Microfilarial Density Research Articles

Variability of Loa loa microfilarial counts in successive blood smears and its potential implication in drug-related serious adverse events

BackgroundThe standard method to diagnose Loa loa infection and quantify microfilarial density (MFD) is the microscopic examination of calibrated thick blood smears (TBSs). In 1950, it was noticed that successive L. loa MFD samples from a single capillary puncture could exhibit up to 20% variation. Although loiasis treatment allocation is based on MFD to prevent serious adverse events (SAEs), data on this variability are scarce. There are also no guidelines supporting the collection and analysis of one or two TBSs.MethodsWe assessed the variability of two successive L. loa MFD samples (MFD1 and MFD2), collected from 255 patients. We analyzed the influence of sex, age, weight, heart rate, arterial pressure, body temperature, and sampling time on MFD variability, as well the impact of MFD variability on MFD thresholds relevant to loiasis treatment protocols.ResultsThe MFD2 was found to have increased in 63% (1145/1826) of TBS pairs and to have decreased in 37% (681/1826) of TBS pairs. The MFD2 were on average 28% higher than the MFD1. These variations drove a total of 333 (17.4%) changes in MFD classes according to loiasis treatment protocol, including 210 (11.3%) class increases. TBSs generated from blood samples from subjects with lower MFD (1–1000 mf/ml) or lower mean arterial pressure (MAP; 55–80 mmHg), or from blood samples collected at an earlier hour time-point (10:00–10:59 a.m.) were more subject to MFD2 variability in a multivariate analysis. The MFD relative change was not constant over time for a given person.ConclusionsWe observed a trend towards an increase in MFD2 with an important variability between samples that may impact loiasis treatment allocation. We suggest that systematically sampling at least two successive TBSs might allow better MFD assessments to prevent post-treatment SAEs. Further studies are needed to verify this variability in larger samples as well as confirm the potential explanatory variables identified.Graphical

Analysis of diagnostic test outcomes in a large loiasis cohort from an endemic region: Serological tests are often false negative in hyper-microfilaremic infections.

The parasitic disease loiasis is associated with significant morbidity and mortality. Individuals with hyper-microfilaremia (greater than 20,000 microfilariae per mL of blood) may suffer from serious treatment-related or spontaneous adverse events. Diagnosing loiasis remains complex and primarily relies on direct parasite detection. In this study, we analyzed the performance of various diagnostic tests and the influence of parasitological and clinical factors on test outcomes in samples from individuals living in an endemic region. Data and samples were collected from rural Gabon. Loiasis was defined as either detectable microfilaremia, or a positive history of eyeworm as assessed by the RAPLOA questionnaire. Diagnostic testing included a quantitative PCR (qPCR) for detection of Loa loa DNA in blood samples, an in-house crude L. loa antigen IgG ELISA, and a rapid test for antibodies against the Ll-SXP-1 antigen (RDT). Sensitivity and specificity were determined for each test and factors potentially influencing outcomes were evaluated in an exploratory analysis. ELISA, RDT and qPCR results were available for 99.8%, 78.5%, and 100% of the 1,232 participants, respectively. The ELISA and RDT had only modest diagnostic accuracy. qPCR was specific for L. loa microfilaremia and Cycle threshold values correlated with microfilarial density. Anti-L. loa IgG levels were highest in occult loiasis, and antibody levels correlated inversely with L. loa microfilarial density as did RDT line intensities. Only 84.6% and 16.7% of hyper-microfilaremic individuals tested positive by ELISA (11/13) and RDT (2/12), respectively. None of the tests demonstrated high sensitivity and specificity for loiasis. Indirect diagnostic assays were characterized by low specificity. Additionally, hyper-microfilaremic individuals often tested negative by RDT and ELISA, indicating that these tests are not suitable for individual case management in endemic populations.

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).

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. 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). 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. A potential link between high L. loa microfilaremia and cardiovascular health deterioration is suggested. Further studies are required to confirm and explore this association.

Surveillance and Selective Treatment of Brugia malayi Filariasis Eleven Years after Stopping Mass Drug Administration in Belitung District, Indonesia.

Brugia malayi is the major cause of lymphatic filariasis (LF) in Indonesia. Zoophilic B. malayi was endemic in Belitung district, and mass drug administration (MDA) with diethylcarbamazine (DEC) and albendazole ceased after five annual rounds in 2010. The district passed three transmission assessment surveys (TAS) between 2011 and 2016. As part of the post-TAS3 surveillance of the national LF elimination program, we collected night blood samples for microfilaria (Mf) detection from 1,911 subjects more than 5 years of age in seven villages. A B. malayi Mf prevalence ranging from 1.7% to 5.9% was detected in five villages. Only 2 (5%) of the total 40 Mf-positive subjects were adolescents aged 18 and 19 years old, and 38 (95%) Mf-positive subjects were 21 years and older. Microfilarial densities in infected individuals were mostly low, with 60% of the subjects having Mf densities between 16 and 160 Mf/mL. Triple-drug treatment with ivermectin, DEC, and albendazole (IDA) was given to 36 eligible Mf-positive subjects. Adverse events were mostly mild, and treatment was well tolerated. One year later, 35 of the treated Mf-positive subjects were reexamined, and 33 (94%) had cleared all Mf, while the anti-Bm14 antibody prevalence remained almost unchanged. Results indicate that in B. malayi-endemic areas, post-TAS3 surveillance for Mf in the community may be needed to detect a potential parasite reservoir in adults. Selective treatment with IDA is highly effective in clearing B. malayi Mf and should be used to increase the prospects for LF elimination if MDA is reintroduced.

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

BackgroundLoiasis 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.MethodsThe study was conducted in 21 villages. Loa loa and Mansonella perstans microfilaremia levels were quantified using 50 µl calibrated blood smears.ResultsA 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.ConclusionsPrevalences 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.Graphical

Longitudinal study of cross-reactive antigenemia in individuals with high Loa loa microfilarial density reveals promising biomarkers for distinguishing lymphatic filariasis from loiasis.

Circulating Loa loa antigens are often detected in individuals with heavy L. loa infections by diagnostic tests for lymphatic filariasis (LF) caused by Wuchereria bancrofti. This is a major challenge to LF mapping and elimination efforts in loiasis co-endemic areas. However, it also provides an opportunity to identify antigen biomarkers for loiasis. To determine which L. loa antigens might be promising biomarkers for distinguishing true LF from loiasis, we screened for L. loa antigens in a group of individuals with heavy L. loa infections living in the Okola Health District of Cameroon. In this longitudinal study, participants were tested for cross-reactive antigenemia by filariasis test strip (FTS), ELISA, and western blot, and were monitored for FTS status at 6, 9, 12, and 15 months post-enrollment. We then identified specific circulating L. loa antigens by liquid chromatography-tandem mass spectrometry (LC-MS/MS) from baseline and 15-month plasma samples. Among 73 FTS-positive (FTS+) and 13 FTS-negative (FTS-) participants with high L. loa microfilarial loads, 83% maintained their FTS status over the course of the study, while 17% experienced at least one FTS conversion event (from FTS+ to FTS- or vice versa). Cross-reactive antigens were detected in both FTS+ and FTS- sera by western blot, and there was poor agreement in antigen detection by FTS, western blot, and ELISA methods. One protein family, a group of Nas-14 metalloproteases, was detected by LC MS/MS in >80% of tested samples, including FTS- samples. These data identify Nas-14 as a promising loiasis biomarker potentially capable of distinguishing loiasis from lymphatic filariasis.

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

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. 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. 991 participants were included, of whom 342 (35%) were L loa microfilaraemic. Among individuals who were microfilaraemic, the prevalence of trace proteinuria (<300 mg/24 h) was 38% (122 of 325), light proteinuria (300 mg to 1 g/24 h) was 51% (45 of 89), and high proteinuria (>1 g/24 h) was 71% (15 of 21). Among individuals who were amicrofilaraemic, the prevalence of trace proteinuria was 63% (203 of 325), light proteinuria was 49% (44 of 89), and high proteinuria was 29% (6 of 21). 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. 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. European Research Council, MorLo project. For the French translation of the abstract see Supplementary Materials section.

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

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. 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. 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. 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.

Impact of short-term discontinuation of ivermectin-based chemoprevention on onchocerciasis transmission in endemic settings with long history of mass drug administration.

The control of onchocerciasis currently relies on annual distribution of single dose ivermectin. Because ivermectin has minimal effects on the adult parasite, mass drug administration (MDA) campaigns against onchocerciasis require at least 15 years of annual uninterrupted ivermectin distribution. Mathematical models have predicted that short-term disruption of MDA (as was seen during COVID-19) could impacted the microfilaridermia prevalence depending on the pre-control endemicity and the histories of treatment, requiring corrective measures (such as biannual MDA) to mitigate the effect on onchocerciasis elimination. Field evidence supporting this prediction, however, has yet to be gathered. This study aimed to assess the impact of ~2 years disruption of MDA on onchocerciasis transmission indicators. A cross-sectional survey was carried out in 2021 in seven villages of Bafia and Ndikinimeki, two health districts located in the Centre Region, Cameroon, where MDA has been ongoing for two decades, but interrupted in 2020 as a response to the COVID-19 pandemic. Volunteers aged 5 years and above were enrolled for clinical and parasitological examinations for onchocerciasis. Data were compared with pre-COVID-19 prevalence and intensity of infection from the same communities to measure changes over time. A total of 504 volunteers (50.3% males), aged 5-99 years (Median: 38; IQR: 15-54) was enrolled in the two health districts. The overall prevalence of microfilaridermia in 2021 was similar in Ndikinimeki health district (12.4%; 95% CI: 9.7-15.6) and Bafia health district (15.1%; 95% CI: 11.1-19.8) (p-value = 0.16). Microfilaridermia prevalences were either similar between 2018 and 2021 in the communities of Ndikinimeki health district (19.3% vs 12.8% (p = 0.057) for Kiboum 1; and 23.7% vs 21.4% (p = 0.814) for Kiboum 2), or higher in 2019 compared to 2021 in the communities of Bafia health district (33.3% vs 20.0% (p = 0.035) for Biatsota). The mean microfilarial densities in these communities dropped from 5.89 (95% CI: 4.77-7.28) mf/ss to 2.4 (95% CI: 1.68-3.45) mf/ss (p-value < 0.0001), and from 4.81 (95% CI: 2.77-8.31) mf/ss to 4.13 (95% CI: 2.49-6.86) mf/ss (p-value < 0.02) in Bafia and Ndikinimeki health districts, respectively. Community Microfilarial Load (CMFL) dropped from 1.08-1.33 mf/ss in 2019 to 0.052-0.288 mf/ss in 2021 in Bafia health district while remaining stable in the Ndikinimeki health district. The continued decline in prevalence and CMFL observed ~2 years after MDA disruption is consistent with mathematical predictions (ONCHOSIM) and shows that additional efforts and resources are not needed to mitigate the effects of short-term MDA disruption in highly endemic settings prior to intervention with long treatment histories.

Reliability evaluation in rural Congo of the calibrated blood smear technique to assess Loa loa microfilaremia level

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. 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. 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.

Temporal variability of Loa loa microfilaraemia

BackgroundThe 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.MethodsWe 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.ResultsAt 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.ConclusionAlthough 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.Graphical

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

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. 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. 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. 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. None.

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

BackgroundLoa 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.MethodsMicrofilaremia 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.ResultsAll 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.ConclusionsWe 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.Graphical

Ivermectin treatment response in two rural villages with a high prevalence of onchocerciasis and epilepsy, Mahenge Tanzania.

Despite 20 years of ivermectin mass distribution in the Mahenge area, Tanzania, the prevalence of onchocerciasis and epilepsy has remained high in rural villages. We investigated the efficacy of ivermectin in reducing Onchocerca volvulus microfilariae and predictors for parasitic load following ivermectin treatment in persons with (PWE) and without epilepsy (PWOE). Between April and September 2019, 50 PWE and 160 randomly selected PWOE from Msogezi and Mdindo villages participated in a follow-up study. Skin snips were obtained pre (baseline) and three months post-ivermectin treatment. The overall prevalence of O. volvulus positive skin snips at baseline was 49% (103/210), with no significant difference between PWE (58.0%) and PWOE (46.3%); p=0.197. The overall mean microfilarial density was significantly higher at baseline 1.45(95%CI:0.98-2.04)) than three-month post-ivermectin treatment (0.23(95%CI:0.11-0.37), p<0.001. Three months after ivermectin, the microfilarial density had decreased by ≥80% in 54 (81.8%, 95%CI: 72.3-91.4) of the 66 individuals with positive skin snips at baseline. High microfilarial density at baseline was the only significant predictor associated with higher microfilarial density in the post-ivermectin skin snips. Our study reports a decrease in microfilarial density following ivermectin treatment in most individuals. Optimizing ivermectin coverage will address the ongoing onchocerciasis transmission in Mahenge.

Association Between Blood &lt;i&gt;Loa loa&lt;/i&gt; Microfilarial Density and Proteinuria Levels: A Population Based Cross-Sectional Study in a Rural Area of the Republic of Congo

Association Between Blood &lt;i&gt;Loa loa&lt;/i&gt; Microfilarial Density and Proteinuria Levels: A Population Based Cross-Sectional Study in a Rural Area of the Republic of Congo

Loiasis is endemic in the Ndikinimeki Health District (Centre Region, Cameroon) but does not represent a hindrance to onchocerciasis elimination

Community-Directed Treatment with Ivermectin (CDTI) is the strategy of choice to fight onchocerciasis in Africa. In areas where loiasis is endemic, onchocerciasis control and/or elimination is hindered by severe adverse events (SAEs) occurring after ivermectin mass treatments. This study aimed at (i) investigating the impact of two decades of CDTI on L. loa clinical and parasitological indicators in the Ndikinimeki Health District, and (ii) assessing the risk of SAEs after this long-term preventive chemotherapy. A cluster-based cross-sectional survey was conducted in the six Health Areas of the Ndikinimeki Health District. All volunteers underwent day-time calibrated thick blood smears to search for L. loa microfilariae, as well as an interview to assess the history of migration of eye worm and Calabar swelling. The overall prevalence of L. loa microfilaraemia was 2.2 % (95% CI: 1.3–3.7%), and the proportions of individuals who had already experienced eye worm and/or Calabar swelling were 1.0% and 0.5%, respectively. The mean microfilarial density was 63.55 (SD: 559.17; maximum: 9220.0) mf/mL. These findings indicate that (i) the long-term ivermectin-based preventive chemotherapy against onchocerciasis significantly reduced L. loa clinical and parasitological indicators, and (ii) the risk of developing neurologic and potentially fatal SAE after ivermectin mass treatment is zero in the Ndikinimeki Health District.

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

BackgroundIndividuals 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.MethodsA 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.ResultsThe 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).ConclusionsA single 2.5mg/kg levamisole dose induces a promising transient reduction in Loa loa MFDs and should encourage testing different regimens.

Parasitological and epidemiological studies of Wuchereria bancrofti in Imobi, Ijebu East, Local Government Area of Ogun State, South Western Nigeria

BackgroundLymphatic filariasis is a mosquito-borne parasitic disease caused by Wuchereria bancrofti. It is a neglected tropical disease that constitutes a public health challenge in rural endemic communities in Nigeria. This is a debilitating disease of global concern, because of its effect on per capital income and its stigmatization on affected individuals. The Program for Elimination for Lymphatic filariasis has set a goal towards possible elimination.ResultsCommunities in Imobi, in Ijedu East Local Government Area in Ogun State, have been undergoing Mass Drug Administration (MDA). However, there is need for a baseline data to assess, monitor and evaluate the progress of MDA in these communities towards eventual elimination. Systematic random sampling and cluster survey were used to gather 246 participants from six communities in Imobi to a central point at the Local Government Health Centre. Parasitological diagnosis was done using microscopy, while structured questionnaires, which probed into respondents Knowledge, Attitude and Practices, were administered. An overall prevalence of 50 (20.3%) was observed with 17 (21.5%) males being more infected than 24 (19.8%) females. Prevalence of infection was significantly higher in younger age groups 4 (28.6%) than in older age groups 20 (14.6%) at p < 0.05. Overall microfilarial density of 25.7 mf/ml was obtained among infected population. Microfilariae prevalence was not observed in people that had received treatment with both albendazole and ivermectin. Higher prevalence of infection was observed in people who did not made use of Long Lasting Insecticidal Nets 45 (21.1%), than in people who did 5 (15.2%). However, it was not statistically significant (p > 0.05). Most of the respondents had little or no knowledge of the disease, its cause, transmission, prevention and treatment. The prevalence level is also higher than 1% for which MDA is required.ConclusionsIt is recommended that MDA be intensified in the study area, together with vector control and awareness campaign on the disease.

ACUTE ENCEPHALOPATHY AFTER SELF MEDICATION WITH IVERMECTIN IN A PATIENT WITH COVID-19

TOPIC: Critical Care TYPE: Global Case Reports INTRODUCTION: Ivermectin is an FDA approved anti parasitic drug widely used and generally well tolerated. In vitro data suggests ivermectin may inhibit replication of SARS-CoV-2. This has generated interest for a potential role in the prevention and treatment of COVID19. We report a case of a patient who developed severe encephalopathy after an accidental overdose with ivermectin CASE PRESENTATION: A 70-year-old female patient was brought to the ED with altered mental status. The patient initially complained of nonproductive cough for five days. After searching online for possible treatments for COVID19, her husband bought a veterinarian preparation of ivermectin for horses at the local store. After discussing with her husband, the patient took two ampules of this medication. Each ampule contained 113.75 mg of ivermectin. About five hours later, the husband noticed that she was difficult to arouse. On presentation, vital signs were normal and she was afebrile. On exam she was arousable to voice and able to follow simple commands but nonverbal. Initial lab values included a normal CBC and BMP. Aminotransferases were mildly elevated. SARS-Cov-2 RNA nasal pharyngeal swab was positive. Urine drug screen was negative. CXR and CT of the brain were normal. The patient was admitted to the ICU for close neurologic assessments. Fortunately, the patient improved slowly and was discharged home 48 hours later with no complications DISCUSSION: Ivermectin is a known anti parasitic drug, that has not been approved to treat viruses. That being said, ivermectin, in vitro, inhibits positive, single stranded RNA viruses. Ivermectin has also shown to inhibit replication of SARS-CoV-2 in vitro. Several trials have been conducted to assess the efficacy of this drug for the prevention and treatment of COVID19. Results have been inconclusive. FDA has not approved ivermectin for use in treating or preventing COVID19. Although mostly considered a safe drug, overdose with ivermectin can cause nausea, vomiting, diarrhea, dizziness, ataxia and rarely seizures, coma and even death. Cases of fatal encephalopathy have been described during ivermectin treatment campaigns against onchocerciasis in Africa in subjects with a high Loa loa microfilarial density. Dosing for treatment of parasitic infections are in the range 150- 400 mcg/kg/day. Our patient took ten times the recommended dose. Ivermectin is also used as an antiparasitic agent for farm animals. It can be purchased without a prescription for veterinarian use. On April 10, 2020 the FDA published an advisory warning the public not to take Ivermectin intended for animals. CONCLUSIONS: Ivermectin is an anti parasitic drug widely used and generally well tolerated. The efficacy of this drug for the prevention and treatment of COVID19 remains inconclusive and its use is not recommended. Accidental overdoses can present with severe encephalopathy REFERENCE #1: Caly L, Druce J, Catton M, The FDA-approved Drug Ivermectin inhibits the replication of SARS-CoV-2 in vitro. Antiviral Res Vol178, June 2020, 104787 REFERENCE #2: https://www.covid19treatmentguidelines.nih.gov/antiviral-therapy/ivermectin/ REFERENCE #3: Chandler R. E. Serious Neurological Adverse Events after Ivermectin—Do They Occur beyond theIndication of Onchocerciasis?. Am. J. Trop. Med. Hyg., 98(2), 2018, pp. 382–388 DISCLOSURES: no disclosure on file for Abdulilah Arafeh;No relevant relationships by Bryan Emerick, source=Web Response No relevant relationships by Juan Morales, source=Web Response

Unusual Localization of Blood-Borne Loa loa Microfilariae in the Skin Depends on Microfilarial Density in the Blood: Implications for Onchocerciasis Diagnosis in Coendemic Areas.

BackgroundThe diagnostic gold standard for onchocerciasis relies on identification and enumeration of (skin-dwelling) Onchocerca volvulus microfilariae (mf) using the skin snip technique (SST). In a recent study, blood-borne Loa loa mf were found by SST in individuals heavily infected with L. loa, and microscopically misidentified as O. volvulus due to their superficially similar morphology. This study investigates the relationship between L. loa microfilarial density (Loa MFD) and the probability of testing SST positive.MethodsA total of 1053 participants from the (onchocerciasis and loiasis coendemic) East Region in Cameroon were tested for (1) Loa MFD in blood samples, (2) O. volvulus presence by SST, and (3) Immunoglobulin (Ig) G4 antibody positivity to Ov16 by rapid diagnostic test (RDT). A Classification and Regression Tree (CART) model was used to perform a supervised classification of SST status and identify a Loa MFD threshold above which it is highly likely to find L. loa mf in skin snips.ResultsOf 1011 Ov16-negative individuals, 28 (2.8%) tested SST positive and 150 (14.8%) were L. loa positive. The range of Loa MFD was 0–85 200 mf/mL. The CART model subdivided the sample into 2 Loa MFD classes with a discrimination threshold of 4080 (95% CI, 2180–12 240) mf/mL. The probability of being SST positive exceeded 27% when Loa MFD was >4080 mf/mL.ConclusionsThe probability of finding L. loa mf by SST increases significantly with Loa MFD. Skin-snip polymerase chain reaction would be useful when monitoring onchocerciasis prevalence by SST in onchocerciasis–loiasis coendemic areas.