DEVELOPMENT AND VERIFICATION OF A NOVEL FOAM VACCINATION SYSTEM FOR CHICKS
The poultry industry is a multi-billion dollar industry that relies on many vaccine application techniques to provide efficient and efficacious protection to its flocks from a pantheon of viral diseases. Spray vaccination has been the most widely used form of mass vaccination for over 40 years. Despite its widespread use, spray application suffers from its susceptibility to certain environmental effects and application issues that make application ununiform and unprotective. We designed, developed, and validated a mass application system that used edible foam as the vaccine vehicle. A foam dispensing nozzle was created and is able to consistently create uniform foam from a Versawhip/xanthan gum based foaming agent. The quality of foam is consistent with the average expansion rate ranging from 25.69 - 33.58, the average bubble size ranging from 3.05 - 3.52 mm, the average liquid drainage at 10 minutes ranging from 59% - 91%, and an average deterioration rate at 5 minutes ranging from 97.3% - 98.2%. After successfully designing the nozzle and foam that was uniform over multiple applications, continued improvements to the system were made through continued testing of nozzle configurations and foaming agent. The system and foaming agents impact on vaccine efficacy was then assessed. The first apparatus was used for two treatments that resulted in a 1.2 log and 1 log loss in titer when using egg white foams compared to the deionized H2O controls (103.8 EID50 per ml and 104.0 EID50 per ml compared to 10>5 EID50 per ml). The second apparatus caused no significant loss of titer when using egg white foam. The third apparatus caused no significant losses of titer when using either egg white or Versawhip based foams. The Versawhip stability trial showed a mild reduction of titer at 60 minutes (104.15 EID50 per ml compared to control titer of 105.33 EID50 per ml) but did not show significant losses of titer at 30-minute (104.93 EID50 per ml) or 120-minute time points (104.54 EID50 per ml). Once it was determined that the foaming system and agent were safe for the vaccine, a 5-nozzle system was built, and was assessed for its ability to apply foam uniformly across chicks. This uniformity of application was compared to coarse spray vaccination. The data depicted that foam was able to reach the eyes, down, and choanal cleft more uniformly than spray. Additionally, it was also found that foam was ingested at higher levels compared to spray with an average of 7.4 μL of foam being ingested per chick compared to only 3.4 μL of spray being ingested per chick. This shows that foam application was able to more uniformly target the areas needed to successfully vaccinate chicks against diseases such as infectious bronchitis. This led to the final experiment in which the foam vaccination system was compared to coarse spray and eyedrop vaccination on accounts of uniformity and protection. RT-PCR showed that eyedrop vaccination and 2-pass foam application had 100% coverage, 1-pass foam had 92.3% coverage, and spray had 72% coverage. ELISA testing showed that there were no significant differences in the antibody titers between any of the vaccinated groups. Of the vaccinated groups, the foam 2-pass group had the highest antibody titers while spray group had the lowest. Tracheal swabs and histological evaluation also support foam vaccination as a better alternative to spray vaccination. The results of the project support the idea that foam vaccination can apply IBV vaccine uniformly to chickens and provide protection similar to that of coarse spray vaccination.