Changes in visual function and in the posterior segment of the eye during treatment of onchocerciasis with diethylcarbamazine citrate

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.

Presumed Onchocerciasis Chorioretinitis Spilling over into North America, Europe and Middle East

BACKGROUND

Newer generation ophthalmologists practicing in the developed world are not very familiar with some tropical ocular diseases due to the absence of reports in the ophthalmic literature over the past thirty years. Because of world globalization or due to influx of immigrants from sub-Saharan Africa, exotic retinal diseases are being encountered more often in ophthalmology clinics.

METHODS

A multicenter case series of chorioretinitis or optic neuritis with obscure etiology that used serial multimodal imaging.

RESULTS

Four cases qualified with the diagnosis of presumed ocular onchocerciasis based on their residence near fast rivers in endemic areas, multimodal imaging, long term follow-up showing progressive disease and negative workup for other diseases. Characteristic findings include peripapillary choroiditis with optic neuritis or atrophy, subretinal tracts of the microfilaria, progressive RPE atrophy around heavily pigmented multifocal chorioretinal lesions of varying shapes, subretinal white or crystalline dots, and response to ivermectin. Typical skin findings are often absent in such patients with chorioretinitis rendering the diagnosis more challenging.

CONCLUSIONS

Familiarity with the myriad ocular findings of onchocerciasis, and a high-degree of suspicion in subjects residing in endemic areas can help in the correct diagnosis and implementation of appropriate therapy. Onchocercal chorioretinitis is a slow, insidious, progressive, and prolonged polymorphous disease.

Challenges in posterior uveitis-tips and tricks for the retina specialist

PURPOSE

Posterior uveitis is a common chorioretinal pathology affecting all ages worldwide and is a frequent reason for referral to the retina clinic. The spectrum of etiologies for uveitis is very broad and includes infectious and auto-immune diseases. Inflammation can be confined to the eye or may be a part of systemic disease. A useful outline is therefore proposed to aid in the correct diagnosis of these challenging entities. The situation is further complicated by the fact that many neoplastic conditions resemble features of posterior uveitis; they are known as "masqueraders of uveitis". Here, we summarize different posterior uveitides that present with rare findings, along with masqueraders that can be difficult to distinguish. These conditions pose a diagnostic dilemma resulting in delay in treatment because of diagnostic uncertainty.

METHODS

An extensive literature search was performed on the MEDLINE/PUBMED, EBSCO and Cochrane CENTRAL databases from January 1985 to January 2022 for original studies and reviews of predetermined diagnoses that include posterior uveitic entities, panuveitis and masquerade syndromes.

RESULTS

We described conditions that can present as mimickers of posterior uveitis (i.e., immune check-points inhibitors and Vogt-Koyanagi-Harada-like uveitis; leukemia and lymphoma associated posterior uveitis), inflammatory conditions that present as mimickers of retinal diseases (i.e., Purtscher-like retinopathy as a presentation of systemic lupus erythematosus; central serous chorioretinopathy masquerading inflammatory exudative retinal detachment), and uveitic conditions with rare and diagnostically challenging etiologies (i.e., paradoxical inflammatory effects of anti-TNF-α; post vaccination uveitis; ocular inflammation after intravitreal injection of antiangiogenic drugs).

CONCLUSION

This review of unique posterior uveitis cases highlights the overlapping features of posterior uveitis (paradoxical inflammatory effects of anti -TNF α and uveitis; Purtscher-like retinopathy as a presentation of systemic lupus erythematosus, …) and the nature of retinal conditions (ischemic ocular syndrome, or central retinal vein occlusion, amyloidosis, inherited conditions like retinitis pigmentosa, autosomal dominant neovascular inflammatory vitreoretinopathy (ADNIV), etc.…) that may mimic them is represented. Careful review of past uveitis history, current medications and recent vaccinations, detailed examination of signs of past or present inflammation, eventually genetic testing and/ or multimodal retinal imaging (like fluorescein angiography, EDI-OCT, OCT-angiography for lupus Purtscher-like retinopathy evaluation, or ICG for central serous retinopathy, or retinal amyloid angiopathy) may aid in correct diagnosis.

Diethylcarbamazine, TRP channels and Ca2+ signaling in cells of the Ascaris intestine

The nematode parasite intestine absorbs nutrients, is involved in innate immunity, can metabolize xenobiotics and as we show here, is also a site of action of the anthelmintic, diethylcarbamazine. Diethylcarbamazine (DEC) is used to treat lymphatic filariasis and activates TRP-2, GON-2 & CED-11 TRP channels in Brugia malayi muscle cells producing spastic paralysis. DEC also has stimulatory effects on ascarid nematode parasites. Using PCR techniques, we detected, in Ascaris suum intestine, message for: Asu-trp-2, Asu-gon-2, Asu-ced-11, Asu-ocr-1, Asu-osm-9 and Asu-trpa-1. Comparison of amino-acid sequences of the TRP channels of B. malayi, and A. suum revealed noteworthy similarity, suggesting that the intestine of Ascaris will also be sensitive to DEC. We used Fluo-3AM as a Ca2+ indicator and observed characteristic unsteady time-dependent increases in the Ca2+ signal in the intestine in response to DEC. Application of La3+ and the TRP channel inhibitors, 2-APB or SKF 96365, inhibited DEC mediated increases in intracellular Ca2+. These observations are important because they emphasize that the nematode intestine, in addition to muscle, is a site of action of DEC as well as other anthelmintics. DEC may also enhance the Ca2+ toxicity effects of other anthelmintics acting on the intestine or, increase the effects of other anthelmintics that are metabolized and excreted by the nematode intestine.

Anti-Wolbachia drugs for filariasis

The mutualistic association between Wolbachia endosymbionts and their filarial nematode hosts has been exploited as a validated drug target delivering macrofilaricidal outcomes. Limitations of existing antibiotics to scale-up have driven the search for new drugs, which are effective in shorter regimens of 7 days or less. Here, we review the last 14 years of anti-Wolbachia drug discovery by the anti-Wolbachia (A·WOL) consortium, which has screened more than two million compounds, delivering thousands of hit compounds. Refined screening models integrated with robust pharmacokinetic/pharmacodynamic (PK/PD) driven optimisation and selection strategies have delivered the first two drug candidates specifically designed to target Wolbachia. AWZ1066S and ABBV-4083 are currently progressing through clinical trials with the aim of delivering safe and effective macrofilaricides to support the elimination of onchocerciasis and lymphatic filariasis.

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.

Diethylcarbamazine activates TRP channels including TRP-2 in filaria, Brugia malayi

Diethylcarbamazine is an important classic drug used for prevention and treatment of lymphatic filariasis and loiasis, diseases caused by filarial nematodes. Despite many studies, its site of action has not been established. Until now, the consensus has been that diethylcarbamazine works by activating host immune systems, not by a direct action on the parasites. Here we show that low concentrations of diethylcarbamazine have direct and rapid (<30 s) temporary spastic paralyzing effects on the parasites that lasts around 4 h, which is produced by diethylcarbamazine opening TRP channels in muscle of Brugia malayi involving TRP-2 (TRPC-like channel subunits). GON-2 and CED-11, TRPM-like channel subunits, also contributed to diethylcarbamazine responses. Opening of these TRP channels produces contraction and subsequent activation of calcium-dependent SLO-1K channels. Recovery from the temporary paralysis is consistent with inactivation of TRP channels. Our observations elucidate mechanisms for the rapid onset and short-lasting therapeutic actions of diethylcarbamazine.

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.

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.

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.

Drug-induced uveitis

INTRODUCTION

Drug-induced uveitis is a well described but often overlooked and/or misdiagnosed adverse reaction to medication. There are an increasing number of medications that have been related to the onset of intraocular inflammation. Identification of these inciting agents may decisively help the diagnostic algorithm involving new cases of uveitis.

AREAS COVERED

This review intends to be an updated comprehensive, practical guide for practitioners regarding the main drugs that have been associated with uveitis. A classification proposed by Naranjo et al. in 1981 for establishing potential causality is applied examining possible mechanisms of action. A guide for clinicians about the rationale of these observations when dealing with patients with uveitis is provided.

EXPERT OPINION

Several agents with different routes of administration (systemic, topical and/or intraocular) may cause intraocular inflammation. The mechanism behind ocular inflammation is frequently unknown. Clinicians should be aware of the potential drug effect to optimize diagnosis and management of such patients.

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.

Ivermectin for onchocercal eye disease (river blindness)

BACKGROUND

It is believed that ivermectin (a microfilaricide) could prevent blindness due to onchocerciasis. However, when given to everyone in communities where onchocerciasis is common, the effects of ivermectin on lesions affecting the eye are uncertain and data on whether the drug prevents visual loss are unclear.

OBJECTIVES

The aim of this review was to assess the effectiveness of ivermectin in preventing visual impairment and visual field loss in onchocercal eye disease. The secondary aim was to assess the effects of ivermectin on lesions affecting the eye in onchocerciasis.

SEARCH METHODS

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 3), MEDLINE (January 1950 to April 2012), EMBASE (January 1980 to April 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 2 April 2012.

SELECTION CRITERIA

We included randomised controlled trials with at least one year of follow-up comparing ivermectin with placebo or no treatment. Participants in the trials were people normally resident in endemic onchocercal communities with or without one or more characteristic signs of ocular onchocerciasis.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality. We contacted study authors for additional information. As trials varied in design and setting, we were unable to perform a meta-analysis.

MAIN RESULTS

The review included four trials: two small studies (n = 398) in which people with onchocercal infection were given one dose of ivermectin or placebo and followed up for one year; and two larger community-based studies (n = 4941) whereby all individuals in selected communities were treated every six or 12 months with ivermectin or placebo, whether or not they were infected, and followed for two to three years. The studies provide evidence that treating people who have onchocerciasis with ivermectin reduces the number of microfilariae in their skin and eye(s) and reduces the number of punctate opacities. There was weaker evidence that ivermectin reduced the risk of chorioretinitis. The studies were too small and of too short a duration to provide evidence for an effect on sclerosing keratitis, iridocyclitis, optic nerve disease or visual loss. One community-based study in communities mesoendemic for the savannah strain of O.volvulus provided evidence that annual mass treatment with ivermectin reduces the risk of new cases of optic nerve disease and visual field loss. The other community-based study of mass biannual treatment of ivermectin in communities affected by the forest strain of O.volvulus demonstrated reductions in microfilarial load, punctate keratitis and iridocyclitis but not sclerosing keratitis, chorioretinitis, optic atrophy or visual impairment. The study was underpowered to estimate the effect of ivermectin on visual impairment and other less frequent clinical signs. The studies included in this review reported some adverse effects, in particular an increased risk of postural hypotension in people treated with ivermectin.

AUTHORS' CONCLUSIONS

The lack of evidence for prevention of visual impairment and blindness should not be interpreted to mean that ivermectin is not effective, however, clearly this is a key question that remains unanswered. The main evidence for a protective effect of mass treatment with ivermectin on visual field loss and optic nerve disease comes from communities mesoendemic for the savannah strain of O.volvulus. Whether these findings can be applied to communities with different endemicity and affected by the forest strain is unclear. Serious adverse effects were rarely reported. None of the studies, however, were conducted in areas where people are infected with Loa loa (loiasis).

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.

A randomized, double-blind, controlled trial of the effects of ivermectin at normal and high doses, given annually or three-monthly, against Onchocerca volvulus: ophthalmological results

A three-year randomized, controlled, double-blind trial was conducted in Cameroon to determine whether ivermectin, given at three-monthly intervals and/or at high doses (800 microg/kg), had a greater effect on adult Onchocerca volvulus than standard doses (150 microg/kg annually). As several patients complained of transitory subjective visual problems after treatment, some of them being of an unexpected type, we organized two series of detailed ophthalmological examinations to evaluate whether they were associated with ocular lesions. Analysis showed that these complaints were significantly more frequent in the two groups treated with high doses of ivermectin than in the reference group. In the ophthalmological examinations, the only differences recorded between the groups were a lower prevalence and mean number of microfilariae in the anterior chamber in the groups treated three-monthly, and, at the first examination round, a higher prevalence of early lesions of the iris in the group treated at high doses annually. These findings do not allow us to explain the cause of the transitory ocular complaints, nor why they were more frequent in the groups treated at high doses. However, one may conclude that using doses of ivermectin higher than the standard one should be considered with caution.

The pathogenesis of chorioretinal disease in onchocerciasis

The pathogenesis of onchocercal chorioretinopathy is poorly understood. In this article, Philip Cooper, Ronald Guderian, Roberto Proaño and David Taylor discuss the important clinical, histological and epidemiological features of the resulting lesions that cause blindness, and review the numerous mechanisins that have been put forward to explain its pathogenesis. The pathogenesis of anterior segment disease, particulary sclerosing keratitis, has been reviewed in depth previously(1) and will not be discussed here.

Clinical picture and outcome of Serious Adverse Events in the treatment of Onchocerciasis

Ivermectin (Mectizan^®) is the only drug currently recommended for the treatment and control of onchocerciasis. Serious adverse events rarely occur during treatment, except in subjects heavily infected with Loa Loa. This review of drug-related serious adverse events in the treatment of onchocerciasis therefore revisited the pre-Mectizan^® reference drugs, DEC and suramin, and other candidate drugs studied extensively for the treatment of human onchocerciasis. The benzimidazole carbamate derivatives and the antibiotic doxycycline were excluded, since no serious adverse events have been reported regarding their use. Using recommended definitions, serious adverse events reported or observed after the use of each drug were summarised, the level of attribution determined, and the results tabulated. Prominence was given to treatment-related deaths. The clinical picture of severe symptomatic postural hypotension is described and used to illustrate the difference between the severity and the seriousness of an adverse event. The epidemiology, management and outcome of serious adverse events are presented. The role of future research is discussed.

Ivermectin for onchocercal eye disease (river blindness)

BACKGROUND

It is believed that ivermectin (a microfilaricide) could prevent blindness due to onchocerciasis. However, when given to everyone in communities where onchocerciasis is common, the effects of ivermectin on lesions affecting the eye are uncertain and data on whether the drug prevents visual loss is unclear.

OBJECTIVES

The aim of this review is to assess the effectiveness of ivermectin in preventing visual acuity and visual field loss in onchocercal eye disease. The secondary aim is to assess the effects of ivermectin on lesions affecting the eye in onchocerciasis.

SEARCH STRATEGY

We searched the Cochrane Eyes and Vision Group specialised register, the Cochrane Controlled Trials Register - CENTRAL, MEDLINE, EMBASE, the reference lists of identified trials, the Science Citation Index and we contacted investigators, experts and pharmaceutical companies to identify additional trials.

SELECTION CRITERIA

We included randomised controlled trials with at least one year follow up, comparing ivermectin at a dose of 150 micrograms per kilogram of body weight with either placebo or no treatment. Participants were people normally resident in endemic onchocercal communities with or without one or more characteristic signs of ocular onchocerciasis.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed trial quality. Study authors were contacted for additional information. Trials varied in design and setting, so no meta-analysis was done.

MAIN RESULTS

This review includes five trials with data from 3810 participants. All the trials compared ivermectin with placebo and were judged to be of moderate risk of bias in terms of methodological quality. No statistically significant difference was observed in any trial (reporting visual acuity outcome) between ivermectin and placebo groups for visual acuity loss.

REVIEWER'S CONCLUSIONS

Questions about the effectiveness of ivermectin in preventing visual acuity loss have not been answered by best available evidence.

Tolerance to diethylcarbamazine-medicated salt in individuals infected with Onchocerca volvulus

The tolerance of Onchocerca volvulus-infected individuals to diethylcarbamazine (DEC)-medicated salt (0.33% w/w) was assessed in 1996 in Tanzania in a double-blind placebo-controlled hospital-based trial involving 4 groups, each of 10 adult males. Groups I and II had O. volvulus microfilariae (mf) only, group III had both O. volvulus and Wuchereria bancrofti mf, and group IV had W. bancrofti mf only. Groups I, III and IV received DEC-medicated salt, whereas group II was a control to group I and received normal cooking salt. Medication was given for 10 days. The most pronounced adverse reactions in groups I and III were mild-to-moderate itching and rash, beginning after 3-4 days and lasting for the remaining medication period. The reactions did not interfere with normal daily activities. By 20 days after the end of medication, adverse reactions had disappeared in all individuals. The low daily dose of DEC had no significant effect on the O. volvulus pre-medication mf geometric mean intensities (GMIs). In contrast, the medication significantly reduced the pre-medication W. bancrofti mf GMIs. The prospects for using DEC-medicated salt for control of bancroftian filariasis in areas where incidental infections with O. volvulus occur are discussed.

Blue-yellow colour vision in an onchocercal area of northern Nigeria

AIM

To determine if the City University Tritan Test is a useful addition to visual function assessment in rural communities in northern Nigeria.

METHODS

The study was a cross sectional survey. The participants were 8394 people, aged 5 years and over, living in 37 rural communities, mesoendemic and nonendemic for onchocerciasis, in Kaduna State in northern Nigeria. The main outcome measures were the detection of a defect in blue-yellow colour vision by two criteria: (1) failure with the City University tritan screening plates; (2) failure with the City University grading plates to identify severe tritan defects.

RESULTS

91% of those aged 10 years and above could perform the test. Below this age, there were difficulties in comprehension. The test showed good inter- and intraobserver agreement. After adjustment for confounders the odds of failing the screening plates were significantly increased in the presence of optic atrophy or glaucoma (3.55 (2.48-5.08) and 15.9 (4.22-60.2) respectively). There was a greater increase in the adjusted odds of failing the grading plates in the presence of optic atrophy or glaucoma (5.30 (2.97-9.45) and 8.87 (1.61-48.7) respectively). Cataract had a smaller effect on the screening plates, adjusted odds 1.63 (0.95-2.80).

CONCLUSION

Blue-yellow colour vision testing is a useful addition to visual function assessment in those aged 10 years and above in rural northern Nigeria, particularly in the detection of optic nerve disease.

The effects of multiple doses of ivermectin on ocular onchocerciasis. A six-year follow-up

BACKGROUND

Ivermectin has been shown to be a safe treatment for onchocerciasis and is now being distributed through mass treatment programs. Previous studies of up to 3 years of treatment have demonstrated that ivermectin improves anterior segment lesions and reduces the incidence of optic atrophy. The benefit of multiple doses of ivermectin on visual acuity and chorioretinitis has yet to be shown.

METHODS

A community-based, double-blind, randomized, controlled trial of ivermectin was started in Bo, Sierra Leone, in 1987. Two cohorts are reported in this study: (1) 214 subjects had received four 6-month doses of ivermectin followed by up to six additional 6-month treatments. The second cohort, with 185 subjects, had received four 6-month doses of placebo followed by up to four annual doses of ivermectin. All subjects received a full ophthalmic examination in 1989 and again in 1994. For both cohorts, there was an 18-month gap between the fifth and sixth rounds of treatment.

RESULTS

There was no significant difference in the prevalences of any ocular lesion nor of visual acuity categories between the cohorts at the second examination. Comparisons of the prevalences of anterior segment lesions for both cohorts combined between the first and second examinations show highly significant improvement (P < 0.001) for all lesions. Posterior segment lesions show a more variable pattern, with chorioretinitis showing highly significant deterioration (P < 0.001) and the emergence of new lesions in both groups.

CONCLUSION

The authors conclude that annual treatment with ivermectin is effective in controlling ocular onchocerciasis apart from chorioretinal lesions and that a 6-month treatment gives no additional benefit.

Onchocerciasis in Ecuador: evolution of chorioretinopathy after amocarzine treatment

AIMS

To investigate the impact of the macrofilaricidal drug, amocarzine, on the evolution of chorioretinopathy in onchocerciasis.

METHODS

A prospective uncontrolled cohort study was performed using subjects infected with Onchocerca volvulus in a hyperendemic onchocerciasis focus in Esmeraldas Province in Ecuador. Study subjects were recruited into four cohorts in which ophthalmic and parasitological data were collected for 2, 3, 4, and 5 years respectively.

RESULTS

Complete ophthalmic follow up was obtained for 294 individuals in the four cohorts. The incidence of retinal pigment epithelial atrophy tended to remain constant between cohorts while that of chorioretinal scarring with a greater observation period. The incidence rate of cases with new or extending chorioretinal lesions was greater with an increasing period of follow up. An association was seen between the cumulative microfilarial loads in the skin and the development of new chorioretinal lesions (p < 0.05). No relation was noted between cumulative microfilarial loads and the progression of existing disease.

CONCLUSION

Amocarzine therapy did not prevent the natural evolution of chorioretinal disease. It was suggested that ocular microfilariae were necessary for the induction of chorioretinopathy in previously unaffected eyes and that extension of existing disease might also be related to the presence of ocular microfilariae or to other immunological mechanisms.

Ivermectin and onchocercal optic neuritis: short-term effects

In 1982 the macrocyclic lactone, ivermectin, was first tested in human patients with onchocerciasis. It has since undergone phase I to IV trials and is now being widely distributed in onchocercal areas. The previous microfilaricide, diethylcarbamazine citrate (DEC), is known to precipitate or exacerbate active optic neuritis in some onchocercal patients, as part of a wider inflammatory response (the Mazzotti reaction). Ivermectin may also cause a mild reaction, especially in people with high microfilarial loads. Few data are available concerning the effect of ivermectin on active optic neuritis. A large, randomised, double-masked, phase IV trial is reported. Individuals were screened for evidence of optic nerve disease (OND), and those identified as possible cases of OND underwent detailed ophthalmic examination, including fluorescein angiography, before being dosed with ivermectin or placebo. A total of 6831 persons were screened of whom 856 (13%) underwent angiography prior to dosing. At 7-14 days after dosing an attempt was made to re-examine 50% of adults over the age of 20 years, including all those with OND. Six hundred and eighty-eight repeat or new angiograms were performed. During this period, 5 new cases of active optic neuritis and one case of exacerbation of existing optic neuritis were identified. Five of these individuals had received placebo and one ivermectin. Two individuals with optic neuritis before dosing had improved after 7-14 days. One had received placebo, the other ivermectin. Ivermectin does not appear to precipitate or exacerbate optic neuritis at a period of 7-14 days.

Reduction in incidence of optic nerve disease with annual ivermectin to control onchocerciasis

The safety and efficacy of ivermectin in the prevention of blindness from onchocerciasis have been established in many studies that have addressed the drug's effects on the front of the eye. We undertook a study with sufficient statistical power to detect an effect on optic nerve disease (OND), probably the main cause of blindness in the disorder. The trial was based in 34 mesoendemic communities in Kaduna State, Nigeria. Villagers aged 5 years and older were randomly assigned annual dosing with ivermectin or placebo for 3 years. Participants underwent medical and ophthalmological examinations before the first, third, and fourth treatments. 3522 villagers aged 15 and older were re-examined at least once. Skin-snip samples were taken at baseline for calculation of microfilarial load. The outcome measure was development of disc pallor accompanied by objective evidence of deterioration in visual function; 116 subjects (45 ivermectin-treated, 71 placebo-treated) showed such changes during the trial. The incidence rate ratio (ivermectin vs placebo) was 0.90 (95% CI 0.54-1.51) for subjects with loads of 0-10 mf (microfilariae) per mg skin and 0.52 (0.29-0.93) for subjects with more than 10 mf/mg. The incidence rate ratio varied little when account was taken of age, sex, presence of pre-existing disc pallor in one eye, previous use of diethylcarbamazine citrate, or doses of ivermectin or placebo received. There was evidence that ivermectin reduced the incidence of OND in subjects with microfilarial loads above 10 mf/mg but had little effect in those with lower loads. Sustained annual delivery of ivermectin could prevent a substantial proportion of onchocercal blindness in mesoendemic communities.

Quantification of the ocular reactions to microfilaricides in the chemotherapy of onchocerciasis

Severe adverse systemic and ocular reactions have complicated the chemotherapy of onchocerciasis. A method for the quantification of ocular reactions to chemotherapy has been devised at the Onchocerciasis Chemotherapy Research Centre, at Hohoe, in Ghana. Symptoms, visual function, anterior segment inflammation and disease of the posterior segment are graded. The information is entered into a computerised database which allows reaction scores to be calculated both for individual patients, and for treatment groups. This system enables comparison of adverse ocular reactions to various new chemotherapeutic regimens.

Immunological crossreactivity between a cloned antigen of Onchocerca volvulus and a component of the retinal pigment epithelium

Onchocerciasis (river blindness) is a major blinding disease in Africa, Central America, and South America. Loss of vision can be due to corneal change, optic atrophy, or chorioretinal disease. It has been suggested that autoimmunological reactions resulting from crossreactivity between parasite antigens and components of eye tissues contribute to development of ocular pathology. Using sera collected from onchocerciasis patients as a screening reagent, a cDNA clone (Ov39) has been isolated from a lambda gt11 expression library of Onchocerca volvulus. This antigen exhibits immunological crossreactivity with a component of retinal pigment epithelium cells (RPE). Antiserum raised against this recombinant peptide immunoprecipitates a 22,000 Mr antigen of adult O. volvulus and recognizes a 44,000 Mr component of bovine RPE by Western blotting. A 44,000 Mr antigen of cultured human RPE metabolically labeled with 35S-methionine can be immunoprecipitated with the same antiserum. An antigen of the same size is recognized by a rabbit antiserum raised against whole O. volvulus extract. Immunocytochemical studies on cryostat sections of the bovine eye using the antirecombinant sera localizes this antigen to the RPE.

Decrease in adverse reactions after repeated ivermectin treatment in onchocerciasis

We assessed the side-effects after multiple single-dose treatment with ivermectin (150 micrograms/kg) in onchocerciasis patients form a hyperendemic area in Sierra Leone, in order to investigate whether medical surveillance was always necessary. After initial treatment 87 onchocerciasis patients were examined for adverse reactions. Fourty-four of these 87 patients (51%) received a second dose of ivermectin 5 months later and thirty-five (40%) received a third dose one year later. The side-effects after the second and third doses were significantly diminished, when compared with the initial dose of ivermectin in the treatment of onchocerciasis (chi2 test p less than 0.005, resp. p less than 0.008). Side-effects requiring therapy were observed in 32% of patients after the first dose, in 18% after the second dose and in 11% after the third dose of ivermectin. Severe side-effects (9%) were only seen after the initial ivermectin dose. All the severe adverse reactions appeared within 48 hours. In view of our findings, it seems necessary that the first treatment with ivermectin should take place under strict medical supervision during at least two days. Five months after treatment with a single dose of ivermectin 29 out of 44 patients (66%) still had a positive skin-snip test. Seven months after the second dose 15 of 35 patients (43%) had a positive skin-snip count. Since almost half of the patients had a positive skin-snip test despite two treatments with ivermectin, it could be argued that in hyperendemic areas treatment should consist of at least two doses in the first year.

Ocular involvement in patients with onchocerciasis after repeated treatment with ivermectin

We assessed ocular changes after therapy at six and 12 months with ivermectin (150 micrograms/kg of body weight) in a 12-month prospective study of 29 patients with ocular onchocerciasis and 15 patients with onchocerciasis without ocular involvement. The patients lived in a hyperendemic area in Sierra Leone, West Africa, where no vector control was instituted. Five months after initial treatment, the microfilarial load in skin and eyes had decreased significantly (P less than .0000), but 28 of 44 (63%) patients had positive skin-snip test results and nine of 29 (31%) patients with ocular involvement had active ocular disease. Twelve months after initial treatment, 15 of 41 (37%) patients had positive skin-snip test results and eight of 26 (31%) showed active ocular involvement. All patients with persistent ocular disease after therapy showed evidence of active onchocerciasis at that time, which suggests that a dose of ivermectin at six-month intervals is not sufficient for intensely infested patients with severe ocular disease. We developed an ocular involvement score to evaluate the patient's total ocular status and observed a significant relation between the pretreatment severity of ocular involvement and the persistence of active ocular disease after treatment with ivermectin.

Ivermectin treatment of onchocerciasis

Ivermectin is a recently developed macrocyclic lactone that has widespread antiparasitic activity. A series of clinical trials has shown that ivermectin is safe and effective in the treatment of human infection with Onchocerca volvulus. Although it is rapidly microfilaricidal, it does not cause a severe reaction as is seen with diethylcarbamazine treatment. The drug also temporarily interrupts production of microfilaria but has no known long-lasting effects on the adult worms. In patients with onchocerciasis, a single oral dose of ivermectin (150 micrograms/kg) repeated once a year leads to a marked reduction in skin microfilaria counts and ocular involvement. At this dose, ivermectin causes minimal side effects and appears to be sufficiently free of severe adverse reactions to be used on a mass scale. Its use promises to revolutionise the treatment of onchocerciasis.

Side-effects of ivermectin in treatment of onchocerciasis

In a prospective study to determine the tolerance for and safety of ivermectin therapy for onchocerciasis in a hyperendemic area in Sierra Leone, 28 (32%) of 87 patients had adverse reactions that required treatment with acetylsalicylic acid and antihistamines, but none of the observed adverse reactions were considered life-threatening. A significant relation was found between the frequency and severity of side-effects and the degree of parasite infestation, as quantified by the skin-snip counts. Free administration of ivermectin to severely infected onchocerciasis patients is not recommended without some form of medical supervision.

Effect of single-dose ivermectin therapy on human Onchocerca volvulus infection with onchocercal ocular involvement

Ivermectin has shown promise as a potentially safe and effective microfilaricidal drug for the treatment of onchocerciasis. Several limited studies have shown it to have fewer side effects, especially ocular complications, than the currently available drug, diethylcarbamazine. The detailed ocular findings in 200 moderately to heavily infected Liberians who were enrolled in a safety and dose-finding study are presented. They received either 0, 100, 150, or 200 micrograms/kg of ivermectin and were followed up for 12 months. In clinical studies so far carried out ivermectin in a dose of 100, 150, or 200 micrograms/kg has not been associated with any major adverse reactions nor were there any sight-threatening effects even in the presence of severe ocular disease. Each of these doses significantly reduced the ocular microfilaria load for at least 12 months when compared with either the placebo (p less than 0.05) or pretreatment values (p less than 0.001). However, the 100 and 150 micrograms/kg doses caused fewer minor side effects than the higher dose. These results confirm that ivermectin in a single oral dose may be a safe and effective microfilaricidal drug for the treatment of onchocerciasis and that it appears to be free of major ocular side effects.

Avoidable blindness

The vast majority of the world's 42 million blind are needlessly impaired. Epidemiologic studies are providing important insights into the cause of cataracts and provision of surgical services; ecologic approaches to the control of trachomatous corneal scarring; treatment and prevention of onchocerciasis; and early diagnosis and treatment of xerophthalmia among others. Continued research and application of existing knowledge can have a dramatic impact on the sight and lives of millions of people.

Ocular findings in a double-blind study of ivermectin versus diethylcarbamazine versus placebo in the treatment of onchocerciasis

The effect of ivermectin, a new microfilaricide, was assessed in a double blind trial against diethylcarbamazine citrate (DEC) and placebo. Fifty-nine adult males with moderate to heavy infection with Onchocerca volvulus and with eye involvement were recruited from an area under Onchocerciasis Control Programme (OCP) vector control in Northern Ghana. They were randomly assigned to an eight-day treatment with ivermectin as a single dose of 12 mg on day 1 followed by placebo for the remaining seven days, or DEC, total dose 1.3 g, or placebo, and ophthalmological review was undertaken over a period of one year. DEC acted quickly to eliminate microfilariae from the eye and was associated with reactive ocular changes and in a few cases functional deficit. Ivermectin eliminated microfilariae slowly from the anterior chamber of the eye over a period of six months. The ocular inflammatory reaction was minimal and no functional deficit occurred. It is postulated that the observed slow action of ivermectin on the eye may be attributed in part to its instability to cross the blood-aqueous humour barrier because of its molecular size as a macrocyclic lactone causing microfilariae to leave the eye gradually along a newly created gradient. Ivermectin is an effective microfilaricide with minimal ocular adverse effect and could therefore be suitable for widespread application without strict supervision.

A double-blind comparison of the efficacy and safety of ivermectin and diethylcarbamazine in a placebo controlled study of Senegalese patients with onchocerciasis

Ivermectin (MK-933) has been compared with diethylcarbamazine (DEC) and placebo in a double-blind study in 30 adult male Senegalese patients with Onchocerca volvulus infection. 10 patients were randomly assigned to each treatment group. Ivermectin was administered as a single oral dose of 12 mg and DEC as 50 mg daily for two days and 100 mg twice daily for the following six days, total 1.3 g in eight days. Skin O. volvulus microfilaria densities remained near pre-study values in the placebo patients, but decreased rapidly with both active drugs to mean values about 2% of pretreatment (Day 8) and then increased slowly, reaching in 12 months about 4% of pre-treatment (ivermectin) and 18% (DEC). This difference is statistically significant. Clinical adverse reactions were recorded in four ivermectin, ten DEC and three placebo patients. One ivermectin and six DEC patients received steroid treatment for relief of these reactions. Serious adverse ocular changes were not seen in any patients, possibly because of the steroid therapy in the DEC patients. Adult O. volvulus from onchocercal nodules one and six months after treatment showed no effect of either drug on viability. Intra-uterine developing forms of the microfilariae appeared normal in all three treatment groups at the one month examination but deformed and degenerated forms were evident at six months in the ivermectin group but not in the DEC and placebo patients. Ivermectin as a single oral dose appears to be a safer and more effective microfilaricidal drug in human onchocerciasis than DEC in the standard multi-dose regimen.

Double-blind study of ivermectin and diethylcarbamazine in African onchocerciasis patients with ocular involvement

In a randomised double-blind study, ivermectin was compared with diethylcarbamazine (DEC) and placebo in the treatment of onchocerciasis in 30 male patients from Mali with moderate to heavy Onchocerca volvulus infections and ocular involvement. 10 patients received a single oral dose of ivermectin, 12 mg, 10 received DEC daily for eight days (total dose 1.3 g), and 10 received matching placebo. Patients were examined periodically for twelve months. Punctate keratitis disappeared in 6 of 7 ivermectin patients but increased in DEC patients. Numbers of O volvulus microfilariae (mf) in the anterior chamber decreased slowly and eventually disappeared in most ivermectin patients during the six months following treatment; anterior chamber mf disappeared more rapidly in some patients after DEC, but reappeared within six months of stopping treatment. Both ivermectin and DEC caused a prompt decrease in mean skin mf density; density then increased in both groups over the twelve month observation period, reaching 9% of pretreatment values in ivermectin patients and 45% in the DEC group. Analysis of adult O volvulus from nodules excised at three and twelve months post treatment showed no effect of either drug on viability; however, there was evidence of degeneration of intra-uterine developing mf in the ivermectin group. Side-effects were less frequent and less severe in ivermectin patients than in DEC patients. Ivermectin as a single oral dose appears to be a more effective microfilaricidal drug than DEC in onchocerciasis.

Comparison of ivermectin and diethylcarbamazine in the treatment of onchocerciasis

We compared ivermectin with diethylcarbamazine for the treatment of onchocerciasis in a double-blind, placebo-controlled trial. Thirty men with moderate to heavy infection and ocular involvement were randomly assigned to receive ivermectin in a single oral dose (200 micrograms per kilogram of body weight), diethylcarbamazine daily for eight days, or placebo. Diethylcarbamazine caused a significantly more severe systemic reaction than ivermectin (P less than 0.001), whereas the reaction to ivermectin did not differ from the reaction to placebo. Diethylcarbamazine markedly increased the number of punctate opacities in the eye (P less than 0.001), as well as the number of dead and living microfilariae in the cornea over the first week of therapy. Ivermectin had no such effect. Both ivermectin and diethylcarbamazine promptly reduced skin microfilaria counts, but only in the ivermectin group did counts remain significantly lower (P less than 0.005) than in the placebo group at the end of six months of observation. Analysis of adult worms isolated from nodules obtained two months after the start of therapy showed no effect of either drug on viability. Ivermectin appears to be a better tolerated, safer, and more effective microfilaricidal agent than diethylcarbamazine for the treatment of onchocerciasis.

A diagnostic "patch test" for onchocerciasis using topical diethylcarbamazine

There is great need for a simple, inexpensive, and sensitive diagnostic test for onchocerciasis, especially in endemic areas where trained personnel and laboratory facilities are limited. Diethylcarbamazine (DEC) was applied as a "patch test" to the skin of 45 patients with onchocerciasis in the Southern Sudan. 75 tests were done on these 45 patients, and 69 (92%) were positive. A positive reaction was a papular eruption beneath the patch. Histopathological studies of the skin beneath the patch revealed the microscopic features of a severe Mazzotti reaction, including degenerating microfilariae in the upper dermis and within epidermal eosinophilic abscesses.

Recent developments in the treatment of onchocerciasis

The treatment of onchocerciasis using diethylcarbamazine and suramin sodium, which can kill different stages of the parasite, Onchocerca volvulus, remains unsatisfactory. Recent studies have more clearly defined the serious limitations of the existing forms of treatment. However, two new classes of compounds, the benzimidazoles and avermectins, offer exciting new leads in the search for a safe and effective treatment that could be used on a large scale.

Comparison of flubendazole and diethylcarbamazine in treatment of onchocerciasis

Flubendazole, an injectable benzimidazole drug, was compared with diethylcarbamazine (DEC) in a prospective double-blind study of the treatment of onchocerciasis. Nineteen Mexican men were randomly assigned to receive either flubendazole 750 mg intramuscularly once a week for 5 doses, or DEC 100 mg twice daily for 14 days, and they were then followed up for 12 months. Major systemic side-effects during the first 3 weeks were common in the DEC group but not in the flubendazole group in which there was considerable inflammation at the injection site instead. Ocular complications (limbitis, punctate keratitis, and uveitis) were also common in the DEC group, whereas in the flubendazole group they consisted only of one new punctate opacity at day 4 in one subject. One DEC patient also had several new areas of chorioretinal changes on day 2 but these had disappeared by 2 months. Skin microfilaria counts fell rapidly in the DEC group, but returned to the pretreatment levels. In contrast, skin microfilaria counts in the flubendazole group fell slowly, but by 6 and 12 months were lower than in the DEC group (at 12 months 0.2 vs 7.3 mf/mg, p less than 0.001). In addition, by 6 months none of the flubendazole subjects had intracorneal microfilariae, and only one had microfilariae in the anterior chamber, whereas the numbers of intraocular microfilariae in the DEC group had returned to pretreatment levels. The results suggest that flubendazole is safer and more effective than DEC in the treatment of onchocerciasis.

Chemotherapy of onchocerciasis: a controlled comparison of mebendazole, levamisole, and diethylcarbamazine

Four drug regimens for treating onchocerciasis were compared in a double-blind study in persons from an endemic area in southern Mexico. 40 men were randomly assigned to receive either diethylcarbamazine (DEC) (200 mg/day), mebendazole (2 g/day), levamisole (150 mg per week), or mebendazole plus levamisole. DEC produced the most rapid fall in skin microfilaria counts, but by 6 months the two groups receiving mebendazole showed similar or slightly greater reductions. Despite the administration of corticosteroids to persons receiving DEC, more systemic side-effects were seen in this group. Ocular complications were also commoner and more severe in those receiving DEC. The reduction in the number of intraocular microfilariae at 6 months was similar to those receiving DEC and mebendazole, alone or in combination with levamisole. Levamisole alone had no significant effect on microfilaria counts. Examination of adult worms in nodules excised at 2 months showed changes suggestive of an interruption of embryogenesis in those persons receiving the mebendazole-containing regimens only. The findings suggest that mebendazole may be a useful alternative to DEC in the treatment of onchocerciasis.