Date of Graduation

12-2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Poultry Science (PhD)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

H. David Chapman

Committee Member

Michael F. Slavik

Second Committee Member

Thomas A. Yazwinski

Keywords

Attenuation, Coccidiosis, Eimeria, Turkey

Abstract

Coccidiosis is an economically important enteric disease of poultry caused by protozoan parasites belonging to the genus Eimeria. Drugs are most commonly used to control coccidiosis. Widespread usage of anticoccidial drugs in the field has resulted in development of drug resistant strains and consequently decreased drug efficacy. An alternative control strategy using attenuated vaccines is desired. A series of experiments was designed to identify, isolate and attenuate a strain of a common and pathogenic species of Eimeria of turkeys, E. meleagrimitis.

Sensitivity of field isolates of turkey coccidia to the anticoccidials drugs amprolium, clopidol, diclazuril, and monensin was investigated. A total of thirty-four isolates comprising mixed species from farms across the country were tested. Of these, four isolates were sensitive to monensin, twelve sensitive to diclazuril, and seventeen sensitive to clopidol and none to amprolium. One isolate, designated MN2, was sensitive to three drugs tested and was selected for further investigation. The different Eimeria species present in the isolates were identified using polymerase chain reaction amplification of cox-1 gene and E. meleagrimitis was the most common species seen. A pure clone of E. meleagrimitis was developed and the pathogenicity and fecundity of the isolated E. meleagrimitis strain was tested and compared to a standard reference E. meleagrimitis strain. Data from the parameters tested showed that the strain had the same characteristics as that of the reference strain.

An attenuated line of E. meleagrimitis was developed by repeated propagation of the parasite in turkeys and collection of the very first oocysts produced following infection. After twenty generations of selection, a line with abbreviated life cycle of -16h was developed. Pathogenicity and immunogenicity of this line was tested and compared with the parent strain. The attenuated line was proven to be non-pathogenic but was immunogenic. The developed line is a candidate for attenuated vaccine against turkey coccidiosis.

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