Despite progress, layer producers need to remain vigilant against E. coli peritonitis
The US layer industry has made big strides to reduce the prevalence of Escherichia coli peritonitis, but producers still need to guard against losses from this potentially devastating disease, says John Brown, DVM, a senior technical services veterinarian, Zoetis Inc.
“Without efforts to protect layers against peritonitis, I’ve seen increased mortality from the disease persist for as long as 10 weeks,” he says.
E. coli peritonitis — an inflammation of the peritoneum due to the E. coli bacterium — can occur as an opportunistic pathogen secondary to respiratory diseases such as Mycoplasma gallisepticum or infectious bronchitis. However, it’s now known that E. coli can be a primary cause of peritonitis in layers.
“Peritonitis can strike without warning, and in fact, in some cases there are typically few clinical signs other than high mortality. You’ll find dead birds in cages, or in cage-free production, birds tend to be found dead in their nests,” Brown says.
Sometimes, late in lay, E. coli peritonitis will present initially as a slower rise in mortality and is more likely related to calcium depletion and ensuing cloacal prolapse, which enables E. coli to invade the oviduct and abdomen, he continues.
Unfortunately, antibiotics are usually ineffective during an outbreak of E. coli peritonitis. “Antibiotics used to be helpful, but only for a short time,” he comments. “Mortality would drop after a week or so, but when the antibiotics were pulled, mortality would come right back up. Treatment would have to be repeated over and over; the problem was never solved and treatment costs could be tremendous.
“It’s become clear that the best defense is vaccination coupled with strict biosecurity,” Brown continues.
The veterinarian cautions that careful diagnosis is important. Although bacterial peritonitis is commonly due to E. coli, it can be easily confused with peritonitis due to fowl cholera bacteria.
Another problem that can be confused with E. coli peritonitis is nonbacterial egg-yolk peritonitis, which occurs when ova are ruptured into the abdomen by rough handling of birds, when birds are moved after they’ve already started producing or when birds are nervous.
“I always recommend culturing birds with peritonitis to get a proper diagnosis. That’s the only way to make sure that initiating E. coli vaccination is likely to be effective,” he says. The veterinarian suggests culturing the abdomen, liver or spleen, and to obtain a more sterile sample from the field, long bones can be collected for bone marrow culturing.
Routine immunization of flocks for E. coli with a modified-live vaccine is now common in most layer operations, Brown reports, adding that it has helped reduce both mortality and the severity of E. coli peritonitis while easing the financial impact of the disease., “Some producers don’t vaccinate until an outbreak occurs, but I think it’s more cost-effective to vaccinate before the disease strikes,” he adds.
For best results, Brown recommends vaccinating flocks in the pullet house twice. The vaccine is usually sprayed on at day of age, then again during the grower stage at 12 to 14 weeks of age. The vaccine can be administered in water, “but I feel that spraying the vaccine on the birds gives better protection,” he says.
Brown emphasizes that biosecurity is just as important as vaccination for combatting E. coli peritonitis because the more pathogenic forms of the bacterium can be present in the environment. E. coli can be tracked from one poultry house to another and spread via dust from fans. The litter and water can be contaminated with E. coli, which birds can aspirate, resulting in peritonitis.
Good ventilation — particularly efforts to reduce ammonia levels — and water sanitation are an important part of E. coli infection prevention, he adds.
Biosecurity also includes restricting visitors on layer farms, Brown says. Anyone entering a poultry house should be required to wear clean cloths. Visitors must be required to wear coveralls, shoe covers and a hairnet, and everyone should wash hands and use a disinfectant footbath upon entering and leaving. The tires of vehicles entering and leaving the farm should be disinfected. There should be pest control procedures in place.
These measures, coupled with vaccination of layer flocks against E. coli, can go a long way toward controlling E. coli peritonitis and reducing losses from the disease, he says.
 Reducing pathogenic E. coli infection by vaccination. Worldpoultry.net. Accessed January 6, 2015. http://www.worldpoultry.net/Broilers/Health/2009/12/Reducing-pathogenic-E-coli-infection-by-vaccination-WP006966W/
 Colibacillosis in layers: An overview. Technical Update. Hy-Line. Accessed January 6, 2015 http://www.hyline.com/userdocs/pages/tech_update_colibacillosis_ENG_for_web.pdf