Open AccessEhrlichia equi Infection of Horses from Minnesota and Wisconsin: Detection of Seroconversion and Acute Disease Investigation
Author(s) -
Bullock Patricia M.,
Ames Trevor R.,
Robinson Robert A.,
Greig Barbara,
Mellencamp Martha A.,
Dumler J. Steven
Publication year - 2000
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/j.1939-1676.2000.tb01163.x
Subject(s) - ehrlichia , seroprevalence , ixodes scapularis , ehrlichiosis , seroconversion , virology , tick , serology , medicine , veterinary medicine , tick borne disease , ixodes , polymerase chain reaction , biology , antibody , immunology , ixodidae , virus , biochemistry , gene
Equine granulocytic ehrlichiosis (EGE) is caused by infection with Ehrlichia equi . EGE has been reported primarily in northern California, where E equi is transmitted by the tick Ixodes pacificus . Reports of EGE and the emergence of human granulocytic ehrlichia in Minnesota prompted a seroprevalence study of E equi in horses of Minnesota and Wisconsin. Tick ( Ixodes scapularis ) endemic areas of Minnesota and Wisconsin were compared to nonendemic regions of Minnesota. Indirect fluorescent antibody was used to detect the presence of serum antibodies to E equi . Serum samples from healthy horses, 375 samples from I scapularis endemic counties, and 366 samples from nonendemic counties were screened at a 1:40 dilution. Results demonstrated a seroprevalence of 17.6% in endemic areas versus 3.8% in nonendemic areas. Ehrlichial DNA from 2 samples was successfully amplified by polymerase chain reaction and 919 base pairs were sequenced. The DNA sequence of 1 Minnesota/Wisconsin strain differed from the GenBank strain (M73223) of E equi at positions 84 and 886 and from the MRK strain of E equi at position 84, and was identical to the human granulocytic ehrlichiosis (HGE) agent. The 2nd Minnesota/Wisconsin strain was identical to the 1st with the exception of a substitution of “A” at position 453 that is not present in E phagocytophila, E equi , or HGE agent strain sequences. Based on the results of this study, we concluded that E equi is present and causes infection in horses in Minnesota and Wisconsin. The occurrence of infection is higher in tick endemic regions.