Question

Which one of the following diseases is caused by protozoans?
A) Malaria
B) Typhoid
C) Tetanus
D) Yellow fever

Answer 1

Hint: Protozoans are bigger unicellular organisms than bacteria. They are parasite protozoans like Plasmodium which have the potential to cause a disease called malaria.

Step by step answer: Protozoans are single-celled eukaryotic organisms that are either free-living or parasitic in nature. They feed on the dead matter such as other tissues or microorganisms.
Malaria is caused by a malarial parasite which is a protozoan. Malaria is caused by the four species called Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae. The parasite lives on mosquitoes and it is transmitted into the blood when mosquitoes bite humans. So, malaria is caused by a protozoan called Plasmodium. Not every mosquito bite causes malaria. Some of the common symptoms of malaria are as follows:
i. High fever
ii. Headache
iii. Vomiting
iv. Diarrhoea
v. Muscle ache
The lifecycle of Plasmodium occurs in both humans and mosquitoes. Sporozoites are the infectious form of the parasite that infect hepatic cells of the liver first and then converts into merozoites to trophozoites to schizonts. This form of the last parasite infects the RBCs in blood and there is a decrease in total RBC count in the body. Thus, the fever is introduced in the body and this is the clinical onset of malaria where there is a decrease in RBCs and irregular fevers with regular intervals.
Hence, the correct answer is option A.

Note: The phase of malarial parasite life cycle includes: schizogony (development of gamete in human RBC), gamogony (development of male and female gametes) and sporogony (formation of oocytes and sporozoites in the mosquito). Only female mosquitoes called anopheles cause malaria as only female mosquitoes bite humans and transmit parasites into humans.