Question

Identify the set of malarial parasites with 48 hr cycle
A. Plasmodium malariae, P. falciparum and P. ovale
B. Plasmodium malariae, P. falciparum and P. vivax
C. Plasmodium malariae, P. ovale and P. vivax
D. Plasmodium falciparum, P. ovale and P. vivax

Answer 1

The life cycle of a pathogen can be defined as the complex series of events that generally include penetration of organisms into the host, infection, incubation, reproduction and survival and this happens between the appearance and reappearance of a pathogen in a host.

Complete answer:
Let us see the life cycles of each of the species of Plasmodium given above.
Plasmodium malariae:
Plasmodium malariae is one of the malarial parasites that causes malaria in humans. The erythrocytic cycle of P. malariae is 48 hours or 3 days. It infects the liver initially and then moves into the blood and digests haemoglobin. The development of the parasite happens in the erythrocytes.
Plasmodium falciparum:
P. falciparum is the parasite that causes the most severe malarial infection. The erythrocytic cycle of P. falciparum exhibits a 48 hour cycle during which the parasites are released from the blood which causes a 48 hour fever in the infected hosts.
Plasmodium vivax:
The infections from P. vivax are the most common and it’s the main cause of recurring malaria. The erythrocytic cycle in Plasmodium vivax is also 48 hours.
Plasmodium ovale:
Plasmodium ovale is the parasite that causes tertian malaria in humans. The erythrocytic cycle lasts for about 48-50 hours for this parasite.
So, we can see that the only species with an erythrocytic cycle other than hours is Plasmodium.
So, the correct answer is “Option D”.

Note:
Tertian malaria is the condition where malarial fever is seen every three days. Plasmodium vivax and Plasmodium ovale causes tertian malaria in humans.
Recurrent malaria is a condition where symptoms of malaria reappear even after a time of no symptoms being shown by the body. The parasites survive in the blood and they reappear when conditions are favourable like weakening of the immune system.