IBD surveillance programs help set up successful vaccination programs
Through IBD surveillance programs, producers can understand which IBD types are present and develop effective vaccination programs to their operation.
By Kalen Cookson, DVM, MAM, DACPV, director of clinical research, Zoetis
Infectious bursal disease (IBD) is one of the most prevalent disease challenges in broiler chicken production. By conducting surveillance, producers can understand which IBD types are present in their flocks and when the virus is likely to infect birds, and then develop an effective IBD vaccination program specific to the operation.
Bursal surveillance lets the bird tell us “how we’re doing.” It tells us when the field viruses are challenging birds and what those viruses look like. It also shows us what kind of cushioning our two IBD vaccination programs (passive and active) are providing.
IBD basics
Infectious bursal disease virus (IBDV) infects young chickens and can cause permanent immune suppression in birds 3 weeks of age or younger,1 which can lead to secondary infections such as Escherichia coli.2,3 These secondary pathogens are more likely to cause further health challenges and performance losses due to the IBD-weakened immune system.
Because IBDV has a high mutation rate, there is a wide range of antigenic variation of the virus in the field, both over time and across locations (Figure 1).1 AL2 is the predominant variant type in the U.S., recovered from nearly half of all sampled flocks during the 2009-2014 period, although Group-6 type viruses have increased in prevalence more recently.1
Figure 1. Percent Prevalence of IBDV Types Over Time
With multiple types of IBDV, it is important to choose a vaccine that provides protection against the predominant variants. The best way to know which viral challenges a flock is facing is to participate in a bursal surveillance program.
Vaccine strategies buffer chicks during critical times
Breeding chickens are vaccinated against IBDV, providing newly hatched chicks with maternal antibodies, which help protect their chicks during the first two to three weeks of life (the first “pillow of protection” shown in Figure 2).
Chicks also can be vaccinated — usually in the hatchery either in ovo or subcutaneously at day of hatch — to set up the chick’s immune system to provide active immunity (the second pillow of protection).
As maternal antibodies start to wane around 14 days of age, vaccinations administered in the hatchery can help transition chicks to active immunity, ensuring there are no gaps in coverage, especially when chickens are raised in high-challenge environments.4
Figure 2. Only Strong Breeder and Progeny Programs Can Cushion Against Early and Late IBDV Challenges
Establishing and conducting IBD surveillance
Routinely assessing bursal health in young chickens is an important step in countering active IBDV challenges and developing appropriate vaccination programs for broiler chickens.
Surveillance could be conducted proactively to determine which virus types are present at which ages in a complex to gauge immune suppression potential and develop an IBD vaccination program. Surveillance also may be conducted to document a vaccine’s cushioning or “Pillow 2” effect in vaccinated birds.
Zoetis conducts surveillance programs in-house, allowing summary reports to offer more granularity about PCR sequencing results so customers can see exactly which virus types they are dealing with, how the virus load may be changing over time and how vaccination programs can be fine-tuned to align with specific field challenges.
When samples are shipped to the diagnostic laboratory, additional information such as vaccine and clinical history are important to include as they provide relevant information needed to develop subsequent recommendations.
Zoetis recommends sampling chickens when they are 18-32 days of age to best determine the window of field challenge and sequence virus types. Birds are not usually sampled before 17-18 days because percent yield of active infections/damage usually goes way down and infections can still be estimated by 2 weeks of age based on the 18- to 22-day results.
At collection, bursas also should be measured and scored with a bursameter. This gives valuable information regarding the window of infection and the level of cushioning provided by vaccination.
Interpreting IBDV surveillance results
When the laboratory completes its testing, customers/clients receive a report* summarizing results for bursameter scores, PCR results and genetic analysis of detected viruses (if sequenced; see examples).
With these results, users can determine which IBD types are present in a flock and when birds are becoming infected, so vaccination programs can be developed to target those challenges.
Contact your Zoetis representative to discuss current IBD challenges and enroll in an annual IBD surveillance program.
*Zoetis may provide a summary or report for informational purposes only. Such information is not intended to be a specific recommendation or advice. At all times, customer agrees to consult with its own veterinarian of choice.References
1 Anderson T, Barker A, Strickland J, Cookson K, Da Costa M, Schaeffer J. An update of wild type IBDV from diagnostic bursal surveys of broiler flocks in the United States since 2009, in Proceedings. International Poultry Science Forum, Atlanta, Georgia. 2023.
2 Cookson K, Macklin K, Giambrone J, Toro H. The influence of E. coli inoculum titer and virally induced immune suppression on the incidence of cellulitis in a broiler skin challenge model, in Proceedings. Western Poultry Disease Conference. 2007.
3 Dey S, Pathak DC, Ramamurthy N, Maity HK, Cellappa MM. Infectious bursal disease virus in chickens: prevalence, impact, and management strategies. Vet Med 2019;(10):85-97.
4 Cookson K, Da Costa M, Dickson J, Schaeffer J. Broiler protection and performance trials of the newest HVT-IBD recombinant vaccine against AL2 and Group-6 IBDV challenges, in Proceedings. AAAP Meeting. 2022.
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