Maria Grillet

• PhD
• Professor (Full) at Central University of Venezuela

Malaria in South America remains a serious public health problem. Anopheles (Nyssorhynchus) darlingi is the most important malaria vector across tropical Latin America. Vector-targeted disease control efforts require a thorough understanding of mosquito demographic and evolutionary patterns. We present and analyze whole genomes of 1094 A. darlingi...

Vector control remains an important strategy worldwide to prevent human infection with pathogens transmitted by arthropods. Vector control strategies rely on accurate identification of vector taxa along with vector‐specific biological indicators such as feeding ecology, infection prevalence and insecticide resistance. Multiple ‘DNA barcoding’ proto...

Most emerging human infectious diseases are of zoonotic origin and caused by viruses prone to epidemic events. Zoonosis is becoming more frequent and intense, driven primarily by major environmental changes such as deforestation. Two of the most threatened tropical forests in South America are the Amazon Forest and the Atlantic Forest. How forest d...

Wastewater-based epidemiological surveillance has proven to be a useful and cost-effective tool for detecting COVID-19 outbreaks. Here, our objective was to evaluate its potential as an early warning system in Venezuela by detecting SARS-CoV-2 RNA in wastewater and its correlation with reported cases of COVID-19. Viral RNA was concentrated from was...

Background In Venezuela, the predominant vaccines administered are BBIBP-CorV and Gam-COVID-Vac. Despite robust evidence from randomized clinical trials validating the effectiveness of COVID-19 vaccines in mitigating hospitalization and mortality, there is still a lack of post-authorization safety studies conducted within this demographic populatio...

The malaria parasites Plasmodium falciparum and Plasmodium vivax differ in key biological processes and associated clinical effects, but consequences on population-level transmission dynamics are difficult to predict. This co-endemic malaria study from Guyana details important epidemiological contrasts between the species by coupling population gen...

The single onchocerciasis-endemic focus in the remote Amazon rainforest is shared by Brazil and Venezuela and affects primarily the indigenous Yanomami people. Regional elimination of onchocerciasis is challenged by the magnitude and inaccessibility of this area. In Brazil, 272 onchocerciasis-endemic communities are operationally organized through...

In the Americas, onchocerciasis has been eliminated in 11 of 13 endemic foci by mass administration of ivermectin. The remaining at-risk population resides in a contiguous cross-border transmission zone located in the Amazon jungle in northwest Brazil and southern Venezuela, known as the Yanomami Focus Area. Here, we describe the development and im...

Background Despite nearly a quarter of Venezuelans remaining unvaccinated against coronavirus disease 2019 (COVID-19), the factors contributing to vaccine hesitancy in the country have not been thoroughly investigated. Methods A cross-sectional study was conducted from October 15th to 30th, 2022, using a knowledge, attitudes, and practices (KAP) s...

The malaria parasites Plasmodium falciparum and Plasmodium vivax differ in key biological processes and associated clinical effects, but consequences on population-level transmission dynamics are difficult to predict. This co-endemic malaria study from Guyana details important epidemiological contrasts between the species by coupling population gen...

Dengue viruses are a significant global health concern, causing millions of infections annually and putting approximately half of the world's population at risk, as reported by the World Health Organization (WHO). Understanding the spatial and temporal patterns of dengue virus spread is crucial for effective prevention of future outbreaks. By inves...

In recent decades, Venezuela has faced a severe economic and social crisis, precipitated by political instability, which in turn has particularly a􀆦fected public health provision. Here, we assess how Venezuela’s health crisis has impacted mosquito-borne infectious diseases (MBID s), placing Venezuela as the hotspot of malaria in the region and one...

Background While rigorous randomized clinical trials have substantiated the efficacy of COVID-19 vaccines in reducing hospitalization and mortality rates, there is a paucity of post-authorization analyses conducted in real-world settings. In Venezuela, the primary vaccines administered are Sinopharm and Sputnik-V. However, the performance and effec...

Background Since 2015, the Global Technical Strategy (GTS) for Malaria 2016–2030 has been adopted by the World Health Organization (WHO) as a comprehensive framework to accelerate progress for malaria elimination in endemic countries. This strategy sets the target of reducing global malaria incidence and mortality rates by 90% in 2030. Here it is s...

Background Aedes aegypti and Aedes albopictus are primary vectors of emerging or re-emerging arboviruses that threaten public health worldwide. Many efforts have been made to develop interventions to control these Aedes species populations. Still, countries in the Latin America and the Caribbean (LAC) region struggle to create/design/develop sustai...

Chagas Disease (CD), a chronic infection caused by the Trypanosoma cruzi parasite, is a Neglected Tropical Disease endemic to Latin America. With a re-emergence in Venezuela during the past two decades, the spread of CD has proved susceptible to, and inhibitable by a digital, real-time surveillance system effectuated by Citizen Scientists in commun...

Background Environmental degradation facilitates the emergence of vector-borne diseases, such as malaria, through changes in the ecological landscape that increase human–vector contacts and that expand vector habitats. However, the modifying effects of environmental degradation on climate–disease relationships have not been well explored. Here, we...

A new species of dobsonfly from Venezuela, Corydalus ralphi Martins, Azevêdo, Hamada & Contreras, sp. nov. , was discovered a decade after the last description of a species of this genus in the country. The new species is morphologically similar to C. wanningeri Contreras-Ramos & von der Dunk, sharing a uniform reddish coloration of body and wings...

Over the last twenty years, Venezuela´s public health quality has been declining due to political and socioeconomic factors, causing an ongoing humanitarian crisis. With a decaying healthcare infrastructure, a mass departure of trained medical personnel, and the decline of all public health programs, including disease surveillance and reporting, Ve...

In the southern coast of Mar Chiquita Lake, central Argentina, mosquitoes affect public health and community livelihood, since they transmit pathogens to human beings causing diseases such as malaria, filariasis, encephalitis, yellow fever, and dengue, among others, and have a negative effect on cattle farming as well. To characterize the structure...

The coronavirus disease 2019 (COVID‐19) pandemic has particularly affected countries with weakened health services in Latin America, where proper patient management could be a critical step to address the epidemic. In this study, we aimed to characterize and identify which epidemiological, clinical and paraclinical risk factors defined COVID‐19 inf...

Background The public health impact of the COVID-19 pandemic has motivated a rapid search for potential therapeutics, with some key successes. However, the potential impact of different treatments, and consequently research and procurement priorities, have not been clear. Methods Using a mathematical model of SARS-CoV-2 transmission, COVID-19 dise...

Background Venezuela accounted for 55% of the cases and 73% of the malaria deaths in the Americas in 2019. Bolivar state, in the southeast, contributes > 60% of the country's Plasmodium vivax and Plasmodium falciparum cases every year. This study describes the clinical–epidemiological characteristics of clinical malaria patients in this high-transm...

Testing and isolation have been crucial for controlling the COVID-19 pandemic. Venezuela has one of the weakest testing infrastructures in Latin America and the low number of reported cases in the country has been attributed to substantial underreporting. However, the Venezuelan epidemic seems to have lagged behind other countries in the region, wi...

Objectives To evaluate the genomic epidemiology of SARS-CoV-2 from Venezuelan migrants living in Colombia. Methods SARS-CoV-2 from 30 clinical specimens collected from Venezuelan migrants were sequenced. Genomes were compared with the Wuhan-reference-genome to identify polymorphisms, reconstruct phylogenetic relationships, and perform comparative...

Background Malaria transmission is highly dependent on environmental conditions. The association between climatic variables and malaria transmission is well established, but the interaction between variations in climate and land use change, such as deforestation, is less well understood. Earth observation data provide a valuable and accessible reso...

Simulium mutucuna, a species described based on a single female from Roraima state, was previously synonymized with Simulium paynei and currently is considered a synonym of Simulium rubrithorax. In the present paper we present morphological and molecular evidence supporting the validity of S. mutucuna based on analysis of specimens from Brazil, Ven...

Beta diversity typically increases with decreasing latitude, with explanations of this pattern often based on tropical origins of most clades. Black flies (Diptera: Simuliidae) are at odds with this trend, having a northern origin. Increasing β-diversity with decreasing latitude might also be a product of changes in causal mechanisms structuring lo...

Malaria elimination in Latin America is becoming an elusive goal. Malaria cases reached a historical ~1 million in 2017 and 2018, with Venezuela contributing 53% and 51% of those cases, respectively. Historically, malaria incidence in southern Venezuela has accounted for most of the country's total number of cases. The efficient deployment of disea...

Simulium mutucuna, a species described based on a single female from Roraima state, was previously synonymized with Simulium paynei and currently is considered a synonym of Simulium rubrithorax. In the present paper we present morphological and molecular evidence supporting the validity of S. mutucuna based on analysis of specimens from Brazil, Ven...

Beta diversity typically increases with decreasing latitude, with explanations of this pattern often based on tropical origins of most clades. Black flies (Diptera: Simuliidae) are at odds with this trend, having a northern origin. Increasing β-diversity with decreasing latitude might also be a product of changes in causal mechanisms structuring lo...

Objectives To determine spatial clustering and risk factors for occurrence and intensity of infection for soil-transmitted helminthiasis (STH), namely Ascaris lumbricoides, Trichuris trichiura, Strongyloides stercoralis and hookworms in a Venezuelan rural community. Methods MIF-fixed faecal samples were individually collected for STH testing. The...

Background: Malaria incidence has reached staggering numbers in Venezuela. Commonly, Bolívar State accounted for approximately 70% of the country cases every year. Most cases cluster in the Sifontes municipality, a region characterized by an extractive economy, including gold mining. An increase in migration to Sifontes, driven by gold mining, fue...

Malaria cases in Latin America reached ~1 million in 2017 and 2018, with 53% and 51% reported from Venezuela, respectively. In this study, we characterized the spatiotemporal dynamics of malaria transmission between 2007-2017 in southern Venezuela, the main endemic area of the country. We found that disease transmission was focal and more prevalent...

Integrated vector management and effective control of vector borne diseases

Introduction Venezuela has plunged into a humanitarian, economic, and health crisis of extraordinary proportions. This complex situation is derived from dismantling of structures at the institutional, legal, political, social, and economic level affecting the life and wellbeing of the entire population. Aim This study aims to assess the impact of...

Human onchocerciasis is a chronic parasitic disease caused by Onchocerca volvulus and transmitted by Simulium black flies. Clinical manifestations include skin and eye disease, leading to loss of vision and blindness. The interaction between parasite, susceptible fly (vector), and human host highlights the relationship between environmental variabl...

Venezuela's tumbling economy and authoritarian rule have precipitated an unprecedented humanitarian crisis. Hyperinflation rates now exceed 45,000%, and Venezuela's health system is in free fall. The country is experiencing a massive exodus of biomedical scientists and qualified healthcare professionals. Reemergence of arthropod-borne and vaccine-p...

Since chikungunya virus emerged in the Caribbean region in late 2013, ≈45 countries have experienced chikungunya outbreaks. We described and quantified the spatial and temporal events after the introduction and propagation of chikungunya into an immunologically naive population from the urban north-central region of Venezuela during 2014. The epide...

In the past 5–10 years, Venezuela has faced a severe economic crisis, precipitated by political instability and declining oil revenue. Public health provision has been affected particularly. In this Review, we assess the impact of Venezuela's health-care crisis on vector-borne diseases, and the spillover into neighbouring countries. Between 2000 an...

In the past 5–10 years, Venezuela has faced a severe economic crisis, precipitated by political instability and declining oil revenue. Public health provision has been affected particularly. In this Review, we assess the impact of Venezuela’s health-care crisis on vector-borne diseases, and the spillover into neighbouring countries. Between 2000 an...

Venezuela’s tumbling economy and authoritarian rule have precipitated an unprecedented humanitarian crisis. Hyperinflation rates now exceed 45,000%, and Venezuela’s health system is in free fall. The country is experiencing a massive exodus of biomedical scientists and qualified healthcare professionals. Reemergence of arthropod-borne and vaccine-p...

Four countries (Brazil, Colombia, Peru, and Venezuela) together contributed ~80% of the 875,000 malaria cases reported in the Latin American region (2016). During the 10-year period (2005-2015) when global malaria incidence was dramatically reduced, Brazil and Colombia were an integral part of this trend, on track to meet the mid-term 2020 goal est...

Dengue is a mosquito-borne viral disease of global impact. In Venezuela, dengue has emerged as one of the most important public health problems of urban areas with frequent epidemics since 2001. The long-term pattern of this disease has involved not only a general upward trend in cases but also a dramatic increase in the size and frequency of epide...

Simulium guianense Wise is a Latin American vector complex of black flies associated with transmission of the causal agent of human onchocerciasis (river blindness). An analysis of the chromosomal banding patterns of 607 larvae of S. guianense s. l. revealed a high level of variation involving 83 macrogenomic rearrangements across 25 populations in...

The influence of climatic variables on the dynamics of human malaria has been widely highlighted. Also, it is known that this mosquito-borne infection varies in space and time. However, when the data is spatially incomplete most popular spatio-temporal methods of analysis cannot be applied directly. In this paper, we develop a two step methodology...

Background Dengue virus (DENV) transmission is spatially heterogeneous. Hence, to stratify dengue prevalence in space may be an efficacious strategy to target surveillance and control efforts in a cost-effective manner particularly in Venezuela where dengue is hyperendemic and public health resources are scarce. Here, we determine hot spots of deng...

DS_S1 Codebook GIS Baseline database DS_S1 GIS Baseline database DS_S1 Dengue prevalence per block Candelaria_Cana Azucar DS_S1 Dengue Prevalence per block_Cooperativa (ZIP)

STROBE Checklist. (DOC)

The increase in species richness from the poles to the equator is one of the most consistent biogeographical patterns of species distributions. Using a globally distributed group of stream insects–black flies (Diptera: Simuliidae)–we addressed two questions: (i) How does α‐richness vary among streams of the New World? (ii) Does niche width, as meas...

Zika virus is up till now another mosquito-borne virus (arbovirus) that is rapidly emerging in an urban setting, on a global scale. In the Americas, it has emerged on the heels of a recent chikungunya epidemic. Therefore, currently, there are 6 (six) viral infections circulating and transmitted by Aedes aegypti in the continent if we include the 4...

This study describes the current distribution patterns of the main species of freshwater mollusks incriminated as intermediate hosts of Schistosoma mansoni (Biomphalaria, 4 species), Fasciola hepatica (Galba, 4 species and Pseudosuccinea columella), and Paragonimus sp. (Aroapyrgus vivens) in Venezuela. Additionally, the epidemiological status and t...

The World Health Organization (WHO) has set goals for onchocerciasis elimination in Latin America by 2015. Most of the six previously endemic countries are attaining this goal by implementing twice a year (and in some foci, quarterly) mass ivermectin (Mectizan®) distribution. Elimination of transmission has been verified in Colombia, Ecuador and Me...

We report the species richness of anophelines (Diptera: Culicidae) occurring in the main aquatic habitats (lotic and lentic) of northwestern Amazonas, currently, one of the main endemic areas for malaria in Venezuela. Overall, 10 species of the genus Anopheles Meigen were identified. The dominant subgenus Nyssorhynchus Blanchard was represented by...

Tricorythodes faeculopsis (Ephemeroptera: Leptohyphidae), descripción de nuevos estadíos y primer registro de Venezuela RESUMEN. Tricorythodes faeculopsis Belmont, Salles & Hamada, es redescripto e ilustrado a partir de todos los estados. Se registra por primera vez esta especie de Venezuela. Los imagos macho y hembra y los huevos son descriptos po...

As a continuation of a series of papers to improve the knowledge of the Ephemeroptera fauna of the Venezuelan Guayana´s Uplands, an update of the families Leptophlebiidae, Euthyplociidae and Oligoneuriidae in the region is presented. As a result, Paramaka incognita sp. nov. is described, the female of Askola emmerichi is described for the first tim...

A level playing field is key for global participation in science and scholarship, particularly with regard to how scientific publications are financed and subsequently accessed. However, there are potential pitfalls of the so-called “Gold” open-access (OA) route, in which author-paid publication charges cover the costs of production and publication...

Human onchocerciasis is a chronic parasitic disease caused by Onchocerca volvulus and transmitted by Simulium black flies. Clinical manifestations include skin and eye disease, leading to loss of vision and blindness. The interaction between parasite, transmitting fly (vector), and human host highlights the relationship between environmental variab...

Onchocerciasis is caused by Onchocerca volvulus and transmitted by Simulium species (black flies). In the Americas, the infection has been previously described in 13 discrete regional foci distributed among six countries (Brazil, Colombia, Ecuador, Guatemala, Mexico and Venezuela) where more than 370,000 people are currently considered at risk. Sin...

We give new geographical and morphological data for the Pannota mayflies of Venezuelan Guayanan uplands. Coryphorus aquilus (Coryphoridae), Amanahyphes saguassu and Tricorythopsis yucupe (Leptohyphidae) are newly recorded for Venezuela, the adults of the last species are described for the first time. Macunahyphes pemonensis sp. nov. and Macunahyphe...

Simulium guianense sensu lato es el vector de Onchocerca volvulus en el foco amazónico de oncocercosis, al sur de Venezuela. En esta nota presentamos la primera identificación geográfica, caracterización ecológica y descripción del paisaje del hábitat acuático de las formas pre-adultas de este complejo de especies, en el área de transmisión de esta...

The family Baetidae is still poorly known from Venezuela, particularly in the South of this country. Three field trips were carried out in La Gran Sabana region (Bolívar State). As a result of these trips, four genera (Cryptonympha, Harpagobae-tis, Spiritiops and Zelusia) and nine species are reported for the first time from this region. A discussi...

The family Baetidae is still poorly known from Venezuela, particularly in the South of this country. Three field trips were carried out in La Gran Sabana region (Bolívar State). As a result of these trips, four genera (Cryptonympha, Harpagobaetis, Spiritiops and Zelusia) and nine species are reported for the first time from this region. A discussio...

Simulium guianense sensu lato is the main vector of Onchocerca volvulus in the Amazonian onchocerciasis focus, southern Venezuela. Here, we present the first report of the pre-adult aquatic habitat spatial distribution as well as the landscape and the habitat ecological characterization of this species complex within the endemic area. Larvae and pu...

Mosquito-borne disease spread might exhibit irregular epidemic fronts caused by ecological heterogeneity in the risk factors. To determine Plasmodium vivax infection spread in north-eastern Venezuela, we used the State Transition Index (STI) to detect the spatial locations of malaria incidence boundaries and their dynamics over time. Then, we evalu...

Mosquito-borne pathogen transmission exhibits spatial-temporal variability caused by ecological interactions acting at different scales. We used local spatial statistics and geographically weighted regression (GWR) to determine the spatial pattern of malaria incidence and persistence in northeastern Venezuela. Seven to 11 hot spots of malaria trans...

En este estudio se describe el patrón espacio-temporal de la malaria durante los últimos 12 años en el estado Sucre, Venezuela, con el objetivo de detectar la existencia de focos de alta transmisión de Plasmodium vivax o focos calientes mediante métodos de estadística espacial. La hipótesis es que el patrón espacial de la malaria, en el paisaje epi...

This study describes the temporal and spatial pattern of malaria in northeastern Venezuela during a 12 year period in order to detect hot spots or areas of high Plasmodium vivax incidence. The underlying hypothesis is that malaria transmission is highly heterogeneous and rather local in nature, consequently, the infectious risk is not homogeneous i...

Parasite-vector interactions shape the population dynamics of vector-borne infections and contribute to observed epidemiological patterns. Also, parasites and their vectors may co-evolve, giving rise to locally adapted combinations or complexes with the potential to stabilise the infection. Here, we focus on Onchocerca-Simulium interactions with pa...

Although it is now well established that in the Amazonian onchocerciasis focus, straddling between Venezuela and Brazil, the main vectors in the highland (hyperendemic) and lowland (hypoendemic) areas, are respectively Simulium guianense sensu lato Wise and S. oyapockense s.l. Floch and Abonnenc, investigation of the vectorial role of a third anthr...

Differential distributions of Aedes aegypti and Ae. mediovittatus (potential inter-epidemic dengue vector) and other mosquitoes colonizing bamboo pots in San Juan, Puerto Rico were studied along an urban-rural gradient. City regions (urban, suburban, and rural) and landscape elements within regions (forest [F], low-density housing [LDH], and high-d...

En este artículo se describe la oncocercosis humana, la cual afecta al pueblo Yanomami en el foco amazónico del sur de Venezuela y se revisa el conocimiento actualizado de la enfermedad y su control. La epidemiología de esta infección parasitaria (causada por Onchocerca volvulus), y transmitida por insectos simúlidos, es altamente dependiente de la...

We demonstrate by example a standardized set of protocols for collecting both larval black flies (Diptera: Simuliidae) and the accompanying stream data. By following a few simple proce- dures, powerful data sets can be readily collected. The protocols have been developed as a result of sam- pling over 500 streams in both North and South America. In...

Here we analyze patterns of human infection with Onchocerca volvulus (the cause of river blindness) in different continents and ecologies. In contrast with some geohelminths and schistosome parasites whose worm burdens typically exhibit a humped pattern with host age, patterns of O. volvulus infection vary markedly with locality. To test the hypoth...

We describe the hourly patterns of parous biting activity of the three main simuliid vectors of human onchocerciasis in the Amazonian focus straddling between Venezuela and Brazil, namely, Simulium guianense s.l. Wise; S. incrustatum Lutz, and S. oyapockense s.l. Floch and Abonnenc. Time series of the hourly numbers of host-seeking parous flies cau...