Chapter 4: Vaccination

Authors: Jenkins, Mark

Submitted to: Coccidiosis in Livestock, Poultry, Companion Animals, and Humans
Publication Type: Book / Chapter
Publication Acceptance Date: 11/22/2019
Publication Date: 12/11/2019
Citation: Jenkins, M.C. 2019. Chapter 4: Vaccination. In Dubey, J.P., editor. Coccidiosis in Livestock, Poultry, Companion Animals, and Humans. Boca Raton, LA: CRC Press. P. 51-58.

Interpretive Summary: Avian coccidiosis is a protozoan disease caused by parasites in the genus Eimeria that inflicts annual losses over $ 1 billion in the U.S. alone and $ 10 billion worldwide. The disease affects weight gain and feed utilization efficiency in broilers and the number of eggs produced in egg laying hens. Of equal importance is that coccidiosis predisposes chickens to bacterial diseases of the gut, particularly necrotic enteritis caused by Clostridium perfringens which can lead to acute death due to the release of toxins by the Clostridium bacteria. Avian coccidiosis has been controlled for decades by the medication of feed with anticoccidial drugs. However, drug resistance in Eimeria and increasing consumer demand for chickens grown in the absence of antibiotics has prompted the use of alternative measures, such as vaccination. Although it has been known for almost 100 years that Eimeria can elicit full protective immunity in chickens after a single infection, it was only in the last 10 years that vaccination with low doses of Eimeria has gained widespread use in the poultry industry. There are some issues associated with vaccination such as non-uniform delivery of the vaccine and the propensity of some Eimeria to avoid immunity by altering its surface coat to avoid immune destruction by the host. Scientists are also working on subunit vaccines that are composed of single constituents of the parasite, but produced in culture by bacteria or yeast.

Technical Abstract: Avian coccidiosis is regularly listed by poultry veterinarians as the most important poultry disease affecting performance of broilers and egg-layers. Worldwide, this parasitic disease costs poultry growers and companies over $1 billion in losses due to unrealized weight gain, poor feed conversion efficiency, and the cost of anticoccidial controls, be it drugs or live Eimeria oocyst vaccines. Increased morin broilers between 2.5 and 3.5 weeks of age are most often due to necrotic enteritis associated with acute coccidiosis infection. Like Eimeria oocysts, Clostridium perfringens spores are capable of resisting inactivation in litter and are prevalent throughout growout. Eimeria vaccines are attractive because they can be used in rotation throughout the year in place of ionophores and synthetic chemicals, and thereby stem the inevitable anticoccidial drug resistance that occurs when these compounds are continually used. The major obstacle in the use of live Eimeria vaccines is how to ensure each chick ingests a minimum dose of oocysts so that subsequent exposure to Eimeria oocysts in litter has a boosting effect rather than causing outright enteric dis Improving vaccine delivery, reducing the carryover of viable Eimeria oocysts during downtime (2 -3 weeks) in a poultry house, and gaining an understanding of how genetic diversity affects vaccine design are just three of the many research areas ripe for investigation.