Background Vector-borne infections pose significant health risks to humans, domestic animals, and wildlife. Domestic dogs (Canis lupus familiaris) in the United States may be infected with and serve as sentinel hosts for several zoonotic vector-borne pathogens. In this study, we analyzed the geographical distribution, risk factors, and co-infections associated with infection with Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi, and Dirofilaria immitis in shelter dogs in the Eastern United States. Methods From 2016 to 2020, blood samples from 3750 shelter dogs from 19 states were examined with IDEXX SNAP® 4Dx® Plus tests to determine the seroprevalence of infection with tick-borne pathogens and infection with D. immitis. We assessed the impact of factors including age, sex, intact status, breed group, and location on infection using logistic regression. Results The overall seroprevalence of D. immitis was 11.2% (n = 419/3750), the seroprevalence of Anaplasma spp. was 2.4% (n = 90/3750), the seroprevalence of Ehrlichia spp. was 8.0% (n = 299/3750), and the seroprevalence of B. burgdorferi was 8.9% (n = 332/3750). Regional variation in seroprevalence was noted: D. immitis (17.4%, n = 355/2036) and Ehrlichia spp. (10.7%, n = 217/2036) were highest in the Southeast while seroprevalence for B. burgdorferi (19.3%, n = 143/740) and Anaplasma spp. (5.7%, n = 42/740) were highest in the Northeast. Overall, 4.8% (n = 179/3750) of dogs had co-infections, the most common of which were D. immitis/Ehrlichia spp. (1.6%, n = 59/3750), B. burgdorferi/Anaplasma spp. (1.5%, n = 55/3750), and B. burgdorferi/Ehrlichia spp. (1.2%, n = 46/3750). Risk factors significantly influenced infection across the evaluated pathogens were location and breed group. All evaluated risk factors were significant for the seroprevalence of D. immitis antigens. Conclusions Our results demonstrate a regionally variable risk of infection with vector-borne pathogens in shelter dogs throughout the Eastern United States, likely due to varying distributions of vectors. However, as many vectors are undergoing range expansions or other changes in distribution associated with climate and landscape change, continued vector-borne pathogen surveillance is important for maintaining reliable risk assessment. Graphical Abstract

Anthelmintic resistance (AR) in gastrointestinal nematodes of cattle is becoming increasingly prevalent worldwide, so there exists a need to develop novel approaches to manage and slow this progression. Refugia are the proportion of the worm population not selected by drug treatment, and the greater the proportion of the worm population left untreated (in refugia), the slower the progression of AR. Sources of refugia include worms in animals left untreated, stages of parasites not affected by the treatment, and free-living stages in the environment (e.g. eggs/larvae on pasture). Studies in sheep demonstrate that managing refugia will reduce the progression of AR without negatively impacting the health or productivity of the flock. However, many of these strategies are impractical for use with cattle, and consequently have not been tested or widely implemented in cattle. One refugia-based strategy with good potential applicability to the cattle industry is 'selective non-treatment’ where a percentage of the herd is deliberately left untreated. In this study, we examined the use of a selective non-treatment strategy in Stocker cattle.

Background Vector-borne infections pose significant health risks to humans, domestic animals, and wildlife. Domestic dogs (Canis lupus familiaris) in the United States may be infected with and serve as sentinel hosts for several zoonotic vector-borne pathogens. In this study, we analyzed the geographic distribution, risk factors, and co-infections associated with infection with Ehrlichia spp., Anaplasma spp., Borrelia burgdorferi, and Dirofilaria immitis in shelter dogs in the eastern United States. Methods From 2016–2020, blood samples from 3,750 shelter dogs from 19 states were examined with IDEXX SNAP® 4Dx® Plus tests to determine prevalence of infection with tick-borne pathogens and infection with D. immitis. We assessed the impact of factors including age, sex, intact status, breed group, and location on infection using logistic regression. Results Regional variation in detection prevalence was noted: D. immitis (17.4%, n = 355/2,036) and Ehrlichia spp. (10.7%, n = 217/2,036) were highest in the Southeast while prevalence for B. burgdorferi (19.3%, n = 143/740) and Anaplasma spp. (5.7%, n = 42/740) were highest in the Northeast. Overall, 4.8% (n = 179/3,750) of dogs had co-infections, the most common of which were D. immitis/Ehrlichia spp. (1.6%, n = 59/3,750), B. burgdorferi/Anaplasma spp. (1.5%, n = 55/3,750), and B. burgdorferi/Ehrlichia spp. (1.2%, n = 46/3,750). Risk factors significantly influenced infection across the evaluated pathogens were location and breed group. All evaluated risk factors were significant for the prevalence of D. immitis antigens. Conclusions Our results demonstrate a regionally variable risk of infection with vector-borne pathogens in shelter dogs throughout the eastern United States, likely due to varying distributions of vectors. However, as many vectors are undergoing range expansions or other changes in distribution associated with climate and landscape change, continued vector-borne pathogen surveillance is important for maintaining reliable risk assessment.