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Pathogenicity of Mycoplasma synoviae in broiler chickens
S B Lockaby1, F J Hoerr, L H Lauerman
1Department of Veterinary Pathobiology, Auburn University, AL 36849, USA. lockasm@vetmed.auburn.edu
Abstract:
Six isolates of Mycoplasma synoviae, identified as WVU 1853, K1968, K1858, 92D8034, F10-2AS, and FMT, were compared for pathogenicity in broiler chickens. Specific-pathogen-free chickens were inoculated, in two groups of 20, with each isolate by footpad or eyedrop inoculation at 1 day of age and were examined at necropsy 7, 14, 28, and 42 days postinoculation. Specimens were taken for histopathology, culture, polymerase chain reaction assay, and hemagglutination-inhibition serology. Isolates were grouped according to pathogenicity on the basis of differences in lesion development and tissue distribution in the respiratory system, other viscera, and the skeletal system. K1968 (pathogenic) induced lesions in all sites examined in both the footpad and eyedrop inoculation groups. It was detected in all sites following footpad inoculation and in all sites except viscera following eyedrop inoculation. WVU 1853, K1858, and 92D8034 (moderately pathogenic) induced lesions and were detected in all sites following footpad inoculation. With eyedrop inoculation, lesions were identified only in upper and lower respiratory sites, and organisms were detected only in upper respiratory sites. F10-2AS (moderately pathogenic) was similar; however, footpad inoculation failed to induce visceral lesions or permit organism detection in any site. F10-2AS was detected in upper and lower respiratory tissues following eyedrop inoculation. FMT (mildly pathogenic) induced only upper respiratory lesions when either footpad or eyedrop inoculation was used, and detection was restricted to upper respiratory sites following eyedrop inoculation. These results are useful in comparative evaluations of the virulence of other M. synoviae isolates and form a basis for characterization of virulence factors of M. synoviae.
Insights
Six Mycoplasma synoviae isolates were compared for pathogenicity in broiler chickens. Virulence varied, with K1968 being highly pathogenic and FMT mildly pathogenic, impacting different tissues based on inoculation route.
Area of Science:
- Avian pathology
- Microbiology
- Veterinary immunology
Background:
- Mycoplasma synoviae (M. synoviae) is an important avian pathogen causing respiratory disease and synovitis in poultry.
- Understanding the pathogenicity of different M. synoviae isolates is crucial for effective disease control and prevention strategies.
Purpose of the Study:
- To compare the pathogenicity of six distinct Mycoplasma synoviae isolates in broiler chickens.
- To evaluate the influence of inoculation route (footpad vs. eyedrop) on disease manifestation and organism distribution.
Main Methods:
- Six M. synoviae isolates were inoculated into specific-pathogen-free broiler chickens at one day of age via footpad or eyedrop.
- Chickens were examined at necropsy (7, 14, 28, 42 days post-inoculation) with samples collected for histopathology, culture, PCR, and serology.
- Isolates were categorized based on lesion development and tissue distribution in respiratory, visceral, and skeletal systems.
Main Results:
- Mycoplasma synoviae isolate K1968 demonstrated high pathogenicity, causing lesions in all examined sites regardless of inoculation route.
- Isolates WVU 1853, K1858, and 92D8034 were moderately pathogenic, affecting all sites with footpad inoculation but primarily respiratory sites with eyedrop inoculation.
- Isolate F10-2AS showed moderate pathogenicity, with footpad inoculation failing to induce visceral lesions, while FMT was mildly pathogenic, causing only upper respiratory lesions.
Conclusions:
- Pathogenicity of M. synoviae isolates varies significantly, influencing lesion development and tissue tropism.
- The route of inoculation plays a critical role in the distribution and severity of M. synoviae infections.
- These findings provide a basis for comparative virulence evaluations and characterization of M. synoviae virulence factors.