vivax episodes which are conventionally always ascribed to homologous hypnozoite
Failure to detect hypnozoites
in hepatic tissue containing exoerythrocytic schizonts of Plasmodium knowlesi.
In this stage, some species of Plasmodium can form hypnozoites
, which can remain hidden in the liver for many weeks or years.
This can be explained in terms of the fact that both P vivax and P ovale form hypnozoites
(dormant parasite stages in the liver that cause relapse weeks to years after the primary infection ) therefore share a common niche.
Although it is unclear what causes the reactivation of hypnozoites
, this phenomenon is one of the main obstacles to the elimination of malaria, since they maintain active transmission of the disease (2,6).
vivax and P.ovale occurrence, additional preventive treatment against liver hypnozoites
of these species should be administered.
Plasmodium vivax is not fatal, though it is responsible for considerable morbidity in those populations where it is endemic through hypnozoites
(the dormant parasite stages in liver) causing relapse within weeks to months after primary episode (2).
vivax invariably in the form of dormant hypnozoites
Unlike Plasmodium vivax and Plasmodium ovale, Plasmodium malariae is not known to have continued liver cycle with hypnozoites
. The only way to have a reinfection without reexposure is from its preexisting erythrocytic forms; this is known as recrudescence.
 has revealed heterologous reactivation of hypnozoites
leading to recurrence, even in the patients from area where reinfection was ruled out.
Nadjm and Behrens  state that relapse is when symptoms reappear after the parasites had been eliminated from blood but persist as dormant hypnozoites
in liver cells.