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Published on: February 20, 2015
Evaluation of Mycoplasma gallisepticum K-strain as a live vaccine in chickens
N M Ferguson-Noel1, V A Laibinis, S H Kleven
1Department of Population Health, University of Georgia, Athens, GA 30602-4875, USA. naolaf@uga.edu
Abstract:
We evaluated the pathogenicity of three live Mycoplasma gallisepticum (MG) vaccine candidates by infection via aerosol of 3-wk-old chickens with log phase broth cultures (trial 1). Two of the candidates (K3020 and K4649A) colonized only 10% and 20% of the chickens, respectively, unlike K2101 (K-strain), which was reisolated from all of the vaccinated chickens tested. K-strain inoculation did not result in significant air sac or tracheal lesions in chickens at 10 and 39 days postinfection (P < or = 0.05). The efficacy of K-strain as a live vaccine was evaluated in trial 2, by challenge of vaccinated chickens with virulent R-strain via aerosol at 6 wk postvaccination. K-strain vaccination resulted in significant protection from air sac and tracheal lesions (P < or = 0.05). The K-strain was further investigated to evaluate transmissibility (trial 3), colonization and persistence of infection following aerosol administration (trial 4), genetic and phenotypic stability following back passage through chickens (trial 5), and vertical transmission (trial 6). The K-strain had a low rate of horizontal transmission; it remained primarily in the respiratory system of inoculated birds and persisted in the upper respiratory tract for the duration of the trial 4 (5 mo). There was no increase in virulence of K-strain when it was back passaged five times through chickens, and no vertical transmission of K-strain was detected. K-strain showed great potential as a safe and effective live MG vaccine.
Insights
The K-strain Mycoplasma gallisepticum (MG) vaccine candidate demonstrated safety and efficacy in chickens. It provided significant protection against virulent R-strain challenge without increasing virulence or causing vertical transmission.
Area of Science:
- Veterinary Microbiology
- Avian Health
- Vaccine Development
Background:
- Mycoplasma gallisepticum (MG) is a significant pathogen in poultry.
- Live vaccines are crucial for controlling MG infections.
- Evaluating novel MG vaccine candidates for safety and efficacy is essential.
Purpose of the Study:
- To assess the pathogenicity and efficacy of three live Mycoplasma gallisepticum (MG) vaccine candidates.
- To investigate the safety, transmissibility, and stability of the most promising candidate, K-strain.
Main Methods:
- Three live MG vaccine candidates were administered via aerosol to 3-week-old chickens.
- Pathogenicity was assessed by reisolation and lesion scoring.
- Efficacy was evaluated by challenging vaccinated chickens with virulent R-strain.
- Further studies included transmissibility, colonization, persistence, genetic stability, and vertical transmission assessments.
Main Results:
- K-strain (K2101) colonized all vaccinated chickens without causing significant lesions.
- K-strain vaccination provided significant protection against air sac and tracheal lesions following challenge.
- K-strain exhibited low horizontal transmission, persisted in the respiratory tract for 5 months, and showed no increased virulence after back-passage.
- No vertical transmission of K-strain was detected.
Conclusions:
- K-strain is a safe and effective live Mycoplasma gallisepticum vaccine candidate.
- It demonstrates potential for controlling MG infections in poultry.
- Further development of K-strain as a commercial vaccine is warranted.
