Biology subjects

Mucci, L. F.

Publications and source records attributed to Mucci, L. F..

4 recordsLinked to original sources

bioRxiv2023

Modelling the transmission and spread of yellow fever in forest landscapes with different spatial configurations

Yellow fever (YF) is a major public health issue in tropical and subtropical areas of Africa and South America. The disease is caused by the yellow fever virus (YFV), an RNA virus transmitted to humans and other animals through the bite of infected mosquitoes (Diptera: Culicidae). In Brazil and other South American countries, YFV is restricted to the sylvatic cycle, with periodic epizootic outbreaks affecting non-human primate (NHP) populations and preceding the emergence of human infections in areas close to forests. In recent epizootic-epidemic waves, the virus has expanded its range and spread across highly fragmented landscapes of the Brazilian Atlantic coast. Empirical evidence has suggested a possible relationship between highly fragmented areas, increased risk of disease in NHP and humans, and easier permeability of YFV through the landscape. Here, we present a hybrid compartmental and network-based model to simulate the transmission and spread of YFV in forest landscapes with different spatial configurations (forest cover and edge densities) and apply the model to test the hypothesis of faster virus percolation in highly fragmented landscapes. The model was parameterized and tested using the pattern- oriented modelling approach. Two different scenarios were simulated to test variations in model outputs, a first where the landscape has no influence on model parameters (default) and a second based on the hypothesis that edge density influences mosquito and dead-end host abundance and dispersal (landscape-dependent). The model was able to reproduce empirical patterns such as the percolation speed of the virus, which presented averages close to 1 km/day, and provided insights into the short persistence time of the virus in the landscape, which was approximately three months on average. When assessing the speed of virus percolation across landscapes, it was found that in the default scenario virus percolation tended to be faster in landscapes with greater forest cover and lower edge density, which contradicts empirical observations. Conversely, in the landscape- dependent scenario, virus percolation was faster in landscapes with high edge density and intermediate forest cover, supporting empirical observations that highly fragmented landscapes favour YFV spread. The proposed model can contribute to the understanding of the dynamics of YFV spread in forested areas, with the potential to be used as an additional tool to support prevention and control measures. The potential applications of the model for YFV and other mosquito-borne diseases are discussed.

ecology↗

bioRxiv2020

A mathematical model for zoonotic transmission of malaria in the Atlantic Forest: exploring the effects of variations in vector abundance and acrodendrophily

Transmission foci of autochthonous malaria caused by Plasmodium vivax-like parasites have frequently been reported in the Atlantic Forest in Southeastern and Southern Brazil. Evidence suggests that malaria is a zoonosis in these areas as human infections by simian Plasmodium species have been detected, and the main vector of malaria in the Atlantic Forest, Anopheles (Kerteszia) cruzii, can blood feed on human and simian hosts. In view of the lack of models that seek to predict the dynamics of zoonotic transmission in this part of the Atlantic Forest, the present study proposes a new deterministic mathematical model that includes a transmission compartment for non-human primates and parameters that take into account vector displacement between the upper and lower forest strata. The effects of variations in the abundance and acrodendrophily of An. cruzii on the prevalence of infected humans in the study area and the basic reproduction number (R0) for malaria were analyzed. The model parameters are based on the literature and fitting of the empirical data. Simulations performed with the model indicate that (1) an increase in the abundance of the vector in relation to the total number of blood-seeking mosquitoes leads to an asymptotic increase in both the proportion of infected individuals at steady state and R0; (2) the proportion of infected humans at steady state is higher when displacement of the vector mosquito between the forest strata increases; and (3) in most scenarios, Plasmodium transmission cannot be sustained only between mosquitoes and humans, which implies that non-human primates play an important role in maintaining the transmission cycle. The proposed model contributes to a better understanding of the dynamics of malaria transmission in the Atlantic Forest. Author summaryThe etiological agents of malaria are protozoa of the genus Plasmodium that are transmitted to humans and other vertebrate hosts by mosquitoes. In the Atlantic Forest in Southeastern and Southern Brazil, human infections by simian Plasmodium species have been detected, showing that in certain situations malaria can be transmitted zoonotically in this region. Anopheles cruzii, a sylvatic mosquito, is considered the main vector of malaria parasites in the Atlantic Forest. The fact that this species can feed on humans and monkeys reinforces the hypothesis of zoonotic transmission. Here we present a new mathematical model to explain the dynamics of zoonotic transmission of malaria in the Atlantic Forest. Simulations performed with the model showed that the prevalence of human cases and the basic reproduction number for malaria can be strongly influenced by variations in the abundance of An. cruzii and the frequency with which these mosquitoes move between the ground and the forest canopy to feed on humans and monkeys, respectively. The proposed model contributes to a better understanding of the dynamics of malaria transmission in the Atlantic Forest.

ecology↗

bioRxiv2019

Zika and dengue viruses infecting wild-caught mosquitoes in an environmental protection area in Brazil

Species of the genus Flavivirus are widespread in Brazil and are a major public health concern. The city of Sao Paulo is in a highly urbanized area with some green spaces which are used for recreation and where potential vertebrate hosts and mosquito vectors of these arboviruses can be found, a scenario that can contribute to the transmission of flaviviruses to humans. This study therefore sought to investigate natural flavivirus infection in mosquitoes collected in the Capivari-Monos Environmental Protection Area (EPA) in the south of the city. Monthly mosquito collections were carried out from March 2016 to April 2017 with CO2-baited CDC light traps. Specimens were identified morphologically and grouped in pools. A total of 260 pools of non-engorged females were inoculated into the C6/36 cell lineage after analysis by indirect immunofluorescence assay (IFA). IFA-positive specimens were tested by qRT-PCR with genus-specific primers targeting a region of ~260 nucleotides in the flavivirus NS5 gene, and the PCR products were sequenced to confirm and identify the flavivirus species. Anopheles (Kerteszia) cruzii and Wyeomyia (Prosopolepis) confusa were the most frequent species collected. Zika virus (ZIKV) nucleotide sequences were detected in three mosquito species, An. cruzii, Limatus durhami and Wy. confusa, and dengue virus 2 (DENV-2) sequences in Culex. spp. and Culex. (Mel.) vaxus. To our knowledge, this is the first report of natural isolation of DENV-2 and ZIKV in sylvatic species of mosquitoes in the Capivari-Monos EPA. Our findings suggest that DENV-2 is present in Culex mosquitoes, and ZIKV in Anopheles, Wyeomyia and Limatus. The flavivirus species identified here are of medical importance; surveillance is therefore recommended in this EPA, where vertebrates and mosquitoes can act as flavivirus hosts and vectors.

zoology↗

bioRxiv2019

Genomic Surveillance of Yellow Fever Virus Epidemic Waves in Sao Paulo, Brazil, 2017 - 2018

Sao Paulo (SP), a densely inhabited state in southeast Brazil that contains the fourth most populated city in the world, recently experienced its largest yellow fever virus (YFV) outbreak in decades. YFV does not normally circulate extensively in SP, so most people were unvaccinated when the outbreak began. Surveillance in non-human primates (NHPs) is important for determining the magnitude and geographic extent of an epizootic, thereby helping to evaluate the risk of YFV spillover to humans. Data from infected NHPs can give more accurate insights into YFV spread than when using data from human cases alone. To contextualise human cases, identify epizootic foci and uncover the rate and direction of YFV spread in SP, we generated and analysed virus genomic data and epizootic case data from NHP in SP. We report the occurrence of three spatiotemporally distinct phases of the outbreak in SP prior to February 2018. We generated 51 new virus genomes from YFV positive cases identified in 23 different municipalities in SP, mostly sampled from non-human primates between October 2016 and January 2018. Although we observe substantial heterogeneity in lineage dispersal velocities between phylogenetic branches, continuous phylogeographic analyses of generated YFV genomes suggest that YFV lineages spread in Sao Paulo state at a mean rate of approximately 1km per day during all phases of the outbreak. Viral lineages from the first epizootic phase in northern Sao Paulo subsequently dispersed towards the south of the state to cause the second and third epizootic phases there. This alters our understanding of how YFV was introduced into the densely populated south of SP state. Our results shed light on the sylvatic transmission of yellow fever in highly fragmented forested regions in SP state and highlight the importance of continued surveillance of zoonotic pathogens in sentinel species. Authors SummarySince July 2016, the southeast region of Brazil has experienced the largest yellow fever virus (YFV) outbreak in decades. Sao Paulo is the most densely populated state in southeast Brazil. The outbreak has caused serious public health concern in the state, as YFV does not normally circulate widely there and most of the 21 million inhabitants were correspondingly unvaccinated against YFV when the outbreak began. In Brazil, YFV typically circulates among non-human primates, and human cases represent isolated spillover events from this predominantly sylvatic cycle. Understanding the epidemiological dynamics and spread of YFV in non-human primates is therefore critical for contextualising human cases, and guiding vaccination strategies that can better protect local human populations. Here, we aim to contextualise human cases, identify epizootic foci and uncover the rate and direction of YFV spread in SP. We analyse the geographic and temporal distribution of observed cases of YFV in non-human primates in Sao Paulo state, and identify three distinct phases of the epizootic. We generate sequence data from 51 YFV-positive cases and perform phylogenetic and phylogeographic analyses aimed at understanding the spatial spread of YFV in Sao Paulo state. Analyses of these data indicate that YFV spread from the north of Sao Paulo state into more densely populated southern regions. Although we observe substantial heterogeneity in the rate at which different sampled YFV lineages spread, the typical rate of spread was low with a mean rate of ~1 km per day. This is consistent with a scenario in which the majority of transmission events occurred between non-human primates and sylvatic vectors across forested patches. Article Summary LineGenomic surveillance of yellow fever in Sao Paulo during the 2016-2018 epizootic

epidemiology↗