Onchocerciasis — MCQs
In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?
Name the parasite whose microfilariae have a sheath and no nuclei at the tail end.
Mass Drug Administration is NOT routinely used as the primary strategy for:
Which fungus is most commonly associated with orbital cellulitis in patients with diabetic ketoacidosis?
Which of the following features is characteristic of a fungal corneal ulcer?
Adult scabies is characterized by which of the following?
An 8-month-old child presented with itchy, exudative lesions on the face, palms, and soles. The siblings also have similar complaints. Which of the following is the treatment of choice?
An infant presents with papulovesicular lesions on the palms, soles, face, and trunk. What is the most likely diagnosis?
A 6-month-old infant presented with multiple erythematous papules and exudative lesions on the face, scalp, trunk, and a few vesicles on palms and soles for 2 weeks. The infant's mother has a history of itchy lesions. What is the most likely diagnosis?
A 10-year-old girl presents with multiple excoriations on her hands that have appeared over the past week. She reports itching and scratching her hands. Physical examination reveals multiple 0.2- to 0.6-cm linear streaks in the interdigital regions. The condition resolved with topical lindane lotion. Which of the following organisms is most likely responsible for these findings?
Onchocerciasis Indian Medical PG Practice Questions and MCQs
Question 1: In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?
- A. Bone marrow biopsy
- B. DEC provocation test
- C. Detection of microfilariae in the blood smear (Correct Answer)
- D. Ultrasound of the scrotum
Explanation: ***Detection of microfilariae in the blood smear*** - A positive **filarial antigen test** indicates the presence of adult worms, and the next step is to confirm active infection by identifying **microfilariae**. [1] - **Nocturnal blood samples** are crucial because microfilariae of *Wuchereria bancrofti* and *Brugia malayi* exhibit **nocturnal periodicity**, meaning they are most abundant in peripheral blood between 10 PM and 2 AM. [1] *Bone marrow biopsy* - This procedure is typically used to diagnose **hematological disorders**, such as leukemia or lymphoma, or investigate causes of unexplained fever, but it is not indicated for filariasis. - While filariasis can rarely lead to **eosinophilia**, a bone marrow biopsy is not a diagnostic tool for filarial infection itself. *DEC provocation test* - The **diethylcarbamazine (DEC) provocation test** is used to bring out microfilariae into the peripheral blood during the daytime for species that exhibit nocturnal periodicity. [1] - However, it carries a risk of severe adverse reactions due to rapid killing of microfilariae, especially in cases of heavy infection, and is generally avoided when antigen tests are positive. [1] *Ultrasound of the scrotum* - Scrotal ultrasound can detect the characteristic "filarial dance sign" (motile adult worms) in the **lymphatic vessels of the scrotum and epididymis**, confirming lymphatic filariasis. [2] - While useful for assessing advanced disease manifestations like **hydrocele**, it does not quantify microfilaremia or replace the need for microscopic confirmation of circulating microfilariae to guide treatment.
Question 2: Name the parasite whose microfilariae have a sheath and no nuclei at the tail end.
- A. Brugia malayi
- B. Loa loa
- C. Onchocerca volvulus
- D. Wuchereria bancrofti (Correct Answer)
Explanation: **Wuchereria bancrofti** - **Wuchereria bancrofti** microfilariae are characterized by the presence of a **sheath** and a **clear tail end** that is devoid of nuclei. - This morphology is a key feature used in the microscopic differentiation of W. bancrofti from other filarial species. *Brugia malayi* - **Brugia malayi** microfilariae also have a **sheath**, but their tail end typically contains **two distinct nuclei** that are spaced apart. - They are generally shorter and have more kinky curves than W. bancrofti. *Loa loa* - **Loa loa** microfilariae possess a **sheath** but are distinguished by their **nuclei extending to the tip** of the tail, often in a more continuous pattern. - They are also known for their diurnal periodicity, which aids in diagnosis. *Onchocerca volvulus* - **Onchocerca volvulus** microfilariae are **unsheathed** and have nuclei that do **not extend to the tail tip**, leaving a distinct clear space. - They are typically found in the skin and subcutaneous tissue, rather than the blood.
Question 3: 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 4: Which fungus is most commonly associated with orbital cellulitis in patients with diabetic ketoacidosis?
- A. Candida
- B. Mucor
- C. Rhizopus (Correct Answer)
- D. Aspergillus
Explanation: ***Rhizopus*** - *Rhizopus* is the most common cause of **mucormycosis** (also called zygomycosis), an aggressive fungal infection that frequently affects immunocompromised patients, especially those with **diabetic ketoacidosis (DKA)**. - *Rhizopus arrhizus* (formerly *R. oryzae*) accounts for approximately **70% of all mucormycosis cases**, making it the single most common causative organism. - In DKA, the acidic environment and high glucose levels favor the growth of **Mucorales fungi**, leading to rapid progression from the sinuses to the orbit and brain (rhinoorbital-cerebral mucormycosis). *Candida* - While *Candida* is a common cause of fungal infections, it typically manifests as **candidemia**, **esophagitis**, or **vulvovaginitis**, and is rarely associated with orbital cellulitis in DKA. - *Candida* infections are more likely in patients with indwelling catheters or those on broad-spectrum antibiotics, rather than specifically linked to DKA-induced orbital cellulitis. *Mucor* - The genus *Mucor* is part of the **Mucorales order** and can cause **mucormycosis** with identical clinical presentations to *Rhizopus*. - However, *Mucor* species account for only **10-20% of mucormycosis cases**, making *Rhizopus* the **most commonly** associated genus as asked in the question. - While both are clinically grouped under "mucormycosis," *Rhizopus* is the more specific and statistically correct answer when identifying the most common causative fungus. *Aspergillus* - *Aspergillus* species are common environmental fungi that can cause invasive infections, particularly in immunocompromised patients, leading to conditions like **aspergilloma** or **invasive aspergillosis**. - While *Aspergillus* can cause sinus and orbital infections, it is less commonly associated with the rapid, aggressive form of orbital cellulitis seen in DKA compared to mucormycosis caused by *Rhizopus*.
Question 5: Which of the following features is characteristic of a fungal corneal ulcer?
- A. The ulcer has feathery margins. (Correct Answer)
- B. Symptoms are more prominent than signs.
- C. The ulcer appears dry and grayish-white.
- D. The ulcer is associated with diffuse corneal edema.
Explanation: ***The ulcer has feathery margins.*** - **Feathery margins** with satellite lesions are the **most characteristic feature** of fungal corneal ulcers, representing fungal hyphae spreading through the corneal stroma in a branching pattern - This infiltrative pattern with irregular, feathery borders is considered **pathognomonic** for fungal keratitis and is a key diagnostic feature - The feathery appearance helps distinguish fungal from bacterial ulcers clinically *The ulcer appears dry and grayish-white.* - While fungal ulcers can have a dry, grayish-white appearance, this is **less specific** and can be seen in other conditions - This feature is supportive but not as characteristic as the feathery margins - The texture relates to the minimal suppuration typical of fungal infections *The ulcer is associated with diffuse corneal edema.* - Diffuse corneal edema is more characteristic of **severe bacterial keratitis** or endothelial dysfunction - Fungal ulcers typically have more **localized infiltrates** with relatively less surrounding edema - When edema occurs, it's usually proportionate to the depth of infiltration *Symptoms are more prominent than signs.* - This describes **viral keratitis** (especially herpes simplex), where severe pain and photophobia occur with subtle signs - In **fungal ulcers**, the visible signs are usually **prominent** and correlate well with symptom severity - The lesion itself is typically quite evident on examination
Question 6: 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.
Question 7: An 8-month-old child presented with itchy, exudative lesions on the face, palms, and soles. The siblings also have similar complaints. Which of the following is the treatment of choice?
- A. Systemic ampicillin
- B. Topical permethrin (Correct Answer)
- C. Systemic prednisolone
- D. Topical betamethasone
Explanation: ### Explanation **Diagnosis: Infantile Scabies** The clinical presentation of itchy, exudative lesions involving the **palms and soles**, combined with a **positive family history** (siblings affected), is pathognomonic for Scabies. In infants, unlike adults, the lesions frequently involve the face, scalp, palms, and soles and often present as vesicles or pustules due to secondary eczematization. **1. Why Topical Permethrin is Correct:** * **Permethrin (5% cream)** is the **drug of choice** for scabies in infants older than 2 months. * **Mechanism:** It acts by disrupting the sodium channel currents in the neurons of the *Sarcoptes scabiei* mite, leading to paralysis and death. * **Application:** It should be applied from head to toe in infants (including the face and scalp, avoiding eyes/mouth) and washed off after 8–12 hours. **2. Why Other Options are Incorrect:** * **Systemic Ampicillin:** While lesions may appear "exudative" due to secondary bacterial infection (impetiginization), the primary pathology is parasitic. Antibiotics alone will not cure the underlying infestation. * **Systemic Prednisolone & Topical Betamethasone:** These are corticosteroids. Using steroids in scabies is contraindicated as they mask the symptoms ("Scabies Incognito") and can worsen the infestation by suppressing the local immune response against the mites. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice in Pregnancy/Lactation:** Permethrin 5%. * **Ivermectin:** Oral ivermectin (200 µg/kg) is an alternative but is generally **avoided in children weighing <15 kg** or pregnant women. * **Nodular Scabies:** Characterized by reddish-brown itchy nodules in the axilla and genitalia; treated with intralesional steroids. * **Crusted (Norwegian) Scabies:** Seen in immunocompromised patients; characterized by thousands of mites and minimal itching. Requires combination therapy (Oral Ivermectin + Topical Permethrin). * **Key Management Rule:** Always treat all close contacts simultaneously, even if asymptomatic, to prevent re-infestation.
Question 8: An infant presents with papulovesicular lesions on the palms, soles, face, and trunk. What is the most likely diagnosis?
- A. Scabies (Correct Answer)
- B. Atopic dermatitis
- C. Urticaria
- D. Seborrheic dermatitis
Explanation: ### Explanation **Correct Answer: A. Scabies** The clinical presentation of papulovesicular lesions involving the **palms, soles, and face** in an infant is classic for **Infantile Scabies**. While scabies in adults typically spares the head and neck (due to the distribution of sebaceous glands), infants are an exception. In this age group, the infestation is often generalized, frequently involving the face, scalp, palms, and soles. The lesions are often inflammatory, presenting as vesicles, pustules, or nodules rather than the classic burrows seen in adults. **Why other options are incorrect:** * **Atopic Dermatitis:** While common in infants, it typically presents as erythematous, itchy, scaly patches on the cheeks and extensor surfaces. It rarely involves the palms and soles. * **Urticaria:** Presents as transient, evanescent wheals (hives) that migrate. It does not present as persistent papulovesicular lesions. * **Seborrheic Dermatitis:** Characterized by "cradle cap" (greasy yellow scales) on the scalp and involvement of skin folds (intertriginous areas). It is generally non-pruritic and does not affect the palms and soles. **High-Yield Clinical Pearls for NEET-PG:** * **Pathogen:** *Sarcoptes scabiei var. hominis*. * **Hallmark Sign:** The **Burrow** (S-shaped track), most commonly found in finger webs and wrist creases. * **Infantile Scabies Key Difference:** Involvement of the **face, scalp, palms, and soles** is a high-yield diagnostic pointer. * **Treatment of Choice:** Topical **Permethrin (5%)** cream. For infants under 2 months, **Precipitated Sulfur (6-10%)** is often preferred due to safety profiles. * **Nodular Scabies:** Persistent itchy nodules in the axilla or genitalia, representing a hypersensitivity reaction.
Question 9: A 6-month-old infant presented with multiple erythematous papules and exudative lesions on the face, scalp, trunk, and a few vesicles on palms and soles for 2 weeks. The infant's mother has a history of itchy lesions. What is the most likely diagnosis?
- A. Scabies (Correct Answer)
- B. Infantile eczema (atopic dermatitis)
- C. Infantile seborrheic dermatitis
- D. Impetigo contagiosa
Explanation: ### Explanation **Correct Answer: A. Scabies** The clinical presentation is classic for **Infantile Scabies**. Unlike adults, where scabies typically spares the head and neck, infants frequently present with involvement of the **face, scalp, palms, and soles**. The presence of **vesicles** on the palms and soles is a high-yield diagnostic clue in this age group. Furthermore, the history of itchy lesions in the mother (a close contact) strongly points toward a contagious parasitic infestation. **Why other options are incorrect:** * **Infantile Eczema (Atopic Dermatitis):** While it involves the face and trunk with exudative lesions, it typically **spares the diaper area** and rarely presents with discrete vesicles on the palms and soles. There is usually a family history of atopy rather than a history of acute contagious itching. * **Infantile Seborrheic Dermatitis:** This presents with greasy, yellow scales (cradle cap) on the scalp and flexures. It is generally **non-itchy** and does not present with palmoplantar vesicles. * **Impetigo Contagiosa:** This is a superficial bacterial infection characterized by honey-colored crusts. While it can complicate scabies (secondary infection), it would not explain the widespread distribution and the mother’s symptoms. **NEET-PG High-Yield Pearls:** * **Pathognomonic sign:** The **Burrow** (S-shaped track), though often difficult to find in infants due to secondary eczematization or infection. * **Nodular Scabies:** Common in infants; occurs on the axillae and groin as a hypersensitivity reaction. * **Treatment of Choice:** **Permethrin 5% cream** (applied from head to toe in infants). * **Alternative:** Oral Ivermectin (only for children >15 kg or >5 years old). * **Key Rule:** Always treat all close household contacts simultaneously to prevent re-infestation.
Question 10: A 10-year-old girl presents with multiple excoriations on her hands that have appeared over the past week. She reports itching and scratching her hands. Physical examination reveals multiple 0.2- to 0.6-cm linear streaks in the interdigital regions. The condition resolved with topical lindane lotion. Which of the following organisms is most likely responsible for these findings?
- A. Ixodes scapularis
- B. Poxvirus
- C. Staphylococcus aureus
- D. Sarcoptes scabiei (Correct Answer)
Explanation: ### Explanation **Correct Answer: D. Sarcoptes scabiei** The clinical presentation is classic for **Scabies**, caused by the mite *Sarcoptes scabiei* var. *hominis*. The pathognomonic sign described—**linear streaks** (0.2 to 0.6 cm)—represents **burrows** created by the female mite as she tunnels through the stratum corneum to lay eggs. * **Key Diagnostic Features:** Intense nocturnal pruritus (a Type IV hypersensitivity reaction to mite feces/saliva) and predilection for "sites of election" such as the **interdigital webs**, flexor wrists, axillae, and genitalia. * **Treatment:** While the question mentions Lindane (an organochlorine), the current first-line treatment is **Topical Permethrin (5%)**. --- ### Why the other options are incorrect: * **A. Ixodes scapularis:** This is the deer tick, the vector for Lyme disease. It typically presents with *Erythema Chronicum Migrans* (a "bull’s-eye" rash), not interdigital burrows. * **B. Poxvirus:** Specifically, Molluscum Contagiosum is caused by a poxvirus. It presents as firm, umbilicated, pearly papules, not linear burrows or excoriations. * **C. Staphylococcus aureus:** This is a common cause of secondary bacterial infections (impetiginization) in scabies patients, but it does not cause the primary linear lesions described. --- ### High-Yield NEET-PG Pearls: 1. **Burrow Identification:** The "Ink test" (applying fountain pen ink to the lesion) can help visualize the burrow. 2. **Nodular Scabies:** A variant seen in children, often involving the scrotum or axillae; these are hypersensitivity nodes that persist after the mites are eradicated. 3. **Crusted (Norwegian) Scabies:** Seen in immunocompromised or elderly patients; characterized by thousands of mites and thick crusts, but often **minimal itching**. 4. **Treatment Protocol:** Treat the **entire family/close contacts** simultaneously to prevent re-infestation. Permethrin should be applied from the neck down and left for 8–12 hours.
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