biology : class12 Plasmodium knowlesi : Causative Organism, Plasmodium, Life Cycle, Symptoms, Prevention : Malaria MCQ Questions and Answers
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Plasmodium knowlesi
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MCQ Questions
1. Which feature most reliably distinguishes Plasmodium knowlesi from Plasmodium malariae in a human blood-film examination?
A.
A 24-hour erythrocytic replication cycle producing quotidian parasitaemia
B.
A 72-hour erythrocytic replication cycle producing quartan fever
C.
Formation of crescent-shaped gametocytes in peripheral blood
D.
Exclusive invasion of reticulocytes rather than mature erythrocytes
Correct Answer:
A 24-hour erythrocytic replication cycle producing quotidian parasitaemia
Explanation:
Plasmodium knowlesi undergoes asexual erythrocytic schizogony approximately every 24 hours, which can produce quotidian fever and rapidly rising parasitaemia. This contrasts with the 72-hour cycle of P. malariae.
2. In the natural transmission cycle of Plasmodium knowlesi, humans are best described as:
A.
The only definitive hosts in which sexual reproduction occurs
B.
Accidental hosts infected after zoonotic transmission from macaques
C.
Intermediate hosts that transmit the parasite directly by skin contact
D.
Reservoir hosts that maintain the parasite independently of mosquitoes
Correct Answer:
Accidental hosts infected after zoonotic transmission from macaques
Explanation:
Plasmodium knowlesi is primarily a parasite of macaques, especially long-tailed and pig-tailed macaques. Humans usually become infected when Anopheles mosquitoes acquire parasites from macaques and subsequently bite people.
3. Which mosquito-related statement is most accurate for human infection with Plasmodium knowlesi?
A.
Transmission occurs through infected female Anopheles mosquitoes that feed on both macaques and humans
B.
Transmission occurs mainly through male Anopheles mosquitoes that feed on plant sap
C.
Transmission requires direct transfer of merozoites from macaques to human blood
D.
Transmission is restricted to Aedes mosquitoes breeding in urban containers
Correct Answer:
Transmission occurs through infected female Anopheles mosquitoes that feed on both macaques and humans
Explanation:
Female Anopheles mosquitoes transmit P. knowlesi. A mosquito can acquire gametocytes from an infected macaque and later inoculate sporozoites into a human during feeding.
4. Why can Plasmodium knowlesi infections become severe more rapidly than many infections caused by Plasmodium malariae?
A.
P. knowlesi completes erythrocytic schizogony about every 24 hours, allowing rapid parasite multiplication
B.
P. knowlesi remains permanently confined to hepatocytes and therefore avoids immune recognition
C.
P. knowlesi produces no merozoites, so infected erythrocytes accumulate without rupture
D.
P. knowlesi undergoes erythrocytic schizogony only once every 14 days, causing prolonged tissue damage
Correct Answer:
P. knowlesi completes erythrocytic schizogony about every 24 hours, allowing rapid parasite multiplication
Explanation:
The short 24-hour asexual blood-stage cycle of P. knowlesi can cause a rapid increase in parasite density. This increases the risk of severe malaria, including complications such as thrombocytopenia and organ dysfunction.
5. A blood film from a patient returning from a forested region shows delicate ring forms and band-shaped trophozoites, but the laboratory initially reports P. malariae. Which explanation is most appropriate?
A.
P. knowlesi can resemble P. malariae microscopically, so molecular confirmation may be required
B.
P. knowlesi is morphologically identical to P. vivax and cannot form band-shaped trophozoites
C.
P. knowlesi occurs only in liver tissue and therefore cannot appear in a blood film
D.
P. knowlesi produces only crescent-shaped gametocytes, making microscopy definitive
Correct Answer:
P. knowlesi can resemble P. malariae microscopically, so molecular confirmation may be required
Explanation:
P. knowlesi may resemble P. malariae in stained blood films, particularly in later blood stages. Because treatment and risk assessment are important, PCR or another species-specific molecular method may be needed for confirmation.
6. Which sequence correctly represents the major stages of the Plasmodium knowlesi life cycle after an infected mosquito bites a human?
A.
Sporozoites enter blood, invade hepatocytes, release merozoites, and initiate erythrocytic cycles
B.
Merozoites enter hepatocytes, become gametocytes, and return to the mosquito through urine
C.
Gametocytes invade hepatocytes, form cysts, and are released through respiratory droplets
D.
Ookinetes enter human erythrocytes, produce sporozoites, and then invade liver cells
Correct Answer:
Sporozoites enter blood, invade hepatocytes, release merozoites, and initiate erythrocytic cycles
Explanation:
During a P. knowlesi infection, mosquito-inoculated sporozoites reach the liver and develop into schizonts. Liver-stage merozoites are released into the bloodstream, where they invade erythrocytes and undergo repeated asexual multiplication.
7. Which observation would most strongly support zoonotic Plasmodium knowlesi transmission rather than sustained transmission of a strictly human malaria parasite?
A.
Human cases clustered near macaque habitats where forest-fringe Anopheles mosquitoes are active
B.
Human cases occurring only in hospitals without mosquito exposure
C.
Transmission occurring exclusively through contaminated drinking water
D.
Infections restricted to individuals who have received blood transfusions
Correct Answer:
Human cases clustered near macaque habitats where forest-fringe Anopheles mosquitoes are active
Explanation:
P. knowlesi is maintained principally in macaque populations and can spill over into humans through mosquito vectors. Proximity to macaque habitats and exposure to forest or forest-edge Anopheles mosquitoes therefore supports zoonotic transmission.
8. Which clinical pattern is particularly concerning in a patient with confirmed Plasmodium knowlesi infection?
A.
A rapidly increasing parasitaemia accompanied by thrombocytopenia and deteriorating organ function
B.
A slowly progressive infection limited to the skin with no blood-stage multiplication
C.
A lifelong asymptomatic hepatic infection with no possibility of erythrocyte invasion
D.
A localized intestinal infection producing malabsorption but no systemic disease
Correct Answer:
A rapidly increasing parasitaemia accompanied by thrombocytopenia and deteriorating organ function
Explanation:
P. knowlesi can multiply rapidly because of its 24-hour erythrocytic cycle. Severe disease may develop with high parasitaemia, thrombocytopenia, respiratory distress, renal impairment, or other organ dysfunction.
9. Which preventive measure is most directly relevant to reducing human exposure to Plasmodium knowlesi in endemic forest-edge areas?
A.
Reducing bites from Anopheles mosquitoes through insecticide-treated nets, repellents, and protective clothing
B.
Avoiding undercooked pork because P. knowlesi is transmitted as a foodborne helminth
C.
Isolating infected people to prevent ordinary respiratory transmission between humans
D.
Drinking only boiled water because the parasite develops in contaminated water
Correct Answer:
Reducing bites from Anopheles mosquitoes through insecticide-treated nets, repellents, and protective clothing
Explanation:
Human P. knowlesi infection is acquired through the bite of an infected female Anopheles mosquito. Personal protection against mosquito bites is therefore central to prevention, especially in areas where macaques and competent vectors coexist.
10. Why is identifying Plasmodium knowlesi specifically important when interpreting a positive malaria rapid diagnostic test or microscopy result?
A.
Some diagnostic methods may cross-react or misclassify species, while P. knowlesi can progress rapidly and requires appropriate management
B.
P. knowlesi is never detectable in blood, so every positive result must represent a different parasite
C.
Species identification is unnecessary because P. knowlesi cannot cause severe illness in humans
D.
P. knowlesi is transmitted only by transfusion, so vector exposure has no diagnostic relevance
Correct Answer:
Some diagnostic methods may cross-react or misclassify species, while P. knowlesi can progress rapidly and requires appropriate management
Explanation:
P. knowlesi may be confused with other malaria species by microscopy or may produce variable results in some rapid diagnostic tests. Correct identification is important because its rapid blood-stage multiplication can lead to severe disease and demands prompt treatment.
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