Falciparum malaria in malaria-naive travellers and African visitors

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.

UK malaria treatment guidelines 2016

1.Malaria is the tropical disease most commonly imported into the UK, with 1300-1800 cases reported each year, and 2-11 deaths. 2. Approximately three quarters of reported malaria cases in the UK are caused by Plasmodium falciparum, which is capable of invading a high proportion of red blood cells and rapidly leading to severe or life-threatening multi-organ disease. 3. Most non-falciparum malaria cases are caused by Plasmodium vivax; a few cases are caused by the other species of plasmodium: Plasmodium ovale, Plasmodium malariae or Plasmodium knowlesi. 4. Mixed infections with more than one species of parasite can occur; they commonly involve P. falciparum with the attendant risks of severe malaria. 5. There are no typical clinical features of malaria; even fever is not invariably present. Malaria in children (and sometimes in adults) may present with misleading symptoms such as gastrointestinal features, sore throat or lower respiratory complaints. 6. A diagnosis of malaria must always be sought in a feverish or sick child or adult who has visited malaria-endemic areas. Specific country information on malaria can be found at http://travelhealthpro.org.uk/. P. falciparum infection rarely presents more than six months after exposure but presentation of other species can occur more than a year after exposure. 7. Management of malaria depends on awareness of the diagnosis and on performing the correct diagnostic tests: the diagnosis cannot be excluded until more than one blood specimen has been examined. Other travel related infections, especially viral haemorrhagic fevers, should also be considered. 8. The optimum diagnostic procedure is examination of thick and thin blood films by an expert to detect and speciate the malarial parasites. P. falciparum and P. vivax (depending upon the product) malaria can be diagnosed almost as accurately using rapid diagnostic tests (RDTs) which detect plasmodial antigens. RDTs for other Plasmodium species are not as reliable. 9. Most patients treated for P. falciparum malaria should be admitted to hospital for at least 24 h as patients can deteriorate suddenly, especially early in the course of treatment. In specialised units seeing large numbers of patients, outpatient treatment may be considered if specific protocols for patient selection and follow up are in place. 10. Uncomplicated P. falciparum malaria should be treated with an artemisinin combination therapy (Grade 1A). Artemether-lumefantrine (Riamet(®)) is the drug of choice (Grade 2C) and dihydroartemisinin-piperaquine (Eurartesim(®)) is an alternative. Quinine or atovaquone-proguanil (Malarone(®)) can be used if an ACT is not available. Quinine is highly effective but poorly-tolerated in prolonged treatment and should be used in combination with an additional drug, usually oral doxycycline. 11. Severe falciparum malaria, or infections complicated by a relatively high parasite count (more than 2% of red blood cells parasitized) should be treated with intravenous therapy until the patient is well enough to continue with oral treatment. Severe malaria is a rare complication of P. vivax or P. knowlesi infection and also requires parenteral therapy. 12. The treatment of choice for severe or complicated malaria in adults and children is intravenous artesunate (Grade 1A). Intravenous artesunate is unlicensed in the EU but is available in many centres. The alternative is intravenous quinine, which should be started immediately if artesunate is not available (Grade 1A). Patients treated with intravenous quinine require careful monitoring for hypoglycemia. 13. Patients with severe or complicated malaria should be managed in a high-dependency or intensive care environment. They may require haemodynamic support and management of: acute respiratory distress syndrome, disseminated intravascular coagulation, acute kidney injury, seizures, and severe intercurrent infections including Gram-negative bacteraemia/septicaemia. 14. Children with severe malaria should also be treated with empirical broad spectrum antibiotics until bacterial infection can be excluded (Grade 1B). 15. Haemolysis occurs in approximately 10-15% patients following intravenous artesunate treatment. Haemoglobin concentrations should be checked approximately 14 days following treatment in those treated with IV artemisinins (Grade 2C). 16. Falciparum malaria in pregnancy is more likely to be complicated: the placenta contains high levels of parasites, stillbirth or early delivery may occur and diagnosis can be difficult if parasites are concentrated in the placenta and scanty in the blood. 17. Uncomplicated falciparum malaria in the second and third trimester of pregnancy should be treated with artemether-lumefantrine (Grade 2B). Uncomplicated falciparum malaria in the first trimester of pregnancy should usually be treated with quinine and clindamycin but specialist advice should be sought. Severe malaria in any trimester of pregnancy should be treated as for any other patient with artesunate preferred over quinine (Grade 1C). 18. Children with uncomplicated malaria should be treated with an ACT (artemether-lumefantrine or dihydroartemisinin-piperaquine) as first line treatment (Grade 1A). Quinine with doxycycline or clindamycin, or atovaquone-proguanil at appropriate doses for weight can also be used. Doxycycline should not be given to children under 12 years. 19. Either an oral ACT or chloroquine can be used for the treatment of non-falciparum malaria. An oral ACT is preferred for a mixed infection, if there is uncertainty about the infecting species, or for P. vivax infection from areas where chloroquine resistance is common (Grade 1B). 20. Dormant parasites (hypnozoites) persist in the liver after treatment of P. vivax or P. ovale infection: the only currently effective drug for eradication of hypnozoites is primaquine (1A). Primaquine is more effective at preventing relapse if taken at the same time as chloroquine (Grade 1C). 21. Primaquine should be avoided or given with caution under expert supervision in patients with Glucose-6-phosphate dehydrogenase deficiency (G6PD), in whom it may cause severe haemolysis. 22. Primaquine (for eradication of P. vivax or P. ovale hypnozoites) is contraindicated in pregnancy and when breastfeeding (until the G6PD status of child is known); after initial treatment for these infections a pregnant woman should take weekly chloroquine prophylaxis until after delivery or cessation of breastfeeding when hypnozoite eradication can be considered. 23. An acute attack of malaria does not confer protection from future attacks: individuals who have had malaria should take effective anti-mosquito precautions and chemoprophylaxis during future visits to endemic areas.

The selective outpatient treatment of adults with imported falciparum malaria: a prospective cohort study

BACKGROUND

Current UK malaria treatment guidelines recommend admission for all patients diagnosed with falciparum malaria. However, evidence suggests that certain patients are at lower risk of severe malaria and death and may be managed as outpatients.

AIM

To prospectively assess the risk of post-treatment severe falciparum malaria in selected cases managed as outpatients. The readmission rate and treatment tolerability were assessed as secondary outcomes.

DESIGN

Prospective cohort study.

METHODS

Adults (>15 years old) diagnosed with falciparum malaria between May 2008 and July 2012 were selected for outpatient treatment using locally defined clinical and laboratory indicators based on known risk factors for severity and death. Treatment outcomes were assessed in clinic or by telephone 4-6 weeks after treatment.

RESULTS

269 adults were diagnosed with falciparum malaria on blood film between May 2008 and July 2012. Of 255 eligible participants, 106 patients were offered ambulatory treatment, of which 95 completed the study. The severe malaria rate was 0% (95% confidence interval (CI) 0-3.8%) and the readmission rate was 5.3% (95% CI 1.7-11.9) in the outpatient group. In addition, 10.6% (95% CI 5.2-18.7%) of outpatients reported drug-related side effects.

CONCLUSIONS

The outpatient treatment of selected cases of falciparum malaria is effective in our high volume UK setting. We recommend adopting a similar approach to managing this infection in other non-endemic settings where immediate access to specialist advice is available.

Transcription Profiling of Malaria-Naïve and Semi-immune Colombian Volunteers in a Plasmodium vivax Sporozoite Challenge

Background

Continued exposure to malaria-causing parasites in endemic regions of malaria induces significant levels of acquired immunity in adult individuals. A better understanding of the transcriptional basis for this acquired immunological response may provide insight into how the immune system can be boosted during vaccination, and into why infected individuals differ in symptomology.

Methodology/Principal Findings

Peripheral blood gene expression profiles of 9 semi-immune volunteers from a Plasmodium vivax malaria prevalent region (Buenaventura, Colombia) were compared to those of 7 naïve individuals from a region with no reported transmission of malaria (Cali, Colombia) after a controlled infection mosquito bite challenge with P. vivax. A Fluidigm nanoscale quantitative RT-PCR array was used to survey altered expression of 96 blood informative transcripts at 7 timepoints after controlled infection, and RNASeq was used to contrast pre-infection and early parasitemia timepoints. There was no evidence for transcriptional changes prior to the appearance of blood stage parasites at day 12 or 13, at which time there was a strong interferon response and, unexpectedly, down-regulation of transcripts related to inflammation and innate immunity. This differential expression was confirmed with RNASeq, which also suggested perturbations of aspects of T cell function and erythropoiesis. Despite differences in clinical symptoms between the semi-immune and malaria naïve individuals, only subtle differences in their transcriptomes were observed, although 175 genes showed significantly greater induction or repression in the naïve volunteers from Cali.

Conclusion/Significance

Gene expression profiling of whole blood reveals the type and duration of the immune response to P. vivax infection, and highlights a subset of genes that may mediate adaptive immunity.

Plasmodium vivax malaria is a debilitating, occasionally life-threatening, and economically burdensome disease in Central Latin America, where 70%- 80% of the population lives with the risk of infection. We performed a gene expression profiling experiment taking advantage of a previously described sporozoite challenge experiment in Cali, Colombia that reported more severe malaria symptoms in subjects who have never experienced malaria. We show that no major differences are seen in the transcriptomes of uninfected naïve and semi-immune volunteers prior to infection, but differential expression of both neutrophil and interferon-related genes was evident at onset of malaria. Several hundred genes showed a stronger response in the naïve individuals just as parasites appear in the peripheral blood, and these fall into several pathways of interest. These findings show how information from gene expression profiling of whole blood can reveal the type and duration of the immune response to P. vivax infection, and highlights a subset of genes that may mediate adaptive immunity in chronically exposed individuals.

Malaria-like symptoms associated with a natural Plasmodium reichenowi infection in a chimpanzee

Although Plasmodium infections have never been clearly associated with symptoms in non-human primates, the question of the pathogenicity of Plasmodium parasites in non-human primates still remains unanswered. A young chimpanzee, followed before and after release to a sanctuary, in a semi-free ranging enclosure located in an equatorial forest, showed fever and strong anaemia associated with a high Plasmodium reichenowi infection, shortly after release. The animal recovered from anaemia after several months despite recurrent infection with other Plasmodium species. This may be the first description of malaria-like symptoms in a chimpanzee infected with Plasmodium.

Epidemiology of imported malaria give support to the hypothesis of 'long-term' semi-immunity to malaria in sub-Saharan African migrants living in France

BACKGROUND

Short-term semi-immunity to malaria in sub-Saharan African migrants who have recently arrived in non-endemic countries results in less severe imported malaria. Our aim was to investigate the factors associated with imported malaria that would favour the hypothesis of a 'long-term' semi-immunity to malaria in adult travellers of sub-Saharan origin living in France and visiting family or relatives in their country of origin (VFR group).

METHOD

The epidemiological, clinical and biological characteristics of imported Plasmodium falciparum malaria in VFR were compared with those of travellers of European origin (TEO). Newly arrived African migrants and European expatriates were excluded.

RESULTS

This retrospective study included 106 adult VFR (30%) and 240 adult TEO (70%) with imported P. falciparum malaria treated at the University Hospital Center of Bordeaux between 2000 and 2007. The main regions visited were West Africa (58%) and Central Africa (34%). P. falciparum was associated with severe malaria in 8% of patients (VFR 3% vs. TEO 11%), of which two TEO died. In univariate analysis, the factors associated with P. falciparum malaria in VFR vs. TEO were: female sex, younger age, less frequent use of mosquito nets, poor compliance with chemoprophylaxis, less severe malaria without death, less severe thrombocytopenia and a tendency towards a lower level of parasitaemia and higher haemoglobinaemia. In multivariate analysis, the only factor to be independently associated with P. falciparum malaria in VFR compared to TEO was less frequent severe malaria.

CONCLUSIONS

Our results give support to the hypothesis of 'long-term' semi-immunity to malaria in VFR living in France.

Risk factors for mortality from imported falciparum malaria in the United Kingdom over 20 years: an observational study

OBJECTIVES

To determine which travellers with malaria are at greatest risk of dying, highlighting factors which can be used to target health messages to travellers.

DESIGN

Observational study based on 20 years of UK national data.

SETTING

National register of malaria cases.

PARTICIPANTS

25,054 patients notified with Plasmodium falciparum malaria, of whom 184 died, between 1987 and 2006.

MAIN OUTCOME MEASURES

Comparison between those with falciparum malaria who died and non-fatal cases, including age, reason for travel, country of birth, time of year diagnosed, malaria prophylaxis used.

RESULTS

Mortality increased steadily with age, with a case fatality of 25/548 (4.6%) in people aged >65 years, adjusted odds ratio 10.68 (95% confidence interval 6.4 to 17.8), P<0.001 compared with 18-35 year olds. There were no deaths in the ≤ 5 year age group. Case fatality was 3.0% (81/2740 cases) in tourists compared with 0.32% (26/8077) in travellers visiting friends and relatives (adjusted odds ratio 8.2 (5.1 to 13.3), P<0.001). Those born in African countries with endemic malaria had a case fatality of 0.4% (36/8937) compared with 2.4% (142/5849) in others (adjusted odds ratio 4.6 (3.1 to 9.9), P<0.001). Case fatality was particularly high from the Gambia. There was an inverse correlation in mortality between region of presentation and number of cases seen in the region (R(2) = 0.72, P<0.001). Most delay in fatal cases was in seeking care.

CONCLUSIONS

Most travellers acquiring malaria are of African heritage visiting friends and relatives. In contrast the risks of dying from malaria once acquired are highest in the elderly, tourists, and those presenting in areas in which malaria is seldom seen. Doctors often do not think of these as high risk groups for malaria; for this reason they are important groups to target in pre-travel advice.

Acquired immunity to malaria

Naturally acquired immunity to falciparum malaria protects millions of people routinely exposed to Plasmodium falciparum infection from severe disease and death. There is no clear concept about how this protection works. There is no general agreement about the rate of onset of acquired immunity or what constitutes the key determinants of protection; much less is there a consensus regarding the mechanism(s) of protection. This review summarizes what is understood about naturally acquired and experimentally induced immunity against malaria with the help of evolving insights provided by biotechnology and places these insights in the context of historical, clinical, and epidemiological observations. We advocate that naturally acquired immunity should be appreciated as being virtually 100% effective against severe disease and death among heavily exposed adults. Even the immunity that occurs in exposed infants may exceed 90% effectiveness. The induction of an adult-like immune status among high-risk infants in sub-Saharan Africa would greatly diminish disease and death caused by P. falciparum. The mechanism of naturally acquired immunity that occurs among adults living in areas of hyper- to holoendemicity should be understood with a view toward duplicating such protection in infants and young children in areas of endemicity.

Falciparum malaria as a cause of fever in adult travellers returning to the United Kingdom: observational study of risk by geographical area

BACKGROUND

The probability that a returned traveller with a history of fever has malaria is likely to vary by geographical area, but this has not been quantified in travellers.

AIM

To collect data on prevalence of malaria in outpatients returning with a fever or history of fever from malaria-endemic countries, at the point of presentation for a malaria test.

DESIGN

Observational retrospective study. Consecutive patients presenting to an unselected 'walk-in' clinic for returned travellers.

RESULTS

Of 2867 patients meeting inclusion criteria, 337 (11.8%) had malaria, 89.5% originating in sub-Saharan Africa. Of travellers returning from sub-Saharan Africa excluding South Africa with fever/history of fever, 291/1497 had malaria (19.4%, 95% CI 17-21%). A high proportion was visiting friends and relatives. In those from other areas the proportions were: 16/707 (2.3%, 95% CI 1.5-3.8) from Indian subcontinent/Southeast Asia; 2/143 (1.4%) from Southern America; 4/129 (3.1%) from South Africa; 1/44 (2.3%) from North Africa; and 8/41 (19.5%) from Oceania. Compared to other malaria-endemic regions, African travel gave an adjusted odds ratio of 7.8 (95% CI 5.4-11.2, P < 0.0001). Only 45.1% of malaria cases had a fever (> or =37.5 degrees C) at the time of presentation. Only 3% of all diagnoses of malaria had no history of fever. In 28% of cases parasite count increased in the initial 24 h of antimalarial treatment.

CONCLUSION

The likelihood that a patient with fever returning from Africa has malaria is high (around 1 in 5), and is significantly lower from other areas. Absence of fever at presentation does not exclude malaria.

Imported malaria and high risk groups: observational study using UK surveillance data 1987-2006

OBJECTIVE

To examine temporal, geographic, and sociodemographic trends in case reporting and case fatality of malaria in the United Kingdom.

SETTING

National malaria reference laboratory surveillance data in the UK.

DESIGN

Observational study using prospectively gathered surveillance data and data on destinations from the international passenger survey.

PARTICIPANTS

39,300 cases of proved malaria in the UK between 1987 and 2006.

MAIN OUTCOME MEASURES

Plasmodium species; sociodemographic details (including age, sex, and country of birth and residence); mortality; destination, duration, and purpose of international travel; and use of chemoprophylaxis.

RESULTS

Reported cases of imported malaria increased significantly over the 20 years of the study; an increasing proportion was attributable to Plasmodium falciparum (P falciparum/P vivax reporting ratio 1.3:1 in 1987-91 and 5.4:1 in 2002-6). P vivax reports declined from 3954 in 1987-91 to 1244 in 2002-6. Case fatality of reported P falciparum malaria did not change over this period (7.4 deaths per 1000 reported cases). Travellers visiting friends and relatives, usually in a country in Africa or Asia from which members of their family migrated, accounted for 13 215/20 488 (64.5%) of all malaria reported, and reports were geographically concentrated in areas where migrants from Africa and South Asia to the UK have settled. People travelling for this purpose were at significantly higher risk of malaria than other travellers and were less likely to report the use of any chemoprophylaxis (odds ratio of reported chemoprophylaxis use 0.23, 95% confidence interval 0.21 to 0.25).

CONCLUSIONS

Despite the availability of highly effective preventive measures, the preventable burden from falciparum malaria has steadily increased in the UK while vivax malaria has decreased. Provision of targeted and appropriately delivered preventive messages and services for travellers from migrant families visiting friends and relatives should be a priority.

Laboratory indicators of the diagnosis and course of imported malaria

When travellers return from malaria-endemic areas and present to hospital with fever, microscopy of blood smears remains the leading method to verify a suspected diagnosis of malaria. Additional laboratory abnormalities may, however, also be indicative of acute malaria infection. We monitored prospectively a group of patients with imported Plasmodium falciparum (n=28) or P. vivax/P. ovale (n=12) infection, respectively, and assessed haemoglobin, leucocytes, thrombocytes, C-reactive protein, coagulation factor II-VII-X, lactate dehydrogenase and bilirubin during 7 d of admission and weekly until d 28. For comparison, admission values of a group of febrile patients with suspected malaria, but with negative blood slides, were also assessed (n=66). The thrombocyte, leucocyte counts and coagulation factor II-VII-X were significantly lower in the malaria group compared to the non-malaria group, whereas the C-reactive protein, lactate dehydrogenase and bilirubin were significantly higher in the malaria group. The differences were particularly strong with falciparum malaria. By contrast, haemoglobin levels were not affected. In conclusion, our study emphasizes the role of a few commonly analysed laboratory parameters, in particular thrombocyte counts, in guiding the clinician managing a returning traveller with fever.

Hospitalization criteria in imported falciparum malaria

BACKGROUND

Controversy exists about the management of patients with imported Plasmodium falciparum malaria. We postulated that rapid parasite clearance supports ambulatory care, or, conversely, that factors associated with longer parasite clearance time (PCT) could be used as hospitalization criteria.

METHODS

Hospitalized patients with imported falciparum malaria recruited through one single travel clinic between 1993 and 2000. We used a linear regression to identify factors independently associated with PCT defined as the time in hours from antimalarial drug administration until the first negative malaria smear.

RESULTS

Among 400 patients hospitalized with falciparum malaria, mean (range) PCT was 58 (1-189) hours. In multivariate analysis, severe malaria, gastrointestinal signs, initial temperature greater than or equal to 40 degrees C, parasitemia greater than or equal to 1%, and platelet counts less than 50,000/microL were associated with longer PCT. Offering ambulatory care to patients aged 15 to 64 years with none of the factors associated with longer PCT in the study would have resulted in 147 (37%) patients receiving outpatient care.

CONCLUSION

Factors identified in this model may help physicians determine which P falciparum malaria patients can be treated on an ambulatory basis, and contribute to revisions of national guidelines for imported malaria management.

UK malaria treatment guidelines

Malaria is the tropical disease most commonly imported into the UK, with 1500-2000 cases reported each year, and 10-20 deaths. Approximately three-quarters of reported malaria cases in the UK are caused by Plasmodium falciparum, which is capable of invading a high proportion of red blood cells and rapidly leading to severe or life-threatening multi-organ disease. Most non-falciparum malaria cases are caused by Plasmodium vivax; a few cases are caused by the other two species of Plasmodium: Plasmodium ovale or Plasmodium malariae. Mixed infections with more than 1 species of parasite can occur; they commonly involve P. falciparum with the attendant risks of severe malaria. Management of malaria depends on awareness of the diagnosis and on performing the correct diagnostic tests: the diagnosis cannot be excluded until 3 blood specimens have been examined by an experienced microscopist. There are no typical clinical features of malaria, even fever is not invariably present. The optimum diagnostic procedure is examination of thick and thin blood films by an expert to detect and speciate the malarial parasites; P. falciparum malaria can be diagnosed almost as accurately using rapid diagnostic tests (RDTs) which detect plasmodial antigens or enzymes, although RDTs for other Plasmodium species are not as reliable. The treatment of choice for non-falciparum malaria is a 3-day course of oral chloroquine, to which only a limited proportion of P. vivax strains have gained resistance. Dormant parasites (hypnozoites) persist in the liver after treatment of P. vivax or P. ovale infection: the only currently effective drug for eradication of hypnozoites is primaquine. This must be avoided or given with caution under expert supervision in patients with glucose-6-phosphate dehydrogenase deficiency (G6PD), in whom it may cause severe haemolysis. Uncomplicated P. falciparum malaria can be treated orally with quinine, atovaquone plus proguanil (Malarone) or co-artemether (Riamet); quinine is highly effective but poorly tolerated in prolonged dosage and is always supplemented by additional treatment, usually with oral doxycycline. ALL patients treated for P. falciparum malaria should be admitted to hospital for at least 24 h, since patients can deteriorate suddenly, especially early in the course of treatment. Severe falciparum malaria, or infections complicated by a relatively high parasite count (more than 2% of red blood cells parasitized), should be treated with intravenous therapy until the patient is well enough to continue with oral treatment. In the UK, the treatment of choice for severe or complicated malaria is currently an infusion of intravenous quinine. This may exacerbate hypoglycaemia that can occur in malaria; patients treated with intravenous quinine therefore require careful monitoring. Intravenous artesunate reduces high parasite loads more rapidly than quinine and is more effective in treating severe malaria in selected situations. It can also be used in patients with contra-indications to quinine. Intravenous artesunate is unlicensed in the EU. Assistance in obtaining artesunate may be sought from specialist tropical medicine centres, on consultation, for named patients. Patients with severe or complicated malaria should be managed in a high dependency or intensive care environment. They may require haemodynamic support and management of acute respiratory distress syndrome, disseminated intravascular coagulation, renal impairment/failure, seizures, and severe intercurrent infections including gram-negative bacteraemia/septicaemia. Falciparum malaria in pregnancy is more likely to be severe and complicated: the placenta contains high levels of parasites. Stillbirth or early delivery may occur and diagnosis can be difficult if parasites are concentrated in the placenta and scanty in the blood. The treatment of choice for falciparum malaria in pregnancy is quinine; doxycycline is contraindicated in pregnancy but clindamycin can be substituted for it, and is equally effective. Primaquine (for eradication of P. vivax or P. ovale hypnozoites) is contraindicated in pregnancy; after treatment for these infections a pregnant woman should take weekly chloroquine prophylaxis until after delivery when hypnozoite eradication can be considered. Children are over-represented in the incidence of malaria in the UK, probably because completely susceptible UK-born children accompany their overseas-born parents on visits to family and friends in endemic areas. Malaria in children (and sometimes in adults) may present with misleading symptoms such as gastrointestinal features, sore throat or lower respiratory complaints; the diagnosis must always be sought in a feverish or very sick child who has visited malaria-endemic areas. Children can be treated with most of the antimalarial regimens which are effective in adults, with appropriate dosage adjustment. Doxycycline plus quinine should not be given to children under 12 years as doxycycline is contraindicated in this age group, but clindamycin can be substituted for doxycycline, and pyrimethamine-sulfadoxine (Fansidar) may also be an effective substitute. An acute attack of malaria does not confer protection from future attacks: individuals who have had malaria should take effective anti-mosquito precautions and chemoprophylaxis during future visits to endemic areas.

Malaria: Diagnosis and treatment of falciparum malaria in travelers during and after travel

Plasmodium falciparum is responsible for most of the mortality in travelers related to imported malaria. Problems that occur during travel include the inaccuracy of a microscopic diagnosis of malaria, both false positives and false negatives, when ill travelers seek care while abroad. A false positive diagnosis can result in unnecessary parenteral injections that carry a risk of transmission of blood-borne pathogens, receipt of potentially dangerous drugs such as halofantrine, or receipt of fake, counterfeit drugs. Increased morbidity and mortality are associated with delays in diagnosis and initiation of prompt treatment for falciparum malaria. Availability of expert microscopy to confirm the diagnosis of malaria is limited. The presence of splenomegaly and thrombocytopenia are strongly associated with malaria and would justify empiric treatment. The availability of atovaquone-proguanil, a safe and well tolerated oral drug, should prompt a reconsideration of current treatment recommendations that discourage empiric treatment on clinical suspicion alone.

Pharmacodynamic analysis of antimalarials used in Plasmodium falciparum imported malaria in northern Italy

BACKGROUND

Conventional treatment of imported malaria in Italy consists of quinine or mefloquine. Since beta-arthemeter is now available, an open-label pharmacodynamic analysis was performed in 73 adults with uncomplicated Plasmodium falciparum malaria. In vitro susceptibility to mefloquine and quinine was evaluated at admission.

METHODS

According to clinical status, baseline parasitemia (P(0)), and premunition, the patients received intravenous quinine, oral mefloquine, or beta-arthemeter. The following parameters were measured: parasitemia at 0, 6, 12, and 24 hours and then every 24 hours until negative; time to 50%, 90%, and 100% reduction in parasite density (PC(50), PC(90), and PCT); parasite reduction ratio at 24 and 48 hours (PRR(24) and PRR(48)); percentage of patients with undetectable parasitemia at 48 hours (PPUP(48)); time required to eradication; in vitro susceptibility to mefloquine and quinine by World Health Organization Microtest Mark III.

RESULTS

Of the study patients, 54.8% were immigrants from malaria-endemic countries. All the infections were acquired in Africa. All the patients were treated successfully. According to the pharmacodynamic parameters measured, no significant differences were recorded among patients with or without prior exposure to malaria. Pharmacodynamic comparison was performed between quinine and beta-arthemeter. Significantly higher clearance times were recorded for beta-arthemeter vs quinine (PC(50), PC(90), and PCT: 16.8, 42.6, and 72 h for quinine vs 7.9, 12.2, and 48 h for beta-arthemeter; p values: .02, < .0001, and .008, respectively). The number of patients who obtained a PPUP(48) with beta-arthemeter was higher than with quinine (66.7 vs 9.1%, p < .003), and PRR(24) was significantly higher in beta-arthemeter-treated patients (617 vs 3.15, p = .0001). PRR(48) and time to eradication were not measurable in the beta-arthemeter group (negative P at 48 h in most cases). Two recrudescences occurred after 5 and 7 days of beta-arthemeter monotherapy. All strains were fully susceptible to quinine and mefloquine.

CONCLUSIONS

Pharmacodynamic properties of mefloquine and quinine are in the range reported in literature. The better PCT and pharmacodynamics of beta-arthemeter suggest that it could be used as a first-line agent, coadministered with mefloquine.