Transcript Module 2 Eligibility for a TAS

Global Programme to Eliminate Lymphatic Filariasis (GPELF)
Training in monitoring and epidemiological assessment of mass
drug administration for eliminating lymphatic filariasis
TAS
Module 2 Eligibility for a TAS
Module 2 Eligibility for a TAS
Learning objectives
By the end of this module, you should understand that the
eligibility of an IU for a TAS is assessed on the basis of:
1. epidemiological drug coverage (programme coverage)
2. prevalence of infection at sentinel sites
3. prevalence of infection at spot-check sites
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Module 2 Eligibility for a TAS
Overview

Eligibility criteria for a TAS

Epidemiological drug coverage (programme coverage)

Sentinel and spot-check surveys

Confirming eligibility
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Module 2 Eligibility for a TAS
Eligibility criteria for a TAS
In order for a national programme to start planning a
TAS, the following criteria must be met in each IU:
 At least five rounds of MDA were completed.
 ≥ 65% epidemiological drug coverage achieved at
each round.
 Sentinel site: prevalence of Mf < 1% or prevalence of
Ag < 2% after last effective round at all sites
 Spot-check site: prevalence of Mf < 1% or prevalence
of Ag < 2% after last effective round at all sites
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Module 2 Eligibility for a TAS
Epidemiological drug coverage
 Epidemiological drug coverage (programme coverage) is defined
as "the proportion of individuals in an IU who actually ingested the
medicines"
=
No. people reported to have ingested the medicines
Total population in IU
X 100
 To reduce the prevalence of Mf in infected individuals to the
threshold below which transmission is assumed to be no longer
sustainable, at least 65% of the total population in each IU must
ingest the medicines in at least five rounds of MDA.
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Module 2 Eligibility for a TAS
Sentinel and spot-check surveys
 Blood surveys at sentinel sites are used to establish the
baseline infection level and to monitor the impact of MDA
on infection prevalence periodically.
 Once a sentinel site is selected, it should continue to serve as the
sentinel site throughout the programme.
 Blood surveys at spot-check sites are used to confirm
that the results of sentinel surveys represent the infection
level in the entire IU.
 At least one spot-check site is selected for each sentinel site.
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Module 2 Eligibility for a TAS
How many sentinel and spot-check sites
are needed in each implementation unit?
 At least one sentinel site per 1 million people
 At least one sentinel site in each IU; more sites may be
selected when resources allow
 Smaller IUs may be served by one sentinel site.
 Combined IUs should be contiguous and have similar
epidemiological characteristics.
 Combined IUs should have conducted MDA at the same time.
 The advice of WHO and the RPRG may be required.
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Module 2 Eligibility for a TAS
Characteristics of sentinel and
spot-check sites
 The population should be at least 500 people (to collect
samples from at least 300 people aged > 5 years)
 Should be in an area of high transmission: high disease
or parasite prevalence or vector abundance
 or an area where difficulty in achieving high drug coverage is
anticipated
 No prior MDA for onchocerciasis
 A stable population
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Module 2 Eligibility for a TAS
When should surveys be conducted?
 Baseline assessment: before first MDA
 Mid-term evaluation: at least 6 months after third MDA
(optional)
 Follow-up survey: at least 6 months after fifth effective MDA
Round of MDA
1
2
3
4
5
Mapping
Mf and/or Ag
prevalence
(baseline)
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Module 2 Eligibility for a TAS
TAS
Mf and/or Ag
prevalence
(optional)
Mf and/or Ag
prevalence
(follow-up)
When should surveys be conducted?
 Target population
 Convenience sample of at least 300 people
 All members of the population in all age groups > 5 years
(including pregnant women)
 When the population is too large, a part can be chosen.
 Diagnostic test
 Blood film for prevalence of Mf
 Immunochromatographic test (ICT) for Ag rate if resources allow
(in W. bancrofti areas)
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Module 2 Eligibility for a TAS
Confirming eligibility to conduct a TAS
 Before assessing the eligibility of
an IU, programme managers
should compile all necessary
records and complete the ‘INTRO’
and ‘ELIGIBILITY’ worksheets of
the TAS Eligibility and Reporting
Form.
 The form helps in deciding whether
the time is appropriate to conduct a
TAS.
 The form should be reviewed by
the RPRG before the survey is
planned.
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Module 2 Eligibility for a TAS