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Pathogenicity differences of multiple isolates of Aspergillus fumigatus in turkeys
1U.S. Department of Agriculture, National Animal Disease Center, Ames, Iowa 50010.
Abstract:
Sixteen Aspergillus fumigatus isolates of environmental, mammalian, and avian origin were used to assess: 1) intra-air-sac inoculation as a viable challenge alternative to aerosol exposure, and 2) isolate variability in pathogenicity. Development of lesions, antibody response in survivors, mortality, and weight gains were assessed. Turkey poults were challenged with equal numbers of viable conidia. Total number of conidia given per experimental group varied markedly and did not influence mortality. Antibody response as measured by the enzyme-linked immunosorbent assay and agar gel immunodiffusion test was erratic, although most poults with high antibody scores had marked lesions and low weight. Lesions were characterized by necrogranulomatous pneumonia and airsacculitis with marked visceral involvement. The source of the isolate was not a factor in mortality, although this was biased by the high numbers of isolates from birds with aspergillosis. The single environmental isolate produced no mortality.
Insights
Intra-air-sac inoculation effectively challenges turkey poults with Aspergillus fumigatus, revealing isolate variability in pathogenicity. Lesion development and antibody response varied, but isolate origin did not significantly impact mortality.
Area of Science:
- Veterinary Mycology
- Avian Pathology
Background:
- Aspergillosis is a significant respiratory disease in poultry.
- Traditional aerosol exposure methods for challenging birds can be difficult to standardize.
- Understanding Aspergillus fumigatus isolate pathogenicity is crucial for disease control.
Purpose of the Study:
- To evaluate intra-air-sac inoculation as an alternative to aerosol exposure for challenging turkey poults with Aspergillus fumigatus.
- To assess the variability in pathogenicity among different Aspergillus fumigatus isolates from various sources.
- To correlate lesion development, antibody response, mortality, and weight gain with isolate characteristics.
Main Methods:
- Sixteen Aspergillus fumigatus isolates (environmental, mammalian, avian) were used.
- Turkey poults were challenged via intra-air-sac inoculation with equal numbers of viable conidia.
- Mortality, weight gain, lesion development (necrogranulomatous pneumonia, airsacculitis), and antibody response (ELISA, AGID) were assessed.
Main Results:
- Intra-air-sac inoculation was a viable challenge method.
- Conidial load did not influence mortality.
- Antibody response was erratic; high antibody scores correlated with lesions and low weight.
- Lesions were severe, involving lungs and air sacs with visceral spread.
- Isolate origin did not affect mortality, though avian isolates were overrepresented.
Conclusions:
- Intra-air-sac inoculation is a practical alternative for challenging poultry with Aspergillus fumigatus.
- Significant variability exists in the pathogenicity of Aspergillus fumigatus isolates.
- Disease severity and host response are complex and not solely dependent on isolate origin or inoculum concentration.