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Schering-Plough Animal Health's technical service team answers questions about managing coccidiosis

A. Several reasons. In a nutshell: Traditional, in-feed anticoccidials such as salinomycin and other ionophores have been so widely used that resistance to them is developing, resulting in coccidiosis outbreaks. Furthermore, consumer demand has increased for birds raised with fewer drugs in the food chain. Immunization offers a more natural approach for control of coccidiosis in poultry. In recent years, new methods of administering coccidiosis vaccination have been developed to ensure better uniformity and efficacy than in the past.

Q. DOES IMMUNITY INDUCED BY COCCIDIOSIS VACCINATION AGAINST ONE COCCIDIAL SPECIES PROVIDE CROSS-PROTECTION AGAINST OTHER COCCIDIAL SPECIES?

A. No. Immunity against one particular coccidial species is specific and will not protect against another coccidial species. Consequently, vaccines each contain several species of coccidia known to be a problem in the targeted bird population. That's how broad protection against coccidiosis is achieved with vaccines.

Q. WON'T BIRDS DEVELOP IMMUNITY TO COCCIDIA ON THEIR OWN, WITHOUT VACCINATION?

A. It's possible if birds are accidentally exposed to infective oocysts. But the development of immunity also depends on how often and how long birds are exposed and they may not be exposed to all the various species of coccidia that could pose a problem down the road. The development of natural immunity also may not be realized until at least 6 weeks of age.

In other words, the development of adequate natural immunity soon enough to meet the needs of poultry producers cannot be guaranteed. That's why the acquisition of immunity through controlled exposure by vaccination is preferable.

Q. CAN RESISTANCE TO COCCIDIAL ORGANISMS DEVELOP WHEN VACCINATIONS ARE USED TO MANAGE COCCIDIOSIS?

A. No. Vaccination enables birds to naturally develop lifelong immunity against coccidia, which helps prevent the development of coccidiosis. No resistance develops. In contrast, in-feed anticoccidials control the development of coccidiosis by minimizing the existing population of coccidia. This is an entirely different approach to coccidiosis control that can and has resulted in the development of resistance to anticoccidials, particularly those used over a long period of time.

Q. CAN COCCIDIOSIS VACCINATION HELP RESTORE EIMERIA SENSITIVITY TO SALINOMYCIN AND OTHER IONOPHORES?

A. It can, as long as the vaccine used provides live, drug-sensitive coccidia. Research conducted by Dr. Harry D. Danforth, PhD, a USDA research microbiologist, has demonstrated that vaccinating with Coccivac-B "a product containing live, drug-sensitive coccidia "changes the sensitivity of coccidia on the floor of grow-out houses. More specifically, studies by Danforth showed that using this type of vaccine helped restore sensitivity to the ionophore salinomycin.

When live coccidial oocysts are delivered with the vaccine, they replicate and replace drug-resistant field strains. The coccidial population in the house shifts to the more sensitive strains. Because most ionophores work the same in inhibiting coccidia, it can be extrapolated that sensitivity should be restored for other ionophores as well. Vaccination with coccidia that are not sensitive to drugs or that are salinomycin resistant would not restore sensitivity.

Danforth's work also shows that after vaccination with a live-oocyst vaccine, an aggressive Eimeria tenella strain disappeared altogether and that lesions due to other species of Eimeria were minimized.

Q. COULD VACCINATION INTRODUCE MYCOPLASMA OR OTHER DISEASES TO BIRDS?

A. Not if it's a high-quality product made by a reputable manufacturer. Coccivac-B, for example, is produced according to strict quality-control methods and undergoes multiple tests to ensure purity. Schering-Plough Animal Health tests the product during several stages of production to make sure that final batches are free of bacteria, fungi and mycoplasma, even though mycoplasma testing for coccidiosis vaccines is not required by the USDA.

Special extra testing also is conducted when indicated. A few years ago, poultry producers were concerned about a new avian leucosis virus subgroup known as J virus. A study initiated in collaboration with the University of Delaware demonstrated that production procedures for producing Coccivac vaccines would eliminate J virus if it were present. Another similar study conducted later showed that Coccivac vaccine production also would eliminate chick anemia virus.

Q. A FEW DAYS AFTER BIRDS ARE VACCINATED FOR COCCIDIOSIS, SOME ARE STILL STAINED FROM THE DYE USED IN THE VACCINE TO CHECK FOR UNIFORM COVERAGE. DOES THE PRESENCE OF THE DYE MEAN THAT SOME OOCYSTS FROM THE PRODUCT HAVE NOT BEEN INGESTED?

A. Chicks are attracted to reds and other primary colors, so the red dye in a coccidiosis vaccine actually encourages preening by chicks in the hatchery. The ingestion of oocysts occurs immediately following vaccination. The lingering presence of the dye indicates that the birds have in fact been properly vaccinated, but does not mean that any vaccine has gone unused.

Have more questions about coccidiosis vaccination? Send yours to the editor at [email protected] or by fax to 928-569-2491. You'll get a personal reply from a Schering- Plough Animal Health Corporation technical service representative and we may include it in our next issue of CocciForum.

Source: CocciForum Issue No.6, Schering-Plough Animal Health.

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