A serological and clinical follow-up in horses with confirmed equine granulocytic ehrlichiosis

For diagnosis of equine granulocytic ehrlichiosis (EGE) serological testing of antibodies to Ehrlichia equi is frequently used. An elevated antibody l evel is often misinterpreted as confirmative of active infection and result s in treatment with antibiotics. If only seropositivity is considered as th e diagnostic criterium, many horses showing convalescence titres will be tr eated. This study was undertaken to obtain information about the kinetics o f antibodies during the course of infection and, for this purpose, 45 horse s with clinical signs of EGE and confirmed ehrlichiaemia were monitored ser ologically and clinically over time. For a correct handling of cases with s uspected EGE, the following results should be helpful: (i) 44% of the horse s in the acute ehrlichiaemic stage were found to be serologically positive to E. equi; (ii) all horses show-ed a rapid increase in antibody titre, rea ching maximum value within a month after the ehrlichiaemic stage; (iii) whe n 8 months had passed, titres had decreased, but 18 of 24 examined horses w ere still serologically positive; (iv) after 12-15 months most of the horse s (n = 10) were serologically negative; and (v) the period required for com plete clinical recovery varied from one day up to 6 months after antibiotic treatment.