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

Fever in the Returned Traveler

International travel is associated with a risk of infections not typically seen in high-income settings. Malaria is the most important tropical infection in travelers, but epidemics of dengue, chikungunya, and Zika emphasize that clinicians need to be aware of the rapidly changing distribution of many arboviruses. A detailed travel history and a syndromic approach to the investigation and management of patients is key. Consultation with a specialist is often recommended to ensure that appropriate management and investigations are undertaken in febrile returned travelers.

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Travel, especially to low-income regions, is associated with an increased risk of infections not typically seen in high-income countries (e.g., malaria, enteric fever, dengue, chikungunya, Zika, and schistosomiasis).

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Although gastroenteritis, respiratory tract infections, and self-limiting viral infections are common, a minority of patients will have a potentially life-threatening tropical infection.

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The evaluation of an ill returned traveler requires a detailed travel history with an understanding of the geographic distribution of infections, risk factors for acquisition, incubation periods, clinical presentations, and appropriate laboratory investigations.

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A syndromic approach to specific investigations, and to presumptive therapy pending laboratory confirmation of the diagnosis, is appropriate.

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Travel is also a risk factor for acquisition of antimicrobial-resistant bacteria, such as those containing extended spectrum β-lactamases, that become part of the traveler's colonizing flora.

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As a rule, malaria should be excluded in all travelers presenting with a fever who have visited the tropics.

Assessment of returning travellers with fever

Millions of people travel to the tropics each year and a significant minority of them become ill, either during their stay or shortly after their return. Most have mild, self-limiting illnesses, but a few have a life-threatening condition. This article outlines how to evaluate fever in the returning traveller and discusses important infection control and public health measures. A detailed travel history, which takes into account travel destinations, specific activities and risk factors in relation to the onset of symptoms, is essential for constructing a comprehensive list of differential diagnoses and guiding appropriate investigations. Importantly, all travellers returning from the tropics with a fever should be investigated for malaria.

Assessment of returning travellers with fever

Millions of people travel to the tropics each year and a significant minority of them become ill, either during their stay, or shortly after their return. Most have mild, self-limiting illnesses, but a few will have a life-threatening condition. This article outlines how to evaluate fever in the returning traveller and discusses important infection control and public health measures. A detailed travel history, which takes into account travel destinations, specific activities and risk factors in relation to the onset of symptoms, is essential for constructing a comprehensive list of differential diagnoses and guiding appropriate investigations. Importantly, all travellers returning from the tropics with a fever should be investigated for malaria, even if their return was 3 months ago or longer.

Infectious disease emergencies in returning travelers: special reference to malaria, dengue fever, and chikungunya

This review article discusses important infectious illnesses, namely malaria, dengue, and chikungunya, in travelers returning from endemic areas. Malaria and dengue are two of the most common systemic illnesses reported in returning travelers. Because chikungunya is gaining importance, it is also briefly discussed. The clinical significance of these diseases is mainly due to the possibility of sudden deterioration with high mortality in clinically healthy looking patients. The key clinical features, their diagnosis, and treatment algorithms are discussed in detail to help in early diagnosis and appropriate clinical management of such travelers presenting in emergency departments.

Fever in returned travellers presenting in the United Kingdom: recommendations for investigation and initial management

International travel is increasing. Most physicians and general practitioners will encounter returned travellers with fever and the majority of travel-related infection is associated with travel to the tropics. In those returning from the tropics malaria must always be excluded, and HIV considered, from all settings. Common causes of non-malarial fever include from Africa rickettsial diseases, amoebic liver abscess and Katayama syndrome; from South and South East Asia, enteric fever and arboviral infection; from the Middle East, brucellosis and from the Horn of Africa visceral leishmaniasis. Other rare but important diseases from particular geographical areas include leptospirosis, trypanosomiasis and viral haemorrhagic fever. North and South America, Europe and Australia also have infections which are geographically concentrated. Empirical treatment may have to be started based on epidemiological probability of infection whilst waiting for results to return. The evidence base for much of the management of tropical infections is limited. These recommendations provide a pragmatic approach to the initial diagnosis and management of fever in returned travellers, based on evidence where it is available and on consensus of expert opinion where it is not. With early diagnosis and treatment the majority of patients with a potentially fatal infection related to travel will make a rapid and full recovery.

Fever in returned travelers: results from the GeoSentinel Surveillance Network

BACKGROUND

Fever is a marker of potentially serious illness in returned travelers. Information about causes of fever, organized by geographic area and traveler characteristics, can facilitate timely, appropriate treatment and preventive measures.

METHODS

Using a large, multicenter database, we assessed how frequently fever is cited as a chief reason for seeking medical care among ill returned travelers. We defined the causes of fever by place of exposure and traveler characteristics.

RESULTS

Of 24,920 returned travelers seen at a GeoSentinel clinic from March 1997 through March 2006, 6957 (28%) cited fever as a chief reason for seeking care. Of patients with fever, 26% were hospitalized (compared with 3% who did not have fever); 35% had a febrile systemic illness, 15% had a febrile diarrheal disease, and 14% had fever and a respiratory illness. Malaria was the most common specific etiologic diagnosis, found in 21% of ill returned travelers with fever. Causes of fever varied by region visited and by time of presentation after travel. Ill travelers who returned from sub-Saharan Africa, south-central Asia, and Latin America whose reason for travel was visiting friends and relatives were more likely to experience fever than any other group. More than 17% of travelers with fever had a vaccine-preventable infection or falciparum malaria, which is preventable with chemoprophylaxis. Malaria accounted for 33% of the 12 deaths among febrile travelers.

CONCLUSIONS

Fever is common in ill returned travelers and often results in hospitalization. The time of presentation after travel provides important clues toward establishing a diagnosis. Preventing and promptly treating malaria, providing appropriate vaccines, and identifying ways to reach travelers whose purpose for travel is visiting friends and relatives in advance of travel can reduce the burden of travel-related illness.

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.

Management of severe malaria: interventions and controversies

This article emphasizes that for many controversial reasons, severe malaria in travelers differs from that seen in endemic areas. There is no controversy, however, that malaria in individuals living in endemic areas should retain research priority. Some of the questions raised might never be amenable to randomized controlled trials, either because of ethical or logistical restraints. A possibly indulgent wish list of outcome (mortality) studies using currently known treatment modalities, however, includes the loading dose of quinine, vigorous fluid replacement, ET, the artemisinins, mannitol, and N-acetylcysteine in the treatment of severe malaria. There may clearly be many more. The treatment of severe malaria remains a challenge to those with an interest in managing life-threatening disease with complex and fascinating pathophysiology. As challenging as the studies listed previously may seem, however, priority must inevitably be given to research on how one can prevent and treat mild disease in the first place.

Factors influencing the pattern of imported malaria

BACKGROUND

Data on imported malaria in industrialized areas are known to be incomplete because of underreporting and lack of homogeneity. These facts and the complexity of factors influencing the transmission of malaria render their interpretation difficult. The relevance of various factors is usually not fully considered, although their impact on recommendations for chemoprophylaxis may be important.

METHODS

All malaria cases imported from Kenya from 1988 to 1996 that were reported to the Federal Office of Public Health of Switzerland were analyzed. The reciprocal impact on data interpretation with regard to Plasmodium species, chemoprophylaxis, onset of first symptoms after return, male or female sex, seasonal fluctuation, duration of stay, nationality groups, and fatal outcome was analyzed.

RESULTS

Multivariate analysis showed a significant impact of Plasmodium species, regular chemoprophylaxis, and long duration of stay on the latency of malaria attacks. African origin and repeated stays were confounders with regard to adherence to chemoprophylaxis. The local situation of malaria transmission and the development of tourist figures were found to influence the evolution of malaria rates. These factors must be analyzed simultaneously to prevent errors in data interpretation. A higher proportion of tertian malaria cases (caused by Plasmodium vivax or Plasmodium ovale) than in previous reports was recorded owing to the impact of chemoprophylaxis and longer outbreak latencies. Seventy-five percent of tertian malaria cases were diagnosed within 6 months after return.

CONCLUSIONS

Factors influencing the pattern of imported malaria must be assessed in relation to each other, especially if data from different countries and various chemoprophylaxis regimens are compared. Furthermore, regular malaria chemoprophylaxis with mefloquine given until 4 weeks after return from an endemic area is not adequate to prevent tertian malaria. Regular chemoprophylaxis was found to cause longer latencies for all malaria species.

Assessment of travellers who return home ill

Every year, millions of people travel abroad, exposing themselves to various diseases. Advice on risk avoidance and on self-medication is not always successful; sometimes travellers return home ill or become unwell soon afterwards. There are many possible causes for such illnesses, and physicians should try to establish whether the disease is specifically associated with the recent journey. The approach to assessment of the ill traveller should make use not only of signs and symptoms, but also of geography and epidemiology. Travellers with fever need immediate attention to rule out serious and potentially life-threatening conditions. Faced with a difficult diagnosis, physicians should consult with experts in tropical and travel medicine.

Prophylaxis failure due to probable mefloquine resistant P falciparum from Tanzania

Failures of mefloquine prophylaxis in travellers returning from Africa have been reported repeatedly. Non-compliance to chemoprophylaxis is considered to be a major factor for failure. Only few reports on mefloquine prophylaxis failure in sub-Saharan Africa were able to report blood levels of the drug that were sufficient for prophylactic effectiveness. We report the case of a 44-year-old German female who travelled to Tanzania for 3 weeks. The patient reported that she never missed a dose of mefloquine during her weekly prophylaxis schedule. Four weeks after returning from Tanzania, the patient presented with fever, headache and myalgia. Only a few trophozoites of Plasmodium falciparum were found in a thick film. Blood levels of mefloquine at that stage were at 1400 ng/ml, thus largely excluding non-compliance and malabsorption. To our knowledge, this is the first case of confirmed prophylaxis failure due to mefloquine resistance in East Africa.

The prevention of malaria

Long before the advent of modern chemoprophylaxis drugs, many practitioners successfully prevented the debilitating and fatal outcomes associated with infection by the Plasmodium parasites that cause malaria. Today, with effective insect repellents and several excellent medications available for chemoprophylaxis, there has never been a better array of quality products to prevent mosquito bites and infection and to suppress parasites once in the blood stream; however, there are thousands of imported cases into nonendemic countries and scores of deaths and near-fatal outcomes every year in returning travelers, soldiers, immigrants, and refugees. In this article, the author focuses on practical uses of currently available prevention tools.

9: Infections in the returned traveller

The usual presentation of a returned traveller is with a particular syndrome - fever, respiratory infection, diarrhoea, eosinophilia, or skin or soft tissue infection - or for screening for asymptomatic infection. Fever in a returned traveller requires prompt investigation to prevent deaths from malaria; diagnosis of malaria may require up to three blood films over 36-48 hours. Diarrhoea is the most common health problem in travellers and is caused predominantly by bacteria; persistent diarrhoea is less likely to have an infectious cause, but its prognosis is usually good. While most travel-related infections present within six months of return, some important chronic infections may present months or years later (eg, strongyloidiasis, schistosomiasis). Travellers who have been bitten by an animal require evaluation for rabies prophylaxis.

Mefloquine chemoprophylaxis in Chinese railway workers on contract in Nigeria

BACKGROUND

Nonimmune Chinese nationals on a 2-year railway contract job were commenced on mefloquine (MQ) chemoprophylaxis 20 weeks after arrival in Nigeria. The objective of the study was to determine the usefulness of mefloquine (MQ) (despite the delay in starting) and its tolerability in this group.

METHODS

Ninety-one workers (89 males, 2 females) were commenced on weekly MQ 250 mg doses for 17 weeks. Most of the subjects were followed up to 16 weeks after cessation of chemoprophylaxis. The morbidity pattern before, during, and after cessation of chemoprophylaxis was compared.

RESULTS

Of the 91 workers included in the study, 89 were evaluable. Three (3.37%) of these developed clinical illness during the 17-week period of chemoprophylaxis. This protection was highly significant when compared to 23 of 91 people (25.27%) who developed clinical illness before chemoprophylaxis was commenced (RR 0.13, 95% CI 0.04-0.43, p <.001). The risk of developing acute malaria increased more than three times, among 84 members of the group who were followed up to 16 weeks after MQ was discontinued (RR 3.18, 95% CI 0.89-11.34). Two subjects withdrew after the second dose due to adverse reactions, however the remaining 89 subjects tolerated the drug for the 16-week period.

CONCLUSIONS

Mefloquine significantly reduced malaria morbidity in the study group. Pretravel counseling and advice is important in preventing unnecessary deaths and morbidity in nonimmune travelers to malarious areas.