Seroprevalence of Rickettsia rickettsii and Rickettsia parkeri in dogs during a Brazilian Spotted Fever outbreak in the State of Rio de Janeiro

Abstract

The present paper is the first to perform this evaluation in dogs from the cities of Natividade, Porciuncula and Varre-Sai. The aim of this study is to search for Spotted Fever Group Rickettsia in canine sera using indirect immunofluorescence assay and to identify the probable causative agent of sera reactions in animals. Of the 253 sampled canines, 67.59% (171/253) were seroreactive for Rickettsia rickettsii and 11.07% (28/253) for Rickettsia parkeri, both in dilution 1:64. Titration of tested sera against R. rickettsii antigens reached 1:131.072 and, for R. parkeri, 1:4.096. We conclude that dogs are important sentinels for R. rickettsii infection, and can be infected regardless of sex, age, the habit of visiting woodlands or being in direct contact with equines and capybaras. Serological diagnosis has highlighted many dogs infected by R. rickettsii, and ambient conditions, such as the presence of flowing water bodies, was important for the occurrence of Brazilian Spotted Fever in the northwestern of Rio de Janeiro State.

Rickettsial pathogens circulating in urban districts of Rio de Janeiro, without report of human Brazilian Spotted Fever

“…In accordance with a prior study on BSF outbreaks in urban areas (Poubel et al, 2018), sex and age were not relevant in anti-R. rickettsii seroreactivity in our study ( Table 1). Other studies have shown that the frequency of IFA reactivity was higher among adult dogs than puppies (Cordeiro et al, 2015;Campos et al, 2017).…”

“…For example, Gazeta et al (2009) found a 58.7% reactivity rate against R. rickettsii in dogs from rural areas of southern Rio de Janeiro, and Poubel et al 2018found a 67.6% reactivity rate against R. rickettsii in urban dogs of northwestern Rio de Janeiro. Although both our study and that of Poubel et al (2018) were carried out in urban regions, these studies differ epidemiologically. The latter was performed during a human outbreak of BSF, accounting for the markedly high presence of seroreactive dogs.…”

“…In Brazil, its vectorial competence has not yet been definitively proven, although supporting evidence exists (Cunha et al, 2009). Dogs that live close to both humans and the ticks that act as vectors of BSF are useful sentinels of the disease (Cardoso et al, 2006;Cunha et al, 2014;Poubel et al, 2018). Therefore, to improve the monitoring and to combat of rickettsioses, it is helpful to seek evidence of prior exposure in such dogs to SFG agents by using Indirect Immunofluorescence Assay (IFA) (Campos et al, 2016).…”

“…Therefore, to improve the monitoring and to combat of rickettsioses, it is helpful to seek evidence of prior exposure in such dogs to SFG agents by using Indirect Immunofluorescence Assay (IFA) (Campos et al, 2016). Serological studies in dogs show that rickettsial dispersions in Rio de Janeiro State are concentrated in rural areas of the southern or northwestern regions, where human BSF has been reported (Gazeta et al, 2009;Cunha et al, 2014;Poubel et al, 2018). Few studies have been conducted in other regions of Rio de Janeiro, especially the metropolitan area (Cordeiro et al, 2015).…”

Spotted fever group rickettsial infection in dogs and their ticks from domestic–wildlife interface areas in southeastern Brazil

“…Based on the presence of antibodies (exposure), dogs have been recognized as sentinels for BSF, presenting strong serological evidence of bacterial circulation (Poubel et al, 2018); however, the molecular detection of R. rickettsii in dogs' blood samples is still considered very rare. The discrepancy between the amount of serological and molecular studies, in which dogs show the presence of rickettsial DNA in the bloodstream (rickettsemia), may be related to the fact that bacteria circulate in the blood for a brief period before they invade endothelial cells, or after being released back into the blood due to the disruption of infected cells.…”