The bacteria salmonella causes food poisoning in humans and infections in vertebrates, including birds, reptiles and mammals. There are more than 2,000 species of salmonella, and subgenus I most commonly affects birds. Pigeons are common carriers of salmonella as susceptible reservoirs to the bacteria, which is generally passed through drinking water or dust, food particles and fecal matter in the air. In pigeons, the bacteria causes the disease paratyphus, which manifests in a number of symptoms, though these symptoms might not be apparent until long after the pigeon has contracted the disease.
Symptoms Common to All Animals
From paratyphus in birds to food poisoning in humans, salmonella shows itself in some common symptoms. These symptoms common to all salmonella infections are lethargy, diarrhoea and excessive weight loss. In all species, salmonella can lead quickly to death if untreated, and in birds often the infection is not diagnosed until after many already have died.
Symptoms Specific to Birds
Some salmonella symptoms in birds are evident in group behaviour. Often, birds infected with salmonella will group together, huddle and exhibit a lack of movement. Their heads droop and they shiver. Their droppings are a yellowish green colour, and an examination of the droppings by a veterinarian can confirm a diagnosis of salmonella. A discharge of mucus from the eyes and beak occurs in some bird species, as well as swelling of the eyelids. If birds infected with salmonella reproduce, their eggs can be clear or black. If they hatch, the baby birds often will be paralysed, have diarrhoea and other ailments; many will die quickly.
Symptoms Specific to Pigeons
Salmonella has one of the highest mortality rates of infectious bacterial diseases in pigeons. They are most susceptible to infection during the breeding and moulting period, as their disease resistance is compromised when they are stressed. In addition to the common avian symptoms, pigeons infected with salmonella may contract arthritis, which is evident in their hesitation to move, unsteadiness on their feet and sometimes a complete loss of use of their legs. In the most severe infections, pigeons also can contract conjunctivitis, an eye infection, and excessive thirst. Damage to the heart, kidneys, liver and spleen also occurs, but there are often no outward symptoms of this except in the pigeon's death. This is why pigeons are one of the most dangerous carriers of salmonella; they often exhibit no outward signs of paratyphus until most of the flock has been infected.