**3. Chloroquine-resistant acute** *P. vivax*

Resistance to CQ by the asexual stages of *P. vivax* has been documented in most endemic regions [4, 5]. Resistant strains dominate the malarious Western Pacific and Indonesian archipelago and nations there have adopted highly efficacious ACTs [11] as first-line therapy. With the possible exception of artesunate combined with sulfadoxine-pyrimethamine, all ACTs have shown superb efficacy in killing asexual blood stages of *P. vivax* [31]. The safety and efficacy of PQ against relapse when combined with partner blood schizonticides other than CQ, quinine, or dihydroartemisinin-piperaquine [32, 33] require validation in clinical trials [14]. Elsewhere, for now, resistance appears sporadically and at relatively low frequencies. Despite substantial efforts to identify molecular markers of *P. vivax* resistance to antimalarial drugs, none have yet been validated. *In vivo* testing in patients or relatively difficult *ex vivo* drug testing procedures remain necessary [34]. The monitoring of antimalarial efficacy offers possible relief from risk of failure due to parasite resistance to specific therapies, but this is carried out relatively infrequently.
