Evaluation of a novel biplex rapid diagnostic test for antibody responses to Loa loa and Onchocerca volvulus infections.

BACKGROUND: Endemic to Central Africa, loiasis, caused by the vector-borne worm Loa loa, affects approximately 10 million individuals. Clinical manifestations include transient angioedema (Calabar swellings), migration of the adult worm under the eye conjunctiva (eye worm) and less specific general symptoms. Loiasis presents a significant public health challenge because L. loa-infected individuals can develop serious adverse events after taking ivermectin, the drug used to combat onchocerciasis. In this context, alternative interventions and rigorous diagnostic approaches are needed. Diagnosing loiasis is challenging because its main clinical manifestations are sporadic and non-specific. The definitive diagnosis relies on identifying adult worms migrating beneath the conjunctiva, or microfilariae (pre-larvae) in blood smears. However, "occult loiasis" (infection without blood microfilariae) is frequent. Serological rapid antibody diagnostic tests (ARTs) can provide an alternative diagnostic method. We compared a novel ART simultaneously targeting onchocerciasis (IgG4 to Ov-16 and OvOC3261, test line 1) and loiasis (IgG4 to L1-SXP-1, test line 2), called IgG4-SXP-1 biplex test) to the already established Loa-ART (all IgG isotypes to Ll-SXP-1, called pan-IgG-SXP-1 test). METHODOLOGY: Blood samples underwent both ARTs, read qualitatively and semi-quantitatively. Additionally, blood smears, skin snips, Kato-Katz method for soil-transmitted helminthiases identification and eosinophilia measurements were performed. Questionnaires gathered demographic details and loiasis-related signs. ARTs performance was compared using specific loiasis-related signs and microfilaremia as references. Discordances between the two ARTs were investigated using logistic regression models. PRINCIPAL FINDINGS: Out of 971 participants, 35.4% had L. loa microfilaremia, 71.9% had already experienced loiasis-related signs, 85.1% were positive in the pan-IgG-SXP-1 test and 79.4% were positive in the IgG4-SXP-1 biplex test. In the microfilariae-positive population, the sensitivity of the rapid tests was 87.4% for the pan-IgG-SXP-1 test and 88.6% for the prototype IgG4-SXP-1 biplex test. Sensitivity was similar for both ARTs when using eye worm or Calabar swelling as references, but diagnostic performance varied based on microfilaremia levels and occult loiasis. Overall, IgG4-SXP-1 biplex test demonstrated a sensitivity of 84.1% and specificity of 47.6% for loiasis compared to the pan-IgG-SXP-1 test, leading to a Kappa coefficient estimated at 0.27 ± 0.03 for the qualitative results of the 2 ARTs. In the group that tested positive with the Pan-IgG test but negative with the IgG4-specific test, there was a lower prevalence of STH infection (p = 0.008) and elevated eosinophilia (p<0.001) compared to the general tested population. CONCLUSION/SIGNIFICANCE: The sensitivity of each test was good (84-85%) but the diagnostic agreement between the two ARTs was poor, suggesting that IgG and IgG4 antibody responses should be interpreted differently. The assessment of the innovative rapid diagnostic IgG4-SXP-1 biplex test, designed for onchocerciasis and loiasis, shows encouraging sensitivity but underlines the necessity for further in vitro assessment.

Safety and Short-term Efficacy of a Single Dose of 2†mg Moxidectin in Loa loa-Infected Individuals: A Double-Blind, Randomized Ivermectin-Controlled Trial With Ascending Microfilarial Densities.

Background: In 2018, the US Food and Drug Administration approved the macrocylic lactone moxidectin (MOX) at 8 mg dosage for onchocerciasis treatment in individuals aged ≥12 years. Severe adverse reactions have occurred after ivermectin (IVM), also a macrocyclic lactone, in individuals with high Loa microfilarial density (MFD). This study compared the safety and efficacy of a 2 mg MOX dose and the standard 150 µg/kg IVM dose in individuals with low L loa MFD. Methods: A double-blind, randomized, ivermectin-controlled trial of a 2 mg moxidectin dose was conducted in Cameroon between May and July 2022. It enrolled 72 adult men with L loa MFD between 5 and 1000 microfilariae/mL. Outcomes were occurrence of adverse events (AEs) and L loa MFD reduction rate during the first month off treatment. Results: No serious or severe AEs occurred among the 36 MOX- or the 36 IVM-treated individuals. Forty-nine AEs occurred in the MOX arm versus 59 AEs in the IVM arm. Grade 2 AE incidence was higher among IVM- than MOX-treated participants (38.5% and 14.3%, respectively, P = .043). Median MFD reduction rates were significantly higher after IVM than MOX at day 3 (70.2% vs 48.5%), day 7 (76.4% vs 50.0%), and day 30 (79.8% vs 48.1%). Conclusions: A single 2 mg MOX dose is as safe as 150 µg/kg IVM in patients with low L loa MFD. Further studies with higher MOX doses and in patients with higher MFD are warranted. Clinical Trials Registration: NCT04049851.

Association between arterial stiffness and Loa loa microfilaremia in a rural area of the Republic of Congo: A population-based cross-sectional study (the MorLo project).

BACKGROUND: Loa loa filariasis (loiasis) is still considered a relatively benign disease. However, recent epidemiologic data suggest increased mortality and morbidity in L. loa infected individuals. We aimed to examine whether the density of L. loa microfilariae (mfs) in the blood is associated with cardiovascular disease. METHODOLOGY: Using a point-of-care device (pOpmètre), we conducted a cross-sectional study to assess arterial stiffness and peripheral arterial disease (PAD) in 991 individuals living in a loiasis-endemic rural area in the Republic of the Congo. Microfilaremic individuals were matched for age, sex and village of residence with 2 amicrofilaremic subjects. We analyzed markers of arterial stiffness (Pulse-Wave Velocity, PWV), PAD (Ankle-Brachial Index, ABI) and cardiovascular health (Pulse Pressure, PP). The analysis considered parasitological results (L. loa microfilarial density [MFD], soil-transmitted helminths infection, asymptomatic malaria and onchocerciasis), sociodemographic characteristics and known cardiovascular risk factors (body mass index, smoking status, creatininemia, blood pressure). PRINCIPAL FINDINGS: Among the individuals included in the analysis, 192/982 (19.5%) and 137/976 (14.0%) had a PWV or an ABI considered out of range, respectively. Out of range PWV was associated with younger age, high mean arterial pressure and high L. loa MFD. Compared to amicrofilaremic subjects, those with more than 10,000 mfs/mL were 2.17 times more likely to have an out of range PWV (p = 0.00). Factors significantly associated with PAD were older age, low pulse rate, low body mass index, smoking, and L. loa microfilaremia. Factors significantly associated with an elevation of PP were older age, female sex, high average blood pressure, low pulse rate and L. loa microfilaremia. CONCLUSION: A potential link between high L. loa microfilaremia and cardiovascular health deterioration is suggested. Further studies are required to confirm and explore this association.

Significant reduction of blackfly densities in persistent onchocerciasis area following pilot implementation of an environment friendly approach (Slash and Clear).

The effectiveness of the "Slash and Clear" method in reducing blackfly populations in low transmission areas is established, but its impact in high transmission settings with large rivers and dense vectors is yet to be proven. A community-based intervention study was conducted in the Mbam Valley, Centre Cameroon, involving two sites: Bayomen (control) and Biatsota (intervention). In each arm, baseline blackfly densities were collected over one year using the human landing method. The intervention consisted of destroying the trailing vegetation where blackflies breed. Blackfly densities were collected post-intervention to assess the impact of the intervention. Post-intervention data showed a 50.8% reduction in blackfly density in Biatsota (mean number of collected blackflies from 1936 to 953), while a reduction of 26.7% was observed in Bayomen (mean number of collected blackflies from 2418 to 1774). The reduction rate attributable to the intervention was 32.9%. Statistical analysis confirmed that the reduction in blackfly density was significantly greater in the intervention site. This study demonstrates the feasibility and significant impact of the "Slash and Clear" method in high transmission areas. However, further research is required to assess its long-term effects and determine how this strategy can be scaled up and sustained until onchocerciasis elimination is achieved.

Treatment and prevention of epilepsy in onchocerciasis-endemic areas is urgently needed.

BACKGROUND: There is increasing epidemiological evidence supporting the association between onchocerciasis and seizures, reinforcing the concept of onchocerciasis-associated epilepsy (OAE). The aim of this paper is to provide an update on the new knowledge about OAE and to propose recommendations to the World Health Organization how to address this public health problem. MAIN TEXT: During the 2nd International Workshop on OAE held on 19-21 September, 2023, in Antwerp, Belgium, participants recognised OAE as a substantial yet neglected public health problem, particularly in areas of sub-Saharan Africa where onchocerciasis remains hyperendemic. Evidence from prospective population-based studies suggest that strengthening onchocerciasis elimination efforts leads to a significant reduction of OAE incidence. There is a need to validate an OAE case definition to estimate the burden of disease and identify onchocerciasis-endemic areas requiring intensification of onchocerciasis elimination programmes and integration of epilepsy care. It is expected that raising awareness about OAE will boost the population uptake of ivermectin. The implementation of a community-based epilepsy treatment programme offering free anti-seizure medications (ASMs) has shown high effectiveness in reducing the frequency of seizures and improving the overall quality of life of people with epilepsy. CONCLUSIONS: To reduce OAE burden, enhanced collaboration between onchocerciasis and mental health programmes at community, national, and international levels is required. Urgent efforts are needed to ensure the uninterrupted provision of free ASMs in onchocerciasis-endemic areas. Furthermore, OAE should be included in the quantification of the onchocerciasis disease burden.

Loa loa and Mansonella perstans microfilaremia in the department of Lékoumou, Republic of Congo.

BACKGROUND: Loiasis is endemic in the northern and western part of the Republic of Congo. Between 2004 and 2010, surveys were conducted, using the RAPLOA method, in all departments of the Republic of Congo to assess the distribution of loiasis. Prior to 2004, only two parasitological surveys on loiasis had been conducted in Congo and mainly in the Department of Lékoumou, in the southwestern of the country. In 2019, we conducted a parasitological survey in this same department, more than 30 years after the first surveys. METHODS: The study was conducted in 21 villages. Loa loa and Mansonella perstans microfilaremia levels were quantified using 50 µl calibrated blood smears. RESULTS: A total of 2444 individuals were examined. The median age of the screened individuals was 43 (interquartile range: 30-57, range: 18-91) years old. The overall prevalences of L. loa and M. perstans microfilaremia were 20.0% [95% confidence intervals (CI) 18.0-21.6%] and 1.0% (95% CI 0.6-1.4%) respectively. The proportion of individuals with a microfilarial density of L. loa > 8000 mf/ml and > 30,000 mf/ml were 5.1% (95% CI 4.3-6.1%) and 1.1% (95% CI 0.8-1.7%), respectively. The overall community microfilarial load was 3.4 mf/ml. CONCLUSIONS: Prevalences and intensities of L. loa infection remained generally stable between the late 1980s and 2019 in the Lékoumou Department. In contrast, parasitological indicators for M. perstans have declined sharply in the intervening years for an unknown reason.

Association between blood Loa loa microfilarial density and proteinuria levels in a rural area of the Republic of Congo (the MorLo project): a population-based cross-sectional study.

BACKGROUND: Case reports have hypothesised that proteinuria, sometimes with glomerulopathy or nephrotic syndromes, might be associated with loiasis. To our knowledge, no study has been done to assess this association. We aimed to investigate the association between Loa loa microfilariae burden and proteinuria. METHODS: We did a cross-sectional study between May 16, 2022, and June 11, 2022, to assess the relationship between Loa loa microfilaraemia densities and proteinuria in a rural area of the Republic of Congo. We included all consenting adults living in the target area at study commencement who had L loa microfilarial densities greater than 500 microfilariae per mL during previous screening for a clinical trial in 2019. This study is part of the MorLo project, and used the project's study population of individuals aged 18 years or older who were living near Sibiti. For each microfilaraemic individual, two individuals without L loa microfilarial densities matched on age, sex, and place of residence were included. The association between proteinuria (assessed by dipstick) and L loa microfilarial densities, age, and sex was assessed using an unconstrained ordinal regression model since the parallel-lines assumption was violated for microfilarial densities. FINDINGS: 991 participants were included, of whom 342 (35%) were L loa microfilaraemic. The prevalence of microfilaraemia was 38% (122 of 325) among individuals with trace proteinuria (<300 mg/24 h), 51% (45 of 89) among individuals with light proteinuria (300 mg to 1 g/24 h), and 71% (15 of 21) among individuals with high proteinuria (>1 g/24 h). Individuals with high proteinuria had significantly higher L loa microfilarial densities (p<0·0001): mean microfilariae per mL were 1595 (SD 4960) among individuals with no proteinuria, 2691 (7982) for those with trace proteinuria, 3833 (9878) for those with light proteinuria, and 13 541 (20 118) for those with high proteinuria. Individuals with 5000-14 999 microfilariae per mL and individuals with 15 000 microfilariae per mL or greater were, respectively, 5·39 and 20·49 times more likely to have a high proteinuria than individuals with no microfilaraemia. INTERPRETATION: The risk of proteinuria increases with L loa microfilaraemia. Further studies are needed to identify renal disorders (eg, tubulopathies, glomerulopathies, or nephrotic syndromes) responsible for loiasis-related proteinuria. FUNDING: European Research Council, MorLo project. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.

[Reliability evaluation in rural Congo of the calibrated blood smear technique to assess Loa loa microfilaremia level]. / Évaluation en milieu rural au Congo de la fiabilité de la méthode de la goutte épaisse calibrée pour évaluer le niveau de la microfilarémie à Loa loa.

Background-Rationale: The diagnosis of Loa loa microfilaremia consists in the observation, using a microscope, of microfilariae in a sample of peripheral blood spread on a slide and subsequently stained (the "blood smear technique"). The accurate quantification of Loa loa microfilaremia is important because the choice of the first intention treatment depends on the patient's microfilaremia: severe adverse events can occur in individuals with high microfilarial densities when treated with ivermectin or diethylcarbamazine, the latter drug being the only one which can definitively cure the infection. However, despite the widespread usage of this technique and its role in guiding clinical management of the patient, estimates of its reliability remain scarce. Materials and methods: We evaluated the reliability (reproducibility and repeatability) of blood smear technique using several sets of 10 L. loo-positive slides, randomly selected, and considered the results with regard to regulatory requirements. The slides had been prepared as part of a clinical trial conducted in Sibiti, Republic of Congo, a region where loiasis is endemic. Results: The estimated and acceptable coefficients of repeatability (NB: the lower, the better) were 13.6% and 16.0%, respectively. The estimated and acceptable coefficients of intermediate reliability (reproducibility) were 15.1% and 22.5%, respectively. The poorest coefficient of intermediate reliability was 19.5% when the tested parameter was related to the technician who performed the readings (10.7% when the reading day was changed). The inter-technician coefficient of variation assessed using 1876 L. loo-positive slides was 13.2%. The coefficient of inter-technician variation considered acceptable was estimated at 18.6%. Discussion-Conclusion. All estimated coefficients of variability were lower than the calculated acceptable coefficients suggesting reliability of the technique, although the lack of laboratory references precludes any conclusion on the quality of this diagnosis. It is imperative to implement a quality system and standardization of procedures for the diagnosis of L. loo microfilaremia, both in endemic countries and in the rest of the world, where the demand for diagnosis has been increasing for years.

Association between altered cognition and Loa loa microfilaremia: First evidence from a cross-sectional study in a rural area of the Republic of Congo.

BACKGROUND: Individuals with high Loa loa microfilarial densities are at risk of developing severe encephalopathy after administration of antiparasitic drugs. Apart from this finding, loiasis is considered benign with no effect on brain function. However, recent epidemiological data suggest an increased mortality and morbidity in L. loa infected individuals, underscoring the importance of studies on the possible neurological morbidity associated with loiasis. METHODOLOGY: Using MoCA tests and neurological ultrasounds, we conducted a cross-sectional study to assess cognitive alteration in a population living in a rural area endemic for loiasis in the Republic of Congo. Fifty individuals with high microfilarial densities (MFD) were matched on sex, age and residency with 50 individuals with low MFD and 50 amicrofilaremic subjects. Analyses focused on individuals with MoCA scores indicating an altered cognition (i.e. < 23/30) and on the total MoCA score according to Loa loa MFD, sociodemographic characteristics and neurological ultrasound results. PRINCIPAL FINDINGS: MoCA scores were very low in the studied population (mean of 15.6/30). Individuals with more than 15,000 microfilariae per milliliter of blood (mean predicted score:14.0/30) are more than twenty times more likely to have an altered cognition, compared to individuals with no microfilaremia (mean predicted score: 16.3/30). Years of schooling were strongly associated with better MoCA results. Extracranial and intracranial atheroma were not associated with L. loa MFD. CONCLUSION/SIGNIFICANCE: Loaisis microfilaremia is probably involved in cognitive impairment, especially when the MFD are high. These results highlight the urgent need to better understand loaisis-induced morbidity. Further studies investigating neurological morbidity of loiasis are needed.

Excess Mortality Associated With Loiasis: Confirmation by a New Retrospective Cohort Study Conducted in the Republic of Congo.

Background: Loiasis (Loa loa filariasis) is considered a benign disease and is currently not included in the World Health Organization's (WHO's) list of Neglected Tropical Diseases, despite mounting evidence suggesting significant disease burden in endemic areas. We conducted a retrospective cohort study to assess the mortality associated with L. loa microfilaremia in the Southwestern Republic of Congo. Methods: The cohort included 3329 individuals from 53 villages screened for loiasis in 2004. We compared mortality rates in 2021 for individuals initially diagnosed as with or without L. loa microfilariae 17 years earlier. Data were analyzed at the community level to calculate crude mortality rates. Survival models were used to estimate the effect of L. loa microfilaremia on mortality in the population. Results: At baseline, prevalence of microfilaremia was 16.2%. During 17.62 years of cohort follow-up, 751 deaths were recorded, representing a crude mortality rate of 15.36 (95% CI, 14.28-16.50) per 1000 person-years. Median survival time was 58.5 (95% CI, 49.7-67.3) years and 39.2 (95% CI, 32.6-45.8) years for amicrofilaremic and microfilaremic indiviudals, respectively. Conclusions: A significant reduction in life expectancy was associated with L. loa microfilaremia, confirming previous observations from Cameroon. This adds to the evidence that loiasis is not a benign disease and deserves to be included in the WHO's list of Neglected Tropical Diseases.

Temporal variability of Loa loa microfilaraemia.

BACKGROUND: The diurnal periodicity of Loa loa microfilaraemia is well known but few studies have documented the short- and long-term stability of microfilarial density. It seems stable over time at the community level, but significant variations have been observed at the individual level. METHODS: We assessed the temporal variability of L. loa microfilaraemia at 5-day, 1-month and 16-month intervals and analyzed the influence of sex, age, level of microfilaraemia, temperatures and time of sampling on this variability. RESULTS: At the community level, L. loa microfilaraemia is very stable over time at 5-day, 1-month and 16-month intervals (Pearson correlation coefficients of 0.92, 0.91 and 0.78, respectively, all three with P < 0.001). However, some individuals had significant variations of up to ± 50% of their initial microfilaraemia at 5-day (33.0%), 1-month (36.5%) and 16-month (62.6%) intervals, even in individuals with an initial microfilaraemia density > 20,000 mf/ml (7.7, 23.1 and 41.4%, respectively, for 5 days, 1 month and 16 months). We do not highlight any external factors that have a major impact on this variability. CONCLUSION: Although at the community level, microfilaria density is very stable, we highlight some individuals with large variations in both the short and long term, which may have an important impact on onchocerciasis control campaigns and longitudinal studies evaluating the impact of an intervention on L. loa microfilaraemia.

Evaluating post-treatment Loa loa microfilarial densities to classify serious adverse events caused by ivermectin: a retrospective analysis.

BACKGROUND: The elimination of onchocerciasis requires increasing ivermectin treatment coverage in communities hypoendemic for onchocerciasis. In areas where loiasis is co-endemic, this approach is complicated by the risk of serious adverse events following treatment with ivermectin in individuals with a high Loa loa microfilarial density (MFD). We aimed to evaluate the extent to which the pre-treatment MFD can be inferred from post-treatment MFDs. METHODS: For this retrospective analysis, we used data from seven clinical or community trials (six were used for the main analysis and one for the secondary analysis) conducted in Cameroon, in which MFDs were measured both before and after (within 14 days) receiving a single dose of ivermectin (150-200 µg/kg bodyweight). The primary objective was to establish the receiver operating characteristic curves and the corresponding area under the curve statistics of MFD measured after treatment to classify pre-treatment MFD (MFDD0) according to common risk thresholds of serious adverse events. We assessed the performance of post-treatment MFD to accurately classify MFDD0 according to commonly used thresholds using bootstrap procedures. FINDINGS: 281 individuals with MFD measurements available before and 3-10 days after ivermectin treatment were enrolled. Our results show that an MFD of more than 3500 L loa microfilariae per mL of blood (mf per mL) 3 or 4 days after treatment indicates a 68·6% chance (positive predictive value) of an MFDD0 of more than 20 000 mf per mL. An MFD of more than 3500 mf per mL at day 5-10 corresponds to a 72·2% chance of having an MFDD0 of more than 20 000 mf per mL. Conversely, an MFD of less than 2500 microfilariae per mL at day 3-4 or day 5-10 corresponds to a probability of 92·3% or 92·8% (negative predictive value) of having MFDD0 of less than 20 000 mf per mL. An MFD less than 1500 mf per mL on days 3-4 after treatment was associated with a 78·3% probability of having an MFDD0 less than 8000 mf per mL; this probability increased to 89·6% on days 5-10 after treatment. INTERPRETATION: The MFD threshold of 1000 mf per mL within 1 month of treatment, which is commonly used to attribute the occurrence of a serious adverse event to ivermectin, should be revised. In this study, we present tables that can help to assess this attributability as part of mass or individual treatments. FUNDING: None.

Factors associated with the periodicity of Loa loa microfilaremia in the Republic of the Congo.

BACKGROUND: Loa loa microfilariae circulate in the peripheral blood of human hosts following a diurnal periodicity, with maximal microfilaremia levels generally observed between 10:00 am and 3:00 pm. Few studies have assessed factors potentially associated with this periodicity. METHODS: Microfilaremia data were collected repeatedly between 9:00 am and 8:00 pm from 13 individuals in the Republic of the Congo. Using local polynomial regression (LOESS), we determined the best models representing the dynamics of microfilaremia over this period. In a second step, using cosinor models, we evaluated the influence of sex, age, and body temperature on the periodicity of L. loa microfilaremia in blood. RESULTS: All subjects reached their maximum microfilaremia between 10:00 am and 4:00 pm. Individual microfilaremia showed different patterns between individuals, and some clearly showed multiple peaks within a day. LOESS provided a good fit to the observed data. Without adjustment, the maximum microfilarial density was reached around 11:00 am. Adjustment revealed three distinct modes of microfilaremia, occurring around 10:00 am, 1:00 pm, and 4:00 pm. Cosinor models also provided good fit to our data. After adjustment on body temperature, the L. loa microfilaremia fluctuation amplitude decreased significantly from 1684.8 to 310.6 microfilariae(mf)/ml and the predicted peak was estimated at 12:02 pm. CONCLUSIONS: We characterized the periodicity of L. loa microfilaremia mathematically with two different approaches: cosinor models and LOESS regression. Both models suggest that body temperature plays a role in the variation in microfilaremia within a day. Further studies are needed to identify individual co-factors affecting microfilaremia.

Factors associated with variation in single-dose albendazole pharmacokinetics: A systematic review and modelling analysis.

BACKGROUND: Albendazole is an orally administered anti-parasitic medication with widespread usage in a variety of both programmatic and clinical contexts. Previous work has shown that the drug's pharmacologically active metabolite, albendazole sulfoxide, is characterised by substantial inter-individual pharmacokinetic variation. This variation might have implications for the efficacy of albendazole treatment, but current understanding of the factors associated with this variation remains incomplete. METHODOLOGY/PRINCIPAL FINDINGS: We carried out a systematic review to identify references containing temporally disaggregated data on the plasma concentration of albendazole and/or (its pharmacologically-active metabolite) albendazole sulfoxide following a single oral dose. These data were then integrated into a mathematical modelling framework to infer albendazole sulfoxide pharmacokinetic parameters and relate them to characteristics of the groups being treated. These characteristics included age, weight, sex, dosage, infection status, and whether patients had received a fatty meal prior to treatment or other drugs alongside albendazole. Our results highlight a number of factors systematically associated with albendazole sulfoxide pharmacokinetic variation including age, existing parasitic infection and receipt of a fatty meal. Age was significantly associated with variation in albendazole sulfoxide systemic availability and peak plasma concentration achieved; as well as the clearance rate (related to the half-life) after adjusting for variation in dosage due to differences in body weight between children and adults. Receipt of a fatty meal prior to treatment was associated with increased albendazole sulfoxide systemic availability (and by extension, peak plasma concentration and total albendazole sulfoxide exposure following the dose). Parasitic infection (particularly echinococcosis) was associated with altered pharmacokinetic parameters, with infected populations displaying distinct characteristics to uninfected ones. CONCLUSIONS/SIGNIFICANCE: These results highlight the extensive inter-individual variation that characterises albendazole sulfoxide pharmacokinetics and provide insight into some of the factors associated with this variation.

Status of Onchocerca volvulus (Spirurida: Onchocercidae) Transmission and Effect of Climatic Variables on the Vector Population Dynamics After Two Decades of Ivermectin-based Preventive Chemotherapy in the Mbam Valley (Centre Region, Cameroon).

Entomological indicators of onchocerciasis transmission and the effect of climatic variables on the vector population dynamics were investigated in two first-line villages after more than two decades of mass drug administration with ivermectin. Female blackflies were collected in two villages (Bayomen and Biatsota) using human landing method for a period of 12 months. Blackflies were dissected and entomological indices were computed. Monthly temperature, precipitation, and humidity were collected and the Spearman correlation rank test was used to assess the relationship between biting rates and climatic variables. The highest biting rates (62,280 bites/human/month in Bayomen and 42,090 bites/human/month in Biatsota) were recorded during the long rainy season (November). The Onchocerca volvulus transmission was greater during the long dry season in both villages, with a peak at the beginning of the long dry season in Biatsota (100 infective larvae/human/month), and at the middle of the long dry season in Bayomen (92 infective larvae/human/month). No correlation was found between biting rates and selected climatic variables in the two villages. This study revealed that onchocerciasis transmission is ongoing in the study area despite almost 25 years of Community-Directed Treatment with Ivermectin. In accordance with WHO recommendations, vector control should be used in combination with mass drug administration to accelerate transmission interruption of onchocerciasis. To be optimal, this vector control should be implemented during the long dry season (November to March) when water volumes are low and transmission potentials are high.

Changes in Onchocerciasis Ov16 IgG4 Rapid Diagnostic Test Results Over One-Month Follow-up: Lessons for Reading Timeframe and Decision-Making.

The SD Bioline® IgG4 rapid diagnostic test (RDT) detects IgG4 antibodies induced by the Onchocerca volvulus-specific antigen Ov16. We evaluated the stability of the RDT results over 1 month, at different time points after completion of each assay, using eluted dried blood spots collected in central Cameroon. Agreement coefficients regarding positivity between 30 minutes and 24 hours, 1, 2, 3, and 4 weeks were, 96.4%, 93.4%, 93.3%, 93.2%, and 93.2%, respectively. Between 30 minutes and 24 hours, 3.6% of the 15,444 tests showed inconsistent results with 81.2% of these tests changing from negative to positive, increasing O. volvulus antibody prevalence from 23.9% to 26.2% (P < 0.0001). This change from negative to positive outcome was confirmed at the subsequent timepoints. Depending on the desired accuracy of prevalence estimates, reading time may have to be redefined more strictly.

Historical overview and geographical distribution of neglected tropical diseases amenable to preventive chemotherapy in the Republic of the Congo: A systematic review.

BACKGROUND: Neglected Tropical Diseases amenable to Preventive Chemotherapy (PC-NTDs) affect the poorest populations around the world, especially in Africa. Scientific information on the distribution and level of endemicity of these diseases in the Republic of the Congo (RoC) is scarce in the published literature. We sought to collect all available epidemiological data on PC-NTDs in the RoC to document the historical and current situation and identify challenges in reaching the elimination of NTDs. METHODS: We searched Medline and Horizon databases for studies published until to July 4th, 2019, on onchocerciasis, lymphatic filariasis, soil-transmitted helminth infections, schistosomiasis, and trachoma in the RoC. Unpublished reports were also reviewed. We included all epidemiological studies containing community data and excluded case reports. Location, prevalence data, and dates of the studies were extracted. PRINCIPAL FINDINGS: We identified 933 records, of which 56 met the inclusion criteria. The articles published before 1960 mainly concerned onchocerciasis and schistosomiasis. Despite a low number over the studied period, since 2005 there has been a steady increase in the number of publications. Most of the studies were cross-sectional and conducted in the general population. Trachoma is endemic in the Sangha and Likouala departments (prevalence of trachomatous inflammation-follicular > 5% in some villages), and further mapping is essential to properly assess the burden of this disease in the country. While the prevalence of soil-transmitted helminths is still high (over 20%) in a large part of Congo, cases of lymphatic filariasis (based on Wuchereria bancrofti antigenaemia and/or microfilaraemia) and onchocerciasis are becoming rare and very focused. To achieve the elimination of PC-NTDs, further intervention is required. CONCLUSIONS: Except for trachoma, whose epidemiological situation should be better evaluated, PC-NTDs are endemic in the RoC, and actions to control them have been taken by health authorities. To eliminate PC-NTDs, which are still present in some locations, new mapping surveys are needed, and increased investment in scientific research should be encouraged in the country.

Safety and Efficacy of Levamisole in Loiasis: A Randomized, Placebo-controlled, Double-blind Clinical Trial.

BACKGROUND: Individuals with high microfilarial densities (MFDs) of Loa loa are at risk of developing serious adverse events (SAEs) after ivermectin treatment. Pretreatment with drugs progressively reducing Loa MFDs below the risk threshold might help prevent these SAEs. We assessed the safety and efficacy of levamisole for this purpose. METHODS: A double-blind, randomized, placebo-controlled, MFD-ascending trial was conducted in the Republic of the Congo. Participants were treated in 3 cohorts defined by pretreatment MFD and levamisole dose (cohort 1: 1.0kg and 1.5mg/kg; cohorts 2 and 3: 2.5mg/kg). Safety outcomes were occurrence of SAE and adverse event frequency during the first week. The efficacy outcomes were MFD reduction from baseline and proportions of individuals with at least 40% and 80% MFD reduction at day 2 (D2), D7, and D30. RESULTS: The 2 lowest doses (1.0mg/kg and 1.5mg/kg) caused no SAEs but were ineffective. Compared with placebo, 2.5mg/kg levamisole caused more mild adverse events (10/85 vs. 3/85, P=.018), a higher median reduction from baseline to D2 (-12.9% vs. +15.5%, P<.001), D7 (-4.9% vs. +18.7%, P<.001), and D30 (-0.5% vs. +13.5%, P=.036) and a higher percentage of participants with >40% MFD reduction at D2 (17.5% vs. 1.2%, P<.001), D7 (11.8% vs. 6.3%, P=.269), and D30 (18.5% vs. 9.6%, P=.107). CONCLUSIONS: A single 2.5mg/kg levamisole dose induces a promising transient reduction in Loa loa MFDs and should encourage testing different regimens.

Adverse reactions with levamisole vary according to its indications and misuse: A systematic pharmacovigilance study.

Levamisole was initially prescribed for the treatment of intestinal worms. Because of immunomodulatory properties, levamisole has been used in inflammatory pathologies and in cancers in association with 5-fluorouracil. Levamisole is misused as a cocaine adulterant. Post-marketing reports have implicated levamisole in the occurrence of adverse drug reactions (ADRs) and its use is now limited in Europe and North America. In contrast, all other parts of the World continue to use single-dose levamisole as an anthelmintic. The aim of this study was to identify ADRs reported after levamisole exposure in VigiBase, the World Health Organisation's pharmacovigilance database, and analyse their frequency compared to other drugs and according to levamisole type of use. METHODS: All levamisole-related ADRs were extracted from VigiBase. Disproportionality analyses were conducted to investigate psychiatric, hepatobiliary, renal, vascular, nervous, blood, skin, cardiac, musculoskeletal and general ADRs associated with levamisole and other drugs exposure. In secondary analyses, we compared the frequency of ADRs between levamisole and mebendazole and between levamisole type of use. RESULTS: Among the 1763 levamisole-related ADRs identified, psychiatric disorders (reporting odds ratio with 95% confidence intervals: 1.4 [1.2-2.6]), hepatobiliary disorders (2.4 [1.9-4.3]), vasculitis (6.5 [4.1-10.6]), encephalopathy (22.5 [17.4-39.9]), neuropathy (4.3 [2.9-7.1]), haematological disorders, mild rashes and musculoskeletal disorders were more frequently reported with levamisole than with other drug. The majority of levamisole-related ADRs occurred when the drug was administrated for a non-anti-infectious indication. CONCLUSION: The great majority of the levamisole-related ADRs concerned its immunomodulatory indication and multiple-dose regimen. Our results suggest that single-dose treatments for anthelmintic action have a good safety profile.

Impact of Semi-Annual Albendazole on Lymphatic Filariasis and Soil-Transmitted Helminth Infection: Parasitological Assessment after 14 Rounds of Community Treatment.

Between October 2012 and October 2015, we conducted a community trial to assess the impact of semi-annual (twice yearly) community treatment with albendazole on lymphatic filariasis in Seke Pembe, a village in the Republic of the Congo. Semi-annual community treatment with albendazole has been continued in the community since October 2015. We conducted an additional parasitological assessment survey in October 2019, 6 months after the 14th round of semi-annual treatment. Between October 2012 and October 2015, Wuchereria bancrofti antigenemia and microfilaremia rates in the community had decreased from 17.3% to 4.7% and from 5.3% to 0.3%, respectively. In October 2019, the antigenemia rate had decreased further to 2.8% (19 of 687). No microfilariae were found in night blood smears from persons with circulating filarial antigenemia (0 of 16), suggesting that W. bancrofti transmission has been interrupted in Seke Pembe. Semi-annual albendazole treatments also reduced significantly infection rates with soil-transmitted helminths.