Two types (species) of parasites, Plasmodium vivax and P. ovale, have liver stages and can remain in the body for years without causing sickness. If not treated, these liver stages may reactivate and cause malaria attacks (relapses) after months or years without symptoms.he type of drugs and length of treatment depend on the type of malaria, where the person was infected, their age, whether they are pregnant, and how sick they are at the start of treatment. For health-care providers treating malaria, please see the CDC Guidelines for Treatment of Malaria in the US.