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Updated coccidiosis book addresses value of vaccination

A popular book on coccidiosis has been updated to include a new chapter on anticoccidial drugs and vaccines.

The 165-page book, Poultry Coccidiosis: Diagnostic and Testing Procedures, is authored by veterinary parasitologists Donal Conway and M. Elizabeth McKenzie. When it was first released in 1979 and a second edition was published in 1991, the book was found to be very useful for poultry scientists, disease diagnosticians and veterinarians.

The most recent edition reflects substantial progress in knowledge about coccidiosis in poultry and a growing body of critical information, Conway says.

The book includes an introduction to coccidiosis, reviews diagnostic procedures and collection and counting of oocysts. It also contains basic procedures and example protocols for testing anticoccidial drugs.

There is a tutorial on scoring gross lesions caused by major species of Eimeria infecting chickens. The review is based on the Johnson and Reid lesion scoring procedure.

For each species, lesions due to infections ranging from light to severe are illustrated by highquality images.

"Over the years, these images have been of significant value in assessing the importance and severity of both controlled and naturally occurring coccidial infections, and it is a special delight to us to review these images once again," Conway comments.

Vaccines minimize resistance

In a chapter on the epidemiology and control of coccidiosis, Conway and McKenzie state that the use of anticoccidial vaccines in a rotational program with anticoccidial drugs is recommended to minimize the risk of anticoccidial drug tolerance or resistance problems over the long term.

"The use of anticoccidial vaccines in breeders and replacement birds is probably the optimum course in most situations, and the current ability to vaccinate chicks at the hatchery by spray cabinet... has made a big difference in making anticoccidial vaccines a practical option for broiler chickens as well," say the authors, who also cover important topics such as environmental management and feed quality.

The book's new chapter on anticoccidial drugs and vaccines reviews various anticoccidials and provides a review of each drug's chemical structure, safety and efficacy. It contains an interesting history on the development of polyether ionophorous antibiotics, reviews the advantages of these drugs and includes concerns such as ionophore toxicity.

Vaccines a 'practical alternative'

Vaccines, the authors state, "provide a very practical and important alternative to the exclusive use of anticoccidial drugs for two excellent reasons."

A number of studies have demonstrated that vaccines give a comparable level of coccidiosis protection to growing broiler chickens compared to anticoccidial drug programs and most live vaccines replace indigenous coccidial populations in the broiler house with coccidia that are susceptible to anticoccidial drugs, extending the usefulness of anticoccidials, they say.

Although initial application of live vaccines was limited to layers and broiler breeders, there is currently a growing use of live anticoccidial vaccines in broiler chickens due in large part to the ability to apply vaccines in an economically effective way at the hatchery, the authors say.

In a section on Coccivac vaccines, Conway and McKenzie explain that the vaccines deliver a controlled dose of oocysts that induce sufficient infection to produce an appropriate immune response without causing a pathogenic effect after two or three life cycles of coccidia. Administration of the vaccine with the SprayCox cabinet has enhanced the uniformity of initial application, "vastly improving the vaccination response, and making other methods of vaccination such as feed spray, drinking water application, and eye spray methods much less efficient."

The updated book will be available through Blackwell Publishing Professional, 2121 State Avenue, Ames, IA 50014- 8300, USA, or through its website: www.blackwellprofessional. com or www.blackwellvet.com.

Source: Cocciforum, isuue 13

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