Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-30 (of 68 Records) |
Query Trace: Perera R[original query] |
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Molecular epidemiology: linking molecular scale insights to population impacts.
Schulte PA , Rothman N , Hainaut P , Smith MT , Boffetta P , Perera FP . IARC Sci Publ 2011 (163) 1-7 In a broad sense, molecular epidemiology is the axis that unites insights at the molecular level and understanding of disease at the population level. It is also a partnership between epidemiologists and laboratory scientists in which investigations are conducted using the principles of both disciplines. A key trait of molecular epidemiology is to evaluate and establish the relationship between a biomarker and important exogenous and endogenous exposures, susceptibility, or disease, providing understanding that can be used in future research and public health and clinical practice. When potential solutions or interventions are identified, molecular epidemiology is also useful in developing and conducting clinical and intervention trials. It can then contribute to the translation of biomedical research into practical public health and clinical applications by addressing the medical and population implications of molecular phenomena in terms of reducing risk of disease. This chapter summarizes the contributions and research endeavours of molecular epidemiology and how they link with public health initiatives and clinical practice. |
Perceptions toward Ebola vaccination and correlates of vaccine uptake among high-risk community members in North Kivu, Democratic Republic of the Congo
Perera SM , Garbern SC , Mbong EN , Fleming MK , Muhayangabo RF , Ombeni AB , Kulkarni S , Tchoualeu DD , Kallay R , Song E , Powell J , Gainey M , Glenn B , Mutumwa RM , Mustafa SHB , Earle-Richardson G , Fukunaga R , Abad N , Soke GN , Prybylski D , Fitter DL , Levine AC , Doshi RH . PLOS Glob Public Health 2024 4 (1) e0002566 The tenth Ebola Virus Disease (EVD) outbreak (2018-2020, North Kivu, Ituri, South Kivu) in the Democratic Republic of the Congo (DRC) was the second-largest EVD outbreak in history. During this outbreak, Ebola vaccination was an integral part of the EVD response. We evaluated community perceptions toward Ebola vaccination and identified correlates of Ebola vaccine uptake among high-risk community members in North Kivu, DRC. In March 2021, a cross-sectional survey among adults was implemented in three health zones. We employed a sampling approach mimicking ring vaccination, targeting EVD survivors, their household members, and their neighbors. Outbreak experiences and perceptions toward the Ebola vaccine were assessed, and modified Poisson regression was used to identify correlates of Ebola vaccine uptake among those offered vaccination. Among the 631 individuals surveyed, most (90.2%) reported a high perceived risk of EVD and 71.6% believed that the vaccine could reduce EVD severity; however, 63.7% believed the vaccine had serious side effects. Among the 474 individuals who had been offered vaccination, 397 (83.8%) received the vaccine, 180 (45.3%) of those vaccinated received the vaccine after two or more offers. Correlates positively associated with vaccine uptake included having heard positive information about the vaccine (RR 1.30, 95% CI 1.06-1.60), the belief that the vaccine could prevent EVD (RR 1.23, 95% CI 1.09-1.39), and reporting that religion influenced all decisions (RR 1.13, 95% CI 1.02-1.25). Ebola vaccine uptake was high in this population, although mixed attitudes and vaccine delays were common. Communicating positive vaccine information, emphasizing the efficacy of the Ebola vaccine, and engaging religious leaders to promote vaccination may aid in increasing Ebola vaccine uptake during future outbreaks. |
Pyrethroid susceptibility reversal in Aedes aegypti: A longitudinal study in Tapachula, Mexico
Penilla-Navarro P , Solis-Santoyo F , Lopez-Solis A , Rodriguez AD , Vera-Maloof F , Lozano S , Contreras-Mejía E , Vázquez-Samayoa G , Torreblanca-Lopez R , Perera R , Black Iv WC , Saavedra-Rodriguez K . PLoS Negl Trop Dis 2024 18 (1) e0011369 Pyrethroid resistance in Aedes aegypti has become widespread after almost two decades of frequent applications to reduce the transmission of mosquito-borne diseases. Because few insecticide classes are available for public health use, insecticide resistance management (IRM) is proposed as a strategy to retain their use. A key hypothesis of IRM assumes that negative fitness is associated with resistance, and when insecticides are removed from use, susceptibility is restored. In Tapachula, Mexico, pyrethroids (PYRs) were used exclusively by dengue control programs for 15 years, thereby contributing to selection for high PYR resistance in mosquitoes and failure in dengue control. In 2013, PYRs were replaced by organophosphates-insecticides from a class with a different mode of action. To test the hypothesis that PYR resistance is reversed in the absence of PYRs, we monitored Ae. aegypti's PYR resistance from 2016 to 2021 in Tapachula. We observed significant declining rates in the lethal concentration 50 (LC50), for permethrin and deltamethrin. For each month following the discontinuation of PYR use by vector control programs, we observed increases in the odds of mosquitoes dying by 1.5% and 8.4% for permethrin and deltamethrin, respectively. Also, knockdown-resistance mutations (kdr) in the voltage-gated sodium channel explained the variation in the permethrin LC50s, whereas variation in the deltamethrin LC50s was only explained by time. This trend was rapidly offset by application of a mixture of neonicotinoid and PYRs by vector control programs. Our results suggest that IRM strategies can be used to reverse PYR resistance in Ae. aegypti; however, long-term commitment by operational and community programs will be required for success. |
Standard-dose versus MF59-adjuvanted, high-dose or recombinant-hemagglutinin influenza vaccine immunogenicity in older adults: comparison of A(H3N2) antibody response by prior season's vaccine status
Zhong S , Ng TWY , Skowronski DM , Iuliano AD , Leung NHL , Perera Rapm , Ho F , Fang VJ , Tam YH , Ip DKM , Havers FG , Fry AM , Aziz-Baumgartner E , Barr IG , Peiris M , Thompson MG , Cowling BJ . J Infect Dis 2023 BACKGROUND: Annual influenza vaccination is recommended for older adults but repeated vaccination with standard-dose influenza vaccine has been linked to reduced immunogenicity and effectiveness, especially against A(H3N2) viruses. METHODS: Community-dwelling Hong Kong adults aged 65-82 years were randomly allocated to receive 2017/18 standard-dose quadrivalent, MF59-adjuvanted trivalent, high-dose trivalent, and recombinant-HA quadrivalent vaccination. Antibody response to unchanged A(H3N2) vaccine antigen was compared among participants with and without self-reported prior year (2016/17) standard-dose vaccination. RESULTS: Mean fold rise (MFR) in antibody titers from Day 0 to Day 30 by hemagglutination inhibition and virus microneutralization assays were lower among 2017/18 standard-dose and enhanced vaccine recipients with (range, 1.7-3.0) vs. without (range, 4.3-14.3) prior 2016/17 vaccination. MFR was significantly reduced by about one half to four fifths for previously vaccinated recipients of standard-dose and all three enhanced vaccines (β range, 0.21-0.48). Among prior-year vaccinated older adults, enhanced vaccines induced higher 1.43 to 2.39-fold geometric mean titers and 1.28 to 1.74-fold MFR vs. standard-dose vaccine by microneutralization assay. CONCLUSIONS: In the context of unchanged A(H3N2) vaccine strain, prior-year vaccination was associated with reduced antibody response among both standard-dose and enhanced influenza vaccine recipients. Enhanced vaccines improved antibody response among older adults with prior-year standard-dose vaccination. |
Ebola vaccine uptake and attitudes among healthcare workers in North Kivu, Democratic Republic of the Congo, 2021
Doshi RH , Garbern SC , Kulkarni S , Perera SM , Fleming MK , Muhayangabo RF , Ombeni AB , Tchoualeu DD , Kallay R , Song E , Powell J , Gainey M , Glenn B , Mutumwa RM , Hans Bateyi Mustafa S , Earle-Richardson G , Gao H , Abad N , Soke GN , Fitter DL , Hyde TB , Prybylski D , Levine AC , Jalloh MF , Mbong EN . Front Public Health 2023 11 1080700 INTRODUCTION: During the 2018-2020 Ebola virus disease (EVD) outbreak in the eastern part of the Democratic Republic of the Congo (DRC), prevention and control measures, such as Ebola vaccination were challenging by community mistrust. We aimed to understand perceptions regarding Ebola vaccination and identify determinants of Ebola vaccine uptake among HCWs. METHODS: In March 2021, we conducted a cross-sectional survey among 438 HCWs from 100 randomly selected health facilities in three health zones (Butembo, Beni, Mabalako) affected by the 10th EVD outbreak in North Kivu, DRC. HCWs were eligible if they were ≥ 18 years and were working in a health facility during the outbreak. We used survey logistic regression to assess correlates of first-offer uptake (i.e., having received the vaccine the first time it was offered vs. after subsequent offers). RESULTS: Of the 438 HCWs enrolled in the study, 420 (95.8%) reported that they were eligible and offered an Ebola vaccine. Among those offered vaccination, self-reported uptake of the Ebola vaccine was 99.0% (95% confidence interval (CI) [98.5-99.4]), but first-offer uptake was 70.2% (95% CI [67.1, 73.5]). Nearly all HCWs (94.3%; 95% CI [92.7-95.5]) perceived themselves to be at risk of contracting EVD. The most common concern was that the vaccine would cause side effects (65.7%; 95% CI [61.4-69.7]). In the multivariable analysis, mistrust of the vaccine source or how the vaccine was produced decreased the odds of first-time uptake. DISCUSSION: Overall uptake of the Ebola vaccine was high among HCWs, but uptake at the first offer was substantially lower, which was associated with mistrust of the vaccine source. Future Ebola vaccination efforts should plan to make repeated vaccination offers to HCWs and address their underlying mistrust in the vaccines, which can, in turn, improve community uptake. |
Surface-aerosol stability and pathogenicity of diverse MERS-CoV strains from 2012 - 2018 (preprint)
van Doremalen N , Letko M , Fischer RJ , Bushmaker T , Yinda CK , Schulz J , Seifert SN , Kim NJ , Hemida MG , Kayali G , Park WB , Perera RA , Tamin A , Thornburg NJ , Tong S , Queen K , van Kerkhove MD , Choi YK , Oh MD , Assiri AM , Peiris M , Gerber SI , Munster VJ . bioRxiv 2021 Middle East Respiratory Syndrome coronavirus (MERS-CoV) is a coronavirus that infects both humans and dromedary camels and is responsible for an ongoing outbreak of severe respiratory illness in humans in the Middle East. While some mutations found in camel-derived MERS-CoV strains have been characterized, the majority of natural variation found across MERS-CoV isolates remains unstudied. Here we report on the environmental stability, replication kinetics and pathogenicity of several diverse isolates of MERS-CoV as well as SARS-CoV-2 to serve as a basis of comparison with other stability studies. While most of the MERS-CoV isolates exhibited similar stability and pathogenicity in our experiments, the camel derived isolate, C/KSA/13, exhibited reduced surface stability while another camel isolate, C/BF/15, had reduced pathogenicity in a small animal model. These results suggest that while betacoronaviruses may have similar environmental stability profiles, individual variation can influence this phenotype, underscoring the importance of continual, global viral surveillance. |
COVID-19 vaccine perceptions among ebola-affected communities in North Kivu, Democratic Republic of the Congo, 2021
Garbern SC , Perera SM , Mbong EN , Kulkarni S , Fleming MK , Ombeni AB , Muhayangabo RF , Tchoualeu DD , Kallay R , Song E , Powell J , Gainey M , Glenn B , Gao H , Mutumwa RM , Mustafa SHB , Abad N , Soke GN , Prybylski D , Doshi RH , Fukunaga R , Levine AC . Vaccines (Basel) 2023 11 (5) Populations affected by humanitarian crises and emerging infectious disease outbreaks may have unique concerns and experiences that influence their perceptions toward vaccines. In March 2021, we conducted a survey to examine the perceptions toward COVID-19 vaccines and identify the factors associated with vaccine intention among 631 community members (CMs) and 438 healthcare workers (HCWs) affected by the 2018-2020 Ebola Virus Disease outbreak in North Kivu, Democratic Republic of the Congo. A multivariable logistic regression was used to identify correlates of vaccine intention. Most HCWs (81.7%) and 53.6% of CMs felt at risk of contracting COVID-19; however, vaccine intention was low (27.6% CMs; 39.7% HCWs). In both groups, the perceived risk of contracting COVID-19, general vaccine confidence, and male sex were associated with the intention to get vaccinated, with security concerns preventing vaccine access being negatively associated. Among CMs, getting the Ebola vaccine was associated with the intention to get vaccinated (RR 1.43, 95% CI 1.05-1.94). Among HCWs, concerns about new vaccines' safety and side effects (OR 0.72, 95% CI 0.57-0.91), religion's influence on health decisions (OR 0.45, 95% CI 0.34-0.61), security concerns (OR 0.52, 95% CI 0.37-0.74), and governmental distrust (OR 0.50, 95% CI 0.35-0.70) were negatively associated with vaccine perceptions. Enhanced community engagement and communication that address this population's concerns could help improve vaccine perceptions and vaccination decisions. These findings could facilitate the success of vaccine campaigns in North Kivu and similar settings. |
Prenatal exposure to polybrominated diphenyl ethers and birth outcomes
Reddam A , Sjödin A , Cowell W , Jones R , Wang S , Perera F , Herbstman JB , Kupsco A . Environ Res 2022 216 114830 BACKGROUND: Polybrominated diphenyl ethers (PBDEs) were used as flame retardants and from their end-use products they can be released to accumulate within indoor environments. This may result in exposures to pregnant women with potential adverse effects on the developing fetus. While studies have shown associations between prenatal PBDE exposure and poor birth outcomes, research has mainly focused on birth weight and gestational age and may miss important indicators of newborn size. METHODS: The sample included a cohort of Dominican and African American mother-child pairs from New York City recruited from 1998 to 2006. PBDE congeners (BDE-47, BDE-99, BDE-100, and BDE-153) were measured in cord serum at birth and dichotomized into low (<80th percentile) and high (>80th percentile) categories. Weight, length, head circumference, and gestational age were measured at birth and the ponderal index (birth weight/length x 100), size for gestational age, and population-based z-scores were calculated (n = 305). Separate regression analyses were conducted to estimate associations between PBDEs or PBDE sum (ng/g lipid) and birth outcomes. Quantile g-computation was performed to estimate the effect of total PBDE mixture. We also assessed effect modification by sex and ethnicity. RESULTS: Adjusting for relevant covariates, the high exposure category of BDE-153 was associated with lower birth weight z-score (-0.25, 95% CI: -0.5, 0.0) and longer gestation (0.43 weeks, 95% CI: 0.07, 0.79). The high exposure category of BDE-99 was associated with lower birth length z-score (-0.55, 95% CI: -0.98, -0.12). There was a negative association between the overall PBDE mixture and birth length z-score (-0.10, 95% CI: -0.21, 0.00) per 1 quintile increase in PBDEs. There was no effect modification by sex or ethnicity. CONCLUSIONS: These results suggest that prenatal exposures to BDE-153, BDE-99, and total PBDE mixture are associated with birth outcomes in a cohort of Dominican and African American newborns. |
Fitness cost of sequential selection with deltamethrin in Aedes aegypti (Diptera: Culicidae)
Gonzalez-Santillan FJ , Contreras-Perera Y , Davila-Barboza JA , Juache-Villagrana AE , Gutierrez-Rodriguez SM , Ponce-Garcia G , Lopez-Monroy B , Rodriguez-Sanchez IP , Lenhart AE , Mackenzie-Impoinvil L , Flores AE . J Med Entomol 2022 59 (3) 930-939 In Mexico, Aedes aegypti (L.) is the primary dengue vector, chikungunya, and Zika viruses. The continued use of synthetic pyrethroids has led to the development of resistance in target populations, which has diminished the effectiveness of vector control programs. Resistance has been associated with disadvantages that affect the biological parameters of resistant mosquitoes compared to susceptible ones. In the present study, the disadvantages were evaluated by parameters related to survival and reproduction ('fitness cost') after selection with deltamethrin for five generations. The parameters analyzed were the length of the development cycle, sex ratio, survival, longevity, fecundity, egg viability, preoviposition, oviposition and postoviposition periods, and growth parameters. In the deltamethrin-selected strain, there was a decrease in the development cycle duration, the percentage of pupae, the oviposition period, and eggs viability. Although mean daily fecundity was not affected after the selection process, this, together with the decrease in the survival and fecundity levels by specific age, significantly affected the gross reproductive rate (GRR), net reproductive rate (Ro), and intrinsic growth rate (rm) of the group selected for five generations with deltamethrin compared to the group without selection. Identifying the 'cost' of resistance in biological fitness represents an advantage if it is desired to limit the spread of resistant populations since the fitness cost is the less likely that resistant individuals will spread in the population. This represents an important factor to consider in designing integrated vector management programs. |
Understanding the role of persistent organic pollutants and stress in the association between proximity to the World Trade Center disaster and birth outcomes
Spratlen MJ , Perera FP , Sjodin A , Wang Y , Herbstman JB , Trasande L . Int J Environ Res Public Health 2022 19 (4) Fetal growth is affected by exposure to both prenatal stress and environmental contaminants. The attacks on the World Trade Center (WTC) resulted in exposure to chemicals and psychological stress amongst New York City residents. We measured prenatal maternal stress and exposure to persistent organic pollutants (polybrominated diphenyl ethers, polychlorinated biphenyls, and polychlorinated dibenzo-p-dioxins (PCDDs)) in 108 participants from a Columbia University WTC birth cohort. Principal component (PC) analyses were conducted to characterize the mixture of exposure to the three groups of chemicals. We evaluated the associations between geographical exposures (proximity to the WTC disaster) and both chemical exposures (PCs) and stress (demoralization). We then evaluated the effect these exposures (PCs and stress) had on previously reported associations between geographical WTC exposure and birth outcomes (birth weight and birth length) in this study population to understand their individual roles in the observed associations. Geographical exposure via proximity to the WTC was associated with the PC reflecting higher PCDD exposure (PC3) (β = 0.60, 95% CI: 0.03, 1.18 for living/working within 2 miles of the WTC; and β = 0.73, 95% CI = 0.08, 1.38 for living within 2 miles of WTC). Previously reported reductions in birth weight and length associated with WTC proximity (β = -215.2, 95% CI: -416.2, -14.3 and β = -1.47, 95% CI: -2.6, -0.34, respectively) were attenuated and no longer significant for birth weight (β = -156.4, 95% CI: -358.2, 45.4) after adjusting for PC3, suggesting that PCDDs may act as partial mediators in this previously observed association. The results of this study can help focus future research on the long-term health effects of these prenatally exposed populations. |
Surface‒Aerosol Stability and Pathogenicity of Diverse Middle East Respiratory Syndrome Coronavirus Strains, 2012‒2018.
van Doremalen N , Letko M , Fischer RJ , Bushmaker T , Schulz J , Yinda CK , Seifert SN , Kim NJ , Hemida MG , Kayali G , Park WB , Perera Rapm , Tamin A , Thornburg NJ , Tong S , Queen K , van Kerkhove MD , Choi YK , Oh MD , Assiri AM , Peiris M , Gerber SI , Munster VJ . Emerg Infect Dis 2021 27 (12) 3052-3062 Middle East respiratory syndrome coronavirus (MERS-CoV) infects humans and dromedary camels and is responsible for an ongoing outbreak of severe respiratory illness in humans in the Middle East. Although some mutations found in camel-derived MERS-CoV strains have been characterized, most natural variation found across MERS-CoV isolates remains unstudied. We report on the environmental stability, replication kinetics, and pathogenicity of several diverse isolates of MERS-CoV, as well as isolates of severe acute respiratory syndrome coronavirus 2, to serve as a basis of comparison with other stability studies. Although most MERS-CoV isolates had similar stability and pathogenicity in our experiments, the camel-derived isolate C/KSA/13 had reduced surface stability, and another camel isolate, C/BF/15, had reduced pathogenicity in a small animal model. These results suggest that although betacoronaviruses might have similar environmental stability profiles, individual variation can influence this phenotype, underscoring the need for continual global viral surveillance. |
Laboratory development and pilot-scale deployment of a two-part foamed rock dust
Brown CB , Perera IE , Harris ML , Chasko LL , Addis JD , Klima S . J Loss Prev Process Ind 2022 74 U.S. Code of Federal Regulations 30 CFR 75.402 and 75.403 require 80% total incombustible content to be maintained within 40 feet of the coal mine face via the liberal application of rock dust. Unfortunately, this application of rock dust limits miners' visibility downwind and can increase the miners' exposures to a respirable nuisance dust. Wet rock dust applied as a slurry is, at times, used to negate these negative effects. Although this aids in meeting the total incombustible limits, the slurry forms a hard cake when dried and no longer effectively disperses as needed to suppress a coal dust explosion. As a result, a dry rock dust must be reapplied to maintain a dispersible layer. Therefore, researchers from the National Institute for Occupational Safety and Health (NIOSH) have been working towards finding and testing a foamed rock dust formulation that can be applied wet on mine surfaces and remain dispersible once dried which minimizes the likelihood of mine disasters, including mine explosions. The initial tests were aimed at discerning dispersion characteristics of three different foamed rock dusts via the NIOSH-developed dispersion chamber and led to identification of a two-part foam with adequate dispersion characteristics. The current study was conducted to assess the robustness of the two-part foamed rock dust. Through a series of laboratory-scale experiments using the dispersibility chamber, the effects of testing conditions and product formulations on the foam's dispersibility was determined. Some of the tested variables include: exposing the foam to high humidity, varying the component levels of the foamed rock dust, altering the rock dust size distribution, and varying the rock dust types. Further pilot-scale tests examined the atmospheric concentrations of dust via personal dust monitors downwind of foamed rock dust production and application. Additionally, product consistency was recorded during pilot-scale testing at key points in the formulation and application. The results of these experiments will be discussed in this paper. © 2021 |
Permethrin resistance in Aedes aegypti: Genomic variants that confer knockdown resistance, recovery, and death.
Saavedra-Rodriguez K , Campbell CL , Lozano S , Penilla-Navarro P , Lopez-Solis A , Solis-Santoyo F , Rodriguez AD , Perera R , Black IV WC . PLoS Genet 2021 17 (6) e1009606 Pyrethroids are one of the few classes of insecticides available to control Aedes aegypti, the major vector of dengue, chikungunya, and Zika viruses. Unfortunately, evolving mechanisms of pyrethroid resistance in mosquito populations threaten our ability to control disease outbreaks. Two common pyrethroid resistance mechanisms occur in Ae. aegypti: 1) knockdown resistance, which involves amino acid substitutions at the pyrethroid target site-the voltage-gated sodium channel (VGSC)-and 2) enhanced metabolism by detoxification enzymes. When a heterogeneous population of mosquitoes is exposed to pyrethroids, different responses occur. During exposure, a proportion of mosquitoes exhibit immediate knockdown, whereas others are not knocked-down and are designated knockdown resistant (kdr). When these individuals are removed from the source of insecticide, the knocked-down mosquitoes can either remain in this status and lead to dead or recover within a few hours. The proportion of these phenotypic responses is dependent on the pyrethroid concentration and the genetic background of the population tested. In this study, we sequenced and performed pairwise genome comparisons between kdr, recovered, and dead phenotypes in a pyrethroid-resistant colony from Tapachula, Mexico. We identified single-nucleotide polymorphisms (SNPs) associated with each phenotype and identified genes that are likely associated with the mechanisms of pyrethroid resistance, including detoxification, the cuticle, and insecticide target sites. We identified high association between kdr and mutations at VGSC and moderate association with additional insecticide target site, detoxification, and cuticle protein coding genes. Recovery was associated with cuticle proteins, the voltage-dependent calcium channel, and a different group of detoxification genes. We provide a list of detoxification genes under directional selection in this field-resistant population. Their functional roles in pyrethroid metabolism and their potential uses as genomic markers of resistance require validation. |
Analysis and Characterization of Anti-Caking Additives Used in Rock Dust to Mitigate Mine Explosions
Perera IE , Harris ML , Sapko MJ . Min Metall Explor 2021 38 (3) 1411-1419 Experiments conducted with limestone dusts and dolomitic marble dusts have indicated that when rock dust is wetted and subsequently dried, it becomes a solid, non-dispersible cake. However, in order to be effectively inert a coal dust explosion, rock dust must be able to disperse as individual particles to air. To counteract this, rock dust manufacturers created treated rock dusts that will resist caking after moisture exposure. National Institute for Occupational Safety and Health (NIOSH) researchers conducted a series of laboratory-scale experiments on four base rock dusts and their treated counterparts to assess the effectiveness of various anti-caking additives after being exposed to moisture and then dried. The dusts were exposed to moisture using humidity cabinets having a high relative humidity (99% RH) and by also exposing the rock dust bed to water through bottom wicking. The dusts were then evaluated for dispersibility after drying using the NIOSH-designed dust dispersion chamber. The anti-caking additives were different concentrations of stearic acid, oleic acid, and xylene-based surfactants. All results were compared to a reference rock dust used to conduct large-scale experiments in the Lake Lynn Experimental Mine (LLEM), Fairchance, PA. When the untreated dusts were dried after exposure to moisture for 1 day, no dispersion was measured. However, rock dusts treated with anti-caking agents were readily dispersible even after exposure to moisture for 6 months. This report details the analysis and characterization of anti-caking additives using the NIOSH-designed dispersion chamber and the 20-L explosion test chamber. © 2019, This is a U.S. government work and its text is not subject to copyright protection in the United States; however, its text may be subject to foreign copyright protection. |
Leveraging mobile phone surveys during the COVID-19 pandemic in Ecuador and Sri Lanka: Methods, timeline and findings.
Phadnis R , Wickramasinghe C , Zevallos JC , Davlin S , Kumarapeli V , Lea V , Lee J , Perera U , Solórzano FX , Vásconez JF . PLoS One 2021 16 (4) e0250171 Effective and rapid decision making during a pandemic requires data not only about infections, but also about human behavior. Mobile phone surveys (MPS) offer the opportunity to collect real-time data on behavior, exposure, knowledge, and perception, as well as care and treatment to inform decision making. The surveys aimed to collect coronavirus disease 2019 (COVID-19) related information in Ecuador and Sri Lanka using mobile phones. In Ecuador, a Knowledge, Attitudes and Practices (KAP) survey was conducted. In Sri Lanka, an evaluation of a novel medicine delivery system was conducted. Using the established mobile network operator channels and technical assistance provided through The Bloomberg Philanthropies Data for Health Initiative (D4H), Ministries of Health fielded a population-based COVID-19-specific MPS using Surveda, the open source data collection tool developed as part of the initiative. A total of 1,185 adults in Ecuador completed the MPS in 14 days. A total of 5,001 adults over the age of 35 in Sri Lanka completed the MPS in 44 days. Both samples were adjusted to the 2019 United Nations Population Estimates to produce population-based estimates by age and sex. The Ecuador COVID-19 MPS found that there was compliance with the mitigation strategies implemented in that country. Overall, 96.5% of Ecuadorians reported wearing a face mask or face covering when leaving home. Overall, 3.8% of Sri Lankans used the service to receive medicines from a government clinic. Among those who used the medicine delivery service in Sri Lanka, 95.8% of those who used a private pharmacy received their medications within one week, and 69.9% of those using a government clinic reported the same. These studies demonstrate that MPS can be conducted quickly and gather essential data. MPS can help monitor the impact of interventions and programs, and rapidly identify what works in mitigating the impact of COVID-19. |
Immunogenicity of standard, high-dose, MF59-adjuvanted, and recombinant-HA seasonal influenza vaccination in older adults
Li APY , Cohen CA , Leung NHL , Fang VJ , Gangappa S , Sambhara S , Levine MZ , Iuliano AD , Perera Rapm , Ip DKM , Peiris JSM , Thompson MG , Cowling BJ , Valkenburg SA . NPJ Vaccines 2021 6 (1) 25 The vaccine efficacy of standard-dose seasonal inactivated influenza vaccines (S-IIV) can be improved by the use of vaccines with higher antigen content or adjuvants. We conducted a randomized controlled trial in older adults to compare cellular and antibody responses of S-IIV versus enhanced vaccines (eIIV): MF59-adjuvanted (A-eIIV), high-dose (H-eIIV), and recombinant-hemagglutinin (HA) (R-eIIV). All vaccines induced comparable H3-HA-specific IgG and elevated antibody-dependent cellular cytotoxicity (ADCC) activity at day 30 post vaccination. H3-HA-specific ADCC responses were greatest following H-eIIV. Only A-eIIV increased H3-HA-IgG avidity, HA-stalk IgG and ADCC activity. eIIVs also increased polyfunctional CD4+ and CD8+ T cell responses, while cellular immune responses were skewed toward single-cytokine-producing T cells among S-IIV subjects. Our study provides further immunological evidence for the preferential use of eIIVs in older adults as each vaccine platform had an advantage over the standard-dose vaccine in terms of NK cell activation, HA-stalk antibodies, and T cell responses. |
Large-scale explosion propagation testing of treated and non-treated rock dust when overlain by a thin layer of coal dust
Perera IE , Harris ML , Sapko MJ , Dyduch Z , Cybulski K , Hildebrandt R , Goodman GVR . Min Metall Explor 2021 38 (2) 1009-1017 To prevent coal dust explosion propagations, rock dust needs to be lifted and suspended in the air with the coal dust during an explosion. The addition of anti-caking agents prevents caking of rock dust in the presence of water. Mining and rock dusting processes can frequently create alternating layers of rock dust and float coal dust on mine surfaces. For this test series, a thin layer of coal dust was distributed on top of a layer of either treated or non-treated rock dust in the Experimental Mine Barbara, Poland. The experimental results compare the effectiveness of treated and non-treated rock dusts to attenuate a propagating coal dust explosion initiated with either strong or weak methane explosions. Experimental results indicate that the treated rock dust performs better than non-treated rock dust in arresting a propagating explosion, especially in the presence of moisture. |
Development and assessment of a pooled serum as candidate standard to measure influenza a virus group 1 hemagglutinin stalk-reactive antibodies
Carreño JM , McDonald JU , Hurst T , Rigsby P , Atkinson E , Charles L , Nachbagauer R , Behzadi MA , Strohmeier S , Coughlan L , Aydillo T , Brandenburg B , García-Sastre A , Kaszas K , Levine MZ , Manenti A , McDermott AB , Montomoli E , Muchene L , Narpala SR , Perera Rapm , Salisch NC , Valkenburg SA , Zhou F , Engelhardt OG , Krammer F . Vaccines (Basel) 2020 8 (4) The stalk domain of the hemagglutinin has been identified as a target for induction of protective antibody responses due to its high degree of conservation among numerous influenza subtypes and strains. However, current assays to measure stalk-based immunity are not standardized. Hence, harmonization of assay readouts would help to compare experiments conducted in different laboratories and increase confidence in results. Here, serum samples from healthy individuals (n = 110) were screened using a chimeric cH6/1 hemagglutinin enzyme-linked immunosorbent assay (ELISA) that measures stalk-reactive antibodies. We identified samples with moderate to high IgG anti-stalk antibody levels. Likewise, screening of the samples using the mini-hemagglutinin (HA) headless construct #4900 and analysis of the correlation between the two assays confirmed the presence and specificity of anti-stalk antibodies. Additionally, samples were characterized by a cH6/1N5 virus-based neutralization assay, an antibody-dependent cell-mediated cytotoxicity (ADCC) assay, and competition ELISAs, using the stalk-reactive monoclonal antibodies KB2 (mouse) and CR9114 (human). A "pooled serum" (PS) consisting of a mixture of selected serum samples was generated. The PS exhibited high levels of stalk-reactive antibodies, had a cH6/1N5-based neutralization titer of 320, and contained high levels of stalk-specific antibodies with ADCC activity. The PS, along with blinded samples of varying anti-stalk antibody titers, was distributed to multiple collaborators worldwide in a pilot collaborative study. The samples were subjected to different assays available in the different laboratories, to measure either binding or functional properties of the stalk-reactive antibodies contained in the serum. Results from binding and neutralization assays were analyzed to determine whether use of the PS as a standard could lead to better agreement between laboratories. The work presented here points the way towards the development of a serum standard for antibodies to the HA stalk domain of phylogenetic group 1. |
Prenatal and early childhood exposure to phthalates and childhood behavior at age 7 years
Daniel S , Balalian AA , Insel BJ , Liu X , Whyatt RM , Calafat AM , Rauh VA , Perera FP , Hoepner LA , Herbstman J , Factor-Litvak P . Environ Int 2020 143 105894 BACKGROUND: Emerging evidence suggests that phthalate exposure may be associated with behavior problems in children and that these associations may be sex specific. METHODS: In a follow up study of 411 inner-city minority mothers and their children, mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBzP), monoisobutyl phthalate (MiBP), monethyl phthalate (MEP) and four di-2-ethylhexyl phthalate metabolites (DEHP) were quantified in maternal urine samples collected during the third trimester and in child urine samples at ages 3 and 5 years. The Conners' Parent Rating Scale-Revised: Long Form (CPRS) and Child Behavior Checklist (CBCL) were administered to the mothers to assess children's behavior problems at 7 years of age. The analysis included children with available measures of CBCL, CPRS and phthalates measured in maternal urine. We performed both Quasi-Poisson regression and a mixture analysis using Weighted Quantile Sum(WQS) regression to assess the risk for CPRS scores and for internalizing and externalizing behaviors (from the CBCL) following intra-uterine exposure to the phthalate metabolites for boys and girls separately. RESULTS: Among boys, increases in in anxious-shy behaviors were associated with prenatal exposure to MBzP (Mean Ratio [MR] = 1.20, 95%CI 1.05-1.36) and MiBP (Mean Ratio (MR) = 1.22, 95%CI 1.02-1.47). Among girls, increases in perfectionism were associated with MBzP (MR = 1.15, 95%CI 1.01-1.30). In both boys and girls, increases in psychosomatic problems were associated with MiBP (MR = 1.28, 95%CI 1.02-1.60), and MnBP (MR = 1.28, 95%CI 1.02-1.59), respectively. Among girls, decreased hyperactivity was associated with two DEHP metabolites, mono(2-ethyl-5-oxohexyl) phthalate (MR = 0.83, 95%CI 0.71-0.98) and mono(2-ethyl-5-hydroxyhexyl) phthalate (MR = 0.85, 95%CI 0.72-0.99). Using weighted Quantile Sum logistic regression, no associations were found between the Weighted Quantile Sum (WQS) of phthalate metabolites and CPRS scores or externalizing and internalizing behaviors. Nonetheless, when the analysis was performed separately for DEHP and non-DEHP metabolites significant associations were found between the WQS of DEHP metabolites and social problems in boys (OR = 2.15, 95%CI 1.13-4.06, p-value = 0.02) anxious-shy problems in girls (OR = 2.19, 95%CI 1.15-4.16, p = 0.02), and emotional lability problems in all children (OR = 0.61, 95%CI 0.38-0.97, p = 0.04). MEHP and MEOHP were the most highly weighted DEHP metabolites in WQS mixture. The analysis performed with CBCL scale corroborated these associations. CONCLUSION: Concentration of non-DEHP metabolites was associated with anxious-shy behaviors among boys. DEHP phthalate metabolites were associated with decreased hyperactivity and impulsivity among girls on CPRS scores. These findings lend further support to the adverse associations between prenatal phthalate exposure and childhood outcomes, and clearly suggest that such associations are sex and mixture specific. |
Comparative reactogenicity of enhanced influenza vaccines in older adults
Cowling BJ , Thompson MG , Ng TWY , Fang VJ , Perera Rapm , Leung NHL , Chen Y , So HC , Ip DKM , Iuliano AD . J Infect Dis 2020 222 (8) 1383-1391 BACKGROUND: We analysed data from a randomized controlled trial on the reactogenicity of three enhanced influenza vaccines compared to standard-dose inactivated influenza vaccine. METHODS: We enrolled community-dwelling older adults in Hong Kong, and randomly allocated them to receive 2017/18 northern hemisphere formulations of: standard-dose vaccine (FluQuadri, Sanofi Pasteur); MF59-adjuvanted vaccine (FLUAD, Seqirus); high-dose vaccine (Fluzone High Dose, Sanofi Pasteur); or recombinant-hemagglutinin vaccine (Flublok, Sanofi Pasteur). Local and systemic reactions were evaluated at Days 1, 3, 7 and 14 after vaccination. RESULTS: Reported reactions were generally mild and short-lived. Systemic reactions occurred in similar proportions of participants by vaccine. Some local reactions were slightly more frequently reported among recipients of the MF59-adjuvanted vaccine and the high-dose vaccine compared to standard dose recipients. Participants reporting feverishness one day after vaccination had mean-fold-rises in post-vaccination hemagglutination inhibition titers that were 1.85-fold higher (95% CI: 1.01, 3.38) for A(H1N1) compared to those who did not report feverishness. CONCLUSIONS: Some acute local reactions were more frequent following vaccination with MF59-adjuvanted and high-dose influenza vaccines compared to standard-dose inactivated influenza vaccine, while systemic symptoms occurred at similar frequencies in all groups. The association between feverishness and immunogenicity should be further investigated in a larger population. |
Impact of deltamethrin selection on kdr mutations and insecticide detoxifying enzymes in Aedes aegypti from Mexico.
Contreras-Perera Y , Ponce-Garcia G , Villanueva-Segura K , Lopez-Monroy B , Rodriguez-Sanchez IP , Lenhart A , Manrique-Saide P , Flores AE . Parasit Vectors 2020 13 (1) 224 BACKGROUND: Insecticide resistance is a serious problem for vector control programmes worldwide. Resistance is commonly attributed to mutations at the insecticide's target site or increased activity of detoxification enzymes. METHODS: We determined the knockdown concentration (KC50) and lethal concentration (LC50) of deltamethrin in six natural populations of adult Aedes aegypti from southeastern Mexico. These populations were then selected over five generations using the LC50 from the preceding generation that underwent selection, and the heritability of deltamethrin resistance was quantified. For each generation, we also determined the frequency of the kdr alleles L410, I1016 and C1534, and the levels of activity of three enzyme families (alpha- and beta-esterases, mixed-function oxidases and glutathione S-transferases (GST)) associated with insecticide detoxification. RESULTS: There was an increase in KC50 and LC50 values in the subsequent generations of selection with deltamethrin (FS5vs FS0). According to the resistance ratios (RRs), we detected increases in LC50 ranging from 1.5 to 5.6 times the values of the parental generation and in KC50 ranging from 1.3-3.8 times the values of the parental generation. Triple homozygous mutant individuals (tri-locus, LL/II/CC) were present in the parental generations and increased in frequency after selection. The frequency of L410 increased from 1.18-fold to 2.63-fold after selection with deltamethrin (FS5vs FS0) in the populations analyzed; for I1016 an increase between 1.19-fold to 2.79-fold was observed, and C1534 was fixed in all populations after deltamethrin selection. Enzymatic activity varied significantly over the generations of selection. However, only alpha- esterase activity remained elevated in multiple populations after five generations of deltamethrin selection. We observed an increase in the mean activity levels of GSTs in two of the six populations analyzed. CONCLUSIONS: The high levels of resistance and their association with high frequencies of kdr mutations (V410L, V1016I and F1534C) obtained through artificial selection, suggest an important role of these mutations in conferring resistance to deltamethrin. We highlight the need to implement strategies that involve the monitoring of kdr frequencies in insecticide resistance monitoring and management programmes. |
Comparative immunogenicity of several enhanced influenza vaccine options for older adults: A randomized, controlled trial
Cowling BJ , Perera Rapm , Valkenburg SA , Leung NHL , Iuliano AD , Tam YH , Wong JHF , Fang VJ , Li APY , So HC , Ip DKM , Azziz-Baumgartner E , Fry AM , Levine MZ , Gangappa S , Sambhara S , Barr IG , Skowronski DM , Peiris JSM , Thompson MG . Clin Infect Dis 2019 71 (7) 1704-1714 BACKGROUND: Enhanced influenza vaccines may improve protection for older adults, but comparative immunogenicity data are limited. Our objective was to examine immune responses to enhanced influenza vaccines, compared to standard-dose vaccines, in community-dwelling older adults. METHODS: Community-dwelling older adults aged 65-82 years in Hong Kong were randomly allocated (October 2017-January 2018) to receive 2017-2018 Northern hemisphere formulations of a standard-dose quadrivalent vaccine, MF59-adjuvanted trivalent vaccine, high-dose trivalent vaccine, or recombinant-hemagglutinin (rHA) quadrivalent vaccine. Sera collected from 200 recipients of each vaccine before and at 30-days postvaccination were assessed for antibodies to egg-propagated vaccine strains by hemagglutination inhibition (HAI) and to cell-propagated A/Hong Kong/4801/2014(H3N2) virus by microneutralization (MN). Influenza-specific CD4+ and CD8+ T cell responses were assessed in 20 participants per group. RESULTS: Mean fold rises (MFR) in HAI titers to egg-propagated A(H1N1) and A(H3N2) and the MFR in MN to cell-propagated A(H3N2) were statistically significantly higher in the enhanced vaccine groups, compared to the standard-dose vaccine. The MFR in MN to cell-propagated A(H3N2) was highest among rHA recipients (4.7), followed by high-dose (3.4) and MF59-adjuvanted (2.9) recipients, compared to standard-dose recipients (2.3). Similarly, the ratio of postvaccination MN titers among rHA recipients to cell-propagated A(H3N2) recipients was 2.57-fold higher than the standard-dose vaccine, which was statistically higher than the high-dose (1.33-fold) and MF59-adjuvanted (1.43-fold) recipient ratios. Enhanced vaccines also resulted in the boosting of T-cell responses. CONCLUSIONS: In this head-to-head comparison, older adults receiving enhanced vaccines showed improved humoral and cell-mediated immune responses, compared to standard-dose vaccine recipients. CLINICAL TRIALS REGISTRATION: NCT03330132. |
Examination of classified rock dust (treated and untreated) performance in a 20-L explosion chamber
Perera IE , Harris ML , Sapko ML . J Loss Prev Process Ind 2019 62 Mine explosions are caused by the ignition of excessive accumulations of combustible dust and/or flammable gas mixed with air in the presence of an ignition source. Rock dusting (limestone dust) is a primary measure to prevent propagating coal dust explosions in underground coal mines in the United States. Although rock dust is considered a nuisance dust, Continuous Personal Dust Monitors (CPDMs) do not distinguish between the coal dust and rock dust and assess the total dust exposure. During application, the <10 μm limestone particles and coal dust particles can become suspended and carried by the ventilating air for long distances and can be measured by the CPDMs. There is a concern in the mining industry that rock dust can be included in the CPDM measurements and make the samples noncompliant. Research conducted by the National Institute for Occupational Safety and Health (NIOSH) has found that all rock dust (RD) cakes after being wetted and then dried. To prevent rock dust from caking, several rock dust manufacturers have developed anti-caking rock dusts. The anti-caking additives used are typically fatty acids that make the rock dust hydrophobic and are added in very low quantities (<1%). While this development will add to the rock dust fluidity, an inevitable problem may be the increased airborne re-entrainment of rock dust due to vehicle movement and foot traffic in the area. Thus, one consideration to reduce such exposure from rock dust is to remove the respirable size fraction (<10 μm) of the applied rock dust. This paper presents the results of experiments that were conducted to determine if a rock dust can still inert a coal dust explosion when the respirable (<10 μm) or inhalable (<20 μm) component of the particle size distribution is removed. Three different untreated rock dusts (untreated A, B, and C) with their treated counterparts (treated A, B, and C) were classified using mechanical sieves into several different-sized fractions, including < 10, 10–20, 20–38, 38–53 and > 75 μm. The relative inerting effectiveness of these size fractions were determined using the United States Bureau of Mines (USBM) 20-L explosion chamber. |
Factors affecting the performance of trickle dusters for preventing explosive dust accumulations in return airways
Sapko MJ , Harris ML , Perera IE , Zlochower IA , Weiss ES . J Loss Prev Process Ind 2019 61 1-7 Correctly applied rock dust can dilute, inert, and mitigate the explosive potential of float coal dust. Trickle dusters are one element of a comprehensive system to help prevent coal dust explosions in underground coal mines. Trickle dusters supply rock dust to inert fine float coal dust in areas where it is commonly deposited, such as the longwall tailgate returns, return airways, pillaring areas, and downwind of belt transfers. Dust deposition studies show that the effectiveness of trickle dusters depends on several key factors. Using multiple orifices, rock dust should be released near the mine roof in the direction of the airflow in order to spread the cloud cross the entry. The rock duster should have a mechanism to break up rock dust agglomerates as they leave the rock duster. The particle size distribution of the limestone rock dust and its airborne concentration should be proportional to the airborne size distribution and concentration of coal dust passing by the trickle duster. Specifically, rock dusts having a greater proportion of <74 microm material are more effective at minimizing downwind zones of explosible mixtures than mostly larger particles. In our testing, rock dusts having more than 95% of <74 microm sized particles were adequately dispersed by trickle dusters. Based on our results, the mass rate of rock dust discharge from the trickle duster should exceed the rate of float coal production by at least a factor of four in order to minimize accumulations of explosible dusts. |
Metabolomic Insights into Human Arboviral Infections: Dengue, Chikungunya, and Zika Viruses.
Byers NM , Fleshman AC , Perera R , Molins CR . Viruses 2019 11 (3) The global burden of arboviral diseases and the limited success in controlling them calls for innovative methods to understand arbovirus infections. Metabolomics has been applied to detect alterations in host physiology during infection. This approach relies on mass spectrometry or nuclear magnetic resonance spectroscopy to evaluate how perturbations in biological systems alter metabolic pathways, allowing for differentiation of closely related conditions. Because viruses heavily depend on host resources and pathways, they present unique challenges for characterizing metabolic changes. Here, we review the literature on metabolomics of arboviruses and focus on the interpretation of identified molecular features. Metabolomics has revealed biomarkers that differentiate disease states and outcomes, and has shown similarities in metabolic alterations caused by different viruses (e.g., lipid metabolism). Researchers investigating such metabolomic alterations aim to better understand host(-)virus dynamics, identify diagnostically useful molecular features, discern perturbed pathways for therapeutics, and guide further biochemical research. This review focuses on lessons derived from metabolomics studies on samples from arbovirus-infected humans. |
Associations between prenatal and childhood PBDE exposure and early adolescent visual, verbal and working memory
Cowell WJ , Margolis A , Rauh VA , Sjodin A , Jones R , Wang Y , Garcia W , Perera F , Wang S , Herbstman JB . Environ Int 2018 118 9-16 BACKGROUND: Prenatal and childhood exposure to polybrominated diphenyl ether (PBDE) flame retardants has been inversely associated with cognitive performance, however, few studies have measured PBDE concentrations in samples collected during both prenatal and postnatal periods. METHODS: We examined prenatal (cord) and childhood (ages 2, 3, 5, 7 and 9years) plasma PBDE concentrations in relation to memory outcomes assessed between the ages of 9 and 14years. The study sample includes a subset (n=212) of the African American and Dominican children enrolled in the Columbia Center for Children's Environmental Health Mothers and Newborns birth cohort. We used multivariable linear regression to examine associations between continuous log10-transformed PBDE concentrations and performance on tests of visual, verbal and working memory in age-stratified models. We additionally used latent class growth analysis to estimate trajectories of exposure across early life, which we analyzed as a categorical variable in relation to memory outcomes. We examined interactions between PBDE exposure and sex using cross-product terms. RESULTS: Associations between prenatal exposure and working memory significantly varied by sex (p-interaction=0.02), with inverse relations observed only among girls (i.e. betaBDE-47=-7.55, 95% CI: -13.84, -1.24). Children with sustained high concentrations of BDEs-47, 99 or 100 across childhood scored approximately 5-8 standard score points lower on tests of visual memory. Children with PBDE plasma concentrations that peaked during toddler years performed better on verbal domains, however, these associations were not statistically significant. CONCLUSIONS: Exposure to PBDEs during both prenatal and postnatal periods may disrupt memory domains in early adolescence. These findings contribute to a substantial body of evidence supporting the developmental neurotoxicity of PBDEs and underscore the need to reduce exposure among pregnant women and children. |
Influence of specific surface area on coal dust explosibility using the 20-L chamber
Zlochower IA , Sapko MJ , Perera IE , Brown CB , Harris ML , Rayyan NS . J Loss Prev Process Ind 2018 54 103-109 The relationship between the explosion inerting effectiveness of rock dusts on coal dusts, as a function of the specific surface area (cm2/g) of each component is examined through the use of 20-L explosion chamber testing. More specifically, a linear relationship is demonstrated for the rock dust to coal dust (or incombustible to combustible) content of such inerted mixtures with the specific surface area of the coal and the inverse of that area of the rock dust. Hence, the inerting effectiveness, defined as above, is more generally linearly dependent on the ratio of the two surface areas. The focus on specific surface areas, particularly of the rock dust, provide supporting data for minimum surface area requirements in addition to the 70% less than 200 mesh requirement specified in 30 CFR 75.2. © 2018 |
House screening with insecticide-treated netting provides sustained reductions in domestic populations of Aedes aegypti in Merida, Mexico
Che-Mendoza A , Medina-Barreiro A , Koyoc-Cardena E , Uc-Puc V , Contreras-Perera Y , Herrera-Bojorquez J , Dzul-Manzanilla F , Correa-Morales F , Ranson H , Lenhart A , McCall PJ , Kroeger A , Vazquez-Prokopec G , Manrique-Saide P . PLoS Negl Trop Dis 2018 12 (3) e0006283 BACKGROUND: There is a need for effective methods to control Aedes aegypti and prevent the transmission of dengue, chikungunya, yellow fever and Zika viruses. Insecticide treated screening (ITS) is a promising approach, particularly as it targets adult mosquitoes to reduce human-mosquito contact. METHODOLOGY/PRINCIPAL FINDINGS: A cluster-randomised controlled trial evaluated the entomological efficacy of ITS based intervention, which consisted of the installation of pyrethroid-impregnated long-lasting insecticide-treated netting material fixed as framed screens on external doors and windows. A total of 10 treatment and 10 control clusters (100 houses/cluster) were distributed throughout the city of Merida, Mexico. Cross-sectional entomological surveys quantified indoor adult mosquito infestation at baseline (pre-intervention) and throughout four post-intervention (PI) surveys spaced at 6-month intervals corresponding to dry/rainy seasons over two years (2012-2014). A total of 844 households from intervention clusters (86% coverage) were protected with ITS at the start of the trial. Significant reductions in the indoor presence and abundance of Ae. aegypti adults (OR = 0.48 and IRR = 0.45, P<0.05 respectively) and the indoor presence and abundance of Ae. aegypti female mosquitoes (OR = 0.47 and IRR = 0.44, P<0.05 respectively) were detected in intervention clusters compared to controls. This high level of protective effect was sustained for up to 24 months PI. Insecticidal activity of the ITS material declined with time, with ~70% mortality being demonstrated in susceptible mosquito cohorts up to 24 months after installation. CONCLUSIONS/SIGNIFICANCE: The strong and sustained entomological impact observed in this study demonstrates the potential of house screening as a feasible, alternative approach to a sustained long-term impact on household infestations of Ae. aegypti. Larger trials quantifying the effectiveness of ITS on epidemiological endpoints are warranted and therefore recommended. |
Some relevant parameters for assessing fire hazards of combustible mine materials using laboratory scale experiments
Litton CD , Perera IE , Harteis SP , Teacoach KA , DeRosa MI , Thomas RA , Smith AC . Fuel (Lond) 2018 218 306-315 When combustible materials ignite and burn, the potential for fire growth and flame spread represents an obvious hazard, but during these processes of ignition and flaming, other life hazards present themselves and should be included to ensure an effective overall analysis of the relevant fire hazards. In particular, the gases and smoke produced both during the smoldering stages of fires leading to ignition and during the advanced flaming stages of a developing fire serve to contaminate the surrounding atmosphere, potentially producing elevated levels of toxicity and high levels of smoke obscuration that render the environment untenable. In underground mines, these hazards may be exacerbated by the existing forced ventilation that can carry the gases and smoke to locations far-removed from the fire location. Clearly, materials that require high temperatures (above 1400 K) and that exhibit low mass loss during thermal decomposition, or that require high heat fluxes or heat transfer rates to ignite represent less of a hazard than materials that decompose at low temperatures or ignite at low levels of heat flux. In order to define and quantify some possible parameters that can be used to assess these hazards, small-scale laboratory experiments were conducted in a number of configurations to measure: 1) the toxic gases and smoke produced both during non-flaming and flaming combustion; 2) mass loss rates as a function of temperature to determine ease of thermal decomposition; and 3) mass loss rates and times to ignition as a function of incident heat flux. This paper describes the experiments that were conducted, their results, and the development of a set of parameters that could possibly be used to assess the overall fire hazard of combustible materials using small scale laboratory experiments. |
Rapid and specific detection of Asian- and African-lineage Zika viruses.
Chotiwan N , Brewster CD , Magalhaes T , Weger-Lucarelli J , Duggal NK , Ruckert C , Nguyen C , Garcia Luna SM , Fauver JR , Andre B , Gray M , Black WCth , Kading RC , Ebel GD , Kuan G , Balmaseda A , Jaenisch T , Marques ETA , Brault AC , Harris E , Foy BD , Quackenbush SL , Perera R , Rovnak J . Sci Transl Med 2017 9 (388) Understanding the dynamics of Zika virus transmission and formulating rational strategies for its control require precise diagnostic tools that are also appropriate for resource-poor environments. We have developed a rapid and sensitive loop-mediated isothermal amplification (LAMP) assay that distinguishes Zika viruses of Asian and African lineages. The assay does not detect chikungunya virus or flaviviruses such as dengue, yellow fever, or West Nile viruses. The assay conditions allowed direct detection of Zika virus RNA in cultured infected cells; in mosquitoes; in virus-spiked samples of human blood, plasma, saliva, urine, and semen; and in infected patient serum, plasma, and semen samples without the need for RNA isolation or reverse transcription. The assay offers rapid, specific, sensitive, and inexpensive detection of the Asian-lineage Zika virus strain that is currently circulating in the Western hemisphere, and can also detect the African-lineage Zika virus strain using separate, specific primers. |
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