The elimination of an infectious disease is a once in a career, nay lifetime, happening for most medical researchers. Happily, there is one success story in the making right here in The Gambia: trachoma, the leading infectious cause of blindness worldwide is on its way to becoming history. The Partnership for the Rapid Elimination of Trachoma (PRET) has been instrumental in this putsch and here we talk to Mr Ansumana Sillah (National Eye Care Programme), Drs Emma Harding-Esch and Sarah Burr (MRC/LSHTM) about PRET.
What is PRET?
EHE: PRET is a cluster randomised control trial taking place in three countries: The Gambia, Tanzania and Niger. It aims to answer two main questions: one is the WHO recommendation that districts where the prevalence of follicular trachoma is 10% or more in children aged 1 to 9 years should be mass treated with azithromycin, an antibiotic donated by Pfi zer via the International Trachoma Initiative. They recommend that treatment should be done annually for at least three years. After three years you re-assess the prevalence then decide whether or not you need to continue mass treatment.

We are looking at whether you actually need to treat every three years or whether less frequent treatment is possible. We have randomised enumeration areas (EAs) of 600-800 people (from clusters of smaller settlements to larger villages). We randomly selected 48 EAs to be included in the whole of the PRET trial. Twenty four of these are randomised to receive treatment every year for three years; 24 belong to a graduation rule, whereby treatment will be ceased if there is no evidence of follicular trachoma or ocular Chlamydia trachomatis infection in the follow up before the next round of mass treatment. In the Gambian arm of PRET, because we had no infection at six months, we actually didn’t do the second round of mass treatment in the 24 graduation arm EAs. And we haven’t had infection at 18 months, so we are not doing treatment again this time at the third round for those 24 EAs.

The other arm of the study is that the WHO recommends that mass treatment coverage should be 80% or more. But again like the 10% trachoma prevalence benchmark, this is based on expert opinion with no real scientifi c evidence behind it. The PRET trial is providing the evidence to support the WHO recommendations. We are comparing 80% treatment coverage with an attempt at obtaining 90%. In The Gambia we have interpreted 80% coverage as being equivalent to what the normal National Eye Care Programme (NECP) would do; 90% is that we go back an extra day and try and treat the people we didn’t catch the fi rst time. Invariably this means that some areas allocated to just 80-89% treatment coverage might actually get 90% because the NECP does such a fantastic job anyway; and 90% treatment coverage might actually be less, because of participants travelling during the time of treatment, for example. So there’s a difference between intention to treat and actual treatment, but we’ve actually managed to do quite well.

Martin and Sarah, what are your roles in PRET?
SB: I came on board to look after all the diagnostic data. We have two people in the lab processing a large volume of samples: in a year we are collecting 12,000.
There’s a lot of quality control and going over the results.

Martin Holland: I generally oversee the project. Robin Bailey (LSHTM) was the Gambia PI on the proposal which I presented to the SCC. The award in terms of what came to LSHTM was a three-way split between Professors David Mabey, Robin Bailey and myself. The ‘real’ PI is Professor Sheila West who is based at Johns Hopkins University.

How has PRET contributed to capacity development?
AS: Our staff were fi rst trained in 2008 in Ethiopia on how to do fi eld work and take samples. We came back and adapted what we had learnt to our situation here. Our staff also received additional training from the MRC. This capacity building has not just been about skills but also in terms of equipment. Our data entry room at NECP is now well equipped with two computers and internet connectivity, so the data entry people can have instant communication with myself and others wherever they are.

And this goes beyond the NECP. Capitalising on the research expertise we have here in the PRET study, a number of countries have benefi ted. Within the Health for Peace Initiative, students have come from all over Africa to receive training at the Regional Opthalmology Training Centre here in The Gambia. Emma has trained community ophthalmic nurses and has also run short courses.

EHE: I organise a week’s training in epidemiology, statistics and operational research at the Regional Opthalmology Training Centre. It’s an intensive week and all the students do really well - they get taught in a week what I was taught in a term in my MSc at the London School! The fi rst day is theoretical epidemiology. The second day they go to the fi eld and visit the PRET team to see them in action. The third day is statistics. Then we prepare them to do their own research project: we identify a community not too far from here and the students help plan a project, such as a survey on trichiasis and cataracts in the community.

They then have to take a random sample and using the epidemiology and statistical knowledge they’ve just acquired, they plan this. The next day they go to the fi eld accompanied by Mass Laye, a community ophthalmic nurse on the north bank who’s fantastic, especially in the community. He leads a day in the fi eld where they collect the data from the community.

Then on the Friday they bring me back the results; I collate it all and we put the data together, and on the basis of this they write a report which covers the aim and method. So they have a research project with data they’ve collected using their newly-acquired theoretical knowledge.

What is the trachoma situation in The Gambia’s neighbouring countries?
AS: The Gambia is surrounded by trachoma endemic countries, and everyone agrees that there’s no way we can get rid of trachoma unilaterally. Senegal and Guinea Bissau have some data that qualifi es them for azithromycin. And we’ve been able to do some work with Casamance, so we hope they will qualify for a donation, although being part of Senegal they cannot apply on their own. However, we may be able to relocate some of our stock from here.

SB/EHE: Based on preliminary data from Casamance it would seem that there may not be a need for mass treatment. However, they have a backlog of trichiasis cases that needs attending to. Last December Emma and Robin Bailey went to Casamance and helped to set up a survey of the region. That will give a good idea of the risk of reinfection from Casamance. The survey that was done in Guinea Bissau will also help them to develop a plan for treatment of the Bijagos Islands, and to start building a more technical relationship with Eye Care services in Guinea Bissau.

What are the plans for disease surveillance?
AS: We’ve been waiting for the WHO’s guidelines on surveillance but they are yet to come…However, we have agreed as a country that we should go ahead and do a survey and we are making plans, including a workshop in December.

EHE: Recent data from the Carter Center suggests that the average cost of a trachoma survey at the district level is about $4000 - that’s equivalent to about two weeks’ worth of lab tests, so it’s not much at all…In the PRET survey areas we’ve already got the household data, so surveillance in The Gambia will be relatively easy.

Trachoma: towards elimination in The Gambia

The trachoma story is an example of the successful partnership between NECP, LSHTM and the MRC.
EHE: Yes. Without the support of the NECP, PRET would not have been possible. For example, we’ve got six community ophthalmic nurses at present as active members of our fi eld team. When we go into the community they are recognised as being a part of it. This really helps with explaining why we are taking samples and why we need to give azithromycin as part of elimination in the whole country. They understand it isn’t just another MRC project.

AS: I am personally - and as a programme - grateful for the collaboration we have in trachoma control. People are listening to us, and not just in The Gambia. The beauty of this partnership is the teamwork and support that the NECP gets from this collaboration. If we’d followed the WHO strategy I don’t know where we’d be now…I can’t imagine us being at this point without the support we’ve received from PRET.…