Low frequency of complications in imported falciparum malaria: a review of 222 cases in south-eastern Norway.

We performed a retrospective study of 222 cases of falciparum malaria diagnosed in Oslo and Akerhus counties, Norway, from January 1988 to December 1997. Except for 12 cases, all had acquired the disease in sub-Saharan Africa. Sixty-four (28.8%) cases occurred in assumed non-immune individuals; of these, 41 (64.1%) were compliant to recommended antimalarial chemoprophylaxis. The mean time lag from first symptom to diagnosis (total diagnosis delay) was 4.6 d (median 3 d, range 0-30 d) and the mean time from presentation to diagnosis (doctor's delay) was 1.3 d (median 0 d, range 0-25 d). There were no fatal cases, and only 8 (3.6%) had a complicated course. The following factors were significantly associated with development of complicated disease: higher age, non-immunity combined with chemoprophylaxis non-compliance, prolonged doctor's delay and prolonged total diagnosis delay (p < or = 0.05). Our data suggest that complicated disease in imported falciparum malaria may largely be prevented by high chemoprophylaxis compliance rates in non-immune travellers and a high index of suspicion in physicians evaluating febrile travellers.     

Epidemiological features and case management practices of imported malaria in northern Italy 1991-1995

We report the results of a retrospective analysis of the clinical charts of imported malaria cases notified during the period 1991-95 in the Lombardy region of northern Italy. We analysed 694 admissions related to 683 individuals. The proportion of immigrants increased during the observation period from 34.4% in 1991 to 59.9% in 1995 (P = 0.002). P. falciparum was the causative species in 534 cases (78. 2%), and 591 (90.1%) of 656 cases with a full travel history had travelled to Africa. Information on chemoprophylaxis was available in 604 cases: 429 (71.0%) reported no drug intake, 140 (23.2%) an incomplete, and 35 (5.8%) a complete chemoprophylactic course. The proportion of subjects who had initiated malaria chemoprophylaxis was significantly lower among immigrants (7.4%) than nonimmigrants (50.2%) (P < 0.001). Severe disease was diagnosed in 26 (4.7%) of 551 cases of falciparum malaria, with a significantly lower incidence among immigrants (1.3% vs. 9.2%; P < 0.001). Eight deaths were recorded, all among nonimmigrants, whose fatality rate was significantly higher (P = 0.02). Mefloquine treatment of cases of uncomplicated falciparum malaria was associated with a significantly shorter fever clearance time (2.8 days +/- 1.5 vs. 3.5 days +/- 1.9; P < 0.001) and mean hospital stay (5.9 days +/- 4.4 vs. 8.3 days +/- 5.1; P < 0.001) compared to quinine treatment.     

Malaria in Leicester 1983-1988: a review of 114 cases

We have reviewed 114 episodes of malaria in 110 patients who were admitted to the Infectious Diseases Unit in Leicester during the 5 year period from February 1983-January 1988. There were 71 episodes of vivax malaria (62%), 33 episodes of falciparum malaria (29%), four patients with mixed infection and six patients with negative blood films who were diagnosed on clinical suspicion alone. Most patients presented in the summer months, 68% were aged under 40 years, 39% were born in the Indian subcontinent, 23% in East Africa and 23% in Britain. Eighty-two per cent of patients with falciparum malaria had recently returned from Africa whereas 82% with vivax malaria had visited Asia. Thirty six per cent had been given antimalarial chemoprophylaxis but only half of these took medication correctly. Seventy five per cent of episodes of falciparum malaria presented within 2 weeks of arrival in Britain, however vivax malaria could present at any time and 49% of cases occurred over 3 months after exposure. Presenting symptoms and signs were often non-specific. Twenty nine per cent of patients had been treated with antibiotics and 11% received antimalarials prior to admission. Vivax malaria was generally a mild infection but falciparum malaria was often severe with 39% of patients experiencing complications including one death. Although Plasmodium vivax and P. falciparum are morphologically similar the diseases caused by the two species of parasite are quite distinct. Physicians must ensure that malaria is excluded in anyone who has travelled to an endemic area.     

Halofantrine for the treatment of mefloquine chemoprophylaxis failures in Plasmodium falciparum infections

Thai soldiers who became slide-positive for malaria while receiving mefloquine chemoprophylaxis were treated with halofantrine to study its efficacy against mefloquine-resistant falciparum malaria. Thirty-two patients received three doses of 500 mg (1,500 mg total) of halofantrine at six-hr intervals, and were then observed for four weeks. Parasite recrudescence following treatment (median 21 days) occurred in seven of 23 patients (30%) who had mefloquine serum concentrations indicative of regular prophylaxis (greater than 500 ng/ml). Serum concentrations of mefloquine in all 32 patients averaged 950 ng/ml (range 26-2,515) prior to halofantrine treatment. The halofantrine serum concentrations were higher in patients cured by halofantrine than in patients with drug failure, but this was not statistically significant. Patients who were cured by halofantrine had parasites that were more sensitive in in vitro testing to mefloquine (mean [inhibitory concentration] IC50 = 12.5 ng/ml) than in patients whose parasitemias recrudesced (mean IC50 = 23.8 ng/ml) (P less than 0.01, by Wilcoxon rank sum test). These observations suggest that the current formulation and regimen of halofantrine are not optimal for the treatment of multiple drug-resistant falciparum malaria from Thailand.     

Imported malaria in a Singapore hospital: clinical presentation and outcome.

OBJECTIVE: To evaluate the clinical presentation and outcome of imported malaria. METHODS: A retrospective chart review was conducted of patients with imported malaria admitted to the Communicable Disease Centre (CDC), Singapore (a 130-bed tertiary referral center) from January 1992 to December 1993. An imported case was defined as a smear-positive infection that was acquired in another country. RESULTS: Among 200 malaria patients hospitalized at CDC, 168 imported cases (137 males and 31 females, 131 nonresidents and 37 residents) were studied. The mean age was 31.6 6 10.5 years. The countries visited were India (49.4%), Indonesia (16.7%), and Bangladesh (13%). Five patients had chemoprophylaxis and 36 patients had experienced previous malaria infection. The predominant symptoms were fever (97.6%), chills (79.2%), and rigors (67.9%). Hepatomegaly was detected in 56 (33.3%) and splenomegaly in 49 patients (29.2%). Plasmodium vivax was present in 132 patients, Plasmodium falciparum in 29, and mixed P. vivax and P. falciparum in 7 patients. Parasitemia ranged from 0.1% to 8.0%. Of the vivax cases, 130 were treated with chloroquine, followed by primaquine in 123 patients. Quinine was given to 36 patients (29 falciparum malaria and 7 mixed infections). Median time to fever defervescence was 2 days. Complications occurred in three patients (2 with shock and 1 with pulmonary edema). According to World Health Organization gravity criteria, body temperature over 40 degrees C was detected in six patients, bilirubinemia higher than 50 mmol/L in nine, parasitemia over 5% in five, glycemia less than 2.2 mmol/L in two patients. There were five relapses. No death was recorded. CONCLUSION: Plasmodium vivax is the most common cause of imported malaria, with the majority acquired from the Indian subcontinent. Only a few patients presented with severe malaria.     

An outbreak of Plasmodium vivax malaria in Kyrghyzstan

Malaria was not notified in the republic in 1960 to 1982, with exception of 1963 where one case of imported malaria was identified. Twenty-four cases of locally transmitted malaria were detected, 11 of them being registered in the Batken district, Osh Region, contiguous with Tadjikistan and Uzbekistan. In 1981 to 2000, a total of 101 cases of malaria were notified, in 2001 there was an increase in cases of malaria to 136, while in 2002, a total of 2744 cases of malaria were registered mainly in the Fergana valley. Malaria was imported from Tadjikistan, Azerbaijan, Uzbekistan, and Afghanistan. The infectious agent of malaria was P. vivax in 98% of cases and P. falciparum in 2%. The high malarial potential areas are the Osh, Zhalalabat, and Batken Regions and town of Osh. In 2002, the investigators identified patients with malaria, made its chloroquine eliminating treatment, seasonal chemoprevention of some 5000 dwellers of the Leilek District of the Batken Region contiguous with Tadjikistan, and larvicidal treatments of water reservoirs and rice checks with dimilin. Almost 1,988,000 m2 of premises were treated with Solfac. Mosquito fishes were placed into more water reservoirs in 2003. In 2003 there was a tendency for a decrease in the incidence of malaria, as compared with 2002, which may be ascribed to the small size of vectors, which is due to the cold spring and cool June and July. In 2003, there were treatments of premises, mosquito fish enrichment of water reservoirs, interseasonal chemoprophylaxis of patients who experienced malaria in 2002; impregnated bed curtains were available to protect the dwellers of foci from mosquito bites.     

Urban malaria in Dakar, Senegal: chemosusceptibility and genetic diversity of Plasmodium falciparum isolates

The chemosusceptibility and genetic polymorphism of Plasmodium falciparum populations from 48 patients hospitalized for malaria at the Hospital Principal in Dakar, Senegal were investigated during the 2002 malaria transmission season. Sixty-two percent of the isolates collected were from patients with severe malaria and 38% were from patients with mild malaria. In vitro activities of chloroquine, quinine, cycloguanil, atovaquone, mefloquine, halofantrine, and artesunate were evaluated. The prevalence of mutations in the Plasmodium falciparum dihydrofolate reductase (dhfr) and dihyropteroate synthetase (dhps) genes and the P. falciparum chloroquine resistance transporter (Pfcrt) gene associated with cycloguanil, pyrimethamine, sulfadoxine, and chloroquine resistance were estimated. The genetic polymorphism of the parasite populations was evaluated by analysis of the highly polymorphic regions of merozoite surface protein 1 (msp1) block 2 and msp2. Seventy percent of the isolates were assessed by an in vitro assay. Fifty-two percent of the isolates were chloroquine resistant, 45% were cycloguanil resistant, and 24% were atovaquone resistant. Four percent had low susceptibility to quinine. The Pfcrt and dhfr mutations were associated with in vitro chloroquine- and antimetabolic drug-resistant isolates, respectively. Approximately 70% of the isolates contained two or more clones. Genetic diversity of P. falciparum was high. The prevalence of allelic family K1 of msp1 was 68%. Isolates of P. falciparum were highly resistant to chloroquine, cycloguanil and atovaquone. The transmission rate of malaria in Dakar is low but a high degree of genetic polymorphism can increase severe malaria, as shown by persons coming to Dakar from areas highly endemic for malaria. Areas with urban malaria should use vector control measures and efficient chemoprophylaxis for non-immune populations.     

Serum procalcitonin in uncomplicated falciparum malaria: a preliminary study

BACKGROUND: Procalcitonin (PCT) has been found elevated in complicated forms of Plasmodium falciparum malaria. Its usefulness has almost never been assessed in uncomplicated falciparum malaria. METHOD: We assessed diagnostic and prognostic value of PCT in a prospective series of 25 adults with uncomplicated P. falciparum malaria. Patients originated mainly from western Africa and were infected during a stay back in their native country (19 semi-immune and 6 non-immune subjects; 11 had not received any chemoprophylaxis). RESULTS: Parasitaemia ranged from 0.01 to 3%. Eighteen patients had their first PCT determined at admission or within 24h thereafter (mean +/- SD: 3.0 +/- 4.6 ng/ml; range: 0.1-19.7). PCT was higher than 0.5 ng/ml in 14 patients (78%), higher than 2 ng/ml in 7 (39%). PCT correlated with parasitaemia (r = 0.53; p = 0.027), not with C-reactive protein (CRP). Delay between first symptoms and diagnosis was much longer among patients with PCT higher than 2 ng/ml than among those with a lower PCT. CONCLUSION: PCT was often elevated in uncomplicated malaria, especially when delay between first symptoms and diagnosis was long or parasitaemia was high (prognostic marker).     

Malaria: 30 years of experience at a New York City teaching hospital

Two previous reviews summarized the New York Hospital experience with 110 cases of malaria from 1968 to 1990. We have extended these studies to include 59 cases of malaria seen from 1991 to 1999 and analyze trends over the past 30 years. Plasmodium falciparum remains the most common species, 38 (64%) of the 59 cases, with the majority of them, 34 (89%) of 38 cases, being acquired in Africa. Of the 59 cases, 22 (37%) were immigrants living in the United States who had visited their countries of origin. Only five (8%) of 59 patients reported using chemoprophylaxis. This represents a marked decrease from the previous reviews. None of the immigrants or their children used chemoprophylaxis. Diagnosis was prompt, and patients responded well to therapy. Complications of malaria were low and no deaths were reported, as was the case in the previous reviews. The low use of chemoprophylaxis, particularly among immigrants, is a major concern.     

Ideal treatment of malaria attack: more questions than answers? Experience of a department of infectious diseases

The number of cases of malaria imported to western Europe from tropical areas is steadily growing, due to the increased number of people traveling to endemic regions and to the spread of Plasmodium strains resistant to chemoprophylaxis. This has prompted the WHO to frequently update its guidelines concerning preventive therapy. We report on 143 consecutive cases of benign attacks of malaria in patients returning primarily from western and central Africa. Plasmodium falciparum was responsible for 80% of the cases. Forty-one percent of the patients had followed their preventive regimen correctly; mefloquine failed in 3 of them. Three early relapses were observed after curative treatment, including 2 patients who had received intravenous quinine for more than 5 days. Because P. falciparum infection is potentially lethal, we suggest that the treatment of malaria attacks be optimized, by systematically dosing serum quinine levels, in order to adjust the administered doses, and, as a first-line therapy, by prescribing a combination of drugs to patients at high risk of resistance.     

Malaria chemoprophylaxis using proguanil/dapsone combinations on the Thai-Cambodian border.

The Thai-Cambodian border is a difficult area in which to provide adequate malaria chemoprophylaxis because of multiple drug-resistant Plasmodium falciparum. In 1990-1991, Thai soldiers were randomly selected to receive proguanil (200 mg/day) combined with dapsone (4 mg or 12.5 mg/day) (n = 184) or pyrimethamine/dapsone (12.5 mg and 100 mg/week) (n = 177). Doxycycline (100 mg/day) was given to men with glucose-6-phosphate dehydrogenase deficiency (n = 77). Falciparum malaria attack rates were the same whether proguanil/dapsone (10.3%) or pyrimethamine/dapsone (11.3%) was used. However, proguanil/dapsone was more effective than pyrimethamine/dapsone in preventing vivax malaria (1.6% versus 12.4%). Men receiving doxycycline had falciparum malaria (3.9%) and vivax malaria (1.3%) at low rates. Adjusting the dapsone component from 4 mg to 12.5 mg did not improve the prophylactic effectiveness. Hematologic toxicity was not observed with the proguanil/dapsone combination. We conclude that proguanil/dapsone is not a useful alternative for malaria chemoprophylaxis on the Thai-Cambodian border.     

Clinical characteristics of imported malaria in Japan: analysis at a referral hospital

Imported malaria remains an important problem in Japan. We have reviewed the medical records of 170 cases of malaria in our hospital, which corresponds to 14.9% of the total cases in Japan. The predominant malarial species was Plasmodium falciparum (52.3%), and the most frequent area of acquisition was Africa (54.2%), followed by Asia (20.9%) and Oceania (19.6%). The most common reason for travel among Japanese patients was business. A significant proportion (22.2%) of vivax malaria cases experienced relapse despite standard primaquine therapy. Most primaquine failures were from Oceania. We also found that a substantial number of Japanese patients contracted malaria without chemoprophylaxis and consulted medical facilities with an unfavorably long delay from initial symptoms (median: 3.0 days). Direct education of travelers and travel companies, in addition to health care providers, is likely necessary to improve outcomes of imported malaria.     

Malaria chemoprophylaxis with chloroquine in young Nigerian children. I. Its effect on mortality, morbidity and the prevalence of malaria

One hundred and ninety-eight Nigerian children who received weekly chemoprophylaxis with chloroquine from shortly after birth until the age of one year or two years and 185 age-matched controls were studied. Chemoprophylaxis with chloroquine was partially, but not completely, effective in controlling malaria. Clinical malaria was documented significantly less frequently in protected children than in control children, and only 9% of random blood films obtained from protected children were positive for Plasmodium falciparum while 41% of random blood films from control children were positive for this parasite. Mean malaria antibody levels were lower in protected than in control children; for ELISA and precipitin antibodies the difference between the two groups was less marked at two years than at one year. Mortality was similar among protected and among control children. No rebound mortality or morbidity was observed after chemoprophylaxis was stopped.     

Efficacy of malaria prophylaxis in American and Swiss travelers to Kenya

The protective effect of malaria chemoprophylaxis with either Fansidar (pyrimethamine-sulfadoxine) or chloroquine was estimated by determining the attack rates of Plasmodium falciparum infections acquired in Kenya and imported by U.S. and Swiss travelers who had used no chemoprophylaxis, who had used only chloroquine for prophylaxis, and who had used Fansidar weekly, either alone or in combination with chloroquine. The estimated attack rates were almost identical in U.S. and Swiss travelers. The attack rate per 100,000 travelers averaged 280 in those who did not use chemoprophylaxis, 162 in those who took 4-aminoquinolines (P greater than .05), and 27 in those who used Fansidar for prophylaxis (P less than .001). Non-immune travelers to Kenya have an appreciable risk of acquiring a P. falciparum infection and need to be informed of current guidelines for chemoprophylaxis. The changing drug susceptibility patterns in Africa require continuous evaluation of the efficacy of recommended drug regimens for malaria prophylaxis.     

High case-fatality from falciparum malaria in UK travellers returning from The Gambia: a case series

BACKGROUND: Following two deaths from falciparum malaria in UK travellers returning from The Gambia, we investigated the epidemiology of cases during part of the "winter sun" season in 2005/2006. METHOD: We obtained data on laboratory-confirmed cases of falciparum malaria (diagnosed 1.11.2005 to 31.1.2006) in travellers returning from The Gambia. Information on prophylaxis and deaths, for all Gambia associated cases from 2000 to 2004, and for cases from all countries between 1.11.2005 and 31.10.2006 (excluding series cases), was used for comparison. We obtained Gambian tourist figures from the World Tourism Organisation. RESULTS: Twenty-six cases of falciparum malaria were identified between 1.11.05 and 31.1.06 (32 during the entire year), of whom three died and seven required intensive care. Twenty cases (80%) were on holiday, and half the year's cases were diagnosed in December. Of the 24/26 where it was determined, half had taken no prophylaxis and half had taken inadequate prophylaxis. The annual risk was 75 per 100,000 charter flight passengers. CONCLUSIONS: Compliance with chemoprophylaxis was poor and the case-fatality rate high (11.5% vs. 3.8% in 2000-2004). A clear message emphasising the importance of chemoprophylaxis, bite avoidance and prompt diagnosis was disseminated to clinicians, public and the travel industry.     

Parasite multiplication potential and the severity of Falciparum malaria

The multiplication rates and invasiveness of Plasmodium falciparum parasites isolated from adult Thai patients hospitalized with uncomplicated malaria (n=34) were compared with those from persons with severe malaria (n=42). To simulate severe malaria and control for host effects, the in vitro cultures were adjusted to 1% parasitemia and used the same red blood cell donor. P. falciparum isolates from persons with severe malaria had initial cycle multiplication rates in vitro that were 3-fold higher than those from uncomplicated malaria (median [95% confidence interval], 8.3 [7. 1-10.5] vs. 2.8 [1.7-3.9]; P=.001). Parasites causing severe malaria exhibited unrestricted red blood cell invasion, whereas those from uncomplicated malaria were restricted to a geometric mean of 40 (31%-53%) of red blood cells. P. falciparum parasites causing severe malaria were less selective and multiplied more at high parasitemias than those causing uncomplicated malaria.     

Chloroquine concentration profile in the community of Mewat region, district Gurgaon (Haryana), India

A survey was conducted to find chloroquine concentration profile in the community of Mewat region district Gurgaon (Haryana) of India. 88 P. falciparum and 3 P. vivax cases were detected out of 148 blood slides examined with a SPR of 61.48. Plasma chloroquine and desethylchloroquine concentrations were determined in 55 P. falciparum and 2 P. vivax patients and 29 persons whose blood slides were negative for malaria parasite before giving any treatment. Mean chloroquine concentrations in cases with P. falciparum parasites and without malaria parasites were 0.018 and 0.016 microg ml(-1) respectively. Chloroquine to desethyl chloroquine ratio was between 2 and 3 in both groups. Only 10 malaria parasite negative cases out of 29 had plasma chloroquine concentrations above 0.016 microg ml(-1) required for malaria chemoprophylaxis. Chloroquine was undetectable in plasma samples of 8 out of 55 P. falciparum cases. Chloroquine plasma concentrations in 21 P. falciparum cases were below therapeutically effective concentration of 0.016 microg ml(-1) suggesting improper treatment while in 29 P. falciparum cases, parasitemia recurred despite required chloroquine concentration confirming chloroquine resistant status. Irregular prophylaxis and lack of proper treatment was one of the major causes of malaria outbreak in this area.     

清远市清城区输入性疟疾病例分析及防控对策探讨

目的分析2011-2016年清远市清城区输人性疟疾病例特点并探讨防控对策,为进一步提高输入性疟疾诊治能力和管理水平提供参考依据。方法回顾性分析2011-2016年该区所有输入性疟疾病例的个案调信息和流行病学资料,对境外输入性病例的虫种、来源、人群分布、地区分布、发病及诊治情况等进行描述性分析。结果 2011-2016年清城区报告输入性疟疾病例13例,其中恶性疟9例、间日疟1例、恶性疟间日疟混合感染2例、卵型疟再燃复发1例。年度输入性疟疾病例总数呈上升趋势,病例输入来源地均为非洲,报告时间主要在1-2、11、12月,占总病例数的84.62%(11/13),患者均为男性,以21~60岁为主,占病例总数的92.31%(12/13);前往非洲疟疾流行区从事野外作业务工人员是输入性疟疾的高危人群。13例输入性疟疾病例均为实验室确诊,患者从发病到初次就诊时间中位数为2.5 d,最长为19 d;初诊到确诊时间中位数为1.9 d,最长为9 d;其中初诊诊断为其他疾病的有6例(46.15%),其中1例患者因延误诊治而死亡。结论清城区境外输入性疟疾病例呈上升趋势,需加强多部门合作,建立高危人群建立监测、协查和健康干预等防控机制,确保输入性疟疾病人得到有效救治。     

Compliance with malaria chemoprophylaxis and preventative measures against mosquito bites among Dutch travellers.

Summary Self-reported compliance with a malaria chemoprophylaxis regimen of proguanil (PG) plus chloroquine (CQ) was assessed in a cohort of 547 Dutch travellers who visited a single travel clinic when travelling to various areas endemic for falciparum malaria. 503 (92%) had taken PG/CQ prophylaxis, but only 326 (60%) reported regular and uninterrupted use throughout the journey and 4 weeks afterwards. Compliance differed by travel destination and was 45% in South America, 52% in West Africa, 53% in South-east Asia, 60% in the Indian Subcontinent and 78% in East Africa. Parasitologically confirmed falciparum malaria occurred in 5 travellers (0.9%), including 3 of 24 non-compliant travellers to West Africa (12.5%). Apart from destination, independent risk factors for non-compliance were young age, extensive travel experience and adventurous travel. Compliance with protection against mosquito bites was 80% for wearing long-sleeved shirts and long-legged trousers after sunset, 73% for use of repellents, 56% for sleeping under bednets and 37% for keeping the sleeping quarters free of mosquitoes. Although 440 travellers (80%) reported to have taken two or more of these measures at least once, only 88 (16%) had done so on a daily basis. Daily use of bednets was reported more frequently among subjects who were non-compliant with chemoprophylaxis. Compliance regarding malaria chemoprophylaxis should be improved, particularly in high-risk areas such as Sub-saharan Africa, with extra attention to young, adventurous travellers. More emphasis should be placed on prevention of Anopheles bites.     

The effect of chemoprophylaxis on the timing of onset of falciparum malaria

The association between chemoprophylaxis and delayed onset of falciparum malaria was investigated in a retrospective study of 477 nonimmune cases reported to the UK Malaria Reference Laboratory (MRL) who had used either mefloquine (n = 56), chloroquine-proguanil (n = 90) or no chemoprophylaxis (n = 331). For holiday and short-term travellers using mefloquine the time between arrival in the UK and diagnosis was found to be significantly longer than for chloroquine and proguanil (C-P) users or for those who had not used prophylaxis at all (P < 0.004). This delay was primarily due to a later onset of symptoms. C-P use was not associated with delay in onset of symptoms or diagnosis when compared to not using prophylaxis. Possible reasons for the findings are discussed. Mefloquine may continue to exert a partially suppressive effect on resistant strains of Plasmodium falciparum (Pf). That chloroquine with proguanil was not found to have such an effect may be due to poor compliance to proguanil or differences in the mode of action and range of parasite resistance to the two regimens. Differences in drug compliance may be one reason why only mefloquine users on holiday or short-term journeys experienced delays to onset of disease. Drug compliance amongst cases of breakthrough malaria on chemoprophylaxis may be lower than is generally recognized. It is important for clinicians and travellers to be aware that the onset of falciparum malaria may be delayed by mefloquine prophylaxis.