Inclusion Body Hepatitis (IBH) can be frustrating and difficult to predict. It’s important for the industry to work together at all levels and encourage open communication to most effectively manage its impacts.
What is IBH?
Inclusion Body Hepatitis (IBH) is a viral disease that affects chickens and is most frequently seen in broilers. It is very prevalent throughout North America and beyond.
The most common clinical sign of IBH is increased mortality in the flock. Often the trend shows an increase in mortality for 3-4 days, a plateau for 3-4 days, then a decrease in mortality over 3-4 days. The total mortality associated with IBH can vary widely, ranging from undetectable levels to up to 40% of the flock.
Mortality from IBH is most often seen in birds around three to four weeks of age, however the timing of infection may vary.
The disease is caused by Fowl Adenovirus, which can be classified into different groups, species, and subgroups called serotypes. The most common serotypes causing IBH in Canada are 11, 8a, and 8b.
The virus that causes IBH can be transmitted “vertically” (from a hen to her offspring through the egg) and “horizontally” (between birds through feces). This means that if some chicks are infected via the egg, they may carry the virus into a flock and spread it to their flock-mates. It also means that if the virus gets into a broiler barn from dirty equipment, shoes, insects, manure, etc. or if the virus is already in the barn from a previous cycle, chicks can be infected that way too. Unfortunately, since adult broiler breeders generally do not show illness from IBH, there is no reliable way to tell if broiler breeders are infected or shedding the virus to their offspring.
Diagnosis
The first step in diagnosing IBH is a postmortem examination of dead birds. In a bird infected with IBH, the liver typically appears enlarged with yellow discolouration and red spots (small pinpoint areas of bleeding). The skin or fat of the bird may appear more yellow than normal as well. Sometimes the kidneys may be swollen or the heart may be surrounded by fluid (hydropericardium).
While postmortem findings can be suggestive of IBH, the diagnosis can only be confirmed with further testing such as microscopic examination (histopathology) and PCR (polymerase chain reaction) testing. It is important to consult a poultry veterinarian and consider submitting samples for confirmation because many different disease processes can cause abnormalities in the liver that may be mistaken for IBH.
Sample submission is also important because it allows for genotyping of the virus if the diagnosis is confirmed. Genotyping will identify which serotype (11, 8b, etc.) is present in the birds. Knowing the serotype is critical for monitoring broiler breeder vaccination programs (more on this below).
Prevention and Control
There are many different strategies that can be used to manage the risk of IBH.
- Broiler Breeder Vaccination
Vaccination of broiler breeders is the primary method we have to protect birds against disease caused by the IBH virus. Typically, breeders are given two injections of this vaccine prior to the start of egg production. There are no vaccines currently licensed for use in broiler chickens in Canada.
Not only does vaccination protect the breeders from infection, the antibodies the birds make in response to vaccination are also passed down from the hens to their chicks via the egg yolk. These “maternal antibodies” help to protect broiler chicks for the first two to three weeks of their life.
Unfortunately, the different serotypes of the virus that causes IBH do not result in protection against other serotypes. For example, if a bird is vaccinated for only type 8b, it will not have protection against type 11. Veterinarians typically use autogenous or “custom” vaccines which can incorporate the specific serotypes and strains that are present in the field within a geographic area or a specific system. As mentioned previously, it’s important to always know what strains are present in the field in order to make sure that the vaccines are effective and up to date.
- Optimal Barn Management and Stress Mitigation
Good stockmanship can help ensure that birds are healthy and able to fight off infections such as IBH. Stress causes suppression of the immune system so any stressor can increase susceptibility to IBH. Examples of stressors may include chilling, overheating, feed outages, overcrowding, lighting issues, etc. Stress in the first week of life can also impair absorption of the yolk sac. This can result in the bird not absorbing enough maternal antibodies to protect them from disease.
- Prevention of Other Diseases
Immunosuppression can also be caused by other common diseases such as infectious bursal disease (IBD), infectious bronchitis virus (IBV), and reovirus. Monitoring for these viruses and implementing vaccination protocols if needed (as recommended by your veterinarian) will help to ensure the birds’ immune systems can cope with disease challenges such as IBH.
- Biosecurity
Maintaining optimal biosecurity is essential to keep IBH, and other diseases, out of the farm. It is strongly recommended to have dedicated clothing and footwear for each barn. Always clean and disinfect any equipment coming in and out of the barn. Have clear signage around the property to prevent accidental entry.
- Site Cleaning, Disinfection, and Pest Management
Fowl Adenovirus is an extremely hardy virus that can remain infectious in the environment for long periods of time. Thorough cleaning and disinfection of the barn after a cycle affected by IBH is critical to ensure the next flock is not re-infected. Some general tips that are often forgotten include:
- Clean and disinfect all areas of the farm that were accessed during the cycle. Make sure to include vehicles, equipment, hallways, offices, shops, clothes, footwear, waterlines, ventilation systems, etc. All organic material (e.g. manure) should ideally be removed from the site entirely. This will all help to reduce the load of virus particles on site and minimize the risk of re-infecting the next flock.
- After washing with water and detergent, allow the barn/surfaces to dry prior to applying your disinfectant to ensure that the disinfectant does not become diluted in any additional water.
- Not all disinfectants are effective against the virus that causes IBH, but some examples of ones that are known to be effective include Prevail, Virkon, Synergize, Bleach, and formaldehyde. Always be sure to follow label directions so that you are using the correct concentration and contact time to target viruses. Exercise caution with disinfectants, especially formaldehyde, as exposure can cause negative effects on human health.
- A heat treatment of the barn may be beneficial to further reduce the overall viral and bacterial load, especially for sites where cleaning and disinfecting is more difficult (e.g. dirt floors). The general rule of thumb is to heat the barn to 100°F (38°C) for 100 hours (~4 ¼ days).
- Pests such as darkling beetles and rodents are known to carry viruses, including IBH. Proper rotation of rodent control and insecticides are critical to control populations of these pests.
Treatment?
Since IBH is caused by a virus, there is no effective treatment for the disease itself. However, there may be ways that we can help support the birds and maximize their ability to survive the virus.
For example, some producers opt to treat birds with a multivitamin through the drinking water. Commercially available vitamin products often include B vitamins, which can anecdotally help to make the birds feel better during a disease challenge.
Vitamin D is also a common component of multivitamins and may be beneficial during an IBH challenge. The liver activates vitamin D into 25-hydroxyvitamin D (sometimes called Hy-D). When the liver is severely damaged, it may not be able to perform this function effectively. Therefore, liver failure from IBH (and other causes) can result in a vitamin D deficiency. Since vitamin D controls the absorption of calcium, a deficiency in vitamin D can cause a deficiency in calcium and resulting problems with bone development. Supplementing with Hy-D in the drinking water during outbreaks of IBH may help to mitigate these consequences by bypassing the liver activation step entirely.
The liver also has many important roles in metabolism. Recent research has shown that birds with IBH have lower blood pH (metabolic acidosis) and lower blood sugar (hypoglycemia) compared to normal birds. It’s possible that supplementation with sugar and/or sodium bicarbonate (baking soda) through the water may help to mitigate these negative effects, although this has not yet been proven. Always consult a poultry veterinarian and your processor before using any new products in the drinking water or feed to ensure that they are in accordance with any programs you are on (e.g. raised without antibiotics/RWA), and to ensure that they are being used correctly.
References/Further Reading
Boulianne M et al. (Eds.). 2019. Avian Disease Manual 8th Edition. The American Association of Avian Pathologists. ISBN: 9781646333936.
Fitzgerald SD, Rautenschlein S, Mahsoub HM, Pierson FW, Reed WM, and Jack SW. 2020. Adenovirus Infections. In: Diseases of Poultry 14th Edition (pp. 321–363). Swayne, D. E. et al. (Eds.). Wiley. https://doi.org/10.1002/9781119371199.ch9
Venne D, Chorfi Y. 2012. Blood biochemical changes in birds with inclusion body hepatitis and the effect of supportive treatments during outbreaks. In: Frame D (ed) Proc Sixty-First West Poult Dis Conf Scottsdale, Arizona, p 73–75
Dr. Hayley grew up in Calgary, Alberta and graduated from the University of Saskatchewan with a BSc. in Animal Bioscience. During her undergraduate studies, she was involved in swine and poultry research where she developed a keen interest in production animal health.
Following graduation from the Western College of Veterinary Medicine with her DVM degree, Dr. Hayley joined PLV where she practices both swine and poultry medicine. She has special interests in pathology, epidemiology, food safety, and animal welfare. She enjoys working with producers to help to their herds and flocks stay healthy, profitable, and sustainable.
