Colibacillosis in Waterfowl
by Dr. Erin Masur
Escherichia coli is a bacteria and part of the normal landscape of many animals’ gastrointestinal tracts (mammals, birds, and humans). There are many types of E. coli, and most of them are non-pathogenic, meaning not associated with illness. Only 10% of E. coli are pathogenic, and “colibacillosis” is the term for when E. coli causes local or systemic infection. This is one of the most common bacterial diseases in laying hens. While the prevalence of colibacillosis in waterfowl is unknown, in chickens, the prevalence is between 9% and 37%, with a lower percentage in meat birds and a higher percentage in layers.
Because E. coli is normally found in the gut of healthy ducks, they shed it throughout their environment. Their fecal material contacts their bedding, bathing, and drinking sources. Any disruption in the balance of microorganisms in the gut allows for more troublesome strains of E. coli to outweigh the good ones. These disruptions could be poor-quality drinking water, spoiled feed, or other bacteria and viruses. When pathogenic E. coli override good bacteria, they damage the finger-like projections (called “villi”) that line the inside of the small intestine. When villi are blunted, the duck’s ability to absorb nutrients is compromised. Inflamed villi may be weak enough to allow E. coli to seep into the free abdomen, causing multi-systemic infection. Rodents and wild birds also harbor E. coli in their gut and spread it via fecal output. If these critters access the same environment as our ducks, they will add to their world’s overall burden of E. coli in their world.
Picture how our ducky friends move through their environment, dipping their bills into the water and through grasses, rapidly fluttering their oral cavity. Due to their curious nature, the oral route is the most common way E. coli is introduced to ducks. Because ducks naturally produce dust and ammonia, overcrowding ducks can lead to another common route of infection, which is the nasal route. This is the most common route when the living quarters have poor ventilation, poor air quality, dust in the air, or ammonia build-up from soiled bedding. Pathogenic E. coli can assume airborne travel on the backs of dust particles if the air is thick enough. Over time, elevated levels of ammonia damage the inner lining of the respiratory tract and impede the duck’s ability to clear toxicants out of the airway. Because of this, respiratory colibacillosis is an eventual consequence of overcrowding ducks. A gradual progression of respiratory colibacillosis presents as poor growth rate, tracheal inflammation, sinus swelling or conjunctivitis.
Just like respiratory colibacillosis takes time to simmer into an outward problem, reproductive colibacillosis may take years to manifest. E. coli entering the cloaca from the outside world climbs to the reproductive tract of laying hens. After several years of silence, this infection could result in lash egg formation or egg yolk peritonitis, two life-threatening and often untreatable consequences. They may become septic, depressed, and anorexic before passing away. It’s more common to see these types of cases during time periods of peak egg production. These cases rarely respond to antibiotic treatment, even if it’s aggressive.
A hen with colibacillosis in her ovaries or oviduct can transmit the infection to her developing duckling as it traverses her reproductive organs. This results in ducklings born with yolk sac infections or infected navels. These ducklings are weak and droopy, with or without pasty butt. The hen may also transmit her infection to her duckling due to fecal material adhering to the shell and penetrating the shell during hatching. The newly hatched duckling may also obtain E. coli as they explore their new world, with the pathogen entering the nasal or cloacal routes. These are the ducklings most likely to suffer from colibacillosis, with illness being most frequent from 2 to 8 weeks old. Ducklings who survive colibacillosis and live to adulthood become silent carriers, with females quietly harboring the infection in their reproductive tracts.
Because colibacillosis is frequently a consequence of conditions such as poor ventilation and overcrowding, it’s more likely to be secondary rather than a primary infection. A primary infection occurs with no other inciting factors, whereas a secondary infection is a consequence of a primary issue. The most common primary conditions that lead to colibacillosis are high ammonia levels, poorly ventilated living quarters, rodent cohabitation, malnutrition, and bacterial infections such as Mycoplasma. This makes obtaining a diagnosis tricky because many factors are at play.
Can we contract E. coli from our ducks? Several operations on our homesteads could pose a risk: egg consumption, meat consumption, and frequent cycles of incubation and brooding. If you are doing frequent hatches, arrange incubators and brooders separate from human living quarters, and vent them to the outdoors. If your ducks are laying, collect eggs promptly. Discard eggs that are cracked or heavily soiled. When processing your birds for meat, be aware that meat consumption is still the most common cause of food poisoning for people. Inexperienced butchers may accidentally contaminate the carcass parts that are being prepared for human consumption, so taking the time to get trained is never a bad idea. Whether personally raised or commercially purchased, all meats should be cooked to the correct internal temperature. When avian strains of E. coli are introduced to the human gut, it can alter the genetic makeup of human E. coli. This has serious implications for antibiotic usage in animal and human medicine.
There are very few prudent reasons to use antibiotics in ducks, but colibacillosis is one of them. Septicemic processes due to colibacillosis are severe and fatal, and several antibiotics are appropriate for use once the infection is confirmed. A good animal veterinarian or a poultry veterinarian is the best resource to get specific dosing recommendations from. These types of antibiotics are meant for large flocks and commercial settings, so they’re tricky to choose, and trickier to dose correctly, so including a veterinarian is the safest choice for you and your ducks.
Avoiding colibacillosis in your ducks and in your homegrown food supply has a lot to do with going back to the basics of animal husbandry. Ventilate, keep rodents and wild birds out of your flock, and prepare your food carefully. Expanding your flock’s numbers should be a critical choice. Evaluate how crowded the living quarters are when everyone is shut in, how labor might increase for you, and if you should create or update your flock’s biosecurity plan. Chicken math is hard, but duck math is harder!
Sources
Goren E. colibacillose bij pluimvee: etiologie, pathologie en therapie [Colibacillosis in poultry: etiology, pathology and therapy]. Tijdschr Diergeneeskd. 1991 Nov 15;116(22):1122-9. Dutch. PMID: 1957296.
Li, Chong, et al. “Escherichia coli O88 induces intestinal damage and inflammatory response through the oxidative phosphorylation and ribosome pathway in Pekin ducks.” Frontiers in Cellular and Infection Microbiology, vol. 12, 17 Aug. 2022, https://doi.org/10.3389/fcimb.2022.940847.
Rodrigo Guabiraba, Catherine Schouler, Avian colibacillosis: still many black holes, FEMS Microbiology Letters, Volume 362, Issue 15, August 2015, fnv118, https://doi.org/10.1093/femsle/fnv118
Sandhu, Tirath. “Duck Health Care.” Cornell University College of Veterinary Medicine, 24 Feb. 2020, www.vet.cornell.edu/animal-health-diagnostic-center/programs/duck-research-lab/health-care.
Dr. Erin Masur is a livestock veterinarian located in the northeast with a passion for small ruminant parasitology. On her own farm, she raises sheep, ducks, and children. You can keep up with her research at EarlyBirdworm.com, or check out her services at SheepRockVet.com. For more frequent updates, you can find her on social media by searching for Sheep Rock Vet or Fork You Farms.
Originally published in the August/September 2024 issue of Backyard Poultry and regularly vetted for accuracy.
