Search Results (120)

Yellow fever remains a significant public health concern in endemic regions of South America and Africa, where periodic outbreaks continue to challenge surveillance and control efforts. Despite the widespread use of vaccines and historical YFV strains in experimental settings, there is limited information on the pathogenic behavior of contemporary wild-type isolates in animal models. To address this gap, this study aimed to develop and characterize a murine model infected with a wild-type YFV strain isolated in 2018, from Brazil’s largest sylvatic outbreak in decades. In this study, four-week-old male and female C57BL/6 IFNAR1^−/− mice were subcutaneously infected with WT YFV. Mice exhibited a nearly 50% survival rate and developed several clinical signs. Viral loads were assessed in serum and some tissues, collected either upon euthanasia of moribund animals or at the end point. YFV RNA was detected in all sampled tissues and serum. Infectious viral particles were identified in the brains of both sexes and in the testis. No statistically significant differences were observed between males and females in survival, clinical signs, or viral loads. Altogether, this study provides a robust and reproducible murine model for wild-type YFV infection, offering a valuable platform for investigating viral pathogenesis, host responses, and potential therapeutic interventions. Full article

Yellow fever (YF) is an acute and potentially fatal hemorrhagic disease caused by the Yellow Fever virus (YFV), endemic to sub-Saharan Africa and several tropical countries, including Brazil. In Brazil, the Amazon region is considered the main endemic area. YFV is maintained in a sylvatic cycle involving Neotropical primates and mosquitoes of the genera Haemagogus and Sabethes, acting as primary and secondary vectors, respectively. In March 2024, entomovirological surveillance was conducted in Santa Bárbara do Pará, Pará, Brazil. A total of 286 mosquitoes were collected, classified into 13 species across nine genera, and grouped into 33 pools. Seventeen pools were tested by RT-qPCR for Orthoflavivirus (YFV, DENV, WNV, SLEV), Alphavirus (CHIKV, MAYV), and Orthobunyavirus (OROV). YFV was detected in four Haemagogus janthinomys pools, with Ct values ranging from 22.2 to 27.9. Metagenomic sequencing confirmed the presence of YFV with assigned reads and >99% protein identity. Notably, the detection occurred without human cases or primate deaths, enabling timely vaccination of the local population. These findings confirm YFV circulation in forested areas of the Belém metropolitan region and reaffirm Hg. janthinomys as a key vector. Our study reinforces the relevance of early entomovirological surveillance and preventive strategies, such as vaccination, to mitigate yellow fever reemergence. Full article

The purpose of this study was to investigate and update the spatial distribution of Trichinella spp. in wild boars tested between 2015 and 2022 and to test the correlation of the population density of chosen animals (wild boars, red foxes (Vulpes vulpes), raccoon dogs (Nyctereutes procyonoides), and European badgers (Meles meles)) with the prevalence of Trichinella spp. in wild boars in Poland. In addition, to understand the distribution of infected animals, we sought to see if there were a correlation of Trichinella spp. infections in wild boars with land cover type. Among the wild carnivore species analyzed, only the population density of the raccoon dog (Nyctereutes procyonoides)—an invasive alien species—was significantly associated with infection rates in wild boars, particularly at the regional scale. As scavengers and competent reservoir hosts for all four European Trichinella species, raccoon dogs are likely to play a key role in the sylvatic transmission cycle. The positive rate of Trichinella spp. infection in wild boars during 2015–2022 was 0.22%, compared to 0.3% in 2009–2016. Moreover, forest density was positively correlated with infection rates, underlining the role of forest habitats in sustaining Trichinella transmission. Full article

Between 2016 and 2018, the state of Minas Gerais, Brazil, experienced its most significant yellow fever (YF) outbreak in 80 years. Yellow fever virus (YFV) circulation persisted afterward, with continued non-human primate (NHP) epizootics and, recently, human cases. In June 2024, YFV RNA was detected in a dead marmoset (Callithrix penicillata) in an urban square in Belo Horizonte (BH), prompting a field investigation in an adjacent park to assess infection in potential mosquito vectors and NHPs. A total of 250 mosquitoes representing nine species were collected at ground and canopy level, of which Aedes fluviatilis and Aedes scapularis comprised 78.8% of the specimens. Haemagogus spp. and Sabethes spp. mosquitoes were not collected, possibly due to the short sampling window during the dry season. No active YFV infection was detected in any of the mosquito pools tested. Eight marmosets (Callithrix penicillata) were captured and tested for arboviral infections. Five out of eight sera, representing both adult and juvenile (less than 17 months old) animals, tested positive for anti-YFV IgM. Interestingly, two adults recaptured in later expeditions revealed seroconversion. One was IgM-positive in July 2024 but negative by September 2024, consistent with the expected decline in IgM levels. The other, initially IgM-negative (as of July 2024), tested positive in April 2025, indicating recent exposure to YFV. These findings provide evidence for the ongoing, low-level circulation of YFV among urban NHPs, posing a continued risk of viral spillover to humans. Moreover, these results highlight the importance of active surveillance in detecting recent infections that would likely be missed by passive monitoring. This integrated approach enhances our understanding of local YF epidemiology and supports early, evidence-based public health interventions to prevent future human outbreaks. Full article

Identifying the diversity of wildlife hosts for malaria parasites in wildlife is crucial for understanding transmission dynamics in endemic regions where humans, vectors, and wildlife heavily overlap. We examined the presence of Plasmodium parasites in free-ranging ring-tailed coatis (Nasua nasua, n = 44) and nine-banded armadillos (Dasypus novemcinctus, n = 66) from an Indigenous community in the Peruvian Amazon. Nested PCR targeting the mitochondrial cytb gene detected Plasmodium spp. DNA in two coatis (4.7%). Sequencing revealed one lineage identical to Plasmodium vivax/P. simium and another to P. malariae/P. brasilianum. A subset of samples was reanalyzed using cox3-based PCR and sequencing in an independent laboratory, confirming P. malariae/P. brasilianum in one coati. No infections were observed in armadillos. These results indicate that coatis in the wild may host diverse Plasmodiidae parasites and that coatis may even carry Plasmodium spp., likely as incidental hosts. Expanding surveillance to additional non-primate mammals will help clarify their role in sylvatic malaria ecology and evaluate potential zoonotic risks. Full article

Triatoma dimidiata is a widely distributed vector of Trypanosoma cruzi in Mexico and Central America, found across a range of habitats from sylvatic to domestic. Vector control has relied heavily on indoor residual spraying with pyrethroids; however, reinfestation and emerging resistance have limited its long-term effectiveness. In this study, we analyzed the genetic diversity and population structure of T. dimidiata from Veracruz, Oaxaca, and Yucatan using mitochondrial markers (cyt b and ND4) and screened for knockdown resistance (kdr)-type mutations in the voltage-gated sodium channel (VGSC) gene. High haplotype diversity and regional differentiation were observed, with most genetic variation occurring between populations. The ND4 marker provided greater resolution than cyt b, revealing ten haplotypes and supporting evidence of recent population expansion. Haplotype networks showed clear geographic segregation, particularly between populations east and west of the Isthmus of Tehuantepec. The L925I mutation, highly associated with pyrethroid resistance, was detected for the first time in Mexican populations of T. dimidiata, albeit at low frequencies. These findings highlight the importance of integrating population genetic data and resistance surveillance into regionally adapted vector control strategies for Chagas disease. Full article

The rabies virus (genus Lyssavirus), is a deadly zoonotic agent affecting humans and animals. Although Mexico has been declared free of canine rabies (V1), sylvatic rabies persists. This study aimed to determine the prevalence of the virus in Desmodus rotundus and other non-hematophagous bat species in Oaxaca. The methodology comprised four stages: a literature review, data requests to the Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria (SENASICA), fieldwork using mist nets across 15 municipalities in Oaxaca, and diagnosis via direct immunofluorescence at the Centro Nacional de Servicios de Diagnóstico en Salud Animal (CENASA). SENASICA reported 89 positive rabies cases (2014–2023) across six laboratories, with the majority (67.02%) attributed to the Oaxaca State Public Health Laboratory. Among the 194 bats analyzed (129 D. rotundus), only three tested positive for the virus, yielding a prevalence of 1.54%. Positive cases were exclusively identified in D. rotundus from San Lucas Ojitlán and The Heroic City of Tlaxiaco. This prevalence aligns with that of national studies, which ranges from 0.05% to 3%. These findings underscore the need to maintain epidemiological surveillance in wild and domestic fauna, alongside public awareness campaigns highlighting bats’ ecological importance for ecosystem conservation and the risks associated with their decline. Full article

The detection of food sources of blood-sucking vectors is essential for a better understanding of the hosts, reservoirs, and other fauna that participate in the transmission web of hemoparasites. The molecular identification of triatomine blood meal sources (BMSs) has been shown to be highly sensitive and taxonomically specific when compared to the immunological method. The application of molecular cloning makes it possible to identify multiple BMS species and/or different individuals/haplotypes of the same vertebrate species in a single triatomine specimen. In Brazil, the molecular detection of BMSs is incipient, with insufficient genetic information on the species of animals involved in the transmission of Trypanosoma cruzi. In this work, we evaluated the sensitivity and specificity of a molecular approach using molecular cloning for the detection of multiple Brazilian mammalian species. The DNA was extracted from blood clots of 13 species of canids, bats, xenarthral, marsupials, and rodents. Serial proportions were used to formulate mixtures combining taxonomically close (belonging to the same family or order) and taxonomically distant (different families) species. The results showed that GenBank lacks reference sequences for some native species tested, such as the sylvatic rodent, Necromys lasiurus, and the wild canid, Lycalopex gymnocercus, for cytb and 12S rDNA, and the rodent Oecomys cleberi for 12S rDNA. The study also demonstrated that it is possible to detect multiple different species, even for those that are taxonomically close. This approach was proven to be efficient for the detection of species in equal and even in disparate unequal proportions, which could represent complementary information about the diversity of potential hosts of T. cruzi. The detection of multiple BMS species in mixed samples provides a more comprehensive and accurate landscape of T. cruzi transmission in nature. Full article

Yellow fever (YF) disease is a viral infection caused by Orthoflavivirus flavi (YFV). YFV is transmitted by hematophagous daytime-biting mosquitoes, predominantly Haemagogus spp. and Sabethes spp. in the sylvatic cycles, and Aedes spp. in urban cycles. In this work, we correlated vaccination coverage with the occurrence and spread of the disease throughout Brazil during the years 2016–2018. The Vale do Mucuri and Vale do Rio Doce regions in Minas Gerais state had the highest number of reported cases. Despite being considered areas with vaccine recommendation since 2008, these regions had less than 60% and 70% vaccination coverage in 2016. The outbreak of YF in Brazil has shown that surveillance for emerging diseases should be constant, especially in relation to the national immunization program. In this study, we observed that low vaccination coverage and the lack of public policies aimed at this region with low population development may have an impact on the reemergence of YF. Full article

Yellow fever is a viral disease with historical importance since epidemics caused thousands of deaths at the end of the 19th century in Argentina. That event was associated with the presence of Aedes aegypti. After the mosquito eradication in South America in the 1960–1970 decade, no epidemic was detected related to this species but epizootics have occurred due to sylvatic vectors belonging to Haemagogus and Sabethes genera. Due to the recolonization of Ae. aegypti and its expanded distribution, the risk of the urbanization of yellow fever has increased over time. However, the reasons why the urban cycle of the yellow fever virus (YFV) has not occurred in South America so far are unknown. We explore the vector competence of Ae. aegypti for YFV transmission. The mosquitos evaluated belonged to colonies from center and northwest cities from Argentina, taking into account the particular genetic features of this mosquito species detected in this country from 2016. We used a viral strain originally isolated in 2009 from Sabethes albiprivus in the country. Viral infection in mosquito body, legs, and saliva was evaluated to estimate the rates of infection, dissemination, and transmission. Our results indicate that both mosquito colonies are competent vectors in the transmission of the YFV but with differences between them. Regarding the infection timeline, we observed a very early infection in the La Plata colony at 3 DPI in contrast to previous studies. This research improves our understanding of the risks of urban YFV transmission in Argentina, highlighting the need for surveillance and specialized vector control strategies in urban settings to prevent yellow fever outbreaks. Full article

Human activity in sylvatic environments and resulting contact with wildlife, such as non-human primates (NHPs), can lead to pathogen spillover or spillback. Both NHPs and humans host a variety of herpesviruses. While these viruses typically cause asymptomatic infections in their natural hosts, they can lead to severe disease or even death when they move into novel hosts. In early 2024, deaths of Callithrix penicillata, the black-tufted marmoset, were reported in an urban park in Belo Horizonte, Minas Gerais, Brazil. The epizootic was investigated in collaboration with CETAS/IBAMA and the Zoonoses Department of Belo Horizonte. Nine marmoset carcasses and four sick marmosets were found in the park; the latter exhibited severe neurological symptoms and systemic illness before succumbing within 48 h. Carcasses were tested for rabies virus and were all negative, and necropsy findings revealed widespread organ damage. In addition, the samples were tested for yellow fever virus, with negative results. Finally, molecular testing, viral isolation, and phylogenetic analysis demonstrated human herpesvirus 1 (HHV-1) as the causative agent. The likely source of infection was human-to-marmoset transmission, facilitated by close interactions such as feeding and handling. This study highlights the risks of pathogen spillover between humans and nonhuman primates, emphasizing the need for enhanced surveillance and public awareness to mitigate future epizootics. Full article

Yellow fever virus (YFV) is an endemic arbovirus in parts of Africa and the Americas. In Brazil, following the eradication of the urban transmission cycle, YFV is maintained in a sylvatic cycle involving several species of neotropical primates and mosquitoes of the genera Haemagogus and Sabethes, which serve as primary and secondary vectors, respectively. During the 2016–2019 outbreak in São Paulo State, a total of 3731 mosquito pools were collected from sites with ongoing epizootic events in 192 municipalities. The RT-qPCR analysis detected YFV in 46 pools (1.4%) across nine mosquito species, including both primary and secondary vectors, as well as species from the genera Aedes and Psorophora. Differences in viral loads were observed among species. While Aedes aegypti was not found to be positive, the detection of natural YFV infection in other Aedes species raises concerns about potential virus reurbanization. Further studies are needed to clarify the role of additional mosquito species in YFV transmission in Brazil. Full article

Phytotelmata are aquatic microenvironments formed by the accumulation of water and organic matter in cavities of plants. These microenvironments serve as breeding sites for various species of mosquitoes, including some of epidemiological importance. Our objective was to identify the mosquito fauna in these microenvironments and to analyze variations in mosquito fauna diversity between bromeliads, tree holes, and bamboo internodes in Cantareira State Park, São Paulo (CSP), Brazil, where there have been reports of yellow-fever epizootics in non-human primates and circulation of plasmodia. Collections were carried out monthly from February 2015 to April 2017. The bromeliads showed greater mosquito species richness and diversity than the tree holes and bamboo internodes, as well as a very different composition. Of the 11 genera collected and 49 taxa identified, Culex (Carrolia) iridescens, Cx. ocellatus, Cx. (Microculex) imitator, and Anopheles (Kerteszia) cruzii were the most abundant. The phytotelmata in the CSP showed significant differences in species richness, diversity, and composition and were found to support a diverse mosquito fauna to develop, including An. cruzii and the sylvatic yellow fever virus vector Haemagogus leucocelaenus. The finding of these epidemiologically important species highlights the key role played by phytotelma breeding sites as places of refuge and species maintenance for these vectors in green areas close to urban centers. Full article

The Oropouche virus (OROV) is a segmented negative-sense RNA arbovirus member of the Peribunyaviridae family, associated with recurring epidemics of Oropouche fever in Central and South America. Since its identification in 1955, OROV has been responsible for outbreaks in both rural and urban areas, with transmission involving sylvatic and urban cycles. This study focuses on the characterization of an OROV isolate from a human clinical sample collected in the state of Rio de Janeiro, a non-endemic region in Brazil, highlighting ultrastructural and morphological aspects of the viral replicative cycle in Vero cells. OROV was isolated in Vero cell monolayers which, following viral inoculation, exhibited marked cytopathic effects (CPEs), mainly represented by changes in cell morphology, including membrane protrusions and vacuolization, as well as cell death. Studies by transmission electron microscopy (TEM) revealed significant ultrastructural changes, such as apoptosis, intense remodeling of membrane-bound organelles and signs of rough endoplasmic reticulum and mitochondrial stress. Additionally, the formation of specialized cytoplasmic vacuoles and intra- and extracellular vesicles emphasized trafficking and intercellular communication as essential mechanisms in OROV infection. RT-qPCR studies confirmed the production of viral progeny in high titers, corroborating the efficiency of this experimental model. These findings contribute to a better understanding of the cytopathogenic mechanisms of OROV infection and the contribution of cellular alterations in OROV morphogenesis. Full article

In 2019, the World Health Organization (WHO) and the Pan American Health Organization (PAHO) bestowed upon Mexico the status of a country free from canine-transmitted human rabies; however, the lingering public health challenge in the nation continues to be the sylvatic cycle of rabies. In Mexico, skunks play a significant role as reservoirs for four antigenic variants of the rabies virus. Nonetheless, up to this point, the specific skunk species involved in this cycle had not been accurately established. This study (2002–2022) aims to identify the taxonomy of skunk specimens diagnosed as rabies-positive in the state of Yucatan, in order to determine the species that serves as the reservoir for the Yucatan sylvatic lineage of rabies. This was achieved through the sequencing of an approximately 680 bp fragment of the mitochondrial gene cytochrome B. All samples belong to the species Spilogale angustifrons yucatanensis. This discovery offers valuable information for understanding and managing the wildlife rabies cycle in Mexico. It also contributes to an improved understanding of the taxonomy within the genus Spilogale. Full article