Disease found in garden birds
11 August 2010
Sick birds tend to show general signs of illness such as lethargy and fluffed-up feathers, and sometimes more specific symptoms.
The following gives information on the commoner diseases in garden birds and how to reduce the risk of these infections.
Salmonellosis is a bacterial infection, which is present at a low level in wild bird populations. There are over 2,000 strains of salmonella bacteria. Although many of them normally occur only in one group of animals, they can spread to any other.
Outbreaks in wild birds are characterised by two strains, which are different from those normally seen in people and domestic animals.
Major salmonella outbreaks in the past have caused serious losses in wild birds and spread over wide areas of Britain. Flocking species, such as greenfinches and house sparrows, are most commonly affected. An infected bird is listless and lethargic, tends to stay close to feeders, fails to respond to danger and can be approached closely.
The crop of an infected bird is often distended with ulcerous growths. These show up as swelling of the crop, and can make the bird look puffed up, or be mistaken for a full crop. Many have diarrhoea.
Even though the infected bird tends to continue to eat almost to the end, it will become weak and emaciated. Salmonella bacteria pass out of the body in the droppings, which spread the contamination if they mix with food taken by other birds.
The risk of transmission is greatest where large numbers of birds gather at communal roosts or feeding sites, and poor hygiene at feeding stations can fuel a local outbreak. While most infected birds die, some do not show any symptoms and can act as carriers for quite some time.
Outbreaks are best prevented by keeping all feeding areas and water containers clean and free from droppings. Some types of salmonella are also responsible for food poisoning in man. Therefore, it is very important to exercise good personal hygiene when handling sick or dead birds, and when cleaning the feeders and water containers.
Trichomonas gallinae is a protozoan parasite of the upper digestive tract. It typically affects pigeons and doves in the UK, but since 2005 it has also been seen in garden birds. Greenfinches appear to be particularly susceptible.
Various birds can catch the infection, and confirmed cases have been found even in birds of prey that have fed on infected birds. Trichomonosis causes lesions in the throat of the infected bird, which makes it progressively harder for the bird to swallow its food, and eventually to breathe. The infected bird will eventually die of starvation or possibly choking.
In addition to showing signs of general illness such as lethargy and fluffed-up plumage, affected birds may drool saliva, regurgitate food, have difficulty swallowing or show laboured breathing. Finches frequently have matted wet plumage around the face and beak, and uneaten food in and around the beak. Sometimes it is possible to see swelling in the throat area of an infected bird, and it may stretch its neck in discomfort.
The infection is spread as birds feed one another during the breeding season, and through food and drinking water contaminated with regurgitated saliva. Sick birds, unable to swallow, will spit out food particles, which will then carry the infection. Saliva from a sick bird can also contaminate bird baths.
The higher the concentration of birds at a feeding station, the greater the chance of another bird picking up the infected food particle and exposing itself to the infection.
If a number of birds show symptoms of trichomonosis, it is recommended to stop putting out food and leave bird baths dry until you no longer find sick or dead birds. This will help to disperse the feeding birds and with it reduce the contact between sick and healthy individuals, thus slowing down or halting the outbreak.
Trichomonosis is bird-specific and does not pass on to mammals, including humans.
Aspergillosis is a lung infection caused by the spores of a fungus called Aspergillus fumigatus. The spores are widespread in the environment, and are found particularly in decaying vegetable matter. They are found commonly in birds, but do not appear to affect healthy individuals. They only become dangerous when a bird’s resistance is lowered by stress, disease etc, or if there is a high concentration of spores in the air for the birds to breathe in.
To reduce the risk of this infection, make sure that food in feeders remains fresh and free from moulds. Since straw can harbour this fungus, never put straw into nestboxes, but use dry hay or wood shavings. Aspergillosis is not passed from one animal to another, but each one will have to be in contact with high concentrations of fungal spores.
Coliform infections occur regularly in wild birds, and can be either gastro-intestinal or respiratory in nature. While E. coli is a normal part of the gut flora in many birds, it can become pathogenic at times of stress. Symptoms include unwillingness to eat, loss of body condition, and severe vomiting or diarrhoea.
Outbreaks are best prevented by keeping all feeding areas and water containers clean and free from droppings.
This is a bacterial infection, which can be found in a wide range of bird species, especially those that occur in large flocks such as sparrows, starlings, pigeons, gulls, waders and ducks. The disease spreads by contaminated droppings and can be readily picked up by birds that feed in close flocks. It is very difficult to diagnose, and there is no known treatment.
The best way to control this disease is to remove infected individuals (some can recover and become long term carriers of the disease, so they are best taken to a vet) and maintain good hygiene routine at feeding stations.
The RSPB does not run bird hospitals or a rescue service. The RSPCA (England and Wales), SSPCA (Scotland) and USPCA (Northern Ireland) are the national charities that help and advise on sick and injured birds and animals. Tiggywinkles and The Swan Sanctuary also take in wild birds in need of care.