Relapsing fever group Borrelia(RFGB) are motile spirochetes transmitted to mammalian or avian hosts through the bite of hematophagous arthropods, such as soft ticks (Argasidae), hard ticks (Ixodidae) and the human clothing lice. RFGB can infect pets such as dogs and cats, as well as birds, cattle and humans.Borrelia recurrentis,B. anserinaandB. theileriare considered to have worldwide distribution, affecting humans, domestic birds and ruminants, respectively.Borreliaspp. associated with soft ticks are transmitted mainly byOrnithodorosticks and thrive in endemic foci in tropical and subtropical latitudes. Nowadays, human cases of soft tick-borne relapsing fever remain neglected diseases in several countries, and the impact these spirochetes have on the health of wild and domestic animals is largely understudied. Human infection with RFGB is difficult to diagnose, given the lack of distinguishing clinical features (undifferentiated febrile illness). Clinically, soft tick or louse-borne relapsing fever is often confused with other etiologies, such as malaria, typhoid or dengue. In Latin America, during the first half of the twentieth century historical documents elaborated by enlightened physicians were seminal, and resulted in the identification of RFGB and their associated vectors in countries such as Mexico, Panama, Colombia, Venezuela, Peru and Argentina. Almost 80 years later, research on relapsing fever spirochetes is emerging once again in Latin America, with molecular characterizations and isolations of novel RFGB members in Panama, Bolivia, Brazil and Chile. In this review we summarize historical aspects of RFGB in Latin America and provide an update on the current scenario regarding these pathogens in the region. To accomplish this, we conducted an exhaustive search of all the published literature for the region, including old medical theses deposited in libraries of medical academies. RFGB were once common pathogens in Latin America, and although unnoticed for many years, they are currently the focus of interest among the scientific community. A One Health perspective should be adopted to tackle the diseases caused by RFGB, since these spirochetes have never disappeared and the maladies they cause may be confused with etiologies with similar symptoms that prevail in the region.Graphical Abstract

The global burden of arboviral diseases continues to rise with alarming frequency and impact

In Colombia, tropical febrile illnesses represent one of the most important causes of clinical attention. Febrile illnesses in the tropics are mainly zoonotic and have a broad etiology. The Colombian surveillance system monitors some notifiable diseases. However, several etiologies are not monitored by this system. In the present review, we describe eleven different etiologies of zoonotic tropical febrile illnesses that are not monitored by the Colombian surveillance system but have scientific, historical, and contemporary data that confirm or suggest their presence in different regions of the country: Anaplasma, Arenavirus, Bartonella, relapsing fever group Borrelia, Coxiella burnetii, Ehrlichia, Hantavirus, Mayaro virus, Orientia, Oropouche virus, and Rickettsia. These could generate a risk for the local population, travelers, and immigrants, due to which they should be included in the mandatory notification system, considering their importance for Colombian public health.

Leptospirosis is caused by pathogenic Leptospira spp., which can be found in nature among domestic and wild animals. In Colombia, the Macaregua cave is known for its bat richness; thus, because bats are reservoir hosts of human microbiological pathogens, we determined if the Macaregua cave bats harbored Leptospira in the wild. A total of 85 kidney samples were collected from three bat species (Carollia perspicillata, Mormoops megalophylla, and Natalus tumidirostris) to detect Leptospira spp. The 16S rRNA gene was targeted through conventional PCR and qPCR; in addition, the LipL32 gene was detected using conventional PCR. Obtained amplicons were purified and sequenced for phylogenetic analysis. The Leptospira spp. 16S rRNA gene was detected in 51.8% bat kidneys, of which 35 sequences were obtained, all clustering within the pathogenic group. Moreover, 11 sequences presented high-identity-values with Leptospiranoguchii, Leptospiraalexanderi, Leptospiraborgpetersenii, Leptospirakirschneri, and Leptospiramayottensis. From the 16S rRNALeptospira spp.-positive population samples, 28 amplified for the LipL32 gene, and 23 sequences clustered in five different phylogenetic groups. In conclusion, we detected the circulation of different groups of Leptospira spp. sequences among cave bats in the wild; some sequences were detected in more than one bat specimen from the same species, suggesting a conspecific transmission within the cave.

Acute undifferentiated febrile illness (AUFI) is one of the leading causes of illness in tropical regions. Although malaria is the most important cause, other pathogens such as Dengue (DENV), Leptospira and recently, Coronavirus Disease 2019 (COVID-19) have gained importance. In Colombia, few studies aimed to identify the etiology of AUFI. Most of them performed in Apartadó and Villeta municipalities, identifying the active circulation of several pathogens. Thus, we conducted a cross-sectional study in these municipalities to characterize the etiologies of AUFI during COVID-19 pandemic. An active surveillance was conducted between September and December 2021 in local hospitals of Apartadó and Villeta municipalities. Febrile patients were enrolled after voluntarily agreeing to participate in the study. Ten different etiologies were evaluated through direct, serological, molecular and rapid diagnostic methods. In Apartadó a confirmed etiology was found in 60% of subjects, DENV (25%) being the most frequent, followed by leptospirosis (16.7%), malaria (10%), COVID-19 (8.3%), spotted fever group (SFG) rickettsiosis (6.7%) and Chikungunya (1.7%). In Villeta, a specific etiology was confirmed in 55.4% of patients, of which SFG rickettsiosis (39.3%) was the most frequent, followed by leptospirosis (21.4%), DENV (3.6%) and malaria (1.8%). No cases due to Mayaro, Yellow Fever, Oropouche and Venezuelan Equine Encephalitis viruses were detected. We confirm the relevance of dengue fever, leptospirosis, SFG rickettsiosis, COVID-19 and malaria as causes of AUFI in the municipality of Apartadó, and highlight the great importance of SFG rickettsiosis as the main cause of AUFI in the municipality of Villeta.