7 results found
Werkman M, Wright JE, Truscott JE, et al., 2018, Testing for soil-transmitted helminth transmission elimination: Analysing the impact of the sensitivity of different diagnostic tools., PLoS Negl Trop Dis, Vol: 12
In recent years, an increased focus has been placed upon the possibility of the elimination of soil-transmitted helminth (STH) transmission using various interventions including mass drug administration. The primary diagnostic tool recommended by the WHO is the detection of STH eggs in stool using the Kato-Katz (KK) method. However, detecting infected individuals using this method becomes increasingly difficult as the intensity of infection decreases. Newer techniques, such as qPCR, have been shown to have greater sensitivity than KK, especially at low prevalence. However, the impact of using qPCR on elimination thresholds is yet to be investigated. In this paper, we aim to quantify how the sensitivity of these two diagnostic tools affects the optimal prevalence threshold at which to declare the interruption of transmission with a defined level of confidence. A stochastic, individual-based STH transmission model was used in this study to simulate the transmission dynamics of Ascaris and hookworm. Data from a Kenyan deworming study were used to parameterize the diagnostic model which was based on egg detection probabilities. The positive and negative predictive values (PPV and NPV) were calculated to assess the quality of any given threshold, with the optimal threshold value taken to be that at which both were maximised. The threshold prevalence of infection values for declaring elimination of Ascaris transmission were 6% and 12% for KK and qPCR respectively. For hookworm, these threshold values are lower at 0.5% and 2% respectively. Diagnostic tests with greater sensitivity are becoming increasingly important as we approach the elimination of STH transmission in some regions of the world. For declaring the elimination of transmission, using qPCR to diagnose STH infection results in the definition of a higher prevalence, than when KK is used.
Wright JE, Werkman M, Dunn JC, et al., 2018, Current epidemiological evidence for predisposition to high or low intensity human helminth infection: a systematic review., Parasit Vectors, Vol: 11
BACKGROUND: The human helminth infections include ascariasis, trichuriasis, hookworm infections, schistosomiasis, lymphatic filariasis (LF) and onchocerciasis. It is estimated that almost 2 billion people worldwide are infected with helminths. Whilst the WHO treatment guidelines for helminth infections are mostly aimed at controlling morbidity, there has been a recent shift with some countries moving towards goals of disease elimination through mass drug administration, especially for LF and onchocerciasis. However, as prevalence is driven lower, treating entire populations may no longer be the most efficient or cost-effective strategy. Instead, it may be beneficial to identify individuals or demographic groups who are persistently infected, often termed as being "predisposed" to infection, and target treatment at them. METHODS: The authors searched Embase, MEDLINE, Global Health, and Web of Science for all English language, human-based papers investigating predisposition to helminth infections published up to October 31st, 2017. The varying definitions used to describe predisposition, and the statistical tests used to determine its presence, are summarised. Evidence for predisposition is presented, stratified by helminth species, and risk factors for predisposition to infection are identified and discussed. RESULTS: In total, 43 papers were identified, summarising results from 34 different studies in 23 countries. Consistent evidence of predisposition to infection with certain species of human helminth was identified. Children were regularly found to experience greater predisposition to Ascaris lumbricoides, Schistosoma mansoni and S. haematobium than adults. Females were found to be more predisposed to A. lumbricoides infection than were males. Household clustering of infection was identified for A. lumbricoides, T. trichiura and S. japonicum. Ascaris lumbricoides and T. trichiura also showed evidence of familial predisposition. Whilst strong evidence fo
Toor J, Truscott JE, Alsallaq R, et al., 2017, ARE WE ON OUR WAY TO ACHIEVING THE 2020 GOALS FOR SCHISTOSOMIASIS MORBIDITY CONTROL USING CURRENT WHO GUIDELINES?, 66th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 394-395, ISSN: 0002-9637
Truscott JE, Werkman M, Wright JE, et al., 2017, Identifying optimal threshold statistics for elimination of hookworm using a stochastic simulation model, PARASITES & VECTORS, Vol: 10, ISSN: 1756-3305
Werkman M, Truscott JE, Toor J, et al., 2017, The past matters: estimating intrinsic hookworm transmission intensity in areas with past mass drug administration to control lymphatic filariasis, PARASITES & VECTORS, Vol: 10, ISSN: 1756-3305
Werkman M, Truscott JE, Wright JE, et al., 2017, ARE WE ON THE RIGHT TRACK? STOPPING CRITERIA FOR ENDING SOIL-TRANSMITTED HELMINTHS RANDOMIZED CLINICAL TRIALS, 66th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 560-560, ISSN: 0002-9637
Wright JE, Truscott J, Werkman M, et al., 2017, ASSESSING BETWEEN-VILLAGE HETEROGENEITY OF HOOKWORM TRANSMISSION IN A LOW-INTENSITY SETTING, 66th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTMH), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 375-376, ISSN: 0002-9637
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