Rickettsiae of the spotted fever group in dogs of the Americas: A systematic review and meta-analysis.

Sentinel animals are defined as sensitive indicators of environmental hazards that provide an early warning system for public health interventions. Spotted fever group rickettsioses are zoonotic tick-borne diseases that are considered endemic in different American countries with significant rates of morbidity and lethality, mainly when involving species such as Rickettsia rickettsii and Rickettsia parkeri. Dogs have been recognized as good sentinels for these rickettsioses, since they are hosts to different species and stages of ticks, and they sustain a good immunological response after infection. Data from epidemiological studies conducted on dogs in the Americas are dispersed and have not been integrated. In this paper, we present a systematic review and meta-analysis that aimed to present a pooled seroprevalence of Rickettsia sp. in dogs and summarize other relevant data. Literature was reviewed in three databases (PubMed, Scopus, and Web of Science) by different authors, using specific eligibility criteria, and subsequently submitted for meta-analysis to obtain pooled seroprevalences for Rickettsia spp. and different Rickettsia antigens. The systematic search yielded 700 documents, and 49 were selected for review and analysis (years: 2001-2025). Brazil (59.2%) was the country with the highest number of published studies. The Indirect Immunofluorescence Assay (IFA) was used as the main technique with R. rickettsii and R. parkeri as the main antigens used. The estimated overall seroprevalence for Rickettsia sp. was 26.2% (95% CI: 17.8% - 36.8%), with the highest values for R. rickettsii (16.9%, 95% CI: 9.8% - 27.4%), followed by R. parkeri (13.2%, 95% CI: 6.9% - 23.6%). The most frequent tick species collected on dogs were Amblyomma ovale and Rhipicephalus sanguineus s.l. This study confirms the important eco-epidemiological role of dogs as sentinels of rickettsioses. Although this has been studied in some countries, several American countries have not yet addressed it. This could be improved by strengthening surveillance programs focused on rickettsial pathogens that include dogs as sentinels, prioritizing these diseases as relevant zoonoses within a One Health framework.