**2.2** *In vitro* **cultivation of** *Plasmodium vivax*

Studies on *P. vivax* resistance to drugs used either as blood schizontocide or radical cure lags far behind *P. falciparum*. The absence of *in vitro* culture system for propagating the blood stage of *P. vivax* has made the *in vivo* test is the only way to determine the *P. vivax* drug response to any antimalarial drugs [17]. Advance in molecular and cellular biology within the last few decades have contributed significantly to the progress in the establishment and refinement of ex vivo drug test and repeatable *in vitro* cultivation in *P vivax* [18–20]. It has long been known that *P. vivax* invade exclusively young erythrocyte (reticulocytes) of Duffy antigen positive vertebrate host for asexual development in human and non human primate [21]. Recent progress have identified more specifically that *Plasmodium vivax* preferentially invade stage I reticulocytes CD71highTOhigh) [22]. Other progress also showed the success for long term cultivation, including cryopreservation and re-cultivation of *P. vivax* using blood of certain non-human primate [23]. With the aforementioned evidence, *ex vivo* and *in vitro* drug testing platform of *P. vivax* for novel drug development is now workable.
