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Antecedentes. El ausentismo escolar es un problema importan-te relacionado con altas tasas de abandono escolar, bajo rendimiento académico y rezago escolar. Este estudio determinó la frecuencia y las causas del ausentismo general y el ausentismo relacionado con la enfermedad en estudiantes de escuelas rurales de dos municipios de Colombia. Métodos. Se realizó un estudio descriptivo en una población de 948 escolares de 34 escuelas rurales. Los datos de ausentismo recopilados para el año 2013 consistieron en el número de episodios y días de ausentismo por grado y motivo de ausencia general y por enfermedad. Se calcularon las tasas de ausentismo general y por enfermedad. Resultados. El 55,1% de la población participante eran hombres y el 71,6% tenían entre 5 y 9 años. La tasa de ausentismo general fue 5,7 episodios por niño-año, IC 95% (5,5-5,8) y 8,6 días por niño-año, IC 95% (8,4-8,9). Las principales razones del ausentismo fueron enfermedades (24,4%), chequeo médico u odontológico (12,9%), viajes (12,3%), falta de motivación para asistir a la escuela (10,0%) y mal clima (9,3%). La tasa de ausentismo por enfermedad fue 1,4 episodios por niño-año IC 95% (1,3-1,5) y 2,5 días por niño-año IC 95% (2,4-2,6). Las principales razones del ausentismo por enfermedad fueron el resfriado común (37,0%), la fiebre inespecífica (10,9%) y el dolor de estómago o vómito (8,4%). Conclusiones. Las razones más comunes para la no asistencia estuvieron relacionadas con la enfermedad. La importancia de las infecciones respiratorias y gastrointestinales en el absentismo fue evidente, mostrando tasas similares a las de otros estudios en escuelas urbanas. Los resultados de este estudio proporcionan conocimiento sobre la magnitud y las razones del absentismo en la población escolar rural Background: School absenteeism is a considerable problem generally related to higher dropout rates, poor academic achievement and school lag. This study determined the frequency and causes of overall and ill-ness-related absenteeism of students in rural schools from two Colombian municipalities. Methods: A prospective and descriptive study was conducted in a popula-tion of 948 school children from 34 rural schools. Absenteeism data were collected for 2013 academic year consisted of the number of students registered and absent by grade, school, day and reason for absence. Absence rates (overall and illness-related absenteeism) were recorded, based on full or partial days absence, measured both as episodes, and accumulating the number of days. Results: From the students included in the study, 55.1% were male and 71.6% were between 5 and 9 years old. The overall absence rate was 5.7 episodes per child-year (95% confidence interval 5.5 to 5.8) and 8.6 days per child-year (8.4 to 8.9). The main reasons for non-attendance were ill-ness (24.4%), medical or dental check-up (12.9%), travel (12.3%), lack of motivation to attend school (10.0%) and bad weather (9.3%). The illness-related absence rate was 1.4 episodes per child-year (95% confidence in-terval 1.3 to 1.5) and 2.5 days per child-year (2.4 to 2.6). The main reasons for illness-related absence were cold (37.0%), nonspecific fever (10.9%) and stomach pain or vomiting (8.4%). Conclusions: In this study, the most common reasons for non-attendance were illness-related. The importance of respiratory and gastrointestinal infections in absenteeism was evident, showing rates similar to other urban school studies. Then, the results of this study provide knowledge on the magnitude and reasons for absenteeism in rural schoolchildren.

Soil-transmitted helminths (STHs) are a major health concern globally. Infection is mostly through contact with contaminated water, food or soil. Therefore to break the cycle of viable transmission STH eggs must be quantitatively detected in the environment. The effect of different reagents on the viability of Ascaris suum eggs during laboratory detection and quantification was assessed and different incubation solutions compared. Sulphuric acid gave a slightly higher recovery percentage of viable eggs (91.2%) than distilled water (90.0%) and 0.5% formalin (87.6%), although the difference was not statistically significant (p > 0.05). Acetoacetic acid, ethyl acetate, ammonium bicarbonate, zinc sulphate, magnesium sulphate and Tween 80, are reagents widely used in test protocols for the detection and quantification of STH eggs. Eggs were exposed to these reagents for different time durations. Acetoacetic acid resulted in the highest loss of viability (3.4 ± 0.7% viable), while magnesium sulphate resulted in the least effect (88.5 ± 1.2% viable). In conclusion the use of the selected reagents in the detection of these eggs was found to affect the viability of exposed eggs, especially during prolonged exposures. Therefore we recommended that eggs be exposed for ≤ 5 minutes, to reduce the risk of viability loss.

Introduction: Dengue is a public health problem in tropical and subtropical regions of the world. Studies on dengue in rural areas are scarce since the disease is considered mainly urban. Objective: To determine the knowledge (K), attitudes (A) and practices (P) of dengue in an endemic area in Colombia. Materials and methods: We conducted a cross-sectional study with 515 pupils (7-16 years old) in 34 rural schools in Anapoima and La Mesa municipalities during 2011. Each KAP category was evaluated independently by a scoring system and then categorized into high, medium or low. Results: Pupils recognized knowledge variables such as the symptoms (fever, bone pain), transmission route (mosquito bites), and mosquito breeding sites (uncovered wáter tanks, solid waste). Average scores on attitude were high in both municipalities indicating a well-developed perception of disease severity. Seeking treatment in medical centers and self-medication for fever management and the use of mosquito net and space-spraying of insecticides were the most frequently identified practices. Discussion: This is the first KAP dengue study performed in a rural area in Colombia and as such it contributes to the understanding of dengue perceptions by the inhabitants of these areas. It showed a medium level of knowledge about dengue and a lower level of preventive practices in pupils from rural schools. It also showed that pupils considered space-spraying as crucial for vector control. The presence of the vector in rural areas of the country underlines the need to improve surveillance and education to more effectively control the vector and promote prevention methods including community participation. Resumen Introducción. El dengue es un problema de salud pública en las regiones tropicales y subtropicales del mundo. Los estudios sobre la enfermedad en áreas rurales son escasos debido a que se presenta principalmente en los núcleos urbanos. Objetivo. Determinar los conocimientos, las actitudes y las prácticas sobre el dengue en un área rural endémica en Colombia. Materiales y métodos. Se hizo un estudio transversal con 515 estudiantes, entre los 7 y los 16 años de edad en 34 escuelas rurales de los municipios de Anapoima y La Mesa en el 2011. Cada categoría se evaluó por separado con un puntaje clasificado como alto, medio o bajo. Resultados. Los estudiantes reconocieron los síntomas (fiebre, dolor de huesos), la ruta de transmisión (picadura de mosquitos) y los criaderos (depósitos de agua destapados, residuos sólidos). El promedio de los puntajes de actitudes fue alto en ambos municipios, lo que indica que percibían la gravedad del dengue. Las prácticas más frecuentes de tratamiento de la fiebre fueron la consulta médica y la automedicación, en tanto que los métodos de control más frecuentes fueron el uso de mosquiteros y el rociamiento con insecticidas. Discusión. Este es el primer estudio de conocimientos, actitudes y prácticas sobre el dengue en un área rural de Colombia. Los resultados contribuyen a entender las percepciones de la enfermedad en sus habitantes y evidenciaron niveles medios de conocimiento y puntuaciones bajas en cuanto a las prácticas entre los estudiantes de las escuelas rurales. Los estudiantes consideraron que la fumigación es importante para el control del vector. La presencia del mosquito en áreas rurales del país resalta la necesidad de mejorar la vigilancia y la educación para lograr un control efectivo del vector y promover métodos de prevención que incluyan la participación comunitaria.

The use of sludge in agriculture has been encouraged as a means of increasing soil nutrient content and improving the water holding capacity. On the negative side, major public health concerns with sludge application prevail, mainly due to the high concentration of pathogenic microorganisms. Soil-transmitted helminths (STHs) are of major health concern in this regard, especially in endemic regions, mainly due to the high environmental resistant of the eggs combined with a low infectious dose. In this study the concentration of STH eggs in two months dried sludge from Durban, South Africa and Dakar, Senegal was determined and compared. Sampling was carried out from January to October 2016 and in September 2016 for Dakar. Ascaris spp, hookworm, Trichuris spp, Taenia spp and Toxocara spp were the commonly recorded STH eggs. STH egg concentrations were higher in Dakar than in Durban, with viable STH egg concentrations exceeding both local and international guidelines. Due to the high concentration of viable STH eggs, risks of Ascaris spp infection was very high for farmers applying this sludge on their farms in both Durban (7.9 × 10−1 (±1.7 × 10−2)) and Dakar (9.9 × 10−1 (±1.3 × 10−5)). Consumption of lettuce grown on sludge amended soil will result in probable infections but harvest after 30 days between sludge application and harvest in Durban gave median probability infection risks with a risk level similar to the WHO tolerable risk value (10−4). This time period need to be prolonged to harvest in Dakar to 40 days to reduce the risks of infection to the tolerable risks values. Further treatment of the sludge either through composting or drying for longer periods of time is thus recommended from a public health perspective., Highlights • Sludge contained high concentration of viable STH eggs after 60 days of drying. • The concentration of these eggs exceeded both national and international guidelines for reuse. • Farmers and consumers of the farm produce are likely to be infected with Ascaris spp. • Further treatment of the sludge is thus recommended from a public health perspective.

Wastewater irrigation is associated with several benefits but can also lead to significant health risks. The health risk for contracting infections from Soil Transmitted Helminths (STHs) among farmers has mainly been assessed indirectly through measured quantities in the wastewater or on the crops alone and only on a limited scale through epidemiological assessments. In this study we broadened the concept of infection risks in the exposure assessments by measurements of the concentration of STHs both in wastewater used for irrigation and the soil, as well as the actual load of STHs ova in the stool of farmers and their family members (165 and 127 in the wet and dry seasons respectively) and a control group of non-farmers (100 and 52 in the wet and dry seasons, respectively). Odds ratios were calculated for exposure and non-exposure to wastewater irrigation. The results obtained indicate positive correlation between STH concentrations in irrigation water/soil and STHs ova as measured in the stool of the exposed farmer population. The correlations are based on reinfection during a 3 months period after prior confirmed deworming. Farmers and family members exposed to irrigation water were three times more likely as compared to the control group of non-farmers to be infected with Ascaris (OR = 3.9, 95% CI, 1.15–13.86) and hookworm (OR = 3.07, 95% CI, 0.87–10.82). This study therefore contributes to the evidence-based conclusion that wastewater irrigation contributes to a higher incidence of STHs infection for farmers exposed annually, with higher odds of infection in the wet season., Author Summary Wastewater irrigation in agriculture is a common reality in many developing cities, linked to rapid urbanization. Approximately 50%-90% of urban dwellers in West Africa consume wastewater/ polluted surface water irrigated-vegetables within cities with 10% of the population involved in the practice. Viral, bacterial and parasitic pathogens can all be found in wastewater putting exposed populations at risk of pathogenic infections. The biggest risk however is to helminth infections, due to their long survival time in the environment. Wastewater irrigation has been practiced in Ghana for many years, however few studies have investigated the epidemiological link between the practice and helminth infections among the farmers. In this study the authors measured the helminth ova concentration in wastewater used for irrigation and the infection loads of farmers as well as a non-farmer control group in Ghana. They reported high concentrations of helminth ova in the wastewater as well as soil on the farms, above the World Health Organization (WHO) guidelines for wastewater irrigation, which resulted in a three times higher probability of infections with helminths for farmers as compared to the non-farmer control group. This research provides information on the direct link between wastewater irrigation and helminth infection in exposed individuals.

The storage of water within the household environment is commonly practiced in many countries in South-east Asia including Laos and Thailand. The practice if not properly managed, can lead to diarrhoea and dengue as a result of faecal contamination and Aedes (Ae) aegypti productions of stored water. In Laos and Thailand, diarrhoea and dengue are prevalent. However, the relationship between these diseases and household water storage remains largely obscured and therefore need to be identified for better disease prevention and control. The overall aim of this study was to determine causal factors and health risks associated with faecal contamination and Ae. aegypti infestation in household water storage in Laos and Thailand. The specific objectives were to: i) identify risk factors of Escherichia coli (E. coli) contamination and Ae. aegypti pupae infestation in household water storage containers; ii) Assess risk factors and their contribution (Proportion Attributable Fraction (PAF)) to diarrhoeal disease incidence; and iii) Assess the incidence and risk factors of dengue-like illness (DLI), and identify dengue infections. To address the study objectives, cross-sectional and longitudinal surveys were conducted in one suburban and one rural village each in Laos and Thailand. The purpose of the crosssectional survey was to gather information on the potential causal factors of E. coli contamination in stored drinking water, and Ae. aegypti infestation in domestic water containers. The longitudinal had the purposes to collect information on the incidence of DLI and diarrhoeal disease in relation to mentioned risk factors. A total of 478 households were covered in the cross-sectional survey while 2,007 individuals were enrolled in the longitudinal survey. Descriptive analysis and multi-variate regression models were used to describe the characteristics of risk factors, and to find significant relationships between the different risk factors and dengue and diarrhoea in each village. The cross-sectional survey revealed contamination of E. coli in household drinking water as well as high levels of Ae. aegypti infestation in the water storage containers in all study villages. Higher E. coli concentrations in drinking water were found in Laos than in Thailand, especially in households without toilets (in Laos) and in rural, rather than in suburban villages. The significant risk factors of E. coli contamination varied across study villages. In suburban Laos, the significant factors associated with E. coli contamination of stored water in the households were wooden house material, containers (jars and bottles), and households without toilets; whereas in rural Laos the factors were rain-fed water, containers covered with lids and households without toilets. In suburban Thailand significant factors associated with the occurrence of E. coli in drinking water were rain-fed containers, jars, buckets and container cleaning frequency; whereas in rural Thailand they were houses made of wood, manually collected rainwater and container cleaning frequency. The study revealed that E. coli contamination was less associated with socio-demographic characteristics. Regarding dengue vector production, the number of pupae collected in the study exceeded proposed dengue transmission thresholds of 0.5-1.5 pupae per person. It was shown that most of the household water storage containers in all study villages were without lids, did not contain larvicide temephos and were cleaned less frequently. Household water management and socio-demographic factors were more likely to be associated with Ae. aegypti pupae infestation. Factors that were significantly associated with Ae. aegypti infestations were tanks, less frequent cleaning of containers, containers without lids, and containers located outdoors or in toilets/bathrooms. The two-year longitudinal survey on diarrhoeal disease and dengue showed that among 2,007 individuals in the four villages, 97 diarrhoeal cases with no deaths were found comprising 35 and 11 cases in suburban and rural Laos, and 12 and 39 cases for Thai villages, respectively. The study showed that diarrhoeal incidence remains a problem for children under-five years of age, especially in suburban Laos and rural Thailand where the numbers of cases were more frequently reported. The incidences of diarrhoeal disease in under-five year old children in suburban Laos and rural Thailand were 170.5 and 180.0 episodes per 1000 person-years, respectively. The incidence reported in this study was higher than in data from the national surveillance system in both countries. In these settings, the risk factors of diarrhoea were mostly hygiene followed by socio-demographic factors. In suburban Laos, households with children under-five years of age were more likely to report a diarrhoea case (PAF: 58%), followed by households with cooking and feeding utensils left unwashed in the kitchen (PAF: 11%) and households disposing children’s stools in the open (PAF: 8%). In rural Thailand, the highest risk attributed to diarrhoea was associated with a delay in cleaning utensils (PAF: 53%). In addition to diarrhoeal disease, 83 DLI cases were recorded within the same follow up population; these included 69 in suburban Laos, 11 in rural Thailand and 3 in rural Laos (none were found in suburban Thailand). Among these 83 DLI, four (4.8%) were positive for dengue which included two cases each from suburban Laos (DENV serotype 1) and rural Thailand (DENV serotype 2). In suburban Laos, the significant risk factors of DLI were associated with household members within the age cohort of 15-20 years, people’s service occupations and the occupation group ‘other’ (retired and children). In rural Thailand, there were no significant associations between DLI and risk factors in the multivariate model. The household water storage containers have an impact not only on the microbial deterioration of drinking water, but also on production of immature Ae. aegypti. This can potentially lead to further occurrence of both dengue and diarrhoea in these settings. However, the occurrence of DLI was not significantly associated with the observed Ae. aegypti pupae per person index, even though this index was generally higher than the proposed dengue transmission threshold of 0.5-1.5 pupae per person. Based on the results in this thesis, it is recommended that stored drinking water should be treated prior to drinking in order to prevent diarrhoea in households with poor water quality. Provision of toilet facilities in Laos should be made urgently to improve quality of stored drinking water and control against diarrhoea related to improper disposal of the baby stool. Immediate cleaning of utensils after eating or cooking is also important for the reduction of diarrhoea in both Laos and Thailand. Furthermore, to achieve significant reductions in Ae. aegypti production and dengue, health education programs should be conducted on the proper use of fitted lids together with weekly cleaning of smaller water containers, as well as on proper use of larvicide temephos strictly in large water-holding containers such as tanks and jars, which were the most infested containers identified in this study. Also, adult mosquito control must also be considered in an integrated vector management strategy. Although compliance is always an issue when it comes to mosquito control, community participation will be key to the success of any selected control measure. Oppbevaring av vann i husholdninger er vanlig praksis i mange land i sør-øst Asia inkludert Laos og Thailand. Denne praksis forblir en av de største risiko faktorene for diare og dengue som et resultat av fekal forurensing og Aedes (Ae) aegypti produksjon hvis den ikke blir håndtert skikkelig. I Laos og Thailand er både diare og dengue vanlig forekommende. Sammenhengen mellom disse sykdommene og vannlagring i husholdninger er fortsatt uklar og må derfor identifiseres for å bedre prevensjon og kontroll av disse sykdommene. Hovedmålsettingen til denne PhD oppgave var å bestemme helserisiko i Laos og Thailand forbundet med lagret husholdningsvann som er forurenset fekalt og infisert med Ae. aegypti mygg. De spesifikke målsetningene var å 1) identifisere risikofaktorer til mikrobiell forurensning i lagret drikkevann, 2) identifisere risikofaktorer til infestasjon av Ae. aegypti pupper i vanntanker i husholdninger 3) vurdere risikofaktorer og deres bidrag til diareinsidens, 4) vurdere insidens og risikofaktorer denguelignende infeksjoner og å identifisere dengueinfeksjoner. For å løse studiemålene ble det gjennomført tverrsnitts- og longitudinelle undersøkelser i en forstadlandsby (suburban) og en landlig landsby (rural) hver i Laos og Thailand. Formålet med tverrsnittsundersøkelsen var å samle informasjon om de potensielle årsaksforholdene til E. coli-forurensning i lagret drikkevann og Ae. aegypti angrep i husholdningsvannbeholdere. Den longitudinelle undersøkelsen hadde til formål å samle inn informasjon om forekomsten av denguelignende og diarésykdommer i forhold til nevnte risikofaktorer. Totalt 478 husholdninger i tverrsnittsundersøkelsen og 2,007 personer ble inkludert i den longitudinelle undersøkelsen. Beskrivende analyse og multivariate regresjonsmodeller ble brukt til å beskrive karakteristikker av risikofaktorer, og til å finne viktige forhold mellom de forskjellige risikofaktorene og dengue og diare i hver landsby. Tverrsnittsundersøkelsen viste høye nivåer av E. coli forurensing i drikkevann og høye nivåer av Ae. aegypti infestasjon i vannbeholdere i mange husholdninger i alle landsbyene. Høyere E. coli konsentrasjonene i drikkevann ble funnet i Laos enn i Thailand, spesielt i husholdninger uten toalett (i Laos) og i landlige landsbyer snarere enn i forstadslandsbyer. Signifikante risikofaktorer for E. coli forurensing varierte mellom landsbyene. I forstads Laos var risiko faktorene assosiert med husmaterial av tre, beholdere (krukker og flasker) og husholdninger uten toalett; mens i landlige Laos var faktorene regn-basert vann, beholdere dekket med lokk og husholdninger uten toalett. I forstads Thailand var de betydningsfulle faktorene assosiert med E. coli i drikkevann regnvann i beholdere, krukker, bøtter og rengjøringsfrekvensen av beholdere; mens i landlige Thailand var de husmaterial av tre, manuelt innsamlet regnvann og rengjøringsfrekvensen av beholdere. Studien viste at E. coli forurensing var mindre assosiert med sosial-demografisk karakteristikker. Med tanke på dengue mygg produksjon, så var antallet myggpupper per person høyere enn foreslåtte grenseverdier på 0.5-1.5 myggpupper per person, dermed gir en høy risiko for både diare og dengue infeksjon under disse forholdene. Mesteparten av husholdningenes vannbeholdere i alle landbyene var uten lokk, hadde ingen larvicide temephos, og var rengjort sjeldnere. Håndtering av husholdningsvann og sosial-demografiske faktorer var mer sannsynlig assosiert med Ae. aegypti puppe infestasjon. Betydningsfulle faktorer som var assosiert med Ae. aegypti infestasjon var vanntanker, beholdere uten lokk og beholdere lokalisert utendørs eller i toalett/bad. Et toårs studie av diaresykdommer viste at av 2,007 individuelle personer i de fire landsbyene ble det funnet 97 diaretilfeller og ingen dødsfall. Disse inkluderer 35 tilfeller i forstads Laos, 11 i landlige Laos, 12 forstads Thailand, og 39 i landlige Thailand. Studiet viste at diare forekomster er et problem for barn under 5 år gamle, spesielt i forstads Laos og landlige Thailand hvor antall rapporterte tilfeller var høye. Forekomst av diare sykdommer blant barn under 5 år i forstads Laos og landlige Thailand var respektive 170.5 og 180.0 episoder per 1000 persondager. Disse verdiene var høyere enn data fra det nasjonale overvåkelsesystemet i begge landene. Under disse forholdene var risikofaktorene for diare for det meste assosiert med hygiene og deretter sosio-demografiske forhold. I forstads Laos var det for det meste barn under 5 år som var utsatt for diare (PAF: 58%), fulgt av de som hadde uvasket redskap på kjøkkenet (PAF: 11%) og de som kastet avføring fra barn i det åpne (PAF: 8%). I landlige Thailand var den høyeste risikoen med tanke på diare assosiert med utsettelse av vasking av redskap (PAF: 53%). I tillegg til diare sykdommer, ble det registrert 83 DLI (dengue-lignende infeksjoner) pasienter, hvor 69 var fra forstads Laos, 11 fra landlige Thailand og 3 i landlige Laos (ingen av de ble funnet i forstads Thailand). Av disse 83 DLI pasientene var 4 funnet positive for dengue (4.8%). Det inkluderer 2 tilfeller fra forstads Laos (DENV serotype 1) og landlige Thailand (DENV serotype 2). I forstads Laos, var risikofaktorene for DLI infeksjon assosiert med aldersgruppen mellom 15 og 20 år, sysselsetting (service og ‘andre’ yrkesgrupper, dvs. pensjonister og barn). I landlige Thailand var det ingen betydningsfulle assosiasjoner mellom DLI og risikofaktorer. Husholdningsvanntanker påvirker ikke bare mikrobiell forurensing av drikkevann, men også produksjon av Ae. Aegypti mygg. Dette kan potensielt føre til ytterligere forekomst av både dengue og diaré i disse områder. Imidlertid var forekomsten av DLI ikke signifikant forbundet med det observerte Ae. aegypti puppe per person, selv om denne indeksen var generelt høyere enn den foreslåtte dengueoverføringsgrensen på 0,5-1,5 pupper per person. I henhold til resultat i denne avhandling, rekommanderes at lagret drikke vann bør behandles før konsumpsjon for å forhindre diare i husholdninger med dårlig drikkevannkvalitet. Anskaffelse av forbedrede toaletter i Laos bør gjøres raskt for å forbedre kvaliteten på lagret drikkevann og kontroll av diaré relatert til feilaktig bortskaffelse av babyavføring. Umiddelbar rengjøring av redskap etter spising eller matlaging er også viktig for å redusere diaretilfeller i både Laos og Thailand. For å oppnå betydningsfull reduksjon av Ae. aegypti produksjon og dengue bør helseopplæringsprogrammer utføres på riktig bruk av lokk på vannbeholdere sammen med ukentlig rengjøring av mindre vannbeholdere, samt om riktig bruk av larviciden temephos for bruk i store vannbeholdere som tanker og krukker som var de mest infiserte beholderne i denne studien. Kontroll av voksne mygg må også vurderes i en integrert vektorkontroll strategi. Selv om overholdelse alltid er et problem når det gjelder myggkontroll, vil samfunnsdeltakelse være nøkkelen til suksess til hvilken som helst kontrollmåte.