Gabriele Peyerl-Hoffmann

Severe Dengue Virus Infection in Travelers: Risk Factors and Laboratory Indicators

BACKGROUNDnDengue fever is the most common arboviral disease in travelers. In countries where dengue virus is endemic, sequential (secondary) infections with different dengue virus serotypes are associated with disease severity. Data on severity and secondary infection rates in a population of travelers are lacking.nnnMETHODSnIntensified surveillance of dengue fever in travelers was performed within the European Network on Surveillance of Imported Infectious Diseases. Data were collected at 14 European clinical referral centers between 2003 and 2005.nnnRESULTSnA total of 219 dengue virus infections imported from various regions of endemicity were reported. Serological analysis revealed a secondary immune response in 17%. Spontaneous bleeding was observed in 17 (8%) patients and was associated with increased serum alanine and aspartate aminotransferase levels and lower median platelet counts. Two (0.9%) patients fulfilled the World Health Organization (WHO) case definition for dengue hemorrhagic fever. However, 23 (11%) travelers had severe clinical manifestations (internal hemorrhage, plasma leakage, shock, or marked thrombocytopenia). A secondary immune response was significantly associated with both spontaneous bleeding and other severe clinical manifestations.nnnCONCLUSIONSnIn travelers, severe dengue virus infections are not uncommon but may be missed if the WHO classification is strictly applied. High liver enzyme levels and low platelet counts could serve as indicators of disease severity.

Use of a Simple Criteria Set for Guiding Echocardiography in Nosocomial Staphylococcus aureus Bacteremia

BACKGROUNDnInfective endocarditis (IE) is a severe complication in patients with nosocomial Staphylococcus aureus bacteremia (SAB). We sought to develop and validate criteria to identify patients at low risk for the development of IE in whom transesophageal echocardiography (TEE) might be dispensable.nnnMETHODSnConsecutive patients with nosocomial SAB from independent cohorts in Europe (Invasive S. aureus Infection Cohort [INSTINCT]) and North America (S. aureus Bacteremia Group [SABG]) were evaluated for the presence of clinical criteria predicting an increased risk for the development of IE (ie, prolonged bacteremia of >4 days duration, presence of a permanent intracardiac device, hemodialysis dependency, spinal infection, and nonvertebral osteomyelitis). Patients were observed closely for clinical signs and symptoms of IE during hospitalization and a 3-month follow-up period.nnnRESULTSnIE was present in 13 (4.3%) of 304 patients in the INSTINCT cohort and in 40 (9.3%) of 432 patients in the SABG cohort. Within 14 days after the first positive blood culture result, echocardiography was performed in 39.8% and 57.4% of patients in the INSTINCT and SABG cohorts, respectively. In patients with IE, the most common clinical prediction criteria present were prolonged bacteremia (69.2% vs 90% for INSTINCT vs SABG, respectively) and presence of a permanent intracardiac device (53.8% vs 32.5%). In total, 13 of 13 patients in the INSTINCT cohort and 39 of 40 patients in the SABG cohort with documented IE fulfilled at least 1 criterion (sensitivity, 100% vs. 97.5%; negative predictive value, 100% vs 99.2%).nnnCONCLUSIONSnA simple criteria set for patients with nosocomial SAB can identify patients at low risk of IE. Patients who meet these criteria may not routinely require TEE.

Genetic diversity of Plasmodium falciparum and its relationship to parasite density in an area with different malaria endemicities in West Uganda.

Field populations of Plasmodium falciparum can be effectively genotyped by PCR‐amplification of selected fragments of the Merozoite Surface Proteins 1 and 2 (MSP1 and MSP2). Genetic diversity of P. falciparum populations in areas with different transmission levels (holo‐ vs. mesoendemic) was investigated in Kabarole District, West Uganda. 225 samples positive for P. falciparum were analysed by amplification of polymorphic regions and classified according to prevalence of allelic families. A large number of alleles was detected for each locus: 22 for MSP1 block 2 and 24 for MSP2 and, 175 (78%) of MSP1 alleles and 143 (64%) of MSP2 showed multiple infections within a range of 2–8 clones. Significant differences between holoendemic and mesoendemic areas in regards of population structure and number of multiclonal infections of P. falciparum were not apparent. However, a significant correlation between parasite density, selected MSP2 loci and differences between parasite density in monoclonal vs. multiclonal infections occurred. Multiplicity of infection was age‐dependent.

Screening for Mutations Related to Atovaquone/ Proguanil Resistance in Treatment Failures and Other Imported Isolates of Plasmodium falciparum in Europe

BACKGROUNDnTwo single-point mutations of the Plasmodium falciparum cytochrome b gene (Tyr268Asn and Tyr268Ser) were recently reported in cases of atovaquone/proguanil (Malarone) treatment failure. However, little is known about the prevalence of codon-268 mutations and their quantitative association with treatment failure.nnnMETHODSnWe set out to assess the prevalence of codon-268 mutations in P. falciparum isolates imported into Europe and to quantify their association with atovaquone/proguanil treatment failure. Isolates of P. falciparum collected by the European Network on Imported Infectious Disease Surveillance between April 2000 and August 2003 were analyzed for codon-268 mutations, by use of polymerase chain reaction-restriction fragment-length polymorphism.nnnRESULTSnWe successfully screened 504 samples for the presence of either Tyr268Ser or Tyr268Asn. One case of Ser268 and no cases of Asn268 were detected. Therefore, we can be 95% confident that the prevalence of Ser268 in the European patient pool does not exceed 0.96% and that Asn268 is less frequent than 0.77%. In 58 patients treated with atovaquone/proguanil, Tyr268Ser was present in 1 of 5 patients with treatment failure but in 0 of 53 successfully treated patients.nnnCONCLUSIONSnTyr268Ser seems to be a sufficient, but not a necessary, cause for atovaquone/proguanil treatment failure. The prevalence of both codon-268 mutations is currently unlikely to be >1% in the European patient pool.

Molecular surveillance of drug resistance through imported isolates of Plasmodium falciparum in Europe

BackgroundResults from numerous studies point convincingly to correlations between mutations at selected genes and phenotypic resistance to antimalarials in Plasmodium falciparum isolates. In order to move molecular assays for point mutations on resistance-related genes into the realm of applied tools for surveillance, we investigated a selection of P. falciparum isolates that were imported during the year 2001 into Europe to study the prevalence of resistance-associated point mutations at relevant codons. In particular, we tested for parasites which were developing resistance to antifolates and chloroquine. The screening results were used to map the prevalence of mutations and, thus, levels of potential drug resistance in endemic areas world-wide.Results337 isolates have been tested so far. Prevalence of mutations that are associated with resistance to chloroquine on the pfcrt and pfmdr genes of P. falciparum was demonstrated at high levels. However, the prevalence of mutations associated with resistance to antifolates at the DHFR and DHPS genes was unexpectedly low, rarely exceeding 60% in endemic areas.ConclusionsConstant screening of imported isolates will enable TropNetEurop to establish a screening tool for emerging resistance in endemic areas.

Therapy of uncomplicated falciparum malaria in Europe: MALTHER – a prospective observational multicentre study

BackgroundMalaria continues to be amongst the most frequent infectious diseases imported to Europe. Whilst European treatment guidelines are based on data from studies carried out in endemic areas, there is a paucity of original prospective treatment data. The objective was to summarize data on treatments to harmonize and optimize treatment for uncomplicated malaria in Europe.MethodsA prospective observational multicentre study was conducted, assessing tolerance and efficacy of treatment regimens for imported uncomplicated falciparum malaria in adults amongst European centres of tropical and travel medicine.ResultsBetween December 2003 and 2009, 504 patients were included in 16 centres from five European countries. Eighteen treatment regimens were reported, the top three being atovaquone-proguanil, mefloquine, and artemether-lumefantrine. Treatments significantly differed with respect to the occurrence of treatment changes (pu2009=u20090.005) and adverse events (pu2009=u20090.001), parasite and fever clearance times (pu2009<u20090.001), and hospitalization rates (pu2009=u20090.0066) and durations (pu2009=u20090.001). Four recrudescences and two progressions to severe disease were observed. Compared to other regimens, quinine alone was associated with more frequent switches to second line treatment, more adverse events and longer inpatient stays. Parasite and fever clearance times were shortest with artemether-mefloquine combination treatment. Vomiting was the most frequent cause of treatment change, occurring in 5.5% of all patients but 9% of the atovaquone-proguanil group.ConclusionsThis study highlights the heterogeneity of standards of care within Europe. A consensus discussion at European level is desirable to foster a standardized management of imported falciparum malaria.

Prevalence of polymorphisms in the dihydrofolate reductase and dihydropteroate synthetase genes of Plasmodium falciparum isolates from southern Mauritania

The increasing resistance of Plasmodium falciparum in the treatment of uncomplicated malaria with pyrimethamine/sulphadoxine has been associated in several studies with the occurrence of point mutations in the genes of dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS). In this study, the prevalence of these mutations was examined in samples from south‐east Mauritania, where atypically strong rainfalls in 1998 and 1999 led to a severe outbreak of falciparum malaria. We analysed 386 samples by polymerase chain reaction (PCR) for infection with P. falciparum, of which 162 (41.97%) were positive. These isolates were examined for point mutations in the genes of DHFR (codons 16, 51, 59, 108 and 164) and DHPS (codons 436, 437, 540, 581 and 613) by nested PCR and subsequent mutation‐specific restriction enzyme digest. We found a low overall prevalence of DHFR gene mutations (up to 18.6% of isolates), but a high overall prevalence of DHPS gene mutations (up to 49.1% of isolates). Thus, emerging resistance to antifolate drugs may be expected to develop soon in the investigated area. This study demonstrates the utility of simple, relatively rapid and inexpensive molecular methods and their application in surveillance programmes. Testing for prevalence of point mutations conferring antifolate resistance might help to identify the developing of drug resistance at a very early stage.

Molecular surveillance of the antifolate-resistant mutation I164L in imported african isolates of Plasmodium falciparum in Europe: sentinel data from TropNetEurop

BackgroundMalaria parasites that carry the DHFR-mutation I164L are not only highly resistant to sulfadoxine-pyrimethamine but also to the new antimalarial drug chlorproguanil-dapsone. The spread of this mutation in Africa would result in a public health disaster since there is a lack of effective alternatives that are both affordable and safe. Up to now, this mutation has only been described in Asian and Latin-American countries. The objective of this study was to assess the prevalence of this mutation in African isolates of Plasmodium falciparum that have been imported into Europe through travellers.MethodsTropNetEurop is a network for the surveillance of travel-associated diseases and seems to cover approximately 12% of all malaria cases imported into Europe. Within this network we screened 277 imported African isolates of P. falciparum with the help of PCR- and enzyme-digestion-methods for the antifolate-resistant mutation I164L.ResultsThe I164L mutation was not detected in any of the isolates tested.DiscussionContinuous molecular surveillance of mutations in P. falciparum, as it is practised within TropNetEurop, is an essential tool for the understanding and early detection of the spread of antimalarial drug resistance in Africa.

Differences in clinical manifestations of imported versus autochthonous leptospirosis in Austria and Germany.

Leptospirosis, a zoonosis occurring worldwide, has a broad spectrum of clinical manifestations. Recently, various countries observed an increase of severe anicteric cases. In Austria and Germany, growing numbers of imported cases are notified in addition to autochthonous infections. The aim of this study was to assess whether imported and autochthonous cases differ in clinical manifestations and outcome. We retrospectively analyzed 24 imported and 35 autochthonous cases treated in six infectious disease units between 1998 and 2008. To compare disease severity, patients were classified according to established independent risk factors for fatal outcome. Although severe leptospirosis (i.e., presence of > or = 1 independent risk factors for death) occurred in similar proportions of imported (67%) and autochthonous (86%) infections (P = 0.1), imported cases were significantly fewer icteric (13% versus 69%; P < 0.0001). In conclusion, an increasing incidence of severe anicteric imported cases of leptospirosis should be anticipated with rising global travel activities.

Plasmodium falciparum: use of a NANP19 antibody-test for the detection of infection in non-immune travellers.

Circumsporozoite (CS) antibodies are a reliable serological marker for the infection of Plasmodium falciparum. The purpose of this investigation was to construct and evaluate an enzyme‐linked immunosorbent assay test for the detection of CS antibodies. While the sensitivity of the newly developed test reached 78%, the specificity was 99%. In addition, the optimized kit was used to test for infection with P. falciparum in 1903 travellers that were recruited from a prospective study for malaria chemoprophylaxis. Sixty‐six of the 1903 patients (3.5%) showed elevated CS antigen antibody titres. However, seroconversion could only be demonstrated in 18 (0.95%) patients. Among those seroconverting, there was a significantly higher percentage of male travellers (1.28%) than female travellers (0.56%). Positive reactions were more frequent among returnees from West and East Africa (1.49 and 1.14%, respectively) than among those from other endemic areas, e.g. South America (n=0). Despite its limited sensitivity, this newly developed kit for CS antibody testing may be a valuable tool for the estimation of the risk for travellers in malarious regions to acquire an infection with P. falciparum. It may also be useful for the determination of the efficacy of malaria chemoprophylaxis for inhibiting outbreak of disease.