Module 1 Background

TAS

Global Programme to Eliminate Lymphatic Filariasis (GPELF)

Training in monitoring and epidemiological assessment of mass drug administration for eliminating lymphatic filariasis

Module 1 Background

Module 1 Background

Learning objectives

By the end of this module, you should be able to answer the questions:

1. What is lymphatic filariasis (LF)?

2. What is the Global Programme to Eliminate Lymphatic Filariasis (GPELF)?

3. What is a transmission assessment survey (TAS)?

4. How does the national programme report to the GPELF?

Slide 2

Module 1 Background

Overview What is LF? The GPELF Programme steps for interrupting transmission

Mapping

Mass drug administration (MDA)

Monitoring and evaluation during MDA

TAS

Post-MDA surveillance

Reporting to the GPELF

Slide 3

Module 1 Background

What is lymphatic filariasis (LF)?

W. bancrofti B. malayi B. timori

Caused by three species of parasitic worm: Wuchereria bancrofti, Brugia malayi and B. timori

Transmitted to humans by mosquitoes

Slide 4

Source: www.dpd.cdc.gov/dpdx

Module 1 BackgroundSlide 5

The commonest clinical manifestations are lymphoedema, which affects 15 million people, and scrotal hydrocoele, which affects 25 million men

Lymphoedema Hydrocoele

What is lymphatic filariasis (LF)?

Module 1 BackgroundSlide 6

Endemic in 73 countries; 1.39 billion people at risk of infection (2011)

What is lymphatic filariasis (LF)?

Module 1 Background

Global Programme to Eliminate Lymphatic Filariasis (GPELF)

Slide 7

In 1997, the World Health Assembly resolved to eliminate lymphatic filariasis as a public health problem (WHA resolution 50.29).

In 2000, the GPELF was launched by WHO

Aim 1. Stop the spread of infection: interrupt transmission by MDA

Aim 2. Reduce the suffering caused by the disease: morbidity management and disability prevention

Goal: Global elimination by 2020

Module 1 Background

GPELF works in partnership with: the ministries of health of countries endemic for LF,

which are responsible for national programmes donors pharmeceutical and diagnostics companies academic and research institutions nongovernmental organizations WHO

Slide 8

Global Programme to Eliminate Lymphatic Filariasis (GPELF)

Module 1 Background

Programmatic steps for interrupting transmission

Slide 9

1. Mapping the geographical distribution of the disease.

2. MDA for 5 years or more to reduce the number of parasites in blood to levels that will prevent mosquito vectors from transmitting infection.

3. Post-MDA surveillance after MDA is discontinued.

4. Verification of elimination of transmission.

Mapping MDA Post-MDA surveillance Verification

Module 1 Background

Mapping

Slide 10

Mapping: to determine whether active transmission is occurring and whether MDA is necessary.

1. Define the implementation unit (IU) for MDA. 2. Conduct mapping by:

reviewing existing information conducting mapping surveys

Measure antigenaemia by immunochromatographic tests (ICT) or measure microfilaria in blood films from older school-aged or adult populations. If the prevalence in this population is ≥ 1%, classify the IU as endemic.

Module 1 Background

MDA

Slide 11

GPELF recommends mass administration: of a combination of medicines:

diethylcarbamazine (DEC) + albendazole (in countries not co-endemic for onchocerciasis)

ivermectin + albendazole (in countries co-endemic for onchocerciasis) of single-dose treatment for at least 5 years to all eligible individuals in the entire endemic area

The objective is to achieve:• a reduction in the density of microfilariae circulating in the blood of

infected individuals and • a reduction in the prevalence of infection in the entire community

to levels at which it is assumed that microfilariae can no longer be transmitted by mosquito vectors to new human hosts.

Module 1 Background

Monitoring and evaluation during MDA

Slide 12

Mapping

Mf or Ag≥1% TAS

Surveillance

Baseline

MDA

Follow-up[Eligibility]

Mid-term (optional)

Yes

M&E

Pass

Fail

Prevalence of Mf or Ag can be used in mapping. Coverage is monitored at each MDA round to determine whether the goal of at least 65%

coverage of the total population was met. After at least five rounds of effective MDA, the impact is evaluated at sentinel and spot-

check sites. If all the eligibility criteria are met, a transmission assessment survey (TAS) is

conducted before deciding to stop MDA. TAS is repeated twice during post-MDA surveillance phase.

Module 1 Background

Transmission assessment Survey (TAS)

Slide 13

Technical aspect Guidance

Geographical area Evaluation Unit (EU)

When survey should be conducted

• When all the eligibility criteria are met • At least 6 months after the last round of MDA

Target population Children aged 6–7 years

Diagnostic tests W. bancrofti areas: ICTBrugia spp. areas: Brugia Rapid™

Survey design Cluster sampling or systematic sampling in schools or the community, or a census

A TAS is the basis for a decision to move from MDA to post-MDA surveillance.

A TAS is a simplified version of the ‘stopping-MDA survey’ protocol.

Module 1 Background

Limitations of previous guideline

Slide 14

Mapping

Mf or Ag≥1%Stopping

MDA survey

Surveillance

Baseline

MDA

Follow-up[Eligibility]

Mid-term (optional)

Yes

M&E

Pass

Fail

An additional 5–10 sentinel or spot-check tests were required per IU. Antigenaemia surveys of 2–4-year-old children were not informative in most

countries. Lot quality assurance sampling surveys were difficult to implement (e.g. too

many schools to visit per IU to test 3000 children). The 1 in 3000 threshold was too conservative.

< 1% Mf< 0.1% ICTLQAS 3000

children

Difficult to implement; extremely conservative threshold.

Module 1 Background

Post-MDA surveillance

Slide 15

Mapping

Mf or Ag≥1% TAS

Surveillance

Baseline

MDA

Follow-up[Eligibility]

Mid-term (optional)

Yes

M&E

Pass

Fail

A TAS is not only an important decision-making step for stopping MDA but is also one of the methods of post-MDA surveillance recommended for detecting whether recrudescence of transmission has occurred.

A survey should be repeated at least twice after MDA is stopped, at an interval of 2–3 years, to ensure that recrudescence has not occurred and therefore transmission can be considered interrupted.

Module 1 Background

Reporting from a national programme to the GPELF

Slide 16

Communicate plan to WHO/RPRG

RPRG endorses plan

TAS

Submit report to WHO/RPRG

RPRG endorses results

VerificationPost-MDA surveillance

Submit dossier to

WHO/RPRG

RPRG endorses dossier and recommends it to

STAG-NTD (via its M&E Working Group)

STAG-NTD endorses the

claim

Begin planning TAS

(Proposed framework)