureus), the evening grosbeak (Coccothraustes vespertinus), and the pine grosbeak (Pinicola enucleator). In the outbreak reported here, infections of a snow bunting (Plectrophenax nivalis) and a northern cardinal (Cardinalis cardinalis) are also suspected.

This disease mainly affects birds on the eastern part of the North America. It is usually observed in proximity of bird feeders. The first episode of avian mycoplasmosis in house finches was described in the winter of 1994. Since then, the disease has spread to all populations of house finches. Populations of house finches have been particularly affected by this disease. However, the frequency of this disease appears to have decreased considerably in recent years, suggesting a certain equilibrium between this pathogen and susceptible birds.

In passerine birds, mycoplasmosis mainly affects the eyes. The disease is characterized by a swelling of the eyelids and redness of the conjunctiva often associated with secretions and crusting. Sneezing and breathing difficulties can also be observed. In extreme cases, the crusts and swelling may cause complete closure of the eyes. These birds have difficulty feeding due to visual impairment; they are often found on the ground, looking for seeds near bird feeders. Consequently, even of this conjunctivitis is not directly fatal, the blindness can be responsible for starvation that can lead to death. In addition, birds become an easy prey for predators.

Bird feeders are potential sites for transmission of this disease. The following recommendations can help to prevent the spread of the infection and will help to keep wild birds healthy:

Photo: House finch infected by Mycoplasma gallisepticum (mycoplasmosis). Eyes closed with swelling of the eyelids, ocular discharges and loss of feathers around the eyes.

• During a known outbreak of mycoplasmosis, temporarily remove bird feeders and bird baths (for one to two weeks) to reduce bird aggregation.
• Clean your feeders and bird baths regularly with a solution of 10% bleach (one volume of bleach for 9 volumes of water). Allow feeders and baths to dry before putting them back in place.
• It is usually not recommended to treat infected wild birds, as the use of antibiotics could lead to the development of a carrier state which could lead to an overall increase in the spread of the disease.

Although Mycoplasma gallisepticum do not affect people, wild birds may be affected by other diseases that can potentially spread to people and pets (for example, Salmonella, Campylobacter and E. coli). It is therefore important to take the following precautions when cleaning bird feeders:

• Brushes and equipment used to clean bird feeders and baths must not be used for other purposes. Keep them outside and away from food preparation areas.
• Wear rubber gloves when cleaning bird feeders and wash your hands and forearms thoroughly with soap and water, especially before eating and drinking. Avoid handling sick or dead birds directly with bare hands.

Report any sick or dead birds to the Canadian Wildlife Health Cooperative. Find your closest regional centre at: http://www.cwhc-rcsf.ca

Stéphane Lair, CWHC – Quebec