Which of the following amoebae does not have a neuropathogenic effect?
Which of the following statements about Helminths is false?
Which of the following is the only ovoviviparous parasite among the options provided?
Cylindrical helminths are -
Consumption of uncooked pork is likely to cause which of the following helminthic disease -
Which Schistosoma species is primarily associated with eggs being discharged in urine?
What is the infective form of Trypanosoma brucei?
In malaria, pre-erythrocytic schizogony occurs in -
A 4 year old child presents with acute watery diarrhea and abdominal cramps. Stool microscopy reveals trophozoites with falling leaf motility. What is the etiological agent?
What does the hookworm primarily feed on?
NEET-PG 2013 - Microbiology NEET-PG Practice Questions and MCQs
Question 41: Which of the following amoebae does not have a neuropathogenic effect?
- A. Naegleria
- B. Acanthamoeba
- C. Dientamoeba (Correct Answer)
- D. Balamuthia
Explanation: ***Dientamoeba*** - *Dientamoeba fragilis* is an intestinal flagellate (often mistakenly classified as an amoeba) that causes **gastrointestinal symptoms** like diarrhea and abdominal pain. - It has **no known neuropathogenic effects** and does not invade the central nervous system. *Naegleria* - *Naegleria fowleri* is a highly virulent amoeba that causes **primary amoebic meningoencephalitis (PAM)**, a rapidly fatal infection of the central nervous system. - It typically invades the brain after **nasal insufflation** of contaminated water. *Acanthamoeba* - *Acanthamoeba* species can cause **granulomatous amoebic encephalitis (GAE)**, a subacute to chronic central nervous system infection, particularly in immunocompromised individuals. - They are also known to cause **amoebic keratitis**, a severe eye infection. *Balamuthia* - *Balamuthia mandrillaris* causes **granulomatous amoebic encephalitis (GAE)**, similar to *Acanthamoeba*, but often in both immunocompetent and immunocompromised individuals. - It can also lead to **skin lesions** and has a tropism for the brain, causing severe neurological damage.
Question 42: Which of the following statements about Helminths is false?
- A. Alimentary canal is complete in Nematodes
- B. Nematodes have separate sexes
- C. Body cavity is present in trematodes (Correct Answer)
- D. Alimentary canal is present but incomplete in trematodes
Explanation: ***Body cavity is present in trematodes*** - Trematodes are **flatworms** (Platyhelminthes), which are **acoelomate**, meaning they lack a true body cavity or coelom. - Their internal organs are embedded in a **parenchymal tissue** rather than being suspended within a fluid-filled cavity. *Alimentary canal is complete in Nematodes* - **Nematodes** (roundworms) possess a **complete alimentary canal**, with a distinct mouth, intestine, and anus. - This allows for **unidirectional flow of food** and waste through their digestive system. *Nematodes have separate sexes* - **Nematodes** are generally **dioecious**, meaning they have separate male and female individuals. - This sexual dimorphism is a characteristic feature for most species within this phylum. *Alimentary canal is Present but incomplete* - The statement refers to the digestive system of **Platyhelminthes** (flatworms) like trematodes and cestodes, where the alimentary canal is present but **incomplete** (lacking an anus). - This means they have a **single opening** that serves as both mouth and anus for digestion.
Question 43: Which of the following is the only ovoviviparous parasite among the options provided?
- A. Ascaris
- B. Strongyloides (Correct Answer)
- C. Enterobius
- D. Ancylostoma
Explanation: ***Strongyloides*** - *Strongyloides stercoralis* stands out as the only **ovoviviparous** parasite among the options, meaning that its eggs hatch while still inside the uterus of the female worm. - The female worm lays **larvated eggs** that quickly hatch into **rhabditiform larvae** in the intestine or intestinal wall, which are then passed in the feces. *Ascaris* - *Ascaris lumbricoides* is **oviparous**, laying **unembryonated eggs** that are passed in the feces and require a period of maturation in the soil to become infective. - The eggs are robust and can survive for long periods in the environment before they are ingested. *Enterobius* - *Enterobius vermicularis* (pinworm) is also **oviparous**, with the female worm migrating to the perianal region to lay **embryonated eggs** on the skin. - These eggs are immediately infective to humans upon ingestion. *Ancylostome* - Ancylostomes (hookworms) are **oviparous** and lay **thin-shelled eggs** that are passed in the feces and hatch into rhabditiform larvae in the soil. - These larvae then develop into infective **filariform larvae** that penetrate the skin.
Question 44: Cylindrical helminths are -
- A. Tapeworms
- B. Flukes
- C. Roundworms (Correct Answer)
- D. Hookworms
Explanation: ***Roundworms*** - **Roundworms**, also known as **nematodes**, are characterized by their **cylindrical body shape**. - Their unsegmented, tapered bodies distinguish them from flatworms like tapeworms and flukes. *Tapeworms* - **Tapeworms**, or **cestodes**, have **flat, ribbon-like bodies** segmented into proglottids. - They are not cylindrical but rather dorsoventrally flattened. *Flukes* - **Flukes**, or **trematodes**, have **flat, leaf-shaped bodies**, which are not cylindrical. - Their morphology includes suckers for attachment and they are not segmented. *Hookworms* - **Hookworms** are a type of **roundworm** (nematode), which means they are cylindrical. However, "Roundworms" is a broader and more accurate classification for the general term "cylindrical helminths." - While hookworms are indeed cylindrical, the option "Roundworms" encompasses all such cylindrical helminths, making it a more general and appropriate answer.
Question 45: Consumption of uncooked pork is likely to cause which of the following helminthic disease -
- A. Taenia saginata
- B. Taenia solium (Correct Answer)
- C. Trichuris trichiura
- D. None of the options
Explanation: ***Taenia solium*** - Infection with **_Taenia solium_** (pork tapeworm) occurs by consuming raw or undercooked **pork** containing **cysticerci** (larval cysts). - This can lead to **taeniasis** (intestinal tapeworm infection) and, if humans ingest the eggs, **cysticercosis**, a more severe disease involving larval cysts in tissues like the brain. *Taenia saginata* - **_Taenia saginata_** (beef tapeworm) is acquired by eating raw or undercooked **beef** containing larval cysts, not pork. - While it causes gastrointestinal symptoms, it does not typically lead to systemic cysticercosis in humans. *Trichuris trichiura* - **_Trichuris trichiura_** (whipworm) infection is caused by ingesting **embryonated eggs** from contaminated soil, typically associated with poor sanitation. - It is not transmitted through the consumption of undercooked meat. *None of the options* - This option is incorrect because **_Taenia solium_** is definitively associated with the consumption of uncooked pork.
Question 46: Which Schistosoma species is primarily associated with eggs being discharged in urine?
- A. S. haematobium (Correct Answer)
- B. S. japonicum
- C. S. mansoni
- D. S. mekongi
Explanation: ***S. haematobium*** - *S. haematobium* specifically targets the **urinary bladder plexus**, leading to the discharge of eggs in the **urine**. - Infection with *S. haematobium* is the primary cause of **urinary schistosomiasis** and is associated with complications like **hematuria** and bladder cancer. *S. japonicum (intestinal)* - *S. japonicum* primarily infects the **mesenteric veins of the small intestine** and discharges its eggs in **feces**, not urine. - This species is known for causing severe **intestinal and hepatic schistosomiasis** due to the large number of eggs produced. *S. mansoni (intestinal)* - *S. mansoni* also primarily infects the **mesenteric veins, mainly of the large intestine**, and its eggs are excreted in **feces**. - It is a common cause of **intestinal schistosomiasis**, leading to symptoms such as abdominal pain, diarrhea, and hepatosplenomegaly. *S. mekongi* - *S. mekongi* is another **intestinal schistosome**, closely related to *S. japonicum*, and its eggs are discharged in **feces**. - This species is found in specific regions of Southeast Asia and causes similar symptoms to other intestinal schistosomes.
Question 47: What is the infective form of Trypanosoma brucei?
- A. Trypomastigote (Correct Answer)
- B. Amastigote form
- C. Egg stage
- D. No infective form
Explanation: ***Trypomastigote*** - The **trypomastigote** is the infective form of *Trypanosoma brucei* transmitted to humans by the **tsetse fly** bite. - In the human host, trypomastigotes multiply in the **blood and lymphatic system**, eventually invading the central nervous system. *Amastigote form* - The **amastigote** form is characteristic of *Trypanosoma cruzi* and *Leishmania* species, not *Trypanosoma brucei*. - **Amastigotes** are found intracellularly and lack a flagellum, responsible for replication within host cells for these other parasites. *Egg stage* - *Trypanosoma brucei* is a **protozoan parasite** and does not have an **egg stage** in its life cycle. - Egg stages are typical for helminths, such as **tapeworms** or **flukes**. *No infective form* - This statement is incorrect; **all parasitic organisms** must have an infective stage to be transmitted to their hosts. - The **trypomastigote** is specifically adapted for transmission and survival in the human host and vector.
Question 48: In malaria, pre-erythrocytic schizogony occurs in -
- A. Lung
- B. Liver (Correct Answer)
- C. Spleen
- D. Kidney
Explanation: ***Liver*** - After being introduced by a mosquito bite, **Plasmodium sporozoites** rapidly travel to the liver - In the liver, they invade **hepatocytes** and undergo asexual reproduction, known as **pre-erythrocytic (or hepatic) schizogony**, forming merozoites - This is the exo-erythrocytic cycle that occurs before red blood cell invasion *Lung* - The lungs are not a primary site for **Plasmodium** development or asexual reproduction in the human host - While some parasite components or host immune responses might involve the lungs in severe malaria, it is not where pre-erythrocytic schizogony occurs *Spleen* - The **spleen** is primarily involved in clearing infected red blood cells and acts as a site for immune responses to malaria, but not for initial schizogony - It plays a significant role in the **erythrocytic stage** of malaria by filtering and destroying parasitized red blood cells *Kidney* - The **kidneys** are not involved in the life cycle of the **Plasmodium parasite** during pre-erythrocytic schizogony - While malaria can cause **renal complications** (such as acute kidney injury in severe cases), this is a pathological effect, not a site of parasite development
Question 49: A 4 year old child presents with acute watery diarrhea and abdominal cramps. Stool microscopy reveals trophozoites with falling leaf motility. What is the etiological agent?
- A. Giardia lamblia (Correct Answer)
- B. Trichomonas tenax
- C. Balantidium coli
- D. Entamoeba histolytica
Explanation: **Giardia lamblia** - The presence of **trophozoites** with characteristic **falling leaf motility** in stool microscopy is pathognomonic for **Giardia lamblia** infection. - **Giardiasis** commonly causes **acute watery diarrhea** and **abdominal cramps** in children, often acquired through contaminated water or food. *Entamoeba histolytica* - **Entamoeba histolytica** causes **amoebic dysentery**, characterized by bloody diarrhea, unlike the watery diarrhea described. - Its trophozoites exhibit **directional motility** with pseudopods and may contain ingested red blood cells, not falling leaf motility. *Trichomonas tenax* - **Trichomonas tenax** is found in the **oral cavity** and is not associated with intestinal infections or diarrhea. - Its typical habitat and clinical presentation are entirely different from the symptoms described. *Balantidium coli* - **Balantidium coli** is a large, ciliated protozoan whose trophozoites have a **distinctive kidney-shaped macronucleus** and rotary motility with cilia. - It causes **balantidiasis**, which can range from asymptomatic to dysentery, but its trophozoite morphology and motility are distinct from falling leaf.
Question 50: What does the hookworm primarily feed on?
- A. Plasma proteins
- B. Lymphatic fluid
- C. Interstitial fluid
- D. Blood from intestinal mucosa (Correct Answer)
Explanation: ***Blood from intestinal mucosa*** - Hookworms attach to the **intestinal wall** and ingest host blood, leading to blood loss and potential **anemia**. - They produce **anticoagulants** to facilitate continuous feeding from the mucosal capillaries. *Plasma proteins* - While plasma contains proteins, hookworms primarily feed directly on **whole blood**, not just isolated plasma proteins. - Feeding mainly on plasma proteins would not explain the significant **iron-deficiency anemia** associated with hookworm infection. *Lymphatic fluid* - Hookworms reside in the **small intestine** and do not typically feed on lymphatic fluid. - Other parasites, like **filarial worms**, are known to inhabit and obstruct the lymphatic system. *Interstitial fluid* - Interstitial fluid is found in the spaces between cells; hookworms feed from the **vascular supply** within the intestinal mucosa. - Feeding on interstitial fluid would not cause the characteristic **blood loss** seen in hookworm infections.