Mark Polhemus

A global map of suitability for coastal Vibrio cholerae under current and future climate conditions.

Vibrio cholerae is a globally distributed water-borne pathogen that causes severe diarrheal disease and mortality, with current outbreaks as part of the seventh pandemic. Further understanding of the role of environmental factors in potential pathogen distribution and corresponding V. cholerae disease transmission over time and space is urgently needed to target surveillance of cholera and other climate and water-sensitive diseases. We used an ecological niche model (ENM) to identify environmental variables associated with V. cholerae presence in marine environments, to project a global model of V. cholerae distribution in ocean waters under current and future climate scenarios. We generated an ENM using published reports of V. cholerae in seawater and freely available remotely sensed imagery. Models indicated that factors associated with V. cholerae presence included chlorophyll-a, pH, and sea surface temperature (SST), with chlorophyll-a demonstrating the greatest explanatory power from variables selected for model calibration. We identified specific geographic areas for potential V. cholerae distribution. Coastal Bangladesh, where cholera is endemic, was found to be environmentally similar to coastal areas in Latin America. In a conservative climate change scenario, we observed a predicted increase in areas with environmental conditions suitable for V. cholerae. Findings highlight the potential for vulnerability maps to inform cholera surveillance, early warning systems, and disease prevention and control.

Klebsiella pneumoniae Liver Abscess: An Emerging Disease☆

ABSTRACT Most of the cases of Klebsiella pneumoniae liver abscess reported early on were from Asia, predominantly Taiwan, with a significant number of patients being middle aged diabetic men, and developing metastatic complications, especially endophthalmitis. The entity is now being increasingly recognized in the United States. In this article, the authors review those reported cases, and also the literature regarding the pathophysiology of this intriguing syndrome.

Successful malaria elimination in the Ecuador–Peru border region: epidemiology and lessons learned

BackgroundIn recent years, malaria (Plasmodium vivax and Plasmodium falciparum) has been successfully controlled in the Ecuador–Peru coastal border region. The aim of this study was to document this control effort and to identify the best practices and lessons learned that are applicable to malaria control and to other vector-borne diseases. A proximal outcome evaluation was conducted of the robust elimination programme in El Oro Province, Ecuador, and the Tumbes Region, Peru. Data collection efforts included a series of workshops with local public health experts who played central roles in the elimination effort, review of epidemiological records from Ministries of Health, and a review of national policy documents. Key programmatic and external factors are identified that determined the success of this eradication effort.Case descriptionFrom the mid 1980s until the early 2000s, the region experienced a surge in malaria transmission, which experts attributed to a combination of ineffective anti-malarial treatment, social-ecological factors (e.g., El Niño, increasing rice farming, construction of a reservoir), and political factors (e.g., reduction in resources and changes in management). In response to the malaria crisis, local public health practitioners from El Oro and Tumbes joined together in the mid-1990s to forge an unofficial binational collaboration for malaria control. Over the next 20xa0years, they effectively eradicated malaria in the region, by strengthening surveillance and treatment strategies, sharing of resources, operational research to inform policy, and novel interventions.Discussion and evaluationThe binational collaboration at the operational level was the fundamental component of the successful malaria elimination programme. This unique relationship created a trusting, open environment that allowed for flexibility, rapid response, innovation and resilience in times of crisis, and ultimately a sustainable control programme. Strong community involvement, an extensive microscopy network and ongoing epidemiologic investigations at the local level were also identified as crucial programmatic strategies.ConclusionThe results of this study provide key principles of a successful malaria elimination programme that can inform the next generation of public health professionals in the region, and serve as a guide to ongoing and future control efforts of other emerging vector borne diseases globally.

Micronutrients and dengue.

Dengue virus infection is the most widespread mosquito-borne viral infection in humans and has emerged as a serious global health challenge. In the absence of effective treatment and vaccine, host factors including nutritional status, which may alter disease progression, need investigation. The interplay between nutrition and other infections is well-established, and modulation of nutritional status often presents a simple low-cost method of interrupting transmission, reducing susceptibility, and/or ameliorating disease severity. This review examines the evidence on the role of micronutrients in dengue virus infection. We found critical issues and often inconsistent results across studies; this finding along with the lack of sufficient literature in this field have limited our ability to make any recommendations. However, vitamins D and E have shown promise in small supplementation trials. In summary, the role of micronutrients in dengue virus infection is an exciting research area and needs to be examined in well-designed studies with larger samples.

The high burden of dengue and chikungunya in southern coastal Ecuador: Epidemiology, clinical presentation, and phylogenetics from a prospective study in Machala in 2014 and 2015

Background Dengue (DENV), chikugunya (CHIKV) and zika (ZIKV) viruses are arboviruses transmitted by the Ae. aegypti mosquito, that cause febrile illness and present a major public health challenge in tropical low– and middle-income countries such as Ecuador. Here we report the methods and findings from the first two years (January 1, 2014 to December 31, 2015) of an active and passive surveillance study conducted in the southern coastal city of Machala, Ecuador. Methods Individuals whom presented at one of four sentinel clinics or the central hospital of the Ministry of Health with suspected DENV (index cases) were recruited into the study (n = 324). Index cases with confirmed acute DENV infection triggered a cluster investigation (n = 44) of DENV infections in the index household and four neighboring households (associates) within 200 meters, (n = 397). We conducted genomic sequencing and phylogenetic analysis of select DENV positive samples from 2014. Results In 2014, 72.5% of index patients and 35.6% of associates had evidence of acute or recent DENV infections. In 2015, 28.3% and 12.85% of index patients and associates, respectively, had acute or recent infections. The first cases of CHIKV were detected in an associate on epidemiological week 12 in 2015. There were a total of 54 cases of acute CHIKV infections, including seven DENV/CHIKV co-infections. No cases of ZIKV were detected. DENV symptoms varied significantly by age and by primary versus secondary infections. Symptoms that were associated with DENV and CHIKV infections are presented. Phylogenetic analyses of isolates revealed genetic relatedness and shared ancestry of DENV1, DENV2 and DENV4 genomes from Ecuador with those from Venezuela and Colombia, as well as more than one introduction of the same serotype into Ecuador, indicating presence of viral flow between Ecuador and the surrounding countries. Discussion Findings from this study highlight the importance of (1) implementing rapid active surveillance protocols and (2) strengthening local molecular diagnostic capacities in resource-limited settings where DENV, CHIKV, and ZIKV co-circulate.

Case Report: An Acute Chikungunya Infection and a Recent Secondary Dengue Infection in a Peripartum Case in Ecuador

Dengue virus (DENV) and chikungunya virus (CHIKV) are transmitted by the same mosquito vectors and now co-circulate in many parts of the world; however, coinfections and serial infections are not often diagnosed or reported. A 38-week pregnant woman was admitted to the hospital with a diagnosis of suspected DENV and CHIKV in southern coastal Ecuador. The pregnancy was complicated by mild polyhydramnios and fetal tachycardia, and a healthy newborn was born. The patient was positive for a recent secondary DENV infection (Immunoglobulin M and Immunoglobulin G positive) and an acute CHIKV infection (real-time reverse transcriptase polymerase chain reaction positive) (Asian genotype). The newborn was not tested for either virus. This case resulted in a benign clinical course with a favorable pregnancy outcome.

Spatiotemporal Variation in Environmental Vibrio cholerae in an Estuary in Southern Coastal Ecuador

Cholera emergence is strongly linked to local environmental and ecological context. The 1991–2004 pandemic emerged in Perú and spread north into Ecuador’s El Oro province, making this a key site for potential re-emergence. Machala, El Oro, is a port city of 250,000 inhabitants, near the Peruvian border. Many livelihoods depend on the estuarine system, from fishing for subsistence and trade, to domestic water use. In 2014, we conducted biweekly sampling for 10 months in five estuarine locations, across a gradient of human use, and ranging from inland to ocean. We measured water-specific environmental variables implicated in cholera growth and persistence: pH, temperature, salinity, and algal concentration, and evaluated samples in five months for pathogenic and non-pathogenic Vibrio cholerae, by polymerase chain reaction (PCR). We found environmental persistence of pandemic strains O1 and O139, but no evidence for toxigenic strains. Vibrio cholerae presence was coupled to algal and salinity concentration, and sites exhibited considerable seasonal and spatial heterogeneity. This study indicates that environmental conditions in Machala are optimal for cholera re-emergence, with risk peaking during September, and higher risk near urban periphery low-income communities. This highlights a need for surveillance of this coupled cholera–estuarine system to anticipate potential future cholera outbreaks.

The Burden of Dengue Fever and Chikungunya in Southern Coastal Ecuador: Epidemiology, Clinical Presentation, and Phylogenetics from the First Two Years of a Prospective Study

Abstract. Here, we report the findings from the first 2 years (2014–2015) of an arbovirus surveillance study conducted in Machala, Ecuador, a dengue-endemic region. Patients with suspected dengue virus (DENV) infections (index cases, N = 324) were referred from five Ministry of Health clinical sites. A subset of DENV-positive index cases (N = 44) were selected, and individuals from the index household and four neighboring homes within 200 m were recruited (N = 400). Individuals who entered the study, other than the index cases, are referred to as associates. In 2014, 70.9% of index cases and 35.6% of associates had acute or recent DENV infections. In 2015, 28.3% of index cases and 12.8% of associates had acute or recent DENV infections. For every DENV infection captured by passive surveillance, we detected an additional three acute or recent DENV infections in associates. Of associates with acute DENV infections, 68% reported dengue-like symptoms, with the highest prevalence of symptomatic acute infections in children aged less than 10 years. The first chikungunya virus (CHIKV) infections were detected on epidemiological week 12 in 2015; 43.1% of index cases and 3.5% of associates had acute CHIKV infections. No Zika virus infections were detected. Phylogenetic analyses of isolates of DENV from 2014 revealed genetic relatedness and shared ancestry of DENV1, DENV2, and DENV4 genomes from Ecuador with those from Venezuela and Colombia, indicating the presence of viral flow between Ecuador and surrounding countries. Enhanced surveillance studies, such as this, provide high-resolution data on symptomatic and inapparent infections across the population.

Environmental cholera (Vibrio cholerae) dynamics in an estuarine system in southern coastal Ecuador

Cholera emergence is strongly linked to local environmental and ecological context. The 1991- 2004 pandemic emerged in Perú and spread north into Ecuador’s El Oro province, making this a key site for potential re-emergence. Machala, El Oro, is a port city of 250,000, near the Peruvian border. Many livelihoods depend on the estuarine system, from fishing for subsistence and trade, to domestic water use. In 2014, we conducted biweekly sampling for 10 months in five estuarine locations, across a gradient of human use, and ranging from inland to ocean. We measured water-specific environmental variables implicated in cholera growth and persistence: pH, temperature, salinity, and algal concentration, and evaluated samples in 5 months for pathogenic and non-pathogenic Vibrio cholerae, by polymerase chain reaction (PCR). We found environmental persistence of pandemic strains O1 and O139, but no evidence for toxigenic strains. Cholera presence was coupled to algal and salinity concentration, and sites exhibited considerable seasonal and spatial heterogeneity. This study indicates that environmental conditions in Machala are optimal for cholera re-emergence, with risk peaking during September, and higher risk near urban periphery low-income communities. This highlights a need for surveillance of this coupled cholera– estuarine system to anticipate potential future cholera outbreaks.Abstract Cholera emergence is strongly linked to local environmental and ecological context. The 1991-2004 pandemic emerged in Peru and spread north into Ecuador’s El Oro province, making this a key site for potential re-emergence. Machala, El Oro, is a port city of 250,000, near the Peruvian border. Many livelihoods depend on the estuarine system, from fishing for subsistence and trade, to domestic water use. In 2014, we conducted biweekly sampling for 10 months in five estuarine locations, across a gradient of human use, and ranging from inland to ocean. We measured water characteristics implicated in V. cholerae growth and persistence: pH, temperature, salinity, and algal concentration, and evaluated samples in five months for pathogenic and non-pathogenic Vibrio cholerae, by polymerase chain reaction (PCR). We found environmental persistence of strains O1 and O139, but no evidence for toxigene presence. V. cholerae presence was coupled to algal and salinity concentration, and sites exhibited considerable seasonal and spatial heterogeneity. This study indicates that environmental conditions in Machala are optimal for human cholera re-emergence, with risk peaking during September, and higher risk near urban periphery low-income communities. This highlights a need for surveillance of this coupled cholera– estuarine system to anticipate potential future outbreaks.

Social-ecological factors and preventive actions decrease the risk of dengue infection at the household-level: Results from a prospective dengue surveillance study in Machala, Ecuador

Background In Ecuador, dengue virus (DENV) infections transmitted by the Aedes aegypti mosquito are among the greatest public health concerns in urban coastal communities. Community- and household-level vector control is the principal means of controlling disease outbreaks. This study aimed to assess the impact of knowledge, attitudes, and practices (KAPs) and social-ecological factors on the presence or absence of DENV infections in the household. Methods In 2014 and 2015, individuals with DENV infections from sentinel clinics in Machala, Ecuador, were invited to participate in the study, as well as members of their household and members of four neighboring households located within 200 meters. We conducted diagnostic testing for DENV on all study participants; we surveyed heads of households (HOHs) regarding demographics, housing conditions and KAPs. We compared KAPs and social-ecological factors between households with (n = 139) versus without (n = 80) DENV infections, using bivariate analyses and multivariate logistic regression models with and without interactions. Results Significant risk factors in multivariate models included proximity to abandoned properties, interruptions in piped water, and shaded patios (p<0.05). Significant protective factors included the use of mosquito bed nets, fumigation inside the home, and piped water inside the home (p<0.05). In bivariate analyses (but not multivariate modeling), DENV infections were positively associated with HOHs who were male, employed, and of younger age than households without infections (p<0.05). DENV infections were not associated with knowledge, attitude, or reported barriers to prevention activities. Discussion Specific actions that can be considered to decrease the risk of DENV infections in the household include targeting vector control in highly shaded properties, fumigating inside the home, and use of mosquito bed nets. Community-level interventions include cleanup of abandoned properties, daily garbage collection, and reliable piped water inside houses. These findings can inform interventions to reduce the risk of other diseases transmitted by the Ae. aegypti mosquito, such as chikungunya and Zika fever.