Spotted fever group rickettsiae canine serosurveillance near the US–Mexico border in California

Abstract

Background: Dogs are vulnerable to pathogens transmitted by brown dog ticks. An epidemic of Rocky Mountain spotted fever (RMSF) is underway in Mexicali, aMexican city bordering California affecting people and dogs; several human cases have been reported in California residents who travelled to Mexico. To evaluate risks of RMSF, we conducted seroprevalence surveys in Imperial County in 2016 and 2017 using dogs as sentinels.Methods: Blood was collected from 752 dogs and was tested for antibodies against R. rickettsii, E. canis and A. phagocytophilum (as a proxy for A. platys). Samples were considered seropositive to spotted fever group rickettsia (SFGR) if the R. rickettsia titre was ≥1:64 and seropositive to E. canis and A. phagocytophilum if the titre was ≥1:32. Owners provided information on dog age, exposure risks, health status and tick prevention. We assessed associations between SFGR seropositivity and driving distance to the nearest US-Mexico border crossing station, whether proximity to a border crossing increased likelihood of taking dogs across the border, and whether distance to the border was associated with seropositivity. Logistic regression was performed to assess relationships between the titre classes and other predictor variables.Results: 12.2% of dogs were seropositive against SFGR. Dogs close to the border were significantly more likely to be taken across the border and to be seropositive.Risk factors that increased seropositivity included owners seeing ticks on the dog (OR = 1.9), being an adult dog, travel to Mexico (OR = 3.0) and living in a rural area (OR = 4.0). There was statistically significant co-exposure to SFGR and Anaplasma spp. Conclusion: Surveillance for brown dog tick-vectored pathogens can help identify dogs and people at risk for RMSF. Tick prevention, particularly in dogs, and surveillance of tick-borne pathogens can help prevent the spread of rickettsioses and other diseases in this dynamic border region. K E Y W O R D S border disease, canine sentinel, Rocky Mountain spotted fever | 149 ESTRADA ET Al.

An exploratory analysis of demography and movement patterns of dogs: New insights in the ecology of endemic Rocky Mountain-Spotted Fever in Mexicali, Mexico

“…Although our findings suggest that dog reproductive performance and turnover are important factors affecting the transmission of RMSF in Mexicali, it is probable that the epidemiological dynamics of the diseases are also influenced by other indirect and direct, multifactorial factors including socioeconomic, biological, and environmental factors at different temporal and spatial scales [13,18,21,46]. For instance, although this study focused on owned freeroaming dogs, dogs of unknown ownership were often observed by study participants, and https://doi.org/10.1371/journal.pone.0233567.g005…”

“…Since 2008, an outbreak of RMSF is ongoing in Mexicali, a city of 700,000 people immediately south of the border with the US, affecting at least 1000 people and countless dogs, with a high human mortality rate of approximately 40% [16]. In Mexico, the vector is a distinct tropical lineage of brown dog tick, in contrast with epidemics in Arizona associated with the temperate lineage [17]; increased warming and drying associated with climate change may permit the tropical lineage ticks to expand northward, with evidence that canine exposure is increased directly north of the US/Mexico border [18].…”

Novel Rickettsia Species Infecting Dogs, United States

“…Studies aimed at identifying the tick vector, potential animal reservoirs, and prevalence are ongoing. These 3 canine rickettsioses cases underscore the value of dogs as sentinels for emerging tickborne pathogens (13,14).…”

Possible Association between Selected Tick-Borne Pathogen Prevalence and Rhipicephalus sanguineus sensu lato Infestation in Dogs from Juarez City (Chihuahua), Northwest Mexico–US Border

“…In previous studies in Mexico, the seroprevalence of TBBPs detected in both ticks and animals was common [ 19 , 20 , 21 , 22 , 23 ], and surveys on the diversity of ticks were carried out [ 21 , 24 ]. However, this research represents the first systematic study performed at the Mexico–US border, where the co-infestation with R. sanguineus s. l. and O. megnini , naturally parasitizing domestic dogs and FRD, the prevalence of TBBPs, and the association among the infestation with R. sanguineus s. l. males and E. canis infection in dogs were identified.…”