Parasitology Practice Questions

Q: Trichomoniasis is transmitted through which stage?

Trophozoite. ### Explanation **Correct Answer: D. Trophozoite** **Medical Concept:** *Trichomonas vaginalis* is a flagellated protozoan that is unique because it **exists only in the trophozoite stage**. Unlike most intestinal protozoa (like *Entamoeba* or *Giardia*), it does not possess a cyst stage in its life cycle. Since there is no cyst to protect the organism from environmental stress, it is primarily transmitted through direct mucosal contact—most commonly via sexual intercourse. The pear-shaped, motile trophozoite is both the **infective stage** and the **diagnostic stage**. **Why the other options are incorrect:** * **A. Cyst:** While cysts are the infective stage for many protozoa (e.g., *E. histolytica*), *Trichomonas* does not form cysts. This is why it cannot survive long outside the human host. * **B. Oocyst:** This stage is characteristic of Apicomplexan parasites like *Cryptosporidium*, *Cyclospora*, and *Toxoplasma*. * **C. Sporozoite:** This is the infective stage for *Plasmodium* (Malaria), transmitted via the bite of an infected female Anopheles mosquito. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Causes a foul-smelling, **frothy, yellowish-green vaginal discharge** and vulvar irritation. * **Strawberry Cervix:** Colposcopy may reveal punctate hemorrhages on the cervix (Cervicitis emphysematosa), a classic board-exam finding. * **Diagnosis:** The gold standard is **Whiff test** (KOH) and **Wet mount microscopy**, which shows "jerky, twitching motility." Culture (Diamond’s medium) is the most sensitive method. * **Treatment:** The drug of choice is **Metronidazole**. It is crucial to **treat both partners** to prevent "ping-pong" reinfection.

Q: Which of the following filarial worms is not found in the blood?

Onchocerca volvulus. ### Explanation The diagnostic hallmark of filarial infections is the detection of **microfilariae** (embryonic larvae). The location of these microfilariae determines the diagnostic specimen required. **Why Onchocerca volvulus is the correct answer:** Unlike most filarial nematodes, the microfilariae of *Onchocerca volvulus* (the causative agent of River Blindness) do not circulate in the peripheral blood. Instead, they reside in the **subcutaneous lymphatics and the dermis**. Therefore, the diagnosis is made via **skin snips** rather than blood films. **Analysis of Incorrect Options:** * **Wuchereria bancrofti & Brugia malayi:** These are lymphatic filarial worms. Their microfilariae circulate in the peripheral blood, typically exhibiting **nocturnal periodicity** (peak density between 10 PM and 2 AM). * **Loa loa:** Also known as the African eye worm, its microfilariae circulate in the blood with **diurnal periodicity** (peak density during the day). **NEET-PG High-Yield Pearls:** 1. **Specimen of Choice:** * Blood: *W. bancrofti, B. malayi, Loa loa, Mansonella* species. * Skin Snip: *Onchocerca volvulus, Mansonella streptocerca*. 2. **Vector Mnemonic:** * *W. bancrofti*: *Culex* (urban), *Anopheles* (rural), *Aedes*. * *Onchocerca*: *Simulium* (Blackfly). * *Loa loa*: *Chrysops* (Deerfly/Mango fly). 3. **Clinical Signs:** *Onchocerca* is associated with **Mazzotti reaction** (severe immune response to dying microfilariae after treatment) and "hanging groin." 4. **Drug of Choice:** **Ivermectin** is the treatment of choice for *Onchocerca*, whereas **Diethylcarbamazine (DEC)** is used for *W. bancrofti*. (Note: DEC is contraindicated in Onchocerciasis due to the risk of severe ocular damage).

Q: Which of the following is NOT a usual feature of Ascariasis?

Anemia. **Explanation:** The correct answer is **Anemia (Option C)** because *Ascaris lumbricoides* (Giant Roundworm) does not feed on host blood. Unlike hookworms (*Ancylostoma duodenale* and *Necator americanus*), which attach to the intestinal mucosa and cause chronic blood loss leading to Iron Deficiency Anemia, *Ascaris* lives freely in the intestinal lumen and competes with the host for nutrients, leading to malnutrition and Vitamin A deficiency rather than anemia. **Analysis of other options:** * **Abdominal pain (Option A):** This is a common symptom. Large burdens of adult worms can cause mechanical irritation, vague abdominal discomfort, or even intestinal obstruction (the most common complication in children). * **Urticaria (Option B):** During the life cycle, *Ascaris* larvae migrate through various tissues. This migration triggers a Type I hypersensitivity reaction, often manifesting as allergic symptoms like urticaria (hives) or angioedema. * **Loeffler’s syndrome (Option D):** This is a classic feature occurring during the pulmonary phase of larval migration. It is characterized by transient pulmonary infiltrates on X-ray, cough, dyspnea, and peripheral eosinophilia. **High-Yield Clinical Pearls for NEET-PG:** * **Most common helminthic infection** worldwide: *Ascaris lumbricoides*. * **Infective stage:** Embryonated egg; **Diagnostic stage:** Bile-stained eggs in stool. * **Complications:** Biliary ascariasis (causing cholangitis or pancreatitis) and intestinal bolus obstruction at the ileocecal valve. * **Drug of choice:** Albendazole or Mebendazole.

Q: All the following parasites cause malignancy except?

Onchocerca volvulus. **Explanation:** The association between parasitic infections and carcinogenesis is a high-yield topic in NEET-PG. Certain parasites are classified as **Group 1 Carcinogens** by the IARC because chronic inflammation and metabolic byproducts lead to DNA damage and malignant transformation. **Why Onchocerca volvulus is the correct answer:** *Onchocerca volvulus* is a nematode responsible for **River Blindness** (Onchocerciasis). While it causes severe pathology, including sclerosing keratitis and lichenified dermatitis ("lizard skin"), it has **no known association with malignancy**. **Analysis of Incorrect Options (Parasites that DO cause malignancy):** * **Schistosoma haematobium:** This trematode (blood fluke) inhabits the vesical venous plexus. Chronic irritation from eggs in the bladder wall leads to **Squamous Cell Carcinoma (SCC) of the urinary bladder** (Note: Not transitional cell carcinoma). * **Clonorchis sinensis (Chinese Liver Fluke):** Inhabits the bile ducts. Chronic infection causes biliary epithelial hyperplasia, which can progress to **Cholangiocarcinoma** (bile duct cancer). * **Opisthorchis viverrini (Southeast Asian Liver Fluke):** Similar to *Clonorchis*, it resides in the biliary tract and is a potent risk factor for **Cholangiocarcinoma**. **NEET-PG High-Yield Pearls:** 1. **Schistosoma mansoni/japonicum:** Associated with Hepatocellular Carcinoma (HCC) and Colorectal cancer, though the link is less definitive than *S. haematobium*. 2. **Strongyloides stercoralis:** Linked to Adult T-cell Leukemia/Lymphoma (ATLL) due to its co-infection synergy with HTLV-1. 3. **Key Distinction:** If a question asks for the most common bladder cancer worldwide, it is Transitional Cell Carcinoma; however, in **endemic areas** of Schistosomiasis (e.g., Egypt), **Squamous Cell Carcinoma** is more prevalent.

Q: Chronic dysentery, abdominal pain, and rectal prolapse in children is caused by which of the following parasites?

Trichuris trichura. **Explanation:** The correct answer is **Trichuris trichiura** (Whipworm). This parasite primarily inhabits the caecum and large intestine. In heavy infections, particularly in children, the worms can be found throughout the colon and rectum. **Why Trichuris trichiura is correct:** The hallmark clinical presentation of heavy Trichuriasis is **Trichuris Dysentery Syndrome**. The worms embed their slender anterior ends into the intestinal mucosa, causing chronic inflammation, mucosal friability, and blood loss. The constant irritation and straining (tenesmus) during defecation, combined with the weakening of the pelvic floor muscles and local inflammation, lead to the classic complication of **rectal prolapse**. **Analysis of Incorrect Options:** * **Enterobius vermicularis (Pinworm):** Primarily causes perianal pruritus (itching) at night. It does not cause dysentery or rectal prolapse. * **Ascaris lumbricoides (Roundworm):** Typically causes intestinal obstruction (bolus formation) or Loeffler’s syndrome (pulmonary phase). It does not typically cause chronic dysentery. * **Trichinella spiralis:** Known for causing muscle pain (myositis), periorbital edema, and eosinophilia after ingestion of undercooked pork. It does not inhabit the lower bowel to cause prolapse. **NEET-PG High-Yield Pearls:** * **Morphology:** Adult worm is whip-like (thick posterior, thin anterior). * **Egg:** Characteristic **barrel-shaped** (lemon-shaped) with **bipolar mucus plugs**. * **Treatment:** Mebendazole or Albendazole. * **Key Association:** Always link "Rectal Prolapse + Child + Dysentery" to *Trichuris trichiura*.

Q: Peripheral smear of malaria shows which of the following findings, EXCEPT?

Banana shaped gametocyte - Ovale. The correct answer is **D. Banana shaped gametocyte - Ovale**. ### **Explanation** The diagnosis of malaria via peripheral smear relies on identifying specific morphological features of the *Plasmodium* species within red blood cells (RBCs). 1. **Why Option D is correct:** Banana-shaped (crescentic) gametocytes are the pathognomonic hallmark of ***Plasmodium falciparum***, not *P. ovale*. In *P. ovale* infections, the gametocytes are typically round or oval, and the infected RBCs often show fimbriated (ragged) edges and an oval shape. 2. **Why Option A is incorrect:** *P. vivax* typically presents with a **single ring form** (trophozoite) per RBC. The infected RBC is usually enlarged and contains Schüffner’s dots. 3. **Why Option B is incorrect:** **Multiple ring forms** (multiple parasites infecting a single RBC) and the "Accole/Applique" position (rings at the periphery of the RBC) are characteristic features of ***P. falciparum*** due to its high parasitemia levels. 4. **Why Option C is incorrect:** ***P. malariae*** is known for its unique **"Band and Bar" forms**, where the growing trophozoite stretches across the diameter of the non-enlarged RBC. ### **High-Yield Clinical Pearls for NEET-PG** * **Maurer’s Dots:** Seen in *P. falciparum*. * **Schüffner’s Dots:** Seen in *P. vivax* and *P. ovale*. * **Ziemann’s Dots:** Seen in *P. malariae*. * **RBC Age Preference:** *P. vivax/ovale* prefer young RBCs (reticulocytes); *P. malariae* prefers old RBCs; *P. falciparum* is "indiscriminate" (infects RBCs of all ages), leading to severe anemia and high parasite load. * **Gold Standard Diagnosis:** Microscopy (Thick smear for detection, Thin smear for species identification).

Q: Which statement is true regarding the trophozoites of E. histolytica?

Shows erythrophagocytosis. **Explanation:** *Entamoeba histolytica* is the causative agent of amoebiasis. Distinguishing it from the morphologically identical but non-pathogenic *E. dispar* is a common NEET-PG focus. **1. Why Option C is Correct:** The presence of **ingested Red Blood Cells (erythrophagocytosis)** within the cytoplasm of a trophozoite is the **pathognomonic** feature of *E. histolytica*. It indicates invasive disease, as the parasite actively destroys host tissue and consumes erythrocytes. This feature is never seen in *E. dispar* or *E. coli*. **2. Why Other Options are Incorrect:** * **Option A:** *E. histolytica* has a **central** karyosome (nucleolus). An **eccentric** (off-center) karyosome is a characteristic feature of *Entamoeba coli*, a non-pathogenic commensal. * **Option B:** The nuclear membrane of *E. histolytica* is lined with **fine, uniformly distributed peripheral chromatin**. A membrane "without chromatin" is not characteristic of this genus. * **Option D:** The presence of ingested bacteria is typical of **Entamoeba coli**. *E. histolytica* trophozoites in invasive disease usually contain RBCs but rarely contain bacteria, whereas commensal amoebae feed on intestinal flora. **High-Yield Clinical Pearls for NEET-PG:** * **Motility:** Trophozoites show unidirectional, purposeful movement using finger-like **pseudopodia**. * **Nuclear Structure:** Described as having a "Cartwheel appearance" due to the central karyosome and delicate chromatin. * **Stain of Choice:** Iron-hematoxylin or Trichrome stain. * **Quadrinucleate Cyst:** The infective stage; contains up to 4 nuclei, rounded chromatoid bars (cigar-shaped), and a glycogen mass.

Question 1

Trichomoniasis is transmitted through which stage?

Accepted Answer

Trophozoite

Answer

Cyst

Answer

Oocyst

Answer

Sporozoite

Question 2

Which of the following filarial worms is not found in the blood?

Accepted Answer

Onchocerca volvulus

Answer

Wuchereria bancrofti

Answer

Brugia malayi

Answer

Loa loa

Question 3

Which of the following is NOT a usual feature of Ascariasis?

Accepted Answer

Anemia

Answer

Abdominal pain

Answer

Urticaria

Answer

Loeffler's syndrome

Question 4

All the following parasites cause malignancy except?

Accepted Answer

Onchocerca volvulus

Answer

Schistosoma haematobium

Answer

Clonorchis sinensis

Answer

Opisthrochis viverrini

Question 5

Chronic dysentery, abdominal pain, and rectal prolapse in children is caused by which of the following parasites?

Accepted Answer

Trichuris trichura

Answer

Enterobius vermicularis

Answer

Ascariasis

Answer

Trichinella spiralis

Question 6

Recurrent giardiasis is associated with which of the following conditions?

Accepted Answer

Common variable immunodeficiency

Answer

Severe combined immunodeficiency

Answer

DiGeorge syndrome

Answer

C8 deficiency

Question 7

Peripheral smear of malaria shows which of the following findings, EXCEPT?

Accepted Answer

Banana shaped gametocyte - Ovale

Answer

Single ring form - Vivax

Answer

Multiple ring form - Falciparum

Answer

Bar and band forms - Malariae

Question 8

A 23-year-old man undergoing chemotherapy for acute lymphoblastic leukemia has developed a fever and abdominal pain within the past week. He now has a severe cough. On physical examination, his temperature is 38.4°C. On auscultation, crackles are heard over all lung fields. Laboratory studies show hemoglobin, 12.8 g/dL; hematocrit, 39%; MCV, 90 mm³; platelet count, 221,000/mm³; and WBC count, 16,475/mm³ with 51% segmented neutrophils, 5% bands, 18% lymphocytes, 8% monocytes, and 18% eosinophils. Infection with which of the following organisms is most likely to be complicating the course of this patient's disease?

Accepted Answer

Strongyloides stercoralis

Answer

Cryptococcus neoformans

Answer

Cytomegalovirus

Answer

Pseudomonas aeruginosa

Question 9

Which statement is true regarding the trophozoites of E. histolytica?

Accepted Answer

Shows erythrophagocytosis

Answer

Has an eccentric karyosome

Answer

Nuclear membrane is without chromatin

Answer

Presence of bacteria inside the cell

Question 10

All of the following statements about toxoplasmosis are true except?

Accepted Answer

Arthralgia, sore throat and abdominal pain are the most common manifestations

Answer

May spread by organ transplantation

Answer

Maternal infection acquired after 6 months has high risk of transmission

Answer

Oocyst in freshly passed cat's faeces is infective

Parasitology — MCQs

Parasitology — MCQs

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