Based on the guidelines for the interpretation of RMSF antibody titers, 23 dogs had IgM titer (≥16) without presence of IgG suggesting infection within the past 2–4 weeks, four dogs had IgM titers ≤8 and IgG titers ≥512, indicating infection within 2 weeks to 3 months, 13 dogs had elevated titers for both antibodies, indicating past infection within 4–8 weeks, and 23 dogs had IgM titers ≤8 and IgG titers = 64–256, indicating past infection. This evidence concerns the gene CD40LG and infection.