Vector-borne infections in dogs occur throughout the US; however, temporal trends in prevalence for most infections have been poorly described. The objective of this study was to evaluate the seroprevalence of Anaplasma spp., Babesia canis, Bartonella henselae, Bartonella vinsonii subsp. berkhoffii, Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia canis, and Rickettsia rickettsii in dog blood samples submitted to the Vector-Borne Diseases Diagnostic Laboratory at NCSU from January 2004 to December 2006. From the laboratory database, 7049 accessions (2208 dogs in 2004, 2400 dogs in 2005 and 2441 dogs in 2006), for which serological results were available for at least three test organisms, were selected for analyses. An indirect immunofluorescence assay (IFA) with a cut-off of 1:64 was used to detect exposure to B. canis B. henselae, B. v. berkhoffii, E. canis and R. rickettsii. The Snap® 4Dx® was used to detect exposure to Anaplasma spp., B. burgdorferi, D. immitis and E. canis. Gender information was available only for 2006, with 1218 males and 1179 females. 6775 samples (96.1%) were submitted from 47 states of the US, with South and Midwest regions overrepresented (68.1% and 20.1% of US samples, respectively). 274 samples (3.9%) were submitted from Canada. Seroprevalences in 2004, 2005 and 2006 are presented below:

A significant decrease in B. henselae seroprevalence occurred from 2004 to 2006 in northeastern states (12%, 2.7% and 4.7%, p=0.02), in southern states (11.5%, 4.6% and 3.8%, p<0.0001), especially in the south Atlantic states (DC, DE, FL, GA, MD, NC, SC, GA, and WV) and in Canada (16.3%, 4.7% and 0%, p=0.0004). A significant increase in B. v. berkhoffii seroprevalence occurred from 2004 to 2006 in Midwestern states (0.8%, 2.2% and 3.1%, p=0.027), especially in IL, IN, MI, OH, and WI, and in southern states (1.2%, 1.9% and 2.8%, p=0.002), especially in south Atlantic states. There was a significant increase in R. rickettsii seroprevalence from 2004 to 2006 in midwestern states (2.2%, 6.9%, and 9.2%, p<0.0001) and in southern states (6.7%, 19.7%, and 19.2%, p<0.0001), especially in south Atlantic states. Ehrlichia canis exposure defined by IFA and Snap® 4Dx® test results were similar in 96.7% of the samples (Kappa: 0.641, CI: 0.596-0.686). Monitoring vector-borne exposures in pets over years is critical for establishing trends and future actions, not only in veterinary, but also in human medicine.