8 - Unearthing Spotted Fever Group Rickettsiosis (SFGR) Foci in Central America

Abstract: Spotted Fever Group Rickettsioses (SFGR) are a group of diseases caused by tick-borne pathogens that are commonly underdiagnosed and underreported in the Central American region, and thus, are classified as neglected bacterial pathogens. The most important species in this group is the causative agent for Rocky Mountain Spotted Fever, Rickettsia rickettsii. Little SFGR research is conducted in Central American countries with higher human poverty and reduced human development—like El Salvador. No pathogenic Rickettsia spp. have been reported in this country. Leveraging a collaboration with the University of El Salvador, we collected ticks from various locations in El Salvador to determine prevalence of pathogenic Rickettsia and tested bio-banked pediatric samples for antibodies to SFGR bacteria. Ticks were collected from two agricultural farms and one veterinary practice, identified to species, and tested for pathogens. Standard and quantitative PCR were used to detect presence of SFGR, Ehrlichia, and Anaplasma spp. pathogens in ticks. Further confirmation of pathogen species was accomplished through DNA sequencing. Commercially available IgG and IgM ELISA assays were conducted to detect antibodies to SFGR bacteria on approximately 1,000 bio-banked pediatric serum samples. Of the approximate 250 collected ticks, Ehrlichia spp. amplified in 2.4%, Anaplasma spp. in 5.5%, and Rickettsia rickettsii in 18.2% of ticks. In total, 7 pathogenic bacterial species were confirmed circulating within local ticks. Combined seroprevalence for SFGR antibodies in the pediatric cohort was 13%, indicating undiagnosed tick-borne disease in a higher-risk population. This is the first report of R. rickettsii and the third report of seropositivity to SFGR bacteria in over 25 years in El Salvador. This is concerning for public health in a country where tick and tick-borne disease surveillance is not conducted. Our study emphasizes the need for further surveillance and research to understand the public health burden in this country.