Serologic confirmation of Ehrlichia equi and Borrelia burgdorferi infections in horses from the northeastern United States

Louis A. Magnarelli Department of Entomology, the Connecticut Agricultural Experiment Station, PO Box 1106, New Haven, CT 06504.

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Jacob W. IJdo Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine, 60 College St, PO Box 208031, New Haven, CT 06520-8034.

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Amy E. Van Andel Department of Epidemiology and Public Health, Yale University School of Medicine, 60 College St, PO Box 208031, New Haven, CT 06520-8034.
Present address: Boehringer Ingelheim Pharmaceuticals Inc, 900 Ridgebury Rd, Ridgefield, CT 06877-0368.

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Caiyun Wu Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine, 60 College St, PO Box 208031, New Haven, CT 06520-8034.

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Steven J. Padula Division of Rheumatic Diseases, Department of Medicine, University of Connecticut Health Center, Farmington, CT 06030.

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Erol Fikrig Section of Rheumatology, Department of Internal Medicine, Yale University School of Medicine, 60 College St, PO Box 208031, New Haven, CT 06520-8034.

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Abstract

Objective—To determine whether horses living in tick-infested areas of northeastern United States with clinical signs of borreliosis or granulocytic ehrlichiosis had detectable serum antibodies to both Borrelia burgdorferi and Ehrlichia equi.

Design—Prospective study.

Animals—Serum samples from 51 clinically normal horses, 14 horses with clinical signs of borreliosis, and 17 horses with clinical signs of granulocytic ehrlichiosis.

Procedure—Serum B burgdorferi or E equi antibodies were measured by use of an ELISA, immunoblot analysis, or indirect fluorescent antibody (IFA) staining.

Results—Of the 82 serum samples tested, 37 (45.1%) and 13 (15.9%) had detectable antibodies to B burgdorferior E equi, respectively. Test results indicated that 12 horses had been exposed to both agents, 11 of these horses had granulocytic ehrlichiosis. The ELISA regularly detected antibodies to the following recombinant protein (p) antigens of B burgdorferi: p29, p37, p39, and p41-G. The use of immunoblot analysis confirmed ELISA results by indicating antibody reactivities to antigens of whole-cell B burgdorferi having molecular masses of predominantly 31, 34, 37, 39, 41, 58, and 93 kd.

Conclusion and Clinical Relevance—Horses living in areas where ticks (Ixodes scapularis) abound are sometimes exposed to multiple pathogens. Analyses for specific recombinant borrelial antibodies using an ELISA can help separate horses with borreliosis from those with granulocytic ehrlichiosis, even when antibodies to both etiologic agents are detected in serum samples. Analysis using immunoblots is sensitive, and along with ELISA or IFA procedures, is suitable for confirming a clinical diagnosis of each disease (J Am Vet Med Assoc 2000;217:1045–1050)

Abstract

Objective—To determine whether horses living in tick-infested areas of northeastern United States with clinical signs of borreliosis or granulocytic ehrlichiosis had detectable serum antibodies to both Borrelia burgdorferi and Ehrlichia equi.

Design—Prospective study.

Animals—Serum samples from 51 clinically normal horses, 14 horses with clinical signs of borreliosis, and 17 horses with clinical signs of granulocytic ehrlichiosis.

Procedure—Serum B burgdorferi or E equi antibodies were measured by use of an ELISA, immunoblot analysis, or indirect fluorescent antibody (IFA) staining.

Results—Of the 82 serum samples tested, 37 (45.1%) and 13 (15.9%) had detectable antibodies to B burgdorferior E equi, respectively. Test results indicated that 12 horses had been exposed to both agents, 11 of these horses had granulocytic ehrlichiosis. The ELISA regularly detected antibodies to the following recombinant protein (p) antigens of B burgdorferi: p29, p37, p39, and p41-G. The use of immunoblot analysis confirmed ELISA results by indicating antibody reactivities to antigens of whole-cell B burgdorferi having molecular masses of predominantly 31, 34, 37, 39, 41, 58, and 93 kd.

Conclusion and Clinical Relevance—Horses living in areas where ticks (Ixodes scapularis) abound are sometimes exposed to multiple pathogens. Analyses for specific recombinant borrelial antibodies using an ELISA can help separate horses with borreliosis from those with granulocytic ehrlichiosis, even when antibodies to both etiologic agents are detected in serum samples. Analysis using immunoblots is sensitive, and along with ELISA or IFA procedures, is suitable for confirming a clinical diagnosis of each disease (J Am Vet Med Assoc 2000;217:1045–1050)

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