Improving respiratory vaccine applications
Improving respiratory vaccine application success
The poultry industry has an ongoing issue with successful vaccination in the hatchery. My research has led to new strategies and technology (equipment) to make the vaccination process more successful, thereby making our flocks healthier.
Nearly all commercial poultry in the United States are vaccinated against the economically significant disease, infectious bronchitis (IB). IB is caused by infectious bronchitis virus (IBV), a highly infectious upper respiratory tract pathogen. Because of the high volume of poultry produced in the U.S. (nearly 9 billion in 2015), chickens must be vaccinated in an efficient manner with mass application scalability. This has traditionally been accomplished by a spray cabinet used in the hatchery, wherein the IBV vaccines are sprayed onto the chicks as they move through the hatchery. This spray system is mechanically simple and easy to operate and is easily scalable for mass poultry production, but outbreaks of IB occur year after year in commercial poultry operations. To better understand why outbreaks of IB continue to occur in the face of heavy vaccination, we investigated the efficacy and efficiency of the spray application system in order to determine weaknesses or points of failure that could be affecting the proper administration of IBV vaccines.
We investigated IBV vaccine application by hatchery spray cabinet in several ways, including evaluating vaccine preparation prior to spraying, mixing IBV vaccines with other types of vaccines, and measuring the effect of the spray cabinet design and function on vaccine viability. Since IBV vaccines are live viruses, we hypothesized that temperature of the vaccine solution could be critical to ensuring that the vaccine was not destroyed or killed before or during application. Our temperature dependent, time course experiment showed that as long as the vaccine stays colder than 19 degrees C, the amount of live virus present does not change. When the vaccine reaches a temperature above 19C, the virus in the vaccine starts dying. This is significant as most hatcheries mix their vaccine with diluent or water stored at room temperature, which is higher than 19C in hatcheries. We also performed similar experiments where, instead of changing the temperature of the vaccine mixture, we mixed the IBV vaccine with coccidia vaccines to determine their effect on IBV. We found that, in a dilute mixture, there was no overall effect on IBV vaccines. In a concentrated mixture, which may occur during the mixing process, however, there was an effect on the IBV vaccine by some of the coccidia vaccines. This is also important information for hatchery managers as they implement vaccination programs and make decisions about vaccine mixtures for mass application.
The most significant findings of this line of research focused around the application process itself and what that does to a live IBV vaccine. There are several points in the application process that create differential pressures and forces on the vaccine, including the syringes that expel the vaccine and the nozzles that aerosolize it. We tested IBV vaccine viability at each of these locations and found that, surprisingly, the action of the syringes did not affect the IBV vaccine when smaller application volumes were used. The aerosolization from the nozzles was influenced however, causing a large part of the vaccine to not reach the chicks. The opposite was true when larger application volumes were used, whereby the syringes had much more impact on the vaccine than the nozzles. Since the impact by the syringes was actual virus destruction but the impact of the nozzles was related to droplet size formation and total volume reaching the chicks, we determined that the mechanism of the syringes was the most destructive part of the process.
From our research, we were able to show that the application process is not as efficient as we once thought, and that there are many areas where failure can occur and improvements can be made. Based on this research, we made many recommendations to the poultry industry on ways to improve their vaccination processes for IBV. Based on these recommendations, most hatcheries are now refrigerating their vaccine diluent before mixing to help prevent IBV vaccine destruction due to temperature. They are also applying IBV vaccines in larger volumes, since the larger application volumes were more efficient at delivering vaccine to the chicks. Hatcheries are also taking advantage of our vaccine combination research, and are mixing IBV and coccidia vaccines together to make the process more streamlined. All of these recommendations will improve the efficiency and efficacy of spray vaccination in the hatchery, but there are still points in the system that cannot be adjusted to reduce their effect on the overall system. For this reason, Dr. Mark Jackwood and myself designed a new spray application cabinet to remove the pieces of the system that were detrimental. This spray cabinet has been licensed by a major poultry vaccine company and has been placed in several hatcheries across the United States for field testing, with plans to release the system nationwide and possibly worldwide.
Health & Nutrition