Animal models testing the ability of
vaccines and therapeutic agents to prevent pathology from induced respiratory
infection are an important means of testing and validating the
vaccines and therapeutic agents. However, the lack of induced pathology in test subjects could be either indicative of protection or a problem with the animal model system. This work describes the improvement of a chicken model system of intratracheal
infection using fluorescent
microspheres as a positive
indicator of
infection. It was shown that fluorescent
microspheres and Mycoplasma gallisepticum bacteria both dispersed to the same areas of the chicken respiratory system and that the
microspheres remained detectable in the chicken lung tissue for at least 7 days following
infection. The
microspheres used are detectable using a black light, allowing for visualization during necropsy. Using the updated model system, three live M. gallisepticum
vaccines were tested both for their ability to elicit a humoral immune response following vaccination, and for their ability to protect from air sac lesion pathology at two different time points following vaccination. Results showed the protective effects of the different M. gallisepticum
vaccines prevented the induction of pathology, consistent with previous results. The presence of the fluorescent
microspheres provided a positive method of identifying the properly infected chickens and a means of differentiating failed experimental
infections so that those samples could be removed, resulting in improved consistency in
infection results.