Salmonellosis
Salmonellosis is a bacterial disease caused by a group of bacteria in the genus
salmonella. All species of birds are susceptible to salmonella infection; the outcome
of infection depends on a variety of factors, including age, stress, host species
susceptibility, and bacterial virulence.
Salmonellosis is a common cause of mortality in birds at birdfeeders.
There are many different strains of salmonella. Many different types of animals
can carry salmonella, including rodents. The bacteria live in the intestines and pass
out with the feces. The organism can be spread from bird to bird through direct contact,
or through ingestion of food or water contaminated with feces from an infected bird or
mammal. Carriers of the organism may appear healthy but shed
the organism periodically in their feces.
Clinical/Field Signs
There are no distinctive signs associated with salmonellosis in wild birds. Different
species and ages may exhibit different signs even when infected with the same serovar
(strain). Commonly reported signs include ruffled feathers, droopiness, diarrhea, and
severe lethargy; chronically infected birds often appear severely emaciated. Sick birds
may also be observed to seizure. Diagnosis requires laboratory isolation and identification
of Salmonella sp. from infected tissues in conjunction with findings from a full diagnostic examination.
Lesions
Types of lesions are highly variable; in acute cases, obvious lesions may be completely
absent. Otherwise, livers often become swollen and crumbly with small reddened or pale
spots. Paratyphoid nodules - small tan to white plaques best seen under a microscope -
may develop in the liver and extend into the body cavity. Infected songbirds often have yellow, cheesy nodules visible
on the surface of the esophagus.
Wildlife Management Significance
Losses occur nationwide. No medical treatment is known to completely cure birds infected by this
organism. There are medications that at least temporarily heal the bird, but the disease
organism may persist in the host and be shed to other previously
uninfected birds at a later time.
To reduce the spread of the bacteria, clean feeders with a 10% bleach and water
solution, rinse well and dry. Don't put the feeders back up for one to two weeks, so
that affected birds won't be concentrated in one location. Rake up waste seeds/droppings
below the feeders. Bird feeders with rough surfaces, cracks, or crevices are difficult to
sanitize and should not be used. When using feeders, the location should be changed at
regular intervals. Addition of more feeders may reduce crowding and minimize opportunity
for interaction and contamination. Birdseed should be stored in rodent proof containers.
If you have additional concerns regarding human or pet health, contact your physician,
public health department or veterinarian for more information. If sick or dead birds are
observed at bird feeders, contact the Wildlife division of your state Natural Resource
Agency or Department of Conservation.
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Photo by Milton Friend
Public Health Significance
The salmonella strain usually found in birds may cause illness in people.
This risk can be minimized, however, by following common sense precautions
such as wearing rubber gloves when handling carcasses or droppings and
washing hands afterwards in warm soapy water. Clean feeders in a bucket outside,
rather than in the kitchen sink. It is
also a good idea to discourage pets from ingesting bird carcasses.
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