Tuberculosis resistance-conferring mutations with fitness cost among HIV-positive individuals in Uganda

BACKGROUND

Multidrug-resistant tuberculosis (MDR-TB) is considered to be less transmissible due to the fitness cost associated with drug resistance-conferring mutations in essential genes.

OBJECTIVE

To test the hypothesis that TB drug resistance-conferring mutations with fitness cost are more frequent among human immunodeficiency virus (HIV) positive than among HIV-negative patients.

DESIGN

We analysed all strains from the two TB drug resistance surveys conducted in Uganda between 2008 and 2011. Strains phenotypically susceptible to rifampicin and/or isoniazid were assumed to be wild-type; in all other cases, we performed whole-genome sequencing. Mutations at the rpoB531 and katG315 codons were considered without fitness loss, whereas other rpoB codons and non-katG were considered with fitness loss.

RESULTS

Of the 897 TB patients, 286 (32.1%) were HIV-positive. Mutations with fitness loss in HIV-positive and HIV-negative patients were respectively as follows: non-531 rpoB: 1.03% (n = 3), 0.71% (n = 4) (OR 1.46, 95%CI 0.58-3.68); non-katG: 0.40% (n = 1), 1.0% (n = 6) (OR 0.40, 95%CI 0.07-2.20); rpoB531: 1.49% (n = 4), 0.69% (n = 4) (OR 2.29, 95%CI 0.83-5.77); katG315: 3.86% (n = 11), 2.55% (n = 15) (OR 1.54, 95%CI 0.81-2.90). The odds of mutations with and without fitness cost were higher for patients with a history of previous anti-tuberculosis treatment.

CONCLUSIONS

Our data do not support the hypothesis that resistance-conferring mutations with fitness cost are likely to be often present in HIV-positive individuals.

Cost and cost-effectiveness of tuberculosis treatment shortening: a model-based analysis

Background

Despite improvements in treatment success rates for tuberculosis (TB), current six-month regimen duration remains a challenge for many National TB Programmes, health systems, and patients. There is increasing investment in the development of shortened regimens with a number of candidates in phase 3 trials.

Methods

We developed an individual-based decision analytic model to assess the cost-effectiveness of a hypothetical four-month regimen for first-line treatment of TB, assuming non-inferiority to current regimens of six-month duration. The model was populated using extensive, empirically-collected data to estimate the economic impact on both health systems and patients of regimen shortening for first-line TB treatment in South Africa, Brazil, Bangladesh, and Tanzania. We explicitly considered ‘real world’ constraints such as sub-optimal guideline adherence.

Results

From a societal perspective, a shortened regimen, priced at USD1 per day, could be a cost-saving option in South Africa, Brazil, and Tanzania, but would not be cost-effective in Bangladesh when compared to one gross domestic product (GDP) per capita. Incorporating ‘real world’ constraints reduces cost-effectiveness. Patient-incurred costs could be reduced in all settings. From a health service perspective, increased drug costs need to be balanced against decreased delivery costs. The new regimen would remain a cost-effective option, when compared to each countries’ GDP per capita, even if new drugs cost up to USD7.5 and USD53.8 per day in South Africa and Brazil; this threshold was above USD1 in Tanzania and under USD1 in Bangladesh.

Conclusion

Reducing the duration of first-line TB treatment has the potential for substantial economic gains from a patient perspective. The potential economic gains for health services may also be important, but will be context-specific and dependent on the appropriate pricing of any new regimen.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2064-3) contains supplementary material, which is available to authorized users.

Alignment of new tuberculosis drug regimens and drug susceptibility testing: a framework for action

New tuberculosis drug regimens are creating new priorities for drug susceptibility testing (DST) and surveillance. To minimise turnaround time, rapid DST will need to be prioritised, but developers of these assays will need better data about the molecular mechanisms of resistance. Efforts are underway to link mutations with drug resistance and to develop strain collections to enable assessment of new diagnostic assays. In resource-limited settings, DST might not be appropriate for all patients with tuberculosis. Surveillance data and modelling will help country stakeholders to design appropriate DST algorithms and to decide whether to change drug regimens. Finally, development of practical DST assays is needed so that, in countries where surveillance and modelling show that DST is advisable, these assays can be used to guide clinical decisions for individual patients. If combined judiciously during both development and implementation, new tuberculosis regimens and new DST assays have enormous potential to improve patient outcomes and reduce the burden of disease.

National anti-tuberculosis drug resistance study in Tanzania

OBJECTIVE

To assess the prevalence of anti-tuberculosis drug resistance in a national representative sample of tuberculosis (TB) patients in Tanzania according to recommended methodology.

DESIGN

Cluster survey, with 40 clusters sampled proportional to size, of notified TB patients from all diagnostic centres in the country.

RESULTS

The survey enrolled 1019 new and 148 retreatment patients. The adjusted prevalence of Mycobacterium tuberculosis strains resistant to any of the four first-line drugs in new patients was 8.3%, while the prevalence of multidrug-resistant TB (MDR-TB) was 1.1%. In retreatment patients, the crude prevalence for any resistance and for MDR-TB was respectively 20.6% and 3.9%. The prevalence of drug resistance did not differ in relapse patients compared to failure patients. These estimates are among the lowest in those African countries with an estimated level of drug resistance in the last 5 years.

CONCLUSION

The low levels of drug resistance in Tanzania are likely due to a well performing TB control programme and the absence of noticeable involvement of the private sector in TB treatment.

Organisation of a tuberculosis prevalence survey

Measuring tuberculosis (TB) prevalence trends provides information on progress towards the Millennium Development Goals. The World Health Organization recently published guidelines on assessing TB prevalence through population-based surveys. The current manuscript describes in detail the organisation of the field activities in such a survey. These activities need to be embedded in a strong organisational framework where the steering committee has the overall responsibility and the survey coordinator the day-to-day supervision. Field activities need to be tailored to the community, with respect to both time and place and direct involvement of community members. Frequent and well-described monitoring procedures need to be in place to be able to identify systematic and non-systematic errors at the earliest opportunity.

High tuberculosis prevalence in a psychiatric hospital in Vietnam

Little is known about tuberculosis (TB) prevalence in psychiatric hospitals in Vietnam, but prevalence may be higher than in the general population. We assessed the TB prevalence among in-patients of a psychiatric hospital in 2005 in Danang City, Vietnam. Of 300 in-patients, 70 had an abnormal X-ray or prolonged cough, and underwent sputum smear examinations. The prevalence of smear-positive TB was 0.33% (1/300, 95%CI 0.008-1.9). Twenty-three (7.7%) patients had X-ray lesions suggesting active TB and 22 (7.3%) had a history of TB treatment. TB prevalence was high in this psychiatric hospital, and TB infection control needs strengthening.

Tuberculosis drug resistance and HIV infection, the Netherlands

In the Netherlands during 1993-2001, multidrug-resistant tuberculosis among newly diagnosed patients was more frequent in those with HIV coinfection (5/308, 1.6%) than in those with no HIV infection (39/646, 0.6%; adjusted odds ratio 3.43, p=0.015). Four of the 5 patients coinfected with multidrug-resistant tuberculosis and HIV were foreign-born. DNA fingerprint analysis suggested that transmission had occurred outside the Netherlands.

Survival and relapse rate of tuberculosis patients who successfully completed treatment in Vietnam

SETTING

Reported tuberculosis (TB) cure rates are high in Vietnam with the 8-month short-course chemotherapy regimen. However, long-term treatment outcomes are unknown.

OBJECTIVE

To assess survival and relapse rates among patients successfully treated for new smear-positive pulmonary tuberculosis (PTB).

METHODS

A cohort of patients treated in 32 randomly selected districts in northern Vietnam were followed up 12-24 months after reported cure or treatment success for survival and bacteriologically confirmed relapse. Measurements included sputum smear examination, culture and interview for recent treatment history.

RESULTS

Of 304 patients included in the study, no information was available for 31 (10%) and 19 (6%) had died. Bacteriology results were available for 244 (80%). The median interval between treatment completion and follow-up was 19 months. Relapse was recorded in 21/244 (8.6%, 95%CI 5.4-13), including 9 (4%) with positive sputum smears, 3 (1%) with negative smears but positive culture and 9 (4%) who had started TB retreatment. Four of 12 culture-positive relapse cases (33%) had multidrug-resistant strains. If the definition of relapse was extended to include death, reportedly due to TB, the relapse proportion was 26/263 (9.9%, 95%CI 6.6-14).

CONCLUSION

A substantial proportion of patients (15%) had died or relapsed after being successfully treated for TB in northern Vietnam.

Tuberculosis epidemiology in six provinces of Vietnam after the introduction of the DOTS strategy

SETTING

Six provinces in Vietnam where the DOTS strategy was introduced in 1989.

OBJECTIVE

To assess the impact of improved tuberculosis (TB) control on TB epidemiology in Vietnam.

METHODS

Data from the surveillance system in the period 1990-2003 were analysed to assess trends of notification rates and the mean ages of notified cases. Data from repeated tuberculin surveys in the period 1986-2002 were estimated to assess the prevalence of TB infection, the annual risk of infection and its trend using various cut-off points in those with and without bacille Calmette-Guérin (BCG) scar.

RESULTS

Age-standardised notification rates in the period 1996-2003 declined significantly, by 2.6% to 5.9% per year, in five provinces. However, in four provinces notification rates in the age group 15-24 years increased significantly, by 4.5% to 13.6% per year, during this period. The mean age of newly diagnosed patients with smear-positive TB increased up to 1995 but decreased thereafter. The annual risk of TB infection showed a significant annual decrease (4.9% per year) in one province in surveys performed between 1986 and 1997, and in two provinces (6.6% and 4.7%) in surveys conducted between 1993 and 2002.

CONCLUSION

These data suggest limited impact to date of the DOTS strategy in Vietnam.

Evaluation of sputum smear microscopy in the National Tuberculosis Control Programme in the north of Vietnam

OBJECTIVE

To assess the yield of sputum smear microscopy and sex differences in the National Tuberculosis Control Programme in the north of Vietnam.

METHODS

Review of registers of 30 randomly selected laboratories (26 district, 4 provincial level).

RESULTS

The average daily workload per technician was 4.4 examinations in district and 5.3 examinations in provincial laboratories. To find one smear-positive case, 9.7 suspects were examined and 29.3 smears done. The smear-positive rate (mean 10.3%) was higher among men (11.6%) than among women (8.4%, P < 0.001). There were more men than women among tuberculosis (TB) suspects (male:female ratio 1.36, 95%CI 1.19-1.54), but even more so among smear-positive patients (1.89, 95%CI 1.64-2.14), irrespective of specimen quality and number of smears examined. Three smears were examined for 18,055 suspects (61.7%). The incremental gain was 33.5% and 4.9% for the second and third smear examination, respectively; 186 (95%CI 160-221) smears needed to be examined to find one additional case of TB with a third serial examination.

CONCLUSION

The diagnostic process seemed generally efficient. The male:female ratios suggest higher TB incidence in men rather than lower access to TB facilities for women. The third smear examination could be omitted.

Comparison of the parasitologic efficacy of amodiaquine and sulfadoxine-pyrimethamine in the treatment of Plasmodium falciparum malaria in the Bungoma District of western Kenya

The efficacy of amodiaquine (AQ) and sulfadoxine-pyrimethamine (SP) was assessed in 310 symptomatic children from western Kenya with uncomplicated Plasmodium falciparum malaria. A non-blinded, randomized, 14-day study was performed and parasitologic criteria were used. Of 310 patients included, 238 (77%) completed the study: 120 received AQ and 118 received SP. In those treated with AQ, there were sensitive (S) infections in 107 patients (89.2%, 95% confidence interval [CI] = 82.2, 94.1%), RI resistance in 10 (8.3%, 95% CI = 4.1, 14.8%), RII resistance in 1 (0.8%, 95% CI = 0, 4.6%), and RIII resistance in 2 (1.7%, 95% CI = 0.2, 5.9%). In those treated with SP, there were S infections in 74 patients (62.7%, 95% CI = 53.3, 71.4%), RI resistance in 21 (17.8%, 95% CI = 11.4, 25.9%), RII resistance in 11 (9.3%, 95% CI = 4.7, 16.1%), and RIII resistance in 12 (10.2%, 95% CI = 5.4, 17.1%). Resistance rates were consistently higher in the SP-treated patients (P < 0.001). Resistance to SP in this area has reached such levels that it should no longer be the first-line treatment. Alternative treatment, such as SP plus AQ combination treatment or artemisinin combination treatment, is urgently needed.

Association of tuberculin sensitivity in Dutch adults with history of travel to areas of with a high incidence of tuberculosis

International travel may be a source of introduction of tuberculosis into low-incidence countries. We assessed whether, in The Netherlands, sensitivity to tuberculin was associated with a history of travel to countries with a high incidence of tuberculosis. Immunocompetent adults with no history of Bacille Calmette-Guérin vaccination or sensitivity to tuberculin were skin-tested simultaneously with 1-tuberculin unit (TU) purified protein derivative (PPD) of Mycobacterium tuberculosis and 1-TU sensitin of Mycobacterium scrofulaceum. Tuberculin sensitivity was defined as a reaction to PPD of > or =10 mm that was > or =3 mm larger than the reaction to M. scrofulaceum sensitin. Tuberculin sensitivity was found in 7 (0.7%) of 1014 participants (95% confidence interval [CI], 0.3%-1.4%); it was independently associated with a cumulative history of >3-months' travel to high-incidence areas (odds ratio, 6.0; 95% CI, 1.2-31.2; P=.016) and increased in association with total duration of travel (P=.02). Travel to high-incidence areas increases the risk of tuberculin sensitivity and, consequently, of latent tuberculous infection. In countries with a low incidence of tuberculosis, cases of infection acquired during travel may account for a substantial proportion of new infections in the resident population.

[Tropical diseases and imported disorders in 1763 patients seen at the Outpatient Clinic for Tropical Diseases, Academic Medical Center, Amsterdam (1996-1997)]

OBJECTIVE

To describe an analysis of the patients seen at the Outpatient Department (OPD) for Tropical Diseases in the Academic Medical Centre, Amsterdam, during 1996 and 1997.

DESIGN

Descriptive cross-sectional study.

METHOD

From our database of OPD-patients the following data were analysed: age, country of birth, travel destination and most frequent complaints at presentation. These were further analysed in relation to travel destination, diagnosis and need of admission.

RESULTS

In 1996 and 1997 1763 patients visited the OPD. Abdominal complaints, fever, general malaise and skin diseases were the main problems. Abdominal complaints were more often acquired in Asia, fever in sub-Saharan Africa and skin problems in South America. General malaise was not related to a specific travel destination. Abdominal complaints, fever and general malaise were more often caused by parasites, and skin problems by bacteria. Plasmodia were the most frequently encountered microbial cause. Malaria was found in 1 out of every 3 Dutch, and 9 out of every 10 Ghanaian patients with fever from Africa.

CONCLUSION

The analysis of the database yielded useful information regarding patients with import diseases in the Netherlands and with respect to travellers to tropical areas.

Risk of infection with Mycobacterium tuberculosis in travellers to areas of high tuberculosis endemicity

BACKGROUND

No data exist on risks of infection with Mycobacterium tuberculosis in travellers. We studied incidences of and risk factors for tuberculin skin-test conversion among Dutch long-term travellers to countries of high tuberculosis endemicity.

METHODS

In a multicentre, prospective cohort study based in travel and tuberculosis clinics in the Netherlands, 1072 BCG-naive immunocompetent travellers to countries with an estimated annual risk of M. tuberculosis infection of at least 1% were skin tested before departure with 1 tuberculin unit purified protein derivative (PPD) of M. tuberculosis in Tween-80. Those with results less than 2 mm were retested 2-4 months after their return with simultaneous testing for cross-sensitivity to environmental mycobacteria (1 tuberculin unit PPD of M. scrofulaceum in Tween-80). M. tuberculosis infection was defined as a post-travel M. tuberculosis tuberculin skin-test result of at least 10 mm that was 3 mm or more larger than the M. scrofulaceum result.

FINDINGS

Post-travel skin-test results were available for 656 (66%) of 988 individuals who were eligible for follow-up. Among these, 12 M. tuberculosis infections were identified (1.8%). The overall incidence rate was 3.5 per 1000 person-months of travel (95% CI 2.0-6.2), and 2.8 per 1000 person-months of travel (1.2-5.5) after exclusion of health-care workers. Two had active tuberculosis at the time of testing (incidence rate 0.6 per 1000 person-months of travel [0.3-2.3]). Work in patient care abroad was an independent risk factor (adjusted rate ratio 5.34, p=0.015).

INTERPRETATION

The risk of M. tuberculosis infection in long-term travellers to high-endemicity countries, even if not engaged in health-care work, is substantial and of similar magnitude to the average risk for the local population. BCG vaccination or post-travel tuberculin skin-testing of high-risk travellers should be considered.

Typhoid fever in group travelers: opportunity for studying vaccine efficacy

BACKGROUND

Typhoid fever (TF) is a rare disease among travelers to endemic areas, and little is known about its travel-related epidemiology. In addition, efficacy data on TF vaccines in travelers is scanty. During 3 months of 1994/95, six cases of TF were reported in The Netherlands among participants of four package tours to Indonesia provided by the same operator. The present study was designed to describe the epidemiology of TF in these groups, and to assess whether travel groups can be used for studying the efficacy of TF vaccines in travelers.

METHOD

Questionnaire-based historical cohort study of participants of 4 groups that stayed in the same hotels along their tours (n=156). TF was defined as blood culture-confirmed Salmonella typhi infection. Submitted isolates were typed by antigen and phage typing. Immunization status was considered documented if ascertained by written records.

RESULTS

Among 110 participants (71%), six cases of TF were identified (group specific attack rate AR 5.4%), three of which were from one travel group (AR 12.0%). There were no significant differences by age or sex. Three submitted S. typhi isolates showed three different types, two of which were in the same group. Eighty-three percent of respondents reported documented TF vaccination in the preceding 3 years. All cases occurred in recipients of the oral Ty21a vaccine (AR 10.2%, 95% CI 3.8-20.8%), but differences with nonvaccinees and recipients of the heat-inactivated whole cell or Vi-antigen polysaccharide vaccines were not significant.

CONCLUSIONS

Although TF is rare in travelers, infections with different strains of S. typhi can occur in one travel group. Travel groups offer an opportunity for retrospective assessment of vaccine efficacy, provided that equal chance of exposure is largely guaranteed; case ascertainment is maximally specific and similar in the vaccine groups; vaccine status is ascertained accurately; and prior immunity by previous exposures to and use of antibiotics effective against the infection are excluded from, or controlled for in, the analysis.

Common health problems in HIV-infected travelers to the (sub)tropics

BACKGROUND

A study was conducted to estimate the incidence of health problems in HIV-infected travelers with various degrees of immunodeficiency to the (sub)tropics.

METHODS

A retrospective questionnaire-based study among HIV-infected patients attending the outpatient department of a university hospital during three months in 1996 with a history of travel to (sub)tropical destinations in the proceeding 12 months. The outcome measures were incidences of and medical consultation rates for common travel-associated illnesses.

RESULTS

Of 293 HIV-infected patients, 59 (20%) had traveled during the preceding 12 months; of these 36 (61%) responded. Ten (28%) had traveled more than once during this period. There were no significant differences between travelers and nontravelers regarding CD4 count and age. Fifteen respondents (42%) used cotrimoxazole (CTX) for PCP prophylaxis; 22 (61%) had sought pretravel health advice. Median duration of travel was 3 weeks. Respiratory infections were recorded by two respondents (6%, 95% confidence intervals 1-19%) and skin problems by 10 (28%, 14-45%). Of 31 respondents without diarrhea on departure, 10 recorded diarrhea (32%, 19-57%). The overall rate of medical consultation for travel-related complaints ws 5% abroad and 28% after return, respectively. There was no association between the risk of diarrhea and CD4 count or CTX prophylaxis, even after adjustment for differences in age, duration of travel and travel experience.

CONCLUSIONS

Although numbers in this study are small, HIV-infected travelers tend to have a high rate of medical consultation for (possibly) travel-related illness. Diarrhea is the most frequent complaint, but shows no strong association with degree of immunodeficiency.

[Specificity of the Mantoux-reaction to the new tuberculin RT23 in relation to that of previously used PPD-RIVM; a comparative study in hospital staff]

OBJECTIVE

In the Netherlands, an increase in prevalence of tuberculin positivity has been noted since the replacement of the Dutch PPD-RIVM preparation by RT23. This investigation was carried out to assess the specificity of RT23 compared with PPD-RIVM.

DESIGN

Comparative.

METHOD

In 90 hospital workers simultaneous tuberculin tests were performed in both forearms with RT23 (Statens Serum Institut, Copenhagen, Denmark; lot number 13751; 2 tuberculin units) and PPD-RIVM (Rijksinstituut voor Volksgezondheid en Milieu, Bilthoven, the Netherlands; lot number 76B; 1 IU), respectively. Sensitivity to atypical mycobacteria (Mycobacterium scrophulaceum, M. avium and M. kansasii) was assessed where differences were > 3 mm.

RESULTS

In two of 73 non-vaccinated subjects, reactions to RT23 were 11 and 15 mm larger than to PPD-RIVM; both showed sensitivity to M. scrophulaceum and M. avium. Five of nine BCG vaccinated subjects showed differences of five to eight mm; in four of these, the reaction to RT23 was larger. Repeat testing in one showed no cross-reactions. The specificity of RT23 compared with PPD-RIVM was 96% (cut-off at 10 mm diameter).

CONCLUSIONS

In a low tuberculosis risk population, tuberculin testing with RT23 yields more positive results than PPD-RIVM. This is probably due to stronger cross-reactivity with atypical mycobacteria of RT23. Decisions on isoniazide prophylaxis should take into account an increased false-positivity rate with RT23.

Travel-related morbidity in travelers with insulin-dependent diabetes mellitus

BACKGROUND

To assess whether there are clinically significant problems in patients with insulin-dependent diabetes mellitus (IDDM) traveling to tropical countries regarding metabolic dysregulations, infectious complications and general health problems.

METHODS

A retrospective, descriptive cohort study by telephone interview of all IDDM patients who had received pretravel health advice at our travel clinic during a 12 month period. Data were collected on IDDM related problems: hypo-/hyperglycemic dysregulation, infectious complications, practical difficulties, exploring risk factors, as well as on general health problems.

RESULTS

Of the 19 respondents, 13 (68%) reported any metabolic dysregulation, including all but one respondents with Type 1 diabetes. Fifty-five percent of Type 1 diabetics reported to have dysregulated more often than in the preceding period at home. Critical dysregulations occurred in 2 of the 19 study patients. Only 4 out of 11 (36%) type 1 IDDM patients increased frequency of blood glucose monitoring while traveling. Three travelers reported a febrile illness which resulted in hyperglycemic dysregulation. Five study patients experienced difficulties in the adjustment of their insulin dosage to the unfamiliar circumstances of traveling in the tropics.

CONCLUSIONS

Metabolic dysregulation was a clinically significant problem, thus IDDM travelers to tropical destinations probably run extra health risks. Fever, easily acquired in the tropics, appeared to be an additional, serious health problem for this study population. As the number of diabetic travelers will increase, more research on the importance of risk factors possibly leading to dysregulation is necessary.

Incidence and risk factors of diarrhoea in Dutch travellers: consequences for priorities in pre-travel health advice

A cohort of 743 Dutch short-term travellers (1-6 weeks) to various (sub)tropical areas was studied to assess incidences of travellers' diarrhoea (TD) and risk factors to guide prevention policies. The occurrence of TD was ascertained retrospectively by questionnaire; independent risk factors were identified by logistic regression analysis. The overall attack rate (AR, 95% CI) of TD was 52% (49-56); 11% (9-14) reported two or more episodes. The overall incidence rate (IR) per 100 person weeks of travel (pwt) (95% CI) was 22 (20-24). IRs were highest for travellers to the Middle East (48, 33-71), lowest for South-east Asia (17, 15-20) and East Africa (18, 14-24) and intermediate for South America and West Africa (both 26, 19-36), Central America (29, 23-37) and the Indian subcontinent (32, 26-39). Compared to first episodes of TD, subsequent episodes were of longer duration and more frequently accompanied by faecal blood loss, abdominal cramps or systemic symptoms. After adjustment for travel duration and destination, independent risk factors (OR, 95% CI) for TD were recent treatment for gastrointestinal (GI) disorders (4.6, 1.2-17.2), history of GI surgery (3.9, 1.4-11.1) and, possibly, current use of medication reducing gastric acidity (6.9, 0.7-67.4). The risk was reduced for extensive travel experience (0.4, 0.3-0.7) and organized travel (0.7, 0.5-0.9). Regarding prevention and/or antibiotic self-treatment of TD, priority should be given to travellers who may suffer major health or other consequences from TD and to those with pre-existing GI disorders, particularly when visiting a high or intermediate-risk area on individual journeys with limited travel experience.

Testing for anti-circumsporozoite and anti-blood-stage antibodies for epidemiologic assessment of Plasmodium falciparum infection in travelers

The purpose of this investigation was to assess the role of serology for establishing incidences of Plasmodium falciparum malaria and of exposure to P. falciparum in epidemiologic studies of travelers using chemoprophylaxis. The design was a prospective cohort study involving 548 short-term Dutch travelers to areas endemic for P. falciparum malaria. Sera were collected before departure and, together with the medical history, 2-6 weeks after return. All sera were tested for anti-circumsporozoite (CS) antibodies by an R32tet32-ELISA; sera of subjects reporting febrile illness during travel or after return or with anti-CS responses were tested for anti-blood-stage antibodies by an indirect fluorescence antibody test (IFAT). Five subjects (0.9%) reported P. falciparum malaria confirmed by thick blood smear examination (documented cases) and six (1.0%) reported treatment for malaria without a documented diagnosis (presumptive cases). Conversions in the IFAT were detected in six subjects, including all five documented cases and one presumptive case. Anti-CS antibodies were detected in seven subjects (1.3%), including three documented cases and four of 442 subjects with no history of fever or malaria treatment (0.9%). Incidence rates per 1,000 person-months of travel (95% confidence interval) of infection with P. falciparum, whether or not suppressed by chemoprophylaxis, were 16.9 (8-31) for all destinations and 91.6 (33-200) for West Africa. In epidemiologic studies of P. falciparum malaria in travelers, testing for antibodies to blood stages can increase the sensitivity and specificity of case detection; testing for antibodies to sporozoites may be useful for the assessment of exposure to P. falciparum in travelers using chemoprophylaxis, but the sensitivity is limited.

Compliance with malaria chemoprophylaxis and preventative measures against mosquito bites among Dutch travellers

Self-reported compliance with a malaria chemoprophylaxis regimen of proguanil (PG) plus chloroquine (CQ) was assessed in a cohort of 547 Dutch travellers who visited a single travel clinic when travelling to various areas endemic for falciparum malaria. 503 (92%) had taken PG/CQ prophylaxis, but only 326 (60%) reported regular and uninterrupted use throughout the journey and 4 weeks afterwards. Compliance differed by travel destination and was 45% in South America, 52% in West Africa, 53% in South-east Asia, 60% in the Indian Subcontinent and 78% in East Africa. Parasitologically confirmed falciparum malaria occurred in 5 travellers (0.9%), including 3 of 24 non-compliant travellers to West Africa (12.5%). Apart from destination, independent risk factors for non-compliance were young age, extensive travel experience and adventurous travel. Compliance with protection against mosquito bites was 80% for wearing long-sleeved shirts and long-legged trousers after sunset, 73% for use of repellents, 56% for sleeping under bed nets and 37% for keeping the sleeping quarters free of mosquitoes. Although 440 travellers (80%) reported to have taken two or more of these measures at least once, only 88 (16%) had done so on a daily basis. Daily use of bed nets was reported more frequently among subjects who were non-compliant with chemoprophylaxis. Compliance regarding malaria chemoprophylaxis should be improved, particularly in high-risk areas such as Sub-saharan Africa, with extra attention to young, adventurous travellers. More emphasis should be placed on prevention of Anopheles bites.