Last data update: May 06, 2024. (Total: 46732 publications since 2009)
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Query Trace: Mathias D[original query] |
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Ebola Virus Disease Outbreak - Democratic Republic of the Congo, August 2018-November 2019.
Aruna A , Mbala P , Minikulu L , Mukadi D , Bulemfu D , Edidi F , Bulabula J , Tshapenda G , Nsio J , Kitenge R , Mbuyi G , Mwanzembe C , Kombe J , Lubula L , Shako JC , Mossoko M , Mulangu F , Mutombo A , Sana E , Tutu Y , Kabange L , Makengo J , Tshibinkufua F , Ahuka-Mundeke S , Muyembe JJ , Ebola Response CDC , Alarcon Walter , Bonwitt Jesse , Bugli Dante , Bustamante Nirma D , Choi Mary , Dahl Benjamin A , DeCock Kevin , Dismer Amber , Doshi Reena , Dubray Christine , Fitter David , Ghiselli Margherita , Hall Noemi , Hamida Amen Ben , McCollum Andrea M , Neatherlin John , Raghunathan Pratima L , Ravat Fatima , Reynolds Mary G , Rico Adriana , Smith Nailah , Soke Gnakub Norbert , Trudeau Aimee T , Victory Kerton R , Worrell Mary Claire . MMWR Morb Mortal Wkly Rep 2019 68 (50) 1162-1165 On August 1, 2018, the Democratic Republic of the Congo Ministry of Health (DRC MoH) declared the tenth outbreak of Ebola virus disease (Ebola) in DRC, in the North Kivu province in eastern DRC on the border with Uganda, 8 days after another Ebola outbreak was declared over in northwest Équateur province. During mid- to late-July 2018, a cluster of 26 cases of acute hemorrhagic fever, including 20 deaths, was reported in North Kivu province.* Blood specimens from six patients hospitalized in the Mabalako health zone and sent to the Institut National de Recherche Biomédicale (National Biomedical Research Institute) in Kinshasa tested positive for Ebola virus. Genetic sequencing confirmed that the outbreaks in North Kivu and Équateur provinces were unrelated. From North Kivu province, the outbreak spread north to Ituri province, and south to South Kivu province (1). On July 17, 2019, the World Health Organization designated the North Kivu and Ituri outbreak a public health emergency of international concern, based on the geographic spread of the disease to Goma, the capital of North Kivu province, and to Uganda and the challenges to implementing prevention and control measures specific to this region (2). This report describes the outbreak in the North Kivu and Ituri provinces. As of November 17, 2019, a total of 3,296 Ebola cases and 2,196 (67%) deaths were reported, making this the second largest documented outbreak after the 2014-2016 epidemic in West Africa, which resulted in 28,600 cases and 11,325 deaths.(†) Since August 2018, DRC MoH has been collaborating with partners, including the World Health Organization, the United Nations Children's Fund, the United Nations Office for the Coordination of Humanitarian Affairs, the International Organization of Migration, The Alliance for International Medical Action (ALIMA), Médecins Sans Frontières, DRC Red Cross National Society, and CDC, to control the outbreak. Enhanced communication and effective community engagement, timing of interventions during periods of relative stability, and intensive training of local residents to manage response activities with periodic supervision by national and international personnel are needed to end the outbreak. |
Respiratory Viral Infections and Infection Prevention Practices among Women with Acute Respiratory Illness during Delivery Hospitalizations during the 2019-2020 Influenza Season
Dawood FS , Varner M , Munoz F , Stockwell MS , Suyama J , Li DK , Tita A , Mathias L , Shakib JH , Piedra PA , Gyamfi-Bannerman C , Weissman A , Ferber J , Battarbee AN , Wesley MG , Vorwaller K , Powers E , Gibson M , Bond N , Santarcangelo P , Avadhanula V , Newes-Adeyi G , Hunt DR , Subramaniam A , Sanusi A , Boone A , Ogokeh C , Macio I , Odouli R , Thind P , Vargas CY , Almonte C , Galang R , Shapiro-Mendoza C , Campbell AP . J Infect Dis 2021 225 (1) 50-54 We conducted a cross-sectional study of pregnant women with acute respiratory illness during delivery hospitalizations in influenza season to describe clinical testing for respiratory viruses and infection prevention practices. Women had nasal swabs tested for influenza and other respiratory viruses. Among 91 enrolled women, 22 (24%) had clinical testing for influenza. Based on clinical and study testing combined, 41/91 (45%) women had samples positive for respiratory viruses. The most common virus was influenza (17/91, 19%); 53% (9/17) of influenza virus infections were identified through study testing alone. Only 16% of women were on droplet precautions. Peripartum respiratory infections may be underrecognized. |
Efficacy of extended release formulations of Natular (spinosad) against larvae and adults of Anopheles mosquitoes in western Kenya
Gimnig JE , Ombok M , Bayoh N , Mathias D , Ochomo E , Jany W , Walker ED . Malar J 2020 19 (1) 436 BACKGROUND: Larval source management is recommended as a supplementary vector control measure for the prevention of malaria. Among the concerns related to larviciding is the feasibility of implementation in tropical areas with large numbers of habitats and the need for frequent application. Formulated products of spinosad that are designed to be effective for several weeks may mitigate some of these concerns. METHODS: In a semi-field study, three formulations of spinosad (emulsifiable concentrate, extended release granules and tablet formulations) were tested in naturalistic habitats in comparison to an untreated control. Cohorts of third instar Anopheles gambiae (Diptera: Culicidae) were introduced into the habitats in screened cages every week up to four weeks after application and monitored for survivorship over three days. A small-scale field trial was then conducted in two villages. Two of the spinosad formulations were applied in one village over the course of 18 months. Immature mosquito populations were monitored with standard dippers in sentinel sites and adult populations were monitored by pyrethrum spray catches. RESULTS: In the semi-field study, the efficacy of the emulsifiable concentrate of spinosad waned 1 week after treatment. Mortality in habitats treated with the extended release granular formulation of spinosad was initially high but declined gradually over 4 weeks while mortality in habitats treated with the dispersable tablet formulation was low immediately after treatment but rose to 100% through four weeks. In the field study, immature and adult Anopheles mosquito populations were significantly lower in the intervention village compared to the control village during the larviciding period. Numbers of collected mosquitoes were lower in the intervention village compared to the control village during the post-intervention period but the difference was not statistically significant. CONCLUSIONS: The extended release granular formulation and the dispersible tablet formulations of spinosad are effective against larval Anopheles mosquitoes for up to four weeks and may be an effective tool as part of larval source management programmes for reducing adult mosquito density and malaria transmission. |
Survey of guidelines and current practices for safe handling of antineoplastic and other hazardous drugs used in 24 countries
Mathias PI , MacKenzie BA , Toennis CA , Connor TH . J Oncol Pharm Pract 2017 25 (1) 1078155217726160 Purpose A survey of guidelines and current practices was conducted to examine the safe handling procedures for antineoplastic and other hazardous drugs that are used in 24 countries including the Americas, Europe, the Mideast, Far East, and Australia. Methods Subject experts were asked to complete a brief survey regarding safe handling guidelines and practices for hazardous drugs in their countries. Questions addressed practices for handling monoclonal antibodies, the use of closed-system transfer devices, medical surveillance practices, and measurements of compliance with existing guidelines. Results Responses from 37 subject experts representing 24 countries revealed considerable variation in the content and scope of safe handling guidelines and pharmacy practices among the participating countries. Guidelines in the majority of countries used the term "cytotoxics," while others referred to "hazardous" or "antineoplastic" drugs. The International Society of Oncology Pharmacy Practice standard was cited by six countries, and five cited the National Institute for Occupational Safety and Health Alert. Others cited international guidelines other than International Society of Oncology Pharmacy Practice, or they have created their own guidelines. Approximately half reported that their guidelines were mandatory under federal, state, or provincial legislation. Only 11 countries reported that monoclonal antibodies were covered in their guidelines. Closed-system drug-transfer devices are widely used, but were not specifically recommended in four countries, while one country required their use. Medical surveillance programs are in place in 20 countries, but only in The Netherlands is surveillance mandatory. Nine countries reported that they have completed recent updates or revisions of guidelines, and the measures for their adoption have been initiated. Conclusions Although the overall goals in the participating countries were similar, the approaches taken to assure safe handling of hazardous drugs varied considerably in some cases. |
An American Thoracic Society/National Heart, Lung, and Blood Institute Workshop Report: Addressing respiratory health equality in the United States
Celedon JC , Burchard EG , Schraufnagel D , Castillo-Salgado C , Schenker M , Balmes J , Neptune E , Cummings KJ , Holguin F , Riekert KA , Wisnivesky JP , Garcia JGN , Roman J , Kittles R , Ortega VE , Redline S , Mathias R , Thomas A , Samet J , Ford JG . Ann Am Thorac Soc 2017 14 (5) 814-826 Health disparities related to race, ethnicity, and socioeconomic status persist and are commonly encountered by practitioners of pediatric and adult pulmonary, critical care, and sleep medicine in the United States. To address such disparities and thus progress toward equality in respiratory health, the American Thoracic Society and the National Heart, Lung, and Blood Institute convened a workshop in May of 2015. The workshop participants addressed health disparities by focusing on six topics, each of which concluded with a panel discussion that proposed recommendations for research on racial, ethnic, and socioeconomic disparities in pulmonary, critical care, and sleep medicine. Such recommendations address best practices to advance research on respiratory health disparities (e.g., characterize broad ethnic groups into subgroups known to differ with regard to a disease of interest), risk factors for respiratory health disparities (e.g., study the impact of new tobacco or nicotine products on respiratory diseases in minority populations), addressing equity in access to healthcare and quality of care (e.g., conduct longitudinal studies of the impact of the Affordable Care Act on respiratory and sleep disorders), the impact of personalized medicine on disparities research (e.g., implement large studies of pharmacogenetics in minority populations), improving design and methodology for research studies in respiratory health disparities (e.g., use study designs that reduce participants' burden and foster trust by engaging participants as decision-makers), and achieving equity in the pulmonary, critical care, and sleep medicine workforce (e.g., develop and maintain robust mentoring programs for junior faculty, including local and external mentors). Addressing these research needs should advance efforts to reduce, and potentially eliminate, respiratory, sleep, and critical care disparities in the United States. |
A review of high performance liquid chromatographic-mass spectrometric urinary methods for anticancer drug exposure of health care workers
Mathias PI , Connor TH , B'Hymer C . J Chromatogr B Analyt Technol Biomed Life Sci 2017 1060 316-324 This review describes published high performance liquid chromatography/mass spectrometry (HPLC-MS) methods for the determination of anticancer drugs in human urine as non-invasive tool for monitoring of health care worker exposure to antineoplastic and cytotoxic drugs. HPLC-MS is a sensitive and specific method for analysis of anticancer drugs and their metabolites in biological fluids. In this review, a tabular summary and overview of published HPLC-MS methods are presented, as well as future trends and limitations in this area of research. |
Comparison of norovirus genogroup I, II and IV seroprevalence among children in the Netherlands, 1963, 1983 and 2006.
van Beek J , de Graaf M , Xia M , Jiang X , Vinje J , Beersma M , de Bruin E , van de Vijver D , Holwerda M , van Houten M , Buisman AM , van Binnendijk R , Osterhaus AD , van der Klis F , Vennema H , Koopmans MP . J Gen Virol 2016 97 (9) 2255-64 Noroviruses are a major cause of acute gastroenteritis worldwide and are a genetically diverse group of viruses. Since 2002, an increasing number of norovirus outbreaks have been reported globally, but it is not clear whether this increase has been caused by a higher awareness or reflects the emergence of new genogroup II genotype 4 (GII.4) variants. The hypothesis that norovirus prevalence has increased post-2002 and is related to the emergence of GII.4 is tested in this study. Sera collected from children aged <5 years of three Dutch cross-sectional population based cohorts in 1963, 1983 and 2006/2007 (n=143, n=130 and n=376, respectively) were tested for specific serum IgG by protein array using antigens to GII.4 and a range of other antigens representing norovirus GI, GII and GIV genotypes. The protein array was validated by paired sera of norovirus infected patients and supernatants of B-cell cultures with single epitope specificity. Evidence for norovirus infection was found to be common among Dutch children in each cohort, but the prevalence towards different genotypes changed over time. At the genogroup level, GI seroprevalence decreased significantly between 1963 and 2006/2007, while a significant increase of GII and, in particular, specific antibodies of the genotype GII.4 was detected in the 2006/2007 cohort. There were no children with only GII.4 antibodies in the 1963 cohort. This study shows that the high GII.4 norovirus incidence in very young children is a recent phenomenon. These findings are of importance for vaccine development and trials that are currently focusing mostly on GII.4 viruses. |
Mercapturic acids: recent advances in their determination by liquid chromatography/mass spectrometry and their use in toxicant metabolism studies and in occupational and environmental exposure studies
Mathias PI , B'Hymer C . Biomarkers 2016 21 (4) 1-23 This review describes recent selected HPLC/MS methods for the determination of urinary mercapturates that are useful as noninvasive biomarkers in characterizing human exposure to electrophilic industrial chemicals in occupational and environmental studies. High-performance liquid chromatography/mass spectrometry is a sensitive and specific method for analysis of small molecules found in biological fluids. In this review, recent selected mercapturate quantification methods are summarized and specific cases are presented. The biological formation of mercapturates is introduced and their use as indicators of metabolic processing of reactive toxicants is discussed, as well as future trends and limitations in this area of research. |
Telomere Length as an Indicator of the Robustness of B- and T-Cell Response to Influenza in Older Adults.
Najarro K , Nguyen H , Chen G , Xu M , Alcorta S , Yao X , Zukley L , Metter EJ , Truong T , Lin Y , Li H , Oelke M , Xu X , Ling SM , Longo DL , Schneck J , Leng S , Ferrucci L , Weng NP . J Infect Dis 2015 212 (8) 1261-9 BACKGROUND: Telomeres provide a key mechanism for protecting the integrity of chromosomes and their attrition after cell division and during aging are evident in lymphocytes. However, the significance of telomere shortening in age-associated decline of immune function is unknown. METHODS: We selected 22 HLA-A2+ healthy older adults who have relatively short or long telomere lengths to compare their antibody response against the influenza vaccine, and their CD8+ T cell response against an influenza antigen. RESULTS: B cells from individuals with a robust antibody response to the influenza vaccine had significantly longer telomeres than those with a poor antibody response. Monocyte-derived antigen-presenting cells of both short and long telomere groups induced similar expansions of influenza M1-specific CD8+ T cells. Vaccination did not increase M1-specific CD8+ T cells in blood, however, M1-specific CD8+ T cells from the long telomere group exhibited significantly better expansion in vitro compared to those from the short telomere group. Finally, M1-specific CD8+ T cells that underwent more expansions had significantly longer telomeres compared to cells with fewer divisions. CONCLUSIONS: Telomere length is positively associated with a robust lymphocyte response and telomere attrition may contribute to the age-associated decline of adaptive immunity. |
Spot the difference-development of a syndrome based protein microarray for specific serological detection of multiple flavivirus infections in travelers.
Cleton NB , Godeke GJ , Reimerink J , Beersma MF , Doorn HR , Franco L , Goeijenbier M , Jimenez-Clavero MA , Johnson BW , Niedrig M , Papa A , Sambri V , Tami A , Velasco-Salas ZI , Koopmans MP , Reusken CB . PLoS Negl Trop Dis 2015 9 (3) e0003580 BACKGROUND: The family Flaviviridae, genus Flavivirus, holds many of the world's most prevalent arboviral diseases that are also considered the most important travel related arboviral infections. In most cases, flavivirus diagnosis in travelers is primarily based on serology as viremia is often low and typically has already been reduced to undetectable levels when symptoms set in and patients seek medical attention. Serological differentiation between flaviviruses and the false-positive results caused by vaccination and cross-reactivity among the different species, are problematic for surveillance and diagnostics of flaviviruses. Their partially overlapping geographic distribution and symptoms, combined with increase in travel, and preexisting antibodies due to flavivirus vaccinations, expand the need for rapid and reliable multiplex diagnostic tests to supplement currently used methods. GOAL: We describe the development of a multiplex serological protein microarray using recombinant NS1 proteins for detection of medically important viruses within the genus Flavivirus. Sera from clinical flavivirus patients were used for primary development of the protein microarray. RESULTS: Results show a high IgG and IgM sensitivity and specificity for individual NS1 antigens, and limited cross reactivity, even within serocomplexes. In addition, the serology based on this array allows for discrimination between infection and vaccination response for JEV vaccine, and no cross-reactivity with TBEV and YFV vaccine induced antibodies when testing for antibodies to other flaviviruses. CONCLUSION: Based on these data, multiplex NS1-based protein microarray is a promising tool for surveillance and diagnosis of flaviviruses. |
A survey of liquid chromatographic-mass spectrometric analysis of mercapturic acid biomarkers in occupational and environmental exposure monitoring
Mathias PI , B'Hymer C . J Chromatogr B Analyt Technol Biomed Life Sci 2014 964 136-45 High-performance liquid chromatography/mass spectrometry (HPLC/MS) is sensitive and specific for targeted quantitative analysis and is readily utilized for small molecules from biological matrices. This brief review describes recent selected HPLC/MS methods for the determination of urinary mercapturic acids (mercapturates) which are useful as biomarkers in characterizing human exposure to electrophilic industrial chemicals in occupational and environmental studies. Electrophilic compounds owing to their reactivity are used in chemical and industrial processes. They are present in industrial emissions, are combustion products of fossil fuels, and are components in tobacco smoke. Their presence in both the industrial and general environments are of concern for human and environmental health. Urinary mercapturates which are the products of metabolic detoxification of reactive chemicals provide a non-invasive tool to investigate human exposure to electrophilic toxicants. Selected recent mercapturate quantification methods are summarized and specific cases are presented. The biological formation of mercapturates is introduced and their use as biomarkers of metabolic processing of electrophilic compounds is discussed. Also, the use of liquid chromatography/tandem mass spectrometry in simultaneous determinations of the mercapturates of multiple parent compounds in a single determination is considered, as well as future trends and limitations in this area of research. |
Detection of DNA damage in workers exposed to JP-8 jet fuel
Krieg Jr EF , Mathias PI , Toennis CA , Clark JC , Marlow KL , B'Hymer C , Singh NP , Gibson RL , Butler MA . Mutat Res 2012 747 (2) 218-27 The genotoxicity of jet propulsion fuel 8 (JP-8) was assessed in the leukocytes of archived blood specimens from U.S. Air Force personnel using the comet assay. No differences in mean comet assay measurements were found between low, moderate, and high exposure groups before or after a 4hour work shift. Before the work shift, mean tail DNA and mean tail (Olive) moment increased as the concentration of benzene measured in end-exhaled breath increased, indicating that prior environmental or work-related exposures to benzene produced DNA damage. The number of cells with highly damaged DNA decreased as the pre-shift benzene concentration in breath increased. It is not clear why the decrease is occurring. Mean tail DNA and mean tail (Olive) moment decreased as the concentrations of benzene and naphthalene measured in breath immediately after the work shift increased. These inverse relationships may reflect a slower rate of absorption or a faster rate of expiration of benzene in the lung. The number of cells with highly damaged DNA increased as the concentration of urinary (2-methoxyethoxy)acetic acid (MEAA) increased. This relationship was not seen in urinary MEAA adjusted for creatinine. MEAA is a metabolite of the deicing agent 2-(2-methoxyethoxy)ethanol contained in JP-8. MEAA or a component of JP-8 correlated with MEAA may have a toxic effect on DNA. |
Comparison and evaluation of urinary biomarkers for occupational exposure to spray adhesives containing 1- bromopropane
Mathias PI , Cheever KL , Hanley KW , Marlow KL , Johnson BC , B'Hymer C . Toxicol Mech Methods 2012 22 (7) 526-32 Three metabolites of 1-bromopropane (1-BP) were measured in urine samples collected from 30 workers exposed to 1-BP at two facilities making furniture seat cushions and evaluated for use as biomarkers of exposure. The mercapturic acid metabolite,N-acetyl-S-(n-propyl)-L-cysteine (AcPrCys), 3-bromopropionic acid (3-BPA), and bromide ion levels (Br(-)) were quantitated for this evaluation. The high exposure group consisted of 13 workers employed as adhesive sprayers who assembled foam cushions using 1-BP containing spray adhesives and the low exposure group consisted of 17 non-sprayers, who worked in various jobs without spraying adhesives. All workers' urine voids were collected over the same 48 hour period at work, and at home before bedtime, and upon awakening. Urinary AcPrCys and Br(-)levels were elevated in the sprayers compared to that ofnon-sprayers. Following HPLC-MS/MS analysis of mercapturic acid metabolite levels, 50 urine samples having the highest levels of AcPrCys were analyzed for 3-BPA. No 3-BPA was detected in any of the samples. The data collected from this study demonstrate that ACPrCys and Br(-) are effective biomarkers of 1-BP exposure, but 3-BPA is not. |
Evaluation of surface-enhanced laser desorption time-of-flight mass spectroscopy in the development of biomarkers of occupational acrylamide exposure
Mathias PI , Cheever KL . Am Lab 2011 43 (11) 34-+ Surface-enhanced laser desorption time-of-flight mass spectroscopy (SELDI-TOF-MS) is a bioanalytical technique used for the rapid examination of intact protein or protein mixtures to exploit the biochemical or biophysical characteristics of intact molecules to separate a complex protein mixture or isolate specific protein classes. Surface-enhanced laser desorption time-of-flight mass spectroscopy allows for rapid examination of protein components of body fluids or cell lysates without extensive extraction or preparative measures. The levels and composition of proteins found in blood and urine may change after exposure to toxic agents.1,2 Such potential changes make the proteins found in these easily obtained fluids a desirable source of new or altered proteins that indicate toxic exposure. This article describes the use of SELDI-TOF to examine urinary proteins or hemoglobin present in erythrocyte lysates. | Acrylamide is a widely used industrial chemical intermediate with many applications,3 such as a polymerizing agent in grouts and in the preparation of laboratory gels for protein and nucleic acid electrophoresis. Low levels of acrylamide present in baked, fried, and roasted foods and in tobacco smoke are common sources of human exposure.4 Acrylamide is a potent neurotoxin5 and is a probable human carcinogen that makes exposure a concern for human health.6 |
(2-Methoxyethoxy)acetic acid: a urinary biomarker of exposure for jet fuel JP-8
B'Hymer C , Mathias P , Krieg E Jr , Cheever KL , Toennis CA , Clark JC , Kesner JS , Gibson RL , Butler MA . Int Arch Occup Environ Health 2011 85 (4) 413-20 PURPOSE: To demonstrate the utility of the urinary metabolite (2-methoxyethoxy)acetic acid (MEAA) as a biomarker of exposure. 2-(2-methoxyethoxy)ethanol [diethylene glycol monomethyl ether] is an anti-icing agent used in the formulation of JP-8, and it is added at a known uniform 0.1% (v/v) concentration to each batch lot. JP-8 is a kerosene-based fuel containing different compounds that vary in the content of every batch/lot of fuel; thus, MEAA has the potential to be a more specific and a consistent quantitative biomarker for JP-8 exposure. METHODS: MEAA was used to measure exposure of jet propulsion fuel 8 (JP-8) in United States Air Force (USAF) personnel working at six airbases within the United States. Post-shift urine specimens from various personnel including high (n = 98), moderate (n = 38), and low (n = 61) exposure workgroup categories were collected and analyzed by a gas chromatographic-mass spectrometric test method. The three exposure groups were evaluated for the number per group positive for MEAA, and a statistical analysis consisted of pair-wise t-tests for unequal variances was used to test for the differences in mean MEAA concentrations between the exposure groups. RESULTS: The number of samples detected as positive for MEAA exposure, that is, those above the test method's limit of detection (LOD = 0.1 mcg/ml), were 92 (93.9%), 13 (34.2%), and 2 (3.3%) for the high, moderate, and low exposure workgroup categories, respectively. The mean urinary MEAA level was significantly greater in the high exposure category (6.8 mcg/ml), compared to the moderate (0.42 mcg/ml) and the low (0.07 mcg/ml) exposure categories. The maximum concentration of urinary MEAA was 110 mcg/ml for the high exposure category, while 4.8 mcg/ml and 0.2 mcg/ml maximum levels were found in the moderate and low exposure categories, respectively. CONCLUSION: This study demonstrated that urinary MEAA can be used as an accurate biomarker of exposure for JP-8 workers and clearly distinguished the differences in JP-8 exposure by workgroup category. |
Spatial and temporal variation in the kdr allele L1014S in Anopheles gambiae s.s. and phenotypic variability in susceptibility to insecticides in Western Kenya
Mathias DK , Ochomo E , Atieli F , Ombok M , Bayoh MN , Olang G , Muhia D , Kamau L , Vulule JM , Hamel MJ , Hawley WA , Walker ED , Gimnig JE . Malar J 2011 10 (1) 10 BACKGROUND: Malaria vector control in Africa depends upon effective insecticides in bed nets and indoor residual sprays. This study investigated the extent of insecticide resistance in Anopheles gambiae s.l., Anopheles gambiae s.s. and Anopheles arabiensis in western Kenya where ownership of insecticide-treated bed nets has risen steadily from the late 1990s to 2010. Temporal and spatial variation in the frequency of a knock down resistance (kdr) allele in A. gambiae s.s. was quantified, as was variation in phenotypic resistance among geographic populations of A. gambiae s.l. METHODS: To investigate temporal variation in kdr frequency, individual specimens of A. gambiae s.s. from two sentinel sites were genotyped using RT-PCR from 1996-2010. Spatial variation in kdr frequency, species composition, and resistance status were investigated in additional populations of A. gambiae s.l. sampled in western Kenya in 2009 and 2010. Specimens were genotyped for kdr as above and identified to species via conventional PCR. Field-collected larvae were reared to adulthood and tested for insecticide resistance using WHO bioassays. RESULTS: Anopheles gambiae s.s. showed a dramatic increase in kdr frequency from 1996 - 2010, coincident with the scale up of insecticide-treated nets. By 2009-2010, the kdr L1014S allele was nearly fixed in the A. gambiae s.s. population, but was absent in A. arabiensis. Near Lake Victoria, A. arabiensis was dominant in samples, while at sites north of the lake A. gambiae s.s was more common but declined relative to A. arabiensis from 2009 to 2010. Bioassays demonstrated that A. gambiae s.s. had moderate phenotypic levels of resistance to DDT, permethrin and deltamethrin while A. arabiensis was susceptible to all insecticides tested. CONCLUSIONS: The kdr L1014S allele has approached fixation in A. gambiae s.s. populations of western Kenya, and these same populations exhibit varying degrees of phenotypic resistance to DDT and pyrethroid insecticides. The near absence of A. gambiae s.s. from populations along the lakeshore and the apparent decline in other populations suggest that insecticide-treated nets remain effective against this mosquito despite the increase in kdr allele frequency. The persistence of A. arabiensis, despite little or no detectable insecticide resistance, is likely due to behavioural traits such as outdoor feeding and/or feeding on non-human hosts by which this species avoids interaction with insecticide-treated nets. |
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