Introduction
Inclusion Body Hepatitis (IBH) is an economically important viral disease of broiler chickens characterized by sudden mortality, hepatitis, and the presence of intranuclear inclusion bodies in liver cells. The disease is primarily caused by Fowl Adenoviruses (FAdVs), particularly serotypes belonging to species D and E. IBH has become increasingly significant worldwide due to its impact on broiler performance, increased mortality, poor feed conversion, and substantial economic losses. The disease mainly affects young broiler chickens between 3 and 7 weeks of age, although birds of other ages may also be affected. Vertical transmission from breeder flocks and horizontal spread through contaminated litter, water, equipment, and personnel play major roles in disease dissemination.

Etiology
IBH is caused by Fowl Adenoviruses (FAdVs), non-enveloped double-stranded DNA viruses belonging to the genus Aviadenovirus within the family Adenoviridae. Several serotypes have been associated with disease outbreaks, including FAdV-2, FAdV-8a, FAdV-8b, and FAdV-11.
Predisposing factors include:
– Immunosuppression caused by Infectious Bursal Disease (IBD)
– Chicken Infectious Anemia (CIA)
– Mycotoxicosis (Poor quality of feed ingredients contaminated with fungus and Mycotoxins).
– Poor Biosecurity and Management
– High stocking density

Clinical Signs
Affected broiler flocks may exhibit:
– Sudden increase in mortality
– Depression and lethargy
– Huddling with Ruffled feathers
– Reduced feed and water consumption
– Usually affects birds of 3 to 5 weeks age, but can be seen in the chicks aging from 4-5 day old.
– Pale comb and wattles
– Poor weight gain
– Diarrhoea with mucoid droppings or green droppings
– Anemia in severe cases
Mortality rates generally range from 5–15%, but outbreaks may occasionally result in mortality exceeding 30%.

Post-Mortem Lesions
The most characteristic lesions are observed in the liver.
Gross Lesions
Liver
– Enlarged, swollen, and pale liver
– Yellowish discoloration
– Multifocal necrotic foci
– Petechial and ecchymotic hemorrhages
– Friable consistency
Kidneys
– Enlarged and pale kidneys
– Congestion
Heart
– Hydropericardium may occasionally be present
– Pale myocardium
Spleen
– Enlargement and congestion
Histopathological Lesions
Microscopic examination reveals:
– Severe hepatic necrosis
– Basophilic intranuclear inclusion bodies in hepatocytes
– Degeneration and destruction of liver cells
– Mononuclear cell infiltration
The presence of characteristic intranuclear inclusion bodies is considered pathognomonic for IBH.

Serology
Serological testing is useful for monitoring flock exposure and breeder immunity.
Common serological methods include:
ELISA (Enzyme-Linked Immunosorbent Assay)
– Detects antibodies against Fowl Adenovirus
– Useful for flock monitoring
– Evaluates maternal antibody levels
Virus Neutralization Test (VNT)
– Determines serotype-specific antibodies
– Primarily used in research and epidemiological investigations
Interpretation
– High antibody titers in breeders provide maternal protection to progeny.
– Seroconversion in broilers indicates field exposure.
– Paired serum samples can help determine recent infection.
Diagnosis
Diagnosis should be based on a combination of clinical history, post-mortem findings, histopathology, and laboratory confirmation.
Field Diagnosis
Suspect IBH when:
– Sudden mortality occurs in 3–7 week-old broilers.
– Enlarged, pale, hemorrhagic liver is observed.
– There is a history of immunosuppressive diseases.
Laboratory Diagnosis
Histopathology
– Demonstration of intranuclear inclusion bodies in hepatocytes.
Polymerase Chain Reaction (PCR)
– Highly sensitive and specific.
– Detects and identifies FAdV serotypes.
Virus Isolation
– Performed in chicken embryo liver cells or embryonated eggs.
Immunohistochemistry
– Detects adenoviral antigen within tissues.
Sequencing
– Used for epidemiological studies and strain characterization.

Treatment
There is no specific antiviral treatment for Inclusion Body Hepatitis.

Management is mainly supportive:
Supportive Therapy
– Multivitamin supplementation
– Vitamin E and Selenium administration
– Use D’Bio-Mix 20-25 mL per 100 birds and ABES-URZZA 20 ml for 100 birds.
– Ionic electrolyte (ABESTRAL) supplementation and probiotic prebiotic supplementation
— Adequate hydration
Control of Secondary Infections
– Antibiotics may be administered under veterinary supervision to control secondary bacterial infections.
Management Measures
– Reduce stress factors
– Improve ventilation
– Maintain litter quality
– Ensure proper nutrition

Prevention and Control
Effective prevention relies on biosecurity and breeder vaccination.

Biosecurity Measures
– All-in/all-out management
– Thorough cleaning and disinfection
– Restriction of farm visitors
– Proper disposal of dead birds
– Control of rodents and insects
– Sanitation of equipment and vehicles
Breeder Flock Management
– Monitor antibody levels regularly.
– Vaccinate breeders to ensure maternal antibody transfer.
– Prevent immunosuppressive diseases such as IBD and CIA.
Control of Vertical Transmission
– Maintain healthy breeder flocks.
– Conduct routine serological surveillance.
– Implement strict hatchery hygiene.

Vaccination Schedule
Vaccination strategies vary according to local epidemiology and circulating serotypes.
Breeder Vaccination Program
Age Vaccine
8–10 weeks Killed IBH (primary dose)
14–16 weeks Booster dose
18–20 weeks (before lay) Optional booster in high-risk areas
Broiler Vaccination
Routine vaccination of broilers is generally not practiced in many regions because protection is primarily achieved through maternal antibodies. However, live or inactivated vaccines may be considered in endemic areas under veterinary guidance.
Objectives of Vaccination
– Prevent vertical transmission
– Enhance maternal antibody levels
– Reduce mortality and production losses
– Improve flock uniformity

Economic Impact
IBH can result in:
– Increased mortality
– Poor growth performance
– Reduced feed efficiency
– Higher medication costs
– Increased carcass condemnation
– Significant financial losses to poultry producers

Conclusion
Inclusion Body Hepatitis remains an important viral disease of modern broiler production. Early diagnosis, strict biosecurity, breeder vaccination, and effective management practices are essential for disease prevention and control. Maintaining strong maternal immunity through breeder vaccination and minimizing immunosuppressive conditions can significantly reduce the impact of IBH on commercial poultry operations.