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Comparison of Experimental Infection of Normal and Immunosuppressed Chickens with Mycoplasma gallisepticum
Abstract:
Four different models of infection of chickens with Mycoplasma gallisepticum (MG) were evaluated. Normal or immunosuppressed chicks (10 days old) were infected with the MG Rlow strain via eye and nasal drops or by direct air sac injection. Bacterial load in the lungs was quantified and air sac and tracheal lesion scores, tracheal mucosal thickness and humoral immune responses were assessed. Serum antibody responses were assessed by use of a serum plate agglutination test. Three days post infection (dpi), all immunosuppressed chicks had developed significant respiratory signs. Chicks infected via air sac injection had significant differences in serum antibody and gross lesion scores at 5 dpi. All chicks had developed pathological changes by 7 dpi. Air sac inoculation of immunosuppressed chicks produced more significant (P ≤0.05) lesions, and these birds had the highest bacterial load in the lungs compared with other groups.
Insights
Immunosuppressed chicks infected with Mycoplasma gallisepticum (MG) via air sac inoculation showed the most severe respiratory lesions and highest bacterial load. This highlights a critical model for studying MG infection in poultry.
Area of Science:
- Veterinary Microbiology
- Poultry Pathology
- Infectious Diseases
Background:
- Mycoplasma gallisepticum (MG) is a significant avian pathogen causing respiratory disease in chickens.
- Understanding optimal infection models is crucial for research and vaccine development.
Purpose of the Study:
- To evaluate four distinct infection models for Mycoplasma gallisepticum (MG) in chickens.
- To compare the severity of respiratory disease and immune response across different inoculation methods and host immune status.
Main Methods:
- Infection of normal and immunosuppressed chicks with MG Rlow strain via eye/nasal drops or air sac injection.
- Quantification of bacterial load, assessment of lesion scores, tracheal mucosal thickness, and humoral immune responses (serum plate agglutination test).
Main Results:
- Immunosuppressed chicks exhibited significant respiratory signs by 3 days post-infection (dpi).
- Air sac injection led to notable differences in serum antibodies and lesion scores by 5 dpi.
- Air sac inoculation in immunosuppressed chicks resulted in significantly more severe lesions (P ≤ 0.05) and the highest lung bacterial load by 7 dpi.
Conclusions:
- Air sac inoculation is an effective method for inducing severe Mycoplasma gallisepticum (MG) infection in immunosuppressed chickens.
- This model provides a robust system for investigating MG pathogenesis and evaluating therapeutic interventions in poultry.
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