Chikungunya Outbreak in Country with Multiple Vectorborne Diseases, Djibouti, 2019-2020.

During 2019-2020, a chikungunya outbreak occurred in Djibouti City, Djibouti, while dengue virus and malaria parasites were cocirculating. We used blotting paper to detect arbovirus emergence and confirm that it is a robust method for detecting and monitoring arbovirus outbreaks remotely.

Malaria prevalence in Mauritania: a systematic review and meta-analysis.

BACKGROUND: Understanding malaria epidemiology is a critical step toward efficient malaria control and elimination. The objective of this meta-analysis was to derive robust estimates of malaria prevalence and Plasmodium species from studies conducted in Mauritania and published since 2000. METHODS: The present review followed the PRISMA guidelines. Searches were conducted in various electronic databases such as PubMed, Web of Science, and Scopus. To obtain pooled prevalence of malaria, meta-analysis was performed using the DerSimonian-Laird random-effects model. Methodological quality of eligible prevalence studies was assessed using Joanna Briggs Institute tool. Inconsistency and heterogeneity between studies were quantified by the I2 index and Cochran's Q test. Publication bias was assessed with funnel plots and Egger's regression tests. RESULTS: A total of 16 studies with a good individual methodological quality were included and analysed in this study. The overall random effects pooled prevalence of malaria infection (symptomatic and asymptomatic) across all included studies was 14.9% (95% confidence interval [95% CI]: 6.64, 25.80, I2 = 99.8%, P < 0.0001) by microscopy, 25.6% (95% CI: 8.74, 47.62, I2 = 99.6%, P < 0.0001) by PCR and 24.3% (95% CI: 12.05 to 39.14, I2 = 99.7%, P < 0.0001) by rapid diagnostic test. Using microscopy, the prevalence of asymptomatic malaria was 1.0% (95% CI: 0.00, 3.48) against 21.46% (95% CI: 11.03, 34.21) in symptomatic malaria. The overall prevalence of Plasmodium falciparum and Plasmodium vivax was 51.14% and 37.55%, respectively. Subgroup analysis showed significant variation (P = 0.039) in the prevalence of malaria between asymptomatic and symptomatic cases. CONCLUSION: Plasmodium falciparum and P. vivax are widespread in Mauritania. Results of this meta-analysis implies that distinct intervention measures including accurate parasite-based diagnosis and appropriate treatment of confirmed malaria cases are critical for a successful malaria control and elimination programme in Mauritania.

Changing epidemiology of Plasmodium vivax malaria in Nouakchott, Mauritania: a six-year (2015-2020) prospective study.

BACKGROUND: Plasmodium vivax malaria is one of the major infectious diseases of public health concern in Nouakchott, the capital city of Mauritania and the biggest urban setting in the Sahara. The assessment of the current trends in malaria epidemiology is primordial in understanding the dynamics of its transmission and developing an effective control strategy. METHODS: A 6 year (2015-2020) prospective study was carried out in Nouakchott. Febrile outpatients with a clinical suspicion of malaria presenting spontaneously at Teyarett Health Centre or the paediatric department of Mother and Children Hospital Centre were screened for malaria using a rapid diagnostic test, microscopic examination of Giemsa-stained blood films, and nested polymerase chain reaction. Data were analysed using Microsoft Excel and GraphPad Prism and InStat software. RESULTS: Of 1760 febrile patients included in this study, 274 (15.5%) were malaria-positive by rapid diagnostic test, 256 (14.5%) were malaria-positive by microscopy, and 291 (16.5%) were malaria-positive by PCR. Plasmodium vivax accounted for 216 of 291 (74.2%) PCR-positive patients; 47 (16.1%) and 28 (9.6%) had P. falciparum monoinfection or P. vivax-P. falciparum mixed infection, respectively. During the study period, the annual prevalence of malaria declined from 29.2% in 2015 to 13.2% in 2019 and 2.1% in 2020 (P < 0.05). Malaria transmission was essentially seasonal, with a peak occurring soon after the rainy season (October-November), and P. vivax infections, but not P. falciparum infections, occurred at low levels during the rest of the year. The most affected subset of patient population was adult male white and black Moors. The decline in malaria prevalence was correlated with decreasing annual rainfall (r = 0.85; P = 0.03) and was also associated with better management of the potable water supply system. A large majority of included patients did not possess or did not use bed nets. CONCLUSIONS: Control interventions based on prevention, diagnosis, and treatment should be reinforced in Nouakchott, and P. vivax-specific control measures, including chloroquine and 8-aminoquinolines (primaquine, tafenoquine) for treatment, should be considered to further improve the efficacy of interventions and aim for malaria elimination.

Modeling intra-mosquito dynamics of Zika virus and its dose-dependence confirms the low epidemic potential of Aedes albopictus.

Originating from African forests, Zika virus (ZIKV) has now emerged worldwide in urbanized areas, mainly transmitted by Aedes aegypti mosquitoes. Although Aedes albopictus can transmit ZIKV experimentally and was suspected to be a ZIKV vector in Central Africa, the potential of this species to sustain virus transmission was yet to be uncovered until the end of 2019, when several autochthonous transmissions of the virus vectored by Ae. albopictus occurred in France. Aside from these few locally acquired ZIKV infections, most territories colonized by Ae. albopictus have been spared so far. The risk level of ZIKV emergence in these areas remains however an open question. To assess Ae. albopictus' vector potential for ZIKV and identify key virus outbreak predictors, we built a complete framework using the complementary combination of (i) dose-dependent experimental Ae. albopictus exposure to ZIKV followed by time-dependent assessment of infection and systemic infection rates, (ii) modeling of intra-human ZIKV viremia dynamics, and (iii) in silico epidemiological simulations using an Agent-Based Model. The highest risk of transmission occurred during the pre-symptomatic stage of the disease, at the peak of viremia. At this dose, mosquito infection probability was estimated to be 20%, and 21 days were required to reach the median systemic infection rates. Mosquito population origin, either temperate or tropical, had no impact on infection rates or intra-host virus dynamic. Despite these unfavorable characteristics for transmission, Ae. albopictus was still able to trigger and yield large outbreaks in a simulated environment in the presence of sufficiently high mosquito biting rates. Our results reveal a low but existing epidemic potential of Ae. albopictus for ZIKV, that might explain the absence of large scale ZIKV epidemics so far in territories occupied only by Ae. albopictus. They nevertheless support active surveillance and eradication programs in these territories to maintain the risk of emergence to a low level.

Prevalence of malaria among febrile patients and assessment of efficacy of artemether-lumefantrine and artesunate-amodiaquine for uncomplicated malaria in Dolisie, Republic of the Congo.

BACKGROUND: In the Republic of the Congo, malaria represents a major public health problem affecting all age groups. A regular surveillance of the current efficacy of first-line anti-malarial drugs is required in the face of possible emergence and spread of artemisinin-resistant Plasmodium falciparum strains in Africa. The purpose of this study was to determine the prevalence of malaria among febrile patients of all ages and assess the efficacy of artemether-lumefantrine (AL) and artesunate-amodiaquine (ASAQ) in Congolese children. METHODS: Febrile patients of all ages were initially screened for malaria by both rapid diagnostic test (RDT) and microscopy. Patients less than 12 years of age, with parasitaemia ≥ 1000 asexual parasites of P. falciparum/µL of blood, without any signs of severity, were enrolled in a therapeutic efficacy study and treated after obtaining their parents' (or legal guardian's) informed consent in two health centres in Dolisie. The patients were followed for 28 days in accordance with the 2009 World Health Organization standard protocol. If parasitaemia reappeared on or after day 7, the genetic profiles (genes expressing merozoite surface protein-1 [msp1], merozoite surface protein-2 [msp2], and glutamine-rich protein [glurp]) of pre-treatment and post-treatment isolates were compared by nested polymerase chain reaction (PCR) followed by capillary electrophoresis to make a distinction between recrudescence and re-infection. The clinical and parasitological outcome was analysed by the per-protocol method and Kaplan-Meier survival curves. RESULTS: A total of 994 febrile patients of all ages were screened by RDT and microscopy. Of 994 patients, 323 (32.5%) presented a positive RDT, and 266 (26.8%) were microscopy-positive. Based on microscopy as the reference diagnostic method, the sensitivity and the specificity of the RDT were 98.9 and 91.8%, respectively. The Cohen's kappa coefficient was 0.86. A total of 121 children aged less than 12 years (61 in AL treatment group and 60 in ASAQ treatment group) were included in therapeutic efficacy study. Before PCR correction, the proportions of adequate clinical and parasitological response were 96.6% for AL and 86.0% for ASAQ in the per-protocol population (P < 0.05). The PCR-corrected efficacy rates were 98.2% and 94.2% for AL and ASAQ, respectively (P > 0.05). Both treatments were well tolerated. CONCLUSIONS: AL and ASAQ remain highly effective for the first-line treatment of uncomplicated P. falciparum malaria in Dolisie. Despite high efficacy of first- and second-line treatment, there is a continuing need to scale up effective malaria preventive interventions and vector control strategies in the country. TRIAL REGISTRATION NUMBER: ACTRN12616001422415.

Role of Anopheles stephensi Mosquitoes in Malaria Outbreak, Djibouti, 2019.

Anopheles stephensi mosquitoes share urban breeding sites with Aedes aegypti and Culex quinquefasciatus mosquitoes in the Republic of Djibouti. We present evidence that A. stephensi mosquitoes might be responsible for an increase in malaria incidence in this country. We also document resistance of Plasmodium falciparum to dihydroartemisinin/piperaquine.

Baseline and multinormal distribution of ex vivo susceptibilities of Plasmodium falciparum to methylene blue in Africa, 2013-18.

BACKGROUND: Plasmodium falciparum resistance to most antimalarial compounds has emerged in Southeast Asia and spread to Africa. In this context, the development of new antimalarial drugs is urgent. OBJECTIVES: To determine the baseline in vitro activity of methylene blue (Proveblue®) on African isolates and to determine whether parasites have different phenotypes of susceptibility to methylene blue. METHODS: Ex vivo susceptibility to methylene blue was measured for 609 P. falciparum isolates of patients hospitalized in France for malaria imported from Africa. A Bayesian statistical analysis was designed to describe the distribution of median effective concentration (EC50) estimates. RESULTS: The EC50 ranged from 0.16 to 87.2 nM with a geometric mean of 7.17 nM (95% CI = 6.21-8.13). The 609 EC50 values were categorized into four components: A (mean = 2.5 nM; 95% CI = 2.28-2.72), B (mean = 7.44 nM; 95% CI = 7.07-7.81), C (mean = 16.29 nM; 95% CI = 15.40-17.18) and D (mean = 38.49 nM; 95% CI = 34.14-42.84). The threshold value for in vitro reduced susceptibility to methylene blue was estimated at 35 nM using the geometric mean of EC50 plus 2 SDs of the 609 isolates. This cut-off also corresponds to the lower limit of the 95% CI of the methylene blue EC50 of component D. Thirty-five isolates (5.7%) displayed EC50 values above this threshold. CONCLUSIONS: Methylene blue exerts a promising efficacy against P. falciparum and is a potential partner for triple combinations.

Performance of 2 Commercial Serologic Tests for Diagnosing Zika Virus Infection.

Reliable serologic tests are needed for diagnosis and surveillance of Zika virus infection. We evaluated the Euroimmun and Dia.Pro serologic tests for detection of Zika virus IgM and IgG by using a panel of 199 samples from a region endemic for flaviviruses. Kinetics of Zika virus antibodies were monitored from 300 sequential specimens sampled over a period of 10 months after infection. We observed suboptimal performance; sensitivity for Zika virus IgM was low, especially in the Euroimmun assay (49%), whereas IgM could be detected for months with the Dia.pro assay. The specificity of the Zika virus IgG assays was also low, especially that of Dia.Pro (62%); findings were strongly influenced by the epidemiologic context. These results highlight the complexity of serologic diagnosis of Zika virus infection in regions endemic for flaviviruses. Accurate analysis of the performance of assays is required to adapt and interpret algorithms.

Investigation of a possible malaria epidemic in an illegal gold mine in French Guiana: an original approach in the remote Amazonian forest.

BACKGROUND: In April 2017, Suriname's Ministry of Health alerted French Guiana's Regional Health Agency (RHA) about an increase of imported malaria cases among people coming from an illegal gold mining site called Sophie, in French Guiana, a French overseas territory located in the Amazonian forest. METHODS: Due to safety issues and the remoteness of Sophie, the RHA requested the collaboration of the French Armed Forces for the epidemiological investigation. A medical unit, and six soldiers to ensure the security of the mission, were transported by helicopter. RESULTS: During the investigation, two malaria episodes were diagnosed among 46 persons. Twenty-six of them were from Sophie, where PCR-Plasmodium prevalence was estimated at 60% (15/26). This result was concordant with previous studies revealing high malaria endemicity in the gold miner population. The increase of imported cases in Suriname may have resulted from decreased access to under-the-counter anti-malarials and increased migration of gold miners to Suriname following a decline of the profitability of gold mining in a context of increased repression against illegal mining by the French army. CONCLUSION: This investigation of a suspicious malaria epidemic confirms the importance of malaria among illegal gold miners. Their mobility along the Guiana Shield and their health-seeking behaviour are likely to spread malaria in populations for which significant efforts are undertaken to fight against this disease. Fighting malaria in this population remains more relevant than ever. A pilot study (Malakit project) is currently in progress to evaluate the efficacy of kits for self-diagnosis and self-treatment.

Tracking Rift Valley fever: From Mali to Europe and other countries, 2016.

On 16 September 2016, the World Health Organization confirmed a Rift Valley fever (RVF) outbreak in Niger. Epidemiological surveillance was reinforced among the French Armed Forces deployed in Niger and bordering countries: Chad, Mali and Burkina Faso. On 26 October, a probable case of RVF was reported in a service member sampled in Mali 3 weeks earlier. At the time the result was reported, the patient was on vacation on Martinique. An epidemiological investigation was conducted to confirm this case and identify other cases. Finally, the case was not confirmed, but three suspected cases of RVF were confirmed using serological and molecular testing. RVF viral RNA was detectable in whole blood for 57 and 67 days after onset of symptoms for two cases, although it was absent from plasma and serum. At the time of diagnosis, these cases had already returned from Mali to Europe. The infectivity of other arboviruses in whole blood has already been highlighted. That RVF virus has been detected in whole blood that long after the onset of symptoms (67 days) raises the question of its potential prolonged infectivity. Because of exposure to tropical infectious diseases during deployment, military populations could import emerging pathogens to Europe.