With regards to chicken vaccines, making sure all newborn chicks are vaccinated right out of the hatchery isn’t always easy. Some birds may be missed by standard poultry vaccination methods and consequently, left with little defense against intestinal diseases.
Developed by scientists at the Agricultural Research Service, a new vaccine delivery system to prevent diseases like coccidiosis may be more appetizing to birds than traditional methods.
Coccidiosis, a common and costly poultry disease, is caused by tiny, single-celled parasites. These parasites, which belong to the genus Eimeria, live and multiply in the intestinal tract and cause tissue damage that hinders the bird’s ability to digest feed and absorb nutrients. Infected birds shed oocysts transform into infectious forms once in litter, soil, feed or water.
As chickens peck around in the litter, they can ingest the oocysts and become infected. The results are slower weight gain and growth and sometimes death.
The disease cocts an estimated $350million in the United States and more than $3billion worldwide each year until recently, coccidiosis outbreaks were mainly controlled by medicating feed with anticoccidial drugs, but the parasite’s increasing resistance to drugs prompted the development of vaccines.
Scientists at ARS’s Henry A. Wallace Beltsville Agricultural Research Center (BARC) in Beltsville, Maryland are developing better vaccines and methods of protection against coccidiosis and other poultry diseases.
Collaborating with researchers at the nonprofit Southwest Research Institute (SwRI) in San Antonio, Texas, they have developed an effective vaccine delivery system by putting low doses of live Eimeria oocysts inside gelatin beads that chickens readily gobble up.
Bead Vaccines are Better
Microbiologist Mark Jenkins and Zoologist Ray Fetterer, in BARS’s Animal Parasitic Diseases Laboratory are attempting to increase vaccine uptake by studying alternative delivery methods.
With the standard industry vaccination method, about 100 chicks at a time are placed into a tray that’s detected by a light sensor as it moves, activating the release of vaccine spray above the heads pf the chicks.
A harmless red dye in the spray is used to identify birds that have been vaccinated. Chicks inhale or ingest the vaccine, which induces protection against disease.
Jenkins used a hand-held sprayer to deliver a vaccine formulation to newly hatched chicks, and then he measured vaccine uptake. “With spraying, some chicks were getting a lot of the vaccine and some weren’t getting any,” Jekins says, leaving then vulnerable to acute coccidiosis and associated necrotic enteritis.
Scientists looked at gelatin beads as an alternative vaccination method. They experimented with different formulations, sizes and colors. The beads they settled on were red or green and about 2 millimeters in diameter, similar to the size of feed grains fed to young chicks.
“Our primary goal was to develop a formulation that would prevent the gelatin beads from drying out when they’re put into poultry houses, where temperatures can exceed 90°F,” says Joseph Persyn, SwRI manager of microencapsulation and nanomaterials.
“The beads needed to retain moisture to keep the Eimeria oocysts active and to remain pliable so the chicks would eat them.” When beads dry out, they become as hard as pebbles, Persyn adds.
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Beads for Broilers
After seeing positive results in chicks of egg-layer hens, Jekins and Fetterer evaluated the effectiveness of the gelatin bead vaccine in broilers, which are raised for meat.
Vaccine uptake and protection against Eimeria challenge infection was compared between day-old chicks fed gelatin beads, those immunized with a hand-held sprayer and a control group.
Chicks fed gelatin beads had a vaccine uptake 10-to-100-fold grater than the spray-vaccine group. Also, birds that consumed vaccine beads displayed higher and more uniform protection against coccidiosis than spra-vaccinated birds.
“Response was amazing in broilers,” Jekins says, “You put them in a cage and they run over and start eating right.