Question:hard
Which of the following is the carrying agent (vector) for the disease showing the given characteristic appearance on microscopy?
Which of the following is the carrying agent (vector) for the disease showing the given characteristic appearance on microscopy?
Show Hint
Maltese cross in RBCs means babesiosis; recall its hard-tick vector.
Updated On: Jun 24, 2026
- Anopheles
- Ixodes scapularis tick
- Louse
- Rat flea
Show Solution
The Correct Option is B
Solution and Explanation
Step 1: Decode the microscopy. Four pear-shaped parasites sitting inside one erythrocyte with their tips touching form a tetrad that looks like a Maltese cross. This appearance is the signature of Babesia infection.
Step 2: Recall the carrier. Babesia is spread to humans through the bite of the hard tick $Ixodes\ scapularis$, which also carries the agent of Lyme disease.
Step 3: Avoid the malaria trap. Because intraerythrocytic ring forms resemble falciparum malaria, remember two discriminators: babesiosis shows the Maltese cross and lacks hemozoin pigment, whereas malaria lacks the cross and contains the pigment.
Step 4: Eliminate other vectors. Anopheles mosquitoes carry malaria, lice carry typhus and relapsing fever, and rat fleas carry plague, so none of them fit the Maltese-cross disease.
\[\boxed{\text{Ixodes scapularis tick}}\]
Step 2: Recall the carrier. Babesia is spread to humans through the bite of the hard tick $Ixodes\ scapularis$, which also carries the agent of Lyme disease.
Step 3: Avoid the malaria trap. Because intraerythrocytic ring forms resemble falciparum malaria, remember two discriminators: babesiosis shows the Maltese cross and lacks hemozoin pigment, whereas malaria lacks the cross and contains the pigment.
Step 4: Eliminate other vectors. Anopheles mosquitoes carry malaria, lice carry typhus and relapsing fever, and rat fleas carry plague, so none of them fit the Maltese-cross disease.
\[\boxed{\text{Ixodes scapularis tick}}\]
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