Myiasis — MCQs
Following are larval control measures, except:
In a rural clinic, a 3-year-old girl child is brought by her mother and is emaciated. Her hemoglobin was 5 g/dL. The girl also has edema over her knees and ankles with discrete rash on her knees, ankles and elbows. The most likely worm infestation causing these manifestations is:
Sandfly acts as a vector to all of the following diseases, except which of the following?
Cutaneous larva migrans is caused by which organism?
Which of the following statements is true regarding amoebic liver abscess?
In Guinea worm prophylaxis, all are true, except -
A child presented with perianal itching. The swab specimen is shown in the image. What is the diagnosis?
A 65-year old man presented with skin lesions on his chest and left arm and shoulder six weeks after returning from a vacation in Belize at the beach in the rain forest. The lesions occasionally stung, drained a dark exudates, and enlarged despite two weeks of treatment with cephalexin. The patient had no constitutional symptoms. Physical examination revealed five nodules of varying sizes with surrounding erythema and a central pore through which a single, moving larva was observed. The larvae coming out of the pores are-
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
Which of the following statements is not correct regarding sebaceous cyst?
Myiasis Indian Medical PG Practice Questions and MCQs
Question 1: Following are larval control measures, except:
- A. DDT (Correct Answer)
- B. Gambusia
- C. Intermittent irrigation
- D. Paris green
Explanation: ***DDT*** - **DDT (dichlorodiphenyltrichloroethane)** is primarily classified as an **adulticide** in vector control programs, used mainly for **indoor residual spraying** to kill adult mosquitoes. - While DDT can kill larvae when applied to water, it is **not typically categorized as a larval control measure** in public health practice due to environmental concerns and its primary use against adult vectors. - Its mechanism involves interfering with the **nervous system** of insects, causing paralysis and death. *Paris green* - **Paris green** is a chemical compound historically used as a **larvicide**, particularly effective against **Anopheles larvae** in stagnant water. - It works as a **stomach poison** for larvae when ingested during feeding, making it a specific larval control agent. *Gambusia* - **Gambusia**, also known as **mosquitofish**, are small fish that feed on mosquito larvae, making them a **biological control measure** for larval populations. - They are often introduced into ponds, ditches, and other water bodies to naturally reduce larval numbers. *Intermittent irrigation* - **Intermittent irrigation** is an **environmental manipulation method** that involves draining and refilling water sources at regular intervals, effectively destroying **larval breeding sites**. - This method prevents larvae from completing their development cycle by eliminating the aquatic environment they depend on.
Question 2: In a rural clinic, a 3-year-old girl child is brought by her mother and is emaciated. Her hemoglobin was 5 g/dL. The girl also has edema over her knees and ankles with discrete rash on her knees, ankles and elbows. The most likely worm infestation causing these manifestations is:
- A. Roundworm
- B. Pinworm
- C. Whipworm
- D. Hookworm (Correct Answer)
Explanation: ***Hookworm*** - **Hookworm infection** (Ancylostoma duodenale/Necator americanus) leads to chronic blood loss from the intestines, causing **microcytic hypochromic anemia** and **severe emaciation** due to persistent nutrient loss and malabsorption. - The combination of severe **anemia (Hb 5 g/dL)**, **emaciation**, and **edema** (due to **hypoalbuminemia**, a consequence of protein-losing enteropathy and poor nutrition) is highly characteristic of hookworm infestation in children. - The **discrete rash** on pressure points (knees, ankles, elbows) may represent **ground itch** (pruritic papulovesicular rash at larval penetration sites) or dermatitis secondary to malnutrition and edema. *Roundworm* - **Ascaris lumbricoides** can cause malnutrition and growth delays, but typically does not lead to the severe anemia and edema seen here unless there is a massive infestation leading to intestinal obstruction or biliary obstruction. - Its primary impact is often related to **nutrient competition** and mechanical obstruction, not significant blood loss. *Pinworm* - **Enterobius vermicularis** (pinworm) infection primarily causes **perianal itching**, especially at night. - It does not typically cause systemic symptoms like **severe anemia**, **emaciation**, or **edema**, as it does not feed on blood or cause significant nutrient malabsorption. *Whipworm* - **Trichuris trichiura** (whipworm) can cause chronic dysentery, **rectal prolapse**, and **anemia** in heavy infections due to blood loss. - While it can contribute to **growth retardation** and anemia, it is less likely to cause the profound emaciation and edema described compared to hookworm, especially with a hemoglobin level of 5 g/dL, which points strongly to major chronic blood loss.
Question 3: Sandfly acts as a vector to all of the following diseases, except which of the following?
- A. Kala-azar
- B. Pappataci fever
- C. Onchocerciasis (Correct Answer)
- D. Leishmaniasis
Explanation: ***Onchocerciasis*** - **Onchocerciasis**, or river blindness, is transmitted by the **blackfly (Simulium species)**, not the sandfly. - The disease is caused by the filarial nematode *Onchocerca volvulus*, which is introduced into humans through the bite of an infected blackfly. *Pappataci fever* - **Pappataci fever**, also known as sandfly fever, is a viral disease transmitted by the bite of infected **sandflies (Phlebotomus species)**. - This disease is characterized by a sudden onset of fever, headache, and muscle pain. *Kala-azar* - **Kala-azar**, or visceral leishmaniasis, is a severe form of **leishmaniasis** transmitted by the bite of an infected female **sandfly (Phlebotomus species)**. - It is caused by intracellular parasites of the genus *Leishmania* and affects internal organs. *Leishmaniasis* - **Leishmaniasis** in its various forms (cutaneous, mucocutaneous, visceral) is transmitted by the bite of an infected female **sandfly**. - The sandfly acts as the definitive host and vector for the *Leishmania* parasites.
Question 4: Cutaneous larva migrans is caused by which organism?
- A. Strongyloides
- B. Toxocara canis
- C. Ancylostoma braziliense (Correct Answer)
- D. Necator americanus
Explanation: ***Ancylostoma braziliense*** - This **hookworm** species commonly found in dogs and cats is the most frequent cause of **cutaneous larva migrans** in humans. - The larvae penetrate the skin but cannot complete their life cycle in humans, instead migrating aimlessly creating **serpiginous tracks**. *Strongyloides* - **_Strongyloides stercoralis_** causes **strongyloidiasis**, which presents with a rapidly advancing (up to 10 cm/hr) migratory rash known as **larva currens**, and not the slower cutaneous larva migrans. - It differs from cutaneous larva migrans in its ability to complete its life cycle in humans, leading to **autoinfection**. *Toxocara canis* - **_Toxocara canis_** is the causative agent of **visceral larva migrans** and **ocular larva migrans**, not cutaneous larva migrans. - In visceral larva migrans, larvae migrate through internal organs, causing symptoms like **hepatomegaly** and **eosinophilia**. *Necator americanus* - This is a human hookworm that can cause **iron deficiency anemia** due to chronic blood loss in the intestines. - While its larvae can penetrate the skin, causing a transient itchy rash known as **ground itch**, they do not cause the prolonged, migratory cutaneous larva migrans.
Question 5: Which of the following statements is true regarding amoebic liver abscess?
- A. May rupture into the pleural cavity.
- B. Mostly involving the right lobe of the liver. (Correct Answer)
- C. For asymptomatic luminal carriers, metronidazole is the drug of choice.
- D. Multiple abscesses is less common than a single abscess.
Explanation: ***Mostly involving the right lobe of the liver*** - The **right lobe** of the liver is the most common site for an amoebic liver abscess due to its larger size and preferential blood flow from the portal venous system, which drains the intestines where *Entamoeba histolytica* resides. - The **superior mesenteric vein**, draining the cecum and ascending colon (common sites for amebiasis), primarily feeds the right hepatic lobe. *May rupture into the pleural cavity* - While rupture can occur, the **peritoneal cavity** is a more common site of rupture for amoebic liver abscesses. - Rupture into the pleural cavity or lung is less frequent but can lead to **empyema** or **bronchopleural fistula** [1]. *For asymptomatic luminal carriers, metronidazole is the drug of choice* - **Metronidazole** is effective against invasive amoebiasis (like liver abscess or dysentery) but is not the drug of choice for asymptomatic luminal carriers. - For **asymptomatic luminal carriers**, **luminal amebicides** such as **paromomycin** or **diloxanide furoate** are used to eradicate cysts from the intestine [1]. *Multiple abscesses is less common than a single abscess* - **A single amoebic liver abscess** is more common than multiple abscesses [1]. - Multiple abscesses are typically seen in disseminated disease or immunocompromised individuals, though even then a solitary lesion is more frequent.
Question 6: In Guinea worm prophylaxis, all are true, except -
- A. Identification of carriers
- B. Mass treatment with anti-helminthic drugs (Correct Answer)
- C. Acute search of new cases
- D. Health education to people to use a sieve for straining drinking water
Explanation: ***Mass treatment with anti-helminthic drugs*** - Guinea worm disease (Dracunculiasis) is caused by the parasite *Dracunculus medinensis*, which is transmitted through contaminated drinking water containing **copepods (water fleas)** harboring larvae. - Unlike many other helminthic infections, Guinea worm disease **does not respond to anti-helminthic drugs** for treatment or prevention, making mass treatment ineffective. *Identification of carriers* - Identifying and containing individuals who are actively expelling worms is crucial to prevent further contamination of water sources. - This strategy focuses on interrupting the parasite's life cycle by preventing infected individuals from entering communal water bodies. *Acute search of new cases* - Active surveillance and rapid detection of new cases enable prompt intervention, such as safe containment of the emerging worm and prevention of water source contamination. - This helps in monitoring incidence and targeting interventions effectively to achieve eradication. *Health education to people to use a sieve for straining drinking water* - This is a cornerstone of Guinea worm prophylaxis, as it directly addresses the mode of transmission by filtering out the **copepods** from drinking water. - Providing **cloth filters** or using fine-mesh sieves is a simple and effective way to ensure safe drinking water and interrupt the life cycle.
Question 7: A child presented with perianal itching. The swab specimen is shown in the image. What is the diagnosis?
- A. Enterobius (Correct Answer)
- B. Ascaris
- C. Trichiura
- D. Ancylostoma
Explanation: ***Enterobius*** - The image shows **D-shaped** (plano-convex) and **transparent eggs**, which are characteristic of *Enterobius vermicularis* (**pinworm** or **threadworm**). - **Perianal itching**, especially at night, is the hallmark symptom due to the female worm migrating to the perianal region to lay eggs. *Ascaris* - *Ascaris lumbricoides* eggs are typically **round to oval**, with a thick, mamillated (bumpy) outer shell, or smooth in the case of decorticated eggs, which is different from the eggs pictured. - Infection with *Ascaris* can cause pulmonary symptoms (Loeffler's syndrome) and intestinal obstruction, but not typically perianal itching. *Trichiura* - *Trichuris trichiura* (**whipworm**) eggs are distinctly **barrel-shaped** with prominent **polar plugs** at each end, which is not seen in the image. - Whipworm infection is often associated with bloody diarrhea, rectal prolapse, and growth retardation, not primarily perianal itching. *Ancylostoma* - *Ancylostoma duodenale* and *Necator americanus* (hookworms) eggs are typically **oval** with a **thin shell** and segmented embryo (morula stage) within, which lacks the distinct D-shape and transparency of the pictured eggs. - Hookworm infection primarily causes iron-deficiency anemia and can lead to cutaneous larva migrans, not perianal itching as a primary symptom.
Question 8: A 65-year old man presented with skin lesions on his chest and left arm and shoulder six weeks after returning from a vacation in Belize at the beach in the rain forest. The lesions occasionally stung, drained a dark exudates, and enlarged despite two weeks of treatment with cephalexin. The patient had no constitutional symptoms. Physical examination revealed five nodules of varying sizes with surrounding erythema and a central pore through which a single, moving larva was observed. The larvae coming out of the pores are-
- A. Loa loa
- B. Diphyllobothrium latum
- C. Dermatobia hominis (Correct Answer)
- D. Dracunculus medinensis
Explanation: ***Dermatobia hominis*** - The description of **cutaneous nodules** with a central pore from which a **moving larva** is observed, particularly after travel to a tropical region like Belize, is classic for **furuncular myiasis** caused by **Dermatobia hominis** larvae (human botfly). - The **"occasional stinging"** and **"dark exudate"** are characteristic symptoms of the larva burrowing in the skin and secreting waste products. *Loa loa* - **Loa loa** (African eye worm) is a filarial nematode that migrates through **subcutaneous tissues** and occasionally across the eye, causing **Calabar swellings**. - It does not present as a **furuncular lesion** with a visible central moving larva emerging from a pore. *Diphyllobothrium latum* - **Diphyllobothrium latum** is a **tapeworm** that infects the intestines and is acquired by consuming undercooked infected fish. - It causes gastrointestinal symptoms and can lead to **vitamin B12 deficiency**, but it does not produce **skin lesions with moving larvae**. *Dracunculus medinensis* - **Dracunculus medinensis** (guinea worm) infection typically results in a **painful blister** on the lower limbs, from which the female worm emerges to release larvae when exposed to water. - While it involves a skin lesion, the presentation of **multiple nodules with a central pore revealing a moving larva** is not consistent with **dracunculiasis**.
Question 9: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 10: Which of the following statements is not correct regarding sebaceous cyst?
- A. Found on hairy areas of the body
- B. Treatment is incision and drainage (Correct Answer)
- C. Not found on palms and soles
- D. It has a punctum
Explanation: ***Treatment is incision and drainage*** - The standard treatment for a sebaceous cyst (more accurately an **epidermoid cyst** or **pilar cyst**) is **surgical excision** of the entire cyst wall to prevent recurrence. - **Incision and drainage** only provides temporary relief by emptying the contents but leaves the cyst wall intact, leading to a high chance of the cyst refilling. *Found on hairy areas of the body* - This statement is generally correct as sebaceous cysts often arise from hair follicles and are common in **hair-bearing areas** like the scalp, face, neck, and trunk. - They occur due to the accumulation of **sebum** and keratin within a blocked or damaged sebaceous gland or hair follicle. *Not found on palms and soles* - This statement is correct because **palms and soles** generally **lack sebaceous glands** and hair follicles, hence sebaceous cysts are typically not found in these locations. - Cysts found in these areas are more likely to be **ganglion cysts** or other types of epidermal inclusion cysts. *It has a punctum* - This statement is often correct; many sebaceous cysts (especially epidermoid cysts) have a visible **central punctum** which represents the occluded pore from which the cyst originated. - This punctum is a **key diagnostic feature** and can sometimes exude a cheesy, foul-smelling material.
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