All Cooped Up: Fowl Typhoid and Pullorum Disease
Reading Time: 4 minutes
What is it? A highly contagious bacterial disease.
Causative Agent: A rod-shaped, facultative aerobic bacteria called Salmonella enterica subspecies enterica serovar Gallinarum and biovar Gallinarum and Pullorum.
Incubation period: 4-6 days.
Disease duration: Infection can be acute or chronic, with birds carrying the disease into adulthood and passing it to their offspring.
Mortality: Very high in young birds, moderately high in older birds.
Signs: Embryos can die in the egg prior to hatching. Birds exhibit depression, drooping wings, huddling, labored breathing, poor appetite, and have thick white paste-like diarrhea.
Diagnosis: A necropsy examination with culture at a state diagnostic laboratory is necessary to confirm the diagnosis.
Treatment: Not recommended.
Pullorum disease and fowl typhoid are both caused by two strains of the Salmonella enterica bacteria. These bacteria affect chickens, turkeys, ducks, geese, quail, guineas, peafowl, pheasants, and various wild birds. These diseases have been virtually eradicated from commercial flocks in most developed countries, but outbreaks in backyard flocks, game birds, and wild birds still happen. Although rare, some mammals such as dogs, pigs, rabbits, and cats can contract these diseases as well.
Birds can contract these diseases either horizontally or vertically. Horizontal transmission occurs from fellow birds in the environment at the same time, and vertical transmission is when bacteria are passed from a hen to her offspring through egg transmission. Lighter breeds are more resistant to these diseases, while heavier breeds are more susceptible.
Horizontally, transmission can occur through the respiratory tract, orally, or through an open wound. The bacteria can be found in the feces of infected birds, so contaminated drinking water or feed is a source of disease. Additionally, birds can contract it through cannibalism or feather picking of infected birds. Bacteria can be mechanically spread through equipment, mammals, wild birds, insects, or owners traveling between farms.
One of the many organ systems affected by these diseases is the ovary, so hens of producing age may lay eggs infected with the bacteria. Zoonotic transmission to humans is unlikely but not impossible. If infected eggs are incubated, chicks will either hatch with the disease or die during development. Even if very few infected chicks hatch, they can soon infect their broodmates through horizontal transmission.
Clinical signs of pullorum disease are usually seen in chicks less than a month old. Infected chicks will be found dead or dying soon after hatching, with signs peaking around two to three weeks old. Chicks will have nonspecific septicemia symptoms, including depression, drooping wings, huddling, labored breathing, poor appetite, and have thick white paste-like diarrhea. Fecal pasting can be seen as well.
Birds that survive into adulthood will be smaller than average, be poorly feathered, and some of the eggs they lay will hatch and become infected chicks. If an older bird becomes infected with these diseases, it will have fewer presenting signs. Usually, the bird doesn’t appear sick other than decreased egg hatchability, decreased production, and reduced fertility.
Fowl typhoid is very similar, with the exception that it affects birds of any age with the same symptoms. Chicks and adults alike will have ruffled feathers, anorexia, weight loss, dehydration, and diarrhea. With both strains of this bacteria, outbreaks can have few or atypical symptoms. Birds will be infected for life, and chronic infections present with weakness, production loss, respiratory problems, and inflamed joints.
Postmortem examinations reveal lesions for both diseases. Pullorum consistently affects the ovary, but almost every organ can develop lesions. Lesions are indistinguishable between the two diseases.
Both fowl typhoid and pullorum disease are diagnosed by a veterinarian. Testing must be conducted at a state diagnostic laboratory. The veterinarian will take samples from live or diseased birds, then conduct serological testing or bacterial isolation typing. Due to the nature of these diseases, your veterinarian will be mandated to report an outbreak for a positive test result or a suspected infection to the state’s Department of Agriculture.
Any animal suspected of being exposed to the disease will be quarantined and tested depending on local regulations. Positive flocks will be depopulated and the area will be decontaminated.
Different antibiotics have been used to treat clinical cases of these diseases in the past, but they do not cure the disease and multidrug resistance is common with S. enterica bacteria. Treatment will not prevent birds from passing the disease on to the next generation. The only real treatment is to cull infected birds, disinfect the living area, and prevent future generations from becoming infected.
Disinfection can be difficult with an S. enterica infection. The bacteria can live for several months to years in the ambient environment, however, they don’t survive in high heat or direct sunlight. Equipment needs to be cleaned with phenol-based disinfectants before use.
Prevention is the only way to protect a flock from these diseases. Since they can be transmitted vertically, it is incredibly important to only buy hatching eggs and chicks from parents that are known to be disease-free. Advocate for your future flocks by asking breeders about the parent bird’s health. The Salmonella bacteria types are one of the agents tested for by the National Poultry Improvement Plan, so flocks that are NPIP certified are safe to buy stock from.
Biosecurity is always a foundational aspect of keeping poultry safe. Keep wild birds and rodents away from your flock as much as possible. Don’t allow visitors if they have sick birds. Clean all equipment prior to use. Be mindful of all feed, bedding, or other materials brought onto your property. Additionally, certain insects, like poultry mites, are known mechanical vectors so preventing and treating infestations quickly is a priority.
All Cooped Up is a collaboration between medical professional Lacey Hughett and poultry specialist at University of Pennsylvania, Dr. Sherrill Davison. Every All Cooped Up publication has been vetted by Dr. Davison.
Originally published in the April/May 2020 issue of Backyard Poultry and regularly vetted for accuracy.