Salmonellosis

Salmonellosis

Causative Agent

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Lesions of salmonellosis may appear in large flat areas of the esophagus as demonstrated in this evening grosbeak.

Lesions of salmonellosis in the esophagus may also appear as large nodules resembling "cheese" as observed in this house sparrow.

Distribution

Geographic:

Seasonality:

Generally, throughout the year.
In passerine birds, salmonellosis outbreaks are more common at bird feeders during the late winter and early spring, and also during hot periods in the summer when birds are stressed and must congregate for feed and water.
In colonial nesting waterbirds such as gulls, terns and cormorants, outbreaks of salmonellosis are more common early in the summer when the young of the year hatch.

Hosts, Transmission and Life Cycle

Hosts:

Humans, wild and domestic mammals, birds, reptiles and insects.
Most frequently isolated from birds.
Among birds, salmonellosis outbreaks are most frequently reported in association with passerine birds at feeders and colonial nesting waterbirds.

Transmission and Life cycle:

Mammals

Infections are acquired from eating feed contaminated with feces that contains bacteria shed by carrier animals.
Animals can either be healthy, long-term carriers of the bacteria, resistant, or susceptible to the disease.
Salmonella bacteria primarily invade the wall of the intestines causing inflammation and damage.
Infection can spread in the body through the bloodstream to other organs such as the liver, spleen, lung, joints, placenta or fetus, and the membranes surrounding the brain.
Toxic substances produced by bacteria can be released and affect the rest of the body.
Infected animals may shed Salmonella bacteria in their feces for weeks or months.
Salmonella bacteria are tolerant of a wide-range of temperatures and survive for months in soil and water.

Birds

Like mammals, infected birds may shed Salmonella bacteria in their feces for weeks or months.
Crowding, stress, contamination of feed with feces, prolonged stays, and the presence of carriers of Salmonella bacteria promote the regular occurrence of salmonellosis at bird feeders.

Signs and Symptoms

Mammals:

The extent and severity of lesions will depend on the species, age and health status of the host as well as the type of Salmonella.
Generally, the intestines appear bloody and inflamed.
Other signs caused by Salmonella infection include: enlargement of the spleen and lymph nodes, accumulation of fluid and blood in organs such as the lungs, damage to the liver.

Birds:

The extent and severity of lesions will depend on the species, age and health status of the host as well as the type of Salmonella.
Young birds are more severely affected than older birds.
Infected birds may suddenly die or gradually show signs of disease.
Sick birds are depressed and may huddle together with ruffled feathers, unsteadiness, shivering, loss of appetite, increased or decreased thirst, rapid loss of weight, accelerated breathing, watery yellow, green or blood-tinged droppings, and closing of the eyes with swollen and pasted eyelids shortly before death.
Infected birds may show signs of an affected nervous system: blindness, incoordination, staggering, tremors, and convulsions
Feathers around the vent (cloaca) may become matted with feces.
Liver and spleen are often enlarged, and the intestinal tract may show inflammation and hemorrhage.
The inner surface of the crop may thicken into a yellow, cheese-like membrane.

Meat Edible?

The meat of wildlife believed to be suffering from salmonellosis should NOT be consumed NOR fed to domestic dogs or cats. Many domestic cats are reported to become ill after consuming infected birds during salmonellosis outbreaks in songbirds.

Human Health Concerns and Risk Reduction

The probability of humans contracting Salmonella bacteria directly from wildlife is low; however if pet cats are affected the risk to their owners increases.
Contamination of the environment from sewage, manure or effluent from abattoirs contributes to the occurrence of salmonellosis in wildlife.
Efforts to weekly disinfect bird feeders in all parts of a neighbourhood with 1 part bleach to 10 parts water and change wet feed, plus the removal of spilled feed, should reduce the recurrence of salmonellosis outbreaks at feeders.
If a Salmonella die-off has occurred at a feeder, feed should be removed for 1 month to prevent further concentration of birds at the site.
Salmonella bacteria are well-documented disease-causing agents in humans, causing “food poisoning”, which is characterized by acute intestinal pain and diarrhea.
Extra care with personal hygiene is warranted by people such those who maintain bird feeders, bird banders, wildlife rehabilitators and biologists who handle birds or materials soiled by bird feces, even when the disease is not apparent.

Samples for Diagnosis

Bacteria may be cultured and identified from fecal samples from live animals, or tissue from the small and large intestines, lymph nodes of the body cavity, spleen and liver may be taken after death.
In birds, minimally, the entire gastrointestinal system should be submitted for testing.
In birds, the presence of yellow, cheese-like material in the crop is suggestive of Salmonella infection and should be submitted to an appropriate diagnostic lab.

Similar Diseases

Localized die-offs in birds due to Salmonella poisoning may mimic the effects of certain pesticides; apart from laboratory testing, an accurate history of the die-off may help to discern if pesticides had played a role in the die-offs.