Avian Cholera Waterfowl
Avian cholera in waterfowl is an uncommon disease for backyard poultry, but an ounce of prevention can deter an unwanted disease.
One nice thing about owning waterfowl is their amazing hardiness and resiliency to disease. Those who keep small numbers of ducks or geese in backyard flocks often go a lifetime without experiencing any problems with sick fowl or loss from a major disease outbreak. Nonetheless, there are a few diseases prone to hitting waterfowl if the conditions are right. Fowl cholera is one of these diseases, and all waterfowl owners should be aware of its existence and the signs of flock infection.
Fowl cholera, or “avian cholera,” can infect numerous species of poultry and birds, both wild and domestic. Occasional outbreaks are known to cause devastating losses in waterfowl flocks worldwide, especially in areas with heavy waterfowl production. Periodic outbreaks are common in some areas of Asia. Fowl cholera has also been known to cause significant losses in the commercial turkey industry.
What Causes Fowl Cholera?
A different infective agent causes fowl cholera than those that cause cholera in humans and swine, and it’s a different disease than cholera in humans. The bacteria Pasteurella causes fowl cholera multocida. (There are also two less common, related strains, P. septica, and P. gallicida. Both can cause diseases with cholera-like symptoms in birds.) In human cholera, a bacteria known as Vibrio cholerae is the infectious agent, while swine cholera is caused by a pathogenic virus known as CSFV.
All three Pasteurella bacteria are serious pathogens, easily transmitted, and highly infectious. In the case of P. multocida, not only does it cause illness and devastating losses in poultry, but it can cause atrophic rhinitis in pigs and bovine hemorrhagic septicemia in cattle, and it’s often a significant source of localized infections in humans when contracted through open wounds or breaks in the skin. This is just one example of why cleanliness and tight biosecurity is so important within all poultry and livestock operations.
How Does Fowl Cholera Present?
When most people think of cholera, the first symptom that comes to mind is copious amounts of liquified, acute diarrhea and resulting weakness or death from dehydration. However, the actual devastation that the infection causes within a bird’s body is much more intense and pervasive than just an attack on the intestinal system.
The onset of fowl cholera is usually sudden. In many cases, birds exposed to P. multocida die within 6 to 12 hours after contracting the bacteria. According to the Merck Veterinary Manual, “Fowl cholera should be the first disease suspected in waterfowl.” The first sign of the disease may be a large number of dead birds in a flock, with no previous sign of infection. Highly contagious and lethal, P. multocida can strike without warning. Not all birds die after contracting the bacteria, however. Some can carry chronic infection with slight signs of generalized, low-grade illness. Others can become asymptomatic carriers.
Clinical Signs
Clinical signs vary greatly but may include: Lethargy, loss of appetite, diarrhea, mucous discharge from the mouth, ruffled feathers, and lameness. In older, established birds, such as those in breeder flocks, rapid and labored breathing is often present. A condition of torticollis (wry or twisted necks) may be present due to infection in the meninges (protective lining of the skull and spinal cord sheath). Internally, bacterial infections wreak havoc by causing legions and hemorrhages on the heart muscle, as well as the connective and fatty tissues of the abdomen. Livers usually become enlarged and discolored, and the tissue of the liver becomes friable or easily crumbled. Post-mortem examinations may also reveal nodules in the lungs and pus in the joints. In the case of turkeys, P. multocida often causes a type of pneumonia.
Although symptoms, signs, and the lesions found in post-mortem examination of dead birds can be a fairly good indication that P. multocida bacteria and fowl cholera are present, identification through a bacterial culture is extremely important, as several avian diseases have similar symptoms and clinical findings in post-mortem examinations.
Transmission and Spread of the Disease
Fowl cholera can be found throughout most regions of the world. Both wild and domestic bird populations are affected, and fowl cholera is present in all major migratory flyways. The disease seems to hit waterfowl populations the hardest, and periodic outbreaks in Asia, where ducks are raised commercially, are still common.
The disease can be easily spread between birds within a flock, as well as by migrating waterfowl and songbirds. Infected migratory birds and waterfowl can contaminate domestic flocks if they share the same ponds or other common areas. Secretions from the nasal passages, mouths, and conjunctiva of the eyes can contaminate water and feed and may contain higher levels of bacteria than the feces, although fecal contamination is another source of transmission.
The bacteria proliferate in unsanitary conditions. Standing water, damp bedding, and feces in duck pens make excellent harbors for this deadly pathogen. Being highly contagious and easily transmitted, the bacteria can spread rapidly through flocks that live in congested populations. Humans and other animals can be carriers of cholera bacteria and infection if biosecurity measures are weak. Tools used in pens, such as shovels and rakes, can also transmit the bacteria from flock to flock.
Control and Eradication
Maintaining clean housing and premises, and following strict biosecurity measures and vaccination programs are the best ways to protect a flock.
However, for waterfowl owners with large flocks being raised for meat or eggs, or as breeder birds, maintaining clean housing and bedding can admittedly be a real challenge. This is especially true for those with ducks. The liquid nature of duck feces alone can make maintaining dry bedding somewhat problematic. Developing a long-term plan for cleaning the housing and pens regularly can help eradicate disease risk. If possible, having at least two areas where flocks can be rotated is also beneficial. P. multocida bacteria can thrive for 3 months or more in damp bedding and soil, though heat, drying, and many common disinfectants will kill it. Being able to empty and clean out an area, disinfect it, and let it dry before letting waterfowl reinhabit is beneficial in protecting them from not only cholera but also other diseases.
There are effective vaccines available, and anyone keeping large flocks of waterfowl may want to consider routine vaccination programs for protection.
When birds do become infected, several antibiotics are effective. However, antibiotics for individual birds won’t eradicate the original bacterial source, and the cholera infection may still smolder and recur once the antibiotic regimen has ended. Depopulation of entire flocks often becomes necessary to eradicate the disease once it takes hold.
Keeping clean premises, biosecurity, and vaccinations are all important ways to avoid this disease in your waterfowl flocks.
Sources
https://www.merckvetmanual.com/poultry/fowl-cholera/ fowl-cholera
https://www.michigan.gov/ dnr/managing-resources/ wildlife/wildlife-disease/ wdm/fowl-cholera
https://poultrydvm.com/ condition/fowl-cholera
Poultry Diseases. (2007). Janet Bradbury, Mark Pattison, Paul McMullin eds. 6th Ed. pgs 149-154.
Doug Ottinger lives, works, and writes from his small hobby farm in northwest Minnesota. His educational background is in agriculture with an emphasis in poultry and avian science.
Originally published in the April/May 2024 issue of Backyard Poultry and regularly vetted for accuracy.
