Memorias do Instituto Oswaldo Cruz最新文献

Background: Chagas disease (CD) is a vector-borne infection caused by Trypanosoma cruzi, a kinetoplastid parasite of mammals. T. cruzi is transmitted by triatomine bugs throughout the Americas and some Caribbean islands. On the Caribbean island of Trinidad, T. cruzi has been isolated from triatomine bugs in several residential areas where dogs are a common pet. However, canine T. cruzi infection in Trinidad has never been studied.

Objectives: We aimed to demonstrate that canine CD does occur in Trinidad through a review of veterinary records from the years 2008-2023.

Methods: We reviewed 3,923 case reports from Trinidad veterinary clinics for canine Chagas cases diagnosed through histological evaluation, necropsy, blood smear evaluation, and/or polymerase chain reactions (PCR).

Findings: We identified 13 confirmed and two suspected canine CD cases. Animal ages ranged from five weeks to 14 years old, with four (27%) being less than one year old, including the pup of a T. cruzi-infected dam. Breed varied, although one-third (5/15) were hounds. Clinical signs ranged from asymptomatic (43%; 6/14) to severely ill with limb paresis (21%; 3/14). Seven of the fifteen (47%) dogs died, and three more (20%) were euthanized. Myocarditis with visible amastigote forms were found in two-thirds (9/15) of dogs.

Main conclusions: Our findings highlight a need for increased awareness of CD among dog owners and veterinarians in Trinidad.

Background: Mosquitoes (Diptera: Culicidae) are among the most important disease vectors worldwide. Several species exhibit high levels of anthropophily and are frequently found in human dwellings and forest fragments near urban areas.

Objectives: In this integrative study combining mosquito collection, viral detection, and ecological analyses, the assemblage of diurnal mosquitoes was investigated across three distinct environments - intradomiciles, and two distinct urban forest fragments (UFFs) - during a dengue outbreak in the city of Salinas, Minas Gerais, Brazil.

Methods: Sampled mosquitoes were tested for the presence of dengue, Zika, and chikungunya viruses through real-time quantitative polymerase chain reaction (RT-qPCR).

Findings: A total of 722 mosquitoes were collected, representing seven genera and 12 species. The most abundant species were Culex quinquefasciatus (270/722, 37.4%), Aedes aegypti (205/722, 28.4%), Ae. albopictus (112/722, 15.5%), and Ae. scapularis (110/722, 15.2%). Five of 81 pools tested positive for dengue virus serotype 1 (DENV-1) RNA, all belonging to Ae. aegypti species. Phylogenetic analyses of the nearly complete genome of DENV-1 revealed clustering with strains sampled in 2023 from São Paulo State. Mosquito richness and composition differed between environments (houses and urban forests), whereas abundance was similar across all environments.

Main conclusions: Important vector species were detected, including Ae. aegypti, Ae. albopictus, Cx. quinquefasciatus, Ae. scapularis, Sabethes albiprivus, and Coquillettidia venezuelensis, associated with the transmission of dengue, oropouche, mayaro, yellow fever, and Venezuelan equine encephalitis viruses. Entomological and virological investigations in urban and peri-urban environments are crucial, as these areas provide shelter and refuge for anthropophilic and opportunistic mosquito species. Our findings underscore a high potential for mosquito-borne disease spillover in these areas.

Background: Narrow-spectrum antibiotics, such as narrow-spectrum β-lactams, have been pointed out as an efficient strategy to mitigate resistance and reach successful outcomes in treating enterobacterial infections. The narrow-spectrum class A β-lactamase LAP-2, conferring resistance to narrow-spectrum cephalosporins/penicillin derivatives, is spread among Enterobacteriaceae from Asia but is rarely reported in the Americas. Due to the lack of information concerning the bla LAP-2 genetic background involved with its dissemination, this study determined the bla LAP-2 genomic environment and contextualised the LAP-2-positive Klebsiella pneumoniae strains from Brazil in the current epidemiological scenario.

Objectives: This study characterised LAP-2-positive K. pneumoniae strains, focusing on their genetic environment and epidemiology.

Methods: Whole-genome sequencing and in silico analyses were performed to identify the genetic context of bla LAP-2 in five clinical isolates from Brazil. Comparative genomics and phylogenomic analysis were conducted to investigate the transmission dynamics of bla LAP-2 globally.

Findings: The bla LAP-2 gene was embedded in a conserved genetic module (IS3-bla LAP-2-ftsI), facilitating its dissemination among diverse Enterobacteriaceae species. The Brazilian strains harboured bla LAP-2 within a pXJ-K2 variant plasmid, a key vector in LAP-2 spread. Phylogenomic analysis revealed that, in Brazil, bla LAP-2 was carried by an ST11 K. pneumoniae lineage distinct from the Chinese lineage but globally disseminated.

Main conclusions: This study provides insights into the epidemiology and transmission dynamics of bla LAP-2, revealing its silent spread via plasmid transfer and clonal expansion of ST11 lineages. The high transmission potential of bla LAP-2 may compromise the application of narrow-spectrum β-lactams as a viable treatment option for enterobacteria-causing infections.

Background: The biological diagnosis of imported malaria cases is a challenge that requires efficient methods, trained staff and high-quality proficiency. Microscopy, rapid diagnosis tests and molecular tests are widely available and provide excellent results. New methods such using haematology analysers have been recently developed.

Objectives: In the context of limited resources, a complete cost-effectiveness analysis of the different scenarios should aid in the decision-making process for the most appropriate methods.

Methods: The full cost-effectiveness of each malaria diagnosis scenario relative to the clinical benefits of the outcome was measured. The study population was a cohort of patients who were receiving health care at Lyon University Hospital for suspected malaria during 2023. Four scenarios were tested: microscopy, rapid diagnosis test + microscopy combination, loop-mediated isothermal amplification (LAMP) + microscopy combination, all identified as the control tests, and haematology analyser XN-31 + microscopy combination, identified as the intervention. The direct costs were calculated based on prices paid in France for material and consumables needed to perform malaria diagnosis for one sample among 1000 tests per year. The indirect cost of technical training, supervision and quality proficiency was calculated based on the hourly salary of the laboratory technician, junior and senior doctors according to the time needed for each scenario.

Findings: This approach provides a global approach for determining the cost-effectiveness of the most frequent scenarios for diagnosing malaria. The diagnosis accuracy and the short time-to-result of the haematology analyser combined with microscopy were the key points of the cost-effectiveness result.

Main conclusion: The generalisability of our findings is restricted by the specificity of the costs observed in France and the limited panel of methods tested. However, this may promote similar studies from other countries to document the cost-effectiveness of the different scenarios used for malaria diagnosis.

Background: Mosquitoes are critical vectors in tropical regions where arboviruses like dengue and Zika are prevalent. This study focuses on characterising the RNA virome of mosquitoes in the Colombian Caribbean, emphasising the core regional virome and its role in the dynamics of arboviruses.

Objectives: The objective was to identify and analyse the core RNA virome of mosquitoes across different genera and seasons in the Colombian Caribbean to understand its composition and potential influence on arbovirus transmission dynamics.

Methods: In 2023, 4,074 mosquitoes from the genera Mansonia, Coquillettidia, and Anopheles were collected across Córdoba, Sucre, Bolívar, and Magdalena during rainy and dry seasons. Specimens were pooled in groups of 50, subjected to RNA extraction, and sequenced on the MGI-G50™ platform. Bioinformatic analyses utilised the DIAMOND-MEGANizer pipeline and R packages (phyloseq, vegan, ggplot2) to identify viral communities.

Findings: The analysis identified 22 viral families and 24 unclassified RNA viruses. The core regional virome, consistently present across species and seasons, was dominated by insect-specific viruses (ISVs) such as Aedes aegypti to virus 1 and 2, Astopletus, and Cumbaru, alongside Picornaviridae (30% of reads), Rhabdoviridae (20%), Orthomyxoviridae, and Bunyavirales. Mansonia titillans (38 species) and Coquillettidia nigricans (21 species) exhibited the highest viral richness. No significant arboviruses were detected, highlighting ISV dominance. Virome composition varied seasonally, with greater diversity in the rainy season due to increased breeding site availability and temperature.

Main conclusions: The stability of the core virome suggests it modulates vector competence, potentially reducing arbovirus transmission. These findings advocate the use of metagenomics for enhanced vector surveillance and biological control strategies in neotropical ecosystems.

Background: Trypanosomatid infections such as Chagas disease (CD) and leishmaniasis remain major public-health concerns. Brazil has a long tradition in this field, yet a consolidated, country-level view of outputs, impact and collaboration patterns is useful to guide scientific policy.

Objectives: To characterise Brazilian scientific production on Trypanosoma cruzi, Leishmania and Trypanosoma brucei (2010-2021), describing temporal trends, regional contributions, collaboration networks and journal impact.

Methods: We performed a bibliometric analysis of PubMed records retrieved with Medical Subject Headings (MeSH) for each pathogen/disease pair, covering publications from 1 January 2010 to 31 December 2021 (search date: 21 July 2022). Data items included article type, year, journal, author affiliations (countries/institutions) and, for Brazil, the geographical region of the corresponding author. Descriptive statistics and visualisations were generated in R.

Findings: From 21,713 records, 6,478 were affiliated to Brazil. Brazil contributed a substantial share of the global literature, particularly for T. cruzi (≈40%) and Leishmania (≈30%). Within Brazil, output increased over time with growing participation from the north and northeast, alongside expanding inter-institutional and international collaborations. Most publications appeared in higher-impact journals (Q1/Q2), with recent gains in Q1 outputs in historically under-represented regions. Original research predominated over reviews across the period.

Main conclusions: Brazilian trypanosomatid research shows sustained growth, increasing regional dispersion and rising international engagement, with a strong presence in high-impact journals. Continued support for collaborative networks and equitable funding across regions could further enhance national and global impact.

Background: We present a simplified freeze-fracture method to reveal the internal structure of protozoan parasites and their host cells, without the need for costly transmission electron microscopy (TEM) equipment. In a traditional procedure, the four key steps in making a freeze-fracture replica are (1) freezing, (2) fracturing, (3) replication, and (4) replica cleaning. In conventional protocols, visualisation is performed using a TEM.

Objectives: This study aimed to adapt the traditional freeze-fracture protocol to a more accessible method, eliminating the need for vacuum equipment and TEM, while preserving the capacity to visualise cellular structures.

Methods: In our adapted method, vacuum equipment was not required for sample fracturing, shadowing, or replica preparation. Cells were fixed with glutaraldehyde, embedded in a gelatin-chitosan matrix, cryoprotected with dimethyl sulfoxide (DMSO), and subsequently frozen in Freon, followed by immersion in liquid nitrogen. We manually break the cells with a previously frozen razor blade and macerate them with osmium tetroxide (OsO4). The samples are visualised using scanning electron microscopy (SEM).

Findings: We present various structures of Toxoplasma gondii, Trypanosoma cruzi, Trichomonas vaginalis, Giardia intestinalis, and cultured cells observed using our adapted freeze-fracture method.

Main conclusions: This is a rapid and low-cost technique that reveals cell structures comparable to those observed using traditional freeze-fracture methods, although with reduced resolution.

Background: The conformation of the Sordida subcomplex has been a topic of prolonged debate, with diverse methodological approaches employed to discern its constituent species. Up to now, Triatoma sordida, T. garciabesi and T. rosai comprise part of this subcomplex. Distinguishing and identifying these three species pose significant challenges due to their pronounced morphological similarity, overlapping distributions, and presence of natural hybrids.

Objectives: This study aims to uncover the genetic diversity and geographic spread of these three species.

Methods: We analysed a mitochondrial cytochrome b gene fragment and complemented it with chromosomal studies across natural populations from an extensive geographical range, including Argentina, Bolivia, Brazil, and Paraguay.

Findings: Phylogenetic analyses revealed genetic distances that suggest the presence of at least six putative species, rather than the three currently recognised.

Main conclusions: The present findings underscore the potency and significance of molecular analyses from natural populations for species identification and highlight the limitations of morphology in classifying Triatominae species.

Background: Parasitic diseases may increase the risk of metabolic abnormalities through persistent inflammation. However, the effects of a hyperglycaemic diet during Trypanosoma cruzi infection remain poorly understood.

Objectives: This study aimed to investigate the metabolic, parasitological, immunological, and histological effects of a hyperglycaemic diet during acute T. cruzi infection in mice.

Methods: C57BL/6 mice were divided into four groups: non-infected with standard diet (NISD), infected with a standard diet (ISD), non-infected with hyperglycaemic diet (NIHD), and infected with hyperglycaemic diet (IHD). Animals were fed their respective diets for eight weeks prior to infection and monitored up to 30 days post-infection (DPI) for blood glucose, body mass, biochemical markers, parasitaemia, tissue alterations, and immune cell profiles.

Findings: At the time of infection, hyperglycaemic diet groups showed higher blood glucose and body mass. By 30 DPI, these animals exhibited lower glucose, increased parasitaemia, adipose tissue hypertrophy, and reduced cholesterol levels compared with controls. Infected groups showed an increased CD4+ IFN-γ+ T cells at 10 DPI, whereas macrophage expansion was observed only in ISD mice. Cardiac parasitism was higher at 30 DPI than at 10 DPI.

Main conclusions: These results show that T. cruzi infection affects metabolic parameters and that a hyperglycaemic diet worsens parasitological outcomes during the acute phase of infection and appears to downregulate the immune response.

Background: Infections with Ascaris lumbricoides can be traced back to the late Pleistocene by palaeoparasitological analysis. Even today, Ascaris infections are still very common worldwide.

Objectives: In a pilot study, soil samples from the pelvic area of ten individuals from the Celtic necropolis of Povegliano Veronese (northern Italy) were examined using palaeoparasitological methods. The burials date from the 3rd to 1st century Before the Common Era (BCE).

Methods: The palaeoparasitological methods already proven in earlier studies were applied.

Findings: Positive evidence of Ascaris eggs was obtained in three individuals, including a newborn. This neonate is the focus of the article. The causes of a possible Ascaris infection in a newborn are discussed.

Main conclusions: It may represent the oldest documented instance of ascariasis in a neonatal individual.