Schistosomiasis control in Senegal: results from community data analysis for optimizing preventive chemotherapy intervention with praziquantel.

BACKGROUND: Over the past two decades, preventive chemotherapy (PC) with praziquantel (PZQ) is the major strategy for controlling schistosomiasis in Senegal. The objective of this analysis was to update the endemicity of schistosomiasis at community level for better targeting mass treatment with PZQ in Senegal. METHODS: Demographic and epidemiological data from 1610 community health areas were analyzed using the schistosomiasis community data analysis tool of Expanded Special Project for Elimination of Neglected Tropical Diseases which developed by World Health Organization/Africa Office (WHO/AFRO). The tool uses a WHO/AFRO decision tree for areas without epidemiological data to determine whether mass treatment should be continued at community level. Descriptive analysis was performed. RESULTS: Overall, the endemicity of 1610 community health areas were updated based on the data from the district endemicity (33.5%) and the form of Join request for selected PC medicine (40.5%). Up to 282 (17.5%) and 398 (24.7%) of community health areas were classified as moderate and high endemicity. 41.1% of communities were non endemic. High endemicity was more important in Tambacounda, Saint Louis, Matam, Louga and Kedougou. A change in endemicity category was observed when data was disagregted from district level to community level. Implementation units classified non endemic were more important at community level (n = 666) compared to district level (n = 324). Among 540 areas previously classified high endemic at district level, 392 (72.6%) remained high prevalence category, while 92 (17.0%) became moderate, 43 (8.0%) low and 13 (2.4%) non-endemics at community level. Number of implementation units requiring PC was more important at district level (1286) compared to community level (944). Number of school aged children requiring treatment was also more important at district level compared to community level. CONCLUSIONS: The analysis to disaggregate data from district level to community level using the WHO/AFRO schistosomiasis sub-district data optimization tool provide an update of schistosomiasis endemicity at community level. This study has allowed to better target schistosomiasis interventions, optimize use of available PZQ and exposed data gaps.

Effectiveness of seasonal malaria chemoprevention administered in a mass campaign in the Kedougou region of Senegal in 2016: a case-control study.

Background: Seasonal malaria chemoprevention (SMC) with sulfadoxine-pyrimethamine plus amodiaquine (SPAQ) is a malaria prevention strategy recommended since 2012 by the World Health Organization (WHO) for children under 5 years. In Senegal, the scaling up of SMC started in 2013 in the south-eastern regions of the country with an extension of the target to 10 years old children. The scaling up of SMC requires regular evaluation of the strategy as recommended by the WHO. This study was conducted to evaluate the effectiveness of SMC. Methods: A case-control study was conducted in some villages of the health districts of Saraya and Kedougou in the Kedougou region from July to December 2016. A case was a sick child, aged 3 months to 10 years, seen in consultation and with a positive malaria rapid diagnostic test (RDT). The control was a child of the same age group with a negative RDT and living in the same compound as the case or in a neighbouring compound. Each case was matched with two controls. Exposure to SMC was assessed by interviewing the mothers/caretakers and by checking the SMC administration card. Results: Overall, 492 children, including 164 cases and 328 controls, were recruited in our study. Their mean ages were 5.32 (+/- 2.15) and 4.44 (+/-2.25) years for cases and controls, respectively. The number of boys was higher in both cases (55.49%; CI 95%=47.54-63.24%) and controls (51,22%; CI 95%=45.83-56.58%). Net ownership was 85.80% among cases and 90.85% among controls (p=0,053). The proportion of controls who received SMC was higher than that of cases (98.17% vs 85.98% and p=1.10 -7). The protective effectiveness of SMC was 89% (OR= 0.12 (CI 95%=0.04-0.28)). Conclusions: SMC is an effective strategy in the control of malaria in children. Case-control studies are a good approach for monitoring the efficacy of drugs administered during SMC.

Malaria parasite carriage before and two years after the implementation of seasonal malaria chemoprevention: a case study of the Saraya health district, southern Senegal.

Background : Seasonal malaria chemoprevention (SMC) has been adopted and implemented in the southern regions of Senegal in children aged between three and 120 months since 2013. Scaling up this strategy requires its evaluation to assess the impact. This study was carried out to determine the dynamics of Plasmodium falciparum carriage before and after two years of SMC implementation. Methods : Four household surveys were conducted in villages in the health district of Saraya, which is a SMC implementation area in Senegal. These villages were selected using probability proportional to size sampling. Each selected village was divided into segments containing at least 50 children. In each segment, a household questionnaire was administered to the parents or legal representatives of children aged three to 120 months. Blood smears were collected to determine P. falciparum prevalence by microscopy one month before the first round of SMC, one month after the last round of the first SMC campaign and two years after the start of the implementation. Results : A total of 2008 children were included with a mean average age of 4.81 (+/-2.73) years. Of the study population, 50.33% were more than five years old and 50.3% were male. In 2013, mosquito net ownership was 99.4 % before the SMC campaign and 97.4% after. In 2015, it was 36.6% before and 45.8% after the campaign. In 2013, the prevalence of plasmodium carriage was 11.8% before and 6.1% after the SMC campaign. In 2015, the prevalence was 4.9% before the administration of SMC and this increased up to 15.3% after. Malaria prevalence was high among children over five years old and in boys. Conclusions : The decrease in Plasmodium falciparum parasite prevalence, which subsequently increased after two years of SMC implementation in this study, suggests adding an extra cycle of the SMC or adjusting the administration period.

[Epidemiology and response strategies against COVID-19: the Senegalese experience from 2020 to 2021]. / Epidémiologie et stratégies de riposte contre la COVID-19: l´expérience sénégalaise de 2020 à 2021.

Introduction: in response to the SARS-CoV-2 pandemic that reached Senegal in March 2020, the country has put in place several strategies to contain its spread. The purpose of this study was to describe the epidemiology and the strategies adopted. Méthods: we conducted a descriptive cross-sectional study of confirmed cases of COVID-19 using RT-PCR test in Senegal from March 2, 2020 to September 30, 2021. Data were collected through a literature review and analyzed with R and QGIS software. Proportions and means with standard deviation were calculated. Results: Senegal has recorded a total of 73,782 confirmed cases and 1,859 deaths from SARS-CoV-2. The temporal evolution was marked by three epidemic waves. The epidemic was concentrated in high-density areas such as Dakar (48,656 cases or 66%), in men (sex-ratio 1:13) and in the age group 25-34 years (16.527 cases or 22.4%). The average age of patients was 43 ± 18 years; the national cumulative incidence was 428 per 100,000 population and the overall case fatality rate was 2.5% (1,859/73,782). Some strategies have been implemented, including staff training, restrictive measures, home-based case management and vaccination. Nine point two percent (840,154/9,128,453) of the target population received 2 doses of vaccine. Conclusion: the epidemic was spread more widely within some population groups. We recommend strengthening preventive measures in high-density cities and mobilizing community networks to encourage immunization.

Correction to: Mass testing and treatment for malaria followed by weekly fever screening, testing and treatment in Northern Senegal: feasibility, cost and impact.

An amendment to this paper has been published and can be accessed via the original article.

Mass testing and treatment for malaria followed by weekly fever screening, testing and treatment in Northern Senegal: feasibility, cost and impact.

BACKGROUND: Population-wide interventions using malaria testing and treatment might decrease the reservoir of Plasmodium falciparum infection and accelerate towards elimination. Questions remain about their effectiveness and evidence from different transmission settings is needed. METHODS: A pilot quasi-experimental study to evaluate a package of population-wide test and treat interventions was conducted in six health facility catchment areas (HFCA) in the districts of Kanel, Linguère, and Ranérou (Senegal). Seven adjacent HFCAs were selected as comparison. Villages within the intervention HFCAs were stratified according to the 2013 incidences of passively detected malaria cases, and those with an incidence ≥ 15 cases/1000/year were targeted for a mass test and treat (MTAT) in September 2014. All households were visited, all consenting individuals were tested with a rapid diagnostic test (RDT), and, if positive, treated with dihydroartemisinin-piperaquine. This was followed by weekly screening, testing and treatment of fever cases (PECADOM++) until the end of the transmission season in January 2015. Villages with lower incidence received only PECADOM++ or case investigation. To evaluate the impact of the interventions over that transmission season, the incidence of passively detected, RDT-confirmed malaria cases was compared between the intervention and comparison groups with a difference-in-difference analysis using negative binomial regression with random effects on HFCA. RESULTS: During MTAT, 89% (2225/2503) of households were visited and 86% (18,992/22,170) of individuals were tested, for a combined 77% effective coverage. Among those tested, 291 (1.5%) were RDT positive (range 0-10.8 by village), of whom 82% were < 20 years old and 70% were afebrile. During the PECADOM++ 40,002 visits were conducted to find 2784 individuals reporting fever, with an RDT positivity of 6.5% (170/2612). The combination of interventions resulted in an estimated 38% larger decrease in malaria case incidence in the intervention compared to the comparison group (adjusted incidence risk ratio = 0.62, 95% CI 0.45-0.84, p = 0.002). The cost of the MTAT was $14.3 per person. CONCLUSIONS: It was operationally feasible to conduct MTAT and PECADOM++ with high coverage, although PECADOM++ was not an efficient strategy to complement MTAT. The modest impact of the intervention package suggests a need for alternative or complementary strategies.

Proactive community case management in Senegal 2014-2016: a case study in maximizing the impact of community case management of malaria.

The Senegal National Malaria Control Programme (NMCP) introduced home-based malaria management for all ages, with diagnosis by rapid diagnostic test (RDT) and treatment with artemisinin-based combination therapy (ACT) in 2008, expanding to over 2000 villages nationwide by 2014. With prise en charge à domicile (PECADOM), community health workers (CHWs) were available for community members to seek care, but did not actively visit households to find cases. A trial of a proactive model (PECADOM Plus), in which CHWs visited all households in their village weekly during transmission season to identify fever cases and offer case management, in addition to availability during the week for home-based management, found that CHWs detected and treated more cases in intervention villages, while the number of cases detected weekly decreased over the transmission season. The NMCP scaled PECADOM Plus to three districts in 2014 (132 villages), to a total of six districts in 2015 (246 villages), and to a total of 16 districts in 2016 (708 villages). A narrative case study with programmatic results is presented. During active sweeps over approximately 20 weeks, CHWs tested a mean of 77 patients per CHW in 2014, 89 patients per CHW in 2015, and 90 patients per CHW in 2016, and diagnosed a mean of 61, 61 and 43 patients with malaria per CHW in 2014, 2015 and 2016, respectively. The number of patients who sought care between sweeps increased, with a 104% increase in the number of RDTs performed and a 77% increase in the number of positive tests and patients treated with ACT during passive case detection. While the number of CHWs increased 7%, the number of patients receiving an RDT increased by 307% and the number of malaria cases detected and treated by CHWs increased 274%, from the year prior to PECADOM Plus introduction to its first year of implementation. Based on these results, approximately 700 additional CHWs in 24 new districts were added in 2017. This case study describes the process, results and lessons learned from Senegal's implementation of PECADOM Plus, as well as guidance for other programmes considering introduction of this innovative strategy.

Malaria prevalence, prevention and treatment seeking practices among nomadic pastoralists in northern Senegal.

BACKGROUND: Malaria transmission in Senegal is highly stratified, from low in the dry north to moderately high in the moist south. In northern Senegal, along the Senegal River Valley and in the Ferlo semi-desert region, annual incidence is less than five cases per 1000 inhabitants. Many nomadic pastoralists have permanent dwellings in the Ferlo Desert and Senegal River Valley, but spend dry season in the south with their herds, returning north when the rains start, leading to a concern that this population could contribute to ongoing transmission in the north. METHODS: A modified snowball sampling survey was conducted at six sites in northern Senegal to determine the malaria prevention and treatment seeking practices and parasite prevalence among nomadic pastoralists in the Senegal River Valley and the Ferlo Desert. Nomadic pastoralists aged 6 months and older were surveyed during September and October 2014, and data regarding demographics, access to care and preventive measures were collected. Parasite infection was detected using rapid diagnostic tests (RDTs), microscopy (thin and thick smears) and polymerase chain reaction (PCR). Molecular barcodes were determined by high resolution melting (HRM). RESULTS: Of 1800 participants, 61% were male. Sixty-four percent had at least one bed net in the household, and 53% reported using a net the night before. Only 29% had received a net from a mass distribution campaign. Of the 8% (142) who reported having had fever in the last month, 55% sought care, 20% of whom received a diagnostic test, one-third of which (n = 5) were reported to be positive. Parasite prevalence was 0.44% by thick smear and 0.50% by PCR. None of the molecular barcodes identified among the nomadic pastoralists had been previously identified in Senegal. CONCLUSIONS: While access to and utilization of malaria control interventions among nomadic pastoralists was lower than the general population, parasite prevalence was lower than expected and sheds doubt on the perception that they are a source of ongoing transmission in the north. The National Malaria Control Program is making efforts to improve access to malaria prevention and case management for nomadic populations.

Declines in Malaria Burden and All-Cause Child Mortality following Increases in Control Interventions in Senegal, 2005-2010.

Malaria is endemic in Senegal. The national malaria control strategy focuses on achieving universal coverage for major interventions, with a goal of reaching preelimination status by 2018. Senegal began distribution of insecticide-treated nets (ITNs) and introduced artemisinin-based combination therapy in 2006, then introduced rapid diagnostic tests in 2007. We evaluated the impact of these efforts using a plausibility design based on malaria's contribution to all-cause under-five mortality (ACCM) and considering other contextual factors which may influence ACCM. Between 2005 and 2010, household ownership of ITNs increased from 20% to 63%, and the proportion of people sleeping under an ITN the night prior to the survey increased from 6% to 29%. Malaria parasite prevalence declined from 6% to 3% from 2008 to 2010 among children under five. Some nonmalaria indicators of child health improved, for example, increase of complete vaccination coverage from 58% to 64%; however, nutritional indicators deteriorated, with an increase in stunting from 16% to 26%. Although economic indicators improved, environmental conditions favored an increase in malaria transmission. ACCM decreased 40% between 2005 and 2010, from 121 (95% confidence interval [CI] 113-129) to 72 (95% CI 66-77) per 1,000, and declines were greater among age groups, epidemiologic zones, and wealth quintiles most at risk for malaria. After considering coverage of malaria interventions, trends in malaria morbidity, effects of contextual factors, and trends in ACCM, it is plausible that malaria control interventions contributed to a reduction in malaria mortality and to the impressive gains in child survival in Senegal.

Assessment of the utility of a symptom-based algorithm for identifying febrile patients for malaria diagnostic testing in Senegal.

BACKGROUND: Malaria rapid diagnostic tests (RDTs) enable point-of-care testing to be nearly as sensitive and specific as reference microscopy. The Senegal National Malaria Control Programme introduced RDTs in 2007, along with a case management algorithm for uncomplicated febrile illness, in which the first step stipulates that if a febrile patient of any age has symptoms indicative of febrile illness other than malaria (e.g., cough or rash), they would not be tested for malaria, but treated for the apparent illness and receive an RDT for malaria only if they returned in 48 h without improvement. METHODS: A year-long study in 16 health posts was conducted to determine the algorithm's capacity to identify patients with Plasmodium falciparum infection identifiable by RDT. Health post personnel enrolled patients of all ages with fever (≥37.5 °C) or history of fever in the previous 2 days. After clinical assessment, a nurse staffing the health post determined whether a patient should receive an RDT according to the diagnostic algorithm, but performed an RDT for all enrolled patients. RESULTS: Over 1 year, 6039 patients were enrolled and 58% (3483) were determined to require an RDT according to the algorithm. Overall, 23% (1373/6039) had a positive RDT, 34% (1130/3376) during rainy season and 9% (243/2661) during dry season. The first step of the algorithm identified only 78% of patients with a positive RDT, varying by transmission season (rainy 80%, dry 70%), malaria transmission zone (high 75%, low 95%), and age group (under 5 years 68%, 5 years and older 84%). CONCLUSIONS: In all but the lowest malaria transmission zone, use of the algorithm excludes an unacceptably large proportion of patients with malaria from receiving an RDT at their first visit, denying them timely diagnosis and treatment. While the algorithm was adopted within a context of malaria control and scarce resources, with the goal of treating patients with symptomatic malaria, Senegal has now adopted a policy of universal diagnosis of patients with fever or history of fever. In addition, in the current context of malaria elimination, the paradigm of case management needs to shift towards the identification and treatment of all patients with malaria infection.

Evidence of non-Plasmodium falciparum malaria infection in Kédougou, Sénégal.

BACKGROUND: Expanded malaria control efforts in Sénégal 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 Sénégal 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 Sénégal. This study set out to better determine whether species other than P. falciparum were evident among patients evaluated for possible malaria infection in Kédougou, Sénégal. 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 Kédougou, a hyper-endemic region in southeastern Sénégal, 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 Sénégal. Current RDT used for routine clinical diagnosis do not necessarily provide an accurate reflection of malaria transmission in Kédougou, Sénégal, 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.

Modeling malaria genomics reveals transmission decline and rebound in Senegal.

To study the effects of malaria-control interventions on parasite population genomics, we examined a set of 1,007 samples of the malaria parasite Plasmodium falciparum collected in Thiès, Senegal between 2006 and 2013. The parasite samples were genotyped using a molecular barcode of 24 SNPs. About 35% of the samples grouped into subsets with identical barcodes, varying in size by year and sometimes persisting across years. The barcodes also formed networks of related groups. Analysis of 164 completely sequenced parasites revealed extensive sharing of genomic regions. In at least two cases we found first-generation recombinant offspring of parents whose genomes are similar or identical to genomes also present in the sample. An epidemiological model that tracks parasite genotypes can reproduce the observed pattern of barcode subsets. Quantification of likelihoods in the model strongly suggests a reduction of transmission from 2006-2010 with a significant rebound in 2012-2013. The reduced transmission and rebound were confirmed directly by incidence data from Thiès. These findings imply that intensive intervention to control malaria results in rapid and dramatic changes in parasite population genomics. The results also suggest that genomics combined with epidemiological modeling may afford prompt, continuous, and cost-effective tracking of progress toward malaria elimination.

Case investigation and reactive case detection for malaria elimination in northern Senegal.

BACKGROUND: Given progress in malaria control in recent years, many control programmes in sub-Saharan Africa will soon be required to strengthen systems for surveillance in order to further drive transmission to zero. Yet few practical experiences are available to guide control programmes in designing surveillance system components in low transmission, pre-elimination, and elimination phases. METHODS: A malaria case investigation programme was piloted for 12 weeks in 2012 in Richard Toll district of northern Senegal. Malaria infections (N = 110) were identified through facility-based passive case detection and investigated within three days. Rapid diagnostic tests (RDT) and a brief questionnaire were administered to 5,520 individuals living within the index case compound or within five neighbouring compounds. RESULTS: In comparison with family and neighbours, index cases were more likely to be male, age 15-49, and to report travel within the past 15 days that entailed an overnight stay. Twenty-three (0.4%) of family/neighbours were RDT-positive. Potential risk factors for infection among family and neighbours were examined, including: sex, age, occupation, travel history, bed net usage, and residence (index vs neighbouring compound). Adjusting for all factors, relative risk (RR) of infection was associated with residence in the index case household (RR = 3.18, p < 0.05) and recent travel, including travel to Dakar (RR = 19.93, p < 0.001), travel within the region (RR = 9.57, p < 0.01), and to other regions in Senegal (RR = 94.30, p < 0.001). Recent fever among RDT-positive family/neighbours was uncommon (30%). Modifications to testing criteria were examined to optimize the efficiency of secondary case investigations in this population. Limiting blood testing to residents of the index case compound and neighbours with recent travel or fever would have identified 20/23 (87%) of the infections through testing 1,173 individuals. Information on the remaining three infections suggests that additional screening for boarding school attendees may facilitate identification of all cases. CONCLUSIONS: The primary risk factor for malaria infection in the low transmission district of Richard Toll is travel. Additional intervention and monitoring strategies to target travellers at risk of malaria infection are needed in this region. Optimizing case investigation with specific targeted testing and treatment of at-risk family and neighbours strengthens the systems needed for continued progress towards malaria elimination in northern Senegal.

Spread of Influenza A(H1N1) oseltamivir-resistant viruses in Africa in 2008 confirmed by multiple introductions in Senegal.

BACKGROUND: Among Influenza neuraminidase inhibitors (NAIs), oseltamivir corresponds to the most widely used agent to treat influenza disease. However since 2001, several cases of resistance to NAIs have been reported for circulating seasonal A(H1N1) Influenza viruses. A direct resistance mechanism may be invoked, involving critical mutations in the viral NA gene that prevent the drug binding to its target. Same phenomenon is reported for adamantanes drugs and mutations in the M2 channel protein gene of Influenza viruses. METHODS: Reverse-Transcription/Restriction Fragment Length Polymorphism (RT-PCR/RFLP) method, phenotypic testing for oseltamivir resistance, and sequencing of NA, HA and M2 genes were used in this study. Phylogenetic analyses were performed using BioEdit and Mega 5 softwares for alignment of sequences and phylogenetic trees building respectively. RESULTS: Using a simple RT-PCR/RFLP method, we found that the 86 seasonal A(H1N1) isolates from 2008 bear the oseltamivir resistance-associated mutation (H274Y) in the NA gene. In contrast all isolates isolated in Senegal in 2007 were sensitive to oseltamivir. These results were first confirmed by finding high IC50 values using a phenotypic testing for oseltamivir resistance, and secondly by sequencing the whole NA gene. Regarding M2 gene, no mutation associated to adamantanes resistance was characterized of the isolates. CONCLUSIONS: The present work provides evidence of circulation of drug-resistant seasonal A(H1N1) viruses during the 2008 influenza season (July to September) in Senegal. The results are in favor of multiple introductions of oseltamivir resistant viruses (ORV) A(H1N1) in Senegal.Phylogenetic analyses of isolates with complete sequences of N1 and HA1 genes showed that they belong to clade 2B and suggest sequential introductions in Africa.

Effectiveness of haemophilus influenzae type B conjugate vaccine for prevention of meningitis in Senegal.

A total of 24 cases of hospitalized, laboratory-confirmed Haemophilus influenzae type b (Hib) meningitis were identified through a regional pediatric bacterial meningitis surveillance system. Each case was matched by age and residence to 4 neighborhood controls. The adjusted vaccine effectiveness for ≥ 2 doses was 95.8% (95% confidence interval, 67.9%-99.4%). Hib vaccine appears to be highly effective in preventing Hib meningitis in Senegal.

Hospital surveillance of childhood bacterial meningitis in Senegal and the introduction of Haemophilus influenzae type b conjugate vaccine.

Bacterial meningitis is an important cause of morbidity and mortality in children living in low-resource settings. Pediatric bacterial meningitis cases < 5 years of age were identified through a regional hospital surveillance system for 3 years after introduction of routine immunization with Haemophilus influenzae type b (Hib) conjugate vaccine in Senegal in July 2005. Cases from the national pediatric hospital were also tracked from 2002 to 2008. The regional surveillance system recorded 1,711 suspected pediatric bacterial meningitis cases. Of 214 laboratory-confirmed cases, 108 (50%) were caused by Streptococcus pneumoniae, 42 (20%) to Hib, and 13 (6%) to Neisseria meningitidis. There was a 98% reduction in the number of hospitalized Hib meningitis cases from Dakar Region in 2008 compared with 2002. The surveillance system provides important information to the Ministry of Health as they consider self-funding Hib vaccine and introducing pneumococcal vaccine.