Overview: Report of a Scientific Working Group on Serious Adverse Events following Mectizan(R) treatment of onchocerciasis in Loa loa endemic areas

Serious adverse reactions associated with ivermectin: A systematic pharmacovigilance study in sub-Saharan Africa and in the rest of the World

BACKGROUND

Ivermectin is known to cause severe encephalopathies in subjects infected with loiasis, an endemic parasite in Sub-Saharan Africa (SSA). In addition, case reports have described ivermectin-related serious adverse drug reactions (sADRs) such as toxidermias, hepatic and renal disorders. The aim of this study was to identify suspected sADRs reported after ivermectin administration in VigiBase, the World Health Organization's global individual case safety reports database and analyze their frequency relative to the frequency of these events after other antinematodal drugs reported in SSA and other areas of the world (ROW).

METHODS

All antinematodal-related sADRs were extracted from VigiBase. Disproportionality analyses were conducted to investigate nervous, cutaneous, psychiatric, respiratory, renal, hepatic and cardiac suspected sADRs reported after ivermectin and benzimidazole drug administration across the world, in SSA and RoW.

PRINCIPAL FINDINGS

2041 post-ivermectin or post-benzimidazole suspected sADRs were identified including 667 after ivermectin exposure (208 in SSA and 459 in the RoW). We found an increased reporting for toxidermias, encephalopathies, confusional disorders after ivermectin compared to benzimidazole drug administration. Encephalopathies were not only reported from SSA but also from the RoW (adjusted reporting odds ratios [aROR] 6.30, 95% confidence interval: 2.68-14.8), highlighting the fact these types of sADR occur outside loiasis endemic regions.

CONCLUSION

We described for the first time suspected sADRs associated with ivermectin exposure according to geographical origin. While our results do not put in question ivermectin's excellent safety profile, they show that as for all drugs, appropriate pharmacovigilance for adverse reactions is indicated.

Central and Peripheral Nervous System Disorders Following Ivermectin Mass Administration: A Descriptive Study Based on the Democratic Republic of Congo Pharmacovigilance System

Introduction

The mainstay of onchocerciasis control currently is mass administration of ivermectin; however, this may be associated with serious adverse events, including deaths, when administered in areas where onchocerciasis and loiasis are co-endemic.

Objectives

The objective of the current study was to describe the central and peripheral nervous system disorders that occurred after mass administration of ivermectin in Democratic Republic of Congo (DRC).

Methods

This is a retrospective descriptive study involving a review of data on adverse events related to mass administration of ivermectin. Data on reported serious adverse events following mass administration of ivermectin in the DRC were extracted from the World Health Organization (WHO) Global individual case safety report (ICSR) database (VigiBase). The review covered the period 2009–2013 and focused on central and peripheral nervous system disorders. Relevant demographic, clinical, and parasitological data, including age, sex, area of residence, adverse events, and parasite density were extracted. Descriptive statistics were analyzed using Stata 12.

Results

A total of 52 ICSRs related to ivermectin intake were available in VigiBase, with 51 (98.1%) from the Province of Equateur. All patients had central and peripheral nervous system disorders; 25 (48.1%) had altered mental status. Of these, 23 (92.0%) satisfied the criteria for “probable/possible Loa loa encephalopathy temporally related to mectizan^®” (PLERM). The most frequent nervous system disorders among patients with PLERM were coma (74%), stupor (30%), headache (22%), and abnormal gait (22%). There were, on average, 2149.1 microfilariae per ml (mf/ml) in peripheral blood [95% confidence interval (CI) 463.6–3834.6; n = 23]. Post-treatment, 61% of PLERM cases had <1000 L. loa mf/ml of blood. One patient had microfilariae in the cerebrospinal fluid rather than the peripheral blood. We found 21.4% co-infection with Plasmodium falciparum and 4% mortality.

Conclusion

PLERM may occur at even low peripheral blood concentrations of microfilaria.

Mapping the distribution of Loa loa in Cameroon in support of the African Programme for Onchocerciasis Control

Background

Loa loa has recently emerged as a filarial worm of significant public health importance as a consequence of its impact on the African Programme for Onchocerciasis Control (APOC). Severe, sometimes fatal, encephalopathic reactions to ivermectin (the drug of choice for onchocerciasis control) have occurred in some individuals with high Loa loa microfilarial counts. Since high density of Loa loa microfilariae is known to be associated with high prevalence rates, a distribution map of the latter may determine areas where severe reactions might occur. The aim of the study was to identify variables which were significantly associated with the presence of a Loa microfilaraemia in the subjects examined, and to develop a spatial model predicting the prevalence of the Loa microfilaraemia.

Methods

Epidemiological data were collected from 14,225 individuals living in 94 villages in Cameroon, and analysed in conjunction with environmental data. A series of logistic regression models (multivariate analysis) was developed to describe variation in the prevalence of Loa loa microfilaraemia using individual level co-variates (age, sex, μl of blood taken for examination) and village level environmental co-variates (including altitude and satellite-derived vegetation indices).

Results

A spatial model of Loa loa prevalence was created within a geographical information system. The model was then validated using an independent data set on Loa loa distribution. When considering both data sets as a whole, and a prevalence threshold of 20%, the sensitivity and the specificity of the model were 81.7 and 69.4%, respectively.

Conclusions

The model developed has proven very useful in defining the areas at risk of post-ivermectin Loa-related severe adverse events. It is now routinely used by APOC when projects of community-directed treatment with ivermectin are examined.

Genetic heterogeneity in Loa loa parasites from southern Cameroon: A preliminary study

Ivermectin (or Mectizan™) is widely used by onchocerciasis and lymphatic filariasis control programs worldwide. Generally, Mectizan™ is both safe and well tolerated. An exception to this general pattern is in some areas co-endemic for Onchocerca volvulus and Loa loa, where a number of severe adverse reactions to Mectizan™ have been noted in L. loa infected individuals. The vast majority of these severe adverse events have occurred in Southern Cameroon. This suggested the hypothesis that the parasites endemic to Southern Cameroon might form a distinct population that exhibited a phenotype of eliciting severe adverse reactions in Loa-infected individuals upon Mectizan™ exposure. To test this hypothesis, the DNA sequences of three potentially polymorphic loci were compared among L. loa parasites from Southern Cameroon and other endemic foci in Sub-Saharan Africa. Analysis of these data suggested that parasites from Southern Cameroon were at least as genetically diverse as those from other foci. Furthermore, no polymorphisms were noted that were unique to and shared among the parasite isolates from Southern Cameroon. Although a limited number of parasite isolates were tested, these results do not appear to support the hypothesis that L. loa parasites from Southern Cameroon represent a unique, genetically isolated population.