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Assessment of Climate-sensitive Infectious Diseases in the Federated States of Micronesia

Lachlan McIver ; Masahiro Hashizume ; Ho Kim ; Yasushi Honda ; Moses Pretrick ; Steven Iddings ; Boris Pavlin

Tropical Medicine and Health.2015;43(1):29-40. doi:10.2149/tmh.2014-17

Background: The health impacts of climate change are an issue of growing concern in the Pacific region. Prior to 2010, no formal, structured, evidence-based approach had been used to identify the most significant health risks posed by climate change in Pacific island countries. During 2010 and 2011, the World Health Organization supported the Federated States of Micronesia (FSM) in performing a climate change and health vulnerability and adaptation assessment. This paper summarizes the priority climate-sensitive health risks in FSM, with a focus on diarrheal disease, its link with climatic variables and the implications of climate change. Methods: The vulnerability and adaptation assessment process included a review of the literature, extensive stakeholder consultations, ranking of climate-sensitive health risks, and analysis of the available long-term data on climate and climate-sensitive infectious diseases in FSM, which involved examination of health information data from the four state hospitals in FSM between 2000 and 2010; along with each state’s rainfall, temperature and El Niño-Southern Oscillation data. Generalized linear Poisson regression models were used to demonstrate associations between monthly climate variables and cases of climate-sensitive diseases at differing temporal lags. Results: Infectious diseases were among the highest priority climate-sensitive health risks identified in FSM, particularly diarrheal diseases, vector-borne diseases and leptospirosis. Correlation with climate data demonstrated significant associations between monthly maximum temperature and monthly outpatient cases of diarrheal disease in Pohnpei and Kosrae at a lag of one month and 0 to 3 months, respectively; no such associations were observed in Chuuk or Yap. Significant correlations between disease incidence and El Niño-Southern Oscillation cycles were demonstrated in Kosrae state. Conclusions: Analysis of the available data demonstrated significant associations between climate variables and climate-sensitive infectious diseases. This information should prove useful in implementing health system and community adaptation strategies to avoid the most serious impacts of climate change on health in FSM.

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The Role of Carbohydrates in Infection Strategies of Enteric Pathogens

Kentaro Kato ; Akiko Ishiwa

Tropical Medicine and Health.2015;43(1):41-52. doi:10.2149/tmh.2014-25

Enteric pathogens cause considerable public health concerns worldwide including tropical regions. Here, we review the roles of carbohydrates in the infection strategies of various enteric pathogens including viruses, bacteria and protozoa, which infect the epithelial lining of the human and animal intestine. At host cell entry, enteric viruses, including norovirus, recognize mainly histo-blood group antigens. At the initial step of bacterial infections, carbohydrates also function as receptors for attachment. Here, we describe the function of carbohydrates in infection by Salmonella enterica and several bacterial species that produce a variety of fimbrial adhesions. During invasion by enteropathogenic protozoa, apicomplexan parasites utilize sialic acids or sulfated glycans. Carbohydrates serve as receptors for infection by these microbes; however, their usage of carbohydrates varies depending on the microbe. On the surface of the mucosal tissues of the gastrointestinal tract, various carbohydrate moieties are present and play a crucial role in infection, representing the site of infection or route of access for most microbes. During the infection and/or invasion process of the microbes, carbohydrates function as receptors for various microbes, but they can also function as a barrier to infection. One approach to develop effective prophylactic and therapeutic antimicrobial agents is to modify the drug structure. Another approach is to modify the mode of inhibition of infection depending on the individual pathogen by using and mimicking the interactions with carbohydrates. In addition, similarities in mode of infection may also be utilized. Our findings will be useful in the development of new drugs for the treatment of enteric pathogens.

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Survey of Wild Mammal Hosts of Cutaneous Leishmaniasis Parasites in Panamá and Costa Rica

Kadir González ; José E. Calzada ; Azael Saldaña ; Chystrie A. Rigg ; Gilbert Alvarado ; Bernal Rodríguez-Herrera ; Uriel D. Kitron ; Gregory H. Adler ; Nicole L. Gottdenker ; Luis Fernando Chaves ; Mario Baldi

Tropical Medicine and Health.2015;43(1):75-78. doi:10.2149/tmh.2014-30

The eco-epidemiology of American cutaneous leishmaniasis (ACL) is driven by animal reservoir species that are a source of infection for sand flies that serve as vectors infecting humans with Leishmania spp parasites. The emergence and re-emergence of this disease across Latin America calls for further studies to identify reservoir species associated with enzootic transmission. Here, we present results from a survey of 52 individuals from 13 wild mammal species at endemic sites in Costa Rica and Panama where ACL mammal hosts have not been previously studied. For Leishmania spp. diagnostics we employed a novel PCR technique using blood samples collected on filter paper. We only found Leishmania spp parasites in one host, the two-toed sloth, Choloepus hoffmanni. Our findings add further support to the role of two-toed sloths as an important ACL reservoir in Central America.

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A Systematic Review of Methodology: Time Series Regression Analysis for Environmental Factors and Infectious Diseases

Chisato Imai ; Masahiro Hashizume

Tropical Medicine and Health.2015;43(1):1-9. doi:10.2149/tmh.2014-21

Background: Time series analysis is suitable for investigations of relatively direct and short-term effects of exposures on outcomes. In environmental epidemiology studies, this method has been one of the standard approaches to assess impacts of environmental factors on acute non-infectious diseases (e.g. cardiovascular deaths), with conventionally generalized linear or additive models (GLM and GAM). However, the same analysis practices are often observed with infectious diseases despite of the substantial differences from non-infectious diseases that may result in analytical challenges. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, systematic review was conducted to elucidate important issues in assessing the associations between environmental factors and infectious diseases using time series analysis with GLM and GAM. Published studies on the associations between weather factors and malaria, cholera, dengue, and influenza were targeted. Findings: Our review raised issues regarding the estimation of susceptible population and exposure lag times, the adequacy of seasonal adjustments, the presence of strong autocorrelations, and the lack of a smaller observation time unit of outcomes (i.e. daily data). These concerns may be attributable to features specific to infectious diseases, such as transmission among individuals and complicated causal mechanisms. Conclusion: The consequence of not taking adequate measures to address these issues is distortion of the appropriate risk quantifications of exposures factors. Future studies should pay careful attention to details and examine alternative models or methods that improve studies using time series regression analysis for environmental determinants of infectious diseases.

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Visualization of Malaria Parasites in the Skin Using the Luciferase Transgenic Parasite, Plasmodium berghei

Hiroyuki Matsuoka ; Hiroyuki Tomita ; Ryuta Hattori ; Meiji Arai ; Makoto Hirai

Tropical Medicine and Health.2015;43(1):53-61. doi:10.2149/tmh.2014-18

We produced a transgenic rodent malaria parasite (Plasmodium berghei) that contained the luciferase gene under a promoter region of elongation factor-1α. These transgenic (TG) parasites expressed luciferase in all stages of their life cycle, as previously reported. However, we were the first to succeed in observing sporozoites as a mass in mouse skin following their deposition by the probing of infective mosquitoes. Our transgenic parasites may have emitted stronger bioluminescence than previous TG parasites. The estimated number of injected sporozoites by mosquitoes was between 34 and 775 (median 80). Since luciferase activity diminished immediately after the death of the parasites, luciferase activity could be an indicator of the existence of live parasites. Our results indicated that sporozoites survived at the probed site for more than 42 hours. We also detected sporozoites in the liver within 15 min of the intravenous injection. Bioluminescence was not observed in the lung, kidney or spleen. We confirmed the observation that the liver was the first organ in which malaria parasites entered and increased in number.

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A Prospective Hospital-based Surveillance to Estimate Rotavirus Disease Burden in Bhutanese Children under 5 Years of Age

Sonam Wangchuk ; Tshering Dorji ; Tsheten ; Karchung Tshering ; Sangay Zangmo ; Kunzang Pem Tshering ; Tandin Dorji ; Akira Nishizono ; Kamruddin Ahmed

Tropical Medicine and Health.2015;43(1):63-68. doi:10.2149/tmh.2014-22

As part of efforts to develop an informed policy for rotavirus vaccination, this prospective study was conducted to estimate the burden of rotavirus diarrhea among children less than 5 years old attended to the Department of Pediatrics, Jigme Dorji Wangchuk National Referral Hospital (JDWNRH), Thimphu, Bhutan. The duration of the study was three years, extending from February 2010 through December 2012. We estimated the frequency of hospitalization in the pediatric ward and dehydration treatment unit (DTU) for diarrhea and the number of events attributable to rotavirus infection among children under 5 years of age. During the study period, a total of 284 children (1 in 45) were hospitalized in the pediatric ward, and 2,220 (1 in 6) in the DTU with diarrhea among children residing in the Thimphu district. Group A rotavirus was detected in 32.5% and 18.8% of the stool samples from children hospitalized in the pediatric ward, respectively. Overall, 22.3% of the stool samples were rotavirus-positive, and the majority (90.8%) of them was detected in children under 2 years of age. From this study, we estimated that the annual incidence of hospitalization in the pediatric ward and DTU due to rotavirus diarrhea was 2.4/1000 (95% CI 1.7–3.4) and 10.8/1000 (95% CI 9.1–12.7) children, respectively. This study revealed that rotavirus is a major cause of diarrhea in Bhutanese children in Thimphu district and since no study has been performed previously, represents an important finding for policy discussions regarding the adoption of a rotavirus vaccine in Bhutan.

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Dengue Hemorrhagic Fever in a Japanese Traveler with Pre-existing Japanese Encephalitis Virus Antibody

Rumi Sato ; Nobuyuki Hamada ; Takahito Kashiwagi ; Yoshihiro Imamura ; Koyu Hara ; Munetsugu Nishimura ; Tomoko Kamimura ; Tomohiko Takasaki ; Hiroshi Watanabe ; Takeharu Koga

Tropical Medicine and Health.2015;43(2):85-88. doi:10.2149/tmh.2014-34

An adult Japanese man who had just returned from Thailand developed dengue hemorrhagic fever (DHF). A primary infection of dengue virus (DENV) was confirmed, specifically DENV serotype 2 (DENV-2), on the basis of the detection of the virus genome, a significant increase in the neutralizing antibody and the isolation of DENV-2. DHF is often observed following a secondary infection from another serotype of dengue virus, particularly in children, but this case was a primary infection of DENV. Japan is a non-endemic country for dengue disease. In fact, only Japanese encephalitis (JE) is known to be a member of the endemic flavivirus family. In this study, IgG antibody against Japanese encephalitis virus (JEV) was detected. JEV belongs to the family of dengue virus and prevails in Japan, particularly Kyushu. Among many risk factors for the occurrence of DHF, a plausible candidate could be a cross-reactive antibody-dependent enhancement (ADE) mechanism caused by JEV antibody. This indicates that most Japanese travelers who living in dengue non-endemic areas, particularly Kyushu, should be aware of the occurrence of DHF.

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Households with Insufficient Bednets in a Village with Sufficient Bednets: Evaluation of Household Bednet Coverage Using Bednet Distribution Index in Xepon District, Lao PDR

Daisuke Nonaka ; Tiengkham Pongvongsa ; Futoshi Nishimoto ; Phetsomphon Nansounthavong ; Yu Sato ; Hongwei Jiang ; Rie Takeuchi ; Kazuhiko Moji ; Panom Phongmany ; Jun Kobayashi

Tropical Medicine and Health.2015;43(2):95-110. doi:10.2149/tmh.2014-37

In Lao PDR, the National Malaria Control Program (NMCP) evaluates bednet coverage, often at the village level, using a coverage target of one net per 2.5 (or fewer) persons in a given population. However, in villages that meet the target, not all households necessarily meet the target or utilize all available bednets. This study explored households that fell short of the target and household utilization of bednets in villages that met the target of bednet coverage set by the NMCP. The person per net ratio (PPNR), which is defined as the population divided by the number of available bednets in a household/village, was used to determine whether a household/village met the NMCP target. Using a household survey, we collected and analyzed the data of 635 households in 17 villages in Xepon district in 2012. Households that fell short of the target (households with a PPNR of > 2.5 or no bednet) existed in every village. The proportion of these households differed greatly among the villages, ranging from 3.4–50%, with some households falling far short. Of the 635 households, 275 (43.5%) had at least one bednet that was not being used on the night preceding the survey and 131 (20.6%) had at least two. In conclusion, in villages that met the NMCP target, a considerable number of households fell short of the target, and the available bednets were not fully utilized in many of the surveyed households.

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Author’s Response to Burgess

Hermann Feldmeier

Tropical Medicine and Health.2015;43(2):91-92. doi:10.2149/tmh.2014-39_res

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Re: Treatment of Parasitic Skin Diseases with Dimeticones A New Family of Compounds with a Purely Physical Mode of Action

Ian F. Burgess

Tropical Medicine and Health.2015;43(2):89-90. doi:10.2149/tmh.2014-39

The article on use of dimeticone for treatment of epidermal parasitic skin diseases is potentially confusing and misleading because, in a practical sense, only head louse infestation can be treated with this material. Scabies mites are unaffected by silicones and use of dimeticone against other ectoparasites may have unwanted side effects such as anaphylactiform reactions or increased risk of pathogen transmission.

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