Travellers' malaria

Factors affecting the use of anti-malaria preventive measures among Taiwan immigrants returning to malaria-endemic regions

The aim of this study was to investigate the predictors of anti-malaria preventive measures (AMPMs) among Taiwan immigrants returning to their country of origin using the Health Belief Model (HBM). Between March and May 2011, all permanent immigrants originating from malaria-endemic countries, attended by either the Taipei or Tainan Immigrant Service Center, Taiwan, and who reported a history of returning to their country of origin within the preceding year during the malarious season in their country of origin were enrolled in the study. Complete information was collected from 316 immigrants, with a response rate of 87% (316/364). The mean age of the subjects was 38.1 years (SD = 9.9). The majority (70%) of participants did not receive travel information through a pre-travel consultation; more than 40% reported that they did not use measures to prevent insect bites. Multiple regression analyses revealed that Chinese proficiency, travel consultation before travel, lower perceived susceptibility to malaria, higher perceived severity of malaria infection, higher perceived benefit for taking measures, and higher self-efficacy for taking measures significantly predicted the use of AMPMs during the return to their country of origin (R(2) = 0.20; F = 50.42; P < 0.001). A high proportion of immigrants were not using appropriate AMPMs when they returned to their country. Educational approaches should be targeted toward immigrants who return to visit their country of origin.

Risk of malaria among French adult travellers

BACKGROUND

Imported malaria remains an important, but often unrecognised, health problem in Europe. Little information exists on the incidence of imported malaria with respect to exposure. This study aimed to estimate the incidence of malaria in a cohort of travellers with respect to protection measures.

METHOD

In all 13,017 participants enrolled in a French general population cohort (SU.VI.MAX cohort) and followed-up over 8 years were investigated. All participants received a retrospective questionnaire about travel to malaria-endemic countries relating to countries visited, duration of stay, use of protection measures and chemoprophylaxis. Malaria cases was confirmed from medical records.

RESULTS

Data were obtained for 752 individuals who made 1,393 trips to malaria-endemic areas. This sample was predominantly middle-class and high-risk groups such as migrants were not represented. Mechanical protection was used in 589 trips (42.3%) and chemoprophylaxis in 1,017 trips (73.0%). This was appropriate for the zone in 615 trips (44.0%) and adequate compliance was reported in the case of 497 trips (35.6%). Appropriate chemoprophylaxis and physical protection measures were used in 21.7% of the trips. Six laboratory-confirmed cases of imported malaria yielded an estimated incidence density of 148 cases/month of exposure/10,000 travellers. In five cases, appropriate protection measures had not been taken.

CONCLUSION

Appropriate chemoprophylaxis and physical protection measures against malaria infection are used by less than one-quarter of a sample of predominantly middle-class travellers from France to endemic areas. More intense education measures need to be implemented to reduce the risk of imported malaria.

Changing epidemiological and clinical aspects of imported malaria in Belgium

BACKGROUND

In the early nineties the increase of imported malaria in some European countries was temporarily halted, but it resumed in 1994. More Africans, more European travelers, and fewer long-term residents were counted amongst patients. A shift towards more subacute disease has been noted. This study intends to assess whether the same trends were observed in Belgium.

METHODS

Clinical and epidemiological data of 128 patients treated for malaria in 1997 at the Institute of Tropical Medicine and the University Hospital of Antwerp were compared with 209 malaria patients treated in 1988/1989. Risk factors for clinical presentation and parasitemia were analysed.

RESULTS

In Belgium the number of reported imported malaria cases remained almost stable between 1988 and 1997. In 1997, there were more African patients, less infections from Central Africa, and 50% less residents. Less patients reported prophylaxis use. The causative agent shifted from Plasmodium falciparum to other species. Subacute and atypical malaria became less frequent. In both years, there were no deaths, and severe malaria did not increase significantly. Mefloquine disappeared almost as a curative treatment, and was replaced by quinine, with or without a long acting agent, or by halofantrine. The ethnic origin, nor the use of chemoprophylaxis, influenced disease characteristics. In 1988, malaria attacks in the previous months predisposed to subacute disease; longer residence, and attacks in the previous months, protected against high parasitemia; longer symptom duration correlated with absence of fever, and with splenomegaly. None of these risk factors was correlated with severe malaria.

CONCLUSION

The incidence of subacute malaria dropped significantly in the last decade. Although this presentation is almost limited to residents, the decline in malaria can not be explained by an overall shorter duration of stay, since the decline in this particular clinical presentation of malaria was also spectacular in residents. Apparently, insufficient treatment of malaria attacks in the previous months is the only independent risk factor.

Knowledge of travel medicine providers: analysis from a continuing education course

BACKGROUND

With millions of international travelers, there has been an increase in the scope and variability of travel medicine providers. A study was conducted to measure the baseline knowledge of providers, determine factors affecting this knowledge, and assess acquisition of knowledge after a continuing education course.

METHODS

A one-day continuing medical education course was held for health care professionals interested in travel medicine. Prior to the course, attendees completed a test determining knowledge in malaria chemoprophylaxis, traveler's diarrhea management, vaccines, jet lag, the returned traveler, and other areas. An identical test was given after completion of the course. Performance on the test was analyzed by profession, area of specialty training, and experience in travel medicine.

RESULTS

Seventy-seven attendees completed the precourse test. Forty-eight percent were physicians and 47% were nurses; 29% specialized in infectious diseases, 22% in occupational medicine and student health, and 18% in family or internal medicine; 60% had >/= 1 year of travel medicine experience while 20% had no experience. The precourse test score for all participants was 62.7% 6 6.5 (sd). Analysis by profession found that physicians scored the highest (71%). Providers with >/= 1 year of travel medicine experience scored higher than those with no experience (67% vs 53%, p <.01). Statistically significant correlations were found between precourse exam results and profession (+.432, p <.001) and travel medicine experience (+.365, p =.002). No significant correlation was found between precourse exam and area of specialty training. Combined mean score on the postcourse exam improved to 81.8% 6 4.5, an increase of 17.2% over the precourse score for those who took both tests (p <.001).

CONCLUSIONS

The profession of the provider and the duration of experience in travel medicine were the most important correlations of baseline knowledge in travel medicine. All groups improved their knowledge following the course.

Mefloquine for malaria chemoprophylaxis 1992-1998: a review

Mefloquine is an orally administered blood schizontocide for the chemoprophylaxis of malaria in nonimmune travelers. New pharmacokinetic data has shown that food increases the bioavailability of mefloquine. Steady-state pharmacokinetics of weekly prophylaxis in long term travelers have shown that toxic accumulation does not occur and that weekly dosing is associated with protective levels of the drug. The pharmacokinetics of mefloquine are highly stereospecific and all pharmacokinetic parameters, except tmax are significantly different for the (+) and (-) enantiomers. Mefloquine and its metabolite are not appreciably removed by hemodialysis. Steady-state levels of mefloquine can be attained in a reduced time frame of 4 days compared to 7-9 weeks using a loading dose strategy of 250 mg mefloquine daily for 3 days followed thereafter by weekly mefloquine dosage. This strategy, is however, associated with a higher incidence of an adverse event (AE). Cumulative evidence suggests a high protective efficacy of mefloquine (>91%) in nonimmune travelers to areas of chloroquine resistant Plasmodium falciparum (CRPF) except for clearly defined regions of multi-drug resistance. Reports from sub-Saharan Africa indicate a low but increasing level of resistance to this drug. Mefloquine resistance is associated with halofantrine and quinine resistance but not with chloroquine resistance. Penfluridol has been shown to reverse P. falciparum mefloquine resistance in vitro. There is some controversy regarding the tolerabilty of mefloquine for malaria chemoprophylaxis. A review of the studies conducted during 1992-1998 shows that in the reporting of any AE the incidence lies in the range (12-90%) and where there is a comparator, is equivalent to the incidence reported for almost all alternative regimens. When some measure of subjective severity is applied to the rating of AE, it appears that 11-17% of travelers are, to some extent, incapacitated by AE. Major studies and worldwide monitoring have shown that serious events are rare. A recent meta-analysis showed that rates of withdrawal and overall incidence of AE with mefloquine were not significantly higher than those observed with comparator regimens except that mefloquine was more likely to cause insomnia and fatigue. Withdrawals in mefloquine arms were higher than in placebo arms. No performance deficit or functional impairment was observed in five clinical toxicity studies of mefloquine prophylaxis, including a study of driving performance. There is limited data regarding use of mefloquine in pregnancy. Early animal studies have documented teratogenic and embryotoxic effects associated with the use of high dose mefloquine. Two studies have shown a relatively high incidence of spontaneous abortions in mefloquine users. Cumulative evidence, however, is reassuring and has led the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) to sanction the use of mefloquine in pregnant women during the second and third trimesters. In conclusion, mefloquine prophylaxis is recommended for travelers to high risk areas of chloroquine resistant Plasmodium falciparum. The risk of malarial infection and the proven efficacy of mefloquine to prevent malaria should be weighed against the risk of drug associated adverse events.

Clinicoepidemiological study of imported malaria in travelers and immigrants to Madrid

BACKGROUND

The number of Spanish travelers visiting malaria endemic areas, and the number of immigrants from malarial countries arriving in Spain are continuously increasing. However, little information about imported cases in Spain is available.

METHODS

A prospective clinicoepidemiological study of imported cases of malaria diagnosed at a referral teaching hospital in Madrid, Spain.

RESULTS

Of the 160 patients, sixty (37.5%) were immigrants and 100 (62.5%) Spanish nationals. Malaria was acquired in Africa by 98.3% of immigrants and in 83.0% of travelers. Falciparum malaria accounted for 71.8% of the cases, P. vivax for 11.9%, P. ovale for 10.6% and P. malarie for 5. 0%. Eleven (6.9%) patients, all immigrants, were asymptomatic. Severe complications were recorded in 17 (10.6%): 7, severe anemia; 3, cerebral malaria; 2, renal failure; 1, spontaneous splenic rupture; 1, acute pulmonary edema; 1, sepsis; 1, acute cerebrovascular accident; and 1, disseminated intravascular coagulation. There were no fatal cases. Among the 100 Spanish nationals, 44% did not follow any prophylaxis, 29% followed a correct prophylaxis, 27% were considered defaulters, and 39% took self-treatment without cure.

CONCLUSIONS

There is a changing pattern of imported malaria in Madrid, with one third occurring in immigrants and two thirds in nationals. This data provides information about the reemergence of imported malaria to Europe.

Risk of malaria in visitors to the Kruger National Park, South Africa

BACKGROUND

The risk of malaria to visitors to South Africa's nature reserves is unknown. Current recommendations for travelers are based on malaria incidence rates in local communities. These rates may well overestimate travelers' malaria risk and lead to unnecessary use of antimalarial prophylaxis with associated drug-related adverse events. This study investigated the incidence of malaria in visitors to South Africa's Kruger National Park (KNP).

METHODS

Postal questionnaires were sent to the cohort of visitors staying in the KNP during April 1996, 6 to 8 weeks after they returned to their homes. Nonrespondents received duplicate questionnaires 8 weeks later. Responses from 3267 groups, representing 11,107 visitors (56. 8%) allowed determination of the malaria attack rate in this group of travelers and assessment of associations between malaria risk and a number of factors, including type of accommodation used during the visit; duration of stay; use of chemoprophylaxis; and use of personal protection measures. All travelers indicating that they had suffered an episode of malaria following their visit were telephonically contacted and their health providers traced to determine the basis of diagnosis and clinical outcome.

RESULTS

One clinically suspected and four confirmed cases of Plasmodium falciparum malaria among the visitors suggest a low attack rate of 4. 5 cases per 10,000 visitors during April, the highest risk month for malaria in South Africa. No association was found between malaria risk and accommodation type, duration of stay, use and type of chemoprophylaxis, and use and number of personal protection measures.

CONCLUSIONS

These findings confirm the importance of careful assessment of local malaria risk before individualized advice is provided to travelers.

Chemoprophylaxis compliance in travelers with malaria

Much effort and resources have been focused on improving or evolving antimalarial prophylactic regimens in order to reduce the increasing problems of malaria infection in nonimmune travelers to malaria endemic regions. Falciparum malaria in travelers returned from Africa has been attributed to reduced efficacy of chloroquine against chloroquine-resistant strains of Plasmodium falciparum (CRPF). Reported prophylaxis use by tourists from East Africa suggests only 52% admit taking their chemoprophylaxis without any missed doses. The effect of noncompliance with chloroquine (CQ) or proguanil (PG) in East Africa has been estimated as equivalent to taking no prophylaxis at all. The influence of poor compliance and/or parasite resistance on the changing pattern of malaria among travelers needs to be understood if methods of reducing morbidity are to be identified. In a number of studies, prophylaxis compliance in travelers has been collected by self-administered questionnaires from which prophylaxis efficacy of drug regimens has been calculated. The interpretation of drug efficacy has hinged on drug compliance and is controversial. We have addressed the role of chemoprophylaxis compliance in travelers with malaria using a prospective study of 368 malaria patients attending the Hospital for Tropical Diseases by examining their travel history and reported prophylaxis compliance compared to their actual plasma drug levels. This has enabled us to characterize the role of CRPF and poor compliance in the etiology of breakthrough malaria in travelers.

Malaria Chemoprophylaxis in German Tourists: A Prospective Study on Compliance and Adverse Reactions

Background: The number of tourists visiting malaria endemic regions is continuously increasing. The risk of aquiring malaria infection can largely be prevented by the regular use of chemoprophylactic drugs combined with using protective measures against mosquito bites. In a prospective study we wished to determine the tolerability of chemoprophylactic drugs and the factors that influence compliance with malaria chemoprophylaxis and antimosquito measures. Method: German travelers (n = 6504) who attended the Berlin Institute of Tropical Medicine in Berlin for pretravel medical advice were interviewed by phone 4 weeks after their journeys about compliance with the recommended malaria chemoprophylaxis and the incidence of side effects. Results: Compliance was better with mefloquine (94.5%) than with chloroquine (85.9%) (p<.001) or chloroquine plus proguanil (79.8%) (p<.001). Compliance was influenced by the purpose of travel, duration of stay, places of stay, and adverse reactions. Side effects occurred in 20.6% of the travelers who took chemoprophylactic drugs. There was no significant difference in the incidence of side effects between the three drug regimens, but people who took mefloquine more often reported neuropsychiatric reactions (6.5% versus 3.9% with chloroquine and 3.6% with chloroquine and proguanil; p<.001)). Side effects were usually mild to moderate and in no instance required hospitalization. People who took their drugs with meals less often reported side effects (15.2%) (p<.01). Conclusion: The knowledge of user profiles (and particular factors that presage side effects and noncompliance) may help us to improve pretravel counseling, thereby reducing the risk that travelers may acquire malaria infection.

Malaria and Casual Sex: What Travelers Know and How They Behave

Background: Travelers to the tropics have been reported to comply poorly with recommendations regarding malaria and AIDS. This study addresses the problem of influencing travelers' behavior through different approaches to conveying advice. Method: 3509 people attending a large travel clinic were randomly allocated to different interventions, including brochures about the implications of "sex tourism" and the possibility of participating in a contest assessing knowledge of malaria and AIDS. A comparison group (n = 607) of travelers to Kenya was contacted at an airport. Anonymous, self-administered questionnaires were sent to all travelers after their return. Results: Compliance with chemosuppressive regimen for malaria was 87%. Well-informed travelers did not protect themselves more efficiently against malaria. The efficacy of a given intervention was found to vary according to the age, sex, or travel experience of the participants. Of travelers, 51% reported casual sex abroad (M/F: 69/31). Thirty-eight percent of these contacts were unprotected. Casual sex abroad and condom use were correlated with a history of casual sex in the home country. Condom use was especially low in young women, who were also more likely to have casual sex with fellow travelers than with local partners. Eight percent of the "sex tourism" brochure readers had engaged in casual sex with local partners (all travelers, 4%). Conclusions: Lack of knowledge does not appear to be the problem. Travelers need to be motivated to put their knowledge into practice. Our results suggest that risks relating to malaria and AIDS are perceived in a different manner and that counseling should be individualized. Contest questions can help start a discussion on ethical and health-responsible behavior. The target group of the "sex tourism" brochure was reached, but their behavior appears not to have changed. Objective criteria can help physicians recognize "high-risk" travelers. Travelers need to be made aware that they may encounter environments conducive to risky behavior and that, while abroad, they may react in unexpected ways.

Malaria in Nonimmune Travelers: A Synopsis of History, Symptoms, and Treatment in 160 Patients

With the current increase of international travel to tropical endemic areas, the incidence of malaria being imported into nonendemic countries has increased significantly. Disagreement concerning malaria chemoprophylaxis and inadequate knowledge of malarious areas, morbidity, and pretravel advise has led to confusion among both health professionals as well as travelers. Therefore, this study was conducted to investigate malaria imported into Germany by identifying the high-risk endemic areas, clinical presentations, and chemoprophylactic and therapeutic regimens related to reported cases. Between 1990 and 1993, the 160 nonimmune travelers, all German nationals or residents for more than 10 years, presenting to our travel clinic with microscopically confirmed malaria were investigated. For each, the travel history, chemoprophylaxis used during travel, symptoms, pathological diagnosis, and treatment efficacy were analyzed. Africa (73%), Asia (21%), and Central South America (6%) were the endemic countries visited by our patients, of whom only 3% used the chemoprophylaxis recommended for their destination. Plasmodium falciparum was the most common pathogen, found in more than half of our patients, and P. vivax (29%), P. ovale (6%), P. malariae (6%), a mixed infection with P. falciparum and P. vivax (3%) were also detected. All patients presented with fever and headaches, a majority with profuse night sweats, insomnia, arthralgias, and myalgias, and diarrhea and abdominal cramps were experienced in 13% and 8%, respectively. In falciparum malaria, a recrudescence was observed in all patients who received chloroquine only, whereas quinine, halofantrine, and mefloquine were highly effective. In vivax malaria, a relapse rate of 14% was noted in patients treated with the currently recommended regimen of chloroquine and primaquine. Visitors to endemic countries, especially Africa, are of significant risk. Given the low compliance rate of chemoprophylaxis, a high precentage of malaria in our patients could have been avoided by an appropriate prophylaxis regimen and optimal pretravel counseling.

West African Immigrants and New Patterns of Malaria Imported to North Eastern Italy

With the settlement of increasing numbers of immigrants from tropical African countries into Italy over the last decade, the epidemiologic pattern of imported malaria underwent significant change. Italian immigrants originating from endemic areas who revisit their country of origin have exhibited an increasing incidence of malaria: the Italian Ministry of Health recorded an increase of from 14% in 1986 to 40.4% in 1991. This retrospective study reviews the epidemiology of all malaria cases recorded from 1988 to 1991 in a regional reference center in North Eastern Italy. Epidemiologic factors, including the details of their travel experience, were examined for all cases, and the relation of immigrants to Italian-born citizens were compared. Of the 100 cases recorded during this period, 36 were diagnosed in 1988-1989 and 64 in 1990-1991. Immigrants accounted for six times more cases during the latter than during the former time period. Compared to nonimmune short-term travelers, immigrants experienced significantly milder forms of the disease and lower levels of parasitemia (Plasmodium falciparum) on admission. Notably, 10 cases of malaria in immigrants were not recognized at first observation on microbiology. With the advent of this new risk group of immigrants that originate from endemic countries, especially those making occasional short visits to their native countries, this new epidemiologic profile of malaria imported into Italy shows the need for improvement in the areas of prophylaxis, pretravel education, and diagnostic services.

The diagnostic histopathologic features of ocular malaria

BACKGROUND

The ocular complications in patients with malaria have been studied clinically by many investigators, but the histopathologic changes were rarely described and generally regarded as nonspecific.

METHODS

The eye of a 53-year-old man who died of chloroquine-resistant Plasmodium falciparum malaria was studied by brightfield and polarized light microscopy.

FINDINGS

An epibulbar hemorrhage that involved the conjunctiva, episclera, and tendinous insertion of the medial rectus muscle was present. Cytoadherence and rosetting of the parasitized erythrocytes were observed within the partially occluded lumens of small retinal and uveal blood vessels. The birefringence of hemozoin (malarial pigment) within the lumens of small ocular blood vessels and in the hemorrhagic epibulbar area was demonstrated by polarized light.

CONCLUSION

Birefringent hemozoinemia in vascular lumens of ocular tissues indicates systemic malarial infestation by any of the four species of malaria. Cytoadherence and rosetting of the parasitized erythrocytes inside ocular capillaries and venules is diagnostic of P. falciparum and is an important cause of ocular hemorrhage.

Structure-activity relationships and modes of action of 9-anilinoacridines against chloroquine-resistant Plasmodium falciparum in vitro

An in vitro investigation of the structure-activity profiles for a range of 9-anilinoacridines on drug-resistant Plasmodium falciparum is reported. C-3, 6-diamino substitution, low lipophilicity, and high pKa values substantially increased the activities of the 9-anilinoacridines tested. There appeared to be no correlation between DNA binding and antimalarial activity. 3,6-Diamino-1'-amino-9-anilinoacridine (compound 13) was the most active compound tested; it had a 50% inhibitory concentration of 25 nM. In vitro mammalian cell growth assays showed compound 13 to be one of the least cytotoxic 9-anilinoacridines (50% inhibitory concentration, 15 microM). Both compound 13 and the antimalarial drug pyronaridine inhibited the decatenation activity of P. falciparum DNA topoisomerase II at concentrations of 10 and 11 microM, respectively.