WHICH OF THE FOLLOWING TYPES OF MALARIA CAN CAUSE RELAPSING ILLNESS AT INTERVALS OVER MONTHS AND YEARS WITHOUT THE PATIENT BEING REINFECTED

• A. Plasmodium vivax ✓
• B. Plasmodium knowlesi
• C. Plasmodium malariae
• D. Plasmodium falciparum

Plasmodium vivax is the type of malaria that can cause relapsing illness at intervals over months and years without the patient being reinfected. This characteristic is due to the unique biology of Plasmodium vivax, which forms dormant liver stages known as hypnozoites. These hypnozoites can remain in the liver for extended periods, leading to relapses of the infection even after the initial acute illness has been treated.

When a person is infected with Plasmodium vivax, some of the parasites develop into these dormant forms in the liver instead of immediately causing symptoms by invading red blood cells. These hypnozoites can reactivate weeks, months, or even years later, causing recurrent episodes of malaria without the individual being reinfected by mosquito bites. This ability to cause relapses sets Plasmodium vivax apart from other types of malaria.

In contrast, Plasmodium falciparum, Plasmodium malariae, and Plasmodium knowlesi do not typically exhibit this pattern of relapsing illness over extended periods without reinfection. While these species can cause severe and sometimes chronic infections, they do not form hypnozoites in the liver that lead to relapses in the same way that Plasmodium vivax does.

In other words, Plasmodium vivax is the type of malaria that can cause relapsing illness at intervals over months and years without the patient being reinfected. This is due to the ability of P. vivax to form dormant liver stages known as hypnozoites, which can reactivate and cause relapses even after successful treatment of the acute infection.

Plasmodium knowlesi, Plasmodium malariae, and Plasmodium falciparum do not typically cause relapsing illness in the same manner as P. vivax. Plasmodium knowlesi is a zoonotic malaria parasite primarily found in macaque monkeys and can infect humans, causing severe and potentially fatal malaria but does not have a relapsing pattern like P. vivax. Plasmodium malariae causes a chronic infection with low parasitemia levels but does not form hypnozoites in the liver for relapses. Plasmodium falciparum is known for causing severe malaria but does not exhibit a relapsing pattern like P. vivax.