Biology subjects

Barragan, V.

Publications and source records attributed to Barragan, V..

3 recordsLinked to original sources

bioRxiv2024

Host population structure and rare dispersal events drive leptospirosis transmission patterns among Rattus norvegicus in Boston, Massachusetts, US

Leptospirosis (caused by pathogenic bacteria in the genus Leptospira) is prevalent worldwide but more common in tropical and subtropical regions. Transmission can occur following direct exposure to infected urine from reservoir hosts, such as rats, or a urine-contaminated environment, which then can serve as an infection source for additional rats and other mammals, including humans. The brown rat, Rattus norvegicus, is an important reservoir of leptospirosis in urban settings. We investigated leptospirosis among brown rats in Boston, Massachusetts and hypothesized that rat dispersal in this urban setting influences the movement, persistence, and diversity of Leptospira. We analyzed DNA from 328 rat kidney samples collected from 17 sites in Boston over a seven-year period (2016-2022); 59 rats representing 12 of 17 sites were positive for Leptospira. We used 21 neutral microsatellite loci to genotype 311 rats and utilized the resulting data to investigate genetic connectivity among sampling sites. We generated whole genome sequences for 28 Leptospira isolates obtained from frozen and fresh tissue from some of the 59 Leptospira-positive rat kidneys. When isolates were not obtained, we attempted Leptospira genomic DNA capture and enrichment, which yielded 14 additional Leptospira genomes from rats. We also generated an enriched Leptospira genome from a 2018 human case in Boston. We found evidence of high genetic structure and limited dispersal among rat populations that is likely influenced by major roads and/or other unknown dispersal barriers, resulting in distinct rat population groups within the city; at certain sites these groups persisted for multiple years. We identified multiple distinct phylogenetic clades of L. interrogans among rats, with specific clades tightly linked to distinct rat populations. This pattern suggests L. interrogans persists in local rat populations and movement of leptospirosis in this urban rat community is driven by rat dispersal. Finally, our genomic analyses of the 2018 human leptospirosis case in Boston suggests a link to rats as the source. These findings will be useful for guiding rat control and human leptospirosis mitigation efforts in this and other urban settings.

molecular biology↗

bioRxiv2023

Domestic dogs in indigenous Amazonian communities: key players in Leptospira cycling and transmission?

BackgroundLeptospirosis is the worlds most common zoonotic disease. Mitigation and control rely on pathogen identification and understanding the roles of potential reservoirs in cycling and transmission. Underreporting and misdiagnosis obscure the magnitude of the problem and confound efforts to understand key epidemiological components. Difficulties in culturing hamper the use of serological diagnostics and delay the development of DNA detection methods. As a result, especially in complex ecosystems, we know very little about the importance of different mammalian host species in cycling and transmission to humans. Methodology/Principal FindingsWe sampled five indigenous Kichwa communities living in the Yasuni National Park in the Ecuadorian Amazon basin. Blood and urine samples from domestic dogs were collected to assess the exposure of these animals to Leptospira, and to identify the circulating species. Microscopic Agglutination Tests with a panel of 22 different serovars showed anti-leptospira antibodies in 36 sampled dogs (75%), and 10 serotypes were detected. Two DNA-based detection assays revealed pathogenic Leptospira DNA in 18 of 19 dog urine samples (94.7%). Amplicon sequencing and phylogenetic analysis of 16s rDNA and SecY genes from 15 urine samples revealed genetic diversity within two of three different Leptospira species: noguchii (n=7), santarosai (n=7), and interrogans (n=1). Conclusions/SignificanceThe high prevalence of antibodies and Leptospira DNA provides strong evidence for high rates of past and current infections. Such high prevalence has not been previously reported for dogs. These dogs live in the peridomestic environment in close contact with humans, yet they are free-ranging animals that interact with wildlife. This complex web of interactions may explain the diverse types of pathogenic Leptospira observed in this study. Our results suggest that domestic dogs are likely to play an important role in the cycling and transmission of Leptospira. Future studies in areas with complex ecoepidemiology will enable better parsing of the significance of genotypic, environmental, and host characteristics. Author SummaryPeople around the world interact with a wide range of animals, but one of the closest is the domestic dog. Dogs can be reservoirs of several zoonotic infectious diseases, including leptospirosis. The frequent ecological interactions between people, dogs and wildlife in indigenous communities living in the Amazon basin might increase the complexity of leptospirosis transmission, in comparison with what has been described for other settings. In the Amazon basin, wild animals and domestic animals may act as reservoirs of the pathogen, excreting the bacteria through their urine. In this work we analyzed serum and urine samples from dogs living with Kichwa communities from the Yasuni National Park in Ecuador. Serum samples were analyzed with MAT and urine samples with a qPCR that detect the presence of pathogenic Leptospira. Our results suggest that a high percentage of dogs are shedding the pathogen and we identified three different Leptospira species. Our serological analysis suggests the presence of ten serovars in dogs and their high exposure to Leptospira. These findings provide important insights into the epidemiology of leptospirosis in this ecosystem, suggesting that dogs are likely to play a critical role in the transmission of the disease.

microbiology↗

bioRxiv2021

Characterization of the immune resistance of SARS-CoV-2 Mu variant and the immunity induced by Mu infection

We have revealed that the SARS-CoV-2 Mu variant is highly resistant to COVID-19 convalescent sera and vaccine sera.1 However, it remains unclear how the immune resistance of the Mu variant is determined. Also, although the Mu variant is highly resistant to the sera obtained from COVID-19 convalescent during early pandemic (i.e., infected with prototypic virus) and vaccinated individuals (i.e., immunized based on prototypic virus), it was unaddressed how the convalescent sera from Mu-infected individuals function. In this study, we revealed that the two mutations in the spike protein of Mu variant, YY144-145TSN and E484K, are responsible for the potent immune resistance of Mu variant. Additionally, we showed that the convalescent sera obtained from the Mu-infected individuals can be broadly antiviral against the Mu variant as well as other SARS-CoV-2 variants of concern/interest. Our findings suggest that developing novel vaccines based on the Mu variant can be more effective against a broad range of SARS-CoV-2 variants.

microbiology↗