All Cooped Up: Infectious Bursal Disease
Reading Time: 4 minutes
All Cooped Up is a new feature, profiling poultry diseases and how to prevent/treat them, written as a collaboration between medical professional Lacey Hughett and University of Pennsylvania poultry specialist Dr. Sherrill Davison.
All Cooped Up: Infectious Bursal Disease
What is it? A highly contagious viral disease that targets the immune system.
Causative agent: Infectious Bursal Disease Virus (IBDV).
Incubation Period: 3-4 days.
Disease Duration: Clinical signs may only last 3-4 days, but survivors will be immunocompromised for life and often suffer from other diseases as a result.
Mortality: Low in meat breeds but can be higher in laying breeds.
Signs: General malaise, loss of balance, diarrhea, lack of appetite.
Diagnosis: Microscopically through culture isolation or postmortem examination.
Treatment: Supportive therapy.
Infectious bursal disease (IBD) is an interesting viral disease that is seen in young chickens and turkeys. It attacks the bursa of Fabricius, an immune organ found in birds that aids in B-cell maturation. B-cells are the part of the immune system that recognize and flag pathogens for destruction for the T-cells.
Bird immunity is closely tied to a well-functioning bursa of Fabricius. In studies, removal of this organ in young chickens resulted in birds with an impaired immune system. The infection process after one contracting IBD has a similar effect. The infection ordinarily doesn’t kill the bird directly; rather, it leaves a door open for another pathogen to come in and do the dirty work.
IBDV is passed through the fecal-oral route. There are a few different strains with varying virulence, and wild birds have also been known to carry IBDV. Those at the highest risk are chicks three to six weeks old. Chicks younger than this can also become sick, but they may not show outward signs because they still benefit from maternal immunity.
After chicks contact the pathogen, there is a three-to-four-day incubation period before clinical signs present. The bird will lay stretched out a lot, appear uncoordinated and weak, and lose its appetite. The flock may exhibit increased vent picking and have diarrhea.
Internally, the virus attacks the immune cells in bursa of Fabricius, spleen, and thymus. If a postmortem examination is done, the bursa of Fabricius, spleen, and kidneys will be swollen. Gross lesions appear on these organs but may be found in other areas; for example, some strains cause hemorrhaging in the leg muscles. In an immunocompromised survivor, the bursa of Fabricius will be damaged and atrophied.
The number of deaths in a flock depends on the virulence of the IBD strain and the breed of bird. Layers are the most susceptible to IBD, with Leghorns being notorious for late adolescent infections. Despite being so contagious, this disease passes quickly. The survivors will appear healthy or recovering in less than a week.
A veterinarian can provide a diagnosis by examining the gross lesions, and from there, will generally send a sample off to be tested for the virus. An official diagnosis of IBD can be made in a lab through gene sequencing to identify the IBDV genotype.
There is no cure for IBD, but there is a vaccine. It can be given as eye drops, subcutaneously, or in the water for the first three weeks of life. In addition to vaccinating the chicks, it is ideal to vaccinate breeder birds while developing because they can pass down immunity to their chicks. If a flock does get IBD, supportive care may increase positive outcomes.
Prevention is key. IBD can be carried to a clean flock through dirty equipment or forgetting to isolate new birds. It’s best to keep different broods of chicks separated by a hatch or where they came from to prevent total losses if one group comes up positive for IBD. IBD is found in wild birds as well. The risk of transmission is low, but when feasible, it is always safer to keep chicks indoors in a barn, shed, or garage away from wildlife.
The best protection from this disease is to vaccinate the parent flock and then vaccinate the chicks before they turn three weeks old. Maternal immunity will protect them until they can be vaccinated. Vaccinating before three weeks helps ensure that there are no lapses in coverage. As is the case with any virus, this can help prevent the disease or make it less fatal if it is contracted.
IBD is a horizontal disease, meaning that while it is super contagious between brood mates, the survivors will not pass the disease onto their offspring. There isn’t any evidence of birds carrying the virus either, once it has run its course. The biggest post-illness issue is the dampened immunity that allows for increased sicknesses.
This virus has an abnormally long lifespan and can live on surfaces for months after being released from the host bird. Additionally, the virus isn’t easily eradicated with disinfectants, so the safest bet is to consider any bedding, coop, and equipment contaminated for several months after an outbreak. For the remaining birds, being mindful of their immunocompromised status and having excellent biosecurity will enable them to live a normal life.
Originally published in the December 2021/January 2022 issue of Backyard Poultry and regularly vetted for accuracy.