B.A. Stillman1; K. Caterina-DeBisceglie1; J. Bradley2; J. Saucier1; E.B. Breitschwerdt2; S.D. Gaunt3; T. O'Connor1; R. Chandrashekar1
In an effort to better understand serological changes in dogs following Ehrlichia canis infection and treatment, we monitored antibody levels in two groups of dogs experimentally infected with E. canis, before and after treatment with doxycycline. Twelve dogs were infected with E. canis; six dogs were subsequently treated at 28 days post-infection, while six dogs remained untreated. Serum samples obtained throughout the course of infection and during and following treatment were evaluated by microtiter plate-format ELISAs to detect antibodies against two different major immunoreactive E. canis proteins (p16 and p30), by IFA, and by SNAP®4Dx® (IDEXX Laboratories). For the majority of dogs (7 of 12), the p16 and IFA assays detected antibodies by day 14, while the p30 and SNAP 4Dx assays became positive around day 21. In doxycycline-treated dogs (10 mg/kg, SID, 28 days), titers of antibodies peaked between post-infection days 20 and 80, and p16 antibodies decreased following treatment more quickly than p30 antibodies over time. IFA titers and SNAP 4Dx assay spot intensity values also decreased in the treated group. In untreated dogs, antibody levels remained high in all assays out to 200 days post-infection (no decrease from early post-infection levels). These studies detail the antibody response to p16, p30 and E. canis whole cell antigens during pre- and post-treatment phases of canine ehrlichiosis. These data, together with other data derived in this study, indicate that antibody levels should decrease progressively following successful treatment of canine ehrlichiosis.