Reactivity of serum samples of dogs and horses tested by use of class-specific recombinant-based enzyme-linked immunosorbent assays for detection of granulocytic ehrlichiosis

Objective-To test serum samples of dogs and horses by use of class-specific recombinant-based ELISA for establishing a diagnosis of granulocytic ehrli chiosis attributable to infection with organisms from the Ehrlichia phagocy tophila genogroup. Sample Population-Serum samples from 43 client-owned dogs and 131 horses (8 1 with signs of acute illness and 50 without signs of disease). Procedure-Serum samples were analyzed, using ELISA with a recombinant 44-kd protein antigen for IgM and IgG antibodies to the human granulocytic ehrli chiosis (HGE) agent (NCH-1 strain). Western blot analyses, using infected h uman promyelocytic leukemia cells, were conducted on 38 serum samples of ho rses and 11 serum samples of dogs to verify reactivity to the 44-kd peptide . Results-IgM or IgG antibodies to the HGE agent were detected in 5 to 28% of dog serum samples and 5 to 37% of horse serum samples. Thirty-five of 38 ( 92%) horse serum samples had corresponding results on both tests (2 positiv e results for 26 samples and 2 negative results for 9 samples), using an EL ISA for IgG antibodies or immunoblotting for total immunoglobulins. All 11 serum samples of dogs had positive results for both methods. Conclusion and Clinical Relevance-These ELISA with recombinant 44-kd antige n are suitable for detecting IgM or IgG antibodies to the HGE agent In seru m samples of dogs and horses. Positive results for serum samples of horses from Connecticut, New York, Virginia, and Georgia indicate that the HGE age nt Is widely distributed in tick-Infested areas of the eastern United State s.