Last data update: May 13, 2024. (Total: 46773 publications since 2009)
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Tropical data: Approach and methodology as applied to trachoma prevalence surveys
Harding-Esch EM , Burgert-Brucker CR , Jimenez C , Bakhtiari A , Willis R , Bejiga MD , Mpyet C , Ngondi J , Boyd S , Abdala M , Abdou A , Adamu Y , Alemayehu A , Alemayehu W , Al-Khatib T , Apadinuwe SC , Awaca N , Awoussi MS , Baayendag G , Badiane MD , Bailey RL , Batcho W , Bay Z , Bella A , Beido N , Bol YY , Bougouma C , Brady CJ , Bucumi V , Butcher R , Cakacaka R , Cama A , Camara M , Cassama E , Chaora SG , Chebbi AC , Chisambi AB , Chu B , Conteh A , Coulibaly SM , Courtright P , Dalmar A , Dat TM , Davids T , Djaker MEA , de Fátima Costa Lopes M , Dézoumbé D , Dodson S , Downs P , Eckman S , Elshafie BE , Elmezoghi M , Elvis AA , Emerson P , Epée EE , Faktaufon D , Fall M , Fassinou A , Fleming F , Flueckiger R , Gamael KK , Garae M , Garap J , Gass K , Gebru G , Gichangi MM , Giorgi E , Goépogui A , Gómez DVF , Gómez Forero DP , Gower EW , Harte A , Henry R , Honorio-Morales HA , Ilako DR , Issifou AAB , Jones E , Kabona G , Kabore M , Kadri B , Kalua K , Kanyi SK , Kebede S , Kebede F , Keenan JD , Kello AB , Khan AA , Khelifi H , Kilangalanga J , Kim SH , Ko R , Lewallen S , Lietman T , Logora MSY , Lopez YA , MacArthur C , Macleod C , Makangila F , Mariko B , Martin DL , Masika M , Massae P , Massangaie M , Matendechero HS , Mathewos T , McCullagh S , Meite A , Mendes EP , Abdi HM , Miller H , Minnih A , Mishra SK , Molefi T , Mosher A , M'Po N , Mugume F , Mukwiza R , Mwale C , Mwatha S , Mwingira U , Nash SD , Nassa C , Negussu N , Nieba C , Noah Noah JC , Nwosu CO , Olobio N , Opon R , Pavluck A , Phiri I , Rainima-Qaniuci M , Renneker KK , Saboyá-Díaz MI , Sakho F , Sanha S , Sarah V , Sarr B , Szwarcwald CL , Shah Salam A , Sharma S , Seife F , Serrano Chavez GM , Sissoko M , Sitoe HM , Sokana O , Tadesse F , Taleo F , Talero SL , Tarfani Y , Tefera A , Tekeraoi R , Tesfazion A , Traina A , Traoré L , Trujillo-Trujillo J , Tukahebwa EM , Vashist P , Wanyama EB , Warusavithana SDP , Watitu TK , West S , Win Y , Woods G , Yajima A , Yaya G , Zecarias A , Zewengiel S , Zoumanigui A , Hooper PJ , Millar T , Rotondo L , Solomon AW . Ophthalmic Epidemiol 2023 30 (6) 544-560 PURPOSE: Population-based prevalence surveys are essential for decision-making on interventions to achieve trachoma elimination as a public health problem. This paper outlines the methodologies of Tropical Data, which supports work to undertake those surveys. METHODS: Tropical Data is a consortium of partners that supports health ministries worldwide to conduct globally standardised prevalence surveys that conform to World Health Organization recommendations. Founding principles are health ministry ownership, partnership and collaboration, and quality assurance and quality control at every step of the survey process. Support covers survey planning, survey design, training, electronic data collection and fieldwork, and data management, analysis and dissemination. Methods are adapted to meet local context and needs. Customisations, operational research and integration of other diseases into routine trachoma surveys have also been supported. RESULTS: Between 29(th) February 2016 and 24(th) April 2023, 3373 trachoma surveys across 50 countries have been supported, resulting in 10,818,502 people being examined for trachoma. CONCLUSION: This health ministry-led, standardised approach, with support from the start to the end of the survey process, has helped all trachoma elimination stakeholders to know where interventions are needed, where interventions can be stopped, and when elimination as a public health problem has been achieved. Flexibility to meet specific country contexts, adaptation to changes in global guidance and adjustments in response to user feedback have facilitated innovation in evidence-based methodologies, and supported health ministries to strive for global disease control targets. |
Seroprevalence to schistosoma soluble egg antigen among nomadic pastoralists residing in Northern Senegal
Seck MC , Badiane AS , Thwing J , Ndiaye M , Diongue K , Ndiaye IM , Diallo MA , Sy M , Gomis JF , Ndiaye T , Gaye A , Lee YM , Secor WE , Ndiaye D , Rogier E . J Parasitol 2023 109 (6) 580-587 Urinary and intestinal schistosomiasis are endemic in Senegal, with prevalence heterogeneous throughout the country. Because of their way of life, nomadic pastoralists are not typically included in epidemiological surveys, and data on the prevalence of schistosomiasis in Senegalese nomadic populations are largely non-existent. The purpose of this study was to determine the seroprevalence of schistosomiasis in Senegalese nomadic pastoralists. A modified snowball sampling survey was conducted among 1,467 nomadic pastoralists aged 6 mo and older in 5 districts in northern Senegal. Dried blood spots from participants of all ages and data regarding demographics were collected to assess IgG antibody responses against Schistosoma mansoni soluble egg antigen (SEA) using a bead-based multiplex assay. Out of 1,467 study subjects, 1,464 (99.8%) provided IgG serological data that cleared quality assurance. Of the participants with appropriate data, 56.6% were male, the median age was 22 yr, and 31.6% were under 15 yr of age. The overall anti-SEA IgG seroprevalence was 19.1% (95% confidence interval [CI]: 17.1-21.1%) with the highest estimates observed in Dagana (35.9%) and the lowest observed in Podor nomadic groups (3.4%). Antibody responses increased significantly with age except for the oldest age groups (>40 yr of age), which saw lower levels of antibody response compared to younger adults. When controlling for age and location by multivariate regression, the male sex was associated with a 2-fold greater odds of anti-SEA IgG seropositivity (aPOR: 2.0; 95% CI: 1.5-2.7). Serosurveys for anti-SEA IgG among nomadic peoples in northern Senegal found a substantial percentage of individuals with evidence for current or previous Schistosoma spp. infection with the highest levels of exposure in the district adjacent to the Diama dam along the Senegal River. With IgG prevalence increased by age except in the older adults, and the male sex significantly associated with seropositivity, these data point toward sex-associated behavioral practices and human environmental modification as risk factors for Schistosoma exposure. |
Malaria surveillance reveals parasite relatedness, signatures of selection, and correlates of transmission across Senegal
Schaffner SF , Badiane A , Khorgade A , Ndiop M , Gomis J , Wong W , Ndiaye YD , Diedhiou Y , Thwing J , Seck MC , Early A , Sy M , Deme A , Diallo MA , Sy N , Sene A , Ndiaye T , Sow D , Dieye B , Ndiaye IM , Gaye A , Ndiaye A , Battle KE , Proctor JL , Bever C , Fall FB , Diallo I , Gaye S , Sene D , Hartl DL , Wirth DF , MacInnis B , Ndiaye D , Volkman SK . Nat Commun 2023 14 (1) 7268 We here analyze data from the first year of an ongoing nationwide program of genetic surveillance of Plasmodium falciparum parasites in Senegal. The analysis is based on 1097 samples collected at health facilities during passive malaria case detection in 2019; it provides a baseline for analyzing parasite genetic metrics as they vary over time and geographic space. The study's goal was to identify genetic metrics that were informative about transmission intensity and other aspects of transmission dynamics, focusing on measures of genetic relatedness between parasites. We found the best genetic proxy for local malaria incidence to be the proportion of polygenomic infections (those with multiple genetically distinct parasites), although this relationship broke down at low incidence. The proportion of related parasites was less correlated with incidence while local genetic diversity was uninformative. The type of relatedness could discriminate local transmission patterns: two nearby areas had similarly high fractions of relatives, but one was dominated by clones and the other by outcrossed relatives. Throughout Senegal, 58% of related parasites belonged to a single network of relatives, within which parasites were enriched for shared haplotypes at known and suspected drug resistance loci and at one novel locus, reflective of ongoing selection pressure. |
Two decades of molecular surveillance in Senegal reveal changes in known drug resistance mutations associated with historical drug use and seasonal malaria chemoprevention (preprint)
Ndiaye YD , Wong W , Thwing J , Schaffner SS , Tine A , Diallo MA , Deme A , Sy M , Bei AK , Thiaw AB , Daniels R , Ndiaye T , Gaye A , Ndiaye IM , Toure M , Gadiaga N , Sene A , Sow D , Garba MN , Yade MS , Dieye B , Diongue K , Zoumarou D , Ndiaye A , Gomis J , Fall FB , Ndiop M , Diallo I , Sene D , Macinnis B , Seck MC , Ndiaye M , Badiane AS , Hartl DL , Volkman SK , Wirth DF , Ndiaye D . medRxiv 2023 26 Drug resistance in Plasmodium falciparum is a major threat to malaria control efforts. We analyzed data from two decades (2000-2020) of continuous molecular surveillance of P. falciparum parasite strains in Senegal to determine how historical changes in drug administration policy may have affected parasite evolution. We profiled several known drug resistance markers and their surrounding haplotypes using a combination of single nucleotide polymorphism (SNP) molecular surveillance and whole-genome sequence (WGS) based population genomics. We observed rapid changes in drug resistance markers associated with the withdrawal of chloroquine and introduction of sulfadoxine-pyrimethamine in 2003. We also observed a rapid increase in Pfcrt K76T and decline in Pfdhps A437G starting in 2014, which we hypothesize may reflect changes in resistance or fitness caused by seasonal malaria chemoprevention (SMC). Parasite populations evolve rapidly in response to drug use, and SMC preventive efficacy should be closely monitored. Copyright The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. |
Malaria surveillance reveals parasite relatedness, signatures of selection, and correlates of transmission across Senegal (preprint)
Schaffner SF , Badiane A , Khorgade A , Ndiop M , Gomis J , Wong W , Ndiaye YD , Diedhiou Y , Thwing J , Seck MC , Early A , Sy M , Deme A , Diallo MA , Sy N , Sene A , Ndiaye T , Sow D , Dieye B , Ndiaye IM , Gaye A , Ndiaye A , Battle KE , Proctor JL , Bever C , Fall FB , Diallo I , Gaye S , Sene D , Hartl DL , Wirth DF , MacInnis B , Ndiaye D , Volkman SK . medRxiv 2023 17 Parasite genetic surveillance has the potential to play an important role in malaria control. We describe here an analysis of data from the first year of an ongoing, nationwide program of genetic surveillance of Plasmodium falciparum parasites in Senegal, intended to provide actionable information for malaria control efforts. Looking for a good proxy for local malaria incidence, we found that the best predictor was the proportion of polygenomic infections (those with multiple genetically distinct parasites), although that relationship broke down at very low incidence. The proportion of closely related parasites in a site was more weakly correlated with incidence while the local genetic diversity was uninformative. Study of related parasites indicated their potential for discriminating local transmission patterns: two nearby study areas had similarly high fractions of relatives, but one area was dominated by clones and the other by outcrossed relatives. Throughout the country, most related parasites proved to belong to a single network of relatives, within which parasites were enriched for shared haplotypes at known and suspected drug resistance loci as well as at one novel locus, reflective of ongoing selection pressure. Copyright The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. All rights reserved. No reuse allowed without permission. |
Feasibility and acceptability of nationwide HPV vaccine introduction in Senegal: findings from community-level cross-sectional surveys, 2020
Doshi RH , Casey RM , Adrien N , Ndiaye A , Brennan T , Roka JL , Bathily A , Ndiaye C , Li AnYie , Garon J , Badiane O , Diallo A , Loharikar A . PLoS Glob Public Health 2022 2 (4) e0000130 In Senegal, cervical cancer is the most common cancer among women and the leading cause of morbidity and mortality from all cancers. In 2018, Senegal launched a national human papillomavirus (HPV) vaccination program with Gavi, the Vaccine Alliance (Gavi), support. HPV vaccination was incorporated into the national immunization program as a two-dose schedule, with a 6-12-month interval, to nine-year-old girls via routine immunization (RI) services at health facilities, schools and community outreach services throughout the year. During February to March 2020, we conducted interviews to assess the awareness, feasibility, and acceptability of the HPV vaccination program with a cross-sectional convenience sample of healthcare workers (HCWs), school personnel, community healthcare workers (cHCWs), parents, and community leaders from 77 rural and urban health facility catchment areas. Participants were asked questions on HPV vaccine knowledge, delivery, training, and community acceptability of the program. We conducted a descriptive analysis stratified by respondent type. Data were collected from 465 individuals: 77 HCW, 78 school personnel, 78 cHCWs, 152 parents, and community leaders. The majority of HCWs (83.1%) and cHCWs (74.4%) and school personnel (57.7%) attended a training on HPV vaccine before program launch. Of all respondents, most (52.5-87.2%) were able to correctly identify the target population. The majority of respondents (60.2-77.5%) felt that the vaccine was very accepted or accepted in the community. Senegal's HPV vaccine introduction program, among the first national programs in the African region, was accepted by community stakeholders. Training rates were high, and most respondents identified the target population correctly. However, continued technical support is needed for the integration of HPV vaccination as a RI activity for this non-traditional age group. The Senegal experience can be a useful resource for countries planning to introduce the HPV vaccine. |
Sensitivity and specificity for malaria classification of febrile persons by rapid diagnostic test, microscopy, parasite DNA, histidine-rich protein 2, and IgG: Dakar, Senegal 2015
Badiane A , Thwing J , Williamson J , Rogier E , Diallo MA , Ndiaye D . Int J Infect Dis 2022 121 92-97 OBJECTIVES: Different methods detecting Plasmodium parasite infection or exposure are available, but systematic comparison of all these methodologies to predict malaria infection is lacking. Understanding the characteristics of respective tests is helpful to choose the most appropriate tests for epidemiological or research purposes. METHODS: Microscopy, RDT, and PCR was performed for 496 patients presenting with febrile illness in Dakar, Senegal in 2015. Blood samples had laboratory multiplex assays performed for IgG serology and detection of HRP2 antigen. Sensitivity (Se) and specificity (Sp) for different tests were calculated using PCR as the gold standard for detecting active infection. Modeling through latent class analysis (LCA) compared each test to a modeled gold standard for Se/Sp estimates. RESULTS: Against PCR, Se/Sp were 95.2%/93.7% for RDT, 90.4%/100.0% for microscopy, and 97.9%/48.1% for lab HRP2 detection. Compared to the modeled gold standard, Se of microscopy was 93.5%, and Se of RDT, PCR, and lab HRP2 detection were all greater than 99%. Se/Sp of IgG serology were substantially for detecting active infection. CONCLUSIONS: Compared to single tests, a combinatorial LCA approach of multiple biomarkers for detecting malaria infection from patient samples provides greater sensitivity and specificity for epidemiological estimates and research objectives. |
Cost of human papillomavirus vaccine delivery in a single-age cohort, routine-based vaccination program in Senegal
Brennan T , Hidle A , Doshi RH , An Q , Loharikar A , Casey R , Badiane O , Ndiaye A , Diallo A , Loko Roka J , Mejia N , Abimbola T . Vaccine 2021 40 Suppl 1 A77-A84 INTRODUCTION: In 2018, Senegal introduced human papillomavirus (HPV) vaccine into its routine immunization program for all nine-year-old girls nationwide. We evaluated the costs of Senegal's introduction of HPV vaccine via this delivery approach. METHODS: We conducted a retrospective, incremental, ingredients-based cost evaluation from the provider perspective. The study timeframe included Senegal's first planning meeting in 2018 through data collection in early 2020. We collected costs from all involved units at the national and regional levels. A multi-stage cluster sampling approach was used to obtain a nationally representative sample of districts and health facilities. Weights were applied to costs from sampled units to estimate costs across all units. The cost evaluation was based on four dimensions: program activity, resource input, payer, and administrative level. Total costs were divided by the number of HPV doses administered to determine cost per dose and per dimension. RESULTS: Excluding vaccine program activity costs, the total financial and economic delivery costs of Senegal's HPV vaccination program were US$ 1,152,351 and US$ 2,838,466, respectively (US$ 3.07 and US$ 7.56 per dose, respectively). A total of 375,608 HPV vaccine doses were administered during the cost evaluation. Training and per diem represented the largest shares of financial costs. Service delivery and personnel time accounted for the largest shares of economic costs. By administrative level, district and health facility levels had the largest shares of financial and economic costs, respectively. Senegal's Ministry of Health accounted for the largest share of financial and economic costs. Including vaccine program activity costs (US$ 4.68/per dose), the total financial cost was US$ 2,911,343 (US$ 7.75 per dose). CONCLUSION: This cost evaluation can support Senegal's future vaccine introductions and inform other countries planning to introduce HPV vaccine nationwide. These findings support previous costing studies which anticipated potential economies of scale during the transition from HPV vaccine pilot demonstration projects to national introduction. |
National introduction of HPV vaccination in Senegal-Successes, challenges, and lessons learned
Casey RM , Adrien N , Badiane O , Diallo A , Loko Roka J , Brennan T , Doshi R , Garon J , Loharikar A . Vaccine 2021 40 Suppl 1 A10-A16 Following successful school-based demonstration programs in 2014-2016, the human papillomavirus (HPV) vaccine was introduced nationwide in Senegal for 9-year-old girls in 2018, using a routine service delivery strategy at health facilities, schools, and other outreach sites. We reviewed the HPV vaccine introduction in Senegal to understand the successes, challenges, and lessons learned. Focusing on three key domains (program decision-making, planning, and implementation), we conducted ten semi-structured interviews during 2019-2020 with purposively selected national-level stakeholders (government, expert advisory committee, key technical and implementation partners) and comprehensive desk reviews of country documents on HPV vaccine introduction. Due to the global HPV vaccine shortage, the introduction was limited to a single-age cohort; therefore, 9-year-old girls were chosen. This strategy enabled Senegal to potentially reach more girls in primary education because school enrolment rates decline thereafter. Vaccination through routine delivery platforms (i.e., health facility, school-based, and community outreach) was perceived to be more cost-effective than a campaign approach. High-level political commitment and collaborations between immunization and education partners were frequently cited by key informants as reasons for a successful vaccine introduction. All key informants reported that the health care worker (HCW) strike, rumors, and vaccine hesitancy negatively impacted the introduction. Other challenges noted included insufficient information on attitudes towards HPV vaccination among HCWs, teachers, and community members. Senegal successfully introduced HPV vaccine into the national immunization schedule, using a routine delivery strategy. Strong leadership and a multi-sectoral approach likely contributed to this success. To build sustainability of the HPV vaccination program in the future, it is important to improve the understanding and engagement among all stakeholders, including HCWs and community members, and to strengthen and innovate communication and crisis management strategies. To better understand the efficiency and effectiveness of Senegal's vaccination strategy, additional assessments of the operational costs and coverage achieved are needed. |
Analysis of anti-Plasmodium IgG profiles among Fulani nomadic pastoralists in northern Senegal to assess malaria exposure
Seck MC , Thwing J , Badiane AS , Rogier E , Fall FB , Ndiaye PI , Diongue K , Mbow M , Ndiaye M , Diallo MA , Gomis JF , Mbaye A , Ndiaye T , Gaye A , Sy M , Deme AB , Ndiaye YD , Ndiaye D . Malar J 2020 19 (1) 15 BACKGROUND: Northern Senegal is a zone of very low malaria transmission, with an annual incidence of < 5/1000 inhabitants. This area, where the Senegal National Malaria Control Programme has initiated elimination activities, hosts Fulani, nomadic, pastoralists that spend the dry season in the south where malaria incidence is higher (150-450/1000 inhabitants) and return to the north with the first rains. Previous research demonstrated parasite prevalence of < 1% in this Fulani population upon return from the south, similar to that documented in the north in cross-sectional surveys. METHODS: A modified snowball sampling survey of nomadic pastoralists was conducted in five districts in northern Senegal during September and October 2014. Demographic information and dried blood spots were collected. Multiplex bead-based assays were used to assess antibody responses to merozoite surface protein (MSP-119) antigen of the four primary Plasmodium species, as well as circumsporozoite protein (CSP) and liver stage antigen (LSA-1) of Plasmodium falciparum. RESULTS: In the five study districts, 1472 individuals were enrolled, with a median age of 22 years (range 1 to 80 years). Thirty-two percent of subjects were under 14 years and 57% were male. The overall seroprevalence of P. falciparum MSP-119, CSP and LSA-1 antibodies were 45, 12 and 5%, respectively. Plasmodium falciparum MSP-119 antibody responses increased significantly with age in all study areas, and were significantly higher among males. The highest seroprevalence to P. falciparum antigens was observed in the Kanel district (63%) and the lowest observed in Podor (28%). Low seroprevalence was observed for non-falciparum species in all the study sites: 0.4, 0.7 and 1.8%, respectively, for Plasmodium ovale, Plasmodium vivax and Plasmodium malariae MSP-1. Antibody responses to P. vivax were observed in all study sites except Kanel. CONCLUSION: Prevalence of P. falciparum MSP-119 antibodies and increases by study participant age provided data for low levels of exposure among this transient nomadic population. In addition, antibody responses to P. falciparum short half-life markers (CSP and LSA-1) and non-falciparum species were low. Further investigations are needed to understand the exposure of the Fulani population to P. vivax. |
Serological data shows low levels of chikungunya exposure in Senegalese nomadic pastoralists
Seck MC , Badiane AS , Thwing J , Moss D , Fall FB , Gomis JF , Deme AB , Diongue K , Sy M , Mbaye A , Ndiaye T , Gaye A , Ndiaye YD , Diallo MA , Ndiaye D , Rogier E . Pathogens 2019 8 (3) The chikungunya virus (CHIKV) is spread by Aedes aegypti and Ae. albopictus mosquitos worldwide; infection can lead to disease including joint pain, fever, and rash, with some convalescent persons experiencing chronic symptoms. Historically, CHIKV transmission has occurred in Africa and Asia, but recent outbreaks have taken place in Europe, Indonesia, and the Americas. From September to October 2014, a survey was undertaken with nomadic pastoralists residing in the northeast departments of Senegal. Blood dried on filter paper (dried blood spots; DBS) were collected from 1465 participants of all ages, and assayed for Immunoglobulin G (IgG) antibodies against CHIKV E1 antigen by a bead-based multiplex assay. The overall seroprevalence of all participants to CHIKV E1 was 2.7%, with no persons under 10 years of age found to be antibody positive. Above 10 years of age, clear increases of seroprevalence and IgG levels were observed with increasing age; 7.6% of participants older than 50 years were found to be positive for anti-CHIKV IgG. Reported net ownership, net usage, and gender were all non-significant explanatory variables of seropositivity. These data show a low-level historical exposure of this pastoralist population to CHIKV, with no evidence of recent CHIKV transmission in the past decade. |
Post-treatment HRP2 clearance in patients with uncomplicated Plasmodium falciparum malaria
Plucinski MM , Dimbu PR , Fortes F , Abdulla S , Ahmed S , Gutman J , Kachur SP , Badiane A , Ndiaye D , Talundzic E , Lucchi N , Aidoo M , Udhayakumar V , Halsey E , Rogier E . J Infect Dis 2017 217 (5) 685-692 Background: Response to antimalarial treatment is assessed using serial microscopy. New techniques for accurate measurement of the Plasmodium falciparum histidine rich protein 2 (HRP2) antigen have made monitoring antigen concentration over time a potential alternative for assessing treatment response. Methods: Post-treatment HRP2 concentration was measured in longitudinal samples from 537 participants with P. falciparum malaria from efficacy trials in Angola, Tanzania, and Senegal. The HRP2 half-life was estimated using a first-order kinetics clearance model. The association between HRP2 concentration three days post-treatment and recrudescence of infection was assessed. Results: Despite substantial variation in HRP2 concentration at baseline, HRP2 concentration in patients consistently showed a first-order exponential decline. The median half-life of HRP2 was estimated to be 4.5 days (interquartile range: 3.3-6.6) in Angola, 4.7 days (4.0-5.9) in Tanzania, and 3.0 days (2.1-4.5) in Senegal. The day 3 HRP2 concentration was predictive of eventual recrudescence, with an area under the receiver operating characteristic curve of 0.86 (95% confidence interval: 0.73-0.99). Conclusions: Consistent HRP2 clearance dynamics following successful antimalarial treatment imply a common underlying biological clearance mechanism. Patients that ultimately failed treatment did not exhibit this same pattern of clearance, even in the absence of other indications of inadequate response to treatment. |
Malaria surveys using rapid diagnostic tests and validation of results using post hoc quantification of Plasmodium falciparum histidine-rich protein 2
Plucinski M , Dimbu R , Candrinho B , Colborn J , Badiane A , Ndiaye D , Mace K , Chang M , Lemoine JF , Halsey ES , Barnwell JW , Udhayakumar V , Aidoo M , Rogier E . Malar J 2017 16 (1) 451 BACKGROUND: Rapid diagnostic test (RDT) positivity is supplanting microscopy as the standard measure of malaria burden at the population level. However, there is currently no standard for externally validating RDT results from field surveys. METHODS: Individuals' blood concentration of the Plasmodium falciparum histidine rich protein 2 (HRP2) protein were compared to results of HRP2-detecting RDTs in participants from field surveys in Angola, Mozambique, Haiti, and Senegal. A logistic regression model was used to estimate the HRP2 concentrations corresponding to the 50 and 90% level of detection (LOD) specific for each survey. RESULTS: There was a sigmoidal dose-response relationship between HRP2 concentration and RDT positivity for all surveys. Variation was noted in estimates for field RDT sensitivity, with the 50% LOD ranging between 0.076 and 6.1 ng/mL and the 90% LOD ranging between 1.1 and 53 ng/mL. Surveys conducted in two different provinces of Angola using the same brand of RDT and same study methodology showed a threefold difference in LOD. CONCLUSIONS: Measures of malaria prevalence estimated using population RDT positivity should be interpreted in the context of potentially large variation in RDT LODs between, and even within, surveys. Surveys based on RDT positivity would benefit from external validation of field RDT results by comparing RDT positivity and antigen concentration. |
Evidence of non-Plasmodium falciparum malaria infection in Kedougou, Senegal
Daniels RF , Deme AB , Gomis JF , Dieye B , Durfee K , Thwing JI , Fall FB , Ba M , Ndiop M , Badiane AS , Ndiaye YD , Wirth DF , Volkman SK , Ndiaye D . Malar J 2017 16 (1) 9 BACKGROUND: Expanded malaria control efforts in Senegal have resulted in increased use of rapid diagnostic tests (RDT) to identify the primary disease-causing Plasmodium species, Plasmodium falciparum. However, the type of RDT utilized in Senegal does not detect other malaria-causing species such as Plasmodium ovale spp., Plasmodium malariae, or Plasmodium vivax. Consequently, there is a lack of information about the frequency and types of malaria infections occurring in Senegal. This study set out to better determine whether species other than P. falciparum were evident among patients evaluated for possible malaria infection in Kedougou, Senegal. METHODS: Real-time polymerase chain reaction speciation assays for P. vivax, P. ovale spp., and P. malariae were developed and validated by sequencing and DNA extracted from 475 Plasmodium falciparum-specific HRP2-based RDT collected between 2013 and 2014 from a facility-based sample of symptomatic patients from two health clinics in Kedougou, a hyper-endemic region in southeastern Senegal, were analysed. RESULTS: Plasmodium malariae (n = 3) and P. ovale wallikeri (n = 2) were observed as co-infections with P. falciparum among patients with positive RDT results (n = 187), including one patient positive for all three species. Among 288 negative RDT samples, samples positive for P. falciparum (n = 24), P. ovale curtisi (n = 3), P. ovale wallikeri (n = 1), and P. malariae (n = 3) were identified, corresponding to a non-falciparum positivity rate of 2.5%. CONCLUSIONS: These findings emphasize the limitations of the RDT used for malaria diagnosis and demonstrate that non-P. falciparum malaria infections occur in Senegal. Current RDT used for routine clinical diagnosis do not necessarily provide an accurate reflection of malaria transmission in Kedougou, Senegal, and more sensitive and specific methods are required for diagnosis and patient care, as well as surveillance and elimination activities. These findings have implications for other malaria endemic settings where species besides P. falciparum may be transmitted and overlooked by control or elimination activities. |
Evaluation of the Illumigene Malaria LAMP: A Robust Molecular Diagnostic Tool for Malaria Parasites.
Lucchi NW , Gaye M , Diallo MA , Goldman IF , Ljolje D , Deme AB , Badiane A , Ndiaye YD , Barnwell JW , Udhayakumar V , Ndiaye D . Sci Rep 2016 6 36808 Isothermal nucleic acid amplification assays such as the loop mediated isothermal amplification (LAMP), are well suited for field use as they do not require thermal cyclers to amplify the DNA. To further facilitate the use of LAMP assays in remote settings, simpler sample preparation methods and lyophilized reagents are required. The performance of a commercial malaria LAMP assay (Illumigene Malaria LAMP) was evaluated using two sample preparation workflows (simple filtration prep (SFP)) and gravity-driven filtration prep (GFP)) and pre-dispensed lyophilized reagents. Laboratory and clinical samples were tested in a field laboratory in Senegal and the results independently confirmed in a reference laboratory in the U.S.A. The Illumigene Malaria LAMP assay was easily implemented in the clinical laboratory and gave similar results to a real-time PCR reference test with limits of detection of ≤2.0 parasites/mul depending on the sample preparation method used. This assay reliably detected Plasmodium sp. parasites in a simple low-tech format, providing a much needed alternative to the more complex molecular tests for malaria diagnosis. |
Non-falciparum malaria in Dakar: a confirmed case of Plasmodium ovale wallikeri infection.
Diallo MA , Badiane AS , Diongue K , Deme A , Lucchi NW , Gaye M , Ndiaye T , Ndiaye M , Sene LK , Diop A , Gaye A , Ndiaye YD , Samb D , Yade MS , Ndir O , Udhayakumar V , Ndiaye D . Malar J 2016 15 (1) 429 BACKGROUND: Plasmodium ovale is rarely described in Senegal. A case of clinical malaria due to P. ovale wallikeri in West Central of Senegal is reported. CASE: A 34-year-old male baker in Dakar, with no significant previous medical history, was admitted to a health clinic with fever and vomiting. Fever had been lasting for 4 days with peaks every 48 h. As monospecific Plasmodium falciparum HRP-2 RDT was negative, he was treated with antibiotics. However, owing to persisting symptoms, he was referred to the emergency unit of the Youssou Mbargane Diop Hospital, Dakar, Senegal. Clinical examination found impaired general condition. All other physical examinations were normal. Laboratory tests showed anaemia (haemoglobin 11.4 g/dl), severe thrombocytopaenia (platelets 30 x 10(9)/mm(3)), leukopenia (3650/mm(3)), lymphocytopenia (650/mm(3)). Renal function was normal as indicated by creatininaemia and uraemia (11 mg/l and 0.25 g/l, respectively) and liver enzymes were slightly elevated (aspartate aminotransferase 77 UI/l and alanine aminotransferase 82 UI/l). Blood smear evaluations in Parasitology Laboratory of Aristide Le Dantec Hospital showed malaria parasites of the species P. ovale with a 0.08 % parasitaemia. Molecular confirmation was done by real time PCR targeting the 18S rRNA gene. The P. ovale infection was further analysed to species level targeting the potra gene and was identified as P. ovale wallikeri. According to the hospital's malaria treatment guidelines for severe malaria, treatment consisted of intravenous quinine at hour 0 (start of treatment) and 24 h after initial treatment, followed by artemether-lumefantrine 24 h later. A negative microscopy was noted on day 3 post-treatment and the patient reported no further symptoms. CONCLUSION: Malaria due to non-falciparum species is probably underestimated in Senegal. RDTs specific to non-falciparum species and/or pan specific RDTs should be included as tools of diagnosis to fight against malaria in Senegal. In addition, a field-deployable molecular tool such as the loop-mediated isothermal amplification can be considered as an additional useful tool to detect low malaria parasite infections and for speciation. In addition, national malaria control policies should consider other non-falciparum species in treatment guidelines, including the provision of primaquine for the treatment of relapsing parasites. |
Application of the World Health Organization programmatic assessment tool for risk of measles virus transmission - lessons learned from a measles outbreak in Senegal
Harris JB , Badiane O , Lam E , Nicholson J , Oumar Ba I , Diallo A , Fall A , Masresha BG , Goodson JL . Risk Anal 2015 36 (9) 1708-17 The World Health Organization (WHO) African Region set a goal for regional measles elimination by 2020; however, regional measles incidence was 125/1,000,000 in 2012. To support elimination efforts, the WHO and U.S. Centers for Disease Control and Prevention developed a tool to assess performance of measles control activities and identify high-risk areas at the subnational level. The tool uses routinely collected data to generate district-level risk scores across four categories: population immunity, surveillance quality, program performance, and threat assessment. To pilot test this tool, we used retrospective data from 2006 to 2008 to identify high-risk districts in Senegal; results were compared with measles case-based surveillance data from 2009 when Senegal experienced a large measles outbreak. Seventeen (25%) of 69 districts in Senegal were classified as high or very high risk. The tool highlighted how each of the four categories contributed to the total risk scores for high or very high risk districts. Measles case-based surveillance reported 986 cases during 2009, including 368 laboratory-confirmed, 540 epidemiologically linked, and 78 clinically compatible cases. The seven districts with the highest numbers of laboratory-confirmed or epidemiologically linked cases were within the capital region of Dakar. All except one of these seven districts were estimated to be high or very high risk, suggesting that districts identified as high risk by the tool have the potential for measles outbreaks. Prospective use of this tool is recommended to help immunization and surveillance program managers identify high-risk areas in which to strengthen specific programmatic weaknesses and mitigate risk for potential measles outbreaks. |
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