Joe Giambrone, Teresa Dormitoro, Tom Brown, and Mike Schwartz

Administering live vaccines to a developing chick in the egg (In Ovo) has proven to be a fast (40,000 eggs per hour), effective (100% of the eggs receive the vaccine), and labor saving ($100,000 per year per hatchery) method to vaccinate baby chicks against certain diseases before they hatch. AAES researchers are now investigating the use of an automated egg vaccination machine system (Figure 1) to protect chicks from infectious bursal disease (IBD).

Figure 1. Three close-up pictures of latest embryo vaccination system.

An automated machine that delivers high speed injections to chicken embryos was first used by manufacturers of human viral vaccines, who use chicken embryos in the development of their products. The design was adapted for use by the poultry industry and the first In Ovo vaccination machine for use on chicken hatching eggs was developed by Embrex, Inc., of Raleigh, N.C. in the late 1980s (Figure 2). The latest version of this In Ovo machine currently is used in about 80% of the U.S. broiler hatcheries to administer Marek’s Disease (MD) vaccines.

Figure 2. In Ovo machine for vaccination of embryonating chicken eggs.

The robot-like machines use several dozen rubber suction nipples to pick up 18-day-old fertilized and developing eggs from the setting trays. It injects 0.1 milliliters of a vaccine mixture into the large end of each egg through the air cell with a one-inch needle. (The 18-day-old chicken embryo’s immune system is mature enough to respond efficiently to vaccination.) The eggs are then transferred into the hatchery where they remain until they hatch at about 21 days of age. The popularity of this machine, which has proven to safely and effectively vaccinate chicks against MD, is spreading worldwide, and this system also is being used increasingly to administer infectious bursal disease (IBD) vaccines. However, the safety and efficacy of the use of live IBD vaccines by In Ovo administration has not been conclusively shown.

IBD is a common, economically important disease of young chickens worldwide that reduces the immune response of infected birds and can cause morbidity and/or mortality. Because the virus is difficult to eradicate from poultry farms, early vaccination of chicks is one of the best methods of prevention.

Two identical studies at Auburn University were undertaken to examine the safety of four live commercially available IBD vaccines given by the In Ovo method. For each study, broiler hatching eggs from an Auburn University specific pathogen free (SPF) flock (birds that have never been exposed to certain disease-causing organisms) were divided into five groups, four of which were vaccinated with one of the commercial IBD vaccines and a fifth group of non-vaccinated embryos that was used as a control. The SPF eggs were obtained from SPF hens reared in isolation so that the embryos did not have maternal-derived immunity (had not inherited immunity from the hens), which could interfere with early IBD vaccination. Each group was housed in a separate isolation facility.

Safety was determined by the effect each vaccine had on hatchability, livability of the chicks to three weeks of age, and the presence of apparent (gross) or microscopic lesions (alterations) associated with IBD. At seven and 21 days of age, five chicks per group were examined for gross lesions. Tissues from the bursa of Fabricius, the target organ for IBDV replication, were tested blindly (so there could be no biasing of the results) by a lab at the University of Georgia and the microscopic lesions were scored from 1 to 4. A score of 1 is normal and 4 is severe. These microscopic lesions are a sensitive indicator of IBD.

In both studies, none of the four live vaccines adversely effected hatchability of the eggs or livability of the chicks to 21 days of age. Although microscopic lesions associated with IBD were evident at seven days of age, they were gone by 21 days of age. These results indicate that each of the four vaccines tested are safe when given by the In Ovo route to SPF chicks. Future studies will examine the efficacy of the same four vaccines in protecting chickens against challenge with virulent IBDVs.