The Mazzotti reaction following treatment of onchocerciasis with diethylcarbamazine: clinical severity as a function of infection intensity

Association of haemato-biochemical indices and blood composite ratios with microfilaridermia in Onchocerciasis patients

BACKGROUND

Onchocerciasis causes chronic systemic inflammation. Several studies have used markers such as haemato-biochemical indices to predict the occurrence of systemic inflammation. This study assessed the variability and predictability of haemato-biochemical indices and blood composite ratios (BCRs) in microfilariae positive (MF+) and microfilariae negative (MF-) subgroups of onchocercomata participants.

METHODS

One hundred and five (105) MF + and 34 MF- participants were retrospectively recruited into the study. Screening for the presence of O. volvulus microfilariae was done from skin snips taken from the left and right iliac crests of participants using established and approved protocols. Haematological and biochemical indices were measured using standard laboratory automated analyzers. Blood composite ratios (BCRs) were calculated as ratios of the absolute parameters involved.

RESULTS

A significantly increased total WBC, absolute eosinophil, eosinophil percent and absolute basophil were observed in the MF + participants compared to MF- participants. Reduced gamma-glutamyl transferase (GGT) with increased estimated glomerular filtration rate (eGFR) was significantly associated with MF + participants compared to MF- participants. BCRs were significantly higher for eosinophil-to-neutrophil ratio (ENR), eosinophil-to-monocyte ratio (EMR), eosinophil-to-basophil ratio (EBR) and eosinophil-to-lymphocyte ratio (ELR) in MF + participants compared to MF- participants. After multivariate adjustment, onchocercomata participants with increased eosinophil counts (aOR = 13.86, 95% CI [2.07-92.90], p = 0.007), ENR x10 (aOR = 1.42, 95% CI [1.05-1.93], p = 0.025), EMR (aOR = 2.64, 95% CI [1.25-5.60], p = 0.011), EBR (aOR = 1.07, 95% CI [1.01-1.10], p = 0.020) and ELR x10 (aOR = 1.69, 95% CI [1.14-2.51], p = 0.009) were more likely to have microfilaridermia.

CONCLUSIONS

Elevated eosinophil counts with higher ENR, EMR, EBR and ELR levels are significantly associated with microfilaridermia in onchocercomata participants. Combining BCRs with eosinophil count significantly led to an improvement in the conventional model for predicting microfilaridermia.

Onchocerca volvulus microfilariae in the anterior chambers of the eye and ocular adverse events after a single dose of 8 mg moxidectin or 150 µg/kg ivermectin: results of a randomized double-blind Phase 3 trial in the Democratic Republic of the Congo, Ghana and Liberia

BACKGROUND

After ivermectin became available, diethylcarbamazine (DEC) use was discontinued because of severe adverse reactions, including ocular reactions, in individuals with high Onchocerca volvulus microfilaridermia (microfilariae/mg skin, SmfD). Assuming long-term ivermectin use led to < 5 SmfD with little or no eye involvement, DEC + ivermectin + albendazole treatment a few months after ivermectin was proposed. In 2018, the US FDA approved moxidectin for treatment of O. volvulus infection. The Phase 3 study evaluated SmfD, microfilariae in the anterior chamber (mfAC) and adverse events (AEs) in ivermectin-naïve individuals with ≥ 10 SmfD after 8 mg moxidectin (n = 978) or 150 µg/kg ivermectin (n = 494) treatment.

METHODS

We analyzed the data from 1463 participants with both eyes evaluated using six (0, 1-5, 6-10, 11-20, 21-40, > 40) mfAC and three pre-treatment (< 20, 20 to < 50, ≥ 50) and post-treatment (0, > 0-5, > 5) SmfD categories. A linear mixed model evaluated factors and covariates impacting mfAC levels. Ocular AEs were summarized by type and start post-treatment. Logistic models evaluated factors and covariates impacting the risk for ocular AEs.

RESULTS

Moxidectin and ivermectin had the same effect on mfAC levels. These increased from pre-treatment to Day 4 and Month 1 in 20% and 16% of participants, respectively. Six and 12 months post-treatment, mfAC were detected in ≈5% and ≈3% of participants, respectively. Ocular Mazzotti reactions occurred in 12.4% of moxidectin- and 10.2% of ivermectin-treated participants without difference in type or severity. The risk for ≥ 1 ocular Mazzotti reaction increased for women (OR 1.537, 95% CI 1.096-2.157) and with mfAC levels pre- and 4 days post-treatment (OR 0: > 10 mfAC 2.704, 95% CI 1.27-5.749 and 1.619, 95% CI 0.80-3.280, respectively).

CONCLUSIONS

The impact of SmfD and mfAC levels before and early after treatment on ocular AEs needs to be better understood before making decisions on the risk-benefit of strategies including DEC. Such decisions should take into account interindividual variability in SmfD, mfAC levels and treatment response and risks to even a small percentage of individuals.

The pipeline for drugs for control and elimination of neglected tropical diseases: 2. Oral anti-infective drugs and drug combinations for off-label use

In its 'Road map for neglected tropical diseases 2021-2030', the World Health Organization outlined its targets for control and elimination of neglected tropical diseases (NTDs) and research needed to achieve them. For many NTDs, this includes research for new treatment options for case management and/or preventive chemotherapy. Our review of small-molecule anti-infective drugs recently approved by a stringent regulatory authority (SRA) or in at least Phase 2 clinical development for regulatory approval showed that this pipeline cannot deliver all new treatments needed. WHO guidelines and country policies show that drugs may be recommended for control and elimination for NTDs for which they are not SRA approved (i.e. for 'off-label' use) if efficacy and safety data for the relevant NTD are considered sufficient by WHO and country authorities. Here, we are providing an overview of clinical research in the past 10 years evaluating the anti-infective efficacy of oral small-molecule drugs for NTD(s) for which they are neither SRA approved, nor included in current WHO strategies nor, considering the research sponsors, likely to be registered with a SRA for that NTD, if found to be effective and safe. No such research has been done for yaws, guinea worm, Trypanosoma brucei gambiense human African trypanosomiasis (HAT), rabies, trachoma, visceral leishmaniasis, mycetoma, T. b. rhodesiense HAT, echinococcosis, taeniasis/cysticercosis or scabies. Oral drugs evaluated include sparfloxacin and acedapsone for leprosy; rifampicin, rifapentin and moxifloxacin for onchocerciasis; imatinib and levamisole for loiasis; itraconazole, fluconazole, ketoconazole, posaconazole, ravuconazole and disulfiram for Chagas disease, doxycycline and rifampicin for lymphatic filariasis; arterolane, piperaquine, artesunate, artemether, lumefantrine and mefloquine for schistosomiasis; ivermectin, tribendimidine, pyrantel, oxantel and nitazoxanide for soil-transmitted helminths including strongyloidiasis; chloroquine, ivermectin, balapiravir, ribavirin, celgosivir, UV-4B, ivermectin and doxycycline for dengue; streptomycin, amoxicillin, clavulanate for Buruli ulcer; fluconazole and isavuconazonium for mycoses; clarithromycin and dapsone for cutaneous leishmaniasis; and tribendimidine, albendazole, mebendazole and nitazoxanide for foodborne trematodiasis. Additional paths to identification of new treatment options are needed. One promising path is exploitation of the worldwide experience with 'off-label' treatment of diseases with insufficient treatment options as pursued by the 'CURE ID' initiative.

The search for better treatment strategies for mansonellosis: an expert perspective

INTRODUCTION

Four species of the Mansonella genus infect millions of people across sub-Saharan Africa and Central and South America. Most infections are asymptomatic, but mansonellosis can be associated with nonspecific clinical manifestations such as fever, headache, arthralgia, and ocular lesions (M. ozzardi); pruritus, arthralgia, abdominal pain, angioedema, skin rash, and fatigue (M. perstans and perhaps Mansonella sp. 'DEUX'); and pruritic dermatitis and chronic lymphadenitis (M. perstans).

AREAS COVERED

We searched the PubMed and SciELO databases for publications on mansonelliasis in English, Spanish, Portuguese, or French that appeared until 1 May 2023. Literature data show that anthelmintics - single-dose ivermectin for M. ozzardi, repeated doses of mebendazole alone or in combination with diethylcarbamazine (DEC) for M. perstans, and DEC alone for M. streptocerca - are effective against microfilariae. Antibiotics that target Wolbachia endosymbionts, such as doxycycline, are likely to kill adult worms of most, if not all, Mansonella species, but the currently recommended 6-week regimen is relatively impractical. New anthelmintics and shorter antibiotic regimens (e.g. with rifampin) have shown promise in experimental filarial infections and may proceed to clinical trials.

EXPERT OPINION

We recommend that human infections with Mansonella species be treated, regardless of any apparent clinical manifestations. We argue that mansonellosis, despite being widely considered a benign infection, may represent a direct or indirect cause of significant morbidity that remains poorly characterized at present.

The efficacy of the benzimidazoles oxfendazole and flubendazole against Litomosoides sigmodontis is dependent on the adaptive and innate immune system

Filarial nematodes can cause debilitating diseases such as lymphatic filariasis and onchocerciasis. Oxfendazole (OXF) is one promising macrofilaricidal candidate with improved oral availability compared to flubendazole (FBZ), and OXF is currently under preparation for phase 2 clinical trials in filariasis patients. This study aimed to investigate the immune system's role during treatment with OXF and FBZ and explore the potential to boost the treatment efficacy via stimulation of the immune system. Wild type (WT) BALB/c, eosinophil-deficient ΔdblGata1, IL-4r/IL-5^-/-, antibody-deficient μMT and B-, T-, NK-cell and ILC-deficient Rag2/IL-2rγ^-/- mice were infected with the rodent filaria Litomosoides sigmodontis and treated with an optimal and suboptimal regimen of OXF and FBZ for up to 5 days. In the second part, WT mice were treated for 2-3 days with a combination of OXF and IL-4, IL-5, or IL-33. Treatment of WT mice reduced the adult worm burden by up to 94% (OXF) and 100% (FBZ) compared to vehicle controls. In contrast, treatment efficacy was lower in all immunodeficient strains with a reduction of up to 90% (OXF) and 75% (FBZ) for ΔdblGata1, 50 and 92% for IL-4r/IL-5^-/-, 64 and 78% for μMT or 0% for Rag2/IL-2rγ^-/- mice. The effect of OXF on microfilariae and embryogenesis displayed a similar pattern, while FBZ's ability to prevent microfilaremia was independent of the host's immune status. Furthermore, flow cytometric analysis revealed strain-and treatment-specific immunological changes. The efficacy of a shortened 3-day treatment of OXF (-33% adult worms vs. vehicle) could be boosted to a 91% worm burden reduction via combination with IL-5, but not IL-4 or IL-33. Our results suggest that various components of the immune system support the filaricidal effect of benzimidazoles in vivo and present an opportunity to boost treatment efficacy.

Filariasis research - from basic research to drug development and novel diagnostics, over a decade of research at the Institute for Medical Microbiology, Immunology and Parasitology, Bonn, Germany

Filariae are vector borne parasitic nematodes, endemic in tropical and subtropical regions causing avoidable infections ranging from asymptomatic to stigmatizing and disfiguring disease. The filarial species that are the major focus of our institution's research are Onchocerca volvulus causing onchocerciasis (river blindness), Wuchereria bancrofti and Brugia spp. causing lymphatic filariasis (elephantiasis), Loa loa causing loiasis (African eye worm), and Mansonella spp causing mansonellosis. This paper aims to showcase the contribution of our institution and our collaborating partners to filarial research and covers decades of long research spanning basic research using the Litomosoides sigmodontis animal model to development of drugs and novel diagnostics. Research with the L. sigmodontis model has been extensively useful in elucidating protective immune responses against filariae as well as in identifying the mechanisms of filarial immunomodulation during metabolic, autoimmune and infectious diseases. The institute for Medical Microbiology, Immunology and Parasitology (IMMIP), University Hospital Bonn (UKB), Bonn, Germany has also been actively involved in translational research in contributing to the identification of new drug targets and pre-clinical drug research with successful and ongoing partnership with sub-Saharan Africa, mainly Ghana (the Kumasi Centre for Collaborative Research (KCCR)), Cameroon (University of Buea (UB)) and Togo (Laboratoire de Microbiologie et de Contrôle de Qualité des Denrées Alimentaires (LAMICODA)), Asia and industry partners. Further, in the direction of developing novel diagnostics that are sensitive, time, and labour saving, we have developed sensitive qPCRs as well as LAMP assays and are currently working on artificial intelligence based histology analysis for onchocerciasis. The article also highlights our ongoing research and the need for novel animal models and new drug targets.

Cases of Loiasis Among a Congolese Family: Screening for Loiasis Among Newly Arrived Refugees From Endemic Areas

Loiasis is a parasitic infection caused by the filarial nematode Loa loa within endemic regions of West and Central Africa. These regions include areas co-endemic for other nematode infections. Although loiasis is rarely seen in the United States (US), primary care providers who regularly see refugees from endemic areas should be aware of its clinical presentation, diagnostic work-up, and initial management. Given the challenges of diagnosing loiasis, especially in low prevalence settings, we present cases of four family members, two of whom were diagnosed with loiasis, and discuss an approach to screening populations from endemic regions during their initial Refugee Health Examination upon arrival to the US.

Corallopyronin A: antimicrobial discovery to preclinical development

Covering: August 1984 up to January 2022Worldwide, increasing morbidity and mortality due to antibiotic-resistant microbial infections has been observed. Therefore, better prevention and control of infectious diseases, as well as appropriate use of approved antibacterial drugs are crucial. There is also an urgent need for the continuous development and supply of novel antibiotics. Thus, identifying new antibiotics and their further development is once again a priority of natural product research. The antibiotic corallopyronin A was discovered in the 1980s in the culture broth of the Myxobacterium Corallococcus coralloides and serves, in the context of this review, as a show case for the development of a naturally occurring antibiotic compound. The review demonstrates how a hard to obtain, barely water soluble and unstable compound such as corallopyronin A can be developed making use of sophisticated production and formulation approaches. Corallopyronin A is a bacterial DNA-dependent RNA polymerase inhibitor with a new target site and one of the few representatives of this class currently in preclinical development. Efficacy against Gram-positive and Gram-negative pathogens, e.g., Chlamydia trachomatis, Orientia tsutsugamushi, Staphylococcus aureus, and Wolbachia has been demonstrated. Due to its highly effective in vivo depletion of Wolbachia, which are essential endobacteria of most filarial nematode species, and its robust macrofilaricidal efficacy, corallopyronin A was selected as a preclinical candidate for the treatment of human filarial infections. This review highlights the discovery and production optimization approaches for corallopyronin A, as well as, recent preclinical efficacy results demonstrating a robust macrofilaricidal effect of the anti-Wolbachia candidate, and the solid formulation strategy which enhances the stability as well as the bioavailability of corallopyronin A.

Current perspective of new anti-Wolbachial and direct-acting macrofilaricidal drugs as treatment strategies for human filariasis

Filarial diseases like lymphatic filariasis and onchocerciasis belong to the Neglected Tropical Diseases and remain a public health problem in endemic countries. Lymphatic filariasis and onchocerciasis can lead to stigmatizing pathologies and present a socio-economic burden for affected people and their endemic countries. Current treatment recommendations by the WHO include mass drug administration with ivermectin for the treatment of onchocerciasis and a combination of ivermectin, albendazole and diethylcarbamazine (DEC) for the treatment of lymphatic filariasis in areas that are not co-endemic for onchocerciasis or loiasis. Limitations of these treatment strategies are due to potential severe adverse events in onchocerciasis and loiasis patients following DEC or ivermectin treatment, respectively, the lack of a macrofilaricidal efficacy of those drugs and the risk of drug resistance development. Thus, to achieve the elimination of transmission of onchocerciasis and the elimination of lymphatic filariasis as a public health problem by 2030, the WHO defined in its roadmap that new alternative treatment strategies with macrofilaricidal compounds are required. Within a collaboration of the non-profit organizations Drugs for Neglected Diseases initiative (DNDi), the Bill & Melinda Gates Foundation, and partners from academia and industry, several new promising macrofilaricidal drug candidates were identified, which will be discussed in this review.

Drug-induced uveitis: A review

Uveitis maybe induced by the use of various medications known as drug-induced uveitis (DIU), though rare it is an important cause of uveitis which one needs to be aware of. The drugs may be administered through any route including systemic, topical, and intravitreal. Ocular inflammation can be in the form of anterior, intermediate, posterior or pan uveitis, and rarely may present as episcleritis and scleritis. Identification of drug as the offending agent of uveitis is important as many a times stopping the drug may help recover the uveitis or the concomitant use of corticosteroids. An extensive literature review was done using the Pubmed. An overview of DIU is provided as it is important for us to be aware of this clinical entity.

Moxidectin: an oral treatment for human onchocerciasis

INTRODUCTION

Moxidectin is a milbemycin endectocide recently approved for the treatment of human onchocerciasis. Onchocerciasis, earmarked for elimination of transmission, is a filarial infection endemic in Africa, Yemen, and the Amazonian focus straddling Venezuela and Brazil. Concerns over whether the predominant treatment strategy (yearly mass drug administration (MDA) of ivermectin) is sufficient to achieve elimination in all endemic foci have refocussed attention upon alternative treatments. Moxidectin's stronger and longer microfilarial suppression compared to ivermectin in both phase II and III clinical trials indicates its potential as a novel powerful drug for onchocerciasis elimination.

AREAS COVERED

This work summarizes the chemistry and pharmacology of moxidectin, reviews the phase II and III clinical trials evidence on tolerability, safety, and efficacy of moxidectin versus ivermectin, and discusses the implications of moxidectin's current regulatory status.

EXPERT OPINION

Moxidectin's superior clinical performance has the potential to substantially reduce times to elimination compared to ivermectin. If donated, moxidectin could mitigate the additional programmatic costs of biannual ivermectin distribution because, unlike other alternatives, it can use the existing community-directed treatment infrastructure. A pediatric indication (for children <12 years) and determination of its usefulness in onchocerciasis-loiasis co-endemic areas will greatly help fulfill the potential of moxidectin for the treatment and elimination of onchocerciasis.

The Pathogenesis of Nodding Syndrome

Nodding syndrome is a rare, enigmatic form of pediatric epilepsy that has occurred in an epidemic fashion beginning in the early 2000s in geographically distinct regions of Africa. Despite extensive investigation, the etiology of nodding syndrome remains unclear, although much progress has been made in understanding the pathogenesis of the disease, as well as in treatment and prevention. Nodding syndrome is recognized as a defined disease entity, but it is likely one manifestation along a continuum of Onchocerca volvulus-associated neurological complications. This review examines the epidemiology of nodding syndrome and its association with environmental factors. It provides a critical analysis of the data that support or contradict the leading hypotheses of the etiologies underlying the pathogenesis of the syndrome. It also highlights the important progress made in treating and preventing this devastating neurological disease and prioritizes important areas for future research.

Effect of flubendazole on developing stages of Loa loa in vitro and in vivo: a new approach for screening filaricidal agents

BACKGROUND

Loiasis, an often-neglected tropical disease, is a threat to the success of lymphatic filariasis and onchocerciasis elimination programmes in rainforest areas of the central and western Africa. Its control and even its elimination might be possible through the use of a safe macrofilaricide, a prophylactic drug, or perhaps a vaccine. This present study evaluated the effect of flubendazole (FLBZ) on the development of Loa loa L3 in vitro and in vivo.

METHODS

Infective stages of L. loa were isolated and co-cultured in Dulbecco's Modified Eagle's Medium in the presence of monkey kidney epithelial cells (LLC-MK2) feeder cells. FLBZ and its principal metabolites, reduced flubendazole (RFLBZ) and hydrolyzed flubendazole (HFLBZ), were screened in vitro at concentrations 0.05, 0.1, 0.5, 1 and 10 μg/ml. The viability of the parasites was assessed microscopically daily for 15 days. For in vivo study, a total of 48 CcR3 KO mice were infected subcutaneously with 200 L. loa L3 and treated with 10 mg/kg FLBZ once daily for 5 consecutive days. Twenty-four animals were used as control and received L3 and vehicle. They were dissected at 5, 10, 15 and 20 days post-treatment for worm recovery.

RESULTS

The motility of L3 larvae in vitro was reduced from the second day of incubation with drugs at in vivo plasma concentration levels, with a strong correlation found between reduced motility and increased drug concentration (Spearman's rho = -0.9, P < 0.0001). Except for HFLBZ (0.05 μg/ml and 0.01 μg/ml), all concentrations of FLBZ, HFLBZ and RFLBZ interrupted the moulting of L. loa infective larvae to L4. In vivo, regardless of the experimental group, there was a decrease in parasite recovery with time. However, at each time point this reduction was more pronounced in the group of animals treated with FLBZ compared to equivalent control. Parasites were recovered from the flubendazole-treated groups only on day 5 post-inoculation at an average rate of 2.1%, a value significantly lower (Mann-Whitney U-test, U = 28, P = 0.0156) than the average of 31.1% recovered from the control group.

CONCLUSIONS

This study reveals the ability of flubendazole to inhibit the development of L. loa L3 both in vitro and in vivo, and in addition validates the importance of in vitro and animal models of L. loa as tools for the development of drugs against loiasis.

Nanomedicine Approaches Against Parasitic Worm Infections

Nanomedicine approaches have the potential to transform the battle against parasitic worm (helminth) infections, a major global health scourge from which billions are currently suffering. It is anticipated that the intersection of two currently disparate fields, nanomedicine and helminth biology, will constitute a new frontier in science and technology. This progress report surveys current innovations in these research fields and discusses research opportunities. In particular, the focus is on: (1) major challenges that helminth infections impose on mankind; (2) key aspects of helminth biology that inform future research directions; (3) efforts to construct nanodelivery platforms to target drugs and genes to helminths hidden in their hosts; (4) attempts in applying nanotechnology to enable vaccination against helminth infections; (5) outlooks in utilizing nanoparticles to enhance immunomodulatory activities of worm-derived factors to cure allergy and autoimmune diseases. In each section, achievements are summarized, limitations are explored, and future directions are assessed.

Heterogeneity in the in vitro susceptibility of Loa loa microfilariae to drugs commonly used in parasitological infections

Background

Co-infection with loiasis remains a potential problem in control programs targeting filarial infections. The effects of many anti-parasitic drugs often administered to Loa loa infected people are not well documented. This study compared the in vitro activity of several of these drugs on the viability of L. loa microfilariae (mf).

Methods

Human strain L. loa mf were isolated from baboon blood using iso-osmotic Percoll gradient, and cultured in RPMI 1640/10% FBS with antimalarial drugs (mefloquine, amodiaquine, artesunate, chloroquine and quinine), anthelmintics (ivermectin, praziquantel, flubendazole and its reduced and hydrolyzed metabolites), two potential trypanocidal agents (fexinidazole and Scynexis-7158) and the anticancer drug imatinib. The drug concentrations used varied between 0.156 μg/ml and 10 μg/ml. Mf motility (CR₅₀ = 50% immotility) and a metabolic viability assay (MTT) were used to assess the effects of these drugs on the parasites.

Results

Mf in control cultures showed only a slight reduction in motility after 5 days of culture. Active inhibition of Loa loa motility was seen with mefloquine and amodiaquine (CR₅₀ values of 3.87 and 4.05 μg/ml, respectively), immobilizing > 90% mf within the first 24 hours: mefloquine killed the mf after 24 hours of culture at concentrations ≥ 5 μg/ml. SCYX-7158 also induced a concentration-dependent reduction in mf motility, with > 50% reduction in mf motility seen after 5 days at 10 μg/ml. The anticancer drug imatinib reduced mf motility at 10 μg/ml from the first day of incubation to 55% by day 5, and the reduction in motility was concentration-dependent. Praziquantel and fexinidazole were inactive, and FLBZ and its metabolites, as well as ivermectin at concentrations > 5 μg/ml, had very minimal effects on mf motility over the first 4 days of culture.

Conclusions

The considerable action of the anti-malarial drugs mefloquine and amodiaquine on Loa mf in vitro highlights the possibility of repurposing the existing anti-infectious agents for the development of drugs against loiasis. The heterogeneity in the activity of anti-parasitic agents on Loa loa mf supports the need for further investigation using animal models of loiasis.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2799-3) contains supplementary material, which is available to authorized users.

Assessment of macrofilaricidal activity of leaf extracts of Terminalia sp. against bovine filarial parasite Setaria cervi

Antifilarial potential of three medicinal plants namely, Terminalia bellerica, Terminalia chebula and Terminalia catappa was explored using Setaria cervi, a bovine filarial parasite at concentrations of 2.5, 5 and 10mg/ml. Amongst all the extracts, methanol extract of T. bellerica showed highest macrofilaricidal activity i.e. 84.63±1.11 at 10mg/ml in MTT reduction assay with IC₅₀ value of 2.7mg/ml. which was better than the standard DEC i.e. 79.22±3.1% at 10mg/ml with IC₅₀ value 2.84mg/ml. Other plant extracts showed mild in vitro macrofilaricidal activity. T. bellerica methanol extract exhibited significant GST activity of 18.86±0.21 and 12.83±0.03μM/ml/min at 5 and 10mg/ml with percentage inhibition value of 73.96% and 82.29% respectively. DEC showed GST activity value of 40.03±4.14 and 21.48±6.44μM/ml/min with percentage inhibition value of 21.76% and 58.01% at 5 and 10mg/ml respectively. Thus, methanol extract of leaves of T. bellerica exhibited highly significant antifilarial potential and needs detailed analysis.

Posttreatment Reactions After Single-Dose Diethylcarbamazine or Ivermectin in Subjects With Loa loa Infection

Background

Severe adverse reactions have been observed in individuals with Loa loa infection treated with either diethylcarbamazine (DEC), the drug of choice for loiasis, or ivermectin (IVM), which is used in mass drug administration programs for control of onchocerciasis and lymphatic filariasis in Africa. In this study, posttreatment clinical and immunologic reactions were compared following single-dose therapy with DEC or IVM to assess whether these reactions have the same underlying pathophysiology.

Methods

Twelve patients with loiasis and microfilarial counts <2000 mf/mL were randomized to receive single-dose DEC (8 mg/kg) or IVM (200 µg/kg). Clinical and laboratory assessments were performed at 4, 8, 24, 48, and 72 hours and 5, 7, 9, and 14 days posttreatment.

Results

Posttreatment adverse events were similar following DEC or IVM, but peaked earlier in subjects who received DEC, consistent with a trend toward more rapid and complete microfilarial clearance in the DEC group. After a transient rise (post-IVM) or fall (post-DEC) in the first 24 hours posttreatment, the eosinophil count rose significantly in both groups, peaking at day 5 in the DEC group and day 9 in the IVM group. Serum interleukin 5 levels and eosinophil activation, as assessed by surface expression of CD69 and serum levels of eosinophil granule proteins, were increased posttreatment in both groups.

Conclusions

Despite differences in eosinophil and lymphocyte counts during the first 24 hours posttreatment, the overall pattern of hematologic and immunologic changes suggest that posttreatment reactions following DEC and IVM share a common pathophysiology.

Clinical Trials Registration

NCT01593722.

Onchocerciasis in Yemen: Time to take action against a neglected tropical parasitic disease

Onchocerciasis is a neglected parasitic disease affecting the poorest underserved people in Yemen. A national control programme with goals to eliminate onchocerciasis has yet to be launched due to the current upheaval and social unrest in the country. The disease, locally termed as sowda, is unique in its clinicopathologic pattern, being of the localized, non-blinding, hyperreactive onchocercal skin disease. Although early reports identified endemic foci along seasonal watercourses, there is a need to redefine its epidemiologic patterns as well as health and socioeconomic impacts. Laboratory diagnosis of sowda among Yemeni patients is difficult due to the low load of microfilariae in skin snips and the presence of asymptomatic itching-free microfilaria carriers. Adoption of ivermectin use at three-month intervals as a control strategy has not been evaluated because the drug is mostly used in clinics and distributed to only a few affected communities. This paper addresses key aspects of onchocerciasis in Yemen and highlights the need for screening at-risk populations using highly sensitive techniques and mapping the distributions of the parasite in human and vector populations of blackflies. The new research should be integrated with the launch of a national onchocerciasis control programme to achieve onchocerciasis elimination.

Experimental Models to Study the Role of Microbes in Host-Parasite Interactions

Until recently, parasitic infections have been primarily studied as interactions between the parasite and the host, leaving out crucial players: microbes. The recent realization that microbes play key roles in the biology of all living organisms is not only challenging our understanding of host-parasite evolution, but it also provides new clues to develop new therapies and remediation strategies. In this paper we provide a review of promising and advanced experimental organismal systems to examine the dynamic of host-parasite-microbe interactions. We address the benefits of developing new experimental models appropriate to this new research area and identify systems that offer the best promises considering the nature of the interactions among hosts, parasites, and microbes. Based on these systems, we identify key criteria for selecting experimental models to elucidate the fundamental principles of these complex webs of interactions. It appears that no model is ideal and that complementary studies should be performed on different systems in order to understand the driving roles of microbes in host and parasite evolution.

Identification of Ecdysone Hormone Receptor Agonists as a Therapeutic Approach for Treating Filarial Infections

Background

A homologue of the ecdysone receptor has previously been identified in human filarial parasites. As the ecdysone receptor is not found in vertebrates, it and the regulatory pathways it controls represent attractive potential chemotherapeutic targets.

Methodology/ Principal Findings

Administration of 20-hydroxyecdysone to gerbils infected with B. malayi infective larvae disrupted their development to adult stage parasites. A stable mammalian cell line was created incorporating the B. malayi ecdysone receptor ligand-binding domain, its heterodimer partner and a secreted luciferase reporter in HEK293 cells. This was employed to screen a series of ecdysone agonist, identifying seven agonists active at sub-micromolar concentrations. A B. malayi ecdysone receptor ligand-binding domain was developed and used to study the ligand-receptor interactions of these agonists. An excellent correlation between the virtual screening results and the screening assay was observed. Based on both of these approaches, steroidal ecdysone agonists and the diacylhydrazine family of compounds were identified as a fruitful source of potential receptor agonists. In further confirmation of the modeling and screening results, Ponasterone A and Muristerone A, two compounds predicted to be strong ecdysone agonists stimulated expulsion of microfilaria and immature stages from adult parasites.

Conclusions

The studies validate the potential of the B. malayi ecdysone receptor as a drug target and provide a means to rapidly evaluate compounds for development of a new class of drugs against the human filarial parasites.

The human filarial parasites are the causative agents of two neglected tropical diseases targeted for elimination by the international community. The current elimination programs rely upon the mass distribution of a limited number of drugs, leaving the programs open to failure in the event that resistance develops. Thus, there is a critical need for novel chemotherapeutic agents to supplement the current arsenal. The filarial parasites are ecdysozoans, whose developmental processes are controlled by a master regulator, the ecdysone receptor. Here we validate the potential of the filarial ecdysone receptor as a chemotherapeutic target and report the development of high throughput and virtual screening assays that may be used to compounds that target it.

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.

Mansonella ozzardi: a neglected New World filarial nematode

Mansonella ozzardi (Nematoda: Onchocercidae) is an understudied filarial nematode, originally described by Patrick Manson in 1897, that can be transmitted by two families of dipteran vectors, biting midges (most of them members of the genus Culicoides) and black flies (genus Simulium). With a patchy geographic distribution from southern Mexico to northwestern Argentina, human infection with M. ozzardi is highly prevalent in some of the Caribbean islands, along riverine communities in the Amazon Basin, and on both sides of the border between Bolivia and Argentina. There is no clinical entity unequivocally associated with M. ozzardi infection, although fever, arthralgia, headache, cold lower extremities, and itchy cutaneous rashes are occasionally mentioned in case report series. More recently, ocular manifestations (especially keratitis) have been associated with mansonelliasis, opening an important area of investigation. Here, we briefly review the biology, epidemiology, pathogenesis, and clinical aspects of M. ozzardi infection and point to some existing knowledge gaps, aiming to stimulate a research agenda to help filling them.

Eosinophilia in Infectious Diseases

In determining the etiology of eosinophilia, it is necessary to consider the type of patient, including previous travel and exposure history, comorbidities, and symptoms. In this review, we discuss the approach to the patient with eosinophilia from an infectious diseases perspective based on symptom complexes.

Diagnosis of O. volvulus infection via skin exposure to diethylcarbamazine: clinical evaluation of a transdermal delivery technology-based patch

Background

Elimination of onchocerciasis in Africa is now regarded as an achievable goal in many areas. This makes monitoring changes in infection prevalence a key component of control programmes. Monitoring is currently based on determining the presence of O. volvulus microfilariae in skin snips, an invasive, labour-intensive method. The Onchocerciasis Control Programme (OCP) had established procedures to detect O. volvulus infections via the localized skin reaction induced by killing of microfilariae upon skin exposure to diethylcarbamazine via a patch (OCP-patch). Large scale OCP - patch use is difficult due to labour-intensive patch preparation. At the request of TDR, a manufacturer specialized in transdermal-delivery systems developed a ready-to-use diethylcarbamazine (DEC) containing patch (LTS-2 patch). To qualify this patch for large scale studies of its sensitivity and specificity, this study evaluated its ease of application, ability to detect infection and DEC exposure related adverse reactions compared to the OCP-patch in 30 infected individuals.

Methods

Each participant with 0.2–36.8 O. volvulus microfilariae/mg skin received the OCP-patch and 4 days later the LTS-2 patch at the left and right iliac crest, respectively, for 24 h. Presence and characteristics of local skin reactions were assessed at patch removal and 6 h later. Skin reaction and Mazzotti reaction rates were compared with Fisher’s exact and a paired t-test, respectively.

Results

The LTS-2 patch could be applied within 10 s. Mild itching occured at 63.3 % of OCP-patch (duration 8.9 ± 11.8 h) and 26.7 % of LTS-2 patch sites (duration 1.0 ± 2.5 h) and was the most frequent Mazzotti reaction. At patch removal after 24 h, a diagnostic local skin reaction was present under 90 % of OCP-patches and 83 % of LTS-2 patches; 6 h later, it was present at 93 % of OCP-patch and 100 % of LTS-2 patch sites.

Conclusions

The data suggest that safety, tolerability and ability to detect infections of the LTS-2 patch are comparable to those of the OCP-patch. They qualify the LTS-2 patch for field studies to determine LTS-2 patch sensitivity, specificity and utility during large scale use and thus to inform use of the LTS-2 patch by onchocerciasis control programmes to determine prevalence of infection.

Trial registration

Current controlled Trials ISRCTN76875372.

Targeting Filarial Abl-like Kinases: Orally Available, Food and Drug Administration-Approved Tyrosine Kinase Inhibitors Are Microfilaricidal and Macrofilaricidal

BACKGROUND

Elimination of onchocerciasis and lymphatic filariasis is targeted for 2020. Given the coincident Loa loa infections in Central Africa and the potential for drug resistance development, the need for new microfilaricides and macrofilaricides has never been greater. With the genomes of L. loa, Onchocerca volvulus, Wuchereria bancrofti, and Brugia malayi available, new drug targets have been identified.

METHODS

The effects of the tyrosine kinase inhibitors imatinib, nilotinib, and dasatinib on B. malayi adult males, adult females, L3 larvae, and microfilariae were assessed using a wide dose range (0-100 µM) in vitro.

RESULTS

For microfilariae, median inhibitory concentrations (IC50 values) on day 6 were 6.06 µM for imatinib, 3.72 µM for dasatinib, and 81.35 µM for nilotinib; for L3 larvae, 11.27 µM, 13.64 µM, and 70.98 µM, respectively; for adult males, 41.6 µM, 3.87 µM, and 68.22 µM, respectively; and for adult females, 42.89 µM, 9.8 µM, and >100 µM, respectively. Three-dimensional modeling suggests how these tyrosine kinase inhibitors bind and inhibit filarial protein activity.

CONCLUSIONS

Given the safety of imatinib in humans, plans are underway for pilot clinical trials to assess its efficacy in patients with filarial infections.

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.

A randomized, single-ascending-dose, ivermectin-controlled, double-blind study of moxidectin in Onchocerca volvulus infection

BACKGROUND

Control of onchocerciasis as a public health problem in Africa relies on annual mass ivermectin distribution. New tools are needed to achieve elimination of infection. This study determined in a small number of Onchocerca volvulus infected individuals whether moxidectin, a veterinary anthelminthic, is safe enough to administer it in a future large study to further characterize moxidectin's safety and efficacy. Effects on the parasite were also assessed.

METHODOLOGY/PRINCIPAL FINDINGS

Men and women from a forest area in South-eastern Ghana without ivermectin mass distribution received a single oral dose of 2 mg (N = 44), 4 mg (N = 45) or 8 mg (N = 38) moxidectin or 150 µg/kg ivermectin (N = 45) with 18 months follow up. All ivermectin and 97%-100% of moxidectin treated participants had Mazzotti reactions. Statistically significantly higher percentages of participants treated with 8 mg moxidectin than participants treated with ivermectin experienced pruritus (87% vs. 56%), rash (63% vs. 42%), increased pulse rate (61% vs. 36%) and decreased mean arterial pressure upon 2 minutes standing still after ≥5 minutes supine relative to pre-treatment (61% vs. 27%). These reactions resolved without treatment. In the 8 mg moxidectin and ivermectin arms, the mean±SD number of microfilariae/mg skin were 22.9±21.1 and 21.2±16.4 pre-treatment and 0.0±0.0 and 1.1±4.2 at nadir reached 1 and 3 months after treatment, respectively. At 6 months, values were 0.0±0.0 and 1.6±4.5, at 12 months 0.4±0.9 and 3.4±4.4 and at 18 months 1.8±3.3 and 4.0±4.8, respectively, in the 8 mg moxidectin and ivermectin arm. The reduction from pre-treatment values was significantly higher after 8 mg moxidectin than after ivermectin treatment throughout follow up (p<0.01).

CONCLUSIONS/SIGNIFICANCE

The 8 mg dose of moxidectin was safe enough to initiate the large study. Provided its results confirm those from this study, availability of moxidectin to control programmes could help them achieve onchocerciasis elimination objectives.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00300768.

Identification of variant ABC-transporter genes amongOnchocerca volvuluscollected from ivermectin-treated and untreated patients in Ghana, West Africa

Treatment with ivermectin (IVM) is known to cause a loss of polymorphism at certain loci of the beta-tubulin, gamma-aminobutyric-acid-receptor, glutamate-gated-chloride-channel and ATP-binding-cassette (ABC) transporter genes of IVM-resistant Haemonchus contortus. The genetic variation of four ABC-transporter homologues from Onchocerca volvulus was therefore investigated, to determine if any change in genetic polymorphism occurs in these genes following repeated treatment with IVM. Samples were collected in the Northern, Brong-Ahafo and Volta regions of Ghana, in 1999 and 2002; nodules containing adult O. volvulus were removed from subjects who had either received multiple IVM treatments or never taken IVM. The ATP-binding domains of four ABC-transporter genes (OvMDR-1, OvMDR-3, OvABC-1 and OvABC-6) were amplified from individual O. volvulus and examined for polymorphism, using single-strand-conformation-polymorphism (SSCP) analysis. In the samples collected in 1999, OvMDR-1 and OvABC-1 showed significant reduction in polymorphism following IVM treatment whereas OvABC-6 and OvMDR-3 were not found to be polymorphic. The samples collected in 2002 also showed a reduction in polymorphism for both OvMDR-1 and OvABC-1. Several single-nucleotide polymorphisms, which resulted in either amino-acid-replacement substitutions or nonsense mutations, were identified in the alleles of OvMDR-1 and OvABC-1.

Drug-induced uveitis

A number of medications have been associated with uveitis. This review highlights both well-established and recently reported systemic, topical, intraocular, and vaccine-associated causes of drug-induced uveitis, and assigns a quantitative score to each medication based upon criteria originally described by Naranjo and associates.

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.

Onchocerciasis: the role of Wolbachia bacterial endosymbionts in parasite biology, disease pathogenesis, and treatment

The discovery of Wolbachia intracellular bacteria within filarial nematodes, including Onchocerca volvulus, the causative agent of onchocerciasis or "river blindness," has delivered a paradigm shift in our understanding of the parasite's biology, to where we now know that the bacterial endosymbionts are essential for normal development of larvae and embryos and may support the long-term survival of adult worms. The apparent mutualistic dependency has also offered a novel approach to the treatment of onchocerciasis through the use of antibiotics to eliminate Wolbachia, delivering for the first time a treatment which has significant macrofilaricidal efficacy. Studies with other filarial nematode species have also highlighted a role for Wolbachia in transmission and infection of the mammalian host through a fascinating manipulation of mast cell-mediated vasodilation to enhance infectivity of vector-borne larvae. Wolbachia has also been identified as the principal driver of innate and adaptive Th1 inflammatory immunity, which can either contribute to disease pathogenesis or, with the Wolbachia-mediated recruitment of mast cells, enhance infectivity. The Wolbachia activation of innate inflammation also drives inflammatory adverse events in response to chemotherapy with either diethylcarbamazine (DEC) or ivermectin. In this review we summarize the experimental and field trial data which have uncovered the importance of Wolbachia symbiosis in onchocerciasis.

Ocular onchocerciasis: current management and future prospects

This paper reviews the current management of onchocerciasis and its future prospects. Onchocerciasis is a disease affecting millions of people in Africa, South and Central America, and Yemen. It is spread by the blackfly as a vector and caused by the filarial nematode, Onchocerca volvulus. A serious attempt was made by the Onchocerciasis Control Program between 1975 and 2002 to eliminate the vector in eleven of the endemic countries in West Africa, and with remarkable success. Formerly, the treatment was with diethyl carbamazine for the microfilaria and suramin for the adult worm. These drugs are now known to be toxic and unsuitable for mass distribution. In particular, they precipitate optic nerve disease. With the discovery of ivermectin, a much safer microfilaricide, and the decision of Merck to distribute the drug free of charge for as long as needed, the strategy of control switched to mass drug administration through community-directed treatment with ivermectin. So far, millions have received this annual or biannual treatment through the African Program for Onchocerciasis Control and the Onchocerciasis Elimination Program for the Americas. However, the problem with ivermectin is that it is a monotherapy microfilaricide which has limited effect on the adult worm, and thus will need to be continued for the life span of the adult worm, which may last up to 15 years. There are also early reports of resistance. Serious encephalopathy and death may occur when ivermectin is used in subjects heavily infested with loiasis. It seems unlikely that a break in transmission will occur with community-directed treatment with ivermectin in Africa because of population migrations and the highly efficient vector, but in the Americas some countries such as Columbia and the Oaxaca focus in Mexico have reported eradication. Vector control is only now applicable in selected situations, and particularly to control the nuisance value of the blackfly. Trials are ongoing for alternatives to ivermectin. Candidate drugs include moxidectin, a macrofilaricide, doxycycline which targets the Wolbachia endosymbiont, and flubendazole, which shows promise with the newer oral cyclodextrin formulation.

Description, mechanisms and control of reactions to treatment in the human filariases

Since diethylcarbamazine at the dosages used to treat filarial infections has little direct toxicity, most of the post-treatment reactions (termed Mazzotti reactions in onchocerciasis) result from the immunological inflammatory mechanisms activated in the process of clearing and killing the skin-swelling or blood-borne microfilariae. These reactions may be either localized to the skin, eyes or lymphatics or generalized systemically (e.g. headache, fever, adenopathy, arthralgia, tachypnoea, tachycardia, hypotension and even death). The occurrence and intensity of such reactions can be shown to be related to the intensity of infection. It had previously been speculated that the best candidates for triggering these post-treatment reactions were activation of complement, immediate hypersensitivity responses mediated by immunoglobulin E, and degranulation of eosinophils with resultant inflammatory reactivity. Recent detailed studies have given little support to the primacy of either complement or immediate hypersensitivity responses in triggering such reactions, but eosinophil degranulation with the release of inflammatory mediators into the tissues and peripheral blood is extremely prominent in all patients undergoing post-treatment reactions and develops with a time course generally consistent with what would be required of an initiator of such reactions. Other inflammatory mediators and pathways may be involved (e.g. kinins, prostaglandins, immune complexes, leukotrienes, platelets and parasite-derived inflammatory molecules), but there is currently no evidence to implicate any of these mechanisms as initiators of the response. Symptomatic treatment of these post-treatment reactions with analgesics, antipyretics, antihypotensive agents etc. has been successful, but their prevention has been achieved only with the broadly anti-inflammatory corticosteroids.

Some unsolved problems in the epidemiology of onchocerciasis

The descriptive epidemiology of onchocerciasis is well understood in the major foci of infection; a great stimulus to epidemiological research has been the implementation of the first control programme, which led to the eradication of infection in Kenya and, more recently, the vast Onchocerciasis Control Programme in the Volta River Basin of West Africa. However, there are still significant gaps in epidemiological knowledge which hamper the planning of future control programmes and the evaluation of current programmes. The four most important unsolved problems are: the refinement of field diagnostic techniques to identify skin microfilariae at the ultra-low densities that will become common in the late stages of vector-control campaigns; the definitive identification of Onchocerca volvulus infective larvae in Simulium species; strain analysis in the field of microfilariae from humans and of developing stages from Simulium, to determine their potential for ocular pathogenicity; determination of the lifespan, or maximum fecundity span, of adult female O. volvulus after the interruption of transmission. Three other unsolved problems are of enormous interest epidemiologically, although less urgent in practical importance. They are the identification of factors causing severe disease as opposed to heavy infection; the effects of seasonal as opposed to perennial transmission; and the importance of transplacental transmission of microfilariae or soluble antigens.

Mazzotti reaction after presumptive treatment for schistosomiasis and strongyloidiasis in a Liberian refugee

We report a case of the Mazzotti reaction in a 13-year-old Liberian refugee after presumptive treatment of schistosomiasis and strongyloidiasis with ivermectin, praziquantel and albendazole. The patient was hospitalized with fever, urticaria, abdominal pain and angioedema. Twelve hours after treatment with intravenous methylprednisolone he had complete resolution of his symptoms.

Lethal LPS-independent side effects after microfilaricidal treatment in Acanthocheilonema viteae-infected rodents

Mastomys coucha and jirds infected with Acanthocheilonema viteae, a filarial species free of endosymbiontic bacteria of the genus Wolbachia, suffer lethal side effects after effective microfilaricidal therapy with diethylcarbamazine and levamisole, whereas, M. coucha infected with the Wolbachia-infested species Brugia malayi or Litomosoides carinii tolerate corresponding treatment. Mortality in A. viteae infected, treated animals varied with microfilariae density in the blood. It was up to 100% in highly microfilaraemic M. coucha and jirds, but low or absent in animals with low microfilariae counts. Deaths occurred in most cases 5-24 h after treatment. Characteristic symptoms in animals, which died subsequently were a rapid drop in body temperature by 4-7 degrees C, an increase in hematokrit values by up to 10% and a moderate blood acidosis. Lethal effects in A. viteae infections did not depend on a particular status of hypersensitivity of the animals since desensitization procedures, which protected infected M. coucha against an otherwise lethal intravenous challenge with A. viteae homogenate did not protect against adverse reactions to a subsequent microfilaricidal treatment. The animals were protected from treatment induced death by injection of N-LMMA. Thus the final morbific agent seems NO. The data show that adverse effects after effective microfilaricidal therapy may be caused by microfilariae derived components different from Wolbachia-released LPS.

Pharmacology of ivermectin

Ivermectin is a semi-synthetic macrocyclic lactone (Fig. I) active in single low doses against many parasites - particularly nematodes and arthropods. It has been registered for animal health use since early 1985, and was earlier this year approved for human use by the French Directorate o f Pharmacy and Drugs. Of particular interest is ivermectin's potential as a micro filaricide for treatment o f onchocerciasis. Clinical trials leave little doubt about the potential o f ivermectin as a therapeutic tool for symptomatic relief from the effects o f infection with Onchocerca volvulus, and the drug is also recognized to have potential in reducing transmission o f the parasite. The manufacturers (Merck, Sharp and Dohme) recently arranged to provide the drug free o f charge to the WHO for mass trials against onchocerciasis in 12 African and Central American countries. In this article we focus on the pharmacological properties o f ivermectin, with a brief consideration of its absorption, fate, excretion and side-effects, and a discussion o f its micro filaricidal action.

The Wolbachia genome of Brugia malayi: endosymbiont evolution within a human pathogenic nematode

Complete genome DNA sequence and analysis is presented for Wolbachia, the obligate alpha-proteobacterial endosymbiont required for fertility and survival of the human filarial parasitic nematode Brugia malayi. Although, quantitatively, the genome is even more degraded than those of closely related Rickettsia species, Wolbachia has retained more intact metabolic pathways. The ability to provide riboflavin, flavin adenine dinucleotide, heme, and nucleotides is likely to be Wolbachia's principal contribution to the mutualistic relationship, whereas the host nematode likely supplies amino acids required for Wolbachia growth. Genome comparison of the Wolbachia endosymbiont of B. malayi (wBm) with the Wolbachia endosymbiont of Drosophila melanogaster (wMel) shows that they share similar metabolic trends, although their genomes show a high degree of genome shuffling. In contrast to wMel, wBm contains no prophage and has a reduced level of repeated DNA. Both Wolbachia have lost a considerable number of membrane biogenesis genes that apparently make them unable to synthesize lipid A, the usual component of proteobacterial membranes. However, differences in their peptidoglycan structures may reflect the mutualistic lifestyle of wBm in contrast to the parasitic lifestyle of wMel. The smaller genome size of wBm, relative to wMel, may reflect the loss of genes required for infecting host cells and avoiding host defense systems. Analysis of this first sequenced endosymbiont genome from a filarial nematode provides insight into endosymbiont evolution and additionally provides new potential targets for elimination of cutaneous and lymphatic human filarial disease.

Analysis of this Wolbachia genome, which resides within filarial parasites, offers insight into endosymbiont evolution and the promise of new strategies for the elimination of human filarial disease