Atovaquone-proguanil versus mefloquine for malaria prophylaxis in nonimmune travelers: results from a randomized, double-blind study

Artemether-lumefantrine, mefloquine and atovaquone-proguanil in the treatment of uncomplicated Plasmodium falciparum malaria in travellers: A retrospective comparative study of efficacy and treatment failures

BACKGROUND

The aim of this study was to evaluate the rates of parasitaemia clearance and the prevalence of treatment failure in patients with uncomplicated Plasmodium falciparum malaria treated with artemether-lumefantrine (AL), mefloquine (MQ), and atovaquone-proguanil (AP).

METHOD

The retrospective descriptive study included adult patients with uncomplicated P. falciparum malaria treated at the University Hospital Bulovka in Prague from 2006 to 2019. Parasitaemia clearance was estimated using a linear regression model.

RESULTS

The study included 72 patients with a median age of 33 years (IQR 27-45) and a male to female ratio of 3.2:1. Thirty-six patients (50.0%) were treated with AL, 27 (37.5%) with MQ and 9 (12.5%) with AP. The proportion of VFR and migrants was 22.2% with no significant differences among the three groups. The median time to the parasitaemia clearance was two days (IQR 2-3) in patients treated with AL versus four days in the MQ (IQR 3-4) and AP (IQR 3-4) groups, p < 0.001. The clearance rate constant was 3.3/hour (IQR 2.5-4.0) for AL, 1.6/hour (IQR 1.3-1.9) for MQ, and 1.9/hour (IQR 1.3-2.4) for AP, p < 0.001. Malaria recrudescence occurred in 5/36 (13.9%) patients treated with AL and in no patients treated with MQ or AP.

CONCLUSIONS

The findings demonstrate the superior efficacy of AL compared to other oral antimalarials in early malaria treatment. However, we observed a higher rate of late treatment failure in patients treated with AL than previously reported. This issue warrants further investigation of possible dose adjustments, extended regimens, or alternative artemisinin-based combinations.

Mefloquine as a prophylaxis for malaria needs to be revisited

According to WHO, 2019 witnessed 229 million cases of malaria globally, of which Africa accounted for 94% of cases. Early diagnosis and treatment are the basis of malaria management, and the need for good chemoprophylaxis especially for people travelling to endemic areas is vital. There are a number of drug options available for the prophylaxis of malaria, mefloquine being one of the drugs used. Mefloquine has been around from the 1970s, and was developed in the United States keeping in mind the soldiers that were being deployed to areas where chloroquine resistant strains of Plasmodium were discovered. Mefloquine was preferred for its once a week dosage. Within a decade of its introduction, reports of the side effects associated with its long-term use surfaced. Mefloquine is now reported to cause a myriad of neuropsychiatric side effects including anxiety, sleep disturbance, depression, dizziness and frank psychosis, especially in patients with pre-existing psychiatric disorders. Many countries like the United States and the United Kingdom have updated their drug boxes to include the warning of these potential neuropsychiatric effects. This paper reviews the side effects of mefloquine and why there is a need to revisit its use in Indian drug policy.

The Ototoxicity of Antimalarial Drugs-A State of the Art Review

This review summarizes current knowledge about the occurrence of hearing and balance disorders after antimalarial drugs treatment. It also examines the clinical applications of antimalarials, their mechanisms behind this ototoxicity and how it can be monitored. It includes studies with larger numbers of patients and those in which auditory function was assessed using audiological tests. Some antimalarials have been repurposed for other conditions like autoimmune disorders, rheumatic diseases, some viral diseases and cancers. While old antimalarial drugs, such as quinoline derivatives, are known to demonstrate ototoxicity, a number of new synthetic antimalarial agents particularly artemisinin derivatives, demonstrate unknown ototoxicity. Adverse audiovestibular effects vary depending on the medication itself, its dose and route of administration, as well as the drug combination, treated disease and individual predispositions of the patient. Dizziness was commonly reported, while vestibular symptoms, hearing loss and tinnitus were observed much less frequently, and most of these symptoms were reversible. As early identification of ototoxic hearing loss is critical to introducing possible alternative treatments with less ototoxic medications, therefore monitoring systems of those drugs ototoxic side effects are much needed.

Malaria Disease and Chemoprophylaxis Usage among Israeli Travelers to Endemic Countries

Prevention of malaria in travelers to endemic countries is one of the complex challenges of travel medicine. Israel has a widespread culture of travel to developing countries, but information regarding malaria prevention is limited so far. Our study, conducted in Sheba Medical Center, Israel, during the years 2008-2018 examined malaria chemoprophylaxis usage and malaria cases in a large group of Israeli travelers returning from endemic countries with any medical complaint. Data were collected regarding travel destinations, conditions, duration of stay, and pretravel consultation. Altogether, 4,708 travelers were included in our study. Travel destinations included Asia (51%), Latin America (31%), and sub-Saharan Africa (SSA) (17%). Median travel duration was 26 days. Only 11.9% reported taking malaria chemoprophylaxis. Of the travelers to SSA, 41.3% took prophylaxis as opposed to only 6% outside of Africa. During the study years, 136 cases of malaria were diagnosed; among them, 82 (60%) were infected with Plasmodium falciparum, of whom all but two were from SSA and none adhered to prophylaxis. Malaria chemoprophylaxis usage was found to be negligible in travel to many countries still considered endemic. Higher prophylaxis usage was found among travelers to SSA, but numbers are still lower than recommended. The low number of malaria cases seen in destinations outside SSA, as documented in our cohort, is likely to represent travel to low risk areas and not high prophylaxis usage. We urge re-evaluation of current CDC and Israeli guidelines which still recommend using chemoprophylaxis in many low-risk countries, as focus on high-risk countries may increase adherence.

Imported Malaria in Countries where Malaria Is Not Endemic: a Comparison of Semi-immune and Nonimmune Travelers

The continuous increase in long-distance travel and recent large migratory movements have changed the epidemiological characteristics of imported malaria in countries where malaria is not endemic (here termed non-malaria-endemic countries). While malaria was primarily imported to nonendemic countries by returning travelers, the proportion of immigrants from malaria-endemic regions and travelers visiting friends and relatives (VFRs) in malaria-endemic countries has continued to increase. VFRs and immigrants from malaria-endemic countries now make up the majority of malaria patients in many nonendemic countries. Importantly, this group is characterized by various degrees of semi-immunity to malaria, resulting from repeated exposure to infection and a gradual decline of protection as a result of prolonged residence in non-malaria-endemic regions. Most studies indicate an effect of naturally acquired immunity in VFRs, leading to differences in the parasitological features, clinical manifestation, and odds for severe malaria and clinical complications between immune VFRs and nonimmune returning travelers. There are no valid data indicating evidence for differing algorithms for chemoprophylaxis or antimalarial treatment in semi-immune versus nonimmune malaria patients. So far, no robust biomarkers exist that properly reflect anti-parasite or clinical immunity. Until they are found, researchers should rigorously stratify their study results using surrogate markers, such as duration of time spent outside a malaria-endemic country.

Vivax Malaria Chemoprophylaxis: The Role of Atovaquone-Proguanil Compared to Other Options

Background

Atovaquone-proguanil is considered causal prophylaxis (inhibition of liver-stage schizonts) for Plasmodium falciparum; however, its causal prophylactic efficacy for Plasmodium vivax is not known. Travelers returning to nonendemic areas provide a unique opportunity to study P. vivax prophylaxis.

Methods

In a retrospective observational study, for 11 years, Israeli rafters who had traveled to the Omo River in Ethiopia, a highly malaria-endemic area, were followed for at least 1 year after their return. Malaria prophylaxis used during this period included mefloquine, doxycycline, primaquine, and atovaquone-proguanil. Prophylaxis failure was divided into early (within a month of exposure) and late malaria.

Results

Two hundred fifty-two travelers were included in the study. Sixty-two (24.6%) travelers developed malaria, 56 (91.9%) caused by P. vivax, with 54 (87.1%) cases considered as late malaria. Among travelers using atovaquone-proguanil, there were no cases of early P. falciparum or P. vivax malaria. However, 50.0% of atovaquone-proguanil users developed late vivax malaria, as did 46.5% and 43.5% of mefloquine and doxycycline users, respectively; only 2 (1.4%) primaquine users developed late malaria (P < .0001).

Conclusions

Short-course atovaquone-proguanil appears to provide causal (liver schizont stage) prophylaxis for P. vivax, but is ineffective against late, hypnozoite reactivation-related attacks. These findings suggest that primaquine should be considered as the chemoprophylactic agent of choice for areas with high co-circulation of P. falciparum and P. vivax.

Injectable anti-malarials revisited: discovery and development of new agents to protect against malaria

Over the last 15 years, the majority of malaria drug discovery and development efforts have focused on new molecules and regimens to treat patients with uncomplicated or severe disease. In addition, a number of new molecular scaffolds have been discovered which block the replication of the parasite in the liver, offering the possibility of new tools for oral prophylaxis or chemoprotection, potentially with once-weekly dosing. However, an intervention which requires less frequent administration than this would be a key tool for the control and elimination of malaria. Recent progress in HIV drug discovery has shown that small molecules can be formulated for injections as native molecules or pro-drugs which provide protection for at least 2 months. Advances in antibody engineering offer an alternative approach whereby a single injection could potentially provide protection for several months. Building on earlier profiles for uncomplicated and severe malaria, a target product profile is proposed here for an injectable medicine providing long-term protection from this disease. As with all of such profiles, factors such as efficacy, cost, safety and tolerability are key, but with the changing disease landscape in Africa, new clinical and regulatory approaches are required to develop prophylactic/chemoprotective medicines. An overall framework for these approaches is suggested here.

Pharmacotherapy for the prevention of malaria in pregnant women: currently available drugs and challenges

INTRODUCTION

Malaria in pregnancy continues to be a significant public health burden globally, with over 100 million women at risk each year. Sulfadoxine-pyrimethamine (SP) is the only antimalarial recommended for intermittent preventive therapy in pregnancy (IPTp) but increasing parasite resistance threatens its viability. There are few other available antimalarial therapies that currently have sufficient evidence of tolerability, safety, and efficacy to replace SP.

AREAS COVERED

Novel antimalarial combinations are under investigation for potential use as chemoprophylaxis and in IPTp regimens. The present review summarizes currently available therapies, emerging candidate combination therapies, and the potential challenges to integrating these into mainstream policy.

EXPERT OPINION

Alternative drugs or combination therapies to SP for IPTp are desperately required. Dihydroartemisinin-piperaquine and azithromycin-based combinations are showing great promise as potential candidates for IPTp but pharmacokinetic data suggest that dose modification may be required to ensure adequate prophylactic efficacy. If a suitable candidate regimen is not identified in the near future, the success of chemopreventive strategies such as IPTp may be in jeopardy.

Abbreviated atovaquone-proguanil prophylaxis regimens in travellers after leaving malaria-endemic areas: A systematic review

BACKGROUND

We evaluated existing data on the prophylactic efficacy of atovaquone-proguanil (AP) in order to determine whether prophylaxis in travellers can be discontinued on the day of return from a malaria-endemic area instead of seven days after return as per currently recommended post-travel schedule.

METHODS

PubMed and Embase databases were searched to identify relevant studies. This PROSPERO-registered systematic review followed PRISMA guidelines. The search strategy included terms or synonyms relevant to AP combined with terms to identify articles relating to prophylactic use of AP and inhibitory and half-life properties of AP. Studies considered for inclusion were: randomized controlled trials, cohort studies, quasi-experimental studies, open-label trials, patient-control studies, cross-sectional studies; as well as case-series and non-clinical studies. Data on study design, characteristics of participants, interventions, and outcomes were extracted. Primary outcomes considered relevant were prophylactic efficacy and prolonged inhibitory activity and half-life properties of AP.

RESULTS

The initial search identified 1,482 publications, of which 40 were selected based on screening. Following full text review, 32 studies were included and categorized into two groups, namely studies in support of the current post-travel regimen (with a total of 2,866 subjects) and studies in support of an alternative regimen (with a total of 533 subjects).

CONCLUSION

There is limited direct and indirect evidence to suggest that an abbreviated post-travel regimen for AP may be effective. Proguanil, however, has a short half-life and is essential for the synergistic effect of the combination. Stopping AP early may result in mono-prophylaxis with atovaquone and possibly select for atovaquone-resistant parasites. Furthermore, the quality of the studies in support of the current post-travel regimen outweighs the quality of the studies in support of an alternative short, post-travel regimen, and the total sample size of the studies to support stopping AP early comprises a small percentage of the total sample size of the studies performed to establish the efficacy of the current AP regimen. Additional research is required - especially from studies evaluating impact on malaria parasitaemia and clinical illness and conducted among travellers in high malaria risk settings - before an abbreviated regimen can be recommended in current practice.

PROSPERO REGISTRATION NUMBER

CRD42017055244.

Mefloquine for preventing malaria during travel to endemic areas

BACKGROUND

Mefloquine is one of four antimalarial agents commonly recommended for preventing malaria in travellers to malaria-endemic areas. Despite its high efficacy, there is controversy about its psychological side effects.

OBJECTIVES

To summarize the efficacy and safety of mefloquine used as prophylaxis for malaria in travellers.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; the Cochrane Central Register of Controlled Trials (CENTRAL), published on the Cochrane Library; MEDLINE; Embase (OVID); TOXLINE (https://toxnet.nlm.nih.gov/newtoxnet/toxline.htm); and LILACS. We also searched the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP; http://www.who.int/ictrp/en/) and ClinicalTrials.gov (https://clinicaltrials.gov/ct2/home) for trials in progress, using 'mefloquine', 'Lariam', and 'malaria' as search terms. The search date was 22 June 2017.

SELECTION CRITERIA

We included randomized controlled trials (for efficacy and safety) and non-randomized cohort studies (for safety). We compared prophylactic mefloquine with placebo, no treatment, or an alternative recommended antimalarial agent. Our study populations included all adults and children, including pregnant women.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility and risk of bias of trials, extracted and analysed data. We compared dichotomous outcomes using risk ratios (RR) with 95% confidence intervals (CI). Prespecified adverse outcomes are included in 'Summary of findings' tables, with the best available estimate of the absolute frequency of each outcome in short-term international travellers. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 20 RCTs (11,470 participants); 35 cohort studies (198,493 participants); and four large retrospective analyses of health records (800,652 participants). Nine RCTs explicitly excluded participants with a psychiatric history, and 25 cohort studies stated that the choice of antimalarial agent was based on medical history and personal preference. Most RCTs and cohort studies collected data on self-reported or clinician-assessed symptoms, rather than formal medical diagnoses. Mefloquine efficacyOf 12 trials comparing mefloquine and placebo, none were performed in short-term international travellers, and most populations had a degree of immunity to malaria. The percentage of people developing a malaria episode in the control arm varied from 1% to 82% (median 22%) and 0% to 13% in the mefloquine group (median 1%).In four RCTs that directly compared mefloquine, atovaquone-proguanil and doxycycline in non-immune, short-term international travellers, only one clinical case of malaria occurred (4 trials, 1822 participants). Mefloquine safety versus atovaquone-proguanil Participants receiving mefloquine were more likely to discontinue their medication due to adverse effects than atovaquone-proguanil users (RR 2.86, 95% CI 1.53 to 5.31; 3 RCTs, 1438 participants; high-certainty evidence). There were few serious adverse effects reported with mefloquine (15/2651 travellers) and none with atovaquone-proguanil (940 travellers).One RCT and six cohort studies reported on our prespecified adverse effects. In the RCT with short-term travellers, mefloquine users were more likely to report abnormal dreams (RR 2.04, 95% CI 1.37 to 3.04, moderate-certainty evidence), insomnia (RR 4.42, 95% CI 2.56 to 7.64, moderate-certainty evidence), anxiety (RR 6.12, 95% CI 1.82 to 20.66, moderate-certainty evidence), and depressed mood during travel (RR 5.78, 95% CI 1.71 to 19.61, moderate-certainty evidence). The cohort studies in longer-term travellers were consistent with this finding but most had larger effect sizes. Mefloquine users were also more likely to report nausea (high-certainty evidence) and dizziness (high-certainty evidence).Based on the available evidence, our best estimates of absolute effect sizes for mefloquine versus atovaquone-proguanil are 6% versus 2% for discontinuation of the drug, 13% versus 3% for insomnia, 14% versus 7% for abnormal dreams, 6% versus 1% for anxiety, and 6% versus 1% for depressed mood. Mefloquine safety versus doxycyclineNo difference was found in numbers of serious adverse effects with mefloquine and doxycycline (low-certainty evidence) or numbers of discontinuations due to adverse effects (RR 1.08, 95% CI 0.41 to 2.87; 4 RCTs, 763 participants; low-certainty evidence).Six cohort studies in longer-term occupational travellers reported our prespecified adverse effects; one RCT in military personnel and one cohort study in short-term travellers reported adverse events. Mefloquine users were more likely to report abnormal dreams (RR 10.49, 95% CI 3.79 to 29.10; 4 cohort studies, 2588 participants, very low-certainty evidence), insomnia (RR 4.14, 95% CI 1.19 to 14.44; 4 cohort studies, 3212 participants, very low-certainty evidence), anxiety (RR 18.04, 95% CI 9.32 to 34.93; 3 cohort studies, 2559 participants, very low-certainty evidence), and depressed mood (RR 11.43, 95% CI 5.21 to 25.07; 2 cohort studies, 2445 participants, very low-certainty evidence). The findings of the single cohort study reporting adverse events in short-term international travellers were consistent with this finding but the single RCT in military personnel did not demonstrate a difference between groups in frequencies of abnormal dreams or insomnia.Mefloquine users were less likely to report dyspepsia (RR 0.26, 95% CI 0.09 to 0.74; 5 cohort studies, 5104 participants, low certainty-evidence), photosensitivity (RR 0.08, 95% CI 0.05 to 0.11; 2 cohort studies, 1875 participants, very low-certainty evidence), vomiting (RR 0.18, 95% CI 0.12 to 0.27; 4 cohort studies, 5071 participants, very low-certainty evidence), and vaginal thrush (RR 0.10, 95% CI 0.06 to 0.16; 1 cohort study, 1761 participants, very low-certainty evidence).Based on the available evidence, our best estimates of absolute effect for mefloquine versus doxycyline were: 2% versus 2% for discontinuation, 12% versus 3% for insomnia, 31% versus 3% for abnormal dreams, 18% versus 1% for anxiety, 11% versus 1% for depressed mood, 4% versus 14% for dyspepsia, 2% versus 19% for photosensitivity, 1% versus 5% for vomiting, and 2% versus 16% for vaginal thrush.Additional analyses, including comparisons of mefloquine with chloroquine, added no new information. Subgroup analysis by study design, duration of travel, and military versus non-military participants, provided no conclusive findings.

AUTHORS' CONCLUSIONS

The absolute risk of malaria during short-term travel appears low with all three established antimalarial agents (mefloquine, doxycycline, and atovaquone-proguanil).The choice of antimalarial agent depends on how individual travellers assess the importance of specific adverse effects, pill burden, and cost. Some travellers will prefer mefloquine for its once-weekly regimen, but this should be balanced against the increased frequency of abnormal dreams, anxiety, insomnia, and depressed mood.

Safety of antimalarial medications for use while scuba diving in malaria Endemic Regions

Background

Recreational diving occurs annually in areas of the world where malaria is endemic. The safety and efficacy of antimalarials for travelers in a hyperbaric environment is unknown. Of particular concern would be medications with adverse effects that could either mimic diving related illnesses such as barotrauma, decompression sickness (DCS) and gas toxicities, or increase the risk for such illnesses.

Methods

We conducted a review of PubMed and Cochrane databases to determine rates of neurologic adverse effects or other effects from antimalarials that may be a problem in the diving environment.

Results

One case report was found on diving and mefloquine. Multiple case reports and clinical trials were found describing neurologic adverse effects of the major chemoprophylactic medications atovaquone/proguanil, chloroquine, doxycycline, mefloquine, and primaquine.

Conclusions

Of the available literature, atovaquone/proguanil and doxycycline are most likely the safest agents and should be preferred; atovaquone/proguanil is superior due to reduced rates of sunburn in the marine environment. Primaquine also appears to be safe, but has reduced efficacy against P. falciparum; mefloquine possesses the highest rate of neurologic side effects and therefore these agents should be limited to extreme cases of patients intolerant to other agents. Chloroquine appears unsafe in the hyperbaric environment and should be avoided. More studies are required to include database reviews of returned divers traveling to malaria endemic areas and randomized controlled trials in the hyperbaric environments.

A serious nightmare: psychiatric and neurologic adverse reactions to mefloquine are serious adverse reactions

Mefloquine (originally marketed as Lariam) is a neurotoxic quinoline derivative antimalarial drug that is known to cause serious and potentially lasting neuropsychiatric adverse reactions. Since 2013, drug regulators in several jurisdictions, including the United States, the United Kingdom, Ireland, and Canada, have required their mefloquine labels be updated to warn that when used for malaria prophylaxis the drug should be discontinued at the onset of neurologic or psychiatric symptoms. These recent changes to the international labeling serve to imply that psychiatric and neurologic reactions to mefloquine prophylaxis may be an early warning of an impending more serious reaction that may further jeopardize the patient with continued use of the drug. To prevent these more serious effects, these drug labels now warn that mefloquine should be discontinued and that patients seek immediate medical intervention to obtain an alternative antimalarial drug when psychiatric or neurologic symptoms occur. When used correctly for malaria prophylaxis as the updated labeling now directs, it is reasonable to expect that mefloquine will be discontinued, and an alternative drug substituted, in each patient who develops psychiatric or neurologic symptoms. This opinion discusses the implications of this updated labeling for the reporting of adverse reactions and for the continued use of the drug in malaria prophylaxis.

Antimalarial drugs and the prevalence of mental and neurological manifestations: A systematic review and meta-analysis

Background: Antimalarial drugs affect the central nervous system, but it is difficult to differentiate the effect of these drugs from that of the malaria illness. We conducted a systematic review to determine the association between anti-malarial drugs and mental and neurological impairment in humans.  Methods: We systematically searched online databases, including Medline/PubMed, PsychoInfo, and Embase, for articles published up to 14th July 2016. Pooled prevalence, heterogeneity and factors associated with prevalence of mental and neurological manifestations were determined using meta-analytic techniques.  Results: Of the 2,349 records identified in the initial search, 51 human studies met the eligibility criteria. The median pooled prevalence range of mental and neurological manifestations associated with antimalarial drugs ranged from 0.7% (dapsone) to 48.3% (minocycline) across all studies, while it ranged from 0.6% (pyrimethamine) to 42.7% (amodiaquine) during treatment of acute malaria, and 0.7% (primaquine/dapsone) to 55.0% (sulfadoxine) during prophylaxis. Pooled prevalence of mental and neurological manifestations across all studies was associated with an increased number of antimalarial drugs (prevalence ratio= 5.51 (95%CI, 1.05-29.04); P=0.045) in a meta-regression analysis. Headaches (15%) and dizziness (14%) were the most common mental and neurological manifestations across all studies. Of individual antimalarial drugs still on the market, mental and neurological manifestations were most common with the use of sulphadoxine (55%) for prophylaxis studies and amodiaquine (42.7%) for acute malaria studies. Mefloquine affected more domains of mental and neurological manifestations than any other antimalarial drug.  Conclusions: Antimalarial drugs, particularly those used for prophylaxis, may be associated with mental and neurological manifestations, and the number of antimalarial drugs taken determines the association. Mental and neurological manifestations should be assessed following the use of antimalarial drugs.

Antimalarial drugs and the prevalence of mental and neurological manifestations: A systematic review and meta-analysis

Background: Antimalarial drugs affect the central nervous system, but it is difficult to differentiate the effect of these drugs from that of the malaria illness. We conducted a systematic review to determine the association between anti-malarial drugs and mental and neurological impairment in humans.  Methods: We systematically searched online databases, including Medline/PubMed, PsychoInfo, and Embase, for articles published up to 14th July 2016. Pooled prevalence, heterogeneity and factors associated with prevalence of mental and neurological manifestations were determined using meta-analytic techniques.  Results: Of the 2,349 records identified in the initial search, 51 human studies met the eligibility criteria. The median pooled prevalence range of mental and neurological manifestations associated with antimalarial drugs ranged from 0.7% (dapsone) to 48.3% (minocycline) across all studies, while it ranged from 0.6% (pyrimethamine) to 42.7% (amodiaquine) during treatment of acute malaria, and 0.7% (primaquine/dapsone) to 55.0% (sulfadoxine) during prophylaxis. Pooled prevalence of mental and neurological manifestations across all studies was associated with an increased number of antimalarial drugs (prevalence ratio= 5.51 (95%CI, 1.05-29.04); P=0.045) in a meta-regression analysis. Headaches (15%) and dizziness (14%) were the most common mental and neurological manifestations across all studies. Of individual antimalarial drugs still on the market, mental and neurological manifestations were most common with the use of sulphadoxine (55%) for prophylaxis studies and amodiaquine (42.7%) for acute malaria studies. Mefloquine affected more domains of mental and neurological manifestations than any other antimalarial drug.  Conclusions: Antimalarial drugs, particularly those used for prophylaxis, may be associated with mental and neurological manifestations, and the number of antimalarial drugs taken determines the association. Mental and neurological manifestations should be assessed following the use of antimalarial drugs.

Identification of a Syndrome Class of Neuropsychiatric Adverse Reactions to Mefloquine from Latent Class Modeling of FDA Adverse Event Reporting System Data

Introduction

Although mefloquine use is known to be associated with a risk of severe neuropsychiatric adverse reactions that are often preceded by prodromal symptoms, specific combinations of neurologic or psychiatric reactions associated with mefloquine use are not well described in the literature. This study sought to identify a distinct neuropsychiatric syndrome class associated with mefloquine use in reports of adverse events.

Methods

Latent class modeling of US Food and Drug Administration Adverse Event Reporting System (FAERS) data was performed using indicators defined by the Medical Dictionary for Regulatory Activities neurologic and psychiatric high-level group terms, in a study dataset of FAERS reports (n = 5332) of reactions to common antimalarial drugs.

Results

A distinct neuropsychiatric syndrome class was identified that was strongly and significantly associated with reports of mefloquine use (odds ratio = 3.92, 95% confidence interval 2.91–5.28), defined by a very high probability of symptoms of deliria (82.7%) including confusion and disorientation, and a moderate probability of other severe psychiatric and neurologic symptoms including dementia and amnesia (18.6%) and seizures (18.1%). The syndrome class was also associated with symptoms that are considered prodromal including anxiety, depression, sleep disturbance, and abnormal dreams, and neurological symptoms such as dizziness, vertigo, and paresthesias.

Conclusions

This study confirms in FAERS reports the existence of a severe mefloquine neuropsychiatric syndrome class associated with common symptoms that may be considered prodromal. Clinical identification of the characteristic symptoms of this syndrome class may aid in improving case finding in pharmacovigilance studies of more serious adverse reactions to the drug.

Genetic Evidence for Cytochrome b Qi Site Inhibition by 4(1H)-Quinolone-3-Diarylethers and Antimycin in Toxoplasma gondii

Toxoplasma gondii is an apicomplexan parasite that causes fatal and debilitating brain and eye disease. Endochinlike quinolones (ELQs) are preclinical compounds that are efficacious against apicomplexan-caused diseases, including toxoplasmosis, malaria, and babesiosis. Of the ELQs, ELQ-316 has demonstrated the greatest efficacy against acute and chronic experimental toxoplasmosis. Although genetic analyses in other organisms have highlighted the importance of the cytochrome bc1 complex Qi site for ELQ sensitivity, the mechanism of action of ELQs against T. gondii and the specific mechanism of ELQ-316 remain unknown. Here, we describe the selection and genetic characterization of T. gondii clones resistant to ELQ-316. A T. gondii strain selected under ELQ-316 drug pressure was found to possess a Thr222-Pro amino acid substitution that confers 49-fold resistance to ELQ-316 and 19-fold resistance to antimycin, a well-characterized Qi site inhibitor. These findings provide further evidence for ELQ Qi site inhibition in T. gondii and greater insight into the interactions of Qi site inhibitors with the apicomplexan cytochrome bc1 complex.

Response to fever and utilization of standby emergency treatment (SBET) for malaria in travellers to Southeast Asia: a questionnaire-based cohort study

Background

Guidelines in several European countries recommend standby emergency treatment (SBET) for travellers to regions with low or medium malaria transmission instead of continuous chemoprophylaxis: travellers are advised to seek medical assistance within 24 h in case of fever and to self-administer SBET only if they are not able to consult a doctor within the time period specified. Data on healthcare-seeking behaviour of febrile travellers and utilization of SBET is however scarce as only two studies were performed in the mid-1990s. Since tourism is constantly increasing and malaria epidemiology has dramatically changed in the meantime more knowledge is urgently needed.

Methods

Some 876 travellers to destinations in South and Southeast Asia with low or medium malaria transmission were recruited in the travel clinic of the University Medical Center Hamburg-Eppendorf. Demographic and travel-related data were collected by using questionnaires. Pre-travel advice was carried out and SBET was prescribed in accordance to national guidelines. Post-travel phone interviews were performed to assess health incidents during travel and individual responses of travellers to febrile illness.

Results

Out of 714 patients who were monitored, 130 (18%) reported onset of fever during travel or 14 days after return. Of those travellers who reported fever, 100 (80%) carried SBET during travel. The vast majority of 79 (79%) febrile travellers who carried SBET did not seek medical assistance. Overall, 14 (14%) febrile patients who carried SBET and six (20%) patients who did not carry SBET took the correct measure (doctor visit or timely SBET administration) as a response to febrile illness, respectively. Only two travellers self-administered SBET, but both of them applied the wrong regimen.

Conclusions

In view of declining malaria transmission and improving medical infrastructure in most countries of Southeast Asia and obvious obstacles concerning SBET as shown in this study the current strategy should be re-evaluated. Pre-travel advice concerning malaria in SEA should focus on appropriate mosquito bite protection and clearly emphasize the need to see a doctor within 24 h after onset of fever.

Neuropsychiatric Outcomes After Mefloquine Exposure Among U.S. Military Service Members

Mefloquine was widely prescribed to U.S. military service members until 2009 when use was limited to personnel with contraindications to doxycycline and no contraindications to mefloquine. The need to estimate the occurrence of neuropsychiatric outcomes (NPOs) in service members prescribed mefloquine warranted a comprehensive evaluation of this issue. Active component service members filling a prescription for mefloquine, doxycycline, or atovaquone/proguanil (A/P) between January 1, 2008 and June 30, 2013, were included in the analysis. The risk of developing incident NPOs and the risk of subsequent NPOs among subjects with a history of the condition were assessed. A total of 367,840 individuals were evaluated (36,538 received mefloquine, 318,421 received doxycycline, and 12,881 received A/P). Among deployed individuals prescribed mefloquine, an increased risk of incident anxiety was seen when compared with doxycycline recipients (incidence rate ratio [IRR] = 1.12 [1.01-1.24]). Among nondeployed mefloquine recipients, an increased risk of posttraumatic stress disorder (PTSD) was seen when compared with A/P recipients (IRR = 1.83 [1.07-3.14]). An increased risk of tinnitus was seen for both deployed and nondeployed mefloquine recipients compared with A/P recipients (IRR = 1.81 [1.18-2.79]), 1.51 (1.13-2.03), respectively). Six percent of the mefloquine cohort had an NPO in the year before receiving mefloquine. When comparing individuals with a prior neuropsychiatric history to those without, the ratio of relative risks for adjustment disorder, anxiety, insomnia, and PTSD were higher (not statistically significant) for mefloquine compared with doxycycline. These findings emphasize the continued need for physicians prescribing mefloquine to conduct contraindication screening.

Psychiatric effects of malaria and anti-malarial drugs: historical and modern perspectives

The modern medical literature implicates malaria, and particularly the potentially fatal form of cerebral malaria, with a risk of neurocognitive impairment. Yet historically, even milder forms of malaria were associated in the literature with a broad range of psychiatric effects, including disorders of personality, mood, memory, attention, thought, and behaviour. In this article, the history of psychiatric effects attributed to malaria and post-malaria syndromes is reviewed, and insights from the historical practice of malariotherapy in contributing to understanding of these effects are considered. This review concludes with a discussion of the potentially confounding role of the adverse effects of anti-malarial drugs, particularly of the quinoline class, in the unique attribution of certain psychiatric effects to malaria, and of the need for a critical reevaluation of the literature in light of emerging evidence of the chronic nature of these adverse drug effects.

Neuropsychiatric Adverse Reactions to Mefloquine: a Systematic Comparison of Prescribing and Patient Safety Guidance in the US, UK, Ireland, Australia, New Zealand, and Canada

Introduction

The antimalarial drug mefloquine (MQ) is associated with neuropsychiatric adverse reactions, some of which may predict the development of more serious effects. Although prescribing guidance in the United States drug label (DL) recommends to discontinue MQ at the onset of neuropsychiatric symptoms, only certain reactions are listed in both the DL and the corresponding patient medication guide with a recommendation to discontinue or to consult a physician should they occur. To identify possible prodromal reactions for which there is complete or partial agreement in prescribing and patient recommendations, a systematic comparison of international drug safety labeling was performed.

Methods

The full text of each DL and medication guide (or equivalent) from six primarily English-speaking countries was reviewed to identify specific reactions with corresponding recommendations in drug safety labeling. Percentage agreement across the countries in corresponding recommendations was determined by MedDRA^® high level group term (HLGT).

Results

Recommendations were found for reactions in 22 neuropsychiatric HLGTs. Complete or partial international agreement was found for reactions in 11 (50%) HLGTs.

Conclusion

This analysis suggests opportunities for physicians to improve patient counseling and for international drug regulators to clarify language in MQ safety labeling to reflect national risk–benefit considerations.

Adverse neuropsychiatric effects of antimalarial drugs

INTRODUCTION

Antimalarial drugs are the primary weapon to treat parasite infection, save lives, and curtail further transmission. Accumulating data have indicated that at least some antimalarial drugs may contribute to severe neurological and/or psychiatric side effects which further complicates their use and limits the pool of available medications.

AREAS COVERED

In this review article, we summarize published scientific studies in search of evidence of the neuropsychiatric effects that may be attributed to the commonly used antimalarial drugs administered alone or in combination. Each individual drug was used as a search term in addition to keywords such as neuropsychiatric, adverse events, and neurotoxicity.

EXPERT OPINION

Accumulating data based on published reports over several decades have suggested that among the major commonly used antimalarial drugs, only mefloquine exhibited clear indications of serious neurological and/or psychiatric side effects. A more systematic approach to assess the neuropsychiatric adverse effects of new or repurposed antimalarial drugs on their safety, tolerability and efficacy phases of clinical studies and in post-marketing surveillance, is needed to ensure that these life-saving tools remain available and can be prescribed with appropriate caution and medical judgment.

Malaria Prevention, Mefloquine Neurotoxicity, Neuropsychiatric Illness, and Risk-Benefit Analysis in the Australian Defence Force

The Australian Defence Force (ADF) has used mefloquine for malaria chemoprophylaxis since 1990. Mefloquine has been found to be a plausible cause of a chronic central nervous system toxicity syndrome and a confounding factor in the diagnosis of existing neuropsychiatric illnesses prevalent in the ADF such as posttraumatic stress disorder and traumatic brain injury. Overall health risks appear to have been mitigated by restricting the drug's use; however serious risks were realised when significant numbers of ADF personnel were subjected to clinical trials involving the drug. The full extent of the exposure, health impacts for affected individuals, and consequences for ADF health management including mental health are not yet known, but mefloquine may have caused or aggravated neuropsychiatric illness in large numbers of patients who were subsequently misdiagnosed and mistreated or otherwise failed to receive proper care. Findings in relation to chronic mefloquine neurotoxicity were foreseeable, but this eventuality appears not to have been considered during risk-benefit analyses. Thorough analysis by the ADF would have identified this long-term risk as well as other qualitative risk factors. Historical exposure of ADF personnel to mefloquine neurotoxicity now also necessitates ongoing risk monitoring and management in the overall context of broader health policies.

Malaria Chemoprophylaxis and Self-Reported Impact on Ability to Work: Mefloquine Versus Doxycycline

BACKGROUND

It is well known that both mefloquine and doxycycline are commonly associated with adverse effects when taken for malaria chemoprophylaxis. However, the relative impact of these on travelers' ability to work is not so well understood. The aim of this study was to identify which drug has a lesser impact on the ability to work as measured by self-reported severity of adverse effects via a questionnaire.

METHODS

This was a questionnaire-based two-arm cohort study. Participants were soldiers selected from 10 consecutive units training in Kenya during 2012 and 2013. The exposure was either doxycycline or mefloquine and the main outcome measure was impact upon ability to work. Each cohort was advised to take doxycycline or mefloquine with exceptions at the individual level where medically or occupationally advised.

RESULTS

Significantly more (p < 0.0001) doxycycline users reported that one or more adverse effects had interfered with their ability to do their job than mefloquine users. Of the 867 mefloquine users, who reported on the impact of adverse effects, 109 (12.6%) reported that one or more adverse effects had impacted upon their ability to do their job, compared to 152 (22.2%) of the 685 doxycycline users who had reported on the impact of any adverse effects. Doxycycline symptoms were predominantly gastrointestinal and dermatological, whereas mefloquine symptoms were neuropsychiatric.

CONCLUSIONS

Self-reported symptoms were common in those that responded and, while the true background rate of adverse effects (off any medication) is unknown, doxycycline had a significantly increased rate compared with mefloquine and was associated with a greater occupational impact. Therefore, this study supports the view that, for organizations which provide malaria chemoprophylaxis to employees free of charge, mefloquine should be the first-choice antimalarial drug where the only alternative is doxycycline.

Rational Risk-Benefit Decision-Making in the Setting of Military Mefloquine Policy

Mefloquine is an antimalarial drug that has been commonly used in military settings since its development by the US military in the late 1980s. Owing to the drug's neuropsychiatric contraindications and its high rate of inducing neuropsychiatric symptoms, which are contraindications to the drug's continued use, the routine prescribing of mefloquine in military settings may be problematic. Due to these considerations and to recent concerns of chronic and potentially permanent psychiatric and neurological sequelae arising from drug toxicity, military prescribing of mefloquine has recently decreased. In settings where mefloquine remains available, policies governing prescribing should reflect risk-benefit decision-making informed by the drug's perceived benefits and by consideration both of the risks identified in the drug's labeling and of specific military risks associated with its use. In this review, these risks are identified and recommendations are made for the rational prescribing of the drug in light of current evidence.

Complex Membrane Channel Blockade: A Unifying Hypothesis for the Prodromal and Acute Neuropsychiatric Sequelae Resulting from Exposure to the Antimalarial Drug Mefloquine

The alkaloid toxin quinine and its derivative compounds have been used for many centuries as effective medications for the prevention and treatment of malaria. More recently, synthetic derivatives, such as the quinoline derivative mefloquine (bis(trifluoromethyl)-(2-piperidyl)-4-quinolinemethanol), have been widely used to combat disease caused by chloroquine-resistant strains of the malaria parasite, Plasmodium falciparum. However, the parent compound quinine, as well as its more recent counterparts, suffers from an incidence of adverse neuropsychiatric side effects ranging from mild mood disturbances and anxiety to hallucinations, seizures, and psychosis. This review considers how the pharmacology, cellular neurobiology, and membrane channel kinetics of mefloquine could lead to the significant and sometimes life-threatening neurotoxicity associated with mefloquine exposure. A key role for mefloquine blockade of ATP-sensitive potassium channels and connexins in the substantia nigra is considered as a unifying hypothesis for the pathogenesis of severe neuropsychiatric events after mefloquine exposure in humans.

Comparative benefit of malaria chemoprophylaxis modelled in United Kingdom travellers

BACKGROUND

Chemoprophylaxis against falciparum malaria is recommended for travellers from non-endemic countries to malarious destinations, but debate continues on benefit, especially with regard to mefloquine. Quantification of benefit for travellers from the United Kingdom (UK) was modelled to assist clinical and public health decision making.

METHODS

The model was constructed utilising: World Tourism Organization data showing total number of arrivals from the UK in countries with moderate or high malaria risk; data from a retrospective UK Clinical Practice Research Datalink (CPRD) drug utilisation study; additional information on chemoprophylaxis, case fatality and tolerability were derived from the travel medicine literature. Chemoprophylaxis with the following agents was considered: atovaquone-proguanil (AP), chloroquine with and without proguanil (C ± P), doxycycline (Dx), mefloquine (Mq). The model was validated for the most recent year with temporally matched datasets for UK travel destinations and imported malaria (2007) against UK Health Protection Agency data on imported malaria.

RESULTS

The median (mean) duration of chemoprophylaxis for each agent in weeks (CPRD) was: AP 3.3 (3.5), C ± P 9 (12.1), Dx 8 (10.3), Mq 9 (12.3): the maximum duration of use of all regimens was 52 weeks. The model correctly predicted falciparum malaria deaths and gave a robust estimate of total cases--model: 5 deaths from 1118 cases; UK Health Protection Agency: 5 deaths from 1153 cases. The number needed to take chemoprophylaxis (NNP) to prevent a case of malaria considered against the 'background' reported incidence in non-users of chemoprophylaxis deemed in need of chemoprophylaxis was: C ± P 272, Dx 269, Mq 260, AP 252; the NNP to prevent a UK traveller malaria death was: C ± P 62613, Dx 61923, Mq 59973, AP 58059; increasing the 'background' rate by 50% yielded NNPs of: C ± P 176, Dx 175, Mq 171, AP 168. The impact of substituting atovaquone-proguanil for all mefloquine usage resulted in a 2.3% decrease in estimated infections. The number of travellers experiencing moderate adverse events (AE) or those requiring medical attention or drug withdrawal per case prevented is as follows: C ± P 170, Mq 146, Dx 114, AP 103.

CONCLUSIONS

The model correctly predicted the number of malaria deaths, providing a robust and reliable estimate of the number of imported malaria cases in the UK, and giving a measure of benefit derived from chemoprophylaxis use against the likely adverse events generated. Overall numbers needed to prevent a malaria infection are comparable among the four options and are sensitive to changes in the background infection rates. Only a limited impact on the number of infections can be expected if Mq is substituted by AP.

Adherence to malaria prophylaxis among Peace Corps Volunteers in the Africa region, 2013

BACKGROUND

Although malaria can be prevented with prophylaxis, it is diagnosed in over 100 Africa-region Peace Corps Volunteers annually. This suggests that prophylaxis non-adherence is a problem in these non-immune travelers.

METHODS

We investigated Volunteers' knowledge, attitudes, and practices regarding prophylaxis using an internet-based survey during August 19-September 30, 2013. Adherence was defined as taking doxycycline or atovaquone-proguanil daily, or taking mefloquine doses no more than 8 days apart.

RESULTS

The survey was sent to 3248 Volunteers. Of 781 whose responses were analyzed, 514 (73%) reported adherence to prophylaxis. The most common reasons for non-adherence were forgetting (n = 530, 90%); fear of long-term adverse effects (LTAEs; n = 316, 54%); and experiencing adverse events that Volunteers attributed to prophylaxis (n = 297, 51%). Two hundred fourteen (27%) Volunteers reported not worrying about malaria. On multivariate analysis controlling for sex and experiencing adverse events Volunteers attributed to prophylaxis, the factor most strongly associated with non-adherence was being prescribed mefloquine (OR 5.4, 95% confidence interval 3.2-9.0).

CONCLUSIONS

We found moderate adherence and a prevailing fear of LTAEs among Volunteers. Strategies to improve prophylaxis adherence may include medication reminders, increasing education about prophylaxis safety and malaria risk, and promoting prompt management of prophylaxis side effects.

Summary of recommendations on malaria issues in special hosts

Background

On behalf of the Public Health Agency of Canada, the Committee to Advise on Tropical Medicine and Travel (CATMAT) developed the Canadian Recommendations for the Prevention and Treatment of Malaria Among International Travellers for Canadian health care providers who are preparing patients for travel to malaria-endemic areas and treating travellers who have returned ill.

Objective

To provide guidelines on malaria issues related to special hosts.

Methods

CATMAT reviewed all major sources of information on malaria prevention, as well as recent research and national and international epidemiological data, to tailor guidelines to the Canadian context. The evidence-based medicine recommendations were developed with associated rating scales for the strength and quality of the evidence.

Recommendations

All people visiting malaria endemic regions should use effective personal protective measures (PPM; topical repellants, bed nets, behavioural choices) and the prescribed chemoprophylaxis. Chemoprophylaxis for pregnant and breastfeeding women and for children requires careful consideration in the context of the pregnancy trimester, the age or size of the infant/child as well as their glucose-6-phosphate dehydrogenase (G6PD) status. Recommendations for long-term travellers, expatriates and people visiting friends and relatives (VFRs) do not differ markedly from those for short-term travellers. Some underlying medical conditions may make individuals more vulnerable to malaria. In addition, some conditions or their treatment may preclude the use of one or more antimalarial medications.

Idiosyncratic quinoline central nervous system toxicity: Historical insights into the chronic neurological sequelae of mefloquine

•

Regulators now warn adverse neurological effects from mefloquine may be irreversible.

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Many neurological effects resemble those of a common quinoline CNS toxidrome.

•

The quinoline toxidrome is associated with a risk of CNS neuronal degeneration.

•

CNS neuronal degeneration may underlie some neurological effects from mefloquine.

Mefloquine is a quinoline derivative antimalarial which demonstrates promise for the treatment of schistosomiasis. Traditionally employed in prophylaxis and treatment of chloroquine-resistant Plasmodium falciparum malaria, recent changes to the approved European and U.S. product labeling for mefloquine now warn of a risk of permanent and irreversible neurological sequelae including vertigo, loss of balance and symptoms of polyneuropathy. The newly described permanent nature of certain of these neurological effects challenges the conventional belief that they are due merely to the long half-life of mefloquine and its continued presence in the body, and raises new considerations for the rational use of the drug against parasitic disease. In this opinion, it is proposed that many of the reported lasting adverse neurological effects of mefloquine are consistent with the chronic sequelae of a well characterized but idiosyncratic central nervous system (CNS) toxicity syndrome (or toxidrome) common to certain historical antimalarial and antiparasitic quinolines and associated with a risk of permanent neuronal degeneration within specific CNS regions including the brainstem. Issues in the development and licensing of mefloquine are then considered in the context of historical awareness of the idiosyncratic CNS toxicity of related quinoline drugs. It is anticipated that the information presented in this opinion will aid in the future clinical recognition of the mefloquine toxidrome and its chronic sequelae, and in informing improved regulatory evaluation of mefloquine and related quinoline drugs as they are explored for expanded antiparasitic use and for other indications.

Effectiveness of short prophylactic course of atovaquone-proguanil in travelers to sub-saharan Africa

BACKGROUND

Current guidelines recommend continuation of atovaquone-proguanil (AP) malaria prophylaxis for 7 days after leaving Plasmodium falciparum endemic areas. Evidence from clinical studies suggests that discontinuation of AP 1 day after exposure ends may be safe and effective. Our objective was to assess the effectiveness of short-course AP prophylaxis among travelers to sub-Saharan Africa.

METHODS

To detect prophylactic failures associated with short-course AP prophylaxis discontinued 1 day after return, we conducted active surveillance during the years 2010 and 2011, by a retrospective telephone survey 1 to 6 months after travelers' return. Passive surveillance data were obtained from the Israel Ministry of Health (MOH) malaria registry.

RESULTS

Among 485 travelers to sub-Saharan Africa (cumulative exposure of 4,979 days), 421 (87%) discontinued AP 1 day after leaving the endemic region (cumulative exposure of 4,337 days). None of the 485 travelers reported malaria infection. The MOH malaria registry survey included 363 P. falciparum-infected patients during the years 2003 to 2011. The majority (n = 305; 84%) did not use any malaria prophylaxis. None of the patients had used AP (neither regular nor short course AP) for malaria prophylaxis.

CONCLUSIONS

We did not detect prophylaxis failures among a group of travelers who discontinued AP prophylaxis 1 day after leaving malaria-endemic areas. Passive surveillance in Israel did not detect any P. falciparum cases among AP users. We recommend further validation of our findings by clinical trials, prospective studies, and active surveillance in larger cohorts to assess the effectiveness of short-course AP prophylaxis in travelers.

A retrospective analysis of the protective efficacy of tafenoquine and mefloquine as prophylactic anti-malarials in non-immune individuals during deployment to a malaria-endemic area

Background

In 2000/2001, the Australian Defense Forces (ADF), in collaboration with SmithKline Beecham and the United States Army, conducted a field trial to evaluate the safety, tolerability and efficacy of tafenoquine and mefloquine/primaquine for the prophylaxis of malaria amongst non-immune Australian soldiers deployed to East Timor (now called Timor Leste) for peacekeeping operations. The lack of a concurrent placebo control arm prevented an internal estimate of the malaria attack rate and so the protective efficacy of the study regimens was not determined at the time.

Methods

In a retrospective analysis of the trial results, the all species malaria attack rate was estimated for the prophylactic phase of the study which was defined as the period between administration of the first prophylactic dose and the first dose of post-deployment medication. First, the Plasmodium vivax attack rate was estimated during the prophylactic phase of the deployment by adjusting the observed P. vivax relapse rate during post-deployment to account for the known anti-relapse efficacies (or effectiveness) of the study medications (determined from prior studies). The all species malaria attack rate (P. vivax and Plasmodium falciparum) was then determined by adjusting the P. vivax attack rate based on the ratio of P. falciparum to P. vivax observed during prior ADF deployments to Timor Leste. This estimated all species malaria attack rate was then used as the ‘constant estimated attack rate’ in the calculation of the protective efficacy of tafenoquine and mefloquine during the prophylactic phase of the deployment.

Results

The estimated attack rate during the prophylactic phase of the study was determined to be 7.88%. The protective efficacies of tafenoquine and mefloquine, with corresponding 95% confidence intervals (95% CI), were determined to be 100% (93%-100%) and 100% (79%-100%) respectively.

Conclusions

The protective efficacy of tafenoquine (200 mg per day for three days, followed by weekly 200 mg maintenance doses) is similar to that of the weekly standard of care (mefloquine, 250 mg).

Paediatric travel medicine: vaccines and medications

The paediatric aspects of travel medicine can be complex, and individual advice is often required. Nonetheless, children are much more likely to acquire common infections than exotic tropical diseases whilst travelling. Important exceptions are malaria and tuberculosis, which are more frequent and severe in children. Overall, travellers' diarrhoea is the most common illness affecting travellers. This review discusses vaccines and medications that may be indicated for children who are travelling overseas. It focuses on immunizations that are given as part of the routine schedule, as well as those that are more specific to travel. Malaria and travellers' diarrhoea are also discussed.

Epilepsy triggered by mefloquine in an adult traveler to Uganda

We report a case of a traveler who visited Uganda for 8 d, and took mefloquine one tablet/week for malaria prophylaxis. After the second dose, he suffered from two episodes of loss of consciousness with seizures, therefore mefloquine was discontinued. During the flight back after full recovery, seizures reoccurred while he was on board, he was disembarked in Addis Ababa and then transferred to Nairobi. After repatriation to Italy, he experienced four other similar episodes. The patient was still on full dose anticonvulsant therapy one year and a half after, as any attempt at reduced dose was unsuccessful. Currently, three agents (mefloquine, atovaquone/proguanil, and doxycycline) are recommended for malaria chemoprophylaxis, with similar efficacy but different adverse event profiles, regimens, and prices. Considering that mefloquine is associated with a higher risk of neurologic and psychiatric adverse events than the alternative regimens, we suggest considering mefloquine as a second line choice after atovaquone/proguanil and doxycycline for short-term travelers.

Malaria chemoprophylaxis: when should we use it and what are the options?

Malaria chemoprophylaxis concerns prescribing healthy individuals medication for an infection they have an unknown chance of getting. Sensible use of malaria chemoprophylaxis is a balance between the risk of infection and death, and the risk of side effects. The risk of infection can be broken down into the risk of being bitten by a malaria-infected mosquito and the risk of the malaria parasites being resistant to the drug used for prophylaxis. Our knowledge of these parameters is patchy. The risk of infection is not uniform at a given location and the standard of living will greatly influence risk. It is suggested that chemoprophylaxis should not be recommended in areas with less than ten reported cases of P. falciparum malaria per 1000 inhabitants per year. The resistance pattern is known to a certain extent but, for instance, diverging opinion of how much resistance to chloroquine there is in West Africa illustrates the lack of data. There is much debate on rare adverse events, which usually escape Phase III studies prior to registration and are only picked up by passive, postmarketing surveillance. The lessons over the past 20 years with the introduction of amodiaquine, pyrimethamine/dapsone (Maloprim, GlaxoSmithKline) and pyrimethamine/sulfadoxine (Fansidar, Roche), which were all withdrawn for prophylaxis after a few years, show how sensitive drugs for chemoprophylaxis are to side effects. Three levels of chemoprophylaxis are used: chloroquine in areas with sensitive P. falciparum, chloroquine plus proguanil in areas with low level chloroquine resistance, and atovaquone/proguanil (Malarone, GlaxoSmithKline), doxycycline or mefloquine (Lariam, Roche) in areas with extensive resistance against chloroquine and proguanil. Primaquine and the primaquone analog tafenoquine may be future alternatives but otherwise there are few new drugs for chemoprophylaxis on the horizon.

Health hazards and medical treatment of volunteers aged 18-30 years working in international social projects of non-governmental organizations (NGO)

The specific health risk profile and diversity of treatments sought by young volunteers participating in international social projects should differ from those of their older colleagues. In the absence of any data to identify whether this was correct, a retrospective analysis was performed using a standardized questionnaire. Questions included what diseases occurred, and details of the frequency and types of treatment sought during their stay - (e.g. self-treatment, medical/dental intervention, or local healer). The 153 participants were aged 18-30 years and worked in a non-governmental organization for >6 months. The participants were: 53% female, mean age 20 years, and mean duration of stay was 11.2 months. Their NGO placement abroad was in Latin America 65.4%, 14.4% in Africa, and 9.8% in Asia. 83% of the young volunteers had received some advice regarding travel medicine before their departure. However, they suffered from more injuries compared to private travellers, and febrile infections were more common when compared to older studies. 21.2% suffered from dental problems and 50% of them sought medical treatment. This study highlights a previously unreported higher risk profile of specific health problems occurring in young NGO volunteers, including some potentially life-threatening diagnoses that differed from their older colleagues and normal travellers. It is recommended that young volunteers should receive age specific, comprehensive pre-departure training in health and safety, first aid, and management of common health problems. A medical check-up upon returning home should be mandatory. The provision of a basic first aid kit to each volunteer before departure is also recommended.

Severity of imported malaria: protective effect of taking malaria chemoprophylaxis

Background

Although chemoprophylaxis remains an important strategy for preventing malaria in travellers, its effectiveness may be compromised by lack of adherence. Inappropriate use of chemoprophylaxis is likely to increase the risk of acquiring malaria, but may probably also worsen the severity of imported cases. The aim of this study was to assess the impact of use of malaria chemoprophylaxis on clinical features and outcome of imported malaria.

Methods

Demographic, clinical and laboratory data of patients included in the Rotterdam Malaria Cohort between 1998 and 2011 were systematically collected and analysed. Patients were classified as self-reported compliant or non-compliant users or as non-users of chemoprophylaxis. Severe malaria was defined using the 2010 WHO criteria.

Results

Details on chemoprophylaxis were available for 559 of the 604 patients, of which 64.6% were non-users, 17.9% were inadequate users and 17.5% reported to be adequate users. The group of non-users was predominated by patients with African ethnicity, partial immunity and people visiting friends and relatives. The majority contracted Plasmodium falciparum malaria. In contrast, compliant users acquired non-falciparum malaria more frequently, had significant lower P. falciparum loads on admission, shorter duration of hospitalization and significant lower odds for severe malaria as compared with non-users. Patients with P. falciparum malaria were more likely to have taken their chemoprophylaxis less compliantly than those infected with non-P. falciparum species. Multivariate analysis showed that self-reported adequate prophylaxis and being a partially immune traveller visiting friends and relatives was associated with significantly lower odds ratio of severe malaria. In contrast, age, acquisition of malaria in West-Africa and being a non-immune tourist increased their risk significantly.

Conclusions

Compliant use of malaria chemoprophylaxis was associated with significantly lower odds ratios for severe malaria as compared with non-compliant users and non-users of chemoprophylaxis. After correction for age, gender and immunity, this protective effect of malaria chemoprophylaxis was present only in individuals who adhered compliantly to use of chemoprophylaxis. Patients with P. falciparum malaria were more likely to have used their chemoprophylaxis less compliantly than patients with non-P. falciparum malaria who were more likely to have contracted malaria in spite of compliant use of chemoprophylaxis.

Adherence to chemoprophylaxis and Plasmodium falciparum anti-circumsporozoite seroconversion in a prospective cohort study of Dutch short-term travelers

Background

We conducted a prospective study in a cohort of short-term travelers assessing the incidence rate of anti-circumsporozoite seroconversion, adherence to chemoprophylaxis, symptoms of malaria during travel, and malaria treatment abroad.

Methods

Adults were recruited from the travel clinic of the Public Health Service Amsterdam. They kept a structured daily travel diary and donated blood samples before and after travel. Blood samples were serologically tested for the presence of Plasmodium falciparum anti-circumsporozoite antibodies.

Results

Overall, the incidence rate (IR) of anti-circumsporozoite seroconversion was 0.8 per 100 person-months. Of 945 travelers, 620 (66%) visited high-endemic areas and were advised about both chemoprophylaxis and preventive measures against mosquito bites. Most subjects (520/620 = 84%) took at least 75% of recommended prophylaxis during travel. Travel to Africa, use of mefloquine, travel duration of 14–29 days in endemic areas, and concurrent use of DEET (N,N-diethyl-meta-toluamide) were associated with good adherence practices. Four travelers without fever seroconverted, becoming anti-circumsporozoite antibody-positive. All four had been adherent to chemoprophylaxis; two visited Africa, one Suriname, one India. Ten subjects with fever were tested for malaria while abroad and of these, three received treatment. All three were adherent to chemoprophylaxis and tested negative for anti-circumsporozoite antibodies.

Conclusion

Travel to Africa, using mefloquine, travel duration of 14–29 days in endemic areas, and use of DEET were associated with good adherence to chemoprophylaxis. The combination of chemoprophylaxis and other preventive measures were sufficient to protect seroconverting travelers from clinical malaria. Travelers who were treated for malaria abroad did not seroconvert.

Compliance with antimalarial chemoprophylaxis in German soldiers: a 6-year survey

PURPOSE

Since 1992, German soldiers have been deployed in areas where malaria is endemic. Antimalarial chemoprophylaxis (CP) is directed according to the assessed risk and is provided free of charge. Compliance is crucial if its effect is to be reliable. This study analysed compliance with directed CP in German soldiers as well as its determinants.

METHODS

Between 2003 and 2009, standardized questionnaire-based interviews were performed with 2,149 out of approximately 100,000 German soldiers who were deployed during this period in areas where malaria is endemic. The questionnaires dealt with information that the soldiers had received about malaria prior to their missions, with their adherence to mosquito-protective and antimalarial chemoprophylactic procedures, and their estimations of their individual level of exposure.

RESULTS

About 1,308 out of 2,149 interviewed soldiers had been ordered to take CP, allowing for an assessment of the outcome parameter "CP-compliance". About 76.9 % out of 1,308 soldiers to whom regular CP was directed took it regularly. The exposure variables "age", "satisfaction with malaria counselling", "perceived threat due to insects or mosquitoes" and "use of insect repellents" were positively associated with compliance with directed antimalarial CP.

CONCLUSIONS

The study confirms the findings of the French and US armies that even free-of-charge access to antimalarial medication will not lead to 100 % acceptance. The compliance problem is aggravated by the generally low age of deployed soldiers. Adequate counselling is crucial to increase adherence to antimalarial CP.