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1.
BMC Infect Dis ; 20(1): 803, 2020 Oct 29.
Artículo en Inglés | MEDLINE | ID: mdl-33121458

RESUMEN

BACKGROUND: Soil-transmitted helminths are more prevalent in tropics and sub-tropics including Ethiopia. Despite their high prevalence, direct saline microscopy with its low sensitivity has been used as a diagnostic method in almost all health facilities in Ethiopia. Alternative diagnostic methods which have higher sensitivity are not yet implemented. Therefore, this study aimed to compare and evaluate the performance of diagnostic methods for soil transmitted helminths. METHODS: A cross-sectional study among 520 school children was conducted from October to December, 2019 in Amhara National Regional State. The study participants were selected using systematic random sampling technique. Stool samples were processed via formol ether concentration, Kato-Katz, spontaneous tube sedimentation and agar plate culture techniques. Data was entered into Epi-data version 3.1 and analysis was done using SPSS version 20.0. The sensitivity, specificity, and negative predictive value were calculated against the combined result. Strength of agreement of the diagnostic methods was determined by Kappa value. RESULTS: The Overall prevalence of soil transmitted helminths was 40.8% using combination of methods. The prevalence 24.4, 22.5, and 32.4%, respectively was recorded by using formol ether concentration, Kato-Katz and spontaneous tube sedimentation. The highest prevalence of hookworm (29.2%) was detected by the agar plate culture. The sensitivity and negative predictive value of formol ether concentration were 57.9 and 78.4%, for Kato-Katz thick smear 55.2 and 76.4%, for spontaneous tube sedimentation were 79.2 and 87.5% to soil transmitted helminths detection, respectively. The sensitivity and negative predictive value of agar plate culture to hookworm detection were 86.4 and 93.5%, respectively. CONCLUSION: Spontaneous tube sedimentation shows higher sensitivity in the detection of soil transmitted helminth infections. Agar plate culture method also indicated better performance for hookworm detection than other methods. Therefore, the employment of spontaneous tube sedimentation technique for routine laboratory and agar plate culture for research purposes will significantly aid in accurate diagnosis of parasitic infections.


Asunto(s)
Ancylostomatoidea/aislamiento & purificación , Pruebas Diagnósticas de Rutina/métodos , Infecciones por Uncinaria/diagnóstico , Infecciones por Uncinaria/transmisión , Suelo/parasitología , Adolescente , Animales , Niño , Estudios Transversales , Etiopía/epidemiología , Heces/parasitología , Femenino , Formaldehído , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/parasitología , Humanos , Masculino , Microscopía/métodos , Prevalencia , Sensibilidad y Especificidad
2.
J Parasitol ; 106(3): 383-391, 2020 06 01.
Artículo en Inglés | MEDLINE | ID: mdl-32491171

RESUMEN

The long-term fidelity of pinniped hosts to their natal rookery site suggests the genetic architecture of their Uncinaria spp. hookworms should be strongly structured by host breeding biology. However, historical events affecting host populations may also shape parasite genetic structure. Sequences of the mitochondrial cytochrome c oxidase 1 (COI) gene of 86 Uncinaria lucasi individuals were obtained to assess genetic variation and structure of nematodes from 2 host species (68 hookworms from northern fur seals; 18 hookworms from Steller sea lions) and rookeries from 3 widely separated geographic regions: the western Bering Sea and Sea of Okhotsk, eastern Bering Sea, and the eastern Pacific Ocean. High COI haplotype (h = 0.96-0.98) and nucleotide (π = 0.014) diversity was found. The haplotype network showed a star-shaped pattern with a large number of haplotypes separated by few substitutions. The network did not show separation of U. lucasi by geographic region or host species. Fst values between U. lucasi individuals representing geographic regions showed no differentiation, consistent with the absence of genetic structure. At face value, this lack of genetic structure in U. lucasi suggests high gene flow but could also be explained by recent (post-glacial) population expansions of northern fur seals and their hookworms.


Asunto(s)
Ancylostomatoidea/fisiología , Caniformia/parasitología , Infecciones por Uncinaria/veterinaria , Secuencia de Aminoácidos , Ancylostomatoidea/genética , Animales , Secuencia de Bases , Complejo IV de Transporte de Electrones/genética , Femenino , Variación Genética , Haplotipos/genética , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/transmisión , Masculino , Mitocondrias/enzimología , Océano Pacífico , Alineación de Secuencia/veterinaria
3.
PLoS Negl Trop Dis ; 13(11): e0007488, 2019 11.
Artículo en Inglés | MEDLINE | ID: mdl-31765383

RESUMEN

INTRODUCTION: Few studies have simultaneously examined the role of sanitation conditions at the home, school, and community on soil-transmitted helminth (STH) infection. We examined the contribution of each domain that children inhabit (home, village, and school) to STH infection and estimated the association of STH infection with sanitation in each domain. METHODS: Using data from 4,104 children from Kwale County, Kenya, who reported attending school, we used logistic regression models with cross-classified random effects to calculate measures of general contextual effects and estimate associations of village sanitation coverage (percentage of households with reported access to sanitation), school sanitation coverage (number of usable toilets per enrolled pupil), and sanitation access at home with STH infection. FINDINGS: We found reported use of a sanitation facility by households was associated with reduced prevalence of hookworm infection but not with reduced prevalence of T. trichiura infection. School sanitation coverage > 3 toilets per 100 pupils was associated with lower prevalence of hookworm infection. School sanitation was not associated with T. trichiura infection. Village sanitation coverage > 81% was associated with reduced prevalence of T. trichiura infection, but no protective association was detected for hookworm infection. General contextual effects represented by residual heterogeneity between village and school domains had comparable impact upon likelihood of hookworm and T. trichiura infection as sanitation coverage in either of these domains. CONCLUSION: Findings support the importance of providing good sanitation facilities to support mass drug administration in reducing the burden of STH infection in children.


Asunto(s)
Composición Familiar , Helmintiasis/epidemiología , Helmintiasis/prevención & control , Características de la Residencia/estadística & datos numéricos , Saneamiento/estadística & datos numéricos , Instituciones Académicas/estadística & datos numéricos , Suelo/parasitología , Adolescente , Ancylostomatoidea , Animales , Niño , Preescolar , Estudios Transversales , Femenino , Helmintiasis/transmisión , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/prevención & control , Infecciones por Uncinaria/transmisión , Humanos , Higiene , Kenia/epidemiología , Modelos Logísticos , Masculino , Prevalencia , Factores de Riesgo , Población Urbana/estadística & datos numéricos
4.
Ann Glob Health ; 85(1)2019 09 11.
Artículo en Inglés | MEDLINE | ID: mdl-31517465

RESUMEN

BACKGROUND: Soil-transmitted helminths (STH) have remained a major threat to humans, especially children in developing countries, including Nigeria. Interventions have always been geared towards school-aged children, neglecting preschool-aged children and occupational risk adults. The Soil-Transmitted Helminthiasis Advisory Committee (STHAC) recently suggested incorporating other at-risk groups. OBJECTIVE: This study assessed the associated risk of STH infection among agrarian communities of Kogi State, Nigeria. METHODS: A total of 310 individuals of all ages participated in the cross-sectional survey. Stool samples were analyzed using standard Kato-Katz method. RESULTS: A total of 106 (34.2%) individuals were infected with at least one STH. Hookworm was the most prevalent (18.1%); followed by Ascaris lumbricoides (16.8%). Worm intensity was generally light. Prevalence of infection was similar between four age groups considered (preschool, school, 'women of reproductive age' and older at-risk group). Poor socio-economic status (SES) was a major risk for STH infection. Using a 20-asset based criteria, 68 (23.1%) and 73 (24.7%) of 295 questionnaire respondents were classified into first (poorest) and fifth (richest) wealth quintiles respectively. Risk of infection with STH was 60% significantly lower in the richest wealth quintile compared to the poorest (Prevalence Ratio [PR] = 0.4843, 95% CI = 0.2704-0.8678, p = 0.015). Open defecators were more likely to harbour STH than those who did not (PR = 1.7878, 95% CI = 1.236-2.5846, p = 0.00201). Pit latrine and water closet toilets each approximately reduced STH infection by 50% (p < 0.05). CONCLUSION: Preventive chemotherapy for all age groups, health education and provision of basic amenities especially toilets are needed in order to achieve the goal toward the 2020 target of STH control.


Asunto(s)
Ascariasis/epidemiología , Conocimientos, Actitudes y Práctica en Salud , Infecciones por Uncinaria/epidemiología , Suelo/parasitología , Tricuriasis/epidemiología , Adolescente , Adulto , Agricultura , Animales , Ascariasis/parasitología , Ascariasis/transmisión , Ascaris lumbricoides , Niño , Preescolar , Estudios Transversales , Defecación , Heces/parasitología , Femenino , Infecciones por Uncinaria/transmisión , Humanos , Masculino , Persona de Mediana Edad , Nigeria/epidemiología , Pobreza , Prevalencia , Medición de Riesgo , Clase Social , Cuartos de Baño/estadística & datos numéricos , Tricuriasis/transmisión , Adulto Joven
5.
Parasit Vectors ; 12(1): 442, 2019 Sep 16.
Artículo en Inglés | MEDLINE | ID: mdl-31522687

RESUMEN

BACKGROUND: As many countries with endemic soil-transmitted helminth (STH) burdens achieve high coverage levels of mass drug administration (MDA) to treat school-aged and pre-school-aged children, understanding the detailed effects of MDA on the epidemiology of STH infections is desirable in formulating future policies for morbidity and/or transmission control. Prevalence and mean intensity of infection are characterized by heterogeneity across a region, leading to uncertainty in the impact of MDA strategies. In this paper, we analyze this heterogeneity in terms of factors that govern the transmission dynamics of the parasite in the host population. RESULTS: Using data from the TUMIKIA study in Kenya (cluster STH prevalence range at baseline: 0-63%), we estimated these parameters and their variability across 120 population clusters in the study region, using a simple parasite transmission model and Gibbs-sampling Monte Carlo Markov chain techniques. We observed great heterogeneity in R0 values, with estimates ranging from 1.23 to 3.27, while k-values (which vary inversely with the degree of parasite aggregation within the human host population) range from 0.007 to 0.29 in a positive association with increasing prevalence. The main finding of this study is the increasing trend for greater parasite aggregation as prevalence declines to low levels, reflected in the low values of the negative binomial parameter k in clusters with low hookworm prevalence. Localized climatic and socioeconomic factors are investigated as potential drivers of these observed epidemiological patterns. CONCLUSIONS: Our results show that lower prevalence is associated with higher degrees of aggregation and hence prevalence alone is not a good indicator of transmission intensity. As a consequence, approaches to MDA and monitoring and evaluation of community infection status may need to be adapted as transmission elimination is aimed for by targeted treatment approaches.


Asunto(s)
Transmisión de Enfermedad Infecciosa , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/transmisión , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Número Básico de Reproducción , Niño , Preescolar , Erradicación de la Enfermedad , Femenino , Humanos , Lactante , Recién Nacido , Kenia/epidemiología , Masculino , Administración Masiva de Medicamentos , Persona de Mediana Edad , Modelos Estadísticos , Prevalencia , Encuestas y Cuestionarios , Adulto Joven
6.
Pak J Pharm Sci ; 32(2 (Supplementary)): 799-803, 2019 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-31103975

RESUMEN

Information on prevalence of soil-transmitted helminth (STH) infections among school children is scarce in Pakistan. This study was aimed to investigate the prevalence of soil-transmitted helminth in school children of three districts in, Khyber Pakhtunkhwa, Pakistan. A total of 300 stool samples were examined from August 2015 to August 2016 using direct smear (Normal saline and Lugol's Iodine solution) and the concentration methods. One hundred and eighty seven (62.3%) pupils were found infected with soil-transmitted helminths. One hundred and forty five (77.5%) were infected with single parasite and forty two (22.4%) with multiple infections. Ascaris lumbricoides 125 (66.4%), Trichuris trichura 50 (26.5%) and Ancylostoma duedenale 13 (6.91%) were detected. The children above 8 years in age were more parasitized than below 8 years (p=0.7832; P>0.05). Males were found more parasitized than females (p=0.9315; P>0.05). Children in lower Dir district were found more infected followed by Swat and upper Dir (P< 0.0001; p<0.05). No significant relationship was found among the examined and that of infected children for ages and sex in all the districts. Malakand division is an area with poor hygiene located in temperate zone near the border of Afghanistan and China. The prevalence of reported nematode parasites here compared with the same studies is unexpectedly high. These types of studies should continue time to time to know the hazardous nature of such parasitic infections for the betterment of the human health.


Asunto(s)
Helmintiasis/epidemiología , Helmintiasis/transmisión , Animales , Ascariasis/epidemiología , Ascariasis/transmisión , Ascaris lumbricoides/aislamiento & purificación , Niño , Coinfección/epidemiología , Coinfección/parasitología , Estudios Transversales , Heces/parasitología , Femenino , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/transmisión , Humanos , Masculino , Pakistán/epidemiología , Prevalencia , Microbiología del Suelo , Tricuriasis/epidemiología , Tricuriasis/transmisión , Trichuris/aislamiento & purificación , Trichuris/patogenicidad
7.
Acta Trop ; 197: 105035, 2019 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-31128094

RESUMEN

Large sectors of the Afghan population have limited access to safe water and sanitation, which increases the risk of transmission of water- and food- borne diseases, including Soil-Transmitted Helminth (STH) infections. STHs interfere with the human host's health status, and their burden of disease is highest among children of school age. Based on the results of a nationwide survey conducted in 2003, which showed an STH prevalence of 47.2%, and with the aim of reducing morbidity among school children, Afghanistan has been conducting nationwide deworming for preschool-age and school-age children since 2004. In 2017, 14 years after the first baseline assessment, a follow-up survey was carried out among schoolchildren aged 8-10 years to provide an update on STH epidemiology and facilitate evidence-informed planning of future deworming campaigns. Stool samples were collected from 2263 pupils aged 8-10 years in five provinces representing the different ecological zones of the country - Kabul, Balkh, Herat, Nangarhar and Kandahar. Microscopic examination was carried out by the Kato-Katz thick smear technique, to assess the presence and the number of parasites and/or their eggs. The survey revealed that 26.6% of the sample was infected with at least one of the STH, a marked decrease from the level registered in 2003. The most prevalent infection was the one with A. lumbricoides (25.7%), followed by T. trichiura (1.0%) and hookworms (0.1%). All positive children were noted to have light-intensity infections, compared to the previous survey where 9.7% of the sample had moderate-to-heavy intensity infections. Only 0.2% of the children had co-infection with two or more parasites. Meanwhile, 6.8% of the students were found infected with the dwarf tapeworm, Hymenolepis nana. The absence of infections of moderate-to-heavy intensity after several yearly rounds of deworming and overall improvements in provision of safe water and sanitation, indicates successful control of morbidity due to STH and, overall, their elimination as a public-health problem from Afghanistan. Nevertheless, current levels of prevalence of infection still show persistence of active transmission of STHs, thus justifying the continued implementation of mass deworming interventions among children. The permanent elimination of STH transmission, however, will be possible only when the country reaches a sanitation level sufficient to impede fecal contamination of the environment with human excreta.


Asunto(s)
Helmintiasis/epidemiología , Afganistán/epidemiología , Ancylostomatoidea/aislamiento & purificación , Animales , Ascariasis/epidemiología , Ascaris lumbricoides/aislamiento & purificación , Niño , Estudios Transversales , Heces/parasitología , Femenino , Helmintiasis/transmisión , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/transmisión , Humanos , Himenolepiasis/epidemiología , Hymenolepis nana/aislamiento & purificación , Masculino , Recuento de Huevos de Parásitos , Prevalencia , Saneamiento , Instituciones Académicas , Suelo/parasitología , Estudiantes , Encuestas y Cuestionarios , Tricuriasis/epidemiología , Tricuriasis/transmisión , Trichuris/aislamiento & purificación
8.
BMC Res Notes ; 12(1): 231, 2019 Apr 16.
Artículo en Inglés | MEDLINE | ID: mdl-30992048

RESUMEN

OBJECTIVE: The aim of this study was to determine the prevalence of soil transmitted helminthes among primary school children. School based cross-sectional study design was employed. A total of six hundred study subjects were selected by a multistage sampling method. Fresh stool specimens were collected using clean, dry and wide mouthed labeled stool cups. It was processed by Kato-Katz technique. The data were analyzed using SPSS version 20 and p-value < 0.05 was considered statistically significant. RESULT: The overall prevalence of soil transmitted helminthes was 57 (9.5%). Hookworm was the most prevalent helminthes species isolated (4.2%) followed by A. lumbricoide (3%). The prevalence of Taenia species, T. trichiura, H. nana and E. vermicularis were; 1.2%, 0.5%, 0.7% and 0.8% respectively. The prevalence of the Soil transmitted helminthes infection was low and all cases of Soil transmitted infections in this study were with low infection intensity. This might be due to the preventive chemotherapy given to the school children.


Asunto(s)
Ancylostomatoidea/aislamiento & purificación , Ascariasis/epidemiología , Ascaris lumbricoides/aislamiento & purificación , Infecciones por Uncinaria/epidemiología , Taenia/aislamiento & purificación , Teniasis/epidemiología , Adolescente , Ancylostomatoidea/clasificación , Animales , Antihelmínticos/administración & dosificación , Ascariasis/parasitología , Ascariasis/prevención & control , Ascariasis/transmisión , Ascaris lumbricoides/clasificación , Niño , Preescolar , Estudios Transversales , Etiopía/epidemiología , Heces/parasitología , Femenino , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/prevención & control , Infecciones por Uncinaria/transmisión , Humanos , Masculino , Profilaxis Pre-Exposición/métodos , Prevalencia , Instituciones Académicas , Suelo/parasitología , Taenia/clasificación , Teniasis/parasitología , Teniasis/prevención & control , Teniasis/transmisión
10.
Parasitol Res ; 117(11): 3507-3517, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-30120589

RESUMEN

Infections due to soil-transmitted helminths (STHs), i.e. Ascaris lumbricoides, Trichuris trichiura, hookworms, and Strongyloides stercoralis, are widely distributed in tropical and subtropical areas in which approximately 1.5 billion people are infected. A clear understanding of the epidemiology and distribution of diseases is an important aid for control and prevention. The aim of our study was to identify the effects of environmental and climatic factors on distribution patterns of STHs and to develop a risk map for STH infections under current environmental and climate regimes in Thailand. Geographical information systems (GIS), remote sensing, and Maximum Entropy (MaxEnt) algorithm software were used to determine the significant factors and to create predictive risk maps for STH infections in Thailand. The disease data from Thailand covered the years from 1969 to 2014, while environmental and climatic data were compiled from the Worldclim database, MODIS satellite imagery, Soilgrids and ISCGM. The models predicted that STHs occur mainly in southern Thailand. Mean annual precipitation was the factor most affecting the current distribution of A. lumbricoides, T. trichiura, and S. stercoralis. Land cover class was the main predictor for distribution of S. stercoralis and important for hookworms. Altitude was the dominant factor affecting the distribution of hookworms, and mean temperature of the wettest quarter was significantly associated with A. lumbricoides distribution. A predicted distribution map of STHs to identify environmental risk factors in Thailand is presented. This work provides a model for use in STH monitoring and health planning not only in Thailand but also in other countries with similar disease conditions.


Asunto(s)
Ancylostomatoidea/aislamiento & purificación , Ascaris lumbricoides/aislamiento & purificación , Enfermedades Gastrointestinales/parasitología , Helmintiasis/epidemiología , Helmintiasis/transmisión , Suelo/parasitología , Strongyloides stercoralis/aislamiento & purificación , Trichuris/aislamiento & purificación , Animales , Ascariasis/epidemiología , Ascariasis/parasitología , Ascariasis/transmisión , Niño , Clima , Entropía , Sistemas de Información Geográfica , Helmintiasis/parasitología , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/transmisión , Humanos , Prevalencia , Tecnología de Sensores Remotos , Estrongiloidiasis/epidemiología , Estrongiloidiasis/parasitología , Estrongiloidiasis/transmisión , Tailandia/epidemiología , Tricuriasis/epidemiología , Tricuriasis/parasitología , Tricuriasis/transmisión
11.
PLoS Negl Trop Dis ; 11(11): e0006088, 2017 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-29176840

RESUMEN

Human excreta is a low cost source of nutrients vital to plant growth, but also a source of pathogens transmissible to people and animals. We investigated the cost-savings and infection risk of soil transmitted helminths (STHs) in four scenarios where farmers used either inorganic fertilizer or fresh/composted human excreta supplemented by inorganic fertilizer to meet the nutrient requirements of rice paddies in the Red River Delta, Vietnam. Our study included two main components: 1) a risk estimate of STH infection for farmers who handle fresh excreta, determined by systematic review and meta-analysis; and 2) a cost estimate of fertilizing rice paddies, determined by nutrient assessment of excreta, a retailer survey of inorganic fertilizer costs, and a literature review to identify region-specific inputs. Our findings suggest that farmers who reuse fresh excreta are 1.24 (95% CI: 1.13-1.37, p-value<0.001) times more likely to be infected with any STH than those who do not handle excreta or who compost appropriately, and that risk varies by STH type (Ascaris lumbricoides RR = 1.17, 95% CI = 0.87-1.58, p-value = 0.29; Hookworm RR = 1.02, 95% CI = 0.50-2.06, p-value = 0.96; Trichuris trichiura RR = 1.38, 95% CI = 0.79-2.42, p-value = 0.26). Average cost-savings were highest for farmers using fresh excreta (847,000 VND) followed by those who composted for 6 months as recommended by the WHO (312,000 VND) and those who composted for a shorter time (5 months) with lime supplementation (37,000 VND/yr); however, this study did not assess healthcare costs of treating acute or chronic STH infections in the target group. Our study provides evidence that farmers in the Red River Delta are able to use a renewable and locally available resource to their economic advantage, while minimizing the risk of STH infection.


Asunto(s)
Agricultura/métodos , Ascariasis/transmisión , Heces/parasitología , Infecciones por Uncinaria/transmisión , Suelo/parasitología , Tricuriasis/transmisión , Ancylostomatoidea/aislamiento & purificación , Animales , Ascariasis/parasitología , Ascaris lumbricoides/aislamiento & purificación , Líquidos Corporales/parasitología , Análisis Costo-Beneficio , Infecciones por Uncinaria/parasitología , Humanos , Modelos Lineales , Tricuriasis/parasitología , Trichuris/aislamiento & purificación , Vietnam
13.
Parasit Vectors ; 10(1): 321, 2017 Jun 30.
Artículo en Inglés | MEDLINE | ID: mdl-28666452

RESUMEN

BACKGROUND: There is an increased focus on whether mass drug administration (MDA) programmes alone can interrupt the transmission of soil-transmitted helminths (STH). Mathematical models can be used to model these interventions and are increasingly being implemented to inform investigators about expected trial outcome and the choice of optimum study design. One key factor is the choice of threshold for detecting elimination. However, there are currently no thresholds defined for STH regarding breaking transmission. METHODS: We develop a simulation of an elimination study, based on the DeWorm3 project, using an individual-based stochastic disease transmission model in conjunction with models of MDA, sampling, diagnostics and the construction of study clusters. The simulation is then used to analyse the relationship between the study end-point elimination threshold and whether elimination is achieved in the long term within the model. We analyse the quality of a range of statistics in terms of the positive predictive values (PPV) and how they depend on a range of covariates, including threshold values, baseline prevalence, measurement time point and how clusters are constructed. RESULTS: End-point infection prevalence performs well in discriminating between villages that achieve interruption of transmission and those that do not, although the quality of the threshold is sensitive to baseline prevalence and threshold value. Optimal post-treatment prevalence threshold value for determining elimination is in the range 2% or less when the baseline prevalence range is broad. For multiple clusters of communities, both the probability of elimination and the ability of thresholds to detect it are strongly dependent on the size of the cluster and the size distribution of the constituent communities. Number of communities in a cluster is a key indicator of probability of elimination and PPV. Extending the time, post-study endpoint, at which the threshold statistic is measured improves PPV value in discriminating between eliminating clusters and those that bounce back. CONCLUSIONS: The probability of elimination and PPV are very sensitive to baseline prevalence for individual communities. However, most studies and programmes are constructed on the basis of clusters. Since elimination occurs within smaller population sub-units, the construction of clusters introduces new sensitivities for elimination threshold values to cluster size and the underlying population structure. Study simulation offers an opportunity to investigate key sources of sensitivity for elimination studies and programme designs in advance and to tailor interventions to prevailing local or national conditions.


Asunto(s)
Ancylostomatoidea/efectos de los fármacos , Erradicación de la Enfermedad , Infecciones por Uncinaria/prevención & control , Modelos Teóricos , Animales , Antihelmínticos/administración & dosificación , Simulación por Computador , Femenino , Infecciones por Uncinaria/tratamiento farmacológico , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/transmisión , Humanos , Masculino , Prevalencia , Suelo/parasitología , Procesos Estocásticos
14.
Parasit Vectors ; 10(1): 254, 2017 May 23.
Artículo en Inglés | MEDLINE | ID: mdl-28535806

RESUMEN

BACKGROUND: Current WHO guidelines for soil-transmitted helminth (STH) control focus on mass drug administration (MDA) targeting preschool-aged (pre-SAC) and school-aged children (SAC), with the goal of eliminating STH as a public health problem amongst children. Recently, attention and funding has turned towards the question whether MDA alone can result in the interruption of transmission for STH. The lymphatic filariasis (LF) elimination programme, have been successful in reaching whole communities. There is the possibility of building upon the infrastructure created for these LF-programmes to enhance the control of STH. Using hookworm as an example, we explore what further MDA coverage might be required to induce interruption of transmission for hookworm in the wake of a successful LF programme. RESULTS: Analyses based on the model of STH transmission and MDA impact predict the effects of previous LF control by MDA over five years, on a defined baseline prevalence of STH in an area with a defined transmission intensity (the basic reproductive number R0). If the LF MDA programme achieved a high coverage (70, 70 and 60% for pre-SAC, SAC and adults, respectively) we expect that in communities with a hookworm prevalence of 15%, after 5 years of LF control, the intrinsic R0 value in that setting is 2.47. By contrast, if lower LF coverages were achieved (40, 40 and 30% for pre-SAC, SAC and adults, respectively), with the same prevalence of 15% at baseline (after 5 years of LF MDA), the intrinsic hookworm R0 value is predicted to be 1.67. The intrinsic R0 value has a large effect on the expected successes of follow-up STH programmes post LF MDA. Consequently, the outcomes of identical programmes may differ between these communities. CONCLUSION: To design the optimal MDA intervention to eliminate STH infections, it is vital to have information on historical MDA programmes and baseline prevalence to estimate the intrinsic transmission intensity for the defined setting (R0). The baseline prevalence alone is not sufficient to inform policy for the control of STH, post cessation of LF MDA, since this will be highly dependent on the intensity and effectiveness of past programmes and the intrinsic transmission intensity of the dominant STH species in any given setting.


Asunto(s)
Ancylostomatoidea/efectos de los fármacos , Antihelmínticos/administración & dosificación , Filariasis Linfática/tratamiento farmacológico , Ancylostomatoidea/fisiología , Animales , Filariasis Linfática/parasitología , Filariasis Linfática/transmisión , Femenino , Infecciones por Uncinaria/tratamiento farmacológico , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/transmisión , Humanos , Masculino , Administración Masiva de Medicamentos
15.
Epidemics ; 18: 38-47, 2017 03.
Artículo en Inglés | MEDLINE | ID: mdl-28279454

RESUMEN

The predictions of two mathematical models of the transmission dynamics of Ascaris lumbricoides and hookworm infection and the impact of mass drug administration (MDA) are compared, using data from India. One model has an age structured partial differential equation (PDE) deterministic framework for the distribution of parasite numbers per host and sexual mating. The second model is an individual-based stochastic model. Baseline data acquired prior to treatment are used to estimate key transmission parameters, and forward projections are made, given the known MDA population coverage. Predictions are compared with observed post-treatment epidemiological patterns. The two models could equally well predict the short-term impact of deworming on A. lumbricoides and hookworm infection levels, despite being fitted to different subsets and/or summary statistics of the data. As such, the outcomes give confidence in their use as aids to policy formulation for the use of PCT to control A. lumbricoides and hookworm infection. The models further largely agree in a qualitative sense on the added benefit of semi-annual vs. annual deworming and targeting of the entire population vs. only children, as well as the potential for interruption of transmission. Further, this study also illustrates that long-term predictions are sensitive to modelling assumptions about which age groups contribute most to transmission, which depends on human demography and age-patterns in exposure and contribution to the environmental reservoir of infection, the latter being notoriously difficult to empirically quantify.


Asunto(s)
Antihelmínticos/uso terapéutico , Ascariasis/prevención & control , Infecciones por Uncinaria/prevención & control , Administración Masiva de Medicamentos , Modelos Teóricos , Animales , Ascariasis/epidemiología , Ascariasis/transmisión , Ascaris lumbricoides , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/transmisión , Humanos , India , Reproducibilidad de los Resultados
16.
Parasit Vectors ; 10(1): 91, 2017 02 17.
Artículo en Inglés | MEDLINE | ID: mdl-28212668

RESUMEN

BACKGROUND: Globally, in 2010, approximately 1.5 billion people were infected with at least one species of soil-transmitted helminth (STH), Ascaris lumbricoides, Trichuris trichiura, hookworm (Ancylostoma duodenale and Necator americanus). Infection occurs through ingestion or contact (hookworm) with eggs or larvae in the environment from fecal contamination. To control these infections, the World Health Organization recommends periodic mass treatment of at-risk populations with deworming drugs. Prevention of these infections typically relies on improved excreta containment and disposal. Most evidence of the relationship between sanitation and STH has focused on household-level access or usage, rather than community-level sanitation usage. We examined the association between the proportion of households in a community with latrines in use and prevalence of STH infections among school-aged children. METHODS: Data on STH prevalence and household latrine usage were obtained during four population-based, cross-sectional surveys conducted between 2011 and 2014 in Amhara, Ethiopia. Multilevel regression was used to estimate the association between the proportion of households in the community with latrines in use and presence of STH infection, indicated by > 0 eggs in stool samples from children 6-15 years old. RESULTS: Prevalence of STH infection was estimated as 22% (95% CI: 20-24%), 14% (95% CI: 13-16%), and 4% (95% CI: 4-5%) for hookworm, A. lumbricoides, and T. trichiura, respectively. Adjusting for individual, household, and community characteristics, hookworm prevalence was not associated with community sanitation usage. Trichuris trichuria prevalence was higher in communities with sanitation usage ≥ 60% versus sanitation usage < 20%. Association of community sanitation usage with A. lumbricoides prevalence depended on household sanitation. Community sanitation usage was not associated with A. lumbricoides prevalence among households with latrines in use. Among households without latrines in use, A. lumbricoides prevalence was higher comparing communities with sanitation usage ≥ 60% versus < 20%. Households with a latrine in use had lower prevalence of A. lumbricoides compared to households without latrines in use only in communities where sanitation usage was ≥ 80%. CONCLUSIONS: We found no evidence of a protective association between community sanitation usage and STH infection. The relationship between STH infection and community sanitation usage may be complex and requires further study.


Asunto(s)
Ascariasis/epidemiología , Infecciones por Uncinaria/epidemiología , Saneamiento , Suelo/parasitología , Cuartos de Baño , Tricuriasis/epidemiología , Tricuriasis/transmisión , Adolescente , Ancylostomatoidea/aislamiento & purificación , Animales , Ascariasis/parasitología , Ascariasis/transmisión , Ascaris lumbricoides/aislamiento & purificación , Niño , Estudios Transversales , Etiopía/epidemiología , Composición Familiar , Heces/parasitología , Femenino , Helmintos/aislamiento & purificación , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/transmisión , Humanos , Masculino , Prevalencia , Encuestas y Cuestionarios , Tricuriasis/parasitología , Trichuris/aislamiento & purificación
17.
Parasitology ; 144(5): 669-679, 2017 04.
Artículo en Inglés | MEDLINE | ID: mdl-28103964

RESUMEN

Soil-transmitted helminth (STH) infections are widely distributed in tropical and subtropical areas, including Brazil. We performed a nationwide population-based study including all deaths in Brazil from 2000 to 2011, in which STHs (ascariasis, trichuriasis and/or hookworm infection) were mentioned on death certificates, either as underlying or as associated causes of death. Epidemiological characteristics, time trends and spatial analysis of STH-related mortality were analysed. STHs was identified on 853/12 491 280 death certificates: 827 (97·0%) deaths related to ascariasis, 25 (2·9%) to hookworm infections, and 1 (0·1%) to trichuriasis. The average annual age-adjusted mortality rate was 0·34/1 000 000 inhabitants (95% confidence interval: 0·27-0·44). Females, children <10 years of age, indigenous ethnic groups and residents in the Northeast region had highest STH-related mortality rates. Nationwide mortality decreased significantly over time (annual percent change: -5·7%; 95% CI: -6·9 to -4·4), with regional differences. We identified spatial high-risk clusters for STH-related mortality mainly in the North, Northeast and South regions. Diseases of the digestive system and infectious/parasitic diseases were the most commonly associated causes of death mentioned in the STH-related deaths. Despite decreasing mortality in Brazil, a considerable number of deaths is caused by STHs, with ascariasis responsible for the vast majority. There were marked regional differences, affecting mainly children and vulnerable populations.


Asunto(s)
Helmintiasis/mortalidad , Suelo/parasitología , Adolescente , Adulto , Anciano , Ascariasis/epidemiología , Ascariasis/mortalidad , Ascariasis/parasitología , Ascariasis/transmisión , Brasil/epidemiología , Niño , Preescolar , Femenino , Geografía , Helmintiasis/epidemiología , Helmintiasis/parasitología , Helmintiasis/transmisión , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/mortalidad , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/transmisión , Humanos , Lactante , Masculino , Persona de Mediana Edad , Enfermedades Desatendidas , Análisis Espacial , Tricuriasis/epidemiología , Tricuriasis/mortalidad , Tricuriasis/parasitología , Tricuriasis/transmisión , Adulto Joven
18.
PLoS Negl Trop Dis ; 10(12): e0005161, 2016 12.
Artículo en Inglés | MEDLINE | ID: mdl-27923048

RESUMEN

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.


Asunto(s)
Riego Agrícola , Ascariasis/etiología , Ascariasis/transmisión , Agricultores , Heces/parasitología , Infecciones por Uncinaria/etiología , Infecciones por Uncinaria/transmisión , Suelo/parasitología , Aguas Residuales/parasitología , Agricultura/métodos , Agricultura/normas , Ancylostomatoidea/aislamiento & purificación , Animales , Ascariasis/epidemiología , Ascariasis/parasitología , Ascaris/aislamiento & purificación , Productos Agrícolas , Familia , Ghana/epidemiología , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/parasitología , Humanos , Oportunidad Relativa , Estaciones del Año , Verduras
19.
Folia Primatol (Basel) ; 87(3): 168-179, 2016.
Artículo en Inglés | MEDLINE | ID: mdl-27682258

RESUMEN

There are many known benefits of social grooming among primates, including maintenance of social relationships, removal of ectoparasites, and improved physiological condition. Recently, however, researchers have noted that social grooming and social contact may also present a significant cost by facilitating transmission of some parasites and pathogens. We investigated whether the number of social grooming partners varied based on infection status for gastrointestinal parasites. We used focal animal sampling and continuous recording to collect data on the number of grooming partners for known individual vervet monkeys (Chlorocebus aethiops). We collected non-invasive faecal samples and examined them using faecal flotation, faecal sedimentation, and immunofluorescence microscopy. We detected 6 parasites: Trichuris sp. (92%), hookworm (71%), spirurids (68%), Oesophagostomum sp. (84%), Strongyloides sp. (24%), and Entamoeba coli (92%). The number of grooming partners varied significantly based on infection with hookworm and sex. No significant relationships were detected for other parasites. Associations between host behavioural variation and some parasite taxa (specifically Trichuris, Oesophagostomum, and Entamoeba spp.) were impossible to explore due to an extremely high prevalence among hosts. This is the first report that we are aware of that has detected an association between social grooming behaviours and infection with hookworm.


Asunto(s)
Chlorocebus aethiops/fisiología , Chlorocebus aethiops/parasitología , Aseo Animal , Infecciones por Uncinaria/veterinaria , Enfermedades de los Monos/parasitología , Animales , Entamoeba/aislamiento & purificación , Entamebiasis/transmisión , Entamebiasis/veterinaria , Heces/parasitología , Femenino , Infecciones por Uncinaria/parasitología , Infecciones por Uncinaria/transmisión , Masculino , Enfermedades de los Monos/transmisión , Nematodos/aislamiento & purificación , Infecciones por Nematodos/transmisión , Infecciones por Nematodos/veterinaria , Conducta Social , Sudáfrica
20.
Parasitol Res ; 115(7): 2817-23, 2016 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-27053130

RESUMEN

Hookworm infection is still prevalent in southern Thailand despite control measures. Hookworm eggs submerged for an extended period under water from rainfall or in latrines may not survive, but they may recover their ability to develop into infective larvae when exposed to atmospheric air. This study examined the survival of the hookworm eggs in stool suspension and the restoration of development capability after prolonged storage. In stool mass, eggs developed normally and yielded infective filariform larvae (FL) in 7 days. On the contrary, in 1:10 stool suspension, hookworm eggs were found to remain at the 4-8 cell stage; degenerated eggs were observed after 15 days of storage, and the number of degenerated eggs reached 80 % on day 30. Aeration of the suspension, or transferring to a Petri dish or agar plate, restored the capacity of eggs stored for up to 15 days to develop into FL; thereafter, the capacity declined sharply. Retardation of egg development under water or in stool suspension may be due to a lack of atmospheric air. Use of "night soil" from latrines as fertilizer may be one factor in maintaining hookworm transmission, as worm eggs can undergo normal development upon exposure to atmospheric air.


Asunto(s)
Ancylostomatoidea/crecimiento & desarrollo , Heces/parasitología , Infecciones por Uncinaria/parasitología , Necator/crecimiento & desarrollo , Necatoriasis/parasitología , Preservación Biológica/métodos , Ancylostomatoidea/patogenicidad , Animales , Femenino , Infecciones por Uncinaria/epidemiología , Infecciones por Uncinaria/transmisión , Humanos , Larva , Necator/patogenicidad , Necatoriasis/epidemiología , Necatoriasis/transmisión , Óvulo/crecimiento & desarrollo , Preservación Biológica/normas , Prevalencia , Suelo/parasitología , Suspensiones , Tailandia/epidemiología , Agua/parasitología
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