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The reservoir for zoonotic o'nyong-nyong virus (ONNV) has remained unknown since this virus was first recognized in Uganda in 1959. Building on existing evidence for mosquito blood-feeding on various frugivorous bat species in Uganda, and seroprevalence for arboviruses among bats in Uganda, we sought to assess if serum samples collected from bats in Uganda demonstrated evidence of exposure to ONNV or the closely related zoonotic chikungunya virus (CHIKV). In total, 652 serum samples collected from six bat species were tested by plaque reduction neutralization test (PRNT) for neutralizing antibodies against ONNV and CHIKV. Forty out of 303 (13.2%) Egyptian rousettes from Maramagambo Forest and 1/13 (8%) little free-tailed bats from Banga Nakiwogo, Entebbe contained neutralizing antibodies against ONNV. In addition, 2/303 (0.7%) of these Egyptian rousettes contained neutralizing antibodies to CHIKV, and 8/303 (2.6%) contained neutralizing antibodies that were nonspecifically reactive to alphaviruses. These data support the interepidemic circulation of ONNV and CHIKV in Uganda, although Egyptian rousette bats are unlikely to serve as reservoirs for these viruses given the inconsistent occurrence of antibody-positive bats.
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[This corrects the article DOI: 10.1371/journal.pntd.0009273.].
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Rift Valley fever virus (RVFV) is a mosquito-transmitted virus with proven ability to emerge into naïve geographic areas. Limited field evidence suggests that RVFV is transmitted vertically from parent mosquito to offspring, but until now this mechanism has not been confirmed in the laboratory. Furthermore, this transmission mechanism has allowed for the prediction of RVFV epizootics based on rainfall patterns collected from satellite information. However, in spite of the relevance to the initiation of epizootic events, laboratory confirmation of vertical transmission has remained an elusive research aim for thirty-five years. Herein we present preliminary evidence of the vertical transmission of RVFV by Culex tarsalis mosquitoes after oral exposure to RVFV. Progeny from three successive gonotrophic cycles were reared to adults, with infectious RVFV confirmed in each developmental stage. Virus was detected in ovarian tissues of parental mosquitoes 7 days after imbibing an infectious bloodmeal. Infection was confirmed in progeny as early as the first gonotrophic cycle, with infection rates ranging from 2.0-10.0%. Virus titers among progeny were low, which may indicate a host mechanism suppressing replication.
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Culex/virologia , Transmissão Vertical de Doenças Infecciosas , Mosquitos Vetores/virologia , Febre do Vale de Rift/transmissão , Animais , Feminino , Humanos , Masculino , Mosquitos Vetores/classificação , Ovário/virologia , Vírus da Febre do Vale do Rift/isolamento & purificação , Carga ViralRESUMO
Bunyaviruses (Negarnaviricota: Bunyavirales) are a large and diverse group of viruses that include important human, veterinary, and plant pathogens. The rapid characterization of known and new emerging pathogens depends on the availability of comprehensive reference sequence databases that can be used to match unknowns, infer evolutionary relationships and pathogenic potential, and make response decisions in an evidence-based manner. In this study, we determined the coding-complete genome sequences of 99 bunyaviruses in the Centers for Disease Control and Prevention's Arbovirus Reference Collection, focusing on orthonairoviruses (family Nairoviridae), orthobunyaviruses (Peribunyaviridae), and phleboviruses (Phenuiviridae) that either completely or partially lacked genome sequences. These viruses had been collected over 66 years from 27 countries from vertebrates and arthropods representing 37 genera. Many of the viruses had been characterized serologically and through experimental infection of animals but were isolated in the pre-sequencing era. We took advantage of our unusually large sample size to systematically evaluate genomic characteristics of these viruses, including reassortment, and co-infection. We corroborated our findings using several independent molecular and virologic approaches, including Sanger sequencing of 197 genome segments, and plaque isolation of viruses from putative co-infected virus stocks. This study contributes to the described genetic diversity of bunyaviruses and will enhance the capacity to characterize emerging human pathogenic bunyaviruses.
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Genoma Viral/genética , Nairovirus/genética , Orthobunyavirus/genética , Vírus de RNA/genética , Animais , Arbovírus/genética , Artrópodes/genética , Sequência de Bases , Humanos , FilogeniaRESUMO
Understanding vertebrate-vector interactions is vitally important for understanding the transmission dynamics of arthropod-vectored pathogens and depends on the ability to accurately identify the vertebrate source of blood-engorged arthropods in field collections using molecular methods. A decade ago, molecular techniques being applied to arthropod blood meal identification were thoroughly reviewed, but there have been significant advancements in the techniques and technologies available since that time. This review highlights the available diagnostic markers in mitochondrial and nuclear DNA and discusses their benefits and shortcomings for use in molecular identification assays. Advances in real-time PCR, high resolution melting analysis, digital PCR, next generation sequencing, microsphere assays, mass spectrometry, and stable isotope analysis each offer novel approaches and advantages to bloodmeal analysis that have gained traction in the field. New, field-forward technologies and platforms have also come into use that offer promising solutions for point-of-care and remote field deployment for rapid bloodmeal source identification. Some of the lessons learned over the last decade, particularly in the fields of DNA barcoding and sequence analysis, are discussed. Though many advancements have been made, technical challenges remain concerning the prevention of sample degradation both by the arthropod before the sample has been obtained and during storage. This review provides a roadmap and guide for those considering modern techniques for arthropod bloodmeal identification and reviews how advances in molecular technology over the past decade have been applied in this unique biomedical context.
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Accurate species-level identification of the source of arthropod bloodmeals is important for deciphering blood feeding patterns of field-collected specimens. Cytochrome c oxidase I (COI) mitochondrial gene sequencing has been used for this purpose; however, species resolution can be difficult to obtain from certain vertebrate genera, including Odocoileus. Sanger sequencing of mitochondrial genes was employed to identify the bloodmeal source of wild-caught mosquitoes trapped in Greeley, Colorado. Initial sequencing of the COI gene of mitochondrial DNA in bloodmeals was inadequate for species-level resolution of bloodmeals from deer in the genus Odocoileus, with current databases returning low fidelity matches to multiple genera. The use of the hypervariable D loop of the control region provided species-level identification of white-tailed deer (Order: Artiodactyla, Family: Cervidae, Odocoileus virginianus); however, taxonomic identification was successful only to genus for mule (O. hemionus hemionus) and black-tailed deer (O. hemionus columbianus). We advocate the use of multiple loci for bloodmeal analysis and the buildout of available databases to include multiple mitochondrial reference genes for reliable host species identification.
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Culicidae/fisiologia , Código de Barras de DNA Taxonômico/instrumentação , Cervos/fisiologia , Cadeia Alimentar , Animais , Colorado , Dieta , Complexo IV da Cadeia de Transporte de Elétrons/análise , Comportamento Alimentar , Controle de Mosquitos/instrumentaçãoRESUMO
The yellow fever mosquito, Aedes aegypti, serves as the primary vector for epidemic transmission of yellow fever, dengue, Zika (ZIKV), and chikungunya viruses to humans. Control of Ae. aegypti is currently limited to insecticide applications and larval habitat management; however, to combat growing challenges with insecticide resistance, novel genetic approaches for vector population reduction or transmission interruption are being aggressively pursued. The objectives of this study were to assess the ability of the Ae. aegypti antiviral exogenous-small interfering RNA (exo-siRNA) response to inhibit ZIKV infection and transmission, and to identify the optimal RNA interference (RNAi) target region in the ZIKV genome. We accomplished these objectives by in vitro transcription of five long double-stranded RNAs (dsRNAs) from the genome region spanning the NS2B-NS3-NS4A genes, which were the most highly conserved among ZIKV RNA sequences representing both East and West African and Asian-American clades, and evaluation of the ability of these dsRNAs to trigger an effective antiviral exo-siRNA response after intrathoracic injection into Ae. aegypti. In a pilot study, five ZIKV dsRNAs were tested by intrathoracic inoculation of 250â¯ng dsRNA into groups of approximately 5-day-old mosquitoes. Three days post-inoculation, mosquitoes were provided an infectious blood-meal containing ZIKV strain PRVABC59 (Puerto Rico), MR766 (Uganda), or 41525 (Senegal). On days 7 and 14 post-infection individual whole mosquito bodies were assessed for ZIKV infectious titer by plaque assays. Based on the results of this initial assessment, three dsRNAs were selected for further evaluation of viral loads of matched body and saliva expectorants using a standardized infectious dose of 1â¯×â¯107â¯PFU/mL of each ZIKV strain. Fourteen days post-exposure to ZIKV, paired saliva and carcass samples were harvested from individual mosquitoes and assessed for ZIKV RNA load by qRT-PCR. Injection of each of the three dsRNAs resulted in significant inhibition of replication of all three strains of ZIKV in mosquito bodies and saliva. This study lays critical groundwork for pursuing ZIKV transmission-blocking strategies that exploit the Ae. aegypti exo-siRNA response for arbovirus suppression in natural populations.
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Aedes/virologia , Interferência de RNA , Infecção por Zika virus/transmissão , Zika virus/genética , Animais , Bovinos , Chlorocebus aethiops , Mosquitos Vetores/virologia , Projetos Piloto , RNA de Cadeia Dupla , RNA Interferente Pequeno , Saliva/virologia , Análise de Sequência de RNA , Células Vero , Carga Viral , Replicação Viral , Zika virus/fisiologia , Infecção por Zika virus/virologiaRESUMO
Rift Valley fever virus (RVFV) poses a major threat of introduction to several continents, including North America. Such an introduction could cause significant losses to the livestock industry, in addition to substantial human morbidity and mortality. Because of the opportunistic blood host selection of Culex tarsalis mosquitoes, we hypothesized that this species could be an important bridge vector of RVFV near feedlots in the event of an introduction. We investigated the mosquito community composition at livestock feedlots and surrounding natural and residential areas to determine differences in mosquito relative abundance and blood feeding patterns attributed to cattle feeding operations. DNA extracted from abdomens of blood-fed mosquitoes were sequenced to determine host identity. Multivariate regression analyses revealed differences between mosquito community assemblages at feedlots and non-feedlot sites (p < 0.05), with this effect driven largely by differential abundances of Aedes vexans (padj < 0.05). Mosquito diversity was lower on feedlots than surrounding areas for three out of four feedlots. Culex tarsalis was abundant at both feedlots and nearby sites. Diverse vertebrate blood meals were detected in Cx. tarsalis at non-feedlot sites, with a shift towards feeding on cattle at feedlots. These data support a potential for Cx. tarsalis to serve as a bridge vector of RVFV between livestock and humans in Colorado.
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Aedes/virologia , Doenças dos Bovinos/transmissão , Culex/virologia , Mosquitos Vetores/virologia , Febre do Vale de Rift/transmissão , Vírus da Febre do Vale do Rift/fisiologia , Doenças dos Ovinos/transmissão , Criação de Animais Domésticos , Animais , Bovinos , Colorado , Gado , OvinosRESUMO
Western equine encephalitis (WEE) was once prevalent and routinely isolated from mosquitoes in Colorado; however, isolations of Western equine encephalitis virus (WEEV) have not been reported from mosquito pools since the early 1990s. The objective of the present study was to test pools of Culex tarsalis (Coquillett) mosquitoes sampled from Weld County, CO, in 2016 for evidence of WEEV infection. Over 7,000 mosquitoes were tested, but none were positive for WEEV RNA. These data indicate that WEEV either was not circulating enzootically in Northern Colorado, was very rare, and would require much more extensive mosquito sampling to detect, or was heterogeneously distributed spatially and temporally and happened to not be present in the area sampled during 2016. Even though the reported incidence of WEE remains null, screening for WEEV viral RNA in mosquito vectors offers forewarning toward the detection and prevention of future outbreaks.
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Culex/virologia , Vírus da Encefalite Equina do Oeste , Mosquitos Vetores/virologia , Animais , Colorado , FemininoRESUMO
Introduction: A number of arboviruses have previously been isolated from naturally-infected East African bats, however the role of bats in arbovirus maintenance is poorly understood. The aim of this study was to investigate the exposure history of Ugandan bats to a panel of arboviruses. Materials and methods: Insectivorous and fruit bats were captured from multiple locations throughout Uganda during 2009 and 2011-2013. All serum samples were tested for neutralizing antibodies against West Nile virus (WNV), yellow fever virus (YFV), dengue 2 virus (DENV-2), Zika virus (ZIKV), Babanki virus (BBKV), and Rift Valley fever virus (RVFV) by plaque reduction neutralization test (PRNT). Sera from up to 626 bats were screened for antibodies against each virus. Results and Discussion: Key findings include the presence of neutralizing antibodies against RVFV in 5/52 (9.6%) of little epauletted fruit bats (Epomophorus labiatus) captured from Kawuku and 3/54 (5.6%) Egyptian rousette bats from Kasokero cave. Antibodies reactive to flaviviruses were widespread across bat taxa and sampling locations. Conclusion: The data presented demonstrate the widespread exposure of bats in Uganda to arboviruses, and highlight particular virus-bat associations that warrant further investigation.
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BACKGROUND: An outbreak of Guillain-Barré syndrome (GBS), a disorder characterized by acute, symmetric limb weakness with decreased or absent deep-tendon reflexes, was reported in Barranquilla, Colombia, after the introduction of Zika virus in 2015. We reviewed clinical data for GBS cases in Barranquilla and performed a case-control investigation to assess the association of suspect and probable Zika virus disease with GBS. METHODS: We used the Brighton Collaboration Criteria to confirm reported GBS patients in Barranquilla during October 2015-April 2016. In April 2016, two neighborhood and age range-matched controls were selected for each confirmed GBS case-patient. We obtained demographics and antecedent symptoms in the 2-month period before GBS onset for case-patients and the same period for controls. Sera were collected for Zika virus antibody testing. Suspected Zika virus disease was defined as a history of rash and ≥2 other Zika-related symptoms (fever, arthralgia, myalgia, or conjunctivitis). Probable Zika virus disease was defined as suspected Zika virus disease with laboratory evidence of a recent Zika virus or flavivirus infection. Conditional logistic regression adjusted for sex and race/ethnicity was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: We confirmed 47 GBS cases. Incidence increased with age (10-fold higher in those ≥60years versus those <20years). We interviewed 40 case-patients and 79 controls. There was no significant difference in laboratory evidence of recent Zika virus or flavivirus infection between case-patients and controls (OR: 2.2; 95% CI: 0.9-5.1). GBS was associated with having suspected (OR: 3.0, 95% CI: 1.1-8.6) or probable Zika virus disease (OR: 4.6, CI: 1.1-19.0). CONCLUSIONS: Older individuals and those with suspected and probable Zika virus disease had higher odds of developing GBS. KEY POINTS: We confirmed a Guillain-Barré syndrome (GBS) outbreak in Barranquilla, Colombia, during October 2015-April 2016. A case-control investigation using neighborhood controls showed an association of suspected and probable Zika virus disease with GBS.
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Síndrome de Guillain-Barré/complicações , Síndrome de Guillain-Barré/epidemiologia , Infecção por Zika virus/complicações , Infecção por Zika virus/epidemiologia , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Criança , Colômbia/epidemiologia , Surtos de Doenças , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Fatores Sexuais , Adulto JovemRESUMO
A large number of arthropod-borne viruses are endemic to East Africa. As a part of the process of undertaking a systematic characterization of the mosquito fauna of Uganda, we examined mosquitoes collected from 2008 through early 2012 for known and novel viruses. In all, 8,288 mosquito pools containing 157,554 mosquitoes were tested. Twenty-nine isolations of 11 different viruses were made from mosquitoes of nine distinct species and from pools identified only to genus Culex. Identified viruses were from family Togaviridae, alphaviruses Sindbis and Babanki viruses; family Rhabdoviridae, hapaviruses Mossuril and Kamese viruses; family Flaviviridae, flaviviruses West Nile and Usutu viruses; family Phenuiviridae, phlebovirus Arumowot virus; and family Peribunyaviridae, orthobunyaviruses Witwatersrand, Pongola, and Germiston viruses. In addition, a novel orthobunyavirus, provisionally named Mburo virus, was isolated from Coquillettidia metallica (Theobald). This is the first report of Babanki, Arumowot, and Mossuril virus isolation from Uganda.
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Arbovírus/isolamento & purificação , Culicidae/virologia , Animais , Arbovírus/classificação , Culicidae/classificação , Feminino , Masculino , UgandaRESUMO
Understanding the ability of the chikungunya virus (CHIKV) to be transmitted by Aedes vectors in the Americas is critical for assessing epidemiological risk. One element that must be considered is the minimum infectious dose of virus that can lead to transmission following the extrinsic incubation period. This study aimed to determine the minimum infection rate for the two Aedes species studied. The results revealed that doses as low as 3.9 log10 plaque-forming units per mL (pfu/mL) of an Asian genotype CHIKV strain can lead to transmission by Ae. albopictus, and doses of at least 5.3 log10 pfu/mL from the same strain are needed for transmission from Ae. aegypti. These low infecting doses suggest that infected individuals may be infectious for almost the entire period of their viremia, and therefore, to prevent further cases, measures should be taken to prevent them from getting bitten by mosquitoes during this period.
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Aedes/virologia , Vírus Chikungunya/isolamento & purificação , Carga Viral , AnimaisRESUMO
In mid-2015, Salvador, Brazil, reported an outbreak of Guillain-Barré syndrome (GBS), coinciding with the introduction and spread of Zika virus (ZIKV). We found that GBS incidence during April-July 2015 among those ≥12 years of age was 5.6 cases/100,000 population/year and increased markedly with increasing age to 14.7 among those ≥60 years of age. We conducted interviews with 41 case-patients and 85 neighborhood controls and found no differences in demographics or exposures prior to GBS-symptom onset. A higher proportion of case-patients (83%) compared to controls (21%) reported an antecedent illness (OR 18.1, CI 6.9-47.5), most commonly characterized by rash, headache, fever, and myalgias, within a median of 8 days prior to GBS onset. Our investigation confirmed an outbreak of GBS, particularly in older adults, that was strongly associated with Zika-like illness and geo-temporally associated with ZIKV transmission, suggesting that ZIKV may result in severe neurologic complications.
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Surtos de Doenças , Síndrome de Guillain-Barré/epidemiologia , Infecção por Zika virus/complicações , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Brasil/epidemiologia , Feminino , Humanos , Incidência , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Understanding the ability of the chikungunya virus (CHIKV) to be transmitted by Aedes vectors in the Americas is critical for assessing epidemiological risk. One element that must be considered is the minimum infectious dose of virus that can lead to transmission following the extrinsic incubation period. This study aimed to determine the minimum infection rate for the two Aedes species studied. The results revealed that doses as low as 3.9 log10 plaqueforming units per mL (pfu/mL) of an Asian genotype CHIKV strain can lead to transmission by Ae. albopictus, and doses of at least 5.3 log10 pfu/mL from the same strain are needed for transmission from Ae. aegypti. These low infecting doses suggest that infected individuals may be infectious for almost the entire period of their viremia, and therefore, to prevent further cases, measures should be taken to prevent them from getting bitten by mosquitoes during this period.
Comprender la capacidad del virus del chikungunya (CHIKV) de ser transmitido por los vectores del género Aedes en la Región de las Américas es fundamental para evaluar el riesgo epidemiológico. Un elemento que debe tenerse en cuenta es la dosis infecciosa mínima de virus que posibilita la transmisión después del período de incubación extrínseco. El objetivo de este estudio ha sido determinar la tasa de infección mínima para las dos especies del género Aedes estudiadas. Los resultados indican que bastan dosis de tan solo 3,9 log10 unidades formadoras de placas por mililitro (ufp/ml) de una cepa de CHIKV del genotipo asiático para que se produzca la transmisión por Ae. albopictus, en tanto que para la transmisión por Ae. aegypti se necesitan dosis de al menos 5,3 log10 ufp/ml de la misma cepa. Estas dosis bajas indican que las personas infectadas podrían conservar el potencial infeccioso prácticamente durante todo el período de viremia y, por consiguiente, a fin de prevenir más casos, habría que tomar medidas para impedir que reciban picaduras de mosquitos durante ese período.
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Aedes , Vírus Chikungunya , Epidemiologia , América , Vírus Chikungunya , EpidemiologiaRESUMO
Dengue virus (DENV) and West Nile virus (WNV) are important reemerging arboviruses that are under-recognized in many parts of Africa due to lack of surveillance. As a part of a study on flavivirus, alphavirus, and parasite exposure in coastal Kenya, we measured neutralizing antibody against DENV and, to evaluate assay specificity, WNV in serum samples that tested positive for serum anti-DENV IgG by enzyme-linked immunosorbent assay. Of 830 anti-DENV IgG-positive samples that were tested for neutralizing activity, 488 (58.8%) neutralized DENV and 94 (11.3%) neutralized WNV. Of children ≤ 10 years of age, 23% and 17% had serum neutralizing antibody to DENV and WNV, respectively, indicating that DENV and WNV transmission has occurred in this region within the past decade. The results suggest that ongoing DENV and WNV transmission continues on the coast of Kenya and supports a need for routine arboviral surveillance in the area to detect and respond to future outbreaks.
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Dengue/epidemiologia , Dengue/transmissão , Febre do Nilo Ocidental/epidemiologia , Febre do Nilo Ocidental/transmissão , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Neutralizantes/sangue , Anticorpos Antivirais/sangue , Criança , Pré-Escolar , Humanos , Lactente , Quênia/epidemiologia , Pessoa de Meia-Idade , Febre do Nilo Ocidental/virologia , Adulto JovemRESUMO
ABSTRACT Understanding the ability of the chikungunya virus (CHIKV) to be transmitted by Aedes vectors in the Americas is critical for assessing epidemiological risk. One element that must be considered is the minimum infectious dose of virus that can lead to transmission following the extrinsic incubation period. This study aimed to determine the minimum infection rate for the two Aedes species studied. The results revealed that doses as low as 3.9 log10 plaque-forming units per mL (pfu/mL) of an Asian genotype CHIKV strain can lead to transmission by Ae. albopictus, and doses of at least 5.3 log10 pfu/mL from the same strain are needed for transmission from Ae. aegypti. These low infecting doses suggest that infected individuals may be infectious for almost the entire period of their viremia, and therefore, to prevent further cases, measures should be taken to prevent them from getting bitten by mosquitoes during this period.(AU)
RESUMEN Comprender la capacidad del virus del chikungunya (CHIKV) de ser transmitido por los vectores del género Aedes en la Región de las Américas es fundamental para evaluar el riesgo epidemiológico. Un elemento que debe tenerse en cuenta es la dosis infecciosa mínima de virus que posibilita la transmisión después del período de incubación extrínseco. El objetivo de este estudio ha sido determinar la tasa de infección mínima para las dos especies del género Aedes estudiadas. Los resultados indican que bastan dosis de tan solo 3,9 log10 unidades formadoras de placas por mililitro (ufp/ml) de una cepa de CHIKV del genotipo asiático para que se produzca la transmisión por Ae. albopictus, en tanto que para la transmisión por Ae. aegypti se necesitan dosis de al menos 5,3 log10 ufp/ml de la misma cepa. Estas dosis bajas indican que las personas infectadas podrían conservar el potencial infeccioso prácticamente durante todo el período de viremia y, por consiguiente, a fin de prevenir más casos, habría que tomar medidas para impedir que reciban picaduras de mosquitos durante ese período.(AU)
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Humanos , Vírus Chikungunya/isolamento & purificação , Aedes/virologia , Febre de Chikungunya/transmissão , Febre de Chikungunya/epidemiologia , América/epidemiologiaRESUMO
Highlands J virus (HJV) is an alphavirus closely related to western equine encephalitis virus (WEEV) and eastern equine encephalitis virus (EEEV). HJV is an avian pathogen with the potential for disruption of poultry operations, but is not known to cause human or equine disease. HJV has only been identified in the eastern United States and is thought to have a transmission cycle similar to that of EEEV involving Culiseta melanura mosquitoes and birds. However, HJV is more genetically similar to WEEV and it remains unclear if it may be transmitted by Culex species mosquitoes like WEEV. Seven strains of HJV were characterized to assess this potential. Phylogenetic analysis of whole genome sequences revealed four distinct HJV lineages (lineages 1-4), and vector competence studies in Cx. tarsalis with four of the HJV strains from different lineages yielded two distinct infection patterns. Lineage 1 strains had low infection rates, while lineages 2 and 4 had significantly higher infection rates similar to those previously published for WEEV. The average mosquito body viral titer was highest at 8 dpi (6.60-7.26 log10 pfu equivalents/body), and head titers at all time points ranged between 6.01 and 6.80 log10 pfu equivalents/head. Nearly 45% of mosquitoes infected with strain AB-80-9 were able to transmit virus in saliva with an average titer of 5.02 log10 pfu equivalents/saliva. A single amino acid difference between high and low infectivity phenotypes was identified at genome position 8605, in the E2 gene. A nonpolar glycine was present in the low infectivity lineage 1 strains, while an acidic glutamic acid was present in the higher infectivity lineage 2 and 4 strains. This study demonstrates HJV transmission by Cx. tarsalis mosquitoes and clearly identifies the potential for transmission in the western United States. Two infection phenotypes were exhibited, indicating the need for further studies to understand Culex species transmission patterns.
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Alphavirus/isolamento & purificação , Culex/virologia , Mosquitos Vetores/virologia , Alphavirus/genética , Animais , Genoma Viral , Filogenia , Saliva/virologiaRESUMO
BACKGROUND: Chikungunya virus (CHIKV) and o'nyong nyong virus (ONNV) are mosquito-borne alphaviruses endemic in East Africa that cause acute febrile illness and arthritis. The objectives of this study were to measure the seroprevalence of CHIKV and ONNV in coastal Kenya and link it to demographics and other risk factors. METHODOLOGY: Demographic and exposure questionnaires were administered to 1,848 participants recruited from two village clusters (Milalani-Nganja and Vuga) in 2009. Sera were tested for alphavirus exposure using standardized CHIKV IgG ELISA protocols and confirmed with plaque reduction neutralization tests (PRNT). Logistic regression models were used to determine the variables associated with seropositivity. Weighted K test for global clustering of houses with alphavirus positive participants was performed for distance ranges of 50-1,000 meters, and G* statistic and kernel density mapping were used to identify locations of higher seroprevalence. PRINCIPAL FINDINGS: 486 (26%) participants were seropositive by IgG ELISA. Of 443 PRNT confirmed positives, 25 samples (6%) were CHIKV+, 250 samples (56%) were ONNV+, and 168 samples (38%) had high titers for both. Age was significantly associated with seropositivity (OR 1.01 per year, 95% C.I. 1.00-1.01); however, younger adults were more likely to be seropositive than older adults. Males were less likely to be seropositive (p<0.05; OR 0.79, 95% C.I. 0.64-0.97). Adults who owned a bicycle (p<0.05; OR 1.37, 95% C.I. 1.00-1.85) or motor vehicle (p<0.05; OR 4.64, 95% C.I. 1.19-18.05) were more likely to be seropositive. Spatial analysis demonstrated hotspots of transmission within each village and clustering among local households in Milalani-Nganja, peaking at the 200-500m range. CONCLUSIONS/SIGNIFICANCE: Alphavirus exposure, particularly ONNV exposure, is common in coastal Kenya with ongoing interepidemic transmission of both ONNV and CHIKV. Women and adults were more likely to be seropositive. Household location may be a defining factor for the ecology of alphaviral transmission in this region.
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Infecções por Alphavirus/epidemiologia , Febre de Chikungunya/epidemiologia , Vírus Chikungunya/imunologia , Vírus O'nyong-nyong/imunologia , Adulto , África Oriental , Idoso , Infecções por Alphavirus/transmissão , Animais , Febre de Chikungunya/transmissão , Criança , Feminino , Humanos , Insetos Vetores/virologia , Quênia/epidemiologia , Masculino , Pessoa de Meia-Idade , Testes de Neutralização , Estudos Soroepidemiológicos , Inquéritos e QuestionáriosRESUMO
Sunguru virus (SUNV), a novel virus belonging to the highly diverse Rhabdoviridae family, was isolated from a domestic chicken in the district of Arua, Uganda, in 2011. This is the first documented isolation of a rhabdovirus from a chicken. SUNV is related to, but distinct from, Boteke virus and other members of the unclassified Sandjimba group. The genome is 11056 nt in length and contains the five core rhabdovirus genes plus an additional C gene (within the ORF of a phosphoprotein gene) and a small hydrophobic protein (between the matrix and glycoprotein genes). Inoculation of vertebrate cells with SUNV resulted in significant viral growth, with a peak titre of 7.8 log10 p.f.u. ml(-1) observed in baby hamster kidney (BHK) cells. Little to no growth was observed in invertebrate cells and in live mosquitoes, with Anopheles gambiae mosquitoes having a 47.4% infection rate in the body but no dissemination of the virus to the salivary glands; this suggests that this novel virus is not arthropod borne as some other members of the family Rhabdoviridae.