An optimal control problem for carrier dependent diseases.

In developing countries, several diseases spread in human population due to the abundance of houseflies (a kind of carrier). The main reason behind the spread of these diseases is the lack of awareness among peoples regarding the sanitation practices and economic constraints. To understand the dynamics of the spread and control of these diseases, in this paper, we propose a mathematical model by considering logistic growth of houseflies. In the model formulation, it is assumed that houseflies transport the bacteria responsible for the disease transmission from the environment to the edibles of human population. To reduce the density of houseflies and number of infected individuals, an optimization problem is also formulated and analyzed. Numerical simulations are performed to support analytically obtained results.

Relación deltre hipotiroidismo subclínico y bocio con el origen del agua consumida por una población del conurbano bonaerense / Relationship of subclinical hypothyroidism and goiter with the origin of water consumed by a population of the Buenos Aires suburbs

El hipotiroidismo subclínico (HS), elevación de tirotrofina con hormonas tiroideas normales, junto al bocio, aumentó la frecuencia en las últimas décadas. Con el objetivo de relacionar la prevalencia de bocio y HS con el consumo de agua subterránea como factor de riesgo etiológico poblacional, se analizaron 879 historias clínicas de un centro médico de Glew, en el conurbano bonaerense Sur. Se estudió la población según edad (20-60 y 12-19 años) y tipo de agua consumida (potabilizada o napa subterránea). El agua subterránea fue consumida por el 70.5% del grupo de 20 a 60 años (n = 559, 79.9% mujeres) y por el 66.3% del grupo de 12 a 19 años (n = 57, 81.4% mujeres). En el grupo de 20 a 60 años la prevalencia de HS en consumidores de agua potabilizada y subterránea fue del 1% y 57.8% (p < 0.0001) y la de bocio de 3.8% y 38.9% (p < 0.0001), respectivamente; con un riesgo atribuible al agua subterránea de 57% para HS y 35% para bocio. En el grupo de 12 a 19 años, la prevalencia de HS fue 6.9% y 52.6% (p < 0.0001) y de bocio 13.8% y 77.2% para los grupos de agua potabilizada y subterránea, (p < 0.0001) respectivamente; con un riesgo atribuible al agua subterránea de 46% para HS y 61% para bocio. El análisis fisicoquímico mostró presencia de nitratos (entre 24 y 83 mg/l) en aguas de pozos y ausencia en agua potable. La prevalencia aumentada de HS y bocio podrían deberse a la acción disruptora tiroidea de los nitratos.

Subclinical hypothyroidism (SH), elevation of the level of thyrotrophin with normal thyroid hormones, along with goiter (glandular size > 25g), increased in recent decades. In order to relate the prevalence of goiter and SH with the consumption of groundwater, as a population etiological risk factor, we analyzed 879 clinical histories from a medical center in the city of Glew in the South Buenos Aires suburbs. The population was studied according to age (20 to 60 and 12 to 19 years) and type of water consumed (potable water or groundwater). Groundwater was consumed by 70.5% of the group from 20 to 60 years old (n = 559, 79.9% women) and by 66.3% of the group from 12 to 19 years old (n = 57, 81.4% women In the group of 20 to 60 years, the prevalence of SH in potable water and groundwater users was 1% and 57.8% (p < 0.0001) and the goiter rate of 3.8% and 38.9% (p < 0.0001) respectively; with an attributable risk to groundwater of 57% for HS, and 35% for goiter In the group of 12 to 19 years, the prevalence of SH was 6.9% and 52.6% (p < 0.0001) and goiter 13.8% and 77.2% for the water and groundwater groups (p>0.0001) respectively, with an attributable risk of 46% for HS y 61% for goiter. The physicochemical analysis showed the presence of nitrates in the range of 24 to 83 mg/l in groundwater and absence in potable water. The increased prevalence of HS and goiter could be due to the thyroid disrupting action of nitrates.

[Relationship of subclinical hypothyroidism and goiter with the origin of water consumed by a population of the Buenos Aires suburbs]. / Relación del hipotiroidismo subclínico y bocio con el origen del agua consumida por una población del conurbano bonaerense.

Subclinical hypothyroidism (SH), elevation of the level of thyrotrophin with normal thyroid hormones, along with goiter (glandular size > 25g), increased in recent decades. In order to relate the prevalence of goiter and SH with the consumption of groundwater, as a population etiological risk factor, we analyzed 879 clinical histories from a medical center in the city of Glew in the South Buenos Aires suburbs. The population was studied according to age (20 to 60 and 12 to 19 years) and type of water consumed (potable water or groundwater). Groundwater was consumed by 70.5% of the group from 20 to 60 years old (n = 559, 79.9% women) and by 66.3% of the group from 12 to 19 years old (n = 57, 81.4% women In the group of 20 to 60 years, the prevalence of SH in potable water and groundwater users was 1% and 57.8% (p < 0.0001) and the goiter rate of 3.8% and 38.9% (p < 0.0001) respectively; with an attributable risk to groundwater of 57% for HS, and 35% for goiter In the group of 12 to 19 years, the prevalence of SH was 6.9% and 52.6% (p < 0.0001) and goiter 13.8% and 77.2% for the water and groundwater groups (p > 0.0001) respectively, with an attributable risk of 46% for HS y 61% for goiter. The physicochemical analysis showed the presence of nitrates in the range of 24 to 83 mg/l in groundwater and absence in potable water. The increased prevalence of HS and goiter could be due to the thyroid disrupting action of nitrates.

A spatial analysis of giardiasis and cryptosporidiosis in relation to public water supply distribution in North West England.

Giardia and Cryptosporidium are both waterborne parasites and leading causes of gastroenteritis. Although specimens from diarrhoeic patients are routinely examined for Cryptosporidium, they are often not examined for Giardia so many cases go undiagnosed. Since 2002, all faecal specimens in Central Lancashire have been tested for infection with Giardia and Cryptosporidium. The aim of this paper is to gain insight into the factors contributing to giardiasis and cryptosporidiosis, including evidence of transmission via drinking water. Our analysis found a higher risk of both conditions for young children and a second peak in risk of giardiasis in adults. There was a significantly higher risk of giardiasis for males and a higher risk of cryptosporidiosis for females. The geographical location was significant, with an increased risk in the north. Residence in an area with increased supply from one water treatment works was a significant predictor for cryptosporidiosis.

Climate Change Impacts on Waterborne Diseases: Moving Toward Designing Interventions.

PURPOSE: Climate change threatens progress achieved in global reductions of infectious disease rates over recent decades. This review summarizes literature on potential impacts of climate change on waterborne diseases, organized around a framework of questions that can be addressed depending on available data. RECENT FINDINGS: A growing body of evidence suggests that climate change may alter the incidence of waterborne diseases, and diarrheal diseases in particular. Much of the existing work examines historical relationships between weather and diarrhea incidence, with a limited number of studies projecting future disease rates. Some studies take social and ecological factors into account in considerations of historical relationships, but few have done so in projecting future conditions. The field is at a point of transition, toward incorporating social and ecological factors into understanding the relationships between climatic factors and diarrheal diseases and using this information for future projections. The integration of these components helps identify vulnerable populations and prioritize adaptation strategies.

Wastewater treatment and public health in Nunavut: a microbial risk assessment framework for the Canadian Arctic.

Wastewater management in Canadian Arctic communities is influenced by several geographical factors including climate, remoteness, population size, and local food-harvesting practices. Most communities use trucked collection services and basic treatment systems, which are capable of only low-level pathogen removal. These systems are typically reliant solely on natural environmental processes for treatment and make use of existing lagoons, wetlands, and bays. They are operated in a manner such that partially treated wastewater still containing potentially hazardous microorganisms is released into the terrestrial and aquatic environment at random times. Northern communities rely heavily on their local surroundings as a source of food, drinking water, and recreation, thus creating the possibility of human exposure to wastewater effluent. Human exposure to microbial hazards present in municipal wastewater can lead to acute gastrointestinal illness or more severe disease. Although estimating the actual disease burdens associated with wastewater exposures in Arctic communities is challenging, waterborne- and sanitation-related illness is believed to be comparatively higher than in other parts of Canada. This review offers a conceptual framework and evaluation of current knowledge to enable the first microbial risk assessment of exposure scenarios associated with food-harvesting and recreational activities in Arctic communities, where simplified wastewater systems are being operated.

A waterborne outbreak of multiple diarrhoeagenic Escherichia coli infections associated with drinking water at a school camp.

BACKGROUND: In June 2015, a local public health laboratory was notified that students had developed gastroenteritis symptoms after attending a camp. An outbreak investigation was conducted to determine the extent and cause of the outbreak. METHOD: A retrospective cohort study was conducted to determine the correlations between the illness and specific exposures at the school camp. All attendees were interviewed with a standard questionnaire that addressed clinical symptoms, food consumption, and environmental exposures. Clinical specimens were cultured using standard microbiological methods for bacterial and viral pathogens. The genetic relationships of all isolates were determined using pulsed-field gel electrophoresis (PFGE). RESULTS: A total 188 patients with symptoms of diarrhoea, abdominal pain, and nausea were identified. The completed questionnaires suggested that the consumption of drinking water was likely to be linked to this outbreak. Using microbiological methods, enterohaemorrhagic Escherichia coli, enteropathogenic E. coli, and enteroaggregative E. coli were isolated, and the isolates from both patient stool and environmental water samples displayed indistinguishable XbaI-PFGE patterns. The water system in the camp used groundwater drawn from a private underground reservoir for cooking and drinking. The environmental investigation revealed some problems with the water supply system, such as the use of inappropriate filters in the water purifier and a defect in the pipeline between the reservoir and the chlorination device. CONCLUSIONS: This outbreak points to the importance of drinking water quality management in group facilities where underground water is used and emphasizes the need for periodic sanitation and inspection to prevent possible waterborne outbreaks.

Symptoms and risk factors of Cryptosporidium hominis infection in children: data from a large waterborne outbreak in Sweden.

Cryptosporidium is a major cause of diarrheal disease worldwide. In developing countries, this infection is endemic and in children, associated with growth faltering and cognitive function deficits, with the most severe impact on those aged <2 years. Little has been reported about symptoms and risk factors for children in industrialized countries, although the disease incidence is increasing in such regions. In November 2010, a large waterborne outbreak of C. hominis occurred in the city of Östersund in Sweden. Approximately 27,000 of the 60,000 inhabitants were symptomatic. We aimed to describe duration of symptoms and the risk factors for infection with C. hominis in children aged <15 years in a Western setting. Within 2 months after a boil water advisory, a questionnaire was sent to randomly selected inhabitants of all ages, including 753 children aged <15 years. Those with ≥3 loose stools/day were defined as cases of diarrhoea. The response rate was 70.3%, and 211 children (39.9%) fulfilled the case definition. Mean duration of diarrhoea was 7.5 days (median 6, range 1-80 days). Recurrence, defined as a new episode of diarrhoea after ≥2 days of normal stools, occurred in 52.5% of the cases. Significant risk factors for infection, besides living within the distribution area of the contaminated water plant, included a high level of water consumption, male sex, and a previous history of loose stools. The outbreak was characterized by high attack and recurrence rates, emphasizing the necessity of water surveillance to prevent future outbreaks.

Waterborne disease outbreak detection: an integrated approach using health administrative databases.

Hundreds of waterborne disease outbreaks (WBDO) of acute gastroenteritis (AGI) due to contaminated tap water are reported in developed countries each year. Such outbreaks are probably under-detected. The aim of our study was to develop an integrated approach to detect and study clusters of AGI in geographical areas with homogeneous exposure to drinking water. Data for the number of AGI cases are available at the municipality level while exposure to tap water depends on drinking water networks (DWN). These two geographical units do not systematically overlap. This study proposed to develop an algorithm which would match the most relevant grouping of municipalities with a specific DWN, in order that tap water exposure can be taken into account when investigating future disease outbreaks. A space-time detection method was applied to the grouping of municipalities. Seven hundred and fourteen new geographical areas (groupings of municipalities) were obtained compared with the 1,310 municipalities and the 1,706 DWN. Eleven potential WBDO were identified in these groupings of municipalities. For ten of them, additional environmental investigations identified at least one event that could have caused microbiological contamination of DWN in the days previous to the occurrence of a reported WBDO.

A controlled survey of less typical long-term consequences after an extensive waterborne epidemic.

BACKGROUND: Extensive backflow of treated wastewater caused household water contamination in a Finnish town in 2007. The drinking water of 9 500 residents became heavily polluted with faecal microbes, resulting in a large gastroenteritis epidemic. Cases of reactive arthritis, milder joint symptoms and prolonged gastrointestinal symptoms were observed after the outbreak. A follow-up survey was performed to study less familiar long-term health consequences within a year from the outbreak. METHODS: The contaminated group comprised a sample of residents of the area with polluted water supply (N = 323) and the control group a sample of residents in a nearby municipality (N = 186). The presence of 20 general symptoms or complaints was inquired by a mail survey. Quarterly prevalence of each symptom or complaint was measured. Twelve of these proceeded to further analysis. RESULTS: The response rate was 53% (323/615) in the contaminated group and 54% (186/343) in the control group. Rash, eye irritation, heartburn and weight loss were more prevalent in the contaminated group during the first year quarter. In the last year quarter, only eye irritation was significantly more common in the contaminated group. CONCLUSION: The excess prevalence of four complaints at the first year quarter can be explained by acute gastroenteritis or intensive water chlorination. The excess prevalence of eye irritation at the fourth year quarter cannot be explained by chlorination anymore but might be a sign of co-existing reactive joint disease. In general, long-term consequences of the outbreak can be considered minor in terms of the surveyed symptoms or complaints.

Automated detection of case clusters of waterborne acute gastroenteritis from health insurance data - pilot study in three French districts.

This pilot study was conducted to assess the utility of using a health insurance database for the automated detection of waterborne outbreaks of acute gastroenteritis (AGE). The weekly number of AGE cases for which the patient consulted a doctor (cAGE) was derived from this database for 1,543 towns in three French districts during the 2009-2012 period. The method we used is based on a spatial comparison of incidence rates and of their time trends between the target town and the district. Each municipality was tested, week by week, for the entire study period. Overall, 193 clusters were identified, 10% of the municipalities were involved in at least one cluster and less than 2% in several. We can infer that nationwide more than 1,000 clusters involving 30,000 cases of cAGE each year may be linked to tap water. The clusters discovered with this automated detection system will be reported to local operators for investigation of the situations at highest risk. This method will be compared with others before automated detection is implemented on a national level.

Waterborne diseases classification and relationship with social-environmental factors in Florianópolis city - Southern Brazil.

This study aimed to investigate and classify the occurrence of waterborne diseases in Florianópolis city, Santa Catarina State, Southern Brazil and to correlate these diseases with the following social-environmental indicators of the local population: type of water supply, adequate collection and sewage treatment, areas of flooding and domestic water tank cleaning. Reports of outpatients were analyzed for surveillance of waterborne diseases during the period of 2002 to 2009. Waterborne diseases were classified into four groups: Group A: diarrheal diseases; Group B: parasitological diseases; Group C: skin diseases and Group D: eye diseases. The diarrheal, parasitological and skin diseases were the most frequently reported. Waterborne diseases belonging to Group A in all sites were correlated with other waterborne diseases groups, which can be an indicator of the circulation of other waterborne diseases. Regarding the social-environmental indicators assessed, the most correlated with waterborne diseases were the origin and quality of the water supply, followed by inadequate collection and treatment of sewage, frequent flooding, and finally the lack of cleanliness of the water reservoir. The results highlight the need for policies aiming for improvement of the sanitation service in the maintenance of human, animal and environmental health.

Hospitalizations due to selected infections caused by opportunistic premise plumbing pathogens (OPPP) and reported drug resistance in the United States older adult population in 1991-2006.

The Flint Water Crisis-due to changes of water source and treatment procedures-has revealed many unsolved social, environmental, and public health problems for US drinking water, including opportunistic premise plumbing pathogens (OPPP). The true health impact of OPPP, especially in vulnerable populations such as the elderly, is largely unknown. We explored 108 claims in the largest US national uniformly collected data repository to determine rates and costs of OPPP-related hospitalizations. In 1991-2006, 617,291 cases of three selected OPPP infections resulted in the elderly alone of $0.6 billion USD per year of payments. Antibiotic resistance significantly increased OPPP illness costs that are likely to be underreported. More precise estimates for OPPP burdens could be obtained if better clinical, microbiological, administrative, and environmental monitoring data were cross-linked. An urgent dialog across governmental and disciplinary divides, and studies on preventing OPPP through drinking water exposure, are warranted.

Integrating surveillance data on water-related diseases and drinking-water quality; action-research in a Brazilian municipality.

The Brazilian Ministry of Health proposed a research study involving municipal professional staff conducting both epidemiological and water quality surveillance to facilitate the integration of the data which they collected. It aimed to improve the intersectoral collaboration and health promotion activities in the municipalities, especially regarding drinking-water quality. We then conducted a study using the action-research approach. At its evaluation phase, a technique which we called 'the tree analogy' was applied in order to identify both possibilities and challenges related to the proposed interlinkage. Results showed that integrating the two data collection systems cannot be attained without prior institutional adjustments. It suggests therefore the necessity to unravel issues that go beyond the selection and the interrelation of indicators and compatibility of software, to include political, administrative and personal matters. The evaluation process led those involved to re-think their practice by sharing experiences encountered in everyday practice, and formulating constructive criticisms. All this inevitably unleashes a process of empowerment. From this perspective, we have certainly gathered some fruit from the Tree, but not necessarily the most visible.

A Systematic Review of Waterborne Disease Outbreaks Associated with Small Non-Community Drinking Water Systems in Canada and the United States.

BACKGROUND: Reports of outbreaks in Canada and the United States (U.S.) indicate that approximately 50% of all waterborne diseases occur in small non-community drinking water systems (SDWSs). Summarizing these investigations to identify the factors and conditions contributing to outbreaks is needed in order to help prevent future outbreaks. OBJECTIVES: The objectives of this study were to: 1) identify published reports of waterborne disease outbreaks involving SDWSs in Canada and the U.S. since 1970; 2) summarize reported factors contributing to outbreaks, including water system characteristics and events surrounding the outbreaks; and 3) identify terminology used to describe SDWSs in outbreak reports. METHODS: Three electronic databases and grey literature sources were searched for outbreak reports involving SDWSs throughout Canada and the U.S. from 1970 to 2014. Two reviewers independently screened and extracted data related to water system characteristics and outbreak events. The data were analyzed descriptively with 'outbreak' as the unit of analysis. RESULTS: From a total of 1,995 citations, we identified 50 relevant articles reporting 293 unique outbreaks. Failure of an existing water treatment system (22.7%) and lack of water treatment (20.2%) were the leading causes of waterborne outbreaks in SDWSs. A seasonal trend was observed with 51% of outbreaks occurring in summer months (p<0.001). There was large variation in terminology used to describe SDWSs, and a large number of variables were not reported, including water source and whether water treatment was used (missing in 31% and 66% of reports, respectively). CONCLUSIONS: More consistent reporting and descriptions of SDWSs in future outbreak reports are needed to understand the epidemiology of these outbreaks and to inform the development of targeted interventions for SDWSs. Additional monitoring of water systems that are used on a seasonal or infrequent basis would be worthwhile to inform future protection efforts.

Water from fruit or the river? Examining hydration strategies and gastrointestinal illness among Tsimane' adults in the Bolivian Amazon.

OBJECTIVE: Water is an essential nutrient overlooked in many cross-cultural studies of human nutrition. The present article describes dietary water intake patterns among forager-horticulturalist adults in lowland Bolivia, compares daily intake with international references and examines if variation in how people acquire water relates to gastrointestinal illness. DESIGN: Cross-sectional observational study used survey, anthropometric and qualitative methods with Tsimane' adults selected by age and sex stratification sampling in one community. SETTING: Research occurred in one Tsimane' village in the Beni department, Bolivia with limited access to clean water. The 24 h diet and health recalls were conducted in July-August 2012 and qualitative interviews/ethnographic observation in September-October 2013. SUBJECTS: Forty-five Tsimane' household heads (49% men) took part in the first data collection and twenty-two Tsimane' (55% men) were included in the follow-up interviews. RESULTS: Men and women reported consuming 4·9 litres and 4·4 litres of water daily from all dietary sources, respectively. On average, water from foods represented 50 % of total water intake. Thirteen per cent of participants reported symptoms of gastrointestinal illness. In a logistic regression model adjusted for age, BMI, sex and raw water consumed, each percentage increase in water obtained from foods was associated with a reduced risk of gastrointestinal illness (OR=0·92; 95% CI 0·85, 0·99). CONCLUSIONS: Both total water intake and percentage of water from foods were higher than averages in industrialized countries. These findings suggest that people without access to clean water may rely on water-rich foods as a dietary adaptation to reduce pathogen exposures.