Temporal and Spatial Differences between Symptomatic and Asymptomatic Malaria Infections in the Chittagong Hill Districts, Bangladesh.

Mapping asymptomatic malaria infections, which contribute to the transmission reservoir, is important for elimination programs. This analysis compared the spatiotemporal patterns of symptomatic and asymptomatic Plasmodium falciparum malaria infections in a cohort study of ∼25,000 people living in a rural hypoendemic area of about 179 km2 in a small area of the Chittagong Hill Districts of Bangladesh. Asymptomatic infections were identified by active surveillance; symptomatic clinical cases presented for care. Infections were identified by a positive rapid diagnostic test and/or microscopy. Fifty-three subjects with asymptomatic P. falciparum infection were compared with 572 subjects with symptomatic P. falciparum between mid-October 2009 and mid-October 2012 with regard to seasonality, household location, and extent of spatial clustering. We found increased spatial clustering of symptomatic compared with asymptomatic infections, and the areas of high intensity were only sometimes overlapping. Symptomatic cases had a distinct seasonality, unlike asymptomatic infections, which were detected year-round. In a comparison of 42 symptomatic Plasmodium vivax and 777 symptomatic P. falciparum cases from mid-October 2009 through mid-March 2015, we found substantial spatial overlap in areas with high infection rates, but the areas with the greatest concentration of infection differed. Detection of both symptomatic P. falciparum and symptomatic P. vivax infections was greater during the May-to-October high season, although a greater proportion of P. falciparum cases occurred during the high season compared with P. vivax. These findings reinforce that passive malaria surveillance and treatment of symptomatic cases will not eliminate the asymptomatic reservoirs that occur distinctly in time and space.

Usability of Rapid Cholera Detection Device (OmniVis) for Water Quality Workers in Bangladesh: Iterative Convergent Mixed Methods Study.

BACKGROUND: Cholera poses a significant global health burden. In Bangladesh, cholera is endemic and causes more than 100,000 cases each year. Established environmental reservoirs leave millions at risk of infection through the consumption of contaminated water. The Global Task Force for Cholera Control has called for increased environmental surveillance to detect contaminated water sources prior to human infection in an effort to reduce cases and deaths. The OmniVis rapid cholera detection device uses loop-mediated isothermal amplification and particle diffusometry detection methods integrated into a handheld hardware device that attaches to an iPhone 6 to identify and map contaminated water sources. OBJECTIVE: The aim of this study was to evaluate the usability of the OmniVis device with targeted end users to advance the iterative prototyping process and ultimately design a device that easily integrates into users' workflow. METHODS: Water quality workers were trained to use the device and subsequently completed an independent device trial and usability questionnaire. Pretraining and posttraining knowledge assessments were administered to ensure training quality did not confound trial and questionnaire. RESULTS: Device trials identified common user errors and device malfunctions including incorrect test kit insertion and device powering issues. We did not observe meaningful differences in user errors or device malfunctions accumulated per participant across demographic groups. Over 25 trials, the mean time to complete a test was 47 minutes, a significant reduction compared with laboratory protocols, which take approximately 3 days. Overall, participants found the device easy to use and expressed confidence and comfort in using the device independently. CONCLUSIONS: These results are used to advance the iterative prototyping process of the OmniVis rapid cholera detection device so it can achieve user uptake, workflow integration, and scale to ultimately impact cholera control and elimination strategies. We hope this methodology will promote robust usability evaluations of rapid pathogen detection technologies in device development.

Community-based antibiotic access and use in six low-income and middle-income countries: a mixed-method approach.

BACKGROUND: Antimicrobial misuse is common in low-income and middle-income countries (LMICs), and this practice is a driver of antibiotic resistance. We compared community-based antibiotic access and use practices across communities in LMICs to identify contextually specific targets for interventions to improve antibiotic use practices. METHODS: We did quantitative and qualitative assessments of antibiotic access and use in six LMICs across Africa (Mozambique, Ghana, and South Africa) and Asia (Bangladesh, Vietnam, and Thailand) over a 2·5-year study period (July 1, 2016-Dec 31, 2018). We did quantitative assessments of community antibiotic access and use through supplier mapping, customer exit interviews, and household surveys. These quantitative assessments were triangulated with qualitative drug supplier and consumer interviews and discussions. FINDINGS: Vietnam and Bangladesh had the largest proportions of non-licensed antibiotic dispensing points. For mild illness, drug stores were the most common point of contact when seeking antibiotics in most countries, except South Africa and Mozambique, where public facilities were most common. Self-medication with antibiotics was found to be widespread in Vietnam (55·2% of antibiotics dispensed without prescription), Bangladesh (45·7%), and Ghana (36·1%), but less so in Mozambique (8·0%), South Africa (1·2%), and Thailand (3·9%). Self-medication was considered to be less time consuming, cheaper, and overall, more convenient than accessing them through health-care facilities. Factors determining where treatment was sought often involved relevant policies, trust in the supplier and the drug, disease severity, and whether the antibiotic was intended for a child. Confusion regarding how to identify oral antibiotics was revealed in both Africa and Asia. INTERPRETATION: Contextual complexities and differences between countries with different incomes, policy frameworks, and cultural norms were revealed. These contextual differences render a single strategy inadequate and instead necessitate context-tailored, integrated intervention packages to improve antibiotic use in LMICs as part of global efforts to combat antibiotic resistance. FUNDING: Wellcome Trust and Volkswagen Foundation.

A five-day course of ivermectin for the treatment of COVID-19 may reduce the duration of illness.

Ivermectin, a US Food and Drug Administration-approved anti-parasitic agent, was found to inhibit severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) replication in vitro. A randomized, double-blind, placebo-controlled trial was conducted to determine the rapidity of viral clearance and safety of ivermectin among adult SARS-CoV-2 patients. The trial included 72 hospitalized patients in Dhaka, Bangladesh, who were assigned to one of three groups: oral ivermectin alone (12 mg once daily for 5 days), oral ivermectin in combination with doxycycline (12 mg ivermectin single dose and 200 mg doxycycline on day 1, followed by 100 mg every 12 h for the next 4 days), and a placebo control group. Clinical symptoms of fever, cough, and sore throat were comparable among the three groups. Virological clearance was earlier in the 5-day ivermectin treatment arm when compared to the placebo group (9.7 days vs 12.7 days; p = 0.02), but this was not the case for the ivermectin + doxycycline arm (11.5 days; p = 0.27). There were no severe adverse drug events recorded in the study. A 5-day course of ivermectin was found to be safe and effective in treating adult patients with mild COVID-19. Larger trials will be needed to confirm these preliminary findings.

What influences antibiotic sales in rural Bangladesh? A drug dispensers' perspective.

BACKGROUND: Antibiotic resistance poses a great threat to global health, especially in low- and middle-income countries with a high infectious disease burden and limited resources. In spite of regulations, antibiotics are sold in many settings as non-prescription medicines, resulting in inappropriate use and resistance. OBJECTIVE: This study aimed to investigate the current status of access and use of antibiotics in rural Bangladesh, by exploring the perspectives and sales practices of antibiotic drug dispensers. METHODS: We used a mixed methods approach (qualitative and quantitative). We mapped and characterized antibiotic purchasing and dispensing sites in the Matlab Health and Demographic Surveillance System catchment area. Furthermore, we investigated the volume of provision of systemic antibiotics in 10 drug outlets. We held 16 in-depth interviews with randomly selected antibiotics dispensers. Interviews explored factors associated with antibiotic selling. Responses were transcribed, coded for themes, and summarized. We used ATLAS.ti 5.2 for conducting a thematic analysis. RESULTS: A total of 301 antibiotic dispensers were identified, of whom 92% (n = 278) were private and 8% (n = 23) public. 52% (n = 155) operated informally (i.e. without legal authorization). In order to promote and survive in their business, dispensers sell antibiotics for a range of conditions without a qualified physician's prescription. Factors that facilitate these inappropriate sales include lack of access to healthcare in the rural community, inadequate doctor: population ratio, limited dispenser knowledge, poor pharmacovigilance concerning safety of self medication, lack of enforcement of policies, financial benefits for both customers and dispensers, and high dependency on pharmaceutical companies' information. CONCLUSION: Dispensers in rural Bangladesh sell antibiotics inappropriately by ignoring existing national regulations. They operate the antibiotic sales without facing any legal barriers and primarily with a view to sustain their business, resulting in inappropriate sales of antibiotics to the rural community. The influence of the drug industry needs to be replaced with evidence-based, not commercially driven information. Awareness programs for antibiotic providers that promote understanding of antibiotics and antibiotic resistance through tailored interventions may be helpful in changing current antibiotic sales practices.

Subclinical Plasmodium falciparum infections act as year-round reservoir for malaria in the hypoendemic Chittagong Hill districts of Bangladesh.

OBJECTIVES: An analysis of the risk factors and seasonal and spatial distribution of individuals with subclinical malaria in hypoendemic Bangladesh was performed. METHODS: From 2009 to 2012, active malaria surveillance without regard to symptoms was conducted on a random sample (n=3971) and pregnant women (n=589) during a cohort malaria study in a population of 24000. RESULTS: The overall subclinical Plasmodium falciparum malaria point prevalence was 1.0% (n=35), but was 3.2% (n=18) for pregnant women. The estimated incidence was 39.9 per 1000 person-years for the overall population. Unlike symptomatic malaria, with a marked seasonal pattern, subclinical infections did not show a seasonal increase during the rainy season. Sixty-nine percent of those with subclinical P. falciparum infections reported symptoms commonly associated with malaria compared to 18% without infection. Males, pregnant women, jhum cultivators, and those living closer to forests and at higher elevations had a higher prevalence of subclinical infection. CONCLUSIONS: Hypoendemic subclinical malaria infections were associated with a number of household and demographic factors, similar to symptomatic cases. Unlike clinical symptomatic malaria, which is highly seasonal, these actively detected infections were present year-round, made up the vast majority of infections at any given time, and likely acted as reservoirs for continued transmission.

Efficacy of Ciprofloxacin for Treatment of Cholera Associated with Diminished Susceptibility to Ciprofloxacin to Vibrio cholerae O1.

OBJECTIVE: We identified a poor clinical response to treatment of cholera with a single 1 g dose of ciprofloxacin, a standard treatment for cholera. METHODS: To determine reasons for the poor response and better therapeutic approaches we examined the minimal inhibitor concentration (MIC, n = 275) and disc-diffusion zone sizes (n = 205) for ciprofloxacin and nalidixic acid of V. cholerae O1 strains isolated in Bangladesh from 1994 to 2012, and reexamined data from 161 patients infected with Vibrio cholerae O1 recruited in four clinical trials who received single- or multiple-dose ciprofloxacin for treatment of cholera and compared their clinical response to the V. cholerae O1 susceptibility. RESULTS: Although all 275 isolates of V. cholerae O1 remained susceptible to ciprofloxacin using standard MIC and disc-diffusion thresholds, the MIC90 to ciprofloxacin increased from 0.010 in 1994 to 0.475 µgm/ml in 2012. Isolates became frankly resistant to nalidixic with the MIC90 increasing from 21 µgm/ml in 1994 to >256 µgm/ml and 166 of 205 isolates from 1994 to 2005 being frankly resistant using disc-diffusion testing. Isolates resistant to nalidixic acid by disc-diffusion testing had a median ciprofloxacin MIC of 0.190 µgm/ml (10th-90th centiles 0.022 to 0.380); nalidixic acid-susceptible isolates had a median ciprofloxacin MIC of 0.002 (0.002 to 0.012).The rate of clinical success with single-dose ciprofloxacin treatment for nalidixic acid-susceptible strains was 94% (61 of 65 patients) and bacteriologic success 97% (63/65) compared to 18% (12/67) and 8% (5/67) respectively with nalidixic acid-resistant strains (P<0.001 for both comparisons). Multiple-dose treatment with ciprofloxacin had 86% and 100% clinical and bacteriologic success rates respectively in patients infected with nalidixic acid-susceptible strains of V. cholerae O1 compared to clinical success 67% and bacteriologic success 60% with nalidixic acid-resistant strains. CONCLUSIONS: Single-dose ciprofloxacin is not effective for treating cholera caused by V. cholerae O1 with diminished susceptibility to ciprofloxacin, and nalidixic acid disc-diffusion testing effectively screens for such isolates.

Hemoglobin E and Glucose-6-Phosphate Dehydrogenase Deficiency and Plasmodium falciparum Malaria in the Chittagong Hill Districts of Bangladesh.

Hemoglobin E is largely confined to south and southeast Asia. The association between hemoglobin E (HbE) and malaria is less clear than that of hemoglobin S and C. As part of a malaria study in the Chittagong Hill Districts of Bangladesh, an initial random sample of 202 individuals showed that 39% and 49% of Marma and Khyang ethnic groups, respectively, were positive for either heterozygous or homozygous hemoglobin E. In this group, 6.4% were also found to be severely deficient and 35% mildly deficient for glucose-6-phosphate dehydrogenase (G6PD). In a separate Plasmodium falciparum malaria case-uninfected control study, the odds of having homozygous hemoglobin E (HbEE) compared with normal hemoglobin (HbAA) were higher among malaria cases detected by passive surveillance than age and location matched uninfected controls (odds ratio [OR] = 5.0, 95% confidence interval [CI] = 1.07-46.93). The odds of heterozygous hemoglobin E (HbAE) compared with HbAA were similar between malaria cases and uninfected controls (OR = 0.71, 95% CI = 0.42-1.19). No association by hemoglobin type was found in the initial parasite density or the proportion parasite negative after 2 days of artemether/lumefantrine treatment. HbEE, but not HbAE status was associated with increased passive case detection of malaria.

The practice of jhum cultivation and its relationship to Plasmodium falciparum infection in the Chittagong Hill Districts of Bangladesh.

Malaria is endemic in the Chittagong Hill Districts of southeastern Bangladesh. Previous epidemiological analyses identified the agricultural practice of jhum cultivation as a potential risk factor for malaria infection. We conducted qualitative interviews with jhum cultivators and surveillance workers to describe jhum cultivation and used demographic and malaria surveillance in two study unions from May of 2010 to August of 2012 to better understand the relationship between jhum cultivation and malaria infection. Qualitative interviews revealed that jhum cultivation is conducted on remote, steep hillsides by ethnic tribal groups. Quantitative analyses found that adult jhum cultivators and individuals who live in the same residence had significantly higher incidence rates of symptomatic Plasmodium falciparum infection compared with non-cultivators. These results confirm that jhum cultivation is an independent risk factor for malaria infection and underscore the need for malaria testing and treatment services to reach remote populations in the Chittagong Hill Districts.

Asymptomatic Plasmodium falciparum malaria in pregnant women in the Chittagong Hill Districts of Bangladesh.

BACKGROUND: Pregnancy is a known risk factor for malaria which is associated with increased maternal and infant mortality and morbidity in areas of moderate-high malaria transmission intensity where Plasmodium falciparum predominates. The nature and impact of malaria, however, is not well understood in pregnant women residing in areas of low, unstable malaria transmission where P. falciparum and P. vivax co-exist. METHODS: A large longitudinal active surveillance study of malaria was conducted in the Chittagong Hill Districts of Bangladesh. Over 32 months in 2010-2013, the period prevalence of asymptomatic P. falciparum infections was assessed by rapid diagnostic test and blood smear and compared among men, non-pregnant women and pregnant women. A subset of samples was tested for infection by PCR. Hemoglobin was assessed. Independent risk factors for malaria infection were determined using a multivariate logistic regression model. RESULTS: Total of 34 asymptomatic P. falciparum infections were detected by RDT/smear from 3,110 tests. The period prevalence of asymptomatic P. falciparum infection in pregnant women was 2.3%, compared to 0.5% in non-pregnant women and 0.9% in men. All RDT/smear positive samples that were tested by PCR were PCR-positive, and PCR detected additional 35 infections that were RDT/smear negative. In a multivariate logistic regression analysis, pregnant women had 5.4-fold higher odds of infection as compared to non-pregnant women. Malaria-positive pregnant women, though asymptomatic, had statistically lower hemoglobin than those without malaria or pregnancy. Asymptomatic malaria was found to be evenly distributed across space and time, in contrast to symptomatic infections which tend to cluster. CONCLUSION: Pregnancy is a risk factor for asymptomatic P. falciparum infection in the Chittagong Hill Districts of Bangladesh, and pregnancy and malaria interact to heighten the effect of each on hemoglobin. The even distribution of asymptomatic malaria, without temporal and spatial clustering, may have critical implications for malaria elimination strategies.

Malaria hotspots drive hypoendemic transmission in the Chittagong Hill Districts of Bangladesh.

BACKGROUND: Malaria is endemic in 13 of 64 districts of Bangladesh, representing a population at risk of about 27 million people. The highest rates of malaria in Bangladesh occur in the Chittagong Hill Districts, and Plasmodium falciparum (predominately chloroquine resistant) is the most prevalent species. METHODS: The objective of this research was to describe the epidemiology of symptomatic P. falciparum malaria in an area of Bangladesh following the introduction of a national malaria control program. We carried out surveillance for symptomatic malaria due to P. falciparum in two demographically defined unions of the Chittagong Hill Districts in Bangladesh, bordering western Myanmar, between October 2009 and May 2012. The association between sociodemographics and temporal and climate factors with symptomatic P. falciparum infection over two years of surveillance data was assessed. Risk factors for infection were determined using a multivariate regression model. RESULTS: 472 cases of symptomatic P. falciparum malaria cases were identified among 23,372 residents during the study period. Greater than 85% of cases occurred during the rainy season from May to October, and cases were highly clustered geographically within these two unions with more than 80% of infections occurring in areas that contain approximately one-third of the total population. Risk factors statistically associated with infection in a multivariate logistic regression model were living in the areas of high incidence, young age, and having an occupation including jhum cultivation and/or daily labor. Use of long lasting insecticide-treated bed nets was high (89.3%), but its use was not associated with decreased incidence of infection. CONCLUSION: Here we show that P. falciparum malaria continues to be hypoendemic in the Chittagong Hill Districts of Bangladesh, is highly seasonal, and is much more common in certain geographically limited hot spots and among certain occupations.

Mobile phones improve case detection and management of malaria in rural Bangladesh.

BACKGROUND: The recent introduction of mobile phones into the rural Bandarban district of Bangladesh provided a resource to improve case detection and treatment of patients with malaria. METHODS: During studies to define the epidemiology of malaria in villages in south-eastern Bangladesh, an area with hypoendemic malaria, the project recorded 986 mobile phone calls from families because of illness suspected to be malaria between June 2010 and June 2012. RESULTS: Based on phone calls, field workers visited the homes with ill persons, and collected blood samples for malaria on 1,046 people. 265 (25%) of the patients tested were positive for malaria. Of the 509 symptomatic malaria cases diagnosed during this study period, 265 (52%) were detected because of an initial mobile phone call. CONCLUSION: Mobile phone technology was found to be an efficient and effective method for rapidly detecting and treating patients with malaria in this remote area. This technology, when combined with local knowledge and field support, may be applicable to other hard-to-reach areas to improve malaria control.

Diversity of anopheline species and their Plasmodium infection status in rural Bandarban, Bangladesh.

BACKGROUND: Historically, the Chittagong Hill Tracts (CHT) of Bangladesh was considered hyperendemic for malaria. To better understand the contemporary malaria epidemiology and to develop new and innovative control strategies, comprehensive epidemiologic studies are ongoing in two endemic unions of Bandarban district of CHT. Within these studies entomological surveillance has been undertaken to study the role of the existing anopheline species involved in the malaria transmission cycle throughout the year. METHODS: CDC miniature light traps were deployed to collect anopheline mosquitoes from the sleeping room of the selected houses each month in a single union (Kuhalong). Molecular identification was carried out for available Anopheles species complexes. Circumsporozoite proteins (CSP) for Plasmodium falciparum, Plasmodium vivax-210 (Pv-210) and Plasmodium vivax-247(Pv-247) were detected by Enzyme-linked immunosorbent assay (ELISA) from the female anopheline mosquitoes. To confirm CSP-ELISA results, polymerase chain reaction (PCR) was also performed. RESULTS: A total of 2,837 anopheline mosquitoes, of which 2,576 were female, belonging to 20 species were collected from July 2009-June 2010. Anopheles jeyporiensis was the most abundant species (18.9%), followed by An. vagus (16.8%) and An. kochi (14.4%). ELISA was performed on 2,467 female mosquitoes of 19 species. 15 (0.6%) female anophelines belonging to eight species were found to be positive for Plasmodium infection by CSP-ELISA. Of those, 11 (0.4%) mosquitoes were positive for P. falciparum and four (0.2%) for Pv-210. No mosquito was found positive for Pv-247. An. maculatus (2.1%, 2/97) had the highest infection rate followed by An. umbrosus (1.7%, 2/115) and An. barbirostris (1.1%, 2/186). Other infected species were An. nigerrimus, An. nivipes, An. jeyporiensis, An. kochi, and An. vagus. Out of 11 P. falciparum CSP positive samples, seven turned out to be positive by PCR. None of the samples positive for Pv-210 was positive by PCR. In terms of abundance and incrimination, the results suggest that An. maculatus, An. jeyporiensis and An. nivipes play important roles in malaria transmission in Kuhalong. CONCLUSION: The findings of this study suggest that even in the presence of an insecticide impregnated bed-net intervention, a number of Anopheles species still play a role in the transmission of malaria. Further investigations are required to reveal the detailed biology and insecticide resistance patterns of the vector mosquito species in endemic areas in Bangladesh in order to assist with the planning and implementation of improved malaria control strategies.

Systemic antibody responses to the immunodominant p23 antigen and p23 polymorphisms in children with cryptosporidiosis in Bangladesh.

Cryptosporidium is a major cause of diarrhea in children in developing countries. However, there is no vaccine available and little is known about immune responses to protective antigens. We investigated antibody responses to p23, a putative vaccine candidate, in children in Bangladesh with cryptosporidiosis and diarrhea (cases) and uninfected children with diarrhea (controls), and p23 gene polymorphisms in infecting species. Serum IgM, IgG, and IgA responses to p23 were significantly greater in cases than controls after three weeks of follow-up. Cases with acute diarrhea had significantly greater serum IgA and IgM responses than those with persistent diarrhea, which suggested an association with protection from prolonged disease. The p23 sequences were relatively conserved among infecting species and subtype families. Although most children were infected with Cryptosporidium hominis, there was a cross-reactive antibody response to C. parvum antigen. These results support further development of p23 as a vaccine candidate.

Serum antibody responses to polymorphic Cryptosporidium mucin antigen in Bangladeshi children with cryptosporidiosis.

Cryptosporidium is a significant cause of diarrheal disease in children in developing countries. The sporozoite antigen Muc4 is important for infection of host cells, and could be a candidate vaccine antigen. However, this antigen is polymorphic between Cryptosporidium hominis and C. parvum. We investigated antibody responses to C. hominis Muc4 and C. parvum Muc4 antigen in children in Bangladesh infected with C. hominis. Antibody responses were compared between children with cryptosporidial diarrhea (cases) and uninfected children with diarrhea (controls). There was a significant IgM response to Muc4 from both species in cases compared with controls, which increased over time, and was higher in children with persistent diarrhea. Despite sequence polymorphisms, antibody responses to C. hominis Muc4 and C. parvum Muc4 were significantly correlated. These results suggest that the human antibody response to Muc4 is cross-reactive between species, but in young children does not mature to an IgG response within the period observed in this study.

Antibody responses to the immunodominant Cryptosporidium gp15 antigen and gp15 polymorphisms in a case-control study of cryptosporidiosis in children in Bangladesh.

Although Cryptospridium hominis is the dominant Cryptosporidium species infecting humans, immune responses to cognate antigens in C. hominis-infected persons have not been reported. We investigated antibody responses to the immunodominant gp15 antigen from C. hominis and C. parvum, in C. hominis-infected Bangladeshi children less than five years of age with diarrhea (cases) and uninfected children with diarrhea (controls). We also investigated polymorphisms in the C. hominis gp15 sequence from cases. Serum IgG responses to gp15 from both species were significantly greater in cases than controls. In spite of polymorphisms in the gp15 sequence, there was a significant correlation between antibody levels to gp15 from both species, indicating cross-reactivity to conserved epitopes. Cases with acute diarrhea had a significantly greater serum IgA response to gp15 compared with those with persistent diarrhea, suggesting that this response may be associated with protection from prolonged disease. These findings support further investigation of gp15 as a vaccine candidate.

Mapping hypoendemic, seasonal malaria in rural Bandarban, Bangladesh: a prospective surveillance.

BACKGROUND: Until recently the Chittagong Hill tracts have been hyperendemic for malaria. A past cross-sectional RDT based survey in 2007 recorded rates of approximately 15%. This study was designed to understand the present epidemiology of malaria in this region, to monitor and facilitate the uptake of malaria intervention activities of the national malaria programme and to serve as an area for developing new and innovative control strategies for malaria. METHODS: This research field area was established in two rural unions of Bandarban District of Bangladesh north of Bandarban city, which are known to be endemic for malaria due to Plasmodium falciparum. The project included the following elements: a) a demographic surveillance system including an initial census with updates every four months, b) periodic surveys of knowledge attitude and practice, c) a geographic information system, d) weekly active and continuous passive surveillance for malaria infections using smears, rapid tests and PCR, f) monthly mosquito surveillance, and e) daily weather measures. The programme included both traditional and molecular methods for detecting malaria as well as lab methods for speciating mosquitoes and detecting mosquitoes infected with sporozoites. RESULTS: The demographic surveillance enumerated and mapped 20,563 people, 75% of which were tribal non-Bengali. The monthly mosquito surveys identified 22 Anopheles species, eight of which were positive by circumsporozoite ELISA. The annual rate of malaria was close to 1% with 85% of cases in the rainy months of May-October. Definitive clustering identified in the low transmission season persisted during the high transmission season. CONCLUSION: This demographically and geographically defined area, near to the Myanmar border, which is also hypoendemic for malaria, will be useful for future studies of the epidemiology of malaria and for evaluation of strategies for malaria control including new drugs and vaccines.

Genetic diversity of Cryptosporidium spp. from Bangladeshi children.

The genetic diversity of Cryptosporidium spp. from infected children was characterized for the first time in Bangladesh. Seven C. hominis and C. parvum subtype families (including a new family, IIm) and 15 subtypes (including 2 new subtypes) were identified. The dominance of specific families and subtypes was different from that in other countries.

Transferable quinolone resistance in Vibrio cholerae.

Ciprofloxacin was introduced for treatment of patients with cholera in Bangladesh because of resistance to other agents, but its utility has been compromised by the decreasing ciprofloxacin susceptibility of Vibrio cholerae over time. We correlated levels of susceptibility and temporal patterns with the occurrence of mutation in gyrA, which encodes a subunit of DNA gyrase, followed by mutation in parC, which encodes a subunit of DNA topoisomerase IV. We found that ciprofloxacin activity was more recently further compromised in strains containing qnrVC3, which encodes a pentapeptide repeat protein of the Qnr subfamily, members of which protect topoisomerases from quinolone action. We show that qnrVC3 confers transferable low-level quinolone resistance and is present within a member of the SXT integrating conjugative element family found commonly on the chromosomes of multidrug-resistant strains of V. cholerae and on the chromosomes of Escherichia coli transconjugants constructed in the laboratory. Thus, progressive increases in quinolone resistance in V. cholerae are linked to cumulative mutations in quinolone targets and most recently to a qnr gene on a mobile multidrug resistance element, resulting in further challenges for the antimicrobial therapy of cholera.