After treatment, anti-E. canis antibody titers may persist for months, and even for years. It has also been shown that persistence of E. canis antibody titers post-treatment was related to the initial titer at the time of treatment. The persistence of high antibody titers for extended periods after prolonged treatments may represent an aberrant immune response, or treatment failure. After successful treatment, seropositive dogs are susceptible to rechallenge. A progressive decrease in the serum gammaglobulin concentrations has been found to be associated with elimination of the parasite.