Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/1997
Publication Date: N/A
Interpretive Summary: Avian coccidiosis, an intestinal disease of poultry caused by protozoan parasites, is estimated to cost the U.S. poultry farmer and industry over $350 million annually. Control of this disease has relied on the use of anticoccidial compounds usually given in the feed, but within the past 10 years these drugs have started losing their effectiveness because of the development by the parasite of drug resistance. This problem has resulted in renewed interest by the poultry industry in the use of immunization to control the disease. Vaccines using viable parasites to give a low level infection to produce protective immunity have been on the market for a number of years, but have not been used by the industry because of poor results. The development of a gel-immunization technique used to deliver the vaccine to day old chicks at the hatchery seemed, in previously run laboratory experiments, to increase the protection given chickens against this disease. In the present study, this immunization technique was used with a modified vaccine containing field isolates of the coccidia in protection trials run in actual poultry houses in Delaware. Results showed that high levels of immunity occurred and the birds from the houses given the vaccine had average weight gains and feed conversions that were equal to or better than anticoccidial medicated groups. This type of immunization can now be used as an effective control of the disease, and is an alternative to use of anticoccidial medication.
Technical Abstract: The use of a gel-immunization technique for administration of a viable oocyst vaccine containing an isolated field strain of Eimeria maxima for the protection of male roaster flocks against avian coccidia was evaluated in 5 separate four-paired house field trials. Results of these studies showed that high infection rates as measured by microscopic examination of intestinal scrapings were obtained in gel- immunized birds by 2-5 weeks post-immunization. Gross intestinal lesion scores decreased in immunized birds between 2-3 and 4-5 weeks of age. Oocyst number in the litter of gel-immunized Test houses decreased between 2-3 and 4-5 weeks of age in 4 out of the 5 Trials. Lower average bird weights occurred in the immunized birds for all Trials at 4 weeks of age and all but one immunized group at 8 weeks of age when compared to nonimmunized anticoccidial treated control groups. Average bird weights and net flock weights at time of processing were lower in Trial 1 for birds immunized with a vaccine that contained a lower number of oocysts. In Trials 2-5, which were immunized with a vaccine containing higher oocyst numbers, average immunized bird weights and net flock weights at time of processing were much improved, and in 3 of 4 Trials were higher than the nonimmunized medicated controls. Feed conversions were higher in the immunized birds in Trial 1 when compared to controls, but were equal to or lower than the control groups in 3 of the 4 other Trials, averaging 0.018 points lower than controls. Total average percent mortality of all 5 Trials was lower with the immunized birds.