Epidemiology and clinical features of vivax malaria imported to Europe: sentinel surveillance data from TropNetEurop

Molecular diagnostic and surveillance tools for global malaria control

Malaria is the most devastating parasitic infection in the world, annually causing over 1 million deaths and extensive morbidity. The global burden of malaria has increased over the last several decades, as have rates of imported malaria into non-endemic regions. Rapid and accurate diagnostics are a crucial component of malaria control strategies, and epidemiological surveillance is required to monitor trends in malaria prevalence and antimalarial drug resistance. Conventional malaria diagnostic and surveillance tools can be cumbersome and slow with limitations in both sensitivity and specificity. New molecular techniques have been developed in an attempt to overcome these restrictions. These molecular techniques are discussed with regard to their technical advantages and disadvantages, with an emphasis on the practicality of implementation in malaria-endemic and non-endemic regions.

Neglect of Plasmodium vivax malaria

Plasmodium vivax infects 130-435 million of the 2.6 billion people living at risk of infection. Recent studies suggest that vivax malaria can become lethal in a similar way to severe falciparum malaria. First-line therapies remain unchanged after 50 years. Despite evidence of failing chloroquine efficacy, little work has assessed the problem or explored alternative therapies. Primaquine treatment, the only therapeutic option against relapse, might also be failing. No licensed primary chemoprophylactic agent protects travelers from relapse. Misdiagnosis of species now affects clinical decisions resulting in inadequate therapy for P. falciparum and P. vivax. All of these factors demonstrate the lack of research on P. vivax.

Pilot-study on GIS-based risk modelling of a climate warming induced tertian malaria outbreak in Lower Saxony (Germany)

The area under investigation, Lower Saxony (Northwest Germany), is a former malaria region with highest incidences along the coastal zones. Malaria had finally become extinct in the early 1950s. Subsequently, further scientific investigations in that field declined. Nevertheless, the vector in shape of Anopheles mosquitoes has still been present in Lower Saxony. Thus, the question arises, whether a new autochthon transmission could take place if the pathogen is introduced again and could develop in Anopheles mosquitoes. Answering this question was the first aim of the investigation at hand. The second one was to examine the spatial and temporal structure of potential transmissions in respect to the predicted increase of air temperatures according to the IPCC scenarios. To answer these questions, current information about Anophelinae and their distribution and habitat preferences within Germany were collected by literature research as well as temperature measurements and Anopheles findings were compiled from the German Weather Survey and the Niedersächsisches Landesamt für Okologie (NLO), respectively. The results reveal a climate warming between the 30-years period from 1961 to 1990 and the years between 1985 and 2004. Induced by higher monthly mean temperatures, the risk of a malaria tertiana transmission is consequently increasing for Lower Saxony as temperature is the determining variable of the mathematical model. The study could demonstrate that most parts of the country are located within a 2 months lasting transmission zone. Although Germany is not an endemic malaria zone, the pathogen can enter the country most likely by infected people or imported mosquitoes that transport it in their guts.

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.

Plasmodium vivax in Africa: hidden in plain sight?

People who live in tropical Africa, south of the Sahara, are predominantly negative for the Duffy blood-group antigen, which mediates invasion of reticulocytes by Plasmodium vivax. Recent reports of a parasite that was molecularly diagnosed as P. vivax from populations who are suspected, or known, to be Duffy negative confound a large body of evidence that states that invasion of P. vivax requires the Duffy antigen. If confirmed, one of several possible explanations is that P. vivax, which originated in Asia, is now evolving to exploit alternate invasion receptors in Africa.

The basic principles of migration health: population mobility and gaps in disease prevalence

Currently, migrants and other mobile individuals, such as migrant workers and asylum seekers, are an expanding global population of growing social, demographic and political importance. Disparities often exist between a migrant population's place of origin and its destination, particularly with relation to health determinants. The effects of those disparities can be observed at both individual and population levels. Migration across health and disease disparities influences the epidemiology of certain diseases globally and in nations receiving migrants. While specific disease-based outcomes may vary between migrant group and location, general epidemiological principles may be applied to any situation where numbers of individuals move between differences in disease prevalence. Traditionally, migration health activities have been designed for national application and lack an integrated international perspective. Present and future health challenges related to migration may be more effectively addressed through collaborative global undertakings. This paper reviews the epidemiological relationships resulting from health disparities bridged by migration and describes the growing role of migration and population mobility in global disease epidemiology. The implications for national and international health policy and program planning are presented.

Imported malaria in Jakarta, Indonesia: passive surveillance of returned travelers and military members postdeployment

BACKGROUND

Autochthonous malaria does not currently occur in Jakarta, the most populous city in Indonesia. Military, forestry, mining, and tourist activities draw Jakarta residents to distant parts of the archipelago with high rates of malaria. Although malaria is a reportable disease in Jakarta, little has been published.

METHODS

We collected demographic and travel information from patients in Jakarta with microscopically confirmed malaria from January 2004 to February 2005, using a standardized data collection form. These results were compared to regional rainfall statistics and transit patterns of Jakarta residents to and from rural areas.

RESULTS

Data from 240 patients were collected. Aceh Province was the travel destination most commonly recorded for military members, while Papua and Bangka Island were the most frequently cited by civilians. Plasmodium falciparum accounted for 53% of cases, of which 15% had detectable gametocytemia. The most common admission diagnoses were malaria (39%), febrile illness not otherwise specified (23%), viral hepatitis (19%), and dengue (11%). The median time from admission to microscopic diagnosis was 2 days for civilian patients and 2.5 days for military patients. The highest number of cases occurred in May, July, and December with the nadir in October.

CONCLUSIONS

The diagnosis of malaria may be overlooked and therefore delayed, in nonendemic areas such as Jakarta. Travel destinations associated with contracting malaria vary significantly for civilian and military populations. The factors affecting the peak months of importation likely include rainfall, holiday transit, military flight availability, and referral center locations.

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.

Malaria prophylaxis policy for travellers from Europe to the Indian Subcontinent

Analysis of malaria imported into eight European countries from the Indian sub-continent (ISC) (India, Pakistan, Bangladesh and Sri Lanka) led to a consensus statement on the use of chemoprophylaxis within TropNetEurop. The proportion of cases from the ISC in 2004 ranged from 1.4%–4.6% of total imported cases. Plasmodium falciparum cases reported from the eight countries was only 23 (13% of all cases from the region). Total malaria reports between 1999–2004 fell from 317 to 180. The risk of malaria in UK residents visiting the region was > 1 case per 1,000 years exposed. The group recommended non-selective prescribing of chemoprophylaxis for visitors to India, Pakistan, Bangladesh and Sri Lanka should be dropped.

Patterns of imported malaria at the academic medical center, Amsterdam, the Netherlands

BACKGROUND

In the Netherlands, cases of imported malaria peaked in the late 1990s to around 500 (60% Plasmodium falciparum) annually. About 30% to 40% of all cases and 57% to 69% of the falciparum cases presented in the Academic Medical Center, Amsterdam. In 1991 to 1994, a shift in population groups to more semi-immune patients, mostly settled immigrants visiting friends and relatives (VFRs), was noticed, when compared to 1979 to 1988. This study shows the ongoing trend in 2000 to 2002.

METHODS

All the patients diagnosed with malaria in the Academic Medical Center, Amsterdam, during 2000 to 2002 were analyzed. Nonimmune and semi-immune patients were analyzed separately.

RESULTS

A total of 302 patients were diagnosed with malaria: 207 (69%) were male; mean age was 34.0 years (range 1-74 years). Of the 302 patients, 105 (35%) were nonimmune travelers and 197 (65%) were considered semi-immune. In 248 (82%) patients, P falciparum was found. In 28 (9.3%), 15 (5.0%), and 6 (2.0%) cases, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae were diagnosed, respectively. Of the 248 falciparum cases, 233 (94%) were infected in sub-Saharan Africa; 90% of them had a parasitemia and <2 and 4% had a parasitemia exceeding 5% (maximum 43.7%). The majority of the falciparum cases (96%) were diagnosed within 30 days after return. The number of nonimmune patients with falciparum malaria decreased sharply from 42 in 2000 to 31 in 2001 to 13 in 2002, accounting for the decrease in all malaria cases, from 118 in 2000 to 82 in 2002. Fifty-four percent of vivax infections were acquired in Southeast Asia and 46% in Latin America and sub-Saharan Africa; 71% of the patients presented after 30 days (delayed primary attacks). All the P ovale infections were acquired in sub-Saharan Africa (73% delayed primary attacks).

CONCLUSIONS

During 2000 to 2002, the total number of patients with falciparum malaria was steadily decreasing due to a decrease in nonimmune patients. The number of semi-immune patients, mostly VFRs and visitors, remained stable. The increasing use of more convenient chemoprophylactic drugs, like atovaquone/proguanil, appears to improve compliance in those who can afford the drug.

Impact of imported malaria on the burden of disease in northeastern Venezuela

BACKGROUND

Many countries throughout the world are reporting an increasing number of imported malaria cases. It is now well documented that population movements play an important role in the spread and introduction of malaria infection in nonendemic areas.

METHODS

We evaluated the contribution of imported malaria to the overall malaria burden of disease in an already endemic malaria region in Venezuela, where malaria is exclusively caused by Plasmodium vivax. To estimate the magnitude of this contribution, we retrospectively analyzed cases of imported malaria in Sucre, Venezuela, during a 10-year period (1987-1998).

RESULTS

During this period, 1,755 (3.8% of the total) cases of imported malaria were identified. Most of these cases were imported from the Meridian states into Sucre. In Latin America, a major factor in the reemergence and spread of malaria is human migration. Surveillance of imported cases of malaria in Venezuela would allow us to continue evaluating population migration dynamics and its epidemiologic impact on malaria transmission.

CONCLUSION

Enhanced surveillance, such as the one shown in this study, would help the early identification of nonindigenous Plasmodium species and also of resistant Plasmodium strains with a potential to spread locally. Population mobility and imported malaria cases may add to the magnitude of malaria burden in some regions of Latin America. Furthermore, malaria treatment guidelines at local and national levels need to incorporate imported malaria cases in their treatment algorithms and into chemoprophylactic recommendations for travelers.

Malaria risk in travelers

Imported malaria has been an increasing problem in several Western countries in the last 2 decades. To calculate the risk factors of age, sex, and travel destination in Swedish travelers, we used data from the routine reporting system for malaria (mixture of patients with and without adequate prophylaxis), a database on travel patterns, and in-flight or visa data on Swedish travelers of 1997 to 2003. The crude risk for travelers varied from 1 per 100,000 travelers to Central America and the Caribbean to 357 per 100,000 in central Africa. Travelers to East Africa had the highest adjusted odds ratio (OR = 341, 95% confidence intervals [CI] 134-886) for being reported with malaria, closely followed by travelers to central Africa and West Africa. Male travelers as well as children <1-6 years of age had a higher risk of being reported with malaria (OR = 1.7, 95% CI 1.3-2.3 and OR = 4.8, 95% CI 1.5-14.8) than women and other age groups.

Imported malaria at an inner-city hospital in the United States

BACKGROUND

More than 1000 cases of malaria are reported to the Centers for Disease Control and Prevention each year among travelers or immigrants.

METHODS

Retrospective study of patients with malaria seen at Grady Memorial Hospital in Atlanta, Georgia, between October 1988 and September 2000.

RESULTS

One hundred twenty-six cases of malaria were diagnosed at Grady Memorial Hospital during the study period. Fourteen patients had seen a physician prior to coming to Grady Memorial Hospital, and in 71% the diagnosis was missed. Half had recently immigrated and half recently traveled to an endemic area, yet only 22% of travelers took prophylaxis. Plasmodium falciparum was the most commonly identified species (52.4%), followed by Plasmodium vivax (23.9%). Seventy-two patients (57.1%) required hospitalization. Presenting symptoms included fever (94%), chills (56%), nausea/vomiting (38%), headache (26%), and abdominal pain (26%). Most patients were diagnosed correctly on the day of admission (79%). Twelve patients (16.7%) had severe malaria, and their complications included severe anemia (9.7%), acute renal failure (4.2%), bleeding and/or disseminated intravascular coagulation (4.2%), shock (2.8%), seizures (2.8%), and hypoglycemia (2.8%). One patient died, and two pregnant women had premature deliveries. Median hospital stay was 3.9 days. One third of the hospitalized patients with P vivax failed to receive primaquine, and in 15% of patients with P falciparum, the treatment was considered to be inappropriate.

CONCLUSIONS

Although some patients with malaria have a benign course and a good outcome, many patients require hospitalization, and some have severe complications. Increased efforts are needed to educate travelers about the need for prophylaxis.