Ectoparasitic Infestations — MCQs
Which among the following occupations is a risk factor for cutaneous larva migrans?
Which of the following statements about scabies is false?
Pathognomonic lesion of scabies is?
Mass Drug Administration is NOT routinely used as the primary strategy for:
A man presents with fever and chills 2 weeks after a louse bite. There was maculo-papular rash on the trunk which spread peripherally. The cause of this infection can be -
Ivermectin is indicated in the treatment of:
What is the average number of mites found on the body in a person suffering from regular scabies?
Which of the following statements about pediculosis pubis is MOST accurate?
The burrow in scabies is in
Adult scabies is characterized by which of the following?
Ectoparasitic Infestations Indian Medical PG Practice Questions and MCQs
Question 1: Which among the following occupations is a risk factor for cutaneous larva migrans?
- A. A poultry worker
- B. A kennel worker
- C. A lifeguard in a swimming pool
- D. Farmer (Correct Answer)
Explanation: ***Farmer*** - Farmers are at high risk due to frequent direct contact with **contaminated soil** or sandy environments where animal feces, especially from dogs and cats, might be present. - Exposure to **larvae of hookworms** such as *Ancylostoma braziliense* and *Ancylostoma caninum*, which can penetrate unprotected skin (e.g., bare feet while working) from the soil. *A lifeguard in a swimming pool* - Lifeguards primarily work in **chlorinated water** or on clean, well-maintained pool decks, which do not typically harbor hookworm larvae. - While they might be exposed to other skin conditions, **cutaneous larva migrans** is not a common risk associated with this occupation. *A poultry worker* - Poultry workers are primarily exposed to avian environments, where hookworm species that cause cutaneous larva migrans in humans are typically **not found**. - Their work environment generally does not involve direct contact with soil contaminated by **canine or feline feces**. *A kennel worker* - While kennel workers handle dogs and cats, which are carriers of hookworms, their primary exposure is to the animals themselves or their immediate cleaned environments, not typically **soil contaminated with larvae**. - The mode of transmission for cutaneous larva migrans is through **soil contact** rather than direct animal handling in a controlled kennel setting.
Question 2: Which of the following statements about scabies is false?
- A. Scabies is caused by the mite Sarcoptes scabiei
- B. Not exclusively transmitted sexually.
- C. Erythematous papules develop due to delayed type 4 hypersensitivity.
- D. Pruritus is predominantly absent. (Correct Answer)
Explanation: ***Pruritus is predominantly absent.*** - This statement is false because **pruritus (itching)** is the **hallmark symptom** of scabies and is almost always present, often severe and worse at night. - The intense itching is caused by an **allergic reaction** to the mites, their eggs, and their feces. *Not exclusively transmitted sexually.* - This statement is true; while scabies can be transmitted sexually through **skin-to-skin contact**, it can also spread through **non-sexual close physical contact** with an infected person or contaminated items like bedding. - Transmission requires **prolonged skin-to-skin contact**, not just a brief touch. *Scabies is caused by the mite Sarcoptes scabiei* - This statement is true; the parasitic mite **_Sarcoptes scabiei_ var. _hominis_** is the causative agent of human scabies. - The female mite burrows into the **epidermis** to lay eggs, leading to characteristic lesions and symptoms. *Erythematous papules develop due to delayed type 4 hypersensitivity.* - This statement is true; the **erythematous papules**, vesicles, and intense itching associated with scabies are a result of a **delayed type IV hypersensitivity reaction** to the mite, its feces, and eggs. - The immune response typically develops **3-6 weeks** after primary exposure.
Question 3: Pathognomonic lesion of scabies is?
- A. Burrow (Correct Answer)
- B. Pits
- C. Vesicle
- D. Papules
Explanation: ***Burrow*** - A **burrow** is a short, wavy, thread-like lesion, typically a few millimeters long, caused by the female **Sarcoptes scabiei mite** tunneling into the stratum corneum of the skin. - It is considered the **pathognomonic lesion** of scabies, meaning its presence is highly characteristic and diagnostic of the infestation. *Pits* - **Pits** are depressions in the skin or nails, often associated with conditions like **psoriasis** or certain fungal infections, but not scabies. - They are not formed by parasitic tunneling and lack the linear, raised appearance characteristic of a scabies burrow. *Vesicle* - A **vesicle** is a small, fluid-filled blister, which can be present in some forms of scabies, particularly in infants or crusted scabies. - While vesicles can be associated with scabies, they are a secondary finding and not the unique primary lesion (burrow) that is pathognomonic. *Papules* - **Papules** are small, raised bumps that can be seen in scabies due to an inflammatory response to the mites, their feces, and eggs. - While common, papules are a non-specific finding and can occur in many other skin conditions, making them not pathognomonic for scabies.
Question 4: Mass Drug Administration is NOT routinely used as the primary strategy for:
- A. Vitamin A Deficiency
- B. Scabies (Correct Answer)
- C. Lymphatic Filariasis
- D. Worm infestation
Explanation: ***Scabies*** - While **mass drug administration with oral ivermectin** has shown effectiveness in specific endemic outbreak settings, MDA is generally **not the primary recommended strategy** for routine scabies control in most public health contexts. - Scabies control typically prioritizes **case finding, contact tracing, simultaneous household treatment, and environmental decontamination**—which are more complex to implement than standard MDA programs. - Unlike the other conditions listed, scabies lacks well-established **routine MDA programs** at the scale of national public health initiatives, making it the least suitable option for MDA among these choices. *Vitamin A Deficiency* - **Vitamin A supplementation** through MDA is a **highly effective and widely implemented** WHO-recommended strategy to combat Vitamin A deficiency in at-risk populations, particularly children under 5 years. - Regular mass supplementation helps prevent **xerophthalmia** and reduces morbidity and mortality from infectious diseases. - This is a cornerstone of routine public health programs globally. *Lymphatic Filariasis* - **Lymphatic filariasis** is a classic example where MDA with anti-filarial drugs like **diethylcarbamazine (DEC), albendazole,** or **ivermectin** is the cornerstone strategy for interrupting transmission. - MDA is the **primary WHO-recommended approach** to achieve elimination of lymphatic filariasis, with established national programs in endemic countries. *Worm infestation* - **Mass deworming programs** using drugs like **albendazole** or **mebendazole** represent highly effective and well-established forms of MDA for controlling **soil-transmitted helminth infections**. - These routine programs significantly reduce disease burden in school-aged children, improving nutritional status, growth, and learning outcomes.
Question 5: A man presents with fever and chills 2 weeks after a louse bite. There was maculo-papular rash on the trunk which spread peripherally. The cause of this infection can be -
- A. Endemic typhus
- B. Rickettsial pox
- C. Epidemic typhus (Correct Answer)
- D. Scrub typhus
Explanation: ***Epidemic typhus*** - **Epidemic typhus** is caused by **Rickettsia prowazekii** and transmitted by the **human body louse (Pediculus humanus corporis)**, consistent with the history of a louse bite. - The classic presentation includes **fever, chills**, and a **maculopapular rash** that starts on the trunk and spreads centrifugally, sparing the palms and soles [1]. *Endemic typhus* - **Endemic typhus** (murine typhus) is caused by **Rickettsia typhi** and transmitted by the **rat flea**, not a louse [1]. - While it also presents with fever and rash, the distinct vector and, typically, milder course differentiate it from epidemic typhus. *Rickettsial pox* - **Rickettsialpox** is caused by **Rickettsia akari** and transmitted by the **mite** from house mice, not a louse. - It is characterized by an **eschar** at the bite site followed by a generalized papulovesicular rash, which is different from the maculopapular rash described. *Scrub typhus* - **Scrub typhus** is caused by **Orientia tsutsugamushi** and transmitted by the **chigger mite** larvae, not a louse [1]. - Similar to rickettsialpox, it typically presents with an **eschar** at the bite site and can cause generalized rash, but the vector is different [1].
Question 6: Ivermectin is indicated in the treatment of:
- A. Scabies (Correct Answer)
- B. Dermatophytosis
- C. Tuberculosis
- D. Syphilis
Explanation: ***Scabies*** - **Ivermectin** is an effective oral antiparasitic agent used to treat **scabies**, particularly in cases of widespread infestation, crusted scabies, or when topical treatments fail. - It acts by paralyzing and killing the **Sarcoptes scabiei mites** responsible for the infestation. *Dermatophytosis* - **Dermatophytosis** (ringworm) is a **fungal infection** of the skin, hair, or nails. - It is typically treated with **antifungal medications** (e.g., azoles, terbinafine), not ivermectin. *Tuberculosis* - **Tuberculosis** is a bacterial infection caused by **Mycobacterium tuberculosis**, primarily affecting the lungs. - Treatment involves a multi-drug regimen of **antibiotics** (e.g., rifampin, isoniazid), for several months. *Syphilis* - **Syphilis** is a sexually transmitted bacterial infection caused by **Treponema pallidum**. - The primary treatment for syphilis is **penicillin**, usually administered via injection.
Question 7: What is the average number of mites found on the body in a person suffering from regular scabies?
- A. 1 to 5
- B. 15 - 20
- C. 3
- D. 10 to 15 (Correct Answer)
Explanation: ***10 to 15*** - In **classic scabies**, the average number of **Sarcoptes scabiei** mites present on the host's body typically ranges from 10 to 15. - This relatively low number of mites is responsible for the intense **pruritus** and characteristic rash due to the host's immune response to mite antigens and waste products. *1 to 5* - While a very small number of mites might be present in the **early stages** of infestation, an average of 1 to 5 is generally too low for a full-blown symptomatic case of **classic scabies**. - A lower mite count is more typical of **atypical presentations** or infestations in partially treated individuals. *15 - 20* - This range is slightly higher than the typical average reported for **classic scabies**, though still within a reasonable, albeit less common, variation. - A significantly higher number of mites, into the thousands or millions, is characteristic of **crusted (Norwegian) scabies**, a much more severe form of the disease. *3* - Three mites represent a very low burden for a person with **classic scabies**. - Although the total number of mites is often small, an average of three significantly underestimates the typical infestation load that causes widespread itching and rash.
Question 8: Which of the following statements about pediculosis pubis is MOST accurate?
- A. Eggs (nits) attached to hair shafts confirm diagnosis (Correct Answer)
- B. It commonly infests scalp hair
- C. It requires systemic antibiotic treatment
- D. It is more contagious than other types of lice
Explanation: ***Eggs (nits) attached to hair shafts confirm diagnosis*** - The presence of **nits (eggs)** firmly attached to the hair shafts, particularly in the pubic region, is a **definitive diagnostic criterion** for pediculosis pubis. - These nits are typically oval, white or grayish, and cannot be easily removed, distinguishing them from dandruff. *It commonly infests scalp hair* - **Pediculosis pubis**, caused by *Pthirus pubis* (pubic louse or crab louse), primarily infests **coarse body hair**, most commonly in the pubic area. - **Scalp hair** is typically infested by *Pediculus humanus capitis* (head louse), which is a different species. *It requires systemic antibiotic treatment* - Pediculosis pubis is caused by an **ectoparasite** (louse), not a bacterial infection, and therefore does not require **systemic antibiotic treatment**. - Treatment involves topical insecticides like permethrin or malathion, and physical removal of lice and nits. *It is more contagious than other types of lice* - All types of lice are **highly contagious**, but pediculosis pubis is primarily transmitted through **sexual contact** or close bodily contact, making it a sexually transmitted infection (STI). - While easily spread, there is no evidence to suggest it is inherently more contagious than head lice, which spread easily through casual contact, especially among children.
Question 9: The burrow in scabies is in
- A. S. corneum (Correct Answer)
- B. Malpighian layer
- C. S. germinatum
- D. S. granulosum
Explanation: ***S. corneum*** - The **burrow** created by the *Sarcoptes scabiei* mite is specifically found within the **stratum corneum** of the epidermis. - This superficial location allows the mite to feed on **keratinocytes** and deposit eggs, leading to the characteristic rash and intense itching. - The burrow appears as a **serpiginous tract** and is a pathognomonic finding in scabies. *Malpighian layer* - The **Malpighian layer** encompasses the **stratum basale** and **stratum spinosum**, which are deeper layers of the epidermis. - The scabies mite does not burrow into these deeper, metabolically active layers. *S. germinatum* - **Stratum germinativum** is another term for the **stratum basale**, the deepest epidermal layer responsible for cell division. - The scabies mite creates burrows at a much more superficial level in the stratum corneum. *S. granulosum* - The **stratum granulosum** lies between the stratum spinosum and stratum corneum. - While closer to the surface than the Malpighian layer, scabies burrows are specifically located in the more superficial **stratum corneum**, not the granulosum layer.
Question 10: Adult scabies is characterized by which of the following?
- A. Involvement of palms and soles (Correct Answer)
- B. Involvement of the face
- C. Involvement of the anterior abdomen
- D. All of the above
Explanation: **Explanation:** Scabies is a contagious skin infestation caused by the mite *Sarcoptes scabiei var. hominis*. The distribution of lesions is the most critical diagnostic feature in NEET-PG questions. **1. Why Option A is Correct:** In **adult scabies**, the "Circle of Hebra" defines the classic distribution. This includes the interdigital spaces, wrists, elbows, axillae, periumbilical area, and genitalia. While traditionally taught that palms and soles are spared in adults compared to infants, modern clinical dermatology (and standard textbooks like IADVL) recognizes that **palms and soles** are frequently involved in adults, especially in cases of high mite burden or crusted scabies. Among the given options, it is the most characteristic site of involvement. **2. Why Options B and C are Incorrect:** * **Option B (Face):** The face and scalp are characteristically **spared** in adult scabies. This is because adults have a higher density of sebaceous glands; the sebum is thought to be inhibitory to the mites. Facial involvement is a hallmark of **infantile scabies** or **crusted (Norwegian) scabies**. * **Option C (Anterior Abdomen):** While the periumbilical area is involved, "anterior abdomen" is too broad and less specific than the involvement of the palms/soles or the web spaces. **Clinical Pearls for NEET-PG:** * **Infantile Scabies:** Unlike adults, infants show involvement of the **face, scalp, palms, and soles** with common secondary vesicopustules. * **Pathognomonic Sign:** The **Burrow** (a S-shaped track) is the clinical hallmark, most commonly found on the finger webs and wrists. * **Nocturnal Pruritus:** Itching is worst at night due to a Type IV hypersensitivity reaction to the mite, its eggs, and scybala (feces). * **Treatment of Choice:** Topical **Permethrin (5%)** is the gold standard. Oral Ivermectin (200 µg/kg) is an alternative or adjunct for crusted scabies.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free