Reviewing and planning therapeutic efficacy studies (TES) to monitor antimalarial drug resistance in the Greater Mekong Subregion (GMS)
Other TitlesReport of a workshop, Kunming, the People's Republic of China, 12-13 June 2012
AbstractSince 2008, the WHO Mekong Malaria Programme (MMP) has been providing technical assistance and coordination to six countries in the Greater Mekong Sub-region (Cambodia, China, Lao People's Democratic Republic, Myanmar, Thailand and Viet Nam) to actively monitor the therapeutic efficacy of their first-line antimalarial drugs using a standard in vivo protocol. In June 2012, the MMP organized a workshop in Kunming, China for all six countries on the Therapeutic Efficacy Study Network to review national study results from 2010-2011 and plan for 2013-2014. Results showed that while artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DHA-PIP) are still highly effective in Lao People's Democratic Republic and China, respectively, the efficacy of artemisinin-based combination therapy (ACT) appears to be declining in other countries. The adequate clinical and parasitological response (ACPR) for DHA-PIP in western Cambodia has dropped below 80%. Both DHA-PIP and artesunate+mefloquine (A+M) show a high proportion of patients who remain positive on day 3 ("D3 positives") of treatment providing suspicion of artemisinin resistance in investigated areas along the Thai-Myanmar border. In this border region, specific concerns for A+M therapeutic efficacy surfaced from 2011 data in Kanchanaburi (87% ACPR) and Ranong (87-90% ACPR), and preliminary results with AL in Ranong and Tak had 90% ACPR. In Myanmar's eastern provinces bordering Thailand, around 6% patients were PCR-confirmed treatment failures, including over 10% D3 positives in Bago and Mon states. Further suspicion of artesunate resistance was demonstrated in the southern Myanmar state of Kawthuang in 2011 where 27% patients had persistent day 3 parasitaemia in the artesunate monotherapy study. In Viet Nam, DHA-PIP efficacy is still high in Binh Phuoc and Gia Lai (ACPR>96%), but D3 positivity is significantly above the threshold in these two provinces. Although 7-day artesunate monotherapy studies showed >96% cure rates, the D3 positivity rates with monotherapy are also high in Binh Phuoc and the nearby province of Dak Nong. The TES Network jointly drafted plans and budget to continue monitoring Plasmodium falciparum and Plasmodium vivax efficacy for 2013 and 2014. All countries expressed strong support to continue these studies; yet they acknowledged significant technical and logistic challenges. Even utilizing a multi-district/village approach, all countries increasingly face difficulties to meet the required sample size due to a clear decline in malaria cases. Moreover, migrants contribute significantly to the disease burden but are difficult to trace and follow up. Cross-border meetings were proposed to share and discuss results, address common ethical issues with migrants, and take coordinated actions especially on artemisinin resistance containment.
World Health Organization, Regional Office for South-East Asia. (2013). Reviewing and planning therapeutic efficacy studies (TES) to monitor antimalarial drug resistance in the Greater Mekong Subregion (GMS). WHO Regional Office for South-East Asia. http://www.who.int/iris/handle/10665/206333