Parasitology Practice Questions

Q: Which of the following organs is NOT affected by Plasmodium falciparum?

Heart. **Explanation:** The correct answer is **Heart**. While *Plasmodium falciparum* is known for causing multi-organ dysfunction, it primarily targets organs with extensive microvascular beds where **cytoadherence** and **sequestration** can occur. **1. Why Heart is the correct answer:** In severe malaria, the heart is typically spared from direct pathological damage. While systemic complications like severe anemia or fluid overload can indirectly strain the cardiovascular system, *P. falciparum* does not cause specific inflammatory or obstructive lesions in the myocardium. Therefore, "Malarial Myocarditis" is not a recognized clinical entity. **2. Why other options are incorrect:** * **Lung:** Can lead to **Acute Respiratory Distress Syndrome (ARDS)** due to increased capillary permeability and sequestration of parasites in pulmonary capillaries. This is a common cause of death in adults. * **Liver:** The liver is the site of the initial **pre-erythrocytic (exo-erythrocytic) cycle**. Severe infection causes centrilobular necrosis, leading to jaundice (biliary remittent fever). * **Kidney:** Causes **Acute Tubular Necrosis (ATN)** due to hemoglobinuria and ischemia. A classic presentation is **Blackwater Fever**, characterized by massive intravascular hemolysis and dark urine. **High-Yield Clinical Pearls for NEET-PG:** * **Sequestration:** Mediated by **PfEMP-1** (P. falciparum erythrocyte membrane protein 1) which binds to receptors like **ICAM-1** and **CD36** on vascular endothelium. * **Cerebral Malaria:** The most dreaded complication; characterized by "Dürck’s granulomas" (focal microglial proliferation). * **Hypoglycemia:** A common metabolic complication caused by both the parasite and quinine therapy. * **Spleen:** *P. falciparum* can cause "Tropical Splenomegaly Syndrome" (Hyperreactive Malarial Splenomegaly).

Q: An AIDS patient presents with headaches and disorientation. A clinical diagnosis of Toxoplasma encephalitis is made, and Toxoplasma cysts are observed in a brain section. Which of the following antibody results would be most likely in this patient?

IgM nonreactive, IgG reactive (low titer). ### Explanation **1. Why Option B is Correct:** In patients with AIDS, Toxoplasma encephalitis is almost always a result of **reactivation of a latent infection** rather than a primary (new) infection. * **IgG:** Since the infection is a reactivation, the patient will have pre-existing IgG antibodies. However, because these patients are severely immunocompromised (typically CD4 <100 cells/mm³), they often fail to mount a robust anamnestic response, leading to **low or stable IgG titers**. * **IgM:** IgM is a marker of acute/primary infection. In reactivation cases, IgM is typically **nonreactive (negative)**. **2. Why Other Options are Incorrect:** * **Option A:** If both are nonreactive, it suggests the patient has never been exposed to *Toxoplasma gondii*. While rare cases of seronegative toxoplasmosis occur in profound immunosuppression, a reactive IgG is the standard diagnostic expectation for reactivation. * **Options C & D:** High titers of IgG and the presence of IgM are characteristic of **primary (acute) toxoplasmosis** in an immunocompetent host. In AIDS patients, the immune system is usually too suppressed to produce IgM or a high-titer IgG surge during reactivation. **3. Clinical Pearls for NEET-PG:** * **Most common cause** of CNS mass lesions in AIDS patients. * **Imaging:** Classic "Ring-enhancing lesions" on CT/MRI (often multiple and involving basal ganglia). * **Definitive Diagnosis:** Brain biopsy (showing tachyzoites or cysts), though usually diagnosed empirically. * **Prophylaxis:** Started when CD4 count <100 cells/mm³. Drug of choice: **Trimethoprim-Sulfamethoxazole (TMP-SMX)**. * **Treatment:** Pyrimethamine + Sulfadiazine + Folinic acid.

Q: Schistosomiasis is a disease characterized by granulomatous reactions to the ova or to products of the parasite at the place of oviposition. Clinical manifestations include which one of the following?

Splenomegaly. **Explanation:** The clinical manifestations of Schistosomiasis (Bilharziasis) are primarily driven by the host’s **granulomatous immune response** to eggs trapped in tissues, rather than the adult worms themselves. **Why Splenomegaly is Correct:** In infections caused by *Schistosoma mansoni* and *S. japonicum*, adult worms reside in the mesenteric veins. Eggs are deposited and travel via the portal circulation to the liver, where they trigger periportal (Symmers' pipe-stem) fibrosis. This leads to **portal hypertension**, which subsequently causes congestive **splenomegaly** and esophageal varices. This "hepatosplenic schistosomiasis" is a classic presentation in chronic cases. **Analysis of Incorrect Options:** * **A. Bladder wall hyperplasia:** While *S. haematobium* affects the urinary tract, it typically causes bladder wall **calcification**, ulceration, and squamous cell carcinoma. "Hyperplasia" is not the characteristic pathological description used for these lesions. * **B. Pulmonary embolism:** While eggs can reach the lungs causing pulmonary hypertension (cor pulmonale), they do not typically cause classic thromboembolism. * **D. Cardiac abnormalities:** Heart involvement is rare and usually secondary to pulmonary hypertension (Right heart failure), not a primary manifestation of oviposition. **NEET-PG High-Yield Pearls:** * **Intermediate Host:** Freshwater snails (*Biomphalaria* for *S. mansoni*; *Bulinus* for *S. haematobium*). * **Infective Stage:** Cercaria (penetrates skin during swimming). * **Diagnostic Feature:** Eggs with spines (*S. haematobium*: Terminal spine; *S. mansoni*: Lateral spine). * **Drug of Choice:** Praziquantel. * **Katayama Fever:** An acute serum sickness-like reaction occurring weeks after infection.

Q: Dwarf tapeworm refers to which of the following?

Hymenolepsis nana. **Explanation:** **Hymenolepis nana (H. nana)** is known as the **Dwarf Tapeworm** because it is the smallest intestinal cestode infecting humans, typically measuring only 15–40 mm in length. **Why H. nana is the correct answer:** It is unique among tapeworms because it does not mandatory require an intermediate host; it can complete its entire life cycle in a single host (Man). It is the only cestode capable of **internal autoinfection**, where eggs hatch within the intestine and develop into larvae (cysticercoids) in the villi, leading to heavy parasite loads. **Analysis of Incorrect Options:** * **A. Echinococcus granulosus:** Known as the **Dog Tapeworm**. It causes Hydatid disease and is characterized by the formation of slow-growing cysts in the liver and lungs. * **B. Loa loa:** Known as the **African Eye Worm**. It is a nematode (roundworm) transmitted by the *Chrysops* fly, characterized by Calabar swellings and subconjunctival migration. * **C. Schistosoma mansoni:** Known as a **Blood Fluke**. It is a trematode that resides in the mesenteric veins and causes intestinal schistosomiasis and portal hypertension. **High-Yield Clinical Pearls for NEET-PG:** * **Smallest Cestode:** *H. nana* (Dwarf tapeworm). * **Largest Cestode:** *Diphyllobothrium latum* (Fish tapeworm). * **Infective Stage:** Embryonated eggs (most common) or cysticercoid larvae (via ingestion of infected insects). * **Diagnosis:** Stool microscopy showing characteristic eggs with **polar filaments** (distinguishes it from *H. diminuta*). * **Treatment of Choice:** Praziquantel.

Q: Strawberry cervix is seen in which of the following conditions?

Trichomonas vaginalis infection. **Explanation:** **Trichomonas vaginalis infection** is the correct answer. The "Strawberry Cervix" (colpitis macularis) is a classic clinical sign characterized by punctate hemorrhages on the cervical epithelium. This occurs because the parasite causes intense local inflammation and capillary dilation, making the cervix appear red and speckled, resembling the surface of a strawberry. While highly specific for Trichomoniasis, it is only visible on physical examination in about 2-5% of cases (more frequently seen via colposcopy). **Analysis of Incorrect Options:** * **A. Gardnerella vaginalis:** This is the primary causative agent of Bacterial Vaginosis (BV). It is characterized by a "thin, homogenous, fishy-smelling discharge" and the presence of **Clue cells** on microscopy, but it does not cause a strawberry cervix. * **C. Candida infection:** Vulvovaginal Candidiasis typically presents with intense pruritus and a thick, white, **"curd-like" or "cottage cheese" discharge**. The vaginal mucosa may be erythematous, but it lacks the punctate hemorrhages of Trichomoniasis. * **D. Mycoplasma pneumoniae:** This is a respiratory pathogen responsible for atypical pneumonia and is not associated with vaginal or cervical infections. **NEET-PG High-Yield Pearls:** * **Trichomoniasis:** Caused by a flagellated protozoan. Look for **"frothy, yellowish-green, foul-smelling discharge"** and a vaginal pH > 4.5. * **Diagnosis:** The gold standard is **NAAT**, but the most common bedside test is **Wet Mount microscopy** showing "jerky/twitching motility." * **Treatment:** Drug of choice is **Metronidazole**. Crucially, the **partner must also be treated** to prevent reinfection (it is an STI). * **Whiff Test:** Positive (fishy odor with KOH) in both Bacterial Vaginosis and Trichomoniasis.

Q: What is the treatment of choice for Echinococcus granulosus?

Albendazole. **Explanation:** **Echinococcus granulosus**, the causative agent of Cystic Echinococcosis (Hydatid cyst), is primarily managed through a combination of surgery, aspiration (PAIR), and chemotherapy. **Why Albendazole is the Correct Choice:** **Albendazole** is the drug of choice because it is a broad-spectrum anthelmintic with superior pharmacokinetic properties compared to other benzimidazoles. It is a prodrug that is converted into **albendazole sulfoxide**, which achieves high concentrations in the hydatid cyst fluid and wall. It works by inhibiting microtubule synthesis, leading to glucose depletion and death of the scolex. In clinical practice, it is used as a primary treatment for small/multiple cysts or as an adjuvant before and after surgery/PAIR to reduce the risk of secondary seeding. **Analysis of Incorrect Options:** * **B. Thiabendazole:** While it is a benzimidazole, it is rarely used now due to significant systemic toxicity and lower efficacy compared to newer agents. * **C. Mebendazole:** It was previously used but is less effective than Albendazole because it is poorly absorbed from the gastrointestinal tract, leading to inconsistent therapeutic levels within the cyst. * **D. Praziquantel:** It is highly effective against adult tapeworms and is often used as an **adjunct** to Albendazole to kill protoscolices more rapidly, but it is not the primary "treatment of choice" for the cyst itself. **High-Yield Clinical Pearls for NEET-PG:** * **PAIR Technique:** Puncture, Aspiration, Injection (of scolicidal agents like hypertonic saline or 95% ethanol), and Re-aspiration. * **Diagnosis:** "Egg-shell calcification" on X-ray; "Water-lily sign" or "Camel-back sign" on USG/CT. * **Casoni’s Test:** An immediate hypersensitivity skin test (now largely replaced by ELISA). * **Surgical Precaution:** Extreme care must be taken to prevent cyst rupture, which can lead to life-threatening **anaphylaxis**.

Q: Which of the following is a flagellated amoeba?

Naegleria fowleri. **Explanation:** The correct answer is **Naegleria fowleri**. This organism is classified as a **Free-Living Amoeba (FLA)** and is unique because it is "amphizoic," meaning it can exist as both a free-living organism and a pathogen. **Why Naegleria fowleri is correct:** *Naegleria fowleri* is known as a **"transformer"** because it exists in three stages: the trophozoite, the cyst, and the **flagellated stage**. When environmental conditions change (such as a decrease in nutrient concentration or exposure to distilled water), the trophozoite develops two long flagella to move quickly to a more favorable environment. This transient flagellated form is a key diagnostic feature. **Why the other options are incorrect:** * **Entamoeba histolytica:** This is an obligate intestinal parasite. It exists only as a trophozoite (moving via pseudopodia) and a cyst. It never develops flagella. * **Acanthamoeba:** While it is a free-living amoeba, it only has two stages: trophozoite and cyst. It lacks a flagellated stage. It is characterized by "acanthopodia" (spine-like projections). * **Balamuthia:** Similar to *Acanthamoeba*, *Balamuthia mandrillaris* exists only in trophozoite and cyst forms and does not possess flagella. **High-Yield Clinical Pearls for NEET-PG:** * **Disease:** *Naegleria fowleri* causes **Primary Amoebic Meningoencephalitis (PAM)**, a rapidly fatal CNS infection typically seen in healthy children/young adults with a history of swimming in warm freshwater. * **Path of Entry:** Through the **cribriform plate** via the olfactory nerves. * **Diagnosis:** Wet mount of CSF shows **actively motile trophozoites**. Note: Only the trophozoite form is found in human tissue; cysts are not seen in brain sections (unlike *Acanthamoeba*). * **Drug of Choice:** Amphotericin B.

Q: In which type of malarial parasite is the exoerythrocytic stage absent?

P. falciparum. ### Explanation The life cycle of *Plasmodium* in humans consists of two main stages: the **Exoerythrocytic (Hepatic) cycle** and the **Erythrocytic cycle**. The correct answer is **P. falciparum** (and also **P. malariae**). In these species, once the sporozoites enter the liver cells and mature into schizonts, they are released into the bloodstream to begin the erythrocytic phase. There is **no persistent liver stage** (hypnozoite). Once the liver is cleared, it remains clear unless a new mosquito bite occurs. **Analysis of Options:** * **P. vivax & P. ovale (Options A & B):** These species possess a "dormant" exoerythrocytic stage known as **hypnozoites**. These forms can remain latent in the liver for months or years, leading to **relapses** of malaria even after the blood stage has been treated. * **P. malariae (Option D):** Like *P. falciparum*, it lacks a true exoerythrocytic (hypnozoite) stage. However, it is known for **recrudescence** (survival of low-level parasites in the blood), not relapse from the liver. In many competitive exams, if both are options, *P. falciparum* is the classic textbook answer for the absence of a persistent liver phase. **High-Yield NEET-PG Pearls:** 1. **Relapse vs. Recrudescence:** Relapse is due to hypnozoites in the liver (*P. vivax/ovale*). Recrudescence is due to persistent sub-clinical parasites in the blood (*P. falciparum/malariae*). 2. **Drug of Choice for Hypnozoites:** **Primaquine** or **Tafenoquine** must be administered to achieve a "radical cure" in *P. vivax* and *P. ovale* infections. 3. **Primaquine Caution:** Always screen for **G6PD deficiency** before administration to prevent acute hemolysis. 4. **P. falciparum** is the most common cause of cerebral malaria and lacks the Schuffner’s dots seen in *P. vivax*.

Question 1

Which of the following organs is NOT affected by Plasmodium falciparum?

Accepted Answer

Heart

Answer

Lung

Answer

Liver

Answer

Kidney

Question 2

Which of the following is NOT a liver fluke?

Accepted Answer

Paragonimus

Answer

Whipworm

Answer

Clonorchis sinensis

Answer

Gnathostoma spinigerum

Question 3

An AIDS patient presents with headaches and disorientation. A clinical diagnosis of Toxoplasma encephalitis is made, and Toxoplasma cysts are observed in a brain section. Which of the following antibody results would be most likely in this patient?

Accepted Answer

IgM nonreactive, IgG reactive (low titer)

Answer

IgM nonreactive, IgG nonreactive

Answer

IgM reactive (low titer), IgG reactive (high titer)

Answer

IgM reactive (high titer), IgG reactive (high titer)

Question 4

Schistosomiasis is a disease characterized by granulomatous reactions to the ova or to products of the parasite at the place of oviposition. Clinical manifestations include which one of the following?

Accepted Answer

Splenomegaly

Answer

Bladder wall hyperplasia

Answer

Pulmonary embolism

Answer

Cardiac abnormalities

Question 5

Dwarf tapeworm refers to which of the following?

Accepted Answer

Hymenolepsis nana

Answer

Echinococcus

Answer

Loa Loa

Answer

Schistosoma mansoni

Question 6

Strawberry cervix is seen in which of the following conditions?

Accepted Answer

Trichomonas vaginalis infection

Answer

Gardenella vaginalis infection

Answer

Candida infection

Answer

Mycoplasma pneumoniae infection

Question 7

What is the treatment of choice for Echinococcus granulosus?

Accepted Answer

Albendazole

Answer

Thio-bendazole

Answer

Mebendazole

Answer

Praziquantel

Question 8

Which of the following is a flagellated amoeba?

Accepted Answer

Naegleria fowleri

Answer

Entamoeba histolytica

Answer

Acanthamoeba

Answer

Balamuthia

Question 9

In which type of malarial parasite is the exoerythrocytic stage absent?

Accepted Answer

P. falciparum

Answer

P. ovale

Answer

P. vivax

Answer

P. malariae

Question 10

What is the correct sequence of the malaria parasite life cycle?

Accepted Answer

Exoerythrocytic stage, Erythrocytic stage, Gametocytic stage, Sporogony

Answer

Exoerythrocytic stage, Gametocytic stage, Erythrocytic stage, Sporogony

Answer

Exoerythrocytic stage, Sporogony, Gametocytic stage, Erythrocytic stage

Answer

Exoerythrocytic stage, Sporogony, Erythrocytic stage, Gametocytic stage

Parasitology — MCQs

Parasitology — MCQs

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