Investigation of pathogens causing tick-borne zoonoses in the Amazon Biome

Abstract

Tick-borne rickettsiosis are zoonoses caused by obligatory intracellular bacteria of the genus Rickettsia. Rocky Mountain spotted fever (FM), caused by the bacterium Rickettsia rickettsii, is the deadliest tick-borne disease with 489 deaths recorded between 2001-2018, many in the state of Sao Paulo. Despite the diversity of entomological fauna, there are no confirmed reports of FM in humans in the Amazon region. However, numerous reports point to the presence of Rickettsia amblyommatis, which is not formally described as a zoonotic agent, but has been associated with seroconversion in suspected FM cases in the US, and it is suggested that parts of these FM cases are caused by R. amblyommatis. Other tick-borne agents are relevant and poorly studied in the Amazon biome, such as Ehrlichia spp., Described as zoonosis, which mainly affects dogs and humans, and Anaplasma and Babesia species. Although the description of human infection with tick-borne pathogens is increasing worldwide, research on these agents in the Amazon is neglected, with very few studies. In contrast to this lack of studies in the Amazon is the high number of unspecific and undiagnosed febrile diseases that affect the population of the region. Recently a surprising case of nonspecific febrile illness with respiratory syndrome in humans was recently detected in the Saracá-Taquera National Forest by the project team. In this specific case, seroconversion to Rickettsia typhi without reaction to FM group rickettsia was identified. The patient had no history of contact with rats and / or fleas and the causative agent, vector and wild reservoir of this disease still remain unknown. Thus, it is possible that rickettsial infection in the region may be occurring undiagnosed, especially in remote locations near the Amazon rainforest, resulting in an important public health problem. This project aims to investigate the infection by tick-borne agents in wild animals, ticks and humans in the Amazon Biome. For this, three areas of study were selected, Curua-Una, Santarém, PA; Flona Saracá-Taquera, Oriximiná, PA; Rio Pardo, President Figueiredo, AM. Samples of wild animals and ticks will be obtained from each zone and submitted to PCR for Rickettsia spp., Anaplasma spp., Babesia spp., Ehrlichia spp. All positive PCR products will be purified and sequenced. The sequences obtained are edited and subjected to similarity analysis with the sequences available in GenBank (BLAST analysis). Human serum samples will be obtained at each study site through a prospective cross-sectional study with an epidemiological questionnaire. Sera will be tested for individual antibody titer determination for R. rickettsii, R. bellii, R. parkeri, R. felis, R. rhipicephali, R. amblyommatis and R. typhi. The different results will be analyzed in relation to the specific epidemiological determinants. This project is expected to better understand the epidemiology of tick-borne diseases in the Amazon and to identify the species of Rickettsia sp. disease in humans in the region, as well as study their potential vectors and wild reservoirs. (AU)