Focus on brown dog tick-transmitted Rocky Mountain spotted fever in dogs and people: shared threats and solutions.

Rocky Mountain spotted fever (RMSF) kills people and dogs in rural communities throughout the Americas and in urban epidemics in Brazil and Mexico. The companion Currents in One Health by Foley et al, AJVR , March 2025, addresses the urban ecology of this devastating disease across the Americas. Cases acquired from Dermacentor spp ticks are sylvatic and sporadic, in contrast with peridomestic cases from Rhipicephalus sanguineus sensu lato, which relies on dogs as hosts. Since the early 2000s, RMSF reemerged in northern Mexico with at least 9,152 human cases and case mortality up to 50%. These cases tend to occur where people are impoverished and have marginal access to medical care. Data on RMSF in dogs are sparse, although dogs are sentinels for human risk. The presence of roaming dogs in neighborhoods is associated with human cases, canine seroprevalence, and tick abundance. Dogs and people share hematological and clinical chemical findings and results of targeted diagnostic tests. Diagnosis requires PCR confirmation or rising convalescent titers, although seropositivity can be a cross-reaction with other rickettsial organisms. Suspect cases should be treated with doxycycline immediately. Coinfection with other R sanguineus -transmitted pathogens is common. Veterinarians in clinical practice can help families manage RMSF risk with client education and provide tick preventive medication, although the considerable cost is a barrier. Veterinarians can also advise how to manage tick infestations in a home, recognizing that eradicating R. sanguineus is very difficult. To reduce roaming and canine population sizes, veterinarians should promote canine spay, neuter, and restraint to the home.