Possible pathogenic pathways in the adverse clinical events seen following ivermectin administration to onchocerciasis patients

Ivermectin role in COVID-19 treatment (IRICT): single-center, adaptive, randomized, double-blind, placebo-controlled, clinical trial

BACKGROUND

To investigate the efficacy and safety of ivermectin compared to hydroxychloroquine and placebo in hospitalized moderate to severe COVID-19 patients.

RESEARCH DESIGN AND METHODS

The study was an adaptive, randomized, double-blinded, controlled, single-center trial. The study was a series of 3-arm comparisons between two different investigational therapeutic agents (ivermectin and hydroxychloroquine) and a placebo. There was interim monitoring to allow early stopping for futility, efficacy, or safety.

RESULTS

Ivermectin decreased survival time from 29 to 18.3 days (HR, 9.8, 95%CI, 3.7-26.2), while it did not shorten the recovery time (HR, 1.02, 95%CI, 0.69-1.5). Subgroup analysis showed an association between ivermectin-related mortality and baseline oxygen saturation level. Moreover, stratified groups showed higher risk among patients on high flow O2. Hydroxychloroquine delayed recovery from 10.1 to 12.5 days (HR, 0.62, 95%CI, 0.4-0.95) and non-significantly decreased survival time from 29 to 26.8 days (HR, 1.47, 95%CI, 0.73-2.9). However, 3 months mortality rates were increased with hydroxychloroquine (RR, 2.05, 95%CI, 1.33-3.16). Neither ivermectin nor hydroxychloroquine increased adverse events and demonstrated safety profile compared to placebo.

CONCLUSIONS

The study recommends against using either ivermectin or hydroxychloroquine for treatment of COVID-19 in hospitalized patients with any degree of severity. Clinical trial registration: www.clinicaltrials.gov identifier is: NCT04746365.

Drug Repurposing: A Review of Old and New Antibiotics for the Treatment of Malaria: Identifying Antibiotics with a Fast Onset of Antiplasmodial Action

Malaria is one of the most life-threatening infectious diseases and constitutes a major health problem, especially in Africa. Although artemisinin combination therapies remain efficacious to treat malaria, the emergence of resistant parasites emphasizes the urgent need of new alternative chemotherapies. One strategy is the repurposing of existing drugs. Herein, we reviewed the antimalarial effects of marketed antibiotics, and described in detail the fast-acting antibiotics that showed activity in nanomolar concentrations. Antibiotics have been used for prophylaxis and treatment of malaria for many years and are of particular interest because they might exert a different mode of action than current antimalarials, and can be used simultaneously to treat concomitant bacterial infections.

Tri-Model Therapy: Combining Macrocyclic Lactone, Piperazine Derivative and Herbal Preparation in Treating Humpsore in Cattle

Stephanofilariasis or humpsore is a chronic parasitic dermatitis of cattle. Various treatment regimens were attempted in the past but were found to be partially effective. Here, we claim a successful treatment regime using an FDA-approved macrocyclic lactone, a piperazine derivative, and an herbal preparation. Twenty-four cattle (18 affected and 6 unaffected) were selected and divided into Gr 1: positive control (infected without treatment; n = 6), Gr 2: treatment group (infected with treatment with ivermectin; n = 6), Gr 3: treatment group (infected with treatment with tri-model therapy including ivermectin, diethylcarbamazine citrate, and an herbal ointment, n = 6), and Gr 4: negative control (non-infected animals; n = 6). In Gr 2 and Gr 3, treatment to the ailing animals were given for 30 days. Lesion was significantly reduced in day 15 of post-treatment and completely healed on day 30 of post-treatment in Gr 3. Tri-model therapy recorded significant improvement in the surface area of the sore as compared to ivermectin administration alone. Antioxidants were increased and malondialdehyde (MDA) and cortisol concentrations were decreased significantly (p < 0.05) in Gr 3 than in untreated control group at day 14, 21 and 28. Histopathological changes in infected animals were characterized by parakeratotic hyperkeratosis along with presence of nucleated keratinocytes. There were infiltrations of polymorphonuclear cells specially eosinophils along with a few monomorphonuclear cells. Microfilarial organism was observed beneath the epidermis, which was surrounded by fibrocytes and infiltrated cells. In the tri-model-treated animal after recovery, the skin revived a normal architecture. Therefore, tri-model therapy has the potential to cure humpsore.

Effect of Ivermectin Treatment on the Frequency of Seizures in Persons with Epilepsy Infected with Onchocerca volvulus

A clinical trial performed in the Democratic Republic of Congo (DRC), among persons with epilepsy (PWE) infected with Onchocerca volvulus treated with anti-seizure medication suggested that ivermectin reduces the seizure frequency. We assessed the effect of ivermectin treatment on seizure frequency in PWE with and without anti-seizure medication in three onchocerciasis endemic areas (Maridi, South Sudan; Aketi, DRC; and Mahenge, Tanzania). Pre- and 3–5 months post-ivermectin microfilariae densities in skin snips and seizure frequency were assessed. After ivermectin, the median (IQR) percentage reduction in seizure frequency in the study sites ranged from 73.4% (26.0–90.0) to 100% (50.0–100.0). A negative binomial mixed model showed that ivermectin significantly reduced the seizure frequency, with a larger decrease in PWE with a high baseline seizure frequency. Mediation analysis showed that ivermectin reduced the seizure frequencies indirectly through reduction in microfilariae densities but also that ivermectin may have a direct anti-seizure effect. However, given the short half-life of ivermectin and the fact that ivermectin does not penetrate the healthy brain, such a direct anti-seizure effect is unlikely. A randomized controlled trial assessing the ivermectin effect in people infected with O. volvulus who are also PWE on a stable anti-seizure regimen may be needed to clarify the causal relationship between ivermectin and seizure frequency.

Ivermectin: From theory to clinical application

Approximately 250 million people have been using ivermectin (IVM) annually to combat many parasitic diseases including filariasis, onchocerciasis, strongyloidiasis, scabies and pediculosis. Many clinical studies have proven its efficacy against these diseases and have reported the optimum dose and duration of treatment. Moreover, its antiparasitic range has increased to cover more parasitic infections, but it still requires further exploration, e.g. for trichinosis and myiasis. Furthermore, IVM showed high efficacy in killing vectors of disease-causing parasites such as mosquitoes, sandflies and tsetse flies. The World Health Organization (WHO) has managed many control programmes involving the use of IVM to achieve elimination of onchocerciasis and lymphatic filariasis and to reduce malaria transmission. However, IVM is not exempt from the possibility of resistance and, certainly, its intensive use has led to the emergence of resistance in some parasites. Recent research is investigating the possibility of novel drug delivery systems for IVM that increase its potential to treat a new range of diseases and to overcome the possibility of drug resistance. This review highlights the most common human uses of IVM, with special reference to the new and promising properties of IVM.

New indications for topical ivermectin 1% cream: a case series study

Introduction

Topical ivermectin is an effective treatment for inflammatory papulopustular rosacea in adults. Positive therapeutic effects of ivermectin due to its potential anti-inflammatory properties could be achieved in the other facial dermatoses.

Aim

To assess the efficacy of topical ivermectin 1% cream therapy in mild and moderate perioral dermatitis (PD), seborrheic dermatitis (SD) and acne vulgaris (AV).

Material and methods

The study comprising 20 patients diagnosed with PD (8), SD (8) and AV (4) was conducted between November 2016 and July 2017. Two scales were applied to establish efficacy of the treatment: Investigator Global Assessment score (IGA) and Patient Global Assessment of Treatment (PGA).

Results

All patients responded to the treatment with topical ivermectin very well with a gradual reduction in inflammatory skin lesions. Complete or almost complete clearance (IGA score 0-1) was achieved in 20 cases. Four patients with PD achieved IGA 0-1 after 4 weeks of treatment, 1 patient after 5 weeks, 2 patients after 6 weeks and 1 patient after 12 weeks. In the total group of 8 patients with SD, 4 presented IGA 0 after 4 weeks of therapy, while 4 patients demonstrated IGA 1 after 6 weeks. Patients with AV required 8 and 10 weeks to obtain IGA 1. Nineteen patients of the studied group reported "very good" or "excellent" response to the therapy, only one patient with AV assessed therapy with topical ivermectin as "good". The adverse events were transient and manifested as mild-moderate desquamation, stinging and burning in 2 patients with PD.

Conclusions

Topical ivermectin was well tolerated and beneficial for treatment of mild and moderate PD, SD and AV.

Inflammatory and regulatory CCL and CXCL chemokine and cytokine cellular responses in patients with patent Mansonella perstans filariasis

Mansonella perstans (Mp) filariasis is present in large populations in sub-Saharan Africa, and to what extent patent Mp infection modulates the expression of immunity in patients, notably their cellular cytokine and chemokine response profile, remains not well known. We studied the spontaneous and inducible cellular production of chemokines (C-X-C motif) ligand 9 (CXCL9) [monokine induced by interferon (IFN)-γ (MIG)], CXCL-10 [inducible protein (IP)-10], chemokine (C-C motif) ligand 24 (CCL24) (eotaxin-2), CCL22 [macrophage-derived chemokine (MDC)], CCL13 [monocyte chemotactic protein-4 (MCP-4)], CCL18 [pulmonary and activation-regulated chemokine (PARC)], CCL17 [thymus- and activation-regulated chemokine (TARC)] and interleukin (IL)-27 in mansonelliasis patients (Mp-PAT) and mansonelliasis-free controls (CTRL). Freshly isolated peripheral mononuclear blood cells (PBMC) were stimulated with helminth, protozoan and bacterial antigens and mitogen [phytohaemagglutinin (PHA)]. PBMC from Mp-PAT produced spontaneously (without antigen stimulation) significantly higher levels of eotaxin-2, IL-27, IL-8, MCP-4 and MDC than cells from CTRL, while IFN-γ-IP-10 was lower in Mp-PAT. Helminth antigens activated IL-27 and MCP-4 only in CTRL, while Ascaris antigen, Onchocerca antigen, Schistosoma antigen, Entamoeba antigen, Streptococcus antigen, Mycobacteria antigen and PHA stimulated MIG release in CTRL and Mp-PAT. Notably, Entamoeba antigen and PHA strongly depressed (P < 0·0001) eotaxin-2 (CCL24) production in both study groups. Multiple regression analyses disclosed in Mp-PAT and CTRL dissimilar cellular chemokine and cytokine production levels being higher in Mp-PAT for CCL24, IL-27, IL-8, MCP-4, MDC and PARC (for all P < 0·0001), at baseline (P < 0·0001), in response to Entamoeba histolytica strain HM1 antigen (EhAg) (P < 0·0001), Onchocerca volvulus adult worm-derived antigen (OvAg) (P = 0·005), PHA (P < 0·0001) and purified protein derivative (PPD) (P < 0·0001) stimulation. In Mp-PAT with hookworm co-infection, the cellular chemokine production of CXCL10 (IP-10) was diminished. In summary, the chemokine and cytokine responses in Mp-PAT were in general not depressed, PBMC from Mp-PAT produced spontaneously and selectively inducible inflammatory and regulatory chemokines and cytokines at higher levels than CTRL and such diverse and distinctive reactivity supports that patent M. perstans infection will not polarize innate and adaptive cellular immune responsiveness in patients.

Ivermectin treatment of Loa loa hyper-microfilaraemic baboons (Papio anubis): Assessment of microfilarial load reduction, haematological and biochemical parameters and histopathological changes following treatment

BACKGROUND

Individuals with high intensity of Loa loa are at risk of developing serious adverse events (SAEs) post treatment with ivermectin. These SAEs have remained unclear and a programmatic impediment to the advancement of community directed treatment with ivermectin. The pathogenesis of these SAEs following ivermectin has never been investigated experimentally. The Loa/baboon (Papio anubis) model can be used to investigate the pathogenesis of Loa-associated encephalopathy following ivermectin treatment in humans.

METHODS

12 baboons with microfilarial loads > 8,000mf/mL of blood were randomised into four groups: Group 1 (control group receiving no drug), Group 2 receiving ivermectin (IVM) alone, Group 3 receiving ivermectin plus aspirin (IVM + ASA), and Group 4 receiving ivermectin plus prednisone (IVM + PSE). Blood samples collected before treatment and at Day 5, 7 or 10 post treatment, were analysed for parasitological, hematological and biochemical parameters using standard techniques. Clinical monitoring of animals for side effects took place every 6 hours post treatment until autopsy. At autopsy free fluids and a large number of standard organs were collected, examined and tissues fixed in 10% buffered formalin and processed for standard haematoxylin-eosin staining and specific immunocytochemical staining.

RESULTS

Mf counts dropped significantly (p<0.05) in all animals following ivermectin treatment with reductions as high as (89.9%) recorded; while no significant drop was observed in the control animals. Apart from haemoglobin (Hb) levels which recorded a significant (p = 0.028) drop post treatment, all other haematological and biochemical parameters did not show any significant changes (p>0.05). All animals became withdrawn 48 hours after IVM administration. All treated animals recorded clinical manifestations including rashes, itching, diarrhoea, conjunctival haemorrhages, lymph node enlargement, pinkish ears, swollen face and restlessness; one animal died 5 hours after IVM administration. Macroscopic changes in post-mortem tissues observed comprised haemorrhages in the brain, lungs, heart, which seen in all groups given ivermectin but not in the untreated animals. Microscopically, the major cellular changes seen, which were present in all the ivermectin treated animals included microfilariae in varying degrees of degeneration in small vessels. These were frequently associated with fibrin deposition, endothelial changes including damage to the integrity of the blood vessel and the presence of extravascular erythrocytes (haemorrhages). There was an increased presence of eosinophils and other chronic inflammatory types in certain tissues and organs, often in large numbers and associated with microfilarial destruction. Highly vascularized organs like the brain, heart, lungs and kidneys were observed to have more microfilariae in tissue sections. The number of mf seen in the brain and kidneys of animals administered IVM alone tripled that of control animals. Co-administration of IVM + PSE caused a greater increase in mf in the brain and kidneys while the reverse was noticed with the co-administration of IVM + ASA.

CONCLUSIONS

The treatment of Loa hyper-microfilaraemic individuals with ivermectin produces a clinical spectrum that parallels that seen in Loa hyper-microfilaraemic humans treated with ivermectin. The utilization of this experimental model can contribute to the improved management of the adverse responses in humans.

Ivermectin to reduce malaria transmission I. Pharmacokinetic and pharmacodynamic considerations regarding efficacy and safety

Ivermectin is an endectocide that has been used broadly in single dose community campaigns for the control of onchocerciasis and lymphatic filariasis for more than 30 years. There is now interest in the potential use of ivermectin regimens to reduce malaria transmission, envisaged as community-wide campaigns tailored to transmission patterns and as complement of the local vector control programme. The development of new ivermectin regimens or other novel endectocides will require integrated development of the drug in the context of traditional entomological tools and endpoints. This document examines the main pharmacokinetic and pharmacodynamic parameters of the medicine and their potential influence on its vector control efficacy and safety at population level. This information could be valuable for trial design and clinical development into regulatory and policy pathways.

A Splendid Gift from the Earth: The Origins and Impact of the Avermectins (Nobel Lecture)

Japanese soil was the origin of one of the most important drugs of the world: ivermectin. No other drug has such importance for the health of millions of people, particularly in the poor regions of the world. The discovery of the parent compounds of the avermectines is described first hand by S. Ōmura.

Research for new drugs for elimination of onchocerciasis in Africa

Onchocerciasis is a parasitic, vector borne disease caused by the filarial nematode Onchocerca volvulus. More than 99% of the population at risk of infection live in Africa. Onchocerciasis control was initiated in West Africa in 1974 with vector control, later complemented by ivermectin mass drug administration and in the other African endemic countries in 1995 with annual community directed treatment with ivermectin (CDTI.) This has significantly reduced infection prevalence. Together with proof-of-concept for onchocerciasis elimination with annual CDTI from foci in Senegal and Mali, this has resulted in targeting onchocerciasis elimination in selected African countries by 2020 and in 80% of African countries by 2025. The challenges for meeting these targets include the number of endemic countries where conflict has delayed or interrupted control programmes, cross-border foci, potential emergence of parasite strains with low susceptibility to ivermectin and co-endemicity of loiasis, another parasitic vector borne disease, which slows down or prohibits CDTI implementation. Some of these challenges could be addressed with new drugs or drug combinations with a higher effect on Onchocerca volvulus than ivermectin. This paper reviews the path from discovery of new compounds to their qualification for large scale use and the support regulatory authorities provide for development of drugs for neglected tropical diseases. The status of research for new drugs or treatment regimens for onchocerciasis along the path to regulatory approval and qualification for large scale use is reviewed. This research includes new regimens and combinations of ivermectin and albendazole, antibiotics targeting the O. volvulus endosymbiont Wolbachia, flubendazole, moxidectin and emodepside and discovery of new compounds.

Effect of Two or Six Doses 800 mg of Albendazole Every Two Months on Loa loa Microfilaraemia: A Double Blind, Randomized, Placebo-Controlled Trial

BACKGROUND

Loiasis is a parasitic infection endemic in the African rain forest caused by the filarial nematode Loa loa. Loiasis can be co-endemic with onchocerciasis and/or lymphatic filariasis. Ivermectin, the drug used in the control of these diseases, can induce serious adverse reactions in patients with high L loa microfilaraemia (LLM). A drug is needed which can lower LLM below the level that represents a risk so that ivermectin mass treatment to support onchocerciasis and lymphatic filariasis elimination can be implemented safely.

METHODOLOGY

Sixty men and women from a loiasis endemic area in Cameroon were randomized after stratification by screening LLM (≤ 30000, 30001-50000, >50000) to three treatment arms: two doses albendazole followed by 4 doses matching placebo (n = 20), six doses albendazole (n = 20) albendazole or 6 doses matching placebo (n = 20) administered every two months. LLM was measured before each treatment and 14, 18, 21 and 24 months after the first treatment. Monitoring for adverse events occurred three and seven days as well as 2 months after each treatment.

PRINCIPAL FINDINGS

None of the adverse events recorded were considered treatment related. The percentages of participants with ≥ 50% decrease in LLM from pre-treatment for ≥ 4 months were 53%, 17% and 11% in the 6-dose, 2-dose and placebo treatment arms, respectively. The difference between the 6-dose and the placebo arm was significant (p = 0.01). The percentages of participants with LLM < 8100 mf/ml for ≥ 4 months were 21%, 11% and 0% in the 6-dose, 2-dose and placebo treatment arms, respectively.

CONCLUSIONS/ SIGNIFICANCE

The 6-dose regimen reduced LLM significantly, but the reduction was insufficient to eliminate the risk of severe and/or serious adverse reactions during ivermectin mass drug administration in loiasis co-endemic areas.

Mass Drug Administration for Scabies Control in a Population with Endemic Disease

BACKGROUND

Scabies is an underrecognized cause of illness in many developing countries. It is associated with impetigo, which can lead to serious systemic complications. We conducted a trial of mass drug administration for scabies control in Fiji.

METHODS

We randomly assigned three island communities to one of three different interventions for scabies control: standard care involving the administration of permethrin to affected persons and their contacts (standard-care group), mass administration of permethrin (permethrin group), or mass administration of ivermectin (ivermectin group). The primary outcome was the change in the prevalence of scabies and of impetigo from baseline to 12 months.

RESULTS

A total of 2051 participants were enrolled; 803 were in the standard-care group, 532 in the permethrin group, and 716 in the ivermectin group. From baseline to 12 months, the prevalence of scabies declined significantly in all groups, with the greatest reduction seen in the ivermectin group. The prevalence declined from 36.6% to 18.8% in the standard-care group (relative reduction in prevalence, 49%; 95% confidence interval [CI], 37 to 60), from 41.7% to 15.8% in the permethrin group (relative reduction, 62%; 95% CI, 49 to 75), and from 32.1% to 1.9% in the ivermectin group (relative reduction, 94%; 95% CI, 83 to 100). The prevalence of impetigo also declined in all groups, with the greatest reduction seen in the ivermectin group. The prevalence declined from 21.4% to 14.6% in the standard-care group (relative reduction, 32%; 95% CI, 14 to 50), from 24.6% to 11.4% in the permethrin group (relative reduction, 54%; 95% CI, 35 to 73), and from 24.6% to 8.0% in the ivermectin group (relative reduction, 67%; 95% CI, 52 to 83). Adverse events were mild and were reported more frequently in the ivermectin group than in the permethrin group (15.6% vs. 6.8%).

CONCLUSIONS

Mass drug administration, particularly the administration of ivermectin, was efficacious for the control of scabies and impetigo. (Funded by the Australian National Health and Medical Research Council; Australian New Zealand Clinical Trials Registry number, ACTRN12613000474752.).

Parasitological, Hematological and Biochemical Characteristics of a Model of Hyper-microfilariaemic Loiasis (Loa loa) in the Baboon (Papio anubis)

Background

Loiasis, a filarial infection caused by Loa loa usually thought to cause relatively minor morbidity, can cause serious and often fatal reactions in patients carrying very high levels of circulating Loa loa microfilariae (mf) following administration of microfilaricidal drugs. An experimental model of this condition would greatly aid the definition of the optimal management of this important clinical presentation.

Methodology/Principle Findings

Fifteen baboons (Papio anubis) were infected with 600 infective larvae (L3) isolated from Chrysops vector flies. Animals were observed for any clinical changes; blood samples were collected every 1–2 months for 22 months, and analysed for parasitological, hematological and biochemical profiles using standard techniques. All animals became patent but remained clinically normal throughout the study. The parasitological pre-patent period was between 4–8 months, with a majority (60%) of animals becoming patent by 5 months post infection (MPI); all animals were patent by 8 MPI. Microfilarial loads increased steadily in all animals and reached a peak at 18 MPI. By 10 MPI >70% of animals had mf >8,000 mf/mL, and at 18 MPI >70% of animals had mf >30,000mf/mL with 50% of these animals with mf >50,000mf/mL. Absolute eosinophil, creatinine, Ca²⁺ and K⁺ levels were generally above normal values (NV). Positive associations were seen between microfilariaemia and eosinophilia, Hb, Ca²⁺, and gamma-GT values, whilst significant negative associations were seen between microfilariaemia and potassium, glucose and mononuclear leukocyte levels.

Conclusions

Infection of splenectomised baboons with L. loa can induce levels of circulating microfilariae, and corresponding haematological profiles, which parallel those seen in those humans in danger of the severe post-microfilariacide clinical responses. Utilization of this experimental model could contribute to the improved management of the loiasis related adverse responses in humans.

Loiasis is a filarial infection of humans that, in addition to causing severe direct clinical effects, is of concern to the global community’s efforts to eliminate the important filarial diseases, onchocerciasis and lymphatic filariasis, through causing interruption to mass drug distribution activities. Hyper-microfilariaemia has been seen to be the characteristic parameter in patients suffering from post ivermectin encephalopathy, a condition which sometimes leads to death. Understanding and developing appropriate approaches to the treatment and prevention of these severe adverse reactions has been difficult due to the lack of suitable models. As primates can be infected with human L. loa, and can develop hyper-microfilariaemia, it is likely that they therefore can serve as suitable models for the investigation of this syndrome in humans. This current study shows that following splenectomy the circulating microfilarial loads are similar to those seen in humans, and that the clinical pathology profile following infection also appears to be similar. The consistent ability to induce microfilariae levels of above 30,000 mf/ml in more than 70% of the tested animals suggests that this is indeed a practical model for investigating the adverse events occurring in hyper-loiasis.

Chemotherapy in the treatment, control, and elimination of human onchocerciasis

Onchocerciasis treatment is one of the most positive stories in tropical medicine although major challenges remain to reaching the ultimate goal of disease elimination. Such challenges are to be expected when the therapeutic goal is to kill and safely remove a large multistage, efficient, metazoan infectious agent such as Onchocerca volvulus that has an exceptionally complicated relationship with its host. Successful control of onchocerciasis has often been hampered by host reactions following chemotherapy, that can sometimes cause significant tissue pathology. Presence of other filariae, particularly Loa loa, in endemic onchocerciasis-treatment areas also poses severe problems due to adverse reactions caused by drug-induced death of the coincident microfilariae of this usually clinically benign species. Although ivermectin has been very successful, there is a need to enhance the progress toward elimination of onchocerciasis; new drugs and their efficient use are keys to this. The permanent absence of Onchocerca microfilaridermia, defined as the lack of resurgence of skin microfilarial loads after treatment, is the ultimate characteristic of a useful new chemotherapeutic agent. Several drugs are under investigation to achieve this, including the reassessment of currently available and previously tested agents, such as the antibiotic, doxycycline, which targets the adult parasites through its anti-Wolbachia endosymbiont activity. Flubendazole, a benzimidazole derivative approved for treatment of human gastrointestinal nematodes, is also being considered for repurposing as a macrofilaricide to aid in the achievement of eradication. The managerial challenges existing at the population level also need to be addressed; these include drug-distribution fatigue, the need to include noncompliant people, civil unrest in endemic areas, political cross-border issues, restrictions of age and pregnancy, and complications due to integration with other treatment programs. It is likely that a panel of chemotherapeutic options, new and old, supported by strong and effective distribution systems will be the best way to address challenges of treatment and elimination of this infection. Future research should also address management of treatment and control, and consider how new treatment paradigms can be incorporated to meet time lines set for global elimination by 2025.

Repurposed automated handheld counter as a point-of-care tool to identify individuals 'at risk' of serious post-ivermectin encephalopathy

Introduction

Administration of ivermectin (IVM) as part of mass drug administration (MDA) campaigns for onchocerciasis and/or lymphatic filariasis (LF) has been suspended in areas co-endemic for Loa loa due to severe post-treatment adverse events (SAEs) associated with high-burden of infection (>30,000 mf/ml). One simple approach for preventing SAEs is to identify and exclude individuals at risk from MDA. Here, we describe a repurposed hand-held automated cell counter (Scepter 2.0; HHAC) as a rapid, point-of-care method for quantifying microfilariae (mf) in the blood of infected individuals.

Methodology/Principal Findings

The quantification of microfilarial levels in blood of naturally infected humans, experimentally infected baboons, or mf-spiked human blood was tested using a microfluidic-based automated counter and compared to traditional calibrated thick-smears. We demonstrate that mf can be quantified in 20 µl of whole blood following lysis with 10% saponin within a minute of obtaining blood. There was a highly significant concordance between the counts obtained by the HHAC and those by microscopy for mf densities of >5,000 (p<0.0001, r_c = 0.97) or >30,000 per ml (p<0.0001, r_c = 0.90). Preliminary proof of concept field studies in Cameroon with 20 µl of blood from L. loa infected humans (n = 22) and baboons (n = 4) also demonstrated a significantly high concordance (p<0.0001, r_c = 0.89) with calibrated thick blood smears counts.

Conclusions/Significance

A repurposed HHAC is a portable, sensitive, rapid, point-of-care and quantitative tool to identify individuals with high levels of L. loa mf that put them at risk for SAEs following MDA. In addition, it provides ease of data storage and accessibility.

Mass drug administration (MDA) efforts with ivermectin-based regimens for onchocerciasis and for lymphatic filariasis in Africa have been suspended in certain areas that are co-endemic for Loa loa infection. This is due to the serious adverse events (encephalopathy and death) that can develop following ivermectin administration in individuals with very high circulating levels of Loa loa microfilariae (mf) (>30,000 mf/ml). Currently thick-blood smears are performed to quantify the mf levels that are neither rapid nor high throughput. To develop a point of care (POC) strategy for rapid and high throughput mf quantification, a repurposed handheld automated counter (HHAC) was assessed and shown to be an efficient POC tool to identify individuals with very high Loa loa microfilaraemia in a manner sufficient to be used as part of a Test and (not) Treat (TNT) program in an effort to restart the suspended MDA programs while preventing severe adverse neurologic events.

The lack of influence of food and local alcoholic brew on the blood level of Mectizan(®) (ivermectin)

There is concern that extraneous factors, such as food and drink, may alter the pharmacodynamics of Mectizan(®) (ivermectin) in patients receiving this important anti-parasitic drug, and thus might put such individuals in danger of serious adverse events. The effects of a common local alcohol-containing beverage and a local food on plasma levels of ivermectin were studied in Sudanese volunteers after administration of the standard dose used in mass drug administration programs for onchocerciasis and filariasis. Plasma levels of ivermectin at various time points (0-48h) after administration of ivermectin were ascertained by HPLC assay in ten volunteers given 150μgkg(-1) ivermectin together with either a local sorghum-based food ('assida'), or a locally brewed alcoholic beverage ('arangi' made from sorghum grain) or in those who were fasting. Maximum mean (±SD) plasma levels of ivermectin (67±49ngml(-1)) were reached within 2h in fasting patients, and had dropped to 26±20ngml(-1) after 30h. The coadministration of local food or alcoholic beverage did not cause an increase in ivermectin plasma levels above those observed in people who were fasting. However, at 2h after ivermectin administration, patients given alcohol had significantly lower plasma ivermectin levels than fed patients or fasting patients. There were no significant differences among treatments for AUC0-30, Cmax, or tmax, and so the coadministration of local food or alcoholic beverage did not cause any change in pharmacokinetic parameters of ivermectin in the plasma in comparison with fasting. None of the measured levels of plasma ivermectin were greater than those reported in previous studies with this compound. These findings do not support the hypothesis that acute intake of alcohol is an important factor in the development of the serious adverse reactions that can occur during the treatment of loaisis patients with ivermectin (Mectizan(®)).

Progress and challenges in the discovery of macrofilaricidal drugs

Control of human filarial infections currently depends on chemotherapeutic strategies predominantly directed at microfilariae. Doxycycline therapy in an extended daily dose regimen sterilizes and kills adult stages, but the utility of this drug for routine field use remains an issue of concern. No macrofilaricidal drugs with efficacy after one or two doses are available for use, delaying the achievement of the elimination or eradication of onchocerciasis and lymphatic filariasis. Moxidectin, a macrocyclic lactone, is currently in clinical trials for onchocerciasis. A few other drugs that have already been approved for use in veterinary practice or in human medicine for other indications are available for investigation. Early drug discovery pipelines are poorly populated and the process of macrofilaricide discovery and development remains highly challenging. In particular, the lack of convenient, validated animal models in an antifilarial drug discovery pathway is an unresolved issue.

Ivermectin to reduce malaria transmission: a research agenda for a promising new tool for elimination

Background

The heterogeneity of malaria transmission makes widespread elimination a difficult goal to achieve. Most of the current vector control measures insufficiently target outdoor transmission. Also, insecticide resistance threatens to diminish the efficacy of the most prevalent measures, indoor residual spray and insecticide treated nets. Innovative approaches are needed. The use of endectocides, such as ivermectin, could be an important new addition to the toolbox of anti-malarial measures. Ivermectin effectively targets outdoor transmission, has a novel mechanism of action that could circumvent resistance and might be distributed over the channels already in place for the control of onchocerciasis and lymphatic filariasis.

Methods

The previous works involving ivermectin and Anopheles vectors are reviewed and summarized. A review of ivermectin’s safety profile is also provided. Finally three definitive clinical trials are described in detail and proposed as the evidence needed for implementation. Several smaller and specific supportive studies are also proposed.

Conclusions

The use of ivermectin solves many challenges identified for future vector control strategies. It is an effective and safe endectocide that was approved for human use more than 25 years ago. Recent studies suggest it might become an effective and complementary strategy in malaria elimination and eradication efforts; however, intensive research will be needed to make this a reality.

Relative neurotoxicity of ivermectin and moxidectin in Mdr1ab (-/-) mice and effects on mammalian GABA(A) channel activity

The anthelmintics ivermectin (IVM) and moxidectin (MOX) display differences in toxicity in several host species. Entrance into the brain is restricted by the P-glycoprotein (P-gp) efflux transporter, while toxicity is mediated through the brain GABA(A) receptors. This study compared the toxicity of IVM and MOX in vivo and their interaction with GABA(A) receptors in vitro. Drug toxicity was assessed in Mdr1ab(−/−) mice P-gp-deficient after subcutaneous administration of increasing doses (0.11–2.0 and 0.23–12.9 µmol/kg for IVM and MOX in P-gp-deficient mice and half lethal doses (LD₅₀) in wild-type mice). Survival was evaluated over 14-days. In Mdr1ab(−/−) mice, LD₅₀ was 0.46 and 2.3 µmol/kg for IVM and MOX, respectively, demonstrating that MOX was less toxic than IVM. In P-gp-deficient mice, MOX had a lower brain-to-plasma concentration ratio and entered into the brain more slowly than IVM. The brain sublethal drug concentrations determined after administration of doses close to LD₅₀ were, in Mdr1ab(−/−) and wild-type mice, respectively, 270 and 210 pmol/g for IVM and 830 and 740–1380 pmol/g for MOX, indicating that higher brain concentrations are required for MOX toxicity than IVM. In rat α1β2γ2 GABA channels expressed in Xenopus oocytes, IVM and MOX were both allosteric activators of the GABA-induced response. The Hill coefficient was 1.52±0.45 for IVM and 0.34±0.56 for MOX (p<0.001), while the maximum potentiation caused by IVM and MOX relative to GABA alone was 413.7±66.1 and 257.4±40.6%, respectively (p<0.05), showing that IVM causes a greater potentiation of GABA action on this receptor. Differences in the accumulation of IVM and MOX in the brain and in the interaction of IVM and MOX with GABA(A) receptors account for differences in neurotoxicity seen in intact and Mdr1-deficient animals. These differences in neurotoxicity of IVM and MOX are important in considering their use in humans.

Ivermectin (IVM) is used for onchocerciasis mass drug administration and is important for control of lymphatic filariasis, strongyloidiases and Scarcoptes mange in humans. It is widely used for parasite control in livestock. Moxidectin (MOX) is being evaluated against Onchocerca volvulus in humans and is also widely used in veterinary medicine. Both anthelmintics are macrocyclic lactones (MLs) that act on ligand-gated chloride channels and share similar spectra of activity. Nevertheless, there are marked differences in their pharmacokinetics, pharmacodynamics and toxicity. Usually, both MLs are remarkably safe drugs. However, there are reports of severe adverse events to IVM, in some humans with high Loa loa burdens, and IVM can be neurotoxic in animals with defects in P-glycoproteins (P-gp) in the blood-brain barrier. We have compared the in vivo neurotoxicity of IVM and MOX in P-gp-deficient mice and their accumulation in brain. We also investigated their effects on mammalian GABA receptors. We show that MOX has a wider margin of safety than IVM, even when the blood-brain barrier function is impaired, and that the neurotoxicity in vivo is related to different effects of the drugs on GABA-gated channels. These observations contribute to understanding ML toxicity and open new perspectives for possible MOX use in humans.

Macrocyclic Lactone Endectocides

The macrocyclic lactone endectocides such as ivermectin, abamectin, selamectin and moxidectin have revolutionized the treatment of parasitic diseases in animals, being active against internal and external parasites. Ivermectin was introduced into veterinary medicine in the 1980s and since that time a number of related compounds have been introduced. In the treatment of internal parasites they complement the use of levamisole and the benzimidazoles, but in recent years they have found utility in treating external insect parasites. These agents show very low levels of toxicity under most circumstances. However, they are neurotoxic particularly in subpopulations of animals with mutations in the MDR1 gene. Toxicity may be also seen during off-label use, possibly because the doses used have been extrapolated from use in other animals. Regardless of these considerations, the macrocyclic lactone endectocides are extremely effective and safe drugs in the treatment of parasitic diseases of animals.

Ivermectin, 'wonder drug' from Japan: the human use perspective

Discovered in the late-1970s, the pioneering drug ivermectin, a dihydro derivative of avermectin--originating solely from a single microorganism isolated at the Kitasato Institute, Tokyo, Japan from Japanese soil--has had an immeasurably beneficial impact in improving the lives and welfare of billions of people throughout the world. Originally introduced as a veterinary drug, it kills a wide range of internal and external parasites in commercial livestock and companion animals. It was quickly discovered to be ideal in combating two of the world's most devastating and disfiguring diseases which have plagued the world's poor throughout the tropics for centuries. It is now being used free-of-charge as the sole tool in campaigns to eliminate both diseases globally. It has also been used to successfully overcome several other human diseases and new uses for it are continually being found. This paper looks in depth at the events surrounding ivermectin's passage from being a huge success in Animal Health into its widespread use in humans, a development which has led many to describe it as a "wonder" drug.

Analysis of the mdr-1 gene in patients co-infected with Onchocerca volvulus and Loa loa who experienced a post-ivermectin serious adverse event

Ivermectin (IVM) is exceptionally safe in humans, and is used for mass treatment of onchocerciasis and lymphatic filariasis. However, cases of encephalopathy, sometimes fatal, have been reported in a small number of individuals who harbored large numbers of Loa loa microfilariae (mf). A loss-of-function mutation in the mdr-1 gene in some dog breeds and in mice leads to accumulation of the drug in the brain, causing coma and death. This hypothesis was tested in four individuals from Cameroon who experienced a post-IVM serious adverse event (SAE) and in nine non-SAE matched controls. No loss-of-function mutation was detected in mdr-1 in any subject. However, haplotypes, associated with altered drug disposition, were present as homozygotes in two of the SAE patients (50%), but absent as homozygotes in the controls (0%). An association of high Loa mf load and a genetic predisposition to altered IVM distribution could be involved in IVM SAEs.

Canine mdr1 gene mutation in Japan

Frequency of the 4-bp deletion mutant in canine mdr1 gene was examined in 193 dogs of eight breeds in Japan. The mutant allele was found in Collies, Australian Shepherds, and Shetland Sheepdogs, where its respective frequencies were 58.3%, 33.3%, and 1.2%. The MDR1 protein was detected on peripheral blood mononuclear cells (PBMC) from a MDR1/MDR1 dog, but not on PBMC from a mdr1-1Delta/mdr1-1Delta Collie. Rhodamine 123 was extruded from MDR1/MDR1 lymphocytes. That excretion was inhibited by a MDR1 inhibitor, verapamil. On the other hand, Rh123 excretion was not observed from lymphocytes derived from a mdr1-1Delta/mdr1-1Delta Collie. These results indicated that the mutant mdr1 allele also existed in Collie-breed dogs in Japan at high rates and that mdr1-1Delta /mdr1-1Delta dogs have no functional MDR1.

Liquid chromatographic assay of ivermectin in human plasma for application to clinical pharmacokinetic studies

There is a need for an accurate, sensitive and selective high-performance liquid chromatography (HPLC) method for the quantitation of ivermectin in human plasma that separates the parent drug from metabolites. Ivermectin and the internal standard, moxidectin, were extracted from 0.2 ml of human plasma using Oasis HLB solid phase extraction cartridges. After extraction, fluorescent derivatives of ivermectin and moxidectin were made by reaction with trifluoroacetic anhydride and N-methylimidazole. Separation was achieved on a Alltech Ultrasphere C18 5mu column with a mobile phase composed of tetrahydrofuran-acetonitrile-water (40:38:22 v/v/v). Detection is by fluorescence, with an excitation of 365 nm and emission of 475 nm. The retention times of ivermectin and internal standard, moxidectin are approximately 24.5 and 12.5 min, respectively. The assay is linear over the concentration range of 0.2-200 ng/ml of ivermectin in human plasma (r = 0.9992, weighted by 1/concentration). Recoveries of ivermectin are greater than 80% at all concentrations. The analysis of quality control samples for ivermectin 0.2, 25, and 200 ng/ml demonstrated excellent precision with coefficient of variation of 6.1, 3.6 and 2.3%, respectively (n = 6). The method is accurate with all intra-day (n = 6) and interday (n = 12) mean concentration within 10% of nominal values at all quality control sample concentrations. Storage stability for 30 days at -80 degrees C and after three freeze-thaw cycles are within acceptable limits. The method separates ivermectin from multiple less and more polar unidentified metabolites. This method is robust and suitable for clinical pharmacokinetic studies. The analytical procedure has been applied to a pharmacokinetic study of ivermectin in healthy volunteers and to the analysis of plasma specimens from patients with disseminated strongyloidiasis.

Frequency of the nt230 (del4) MDR1 mutation in Collies and related dog breeds in Germany

MDR1 (ABCB1) P-glycoprotein exerts a protective function in the blood-brain barrier thereby limiting the entry of many drugs and other xenobiotics to the central nervous system. A nonsense mutation has been described for Collies and related dog breeds which abolishes this function and is associated with increased susceptibility to neurotoxic side effects of several drugs including ivermectin, moxidectin and loperamide. In order to evaluate the occurrence and frequency of this nt230 (del4) MDR1 mutation in Germany, we screened 1500 dogs. Frequency of the homozygous mutated genotype was highest for Collies (33.0%), followed by Australian Shepherd (6.9%) and Shetland Sheepdog (5.7%). Thirty-seven percent of the Wäller dogs and 12.5% of the Old English Sheepdogs were heterozygous for the mutant MDR1 (-) allele. Considering the predominant role of MDR1 P-glycoprotein in drug disposition and in particular for blood-brain barrier protection, MDR1 genotype-based breeding programs are recommended for improving the safety of drug therapy in these canine breeds.