Assessing the association between the geographic distribution of deer ticks and seropositivity rates to various tick-transmitted disease organisms indogs

Objective-To determine whether the geographic distribution of deer ticks (I xodes scapularis) was associated with the distribution of dogs seropositive for various tick-transmitted disease organisms (ie, Borrelia burgdorferi, Rickettsia rickettsii, the human granulocytic ehrlichiosis [HGE] agent, Ehr lichia canis, and Bartonella vinsonii subsp berkhoffii). Design-Serologic survey. Sample Population-Serum samples from 277 dogs in animal shelters and veteri nary hospitals in Rhode Island. Results-Overall, 143 (52%) dogs were seropositive for B burgdorferi, 59 (21 .3%) were seropositive for R rickettsii, 40 (14.4%) were seropositive for t he HGE agent, 8 (2.9%) were seropositive for E canis, and 6 (2.2%) were ser opositive for B vinsonii. Regression analysis indicated that the natural lo garithm of nymphal deer tick abundance was correlated with rate of seroposi tivity to the HGE agent and to B burgdorferi but not to rate of seropositiv ity to R rickettsii, E canis, or B vinsonii. Percentages of samples seropos itive for B burgdorferi, R rickettsii, the HGE agent, and E canis were sign ificantly higher for samples from the southwestern part of the state where ticks in general and deer licks in particular are abundant than for samples from the northern and eastern portions of the state, where ticks are relat ively rare. Conclusions and Clinical Relevance-Results suggested that all 5 disease age nts are in Rhode Island and pose a risk to dogs and humans. Knowledge conce rning tick distributions may be useful in predicting the pattern of disease associated with particular tick species and may aid diagnostic, prevention , and control efforts.