Seroprevalence of Rickettsia Spp. and Orientia tsutsugamushi in Indigenous Populations from the Sierra Nevada de Santa Marta, Colombia.

Background: Rickettsia spp. are vector-borne zoonotic pathogens that cause febrile illness in humans. Rickettsioses is not included in the Colombian national surveillance system and is subsequently expected to be underreported. This cross-sectional study aimed to determine the seroprevalence of Rickettsia spp. and the closely related Orientia tsutsugamushi in two indigenous populations residing in the Sierra Nevada de Santa Marta, Colombia. Materials and Methods: Serum samples (n = 539) were collected from the Wiwa and Koguis people between 2021 and 2022. Serum samples were screened for spotted fever group (SFG) and typhus group (TG) Rickettsia spp. using the Fuller laboratories Rickettsia IgG IFA kit and for O. tsutsugamushi with the Scrub Typhus Detect™ IgG ELISA. Results: We observed an overall seroprevalence of 26.2% (95% confidence interval [CI] 22.5-30.1] for Rickettsia spp. of the SFG, 5.4% (95% CI 3.6-7.6) for Rickettsia spp. of the TG and 4.3% (95% CI 2.7-6.3) for O. tsutsugamushi. Common risk factors for zoonotic disease infections were assessed for 147 of the Wiwa participants. Increased odds of seropositivity for SFG Rickettsia spp. were observed for Wiwa participants who cared for livestock, including assisting with the birth of cattle (odds ratio [OR] = 8.85; 95% CI 1.54-50.90; p = 0.015) and goats (OR = 7.60; 95% CI 1.70-33.90; p = 0.008). Conclusions: These results highlight a notable exposure to Rickettsia spp., especially the SFG, in rural Colombia. Together with recent reports of high mortality for Rocky Mountain Spotted Fever in nearby regions of South America, more detailed investigations focusing on improving knowledge and awareness as well as "One Health" and "causes-of-fever" studies are needed. The characterization of Rickettsia spp. infections in humans, livestock, and tick vectors with their potential transmission routes could make a high impact on these easily treatable diseases.

Identification of trombiculid mites (Acari: Trombiculidae) on rodents from Chiloé Island and molecular evidence of infection with Orientia species.

BACKGROUND: Scrub typhus is an emerging vector-borne zoonosis, caused by Orientia spp. and transmitted by larvae of trombiculid mites, called chiggers. It mainly occurs within a region of the Asia-Pacific called the tsutsugamushi triangle, where rodents are known as the most relevant hosts for the trombiculid vector. However, the reservoir(s) and vector(s) of the scrub typhus outside Asia-Pacific are unknown. The disease has recently been discovered on and is considered endemic for Chiloé Island in southern Chile. The aim of the present work was to detect and determine the prevalence of chiggers on different rodent species captured in probable sites for the transmission of orientiae responsible for scrub typhus on Chiloé Island in southern Chile and to molecularly examine collected chiggers for the presence of Orientia DNA. METHODOLOGY/PRINCIPAL FINDINGS: During the austral summer 2018, rodents were live-trapped in six sites and examined for chigger infestation. All study sites were rural areas on Chiloé Island, previously identified as probable localities where human cases acquired the scrub typhus. During a total of 4,713 trap-nights, 244 rodents of seven species were captured: the most abundant was Abrothrix olivacea. Chiggers were detected on all seven rodent species with a 55% prevalence rate. Chiggers showed low host specificity and varied according to site specific host abundance. Three genera of trombiculids were identified. Herpetacarus was the most abundant genus (93%), prevalent in five of the six sites. Infestation rates showed site specific differences, which were statistically significant using a GLM model with binomial errors. Molecular analyses proved that 21 of 133 (15.8%) mite pools were positive for Orientia species, all of them belonged to the genus Herpetacarus. CONCLUSIONS/SIGNIFICANCE: This study firstly reports the presence of different rodent-associated chigger mites positive for Orientia sp., in a region endemic for scrub typhus in southern Chile. Herpetacarus and two other genera of mites were found with high infestation rates of rodents in sites previously identified as probable exposure of scrub typhus cases. A substantial percentage of mite pools were positive for Orientia DNA, suggesting that chigger mites serve as vectors and reservoirs of this emerging zoonosis in South America.

Endemic Scrub Typhus in South America.

Scrub typhus is a life-threatening zoonosis caused by Orientia tsutsugamushi organisms that are transmitted by the larvae of trombiculid mites. Endemic scrub typhus was originally thought to be confined to the so called "tsutsugamushi triangle" within the Asia-Pacific region. In 2006, however, two individual cases were detected in the Middle East and South America, which suggested that the pathogen was present farther afield. Here, we report three autochthonous cases of scrub typhus caused by O. tsutsugamushi acquired on Chiloé Island in southern Chile, which suggests the existence of an endemic focus in South America. (Funded by the Chilean Comisión Nacional de Investigación Científica y Tecnológica and the Wellcome Trust.).

Endemic scrub typhus-like illness, Chile.

We report a case of scrub typhus in a 54-year-old man who was bitten by several terrestrial leeches during a trip to Chiloé Island in southern Chile in 2006. A molecular sample, identified as related to Orientia tsutsugamushi based on the sequence of the16S rRNA gene, was obtained from a biopsy specimen of the eschar on the patient's leg. Serologic analysis showed immunoglobulin G conversion against O. tsutsugamushi whole cell antigen. This case and its associated molecular analyses suggest that an Orientia-like agent is present in the Western Hemisphere that can produce scrub typhus-like illness. The molecular analysis suggests that the infectious agent is closely related, although not identical, to members of the Orientia sp. from Asia.