Mild tertian malaria is caused by-
a. Plasmodium malariae
b. P. ovale
c. P. falciparum
d. None of these

Answer Verified Verified
Hint: A parasitic protozoan species that causes tertian malaria is rare and considerably less harmful compared to other parasites. This malaria mainly exists in countries in Africa.

Complete answer:
> Option A is incorrect. Plasmodium malariae is a protozoan parasite which causes malaria in humans. It is one of many Plasmodium parasite species that infect other organisms as pathogenic agents. It is recorded in areas of the South American Amazon Basin. Female Anopheles mosquitoes transmit the plasmodium parasite, which are known as "night-biting" mosquitoes because they most often bite between dusk and dawn. If a mosquito bites an already malaria-infected human, it may also become infected and spread the parasite to others.

> Option B is correct. Plasmodium ovale is a parasitic protozoan species which causes tertian malaria in humans. Fever which occurs every third day characterises this malaria. It is called benign, since it is caused by P. vivax and P. ovale species. The mortality of infection with these species is very limited. While similar to P. vivax, P. ovale can infect individuals who are negative to the Duffy blood group, as is the case for many Sub Saharan African residents. This explains the higher prevalence of P. ovale in most of Africa (rather than P. vivax)

> Option C is incorrect. Plasmodium falciparum is a mammalian protozoan parasite which are unicellular, and the deadliest Plasmodium species that causes malaria in humans. The parasite is transmitted via a female Anopheles mosquito's bite, and causes falciparum malaria, the most dangerous type of the disease. It is widely distributed in tropical areas worldwide, and especially in Africa where this species predominates. It can cause severe malaria as it multiplies very rapidly in the blood and can cause severe blood loss (anaemia).

> Option D is incorrect. Plasmodium ovale is a parasitic protozoan species which causes tertian malaria in humans. It is one of many protozoan parasite species that infect humans including Plasmodium falciparum and Plasmodium vivax that are responsible for most malaria infections. Compared to these two parasites it is rare, and considerably less harmful than P. falciparum.

Hence, The correct answer is option (B).

Note: Chloroquine, like most antimalarial agents, is active against the parasite's erythrocytic stages; other agents are required for the radical cure of P. vivax and P. ovale infections.