Two decades of molecular surveillance in Senegal reveal rapid changes in known drug resistance mutations over time.

BACKGROUND: Drug resistance in Plasmodium falciparum is a major threat to malaria control efforts. Pathogen genomic surveillance could be invaluable for monitoring current and emerging parasite drug resistance. METHODS: Data from two decades (2000-2020) of continuous molecular surveillance of P. falciparum parasites from Senegal were retrospectively examined to assess historical changes in malaria drug resistance mutations. Several known drug resistance markers and their surrounding haplotypes were profiled using a combination of single nucleotide polymorphism (SNP) molecular surveillance and whole genome sequence based population genomics. RESULTS: This dataset was used to track temporal changes in drug resistance markers whose timing correspond to historically significant events such as the withdrawal of chloroquine (CQ) and the introduction of sulfadoxine-pyrimethamine (SP) in 2003. Changes in the mutation frequency at Pfcrt K76T and Pfdhps A437G coinciding with the 2014 introduction of seasonal malaria chemoprevention (SMC) in Senegal were observed. In 2014, the frequency of Pfcrt K76T increased while the frequency of Pfdhps A437G declined. Haplotype-based analyses of Pfcrt K76T showed that this rapid increase was due to a recent selective sweep that started after 2014. DISCUSSION (CONCLUSION): The rapid increase in Pfcrt K76T is troubling and could be a sign of emerging amodiaquine (AQ) resistance in Senegal. Emerging AQ resistance may threaten the future clinical efficacy of artesunate-amodiaquine (ASAQ) and AQ-dependent SMC chemoprevention. These results highlight the potential of molecular surveillance for detecting rapid changes in parasite populations and stress the need to monitor the effectiveness of AQ as a partner drug for artemisinin-based combination therapy (ACT) and for chemoprevention.

Quality assessment of malaria microscopic diagnosis at the Aristide Le Dantec University Hospital of Dakar, Senegal, in 2020.

BACKGROUND: Following WHO guidelines, microscopy is the gold standard for malaria diagnosis in endemic countries. The Parasitology-Mycology laboratory (LPM) is the National Reference Laboratory and is currently undergoing ISO 15189 accreditation. In this context, we assessed the performance of the laboratory by confirming the reliability and the accuracy of results obtained in accordance with the requirements of the ISO 15189 standards. This study aimed to verify the method of microscopic diagnosis of malaria at the LPM, in the Aristide Le Dantec hospital (HALD) in Dakar, Senegal. METHODS: This is a validation/verification study conducted from June to August 2020. Twenty (20) microscopic slides of thick/thin blood smear with known parasite densities (PD) selected from the Cheick Anta Diop University malaria slide bank in Dakar were used for this assessment. Six (6) were used to assess microscopists' ability to determine PD and fourteen (14) slides were used for detection (positive vs negative) and identification of parasites. Four (4) LPM-HALD microscopists read and recorded their results on prepared sheets. Data analysis was done with Microsoft Excel 2010 software. RESULTS: A minimum threshold of 50% concordance was used for comparison. Of the twenty (20) slides read, 100% concordance was obtained on eight (8) detection (positive vs negative) slides. Four (4) out of the six (6) parasite density evaluation slides obtained a concordance of less than 50%. Thirteen (13) out of the fourteen (14) identification slides obtained a concordance greater than 50%. Only one (1) identification slide obtained zero agreement from the microscopists. For species identification a concordance greater than 80% was noted and the microscopists obtained scores between 0.20 and 0.4 on a scale of 0 to 1 for parasite density reading. The microscopists obtained 100% precision, sensitivity, specificity and both negative and positive predictive values. CONCLUSION: This work demonstrated that the microscopic method of malaria diagnosis used in the LPM/HALD is in accordance with the requirements of WHO and ISO 15189. Further training of microscopists may be needed to maintain competency.

Investigating the etiologies of non-malarial febrile illness in Senegal using metagenomic sequencing.

The worldwide decline in malaria incidence is revealing the extensive burden of non-malarial febrile illness (NMFI), which remains poorly understood and difficult to diagnose. To characterize NMFI in Senegal, we collected venous blood and clinical metadata in a cross-sectional study of febrile patients and healthy controls in a low malaria burden area. Using 16S and untargeted sequencing, we detected viral, bacterial, or eukaryotic pathogens in 23% (38/163) of NMFI cases. Bacteria were the most common, with relapsing fever Borrelia and spotted fever Rickettsia found in 15.5% and 3.8% of cases, respectively. Four viral pathogens were found in a total of 7 febrile cases (3.5%). Sequencing also detected undiagnosed Plasmodium, including one putative P. ovale infection. We developed a logistic regression model that can distinguish Borrelia from NMFIs with similar presentation based on symptoms and vital signs (F1 score: 0.823). These results highlight the challenge and importance of improved diagnostics, especially for Borrelia, to support diagnosis and surveillance.

SEROPREVALENCE TO SCHISTOSOMA SOLUBLE EGG ANTIGEN AMONG NOMADIC PASTORALISTS RESIDING IN NORTHERN SENEGAL.

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.

Improving diagnosis of non-malarial fevers in Senegal: Borrelia and the contribution of tick-borne bacteria.

The worldwide decline in malaria incidence is revealing the extensive burden of non-malarial febrile illness (NMFI), which remains poorly understood and difficult to diagnose. To characterize NMFI in Senegal, we collected venous blood and clinical metadata from febrile patients and healthy controls in a low malaria burden area. Using 16S and unbiased sequencing, we detected viral, bacterial, or eukaryotic pathogens in 29% of NMFI cases. Bacteria were the most common, with relapsing fever Borrelia and spotted fever Rickettsia found in 15% and 3.7% of cases, respectively. Four viral pathogens were found in a total of 7 febrile cases (3.5%). Sequencing also detected undiagnosed Plasmodium, including one putative P. ovale infection. We developed a logistic regression model to distinguish Borrelia from NMFIs with similar presentation based on symptoms and vital signs. These results highlight the challenge and importance of improved diagnostics, especially for Borrelia, to support diagnosis and surveillance.

Simultaneous seroprevalence of Toxoplasma gondii and rubella virus infections in pregnant women in Dakar (Senegal).

Context: Toxoplasma gondii and rubella virus are microorganisms that can cause intrauterine infections and congenital anomalies in the fetus. Data regarding the simultaneous seroprevalence of these infections are not available in Senegal. Aims: This study aimed to determine for the first time the simultaneous seroprevalence of toxoplasmosis and rubella among pregnant women in Dakar. Materials and Methods: In this retrospective study, anti-Toxoplasma and anti-rubella antibodies were analyzed in the serum samples obtained from pregnant women receiving prenatal care at Military Hospital of Ouakam between 2016 and 2021 using a chemiluminescent microparticle immunoassay for the quantitative determination of immunoglobulin G (IgG) and IgM antibodies to Toxoplasma gondii and rubella in human serum. Results: Overall, data from 2589 women were analyzed. The median age was 29 years (interquartile range: 23.14-34.86). Serum IgG and IgM were positive for T. gondii with 35.84% and 1.66%, respectively. Rubella seroprevalence was 87.14% and 0.35%, respectively, for IgG and IgM. Seroprevalence of toxoplasmosis increases significantly with age and study period. For rubella infection, the highest seroprevalence rates were noted in the youngest age group and at the end of the study period. Conclusions: Data from this first-time study regarding simultaneous seroprevalence of toxoplasmosis and rubella among pregnant women in Senegal indicate a continuing high risk of congenital toxoplasmosis and congenital rubella syndrome in Dakar. Further studies are needed to fully assess the efficacy of rubella vaccination in women of childbearing age.

Evaluation of knowledge and experience of fungal infections (mycoses) among clinical doctors in Senegal.

In order to assess the knowledge and experience of fungal infections (FIs) among clinicians in Senegal, a cross-sectional survey was carried out among medical practitioners in Senegal via a questionnaire designed with "Google Forms" between 24 January and 24 April 2022. A total of 100 clinicians responded to the questionnaire. Clinicians in the 31- 40-year-old age group formed the majority of respondents (51%). Male respondents were predominant (72%). Forty-one percent of respondents were general practitioners, 40% were specialist doctors, and the rest were residents. Dermatologists were the most common at 15% (6/40). In terms of clinicians' general knowledge of fungi, FIs and their therapeutic management, an average of 70% correct answers was recorded. The majority (70%) of respondents cared for between two to four different categories of patients at risk of invasive FIs (IFIs) at a time, with diabetes predominating. Eighty percent confirmed that they had been confronted with FIs, including 43% with superficial FIs, 3% with subcutaneous FIs and 5% with IFIs. Thirty-four percent of doctors stated that they had never suspected an IFI. Candidiasis was the most commonly mentioned mycosis by doctors. To support the diagnosis of these FIs, 22% of the clinicians said that they had recourse only to the clinical diagnosis. In total, 79% of clinicians responded that they had never used an antifungal chemoprophylaxis. In addition, 28% and 22% of practicing physicians chose a combination of antifungals for the chemoprophylaxis of invasive candidiasis and invasive aspergillosis, respectively. This survey shows that both clinicians' knowledge and experience of fungi, antifungals, FIs and their therapeutic management, as well as chemoprophylaxis, need to be improved. Indeed, half of the clinicians seem to be unaware of the incidence of FIs, in particular IFIs, which, nevertheless, represent some of the deadliest infectious diseases in the world.

Two decades of molecular surveillance in Senegal reveal changes in known drug resistance mutations associated with historical drug use and seasonal malaria chemoprevention.

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.

[Atrial fibrillation in three cardiological reference centers in Dakar: Senegal data from the AFRICA register survey]. / La fibrillation atriale dans trois centres cardiologiques de référence de Dakar: données sénégalaises de l'enquête du registre AFRICA.

Introduction: atrial fibrillation (AF) is the most common cardiac rhythm disorder. Its prevalence is underestimated in Africa, hence the initiation of the Atrial Fibrillation Registry In Countries of Africa (AFRICA). The aim of our study was to describe, within the framework of the AFRICA registry, the epidemiological, clinical, paraclinical, therapeutic and evolutionary aspects of atrial fibrillation (AF) in Africa, particularly in Senegal. Methods: we performed a cross-sectional, retrospective, multicentric study conducted from January 1st to December 31st 2017, in three referral cardiology wards in Senegal. Results: one hundred and sixty-eight patients, with a mean age of 63 years, were selected, representing a hospital prevalence of 5.99%. There was a predominance of women with sex-ratio of 0.69. High blood pressure was the most frequent risk factor (24.4%). Heart failure was the most frequent circumstance of discovery (59.52%). AF was persistent in 52.24% and valvular AF accounted for 31% and was more frequent in young people (p= 0.005). Left ventricular systolic function was impaired in 55.7%, the left atrium was dilated in 70.83%. The strategy to reduce heart rate was the most used. Patients with CHA2DS2VASC ≥ 2 received anticoagulation with LMWH and oral relay maid mostly of VKA. The complications were dominated by heart failure (66.6%) and ischemic stroke cerebral (28%). Conclusion: atrial fibrillation (AF) is the most frequent cardiac rhythm disorder. It is a major public health concern.

Spatiotemporal Dynamic of the RTS,S/AS01 Malaria Vaccine Target Antigens in Senegal.

The RTS,S/AS01 malaria vaccine confers only moderate protection against malaria. Evidence suggests that the effectiveness of the RTS,S/AS01 vaccine depends upon the parasite population genetics, specifically regarding the circumsporozoite protein haplotypes in the population. We investigated Plasmodium falciparum circumsporozoite protein (PfCSP) gene sequences from two endemic sites in 2018 in Senegal. The PfCSP sequences were compared with those retrieved from the Pf3k genome database. In the central repeat region of PfCSP, the distribution of haplotypes differed significantly between the two study sites (Fisher's exact test, P < 0.001). No 3D7 vaccine strain haplotype was observed in this locus. In the C-terminal region, there was no significant difference in haplotypes distribution between Kedougou and Diourbel (Fischer's exact test, P = 0.122). The 3D7 haplotype frequency was 8.4% in early samples (2001-2011), but then it contracted in the subsequent years. The extensive plasticity of the P. falciparum genes coding the RTS,S/AS01 vaccine target antigens may influence the immune responses to circulating alleles. Monitoring the genetic diversity baseline and its dynamics over time and space would be instrumental in rationally improving the malaria RTS,S/AS01 vaccine and/or its implementation schedule.

Humanitarian Maxillofacial Mission's Success Requires Experienced Surgeons, Careful Planning, and Meeting With the Local's Care Needs.

PURPOSE: Meeting with local needs of low- and middle-income countries during maxillofacial humanitarian mission is not easy. This article aimed to report on 5 years of experience in humanitarian maxillofacial surgery missions. In addition, several key points for best practices and meeting the medical needs of local populations are discussed. METHODS: In this retrospective case series, all medical charts of patients managed during humanitarian maxillofacial surgery missions organized within the department of maxillofacial surgery of Le Dantec Hospital (Senegal) were analyzed. Disease characteristics, treatments modality, and outcomes were reviewed. Moreover, missions planning and costs were studied. RESULTS: Between 2015 and 2018, 5 humanitarian missions were organized totalizing 177 patients, one-third of which were treated surgically. Tumors (35%) and sequelae from previous surgeries, cancrum oris or trauma (24%) were the most frequently treated disorders. Most patients were treated with free flap reconstructions (35%). Postoperative complications were observed for only 3 patients (5%). With a median follow-up of 13 months, no sequelae requiring specific treatment were observed. The estimated total cost for each mission was $39,000. CONCLUSION: In order to benefit both the locals and the volunteers, humanitarian maxillofacial missions should be carefully planned and volunteers appropriately prepared. Other keys to the success of such missions are setting up training and support programs, reflecting upon ethical considerations, understanding local cultural customs and ensuring mutual respect with the locals. Frequent self-evaluation and long-term mission sustainability are critical. Finally, mission costs should be evaluated.

Epidemiological aspects of superficial fungal infections in Koranic schools in two localities of Senegal (Thies and Touba).

BACKGROUND: In developing countries, superficial fungal infections (SFI) are endemic and cause a therapeutic problem because of the duration and cost of treatment. Community living and promiscuity are key factors in the direct or indirect transmission and spread of these diseases. OBJECTIVES: The objective was to study the epidemiological aspects of SFI, among koranic school children in two localities in Senegal. PATIENTS/METHODS: School koranic students were recruited in Thies and Touba. Diagnosis of fungal diseases was carried out using conventional techniques (microscopic examination and culture). RESULTS: Among 210 children, the overall prevalence of SFI was 25.71%, with 27.63% in Touba and 20.68% in Thiès. The clinical lesions were epidermophytosis (0.5%), intertrigo (0.9%), palmoplantar keratoderma (KPP) (0.9%), onychomycosis (7.7%) and tinea capitis (TC) (90%). The species responsible for the SFI were Trichophyton soudanense (85.18%), Microsporum audouinii langeronii (9.25%), Trichophyton rubrum (3.70%) and Chrysosporium keratinophilum (1.85%). The prevalence of infection was higher among boys (85.18%). CONCLUSION: Superficial fungal infections are prevalent in koranic school children and attention should be given to non-dermatophytic species that could be responsible for SFI.

High prevalence of asymptomatic Plasmodium infection in Bandafassi, South-East Senegal.

BACKGROUND: Malaria control and elimination strategies are based on levels of transmission that are usually determined by data collected from health facilities. In endemic areas, asymptomatic Plasmodium infection is thought to represent the majority of infections, though they are not diagnosed nor treated. Therefore, there might be an underestimation of the malaria reservoir, resulting in inadequate control strategies. In addition, these untreated asymptomatic Plasmodium infections maintain transmission, making it difficult or impossible to reach malaria elimination goals. Thus, the aim of this study was to determine the prevalence of asymptomatic Plasmodium infections in southeastern Senegal. METHODS: A cross sectional study was conducted among asymptomatic individuals (N = 122) living in the village of Andiel located in Bandafassi, Kédougou, which consisted of about 200 inhabitants during the malaria transmission season in late October 2019. For each individual without malaria-related symptoms and who consented to participate, a rapid diagnostic test (RDT) was performed in the field. Results were confirmed in the laboratory with photo-induced electron transfer (PET-PCR). RESULTS: Malaria prevalence was 70.3% by PET-PCR and 41.8% by RDT. During the same period, the health post of the area reported 49. 1% test positivity rate by RDT. The majority of the infected study population, 92.9%, was infected with a single species and 7.1% had two or three species of Plasmodium. Plasmodium falciparum was predominant and represented 90.2% of the infections, while 6.5% were due to Plasmodium ovale and 3.3% to Plasmodium malariae. 59.4% of children targeted for SMC (zero to ten years old) were infected. CONCLUSION: In southeastern Senegal, where the transmission is the highest, malaria control strategies should address asymptomatic Plasmodium infections at the community level. The results suggest that this area could be eligible for mass drug administration. Moreover, non-falciparum species could be more common and its prevalence should be determined countrywide.

Genomic investigation of a dengue virus outbreak in Thiès, Senegal, in 2018.

Dengue virus is a major and rapidly growing public health concern in tropic and subtropic regions across the globe. In late 2018, Senegal experienced its largest dengue virus outbreak to date, covering several regions. However, little is known about the genetic diversity of dengue virus (DENV) in Senegal. Here we report complete viral genomes from 17 previously undetected DENV cases from the city of Thiès. In total we identified 19 cases of DENV in a cohort of 198 individuals with fever collected in October and November 2018. We detected 3 co-circulating serotypes; DENV 3 was the most frequent accounting for 11/17 sequences (65%), 4 (23%) were DENV2 and 2 (12%) were DENV1. Sequences were most similar to recent sequences from West Africa, suggesting ongoing local circulation of viral populations; however, detailed inference is limited by the scarcity of available genomic data. We did not find clear associations with reported clinical signs or symptoms, highlighting the importance of testing for diagnosing febrile diseases. Overall, these findings expand the known range of DENV in Senegal, and underscore the need for better genomic characterization of DENV in West Africa.

Pulmonary Madurella mycetomatis mycetoma secondary to knee eumycetoma, Senegal.

Mycetoma is a neglected tropical disease which is endemic in Senegal. Although this subcutaneous mycosis is most commonly found on the foot, extrapodal localisations have also been found, including on the leg, knee, thigh, hand, and arm. To our knowledge, no case of blood-spread eumycetoma has been reported in Senegal. Here, we report a case of pulmonary mycetoma secondary to a Madurella mycetomatis knee eumycetoma. The patient was a 41-year-old farmer living in Louga, Senegal, where the Sudano-Sahelian climate is characterised by a short and unstable rainy season and a steppe vegetation. He suffered a trauma to the right more than 20 years previously and had received treatment for more than 10 years with traditional medicine. He consulted at Le Dantec University Hospital in Dakar for treatment of a right knee mycetoma which had been diagnosed more than 10 years ago. He had experienced a chronic cough for more than a year; tuberculosis documentation was negative. Grains collected from the knee and the sputum isolated M. mycetomatis, confirmed by the rRNA gene ITS regions nucleotide sequence analysis. An amputation above the knee was performed, and antibacterial and antifungal therapy was started with amoxicillin-clavulanic acid and terbinafine. The patient died within a month of his discharge from hospital.

Evaluation of the Multiplex Real-Time PCR DermaGenius® Assay for the Detection of Dermatophytes in Hair Samples from Senegal.

For the successful treatment of dermatophytoses, especially tinea capitis, there is a need for accurate and rapid diagnostic methods. A lot of recent literature has focused on the detection of dermatophytes directly on sample material such as nails, hair and skin scrapings. Molecular tools offer the ability to rapidly diagnose dermatophytosis within 48 h. This study aimed to compare the results of a commercial real-time PCR (real-time PCR) assay DermaGenius®(DG) 2.0 complete multiplex kit with those of conventional diagnostic methods (direct microscopy and culture). A total of 129 hair samples were collected in Dakar (Senegal) from patients suspected of dermatophytosis. DG was applied for the molecular detection of Candida albicans, Trichophyton rubrum/soudanense, T. interdigitale, T. tonsurans, T. mentagrophytes, T. violaceum, Microsporum canis, M. audouinii, Epidermophyton floccosum, T. benhamiae and T. verrucosum. Dermatophytes species and C. albicans were differentiated by melting curve analysis. The sensitivity and specificity of the PCR assay were 89.3% and 75.3%, respectively. DG PCR was significantly more sensitive than culture (p < 0.001). DG PCR is fast and robust to contamination. In this paper, the main questions discussed were the replacement of culture by a broad-spectrum fungal real-time PCR and the implementation of DG PCR into a routine laboratory in Senegal.

Efficacy and safety of artemisinin-based combination therapy and the implications of Pfkelch13 and Pfcoronin molecular markers in treatment failure in Senegal.

In 2006, Senegal adopted artemisinin-based combination therapy (ACT) as first-line treatment in the management of uncomplicated malaria. This study aimed to update the status of antimalarial efficacy more than ten years after their first introduction. This was a randomized, three-arm, open-label study to evaluate the efficacy and safety of artemether-lumefantrine (AL), artesunate-amodiaquine (ASAQ) and dihydroartemisinin-piperaquine (DP) in Senegal. Malaria suspected patients were screened, enrolled, treated, and followed for 28 days for AL and ASAQ arms or 42 days for DP arm. Clinical and parasitological responses were assessed following antimalarial treatment. Genotyping (msp1, msp2 and 24 SNP-based barcode) were done to differentiate recrudescence from re-infection; in case of PCR-confirmed treatment failure, Pfk13 propeller and Pfcoronin genes were sequenced. Data was entered and analyzed using the WHO Excel-based application. A total of 496 patients were enrolled. In Diourbel, PCR non-corrected/corrected adequate clinical and parasitological responses (ACPR) was 100.0% in both the AL and ASAQ arms. In Kedougou, PCR corrected ACPR values were 98.8%, 100% and 97.6% in AL, ASAQ and DP arms respectively. No Pfk13 or Pfcoronin mutations associated with artemisinin resistance were found. This study showed that AL, ASAQ and DP remain efficacious and well-tolerated in the treatment of uncomplicated P. falciparum malaria in Senegal.

A twenty-eight-year laboratory-based retrospective trend analysis of malaria in Dakar, Senegal.

INTRODUCTION: Health facility-based records offer a rich source of information to understand trends and changes in malaria cases over time. This study is aimed at determining the changes in malaria occurrence over the last 28 years, from 1989 to 2016 in Dakar, Senegal. METHODS: Laboratory suspected and confirmed malaria records from 1989 to 2016 were reviewed from the laboratory registers of the Laboratory of Parasitology and Mycology of Aristide Le Dantec Hospital. Interrupted time series (ITS) analysis was used to estimate the changes by comparing malaria cases post-intervention (2006-2016) with that of the pre-intervention (1989-2005) period. RESULTS: A total of 5,876 laboratory confirmed malaria cases were reported out of 29,852 tested cases, with total slide positivity rate (SPR) of 19.7%. Malaria case counts exhibited a fluctuating trend with major peaks occurring in the years 1995 and 2003 with SPR of 42.3% and 42.5%, respectively. Overall, a remarkable decline in the total number of laboratory confirmed malaria cases was observed over the last 28 years. P. falciparum was almost the only reported species, accounting for 99.98% of cases. The highest SPR was observed in the age group of under five years during the pre-intervention period while this shifted to the age group of 6-15 years old for the subsequent years. Two major malaria peak seasons were observed: one in September during the pre-intervention period and the other in November for the post-intervention period. The ITS analysis showed a dramatic decline of 83.6% in SPR following the scale-up of interventions in 2006. CONCLUSION: A remarkable decline in laboratory confirmed malaria cases in Dakar over 28 years was observed. The period of rapid decline in malaria SPR coincided with the scale-up in interventions beginning in 2006 with the introduction of ACTs, followed by the widespread introduction in 2008 of bed nets treated with insecticides. Robust surveillance data should be maintained in the context of malaria elimination efforts.

Clustering of asymptomatic Plasmodium falciparum infection and the effectiveness of targeted malaria control measures.

BACKGROUND: Because clustering of Plasmodium falciparum infection had been noted previously, the clustering of infection was examined at four field sites in West Africa: Dangassa and Dioro in Mali, Gambissara in The Gambia and Madina Fall in Senegal. METHODS: Clustering of infection was defined by the percent of persons with positive slides for asexual P. falciparum sleeping in a house which had been geopositioned. Data from each site were then tested for spatial, temporal and spatio-temporal clustering in relation to the prevalence of infection from smear surveys. RESULTS: These studies suggest that clustering of P. falciparum infection also affects the effectiveness of control interventions. For example, the clustering of infection in Madina Fall disappeared in 2014-2016 after vector control eliminated the only breeding site in 2013. In contrast, the temporal clustering of infection in Dioro (rainy season of 2014, dry season of 2015) was consistent with the loss of funding for Dioro in the second quarter of 2014 and disappeared when funds again became available in late 2015. The clustering of infection in rural (western) areas of Gambissara was consistent with known rural-urban differences in the prevalence of infection and with the thatched roofs, open eaves and mud walls of houses in rural Gambissara. In contrast, the most intense transmission was in Dangassa, where the only encouraging observation was a lower prevalence of infection in the dry season. Taken together, these results suggest: (a) the transmission of infection was stopped in Madina Fall by eliminating the only known breeding site, (b) the prevalence of infection was reduced in Dioro after financial support became available again for malaria control in the second half of 2015, (c) improvements in housing should improve malaria control by reducing the number of vectors in rural communities such as western Gambissara, and (d) beginning malaria control during the dry season may reduce transmission in hyperendemic areas such as Dangassa. CONCLUSIONS: From a conceptual perspective, testing for spatial, temporal and spatio-temporal clustering based on epidemiologic data permits the generation of hypotheses for the clustering observed and the testing of candidate interventions to confirm or refute those hypotheses.