In ovo vaccination assists earlier, more robust immune response in chicks
At hatch, chicks can be exposed to health challenges, such as Marek’s disease virus (MDV), Newcastle disease (ND) and infectious bursal disease (IBD), and their immune systems may be too underdeveloped to protect against infection. It can take one to two weeks for the newly hatched chick’s immune system to fully mature, creating a period of vulnerability. However, there are ways to help protect chicks sooner.
Recombinant vaccines based on herpesvirus of turkeys (HVT) applied accurately through in ovo vaccination help hasten maturation of the chicken embryo immune system, shifting the onset of immunity closer to hatch3 and allowing the chick to respond to a disease challenge sooner.1,2,4 Accurate site of injection during in ovo vaccination, in the amnion, is important to help maximise the full potential of vaccine investments and support an immune response.
In a study, chickens vaccinated against MDV at day 17 of incubation had a lower incidence of lesions when challenged with MDV during the first 5 days after hatch compared with birds vaccinated at hatch, demonstrating that chicks vaccinated in ovo initiated a prehatch immune response (Figure 1).4
Figure 1- An MDV challenge study compared chicks vaccinated in ovo at day 17 of incubation with chicks vaccinated subcutaneously at hatch against MDV.
Apply recombinant vaccines in ovo to get more from early immunity
Recombinant vaccines – such as poulvac procerta – that are based on HVT, are commonly used with in ovo vaccination systems. The HVT virus – related to MDV and conferring protection against MDV — is a large virus, and that helps make it a good candidate for gene inserts from other viruses (particularly ND virus, IBD virus and infectious laryngotracheitis).
In ovo vaccination not only helps with adaptive immunity through development of antibodies (humoral immunity) but also helps chickens develop cell-mediated immunity — an immune response that helps fight pathogens by destroying infected cells that display certain proteins known as antigens on their surface.
Research has demonstrated that in ovo vaccination with HVT also can hasten maturity of the chick embryo immune system. In ovo administration of HVT at day 18 of incubation resulted in innate and cell-mediated immunity responses comparable to those of chicks 1 to 2 weeks of age.2
Earlier development of the immune system via in ovo vaccination helps protect young birds against pathogens unrelated to those they’ve been vaccinated against. In a study, a group of chicks were given an HVT in ovo vaccination. A 2nd group received a sham or diluent-only in ovo vaccination. All the in ovo-vaccinated chicks were exposed to KLH, an unrelated antigen. Unvaccinated 7- and 14-day-old chicks were also exposed to KLH. When KLH antibodies were evaluated a week after exposure, 100% of the HVT in ovo-vaccinated chicks developed detectable antibodies to KLH, as well as 100% of the unvaccinated 7- and 14-day-old chicks. Only 20% of the sham in ovo-vaccinated chicks developed detectable KLH antibodies.2
When all the chicks were exposed to KLH a 2nd time, the antibody activity level for the HVT in ovo-vaccinated chicks was much higher compared with the sham in ovo-vaccinated group. Comparing the HVT in ovo-vaccinated chicks to the unvaccinated 7- and 14-day-old chicks after the second exposure to KLH, the HVT in ovo-vaccinated chicks had 61% of the KLH antibody activity compared with the 7-day-old chicks (46.7% compared with 76.4%). This shows in ovo vaccination helps enhance maturation of the chicken immune system. Previously, it was thought that chicks do not develop humoral immune response until 1 to 2 weeks of age.2
Recombinant vaccines pair well with embrex in ovo devices
The pairing of the accurate and reliable embrex in ovo vaccination systems with vector vaccines can enable great value and optimal results from a hatchery vaccine programme. The fast-acting line of poulvac procerta vector vaccines from Zoetis are designed to help provide early, fast protection against costly viral challenges and compare favourably with competitor vector vaccines.6-12
Technology built for success, backed by experience
Embrex in ovo vaccination technology delivers on 5 critical success factors for in ovo vaccination that support efficacious vaccine response and help reap the benefits of vaccine investments. Those 5 in ovo technology success factors include (1) adaptive egg location; (2) consistent shell penetration; (3) thorough sanitation; (4) accurate site of injection; and (5) vaccine integrity maintenance.
This technology is backed by more than 30 years of combined poultry health and engineering experience, working with poultry producers to effectively immunise chickens and address disease challenges. Zoetis is committed to delivering on the excellence in service, training, support and in ovo technology that the embrex brand is consistently known for around the world.13
References are available on request.
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