Ectoparasites — MCQs
Which of the following is the most common vector of zoonotic diseases?
Not transmitted by mite -
Which of the following diseases is transmitted by rat flea?
Soft tick transmits:
A lady presented with fever and rashes. She returned from the USA and gives a history of exposure to ticks. Most probable diagnosis is
Which of the following is the carrying agent for Lyme disease?
Chagas disease is transmitted by the following:
A girl from Shimla presented to OPD with fever, hypotension, malaise and axillary and inguinal lymphadenopathy. Culture in glucose broth shows stalactite growth. Most likely causative organism is?
A farmer presents to the emergency department with painful inguinal lymphadenopathy and a history of fever and flu-like symptoms. Clinical examination reveals an ulcer on the leg. Which of the following stains should be used to detect suspected bipolar-stained organisms?
A militant presents with rashes all over his body sparing the palms and soles. On examination, he was febrile and lice were noted. Which of the following is responsible for his condition?
Ectoparasites Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following is the most common vector of zoonotic diseases?
- A. Sand fly
- B. Ticks
- C. Mosquito (Correct Answer)
- D. Mite
Explanation: ***Mosquito*** - Mosquitoes are responsible for transmitting a vast number of **zoonotic diseases** affecting millions globally, including **malaria**, dengue, Zika, and **West Nile virus**. - Their widespread distribution and ability to feed on various hosts, including humans and animals, make them highly efficient **vectors**. *Sand fly* - Sand flies are known vectors for diseases like **leishmaniasis**, but their reach and impact are not as extensive as mosquitoes. - Leishmaniasis primarily affects specific geographic regions and isn't as globally prevalent as mosquito-borne illnesses. *Ticks* - Ticks transmit several important zoonotic diseases such as **Lyme disease**, Rocky Mountain spotted fever, and ehrlichiosis. - While significant, the global burden of tick-borne diseases is generally less than that of mosquito-borne diseases. *Mite* - Mites can transmit diseases like **scrub typhus** (via chiggers) and are associated with scabies, which is an infestation rather than a direct disease transmission. - Their role as vectors for major zoonotic diseases is comparatively limited.
Question 2: Not transmitted by mite -
- A. Rickettsialpox
- B. Scabies
- C. Kyasanur forest disease (Correct Answer)
- D. Scrub typhus
Explanation: ***Kyasanur forest disease*** - **Kyasanur forest disease (KFD)** is a viral hemorrhagic fever transmitted by the **hard tick** (*Haemaphysalis spinigera*), not mites. - Humans typically acquire KFD through contact with infected ticks or sick animals like monkeys. *Rickettsialpox* - Rickettsialpox is caused by *Rickettsia akari* and transmitted by the **house mouse mite** (*Liponyssoides sanguineus*). - The mite serves as both the reservoir and vector for this disease. *Scabies* - Scabies is a skin infestation caused by the **human itch mite** (*Sarcoptes scabiei* var. *hominis*). - The mites burrow into the skin to lay eggs, leading to intense itching and rash. *Scrub typhus* - Scrub typhus is caused by *Orientia tsutsugamushi* and is transmitted to humans by the bite of infected **chiggers** (larval mites) of the family Trombiculidae. - These mites are often found in areas with scrub vegetation, hence the name.
Question 3: Which of the following diseases is transmitted by rat flea?
- A. Oriental sore
- B. Endemic typhus (Correct Answer)
- C. Trench fever
- D. Chagas disease
Explanation: ***Endemic typhus*** - **Endemic (murine) typhus** is caused by *Rickettsia typhi* and is primarily transmitted to humans by the **rat flea** (*Xenopsylla cheopis*) - The rat flea typically acquires the bacteria by feeding on infected rodents (e.g., rats), and then transmits it to humans through its feces while feeding. *Oriental sore* - **Oriental sore** refers to cutaneous leishmaniasis, caused by *Leishmania* parasites. - It is transmitted by the bite of infected **sandflies**, not rat fleas. *Trench fever* - **Trench fever** is caused by *Bartonella quintana* and is transmitted to humans by **human body lice** (*Pediculus humanus corporis*). - This disease is historically associated with crowded and unsanitary conditions, particularly during wartime. *Chagas disease* - **Chagas disease** (American trypanosomiasis) is caused by the parasite *Trypanosoma cruzi*. - It is primarily transmitted by the feces of infected **reduviid bugs** (also known as kissing bugs), which typically bite humans around the face.
Question 4: Soft tick transmits:
- A. Tularemia
- B. Indian tick typhus
- C. Relapsing fever (Correct Answer)
- D. KFD
Explanation: ***Relapsing fever*** - **Soft ticks** (Ornithodoros species) are the primary vectors for **tick-borne relapsing fever**, specifically transmitting spirochetes of the genus *Borrelia*. - The disease is characterized by recurrent episodes of **fever**, **headache**, and **fatigue**, alternating with afebrile periods. *Tularemia* - While tularemia can be transmitted by ticks, it is primarily associated with **hard ticks** (e.g., Dermacentor, Amblyomma) and not typically soft ticks. - The causative agent is *Francisella tularensis*, which can also be acquired through contact with infected animals or contaminated water. *Indian tick typhus* - This is a form of spotted fever group rickettsiosis caused by *Rickettsia conorii*, typically transmitted by **hard ticks** like *Rhipicephalus sanguineus*. - It is characterized by fever, rash, and a characteristic **eschar** at the bite site. *KFD* - **Kyasanur Forest Disease (KFD)** is a viral hemorrhagic fever transmitted by **hard ticks**, particularly *Haemaphysalis spinigera*. - It is endemic to India and involves symptoms such as high fever, headache, and hemorrhage.
Question 5: A lady presented with fever and rashes. She returned from the USA and gives a history of exposure to ticks. Most probable diagnosis is
- A. Oraya fever
- B. Rocky mountain fever (Correct Answer)
- C. Scrub typhus
- D. Epidemic typhus
Explanation: ***Rocky mountain fever*** - **Rocky Mountain spotted fever (RMSF)** is a **tick-borne disease** caused by the bacterium *Rickettsia rickettsii*, characterized by **fever and rash**. - The patient's history of returning from the **USA** and **tick exposure** in the context of fever and rash makes RMSF the most probable diagnosis, as it is endemic to many regions of the Americas. *Oraya fever* - **Oraya fever** is caused by **Bartonella bacilliformis** and is characterized by acute hemolytic anemia and fever, with a rash appearing later in some cases. - It is geographically restricted to **Andean regions of Peru, Ecuador, and Colombia**, making it unlikely for a patient returning from the USA. *Scrub typhus* - **Scrub typhus** is a **mite-borne disease** caused by *Orientia tsutsugamushi*, presenting with fever, rash, and often an **eschar** [1]. - It is endemic to **Asia, Australia, and the Pacific Islands**, not typically associated with exposure in the USA [1]. *Epidemic typhus* - **Epidemic typhus** is caused by **Rickettsia prowazekii** and is typically transmitted by the **human body louse**, occurring in crowded, unsanitary conditions. - While it presents with fever and rash, the mode of transmission and typical epidemiological context (lice, crowded living) do not fit the presented case of tick exposure in the USA.
Question 6: Which of the following is the carrying agent for Lyme disease?
- A. Anopheles
- B. Ixodes scapularis ticks (Correct Answer)
- C. Louse
- D. Rat flea
Explanation: ***Ixodes scapularis ticks*** - *Ixodes scapularis* ticks (deer ticks) are the primary **vectors for Lyme disease** (caused by *Borrelia burgdorferi*) in North America [1]. - In Europe, *Ixodes ricinus* is the main vector for Lyme disease. - Lyme disease presents with characteristic **erythema migrans** rash, followed by potential neurological, cardiac, and arthritic complications [1]. - Lyme arthritis commonly affects large joints, particularly the **knee**, causing inflammatory arthritis [1]. *Anopheles* - **Anopheles mosquitoes** are the primary vectors for **malaria**, not Lyme disease [2]. - Malaria is caused by *Plasmodium* parasites and presents with fever, chills, and hemolytic anemia [2]. *Louse* - **Lice** are vectors for diseases such as **epidemic typhus** (caused by *Rickettsia prowazekii*) and **relapsing fever** (caused by *Borrelia recurrentis*) [3]. - They are not associated with the transmission of Lyme disease. *Rat flea* - **Rat fleas** (e.g., *Xenopsylla cheopis*) are the primary vectors for **bubonic plague** (caused by *Yersinia pestis*) and **murine typhus**. - These insects do not transmit Lyme disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 389-390. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 400. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 392-393.
Question 7: Chagas disease is transmitted by the following:
- A. Birds
- B. Kissing bugs (Correct Answer)
- C. Tsetse flies
- D. Dogs
Explanation: ***Kissing bugs*** - Chagas disease is primarily transmitted by the feces of infected **triatomine bugs**, commonly known as **kissing bugs**, which typically feed at night. - These bugs transmit the parasite *Trypanosoma cruzi* when they defecate near the bite wound or mucous membranes. *Birds* - Birds are not known vectors for the transmission of **Chagas disease**. - While some birds can carry other diseases, they do not carry the **triatomine bug** or the *Trypanosoma cruzi* parasite. *Tsetse flies* - **Tsetse flies** are the primary vectors for **African trypanosomiasis** (sleeping sickness), caused by *Trypanosoma brucei*. - They are not involved in the transmission of **Chagas disease** (*Trypanosoma cruzi*). *Dogs* - While dogs can be reservoirs for the *Trypanosoma cruzi* parasite and can become infected with **Chagas disease**, they are not directly responsible for transmitting the disease to humans. - Transmission to dogs and humans occurs through the bite of an infected **kissing bug**.
Question 8: A girl from Shimla presented to OPD with fever, hypotension, malaise and axillary and inguinal lymphadenopathy. Culture in glucose broth shows stalactite growth. Most likely causative organism is?
- A. Yersinia pestis (Correct Answer)
- B. Brucella abortus
- C. Coxiella burnetii
- D. Francisella tularensis
Explanation: ***Yersinia pestis*** - The combination of **fever**, **hypotension**, **malaise**, and **inguinal and axillary lymphadenopathy** (buboes) is highly characteristic of **bubonic plague**, caused by *Yersinia pestis*. - **Stalactite growth** in broth culture is a classic identifying feature of *Yersinia pestis* when incubated without agitation, due to the organism's **lipid A-modified LPS** which allows self-aggregation. *Brucella abortus* - *Brucella abortus* causes **brucellosis**, which presents with **undulant fever**, **arthralgia**, and **hepatosplenomegaly**, but typically not with prominent acute lymphadenopathy and hypotension to this degree. - While it is a **facultative intracellular pathogen**, it does not exhibit stalactite growth in glucose broth. *Coxiella burnetii* - *Coxiella burnetii* causes **Q fever**, which is characterized by **fever**, **headache**, and **pneumonia**, often without prominent lymphadenopathy. - It is an **obligate intracellular bacterium** and cannot be cultivated in standard glucose broth, much less show stalactite growth. *Francisella tularensis* - *Francisella tularensis* causes **tularemia**, which can manifest with **fever**, **lymphadenopathy** (ulceroglandular form), and **malaise**. - However, it typically requires **specialized culture media** like cysteine-enriched agar and does not exhibit stalactite growth in glucose broth.
Question 9: A farmer presents to the emergency department with painful inguinal lymphadenopathy and a history of fever and flu-like symptoms. Clinical examination reveals an ulcer on the leg. Which of the following stains should be used to detect suspected bipolar-stained organisms?
- A. Albe's stain
- B. McFadyean's stain
- C. Wayson's stain (Correct Answer)
- D. Ziehl-Neelsen stain
Explanation: ***Wayson's stain*** - This stain is specifically used for the detection of **Yersinia pestis**, the causative agent of **plague**, which often presents with **bipolar staining**. - Clinical features like **painful inguinal lymphadenopathy** (buboes), fever, flu-like symptoms, and an ulcer (possibly an inoculation site) are highly suggestive of **plague**. *Albe's stain* - **Albe's stain** is used for demonstrating **bacterial capsules**, not for bipolar-stained organisms. - It would not specifically identify **Yersinia pestis** in this context. *Mc Fayden's stain* - **McFadyen's stain** is primarily used to detect the capsule of **Bacillus anthracis** (anthrax) from smears. - While helpful for anthrax, it is not the specific stain for bipolar staining of **Yersinia pestis**. *Ziehl Nelson stain* - **Ziehl-Neelsen stain** is an **acid-fast stain** used to identify organisms with high mycolic acid content in their cell walls, such as **Mycobacterium tuberculosis**. - It is not suitable for visualizing gram-negative bacteria like **Yersinia pestis** or their bipolar staining characteristics.
Question 10: A militant presents with rashes all over his body sparing the palms and soles. On examination, he was febrile and lice were noted. Which of the following is responsible for his condition?
- A. Rickettsia typhi
- B. Rickettsia prowazekii (Correct Answer)
- C. Rickettsia akari
- D. Rickettsia conorii
Explanation: ***Rickettsia prowazekii*** - This bacterium is the causative agent of **epidemic typhus**, which is transmitted by the **body louse** (Pediculus humanus corporis), consistent with the presence of lice. - The characteristic rash of epidemic typhus **spares the palms and soles** and often begins on the trunk, spreading centrifugally. *Rickettsia typhi* - This organism causes **murine typhus**, which is transmitted by **fleas**, particularly those found on rodents. - While it can cause a rash that typically spares the palms and soles, the transmission vector and typical setting (exposure to rodents) do not fit the clinical scenario as well as **body lice**. *Rickettsia akari* - This bacterium causes **rickettsialpox**, transmitted by **mites**. - The rash of rickettsialpox is typically papulovesicular, and a characteristic **eschar** (or black scab) is usually present at the site of the mite bite, which is not mentioned in the case. *Rickettsia conorii* - This organism causes **Mediterranean spotted fever** (also known as Boutonneuse fever), transmitted by **ticks**. - A distinguishing feature of this infection is the presence of a **tache noire** (eschar) at the site of the tick bite, which is absent in the patient's presentation.
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