Protozoa/Helminths US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Protozoa/Helminths. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Protozoa/Helminths US Medical PG Question 1: A 30-year-old forest landscape specialist is brought to the emergency department with hematemesis and confusion. One week ago, she was diagnosed with influenza when she had fevers, severe headaches, myalgias, hip and shoulder pain, and a maculopapular rash. After a day of relative remission, she developed abdominal pain, vomiting, and diarrhea. A single episode of hematemesis occurred prior to admission. Two weeks ago she visited rainforests and caves in western Africa where she had direct contact with animals, including apes. She has no history of serious illnesses or use of medications. She is restless and her temperature is 38.0°C (100.4°F); pulse, 95/min; respirations, 20/min; and supine and upright blood pressure, 130/70 mm Hg and 100/65 mm Hg, respectively. Conjunctival suffusion is seen. Ecchymoses are observed on the lower extremities. She is bleeding from one of her intravenous lines. The peripheral blood smear is negative for organisms. The laboratory studies show the following:
Hemoglobin 10 g/dL
Leukocyte count 1,000/mm3
Segmented neutrophils 65%
Lymphocytes 20%
Platelet count 50,000/mm3
Partial thromboplastin time (activated) 60 seconds
Prothrombin time 25 seconds
Fibrin split products positive
Serum
Alanine aminotransferase (ALT) 85 U/L
Aspartate aminotransferase (AST) 120 U/L
γ-Glutamyltransferase (GGT) 83 U/L (N = 5–50 U/L)
Creatinine 2 mg/dL
Which of the following is the most likely causal pathogen?
- A. Zika virus
- B. Plasmodium falciparum
- C. Yersinia pestis
- D. Babesia microti
- E. Ebola virus (Correct Answer)
Protozoa/Helminths Explanation: ***Ebola virus***
- The patient's presentation with **fever, myalgias, headache, maculopapular rash, gastrointestinal symptoms (vomiting, diarrhea, hematemesis), confusion, bleeding diathesis (ecchymoses, IV site bleeding, prolonged PT/aPTT, positive fibrin split products)**, and recent travel to **rainforests and caves in western Africa with ape contact** is highly consistent with Ebola virus disease.
- Laboratory findings of **leukopenia, thrombocytopenia, elevated liver enzymes (ALT, AST, GGT), and acute kidney injury (creatinine 2 mg/dL)** further support this diagnosis, as Ebola can cause widespread organ damage and disseminated intravascular coagulation (DIC).
*Zika virus*
- While Zika can cause **fever, rash, and arthralgia**, it typically presents as a milder illness and does not characteristically lead to severe **hemorrhagic manifestations, confusion, or significant organ dysfunction** like the patient's presentation.
- The patient's severe gastrointestinal symptoms, profound coagulopathy, and significant organ involvement are not typical features of Zika virus infection.
*Plasmodium falciparum*
- **Malaria** caused by *Plasmodium falciparum* can lead to **fever, headache, myalgias, and confusion**, and severe malaria can cause **anemia and thrombocytopenia**.
- However, the prominent **maculopapular rash, severe hemorrhagic diathesis with multi-site bleeding, prolonged PT/aPTT, and significant leukopenia** are not characteristic features of *P. falciparum* malaria, and the peripheral blood smear was negative for organisms.
*Yersinia pestis*
- **Bubonic plague** (caused by *Yersinia pestis*) can cause **fever, headache, and severe illness**, often with characteristic **lymphadenopathy (buboes)**, and can progress to pneumonic or septicemic forms.
- The absence of prominent buboes and the specific constellation of hemorrhagic fever symptoms, rash, and liver/kidney involvement point away from *Yersinia pestis* and more towards a viral hemorrhagic fever.
*Babesia microti*
- **Babesiosis** is a tick-borne illness causing **fever, fatigue, myalgias, and hemolytic anemia**, primarily seen in immunocompromised individuals or those with splenectomy, and does not typically involve **maculopapular rash, severe hemorrhagic phenomena, or significant leukopenia**.
- While it can cause some anemia and thrombocytopenia, the overall clinical picture, especially the prominent bleeding and multi-organ failure, is inconsistent with babesiosis.
Protozoa/Helminths US Medical PG Question 2: A 46-year-old man comes to the physician because of a 1-week history of headache, muscle pain, and recurrent fever spikes that occur without a noticeable rhythm. Two weeks ago, he returned from a 5-week-long world trip during which he climbed several mountains in India, Africa, and Appalachia. Chemoprophylaxis with chloroquine was initiated one week prior to the trip. Physical examination shows jaundice. The spleen is palpated 2 cm below the left costal margin. His hemoglobin concentration is 10 g/dL. A photomicrograph of a peripheral blood smear is shown. Which of the following agents is the most likely cause of this patient's findings?
- A. Chikungunya virus
- B. Trypanosoma cruzi
- C. Leishmania donovani
- D. Plasmodium falciparum (Correct Answer)
- E. Trypanosoma brucei
Protozoa/Helminths Explanation: **Plasmodium falciparum**
- The image shows **multiple ring forms** and **applique forms** within red blood cells, which are characteristic of *Plasmodium falciparum* malaria. The clinical presentation of **headache, muscle pain, recurrent fever spikes without a noticeable rhythm, jaundice, splenomegaly, and anemia (Hb 10 g/dL)** in a traveler returning from India and Africa is highly consistent with malaria, especially given the chloroquine chemoprophylaxis which is often ineffective against chloroquine-resistant strains of *P. falciparum*.
- *P. falciparum* can cause severe disease, including **anemia** due to red blood cell destruction and **jaundice** due to hemolysis and liver involvement, and is notorious for its **irregular fever patterns** early in the infection cycle.
*Chikungunya virus*
- Chikungunya typically presents with **high fever, severe polyarthralgia**, and rash, but does not cause the parasitemia or specific red blood cell morphology seen in the image.
- While present in endemic regions like India and Africa, it does not lead to **anemia, splenomegaly, or jaundice** to the extent seen in this patient, nor does it appear on a blood smear as intracellular parasites.
*Trypanosoma cruzi*
- *Trypanosoma cruzi* causes **Chagas disease**, which is endemic to **Central and South America**, not India or Africa.
- While it can be found in blood smears during the acute phase (trypomastigotes), its morphology differs significantly from the ring forms seen, and the overall clinical picture of **fever, jaundice, and marked splenomegaly with characteristic RBC parasites** does not fit Chagas disease.
*Leishmania donovani*
- *Leishmania donovani* causes **visceral leishmaniasis (kala-azar)**, characterized by **prolonged fever, splenomegaly, hepatomegaly, pancytopenia**, and weight loss.
- While present in India and Africa, the parasites (**amastigotes**) are typically found within **macrophages** in bone marrow, spleen, or liver aspirates, not as ring forms within red blood cells on a peripheral blood smear.
*Trypanosoma brucei*
- *Trypanosoma brucei* causes **African sleeping sickness**, which involves **fever, headache, joint pain, neurological symptoms**, and lymphadenopathy (Winterbottom's sign).
- The parasites (trypomastigotes) are observed extracellularly in the blood, lymph, or CSF, and have a distinct **elongated, flagellated morphology** that is completely different from the intracellular ring forms seen in the provided image.
Protozoa/Helminths US Medical PG Question 3: A 32-year-old woman presents to your office with abdominal pain and bloating over the last month. She also complains of intermittent, copious, non-bloody diarrhea over the same time. Last month, she had a cough that has since improved but has not completely resolved. She has no sick contacts and has not left the country recently. She denies any myalgias, itching, or rashes. Physical and laboratory evaluations are unremarkable. Examination of her stool reveals the causative organism. This organism is most likely transmitted to the human host through which of the following routes?
- A. Insect bite
- B. Penetration of skin (Correct Answer)
- C. Sexual contact
- D. Inhalation
- E. Animal bite
Protozoa/Helminths Explanation: ***Penetration of skin***
- The symptoms of **abdominal pain**, **bloating**, **intermittent copious non-bloody diarrhea**, and a recent **cough** are highly suggestive of a **hookworm infection**.
- Hookworm larvae (filariform larvae) primarily penetrate the skin, usually through bare feet, as their mode of entry into the human host.
*Insect bite*
- Although some parasitic infections are transmitted by insect bites (e.g., malaria, Chagas disease), hookworms are not transmitted this way.
- **Insect-borne diseases** typically present with different clinical manifestations or geographical associations.
*Sexual contact*
- **Sexually transmitted infections** involve direct contact of mucous membranes or body fluids during sexual activity.
- Hookworm infection transmission through sexual contact is not a recognized route.
*Inhalation*
- **Inhalation** is a route of transmission for respiratory pathogens (e.g., influenza, tuberculosis) or certain fungal infections, but not for hookworms.
- While hookworm larvae migrate through the lungs, the initial infection pathway is not via inhalation.
*Animal bite*
- **Animal bites** transmit diseases like rabies or certain bacterial infections, but not parasitic hookworms.
- Hookworm infection does not result from direct contact with an animal's saliva or puncture wound.
Protozoa/Helminths US Medical PG Question 4: A 68-year-old man presents to his physician for symptoms of chronic weight loss, abdominal bloating, and loose stools. He notes that he has also been bothered by a chronic cough. The patient’s laboratory work-up includes a WBC differential, which is remarkable for an eosinophil count of 9%. Stool samples are obtained, with ova and parasite examination revealing roundworm larvae in the stool and no eggs. Which of the following parasitic worms is the cause of this patient’s condition?
- A. Taenia saginata
- B. Taenia solium
- C. Strongyloides stercoralis (Correct Answer)
- D. Necator americanus
- E. Ascaris lumbricoides
Protozoa/Helminths Explanation: ***Strongyloides stercoralis***
- The presence of **larvae (rhabditiform)** in the stool, **pulmonary symptoms** (chronic cough), **gastrointestinal symptoms** (weight loss, bloating, loose stools), and **eosinophilia** are classic findings for *Strongyloides stercoralis* infection.
- Unlike most other intestinal nematodes, *Strongyloides* can establish an **autoinfection cycle**, meaning larvae can reinfect the host, leading to persistent and potentially severe infections even in immunocompetent individuals, without the need for external re-exposure or eggs in stool.
*Taenia saginata*
- This is a **tapeworm (cestode)** that causes taeniasis and is acquired by consuming undercooked beef.
- Diagnosis is typically made by finding **proglottids** or **eggs** in the stool, not larvae, and pulmonary symptoms are not characteristic.
*Taenia solium*
- This is another **tapeworm (cestode)**, acquired by consuming undercooked pork; it can cause taeniasis (intestinal infection) and cysticercosis (tissue infection).
- Similar to *T. saginata*, diagnosis involves finding **proglottids** or **eggs** in stool for intestinal infection, and it does not typically present with lung involvement or larvae in stool.
*Necator americanus*
- This is a **hookworm** that causes iron-deficiency anemia due to blood loss in the intestines.
- While it can cause some pulmonary symptoms as larvae migrate through the lungs, and gastrointestinal symptoms, the diagnostic hallmark is finding **eggs** in the stool, not larvae.
*Ascaris lumbricoides*
- This is the **giant roundworm**; infections are common and often asymptomatic, but heavy worm burdens can cause intestinal obstruction or malnutrition.
- While **pulmonary symptoms (Loeffler's syndrome)** can occur during larval migration, and eosinophilia is present, the diagnosis is confirmed by finding characteristic **mammillated eggs** in the stool, not larvae.
Protozoa/Helminths US Medical PG Question 5: A 30-year-old forest landscape specialist is brought to the emergency department with hematemesis and confusion. One week ago she was diagnosed with influenza when she had fevers, severe headaches, myalgias, hip and shoulder pain, and a maculopapular rash. After a day of relative remission, she developed abdominal pain, vomiting, and diarrhea. A single episode of hematemesis occurred prior to admission. Two weeks ago she visited rainforests and caves in western Africa where she had direct contact with animals, including apes. She has no history of serious illnesses or use of medications. She is restless. Her temperature is 38.0℃ (100.4℉); the pulse is 95/min, the respiratory rate is 20/min; and supine and upright blood pressure is 130/70 mm Hg and 100/65 mm Hg, respectively. Conjunctival suffusion is noted. Ecchymoses are observed on the lower extremities. She is bleeding from one of her intravenous lines. The peripheral blood smear is negative for organisms. Filovirus genomes were detected during a reverse transcription-polymerase chain reaction. The laboratory studies show the following:
Laboratory test
Hemoglobin 10 g/dL
Leukocyte count 1,000/mm3
Segmented neutrophils 65%
Lymphocytes 20%
Platelet count 50,000/mm3
Partial thromboplastin time (activated) 60 seconds
Prothrombin time 25 seconds
Fibrin split products positive
Serum
Alanine aminotransferase (ALT) 85 U/L
Aspartate aminotransferase (AST) 120 U/L
γ-Glutamyltransferase (GGT) 83 U/L
Creatinine 2 mg/dL
Which of the following is the most appropriate immediate step in management?
- A. Esophagogastroduodenoscopy
- B. Postexposure vaccination of close contacts
- C. Parenteral artesunate plus sulfadoxine/pyrimethamine
- D. Use of N95 masks
- E. Intravenous fluids and electrolytes (Correct Answer)
Protozoa/Helminths Explanation: ***Intravenous fluids and electrolytes***
- The patient presents with **orthostatic hypotension**, internal bleeding (hematemesis, ecchymoses), and deranged renal function (elevated creatinine). These indicate significant **fluid loss** and potential **hypovolemic shock**, making immediate fluid resuscitation critical.
- **Ebola virus disease** (indicated by the travel history, symptoms, and positive filovirus genomes) often leads to severe dehydration due to fluid loss from vomiting, diarrhea, and internal bleeding, necessitating aggressive fluid and electrolyte replacement as a cornerstone of supportive care.
*Esophagogastroduodenoscopy*
- While the patient has hematemesis, her overall clinical picture with **severe coagulopathy** (elevated PT/aPTT, low platelets, positive fibrin split products) and **multisystem involvement** suggests a systemic bleeding disorder rather than a focal upper GI bleed that would be the primary target of an EGD.
- Performing an invasive procedure like EGD in a patient with severe coagulopathy and a highly contagious disease like Ebola (implied by filovirus detection) carries significant risks and is not the most immediate priority compared to stabilizing vital signs and correcting fluid deficits.
*Postexposure vaccination of close contacts*
- This is a crucial public health measure for **Ebola virus disease** but is a secondary step in management focused on prevention for others, not the immediate stabilization or treatment of the acutely ill patient.
- While important, it does not address the patient's immediate, life-threatening symptoms of hypovolemia, bleeding, and organ dysfunction.
*Parenteral artesunate plus sulfadoxine/pyrimethamine*
- This regimen is an antimalarial treatment. While the patient traveled to Western Africa, her symptoms and the detection of **filovirus genomes** rule out malaria as the primary diagnosis requiring this specific treatment.
- Administering antimalarials would delay appropriate supportive care for Ebola virus disease and is not indicated given the specific viral diagnosis.
*Use of N95 masks*
- **N95 masks** are important for healthcare worker protection given the patient's symptoms and confirmed filovirus. However, the question asks for the most appropriate *immediate step in management* of the patient's condition.
- While infection control is paramount, providing immediate direct patient care like fluid resuscitation takes precedence for the patient's survival over PPE considerations, assuming adequate PPE is already being donned by healthcare providers.
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