Pathogenicity of FAdV-D serotype 2 in broiler and layer chicks

Area of Science:

• Avian Pathology
• Virology
• Immunology

Background:

• Inclusion body hepatitis (IBH) in chickens is primarily caused by fowl adenovirus (FAdV).
• Understanding the pathogenesis and immune effects of specific FAdV serotypes is crucial for disease control.

Purpose of the Study:

• To investigate the effects of FAdV-D serotype 2 isolates on broiler and layer chickens.
• To assess clinical signs, histopathological changes, viral shedding, and immune responses following experimental infection.

Main Methods:

• Experimental infection of broiler and layer chicks with two FAdV-D serotype 2 isolates.
• Clinical observation, histopathology, viral shedding analysis (up to 21 days post-infection).
• Serological response (ELISA), biochemical analysis, innate immune parameters (PCR for interleukins/cytokines), and vaccine response (HI test) were evaluated.

Main Results:

• No mortality was observed, but significant histopathological damage occurred in multiple organs (liver, pancreas, kidneys, spleen, thymus, bursa of Fabricius).
• Viral shedding persisted up to 21 days post-infection.
• FAdV-D serotype 2 infection elevated interleukins and cytokines but did not induce a serological response or affect vaccine immunity; broilers were more susceptible than layers.

Conclusions:

• FAdV-D serotype 2 causes significant immunosuppression in chickens.
• Broiler chickens exhibit higher susceptibility to IBH caused by FAdV-D serotype 2 compared to layer chicks.
• Despite lack of mortality, FAdV-D serotype 2 infection induces subclinical pathology and immune modulation.