Canine infection with Dirofilaria immitis, Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. in the United States, 2013–2019

Abstract

Background Dogs in the US are commonly infected with vector-borne pathogens, including heartworm and tick-borne disease agents. The geographic distribution of both arthropod vectors and the pathogens they transmit continues to expand. Methods To describe the current geographic distribution and prevalence of antigen of Dirofilaria immitis and antibody to Borrelia burgdorferi, Ehrlichia spp., and Anaplasma spp. in dogs, we summarized over 144 million test results from 2013 to 2019, inclusive, by county, state, and region. Canine seroprevalence by state was compared to population-adjusted human reports of tick-borne diseases. Results Results varied regionally, with D. immitis antigen and Ehrlichia spp. antibodies more frequently detected in the Southeast (2.6% and 5.2%, respectively) and antibody to B. burgdorferi and Anaplasma spp. most common in the Northeast (12.1% and 7.3%, respectively). Overall, percent positive test results to D. immitis decreased in the Southeast by 33.3% when compared to earlier summaries using the same strategy (from 3.9 to 2.6%). Geographic expansion of areas where dogs commonly test positive for Ehrlichia spp. was evident, likely because of a change in the test made in 2012 to allow detection of antibodies to E. ewingii concomitant with expansion of vector tick populations. Percent positive test results to Ehrlichia spp. increased in every region; this shift was particularly pronounced in the Southeast, where percent positive test results increased fourfold (from 1.3 to 5.2%). Continued geographic expansion of B. burgdorferi and A. phagocytophilum was apparent in the Northeast, Midwest, and Upper South, although canine seroprevalence of antibody to B. burgdorferi was much lower than prior surveys in many Lyme-endemic areas. Annual reports of human cases of Lyme disease, ehrlichiosis, and anaplasmosis were associated with percent positive canine results by state for the three tick-borne disease agents (R2 = 0.812, 0.521, and 0.546, respectively). Within endemic areas, percent positive test results for all three tick-borne agents demonstrated evidence of geographic expansion. Conclusions Large scale analysis of results from screening dogs in practice for evidence of vector-borne infections, including those with zoonotic importance, continues to be a valuable strategy for understanding geographic trends in infection risk over time.

Epidemiological and Clinicopathological Features of Anaplasma phagocytophilum Infection in Dogs: A Systematic Review

“…The geographical distribution of canine infection seems to parallel the distribution of HGA in the USA with a positive association of human and canine cases in many states ( 3 , 23 ). Indeed, several studies found the highest prevalence rates of A. phagocytophilum antibodies in dogs from the upper midwest, northeast, and mid-atlantic, which correlate with areas where the highest incidence of human anaplasmosis were reported ( 3 , 4 , 9 , 15 , 22 , 23 ). In addition, the estimated regression coefficient for the endemic risk factor in the contiguous USA model was positive and significant.…”

“…Five countrywide serologic studies showed an overall prevalence of Anaplasma spp. of 1.9 to 4.8% with the highest rates recorded in northeastern regions ( 3 , 9 , 15 , 23 , 119 ). The study that found a prevalence rate of 1.9%, used species-specific peptides to detect canine antibodies to A. phagocytophilum ( 3 ).…”

“…Serologic surveys revealed prevalence values of Anaplasma spp. antibodies ranging from 0.0 to 40.0% ( 3 , 9 , 10 , 12 , 13 , 15 , 23 , 119 , 120 , 122 – 126 , 236 , 242 , 244 , 245 ). Five countrywide serologic studies showed an overall prevalence of Anaplasma spp.…”

“…Because of their proximity to humans, dogs may serve as reservoirs of vector-borne pathogens, a source of infection for vectors, mechanical transporters of infected vectors, and as sentinel indicators of regional infection risk ( 2 , 3 , 10 – 15 ). Furthermore, the strong molecular similarity between human and canine isolates of A. phagocytophilum in Europe and the USA ( 16 – 21 ) and the positive association in the distributions of human and canine cases in the USA emphasizes the use for dogs as sentinels in epidemiological studies ( 3 , 4 , 9 , 15 , 22 , 23 ).…”

Exposure to Major Vector-Borne Diseases in Dogs Subjected to Different Preventative Regimens in Endemic Areas of Italy

“…Bacterial tick-borne diseases (TBDs) also play an important role in canine medicine, as Ehrlichia spp., Anaplasma spp., Borrelia spp. and Rickettsia conorii are the most common throughout Europe and elsewhere [ 14 , 15 , 16 , 17 ]. Most of the abovementioned pathogens have a zoonotic potential and represent a threat for human health [ 2 , 18 ].…”