Spatial and risk factor analyses of vector-borne pathogens among shelter dogs in the Eastern United States

Abstract

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

Ehrlichia canis and Rickettsia conorii Infections in Shelter Dogs: Seropositivity and Implications for Public Health

“…Our results showed no difference between dogs’ age and seropositivity to the studied pathogen species. This finding is not in line with previous studies [ 24 , 60 ], which found an association between older dogs and seropositivity, as antibodies to R. conorii can remain detectable for a long period [ 61 ]. Elderly dogs have a higher likelihood of exposure throughout their lives, and dogs in suboptimal physical conditions may experience a weakened immune system, which increases the risk of infection [ 24 , 60 ].…”

“…This provides homes for animals and promotes global cooperation in animal welfare and health. Shelter animals, especially dogs, are particularly susceptible to tick infestations and the pathogens transmitted by these vectors, including E. canis and R. conorii [ 23 , 24 , 25 ]. These dogs serve as a critical reservoir for these vector-borne agents, potentially contributing to their transmission to other animals and even humans.…”

“…These dogs serve as a critical reservoir for these vector-borne agents, potentially contributing to their transmission to other animals and even humans. The confined and often overcrowded conditions within shelter environments can facilitate close contact between infected and susceptible animals, increasing the risk of disease spread [ 24 , 26 ]. Furthermore, as dogs are known to share strong bonds with humans and often become adopted into households, the potential for zoonotic transmission becomes a relevant concern.…”

Association between vector-borne pathogen seroprevalence in shelter-housed and owned dog populations in the contiguous United States of America

“…The first dataset is from the Companion Animal Parasite Council (CAPC; ( www.capcvet.org ), for which the data have been compiled from two veterinary diagnostic laboratories since 2011. Most of these dogs are under the care of a veterinarian, and are therefore assumed to be at lower risk of exposure; they are henceforth referred to as the “owned dog population.” The second is a prospective dataset of samples from shelter-housed dogs representing the high-risk population [ 14 ]. Shelter-housed dogs likely represent a mixed population in terms of the level of risk of exposure, but they are much more accessible compared to stray or feral dogs, or owned dogs that are not under the care of a veterinarian.…”

“…Higher risk populations of dogs (e.g., those in shelters or displaced by natural disasters) are hypothesized to have high prevalences of vector-borne pathogens, and the few studies that have directly compared the seroprevalence of higher risk dog populations to the seroprevalence of a lower risk population (e.g., owned and under the care of a veterinarian) support this hypothesis [ 6 – 14 ]. However, these studies were limited in scope and geographic distribution of data, which limits our ability to explore the relationship between the prevalences of vector-borne pathogens in these two groups of dogs.…”