South-East Asia Regional Conference on Epidemiology

222 | <strong>South</strong>-<strong>East</strong> <strong>Asia</strong> <strong>Regional</strong> <strong>Conference</strong> on Epidemiology
generated from more than 3000 patients investigated during the last 10 years on whom the efficacy of
the drugs has been systematically measured is the rapidity (clearance time) with which the parasites
disappear from the blood. If blood smears are taken everyday from day 0 onwards, parasites usually
disappear at least after 72 hours. It means the drug under evaluation is performing very well. Year by
year, there is an increasing proportion of patients showing persisting falciparum parasites after 72
hours, meaning on day 3, and even day 4 and day 5. This observation was a warning that the parasite
clearance time is increasing over time, which is something unusual, and which needs to be closely
monitored and investigated (12). Thus, it is clear that the drug is no longer acting as it should. This
critical finding has triggered additional survey and studies by the international community.
Subsequent studies made it clear that even at 2000-km distance there are differences between
the parasites. The parasite clearance times on the Cambodian side and on the Myanmar side as
well as between the western part of Thailand and the western part of Cambodia differ significantly
(13). Policy-makers, researchers and programme managers are considering why it is happening and
what to do next. There is a difference between different sites; the parasite clearance time should be
between 24 and 48 hours, but in some sites, more than three days are needed to clear all parasites with
an artemisinin-based combination. The situation is making experts think that something wrong is
happening in that part of the world which could affect other countries as well if potential geneticallymodified
parasites are brought in different locations. A similar situation has been observed in one site
in the southern part of Viet Nam where the clinical response is 85%, whereas it should be more than
90%. In Myanmar, a comparison of results between different sites shows that the therapeutic efficacy
response remains acceptable except in one location in the south-eastern part where the proportion of
patients with parasites on day 3 is up to 18% compared to less than 5% in other sites. These findings
give some idea that something unusual is happening in specific locations. In western Thailand and in
the southern part of the province of Yunnan, China, bordering Myanmar, there are sites with a more
than 10% therapeutic failure rate after 28 days. This is above the 10% threshold recommended by
WHO for countries in the region to shift to another more effective combination.
However, locations where the proportion of therapeutic failure rate is documented as the highest
remain on the Cambodia-Thailand border. This is where the situation is considered as the worst and
where containment operations have to be intensified. Highly sophisticated surveys carried out by
international researchers have confirmed such worrisome results from in vivo studies confirming
the Cambodia-Thailand border as the epicentre of falciparum resistance to artemisinins in the world
(13,14,15). Other similar sites have been found last year on the Myanmar-Thai border, in the southern
part of Yunnan and on the southern Viet Nam-Cambodia border. Studies are currently being performed
in those locations to confirm the presence of additional hotspots of artemisinin resistance in the
Mekong region [WHO reports under finalization, 2010].
Since 2007-08, a bi-country containment project has been in operation which involves containment
activities on the border between China and Myanmar.
This would involve collaboration between two countries where WHO will act as the facilitator.
Cambodia and Thailand will also be engaged in a similar operation, especially in provinces in western
Cambodia and eastern Thailand. This ambitious cross-border project aims to contain, and even
eliminate, all suspected resistant parasites. This is a project of global interest which is employing both
regional and global approaches to monitor resistance and mount a supranational response. The global
monitoring is going to go beyond the Mekong region to India, Bangladesh, Indonesia, Vanuatu, Papua
New Guinea, Solomon Islands and other continents like Africa.
The multicountry response has been successful in getting funds initially from the Bill and Melinda
Gates Foundation, and subsequently from the Global Fund, in addition to domestic funding. In the hot