Evaluation of the safety and efficacy of the novel Mycoplasma gallisepticum vaccine, Vaxsafe MG304, after spray-vaccination of 1-day-old specific pathogen-free chicks.

Mycoplasma gallisepticum causes chronic respiratory disease in poultry. A novel vaccine, Vaxsafe MG304 (the ts-304 strain), has greater protective efficacy in chickens than the Vaxsafe MG (strain ts-11) vaccine when delivered by eye drop at 3 weeks of age. Applying this vaccine in the hatchery to 1-day-old birds, using mass administration methods, would improve animal welfare and reduce labour costs associated with handling individual birds. This study assessed the protection provided by vaccination with Vaxsafe MG304 after administration to 1-day-old chicks. Chicks were administered a single dose of the vaccine to assess the efficacy of either a high dose (107.0 colour changing units, CCU) or a low dose (105.7 CCU) after eye drop or spray (in water or gel) administration against experimental challenge with virulent M. gallisepticum strain Ap3AS at 7 weeks of age. The vaccine was able to colonise the palatine cleft of chicks after vaccination by eye drop (at both doses) or by spray (in water or gel) (at the high dose). The high dose of vaccine, when delivered by eye drop or spray, was shown to be safe and induced a serological response and protective immunity (as measured by tracheal mucosal thickness and air sac lesion scores) against challenge. Vaccination of 1-day-old chicks with Vaxsafe MG304 by eye drop induced protective immunity equivalent to vaccination at 3 weeks of age. Vaxsafe MG304 was also protective when applied by both coarse- and gel spray methods at the higher dose and is therefore a suitable live attenuated vaccine for use in 1-day-old chicks.

Nebulization as a more efficient method than atomizer for experimental reproduction of avian colibacillosis in young chickens.

Infection and immunity studies involving genetically modified organisms (GMOs), such as gene knockout bacterial mutants, require stringent physical containment to prevent the accidental spread of these organisms into the environment. Experimental respiratory tract infection models often require the animals, for example birds, to be transported several times between a negative pressure housing isolator and a bespoke aerosol exposure chamber under positive pressure. While the exposure chamber is sealed and fitted with HEPA filters, the repeated movements of infected animals and opening of the chamber can still pose a serious risk of breaching containment of the organism in the experimental facility. In the current study, the ability of two aerosol infection protocols that expose birds to avian pathogenic E. coli (APEC) aerosols directly within the housing isolator was evaluated. Young chicks were exposed to APEC E956 within the negative pressure housing isolators using either a nebulizer or an atomizer. Birds exposed twice (days 1 and 4) to aerosols of APEC E956 produced by the nebulizer developed a rapidly progressing disease mimicking field cases of avian colibacillosis. However, birds exposed to aerosols of APEC E956 produced by an atomizer did not develop colibacillosis even after three exposures to APEC E956 on days 1, 4 and 7. Consequently, the current study reports the nebulizer was more efficacious in producing avian colibacillosis under stricter bacterial containment settings.RESEARCH HIGHLIGHTS Two aerosol exposure methods were evaluated to develop avian colibacillosis.Nebulizer method found to be more efficient in reproducing avian colibacillosis.Refined infection method can be used to study genetically modified organisms (GMOs).