Antimalarial drug efficacy and resistance in malaria-endemic countries in HANMAT-PIAM_net countries of the Eastern Mediterranean Region 2016-2020: Clinical and genetic studies

INTRODUCTION

The World Health Organization recommends regular monitoring of the efficacy of nationally recommended antimalarial drugs. We present the results of studies on the efficacy of recommended antimalarials and molecular markers of artemisinin and partner resistance in Afghanistan, Pakistan, Somalia, Sudan and Yemen.

METHODS

Single-arm prospective studies were conducted to evaluate the efficacy of artesunate-sulfadoxine-pyrimethamine (ASSP) in Afghanistan and Pakistan, artemether-lumefantrine (AL) in all countries, or dihydroartemisinin-piperaquine (DP) in Sudan for the treatment of Plasmodium falciparum. The efficacy of chloroquine (CQ) and AL for the treatment of Plasmodium vivax was evaluated in Afghanistan and Somalia, respectively. Patients were treated and monitored for 28 (CQ, ASSP and AL) or 42 (DP) days. Polymerase chain reaction (PCR)-corrected cure rate and parasite positivity rate at Day 3 were estimated. Mutations in the P. falciparum kelch 13 (Pfk13) gene and amplifications of plasmepsin (Pfpm2) and multidrug resistance-1 (Pfmdr-1) genes were also studied.

RESULTS

A total of 1680 (249 for ASSP, 1079 for AL and 352 for DP) falciparum cases were successfully assessed. A PCR-adjusted ASSP cure rate of 100% was observed in Afghanistan and Pakistan. For AL, the cure rate was 100% in all but four sites in Sudan, where cure rates ranged from 92.1% to 98.8%. All but one patient were parasite-free at Day 3. For P. vivax, cure rates were 98.2% for CQ and 100% for AL. None of the samples from Afghanistan, Pakistan and Yemen had a Pfk13 mutation known to be associated with artemisinin resistance. In Sudan, the validated Pfk13 R622I mutation accounted for 53.8% (14/26) of the detected non-synonymous Pfk13 mutations, most of which were repeatedly detected in Gadaref. A prevalence of 2.7% and 9.3% of Pfmdr1 amplification was observed in Pakistan and Yemen, respectively.

CONCLUSION

High efficacy of ASSP, AL and DP in the treatment of uncomplicated falciparum infection and of CQ and AL in the treatment of P. vivax was observed in the respective countries. The repeated detection of a relatively high rate of Pfk13 R622I mutation in Sudan underscores the need for close monitoring of the efficacy of recommended ACTs, parasite clearance rates and Pfk13 mutations in Sudan and beyond. Registration numbers of the trials: ACTRN12622000944730 and ACTRN12622000873729 for Afghanistan, ACTRN12620000426987 and ACTRN12617001025325 for Pakistan, ACTRN12618001224213 for Somalia, ACTRN12617000276358, ACTRN12622000930785 and ACTRN12618001800213 for Sudan and ACTRN12617000283370 for Yemen.

Public health impact of the spread of Anopheles stephensi in the WHO Eastern Mediterranean Region countries in Horn of Africa and Yemen: need for integrated vector surveillance and control

BACKGROUND

Anopheles stephensi is an efficient vector of both Plasmodium falciparum and Plasmodium vivax in South Asia and the Middle East. The spread of An. stephensi to countries within the Horn of Africa threatens progress in malaria control in this region as well as the rest of sub-Saharan Africa.

METHODS

The available malaria data and the timeline for the detection of An. stephensi was reviewed to analyse the role of An. stephensi in malaria transmission in Horn of Africa of the Eastern Mediterranean Region (EMR) in Djibouti, Somalia, Sudan and Yemen.

RESULTS

Malaria incidence in Horn of Africa of EMR and Yemen, increased from 41.6 in 2015 to 61.5 cases per 1000 in 2020. The four countries from this region, Djibouti, Somalia, Sudan and Yemen had reported the detection of An. stephensi as of 2021. In Djibouti City, following its detection in 2012, the estimated incidence increased from 2.5 cases per 1000 in 2013 to 97.6 cases per 1000 in 2020. However, its contribution to malaria transmission in other major cities and in other countries, is unclear because of other factors, quality of the urban malaria data, human mobility, uncertainty about the actual arrival time of An. stephensi and poor entomological surveillance.

CONCLUSIONS

While An. stephensi may explain a resurgence of malaria in Djibouti, further investigations are needed to understand its interpretation trends in urban malaria across the greater region. More investment for multisectoral approach and integrated surveillance and control should target all vectors particularly malaria and dengue vectors to guide interventions in urban areas.

High efficacy of two artemisinin-based combinations: artesunate + sulfadoxine-pyrimethamine and artemether-lumefantrine for falciparum malaria in Yemen

BACKGROUND

Artesunate + sulfadoxine-pyrimethamine (AS + SP) has been the first-line treatment and artemether-lumefantrine (AL) the second-line treatment for uncomplicated falciparum malaria in Yemen since 2005. This paper reports the results of studies conducted to monitor therapeutic efficacy of these two drugs in sentinel sites in Yemen.

METHODS

Eight therapeutic efficacy studies were conducted in six sentinel sites during the period 2009-2013 in Yemen. Five studies were for the evaluation of AS + SP (total of 465 patients) and three studies (total of 268 patients) for the evaluation of AL. The studies were done according to standard WHO protocol 2009 with 28-day follow-up.

RESULTS

In the evaluation of AS + SP, the PCR-corrected cure rate was 98 % (95 % CI 92.2-99.5 %) in one site and 100 % in all of the other four sites. In the sites where AL was evaluated, the PCR-corrected cure rate was 100 % in all the sites. All patients were negative for asexual parasitaemia on day 3 in both the AS + SP and the AL groups. There was a higher rate of clearance of gametocytaemia in the AL-treated group when compared with the AS + SP groups from day 7 onwards.

CONCLUSION

AS + SP remains the effective drug for uncomplicated falciparum malaria in Yemen. AL is also highly effective and can be an appropriate alternative to AS + SP for the treatment of falciparum malaria. AL demonstrated a higher efficacy in clearing microscopic gametocytaemia than AS + SP.

TRIAL REGISTRATION

Trial registration number ACTRN12610000696099.