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Risk of postnatal exposure to Sarcocystis neurona and Neospora hughesi in horses

Paulo de C. DuarteDepartment of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.
Present address is Animal Population Health Institute, Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1681.

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Patricia A. ConradDepartments of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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W. David WilsonDepartment of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Gregory L. FerraroCenter for Equine Health, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Andrea E. PackhamDepartments of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Jeanne Bowers-LeporeHarris Farm Incorporated, 27366 W Oakland Ave, Coalinga, CA 93210.

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Tim E. CarpenterDepartment of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Ian A. GardnerDepartment of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA 95616.

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Abstract

Objective—To estimate risk of exposure and age at first exposure to Sarcocystis neurona and Neospora hughesi and time to maternal antibody decay in foals.

Animals—484 Thoroughbred and Warmblood foals from 4 farms in California.

Procedure—Serum was collected before and after colostrum ingestion and at 3-month intervals thereafter. Samples were tested by use of the indirect fluorescent antibody test; cutoff titers were ≥ 40 and ≥ 160 for S neurona and N hughesi, respectively.

Results—Risk of exposure to S neurona and N hughesi during the study were 8.2% and 3.1%, respectively. Annual rate of exposure was 3.1% for S neurona and 1.7% for N hughesi. There was a significant difference in the risk of exposure to S neurona among farms but not in the risk of exposure to N hughesi. Median age at first exposure was 1.2 years for S neurona and 0.8 years for N hughesi. Highest prevalence of antibodies against S neurona and N hughesi was 6% and 2.1%, respectively, at a mean age of 1.7 and 1.4 years, respectively. Median time to maternal antibody decay was 96 days for S neurona and 91 days for N hughesi. There were no clinical cases of equine protozoal myeloenchaphlitis (EPM).

Conclusions and Clinical Relevance—Exposure to S neurona and N hughesi was low in foals between birth and 2.5 years of age. Maternally acquired antibodies may cause false-positive results for 3 or 4 months after birth, and EPM was a rare clinical disease in horses ≤ 2.5 years of age. (Am J Vet Res 2004;65:1047–1052)

Abstract

Objective—To estimate risk of exposure and age at first exposure to Sarcocystis neurona and Neospora hughesi and time to maternal antibody decay in foals.

Animals—484 Thoroughbred and Warmblood foals from 4 farms in California.

Procedure—Serum was collected before and after colostrum ingestion and at 3-month intervals thereafter. Samples were tested by use of the indirect fluorescent antibody test; cutoff titers were ≥ 40 and ≥ 160 for S neurona and N hughesi, respectively.

Results—Risk of exposure to S neurona and N hughesi during the study were 8.2% and 3.1%, respectively. Annual rate of exposure was 3.1% for S neurona and 1.7% for N hughesi. There was a significant difference in the risk of exposure to S neurona among farms but not in the risk of exposure to N hughesi. Median age at first exposure was 1.2 years for S neurona and 0.8 years for N hughesi. Highest prevalence of antibodies against S neurona and N hughesi was 6% and 2.1%, respectively, at a mean age of 1.7 and 1.4 years, respectively. Median time to maternal antibody decay was 96 days for S neurona and 91 days for N hughesi. There were no clinical cases of equine protozoal myeloenchaphlitis (EPM).

Conclusions and Clinical Relevance—Exposure to S neurona and N hughesi was low in foals between birth and 2.5 years of age. Maternally acquired antibodies may cause false-positive results for 3 or 4 months after birth, and EPM was a rare clinical disease in horses ≤ 2.5 years of age. (Am J Vet Res 2004;65:1047–1052)