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Active/passive
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Passive
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Active
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Active
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Active
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Year initiated
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1950s (1989 for schistosomiasis)
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1990
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1950s
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1989
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Reporting unit
|
Individuals in hospitals
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Sentinel village
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Village
|
Village
|
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Coverage
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All hospitals
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Nine sentinel villages
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All villages in endemic counties
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1% of villages in endemic provinces
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|
Time frame
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Real-time, within 24 hours of patient diagnosis
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Yearly
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All villages sampled over ~3 years, reporting occurs at completion of each village’s survey
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Periodic every 6-9 years: 1989, 1995, 2004
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|
Purpose
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Aid understanding of disease patterns; provide evidence for policy-making
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Longitudinally and objectively monitor how the schistosome-endemic situation changes over time
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Evaluate control measures
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Clarify the endemic status of schistosomiasis as established by the previous national survey
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|
Information collected
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Individual cases (demographics, patient residence, diagnosis, treatment and hospital)
|
Snail habitat, human infection prevalence and intensity, bovine infection prevalence
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Snail habitat, human infection prevalence
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Human infection prevalence and intensity, bovine infection prevalence, snail habitat
|
|
Diagnostics
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Clinical and laboratory
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IHA screen then Kato-Katz and miracidium hatch
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IHA screen then Kato-Katz
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ELISA screen then Kato-Katz
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|
Major changes
|
2004: Replaced paper-based monthly or yearly reporting with internet-based real-time reporting system
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2011: Added Miracidium Hatch Test to diagnostic procedure
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2011: Replaced yearly reporting with internet-based parasitic disease reporting that occurs after completion of each village survey
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2004: Inclusion criteria expanded to include areas with prevalence >0.5% from previous criterion of >1%
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|
Strengths
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Inexpensive, Algorithms can be created to automatically detect outbreaks of emerging or reemerging disease
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Provides longitudinal measures of disease prevalence and intensity
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Provides greatest coverage since it samples all endemic villages in the province
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Provides a nationwide estimate of schistosomiasis prevalence
|
|
Limitations
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Underreporting of chronic cases; potential underreporting of acute cases due to political pressure; potential information bias associated with variable clinical and diagnostic capacities of reporting sites; non-response bias associated with reporter fatigue
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Sampling occurs at limited sites (20 in 1989, 80 in 2005); longitudinal follow-up over decades can yield non-response bias resulting from participation and reporter fatigue; potential selection bias associated with the choice of villages to sample longitudinally
|
Variable clinical and diagnostic capabilities can lead to information bias; potential selection bias associated with choice of survey sites, since those in charge of surveillance are also in charge of control efforts; potential reporting bias as funding can be tied to disease control success; potential non-response bias resulting from participation fatigue and temporary rural-to-urban migration
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Occurs rarely and survey methods change, making it difficult to assess temporal patterns; only includes 1% of endemic villages in each province
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