Pathogens and Parasites Practice Questions
20 free Pathogens and Parasites practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which organism is the causative agent of malaria in humans?
- A Entamoeba histolytica
- B Plasmodium species (e.g. P. falciparum)
- C Trypanosoma gambiense
- D Leishmania donovani
Correct answer: Plasmodium species (e.g. P. falciparum)
Malaria is caused by protozoan parasites of the genus Plasmodium, with P. falciparum being the most lethal species. They invade red blood cells and are transmitted by the bite of infected female Anopheles mosquitoes.
Which mosquito species acts as the vector for dengue fever?
- A Anopheles
- B Culex
- C Aedes (especially Aedes aegypti)
- D Mansonia
Correct answer: Aedes (especially Aedes aegypti)
Dengue fever is transmitted primarily by Aedes mosquitoes, especially Aedes aegypti. These mosquitoes breed in small collections of clean stagnant water and are active during the day.
Typhoid fever is caused by which bacterium?
- A Vibrio cholerae
- B Salmonella typhi
- C Shigella dysenteriae
- D Escherichia coli
Correct answer: Salmonella typhi
Typhoid fever is caused by the bacterium Salmonella typhi. It spreads through contaminated food and water.
Which stage of Plasmodium infects human red blood cells?
- A Sporozoite
- B Gametocyte
- C Merozoite
- D Ookinete
Correct answer: Merozoite
Merozoites invade human red blood cells during malaria infection. Their multiplication causes periodic fever and chills.
Which disease is transmitted by the bite of female Anopheles mosquito?
- A Dengue fever
- B Malaria
- C Chikungunya
- D Yellow fever virus
Correct answer: Malaria
Malaria is transmitted by the bite of the female Anopheles mosquito. The mosquito introduces Plasmodium sporozoites into the bloodstream during feeding.
What is the causative organism of amoebiasis?
- A Giardia lamblia protozoan
- B Entamoeba histolytica
- C Balantidium coli protozoan
- D Plasmodium vivax parasite
Correct answer: Entamoeba histolytica
Amoebiasis is caused by Entamoeba histolytica, a protozoan parasite that infects the large intestine and can cause dysentery and liver abscesses.
Which disease is also known as kala-azar?
- A Malaria
- B Leishmaniasis
- C Filariasis
- D Trypanosomiasis
Correct answer: Leishmaniasis
Kala-azar is another name for visceral leishmaniasis. It is caused by Leishmania donovani and transmitted by sandflies.
Which parasite causes filariasis (elephantiasis)?
- A Wuchereria bancrofti
- B Taenia solium
- C Ascaris lumbricoides
- D Schistosoma haematobium
Correct answer: Wuchereria bancrofti
Filariasis is caused by Wuchereria bancrofti. It infects the lymphatic system and leads to severe swelling.
Which of the following diseases is caused by a virus?
- A Typhoid fever
- B Malaria
- C Dengue
- D Amoebiasis
Correct answer: Dengue
Dengue is caused by a virus of the Flavivirus genus (Family Flaviviridae). It is transmitted by Aedes mosquitoes, unlike typhoid (bacterium) and malaria (protozoan).
Which symptom is commonly associated with malaria?
- A Persistent dry cough with wheezing
- B Periodic fever with chills
- C Generalized skin rash and itching
- D Persistent watery diarrhoea
Correct answer: Periodic fever with chills
Malaria typically causes periodic fever accompanied by chills and sweating. This cyclical pattern results from the synchronized rupture of infected red blood cells releasing merozoites.
Which mode of transmission is common to both typhoid and cholera?
- A Respiratory airborne droplets
- B Direct sexual contact
- C Contaminated food and water
- D Bite of infected insect
Correct answer: Contaminated food and water
Both typhoid (Salmonella typhi) and cholera (Vibrio cholerae) spread through contaminated food and water. Poor sanitation and unsafe drinking water are the primary risk factors.
Which stage of Plasmodium is injected into humans by the mosquito?
- A Merozoite
- B Gametocyte
- C Sporozoite
- D Zygote
Correct answer: Sporozoite
Sporozoites are injected into humans during a mosquito bite. They first infect liver cells before entering red blood cells.
Which disease is characterized by severe dehydration due to watery diarrhoea?
- A Typhoid
- B Cholera
- C Amoebiasis
- D Malaria
Correct answer: Cholera
Cholera causes severe watery diarrhoea leading to dehydration. It is caused by the bacterium Vibrio cholerae.
Which parasite lives in the human intestine and causes ascariasis?
- A Taenia saginata
- B Ascaris lumbricoides
- C Ancylostoma duodenale
- D Enterobius vermicularis
Correct answer: Ascaris lumbricoides
Ascariasis is caused by the roundworm Ascaris lumbricoides. It lives in the human intestine and affects nutrient absorption.
Which disease involves enlargement of spleen and liver as a major symptom?
- A Dengue fever
- B Kala-azar
- C Typhoid fever
- D Cholera disease
Correct answer: Kala-azar
Kala-azar (visceral leishmaniasis) causes significant enlargement of the spleen (splenomegaly) and liver (hepatomegaly) due to the invasion of macrophages by Leishmania donovani parasites.
Which organism causes sleeping sickness in humans?
- A Trypanosoma gambiense
- B Plasmodium falciparum
- C Leishmania tropica
- D Entamoeba histolytica
Correct answer: Trypanosoma gambiense
Sleeping sickness is caused by Trypanosoma gambiense. It is transmitted by the bite of the tsetse fly.
Which preventive measure is most effective against mosquito-borne diseases?
- A Antibiotic therapy to treat infection
- B Annual vaccination of all individuals
- C Vector control and preventing breeding
- D Isolating patients to avoid contact
Correct answer: Vector control and preventing breeding
Controlling mosquito breeding sites and preventing bites through vector control are the most effective strategies against mosquito-borne diseases like malaria and dengue, as they interrupt transmission at its source.
Which disease spreads through the cyst form of its pathogen in contaminated water?
- A Malaria
- B Dengue
- C Amoebiasis
- D Filariasis
Correct answer: Amoebiasis
Amoebiasis spreads through cysts of Entamoeba histolytica present in contaminated water. These cysts are resistant to harsh conditions.
Which parasite causes intestinal blockage in severe infections?
- A Ascaris lumbricoides
- B Plasmodium vivax
- C Wuchereria bancrofti
- D Giardia lamblia
Correct answer: Ascaris lumbricoides
Heavy infection of Ascaris lumbricoides can cause intestinal blockage. This is due to the large size and number of worms.
Which statement correctly differentiates malaria and dengue?
- A Both are bacterial diseases
- B Malaria is viral and dengue is protozoan
- C Malaria is protozoan and dengue is viral
- D Both are caused by helminths
Correct answer: Malaria is protozoan and dengue is viral
Malaria is caused by protozoan Plasmodium species, whereas dengue is caused by a virus. Both are transmitted by mosquitoes but have different causative agents.