Protozoa/Helminths Practice Questions

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?

Accepted Answer

Ebola virus

Answer

Zika virus

Answer

Plasmodium falciparum

Answer

Yersinia pestis

Answer

Babesia microti

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?

Accepted Answer

Plasmodium falciparum

Answer

Chikungunya virus

Answer

Trypanosoma cruzi

Answer

Leishmania donovani

Answer

Trypanosoma brucei

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?

Accepted Answer

Penetration of skin

Answer

Insect bite

Answer

Sexual contact

Answer

Inhalation

Answer

Animal bite

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?

Accepted Answer

Strongyloides stercoralis

Answer

Taenia saginata

Answer

Taenia solium

Answer

Necator americanus

Answer

Ascaris lumbricoides

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?

Accepted Answer

Intravenous fluids and electrolytes

Answer

Esophagogastroduodenoscopy

Answer

Postexposure vaccination of close contacts

Answer

Parenteral artesunate plus sulfadoxine/pyrimethamine

Answer

Use of N95 masks

Question 6

A 31-year-old woman presents to your office with one week of recurrent fevers. The highest temperature she recorded was 101°F (38.3°C). She recently returned from a trip to Nigeria to visit family and recalls a painful bite on her right forearm at that time. Her medical history is significant for two malarial infections as a child. She is not taking any medications. On physical examination, her temperature is 102.2°F (39°C), blood pressure is 122/80 mmHg, pulse is 80/min, respirations are 18/min, and pulse oximetry is 99% on room air. She has bilateral cervical lymphadenopathy and a visible, enlarged, mobile posterior cervical node. Cardiopulmonary and abdominal examinations are unremarkable. She has an erythematous induration on her right forearm. The most likely cause of this patient's symptoms can be treated with which of the following medications?

Accepted Answer

Fexinidazole

Answer

Sulfadiazine and pyrimethamine

Answer

Atovaquone and azithromycin

Answer

Primaquine

Answer

Chloroquine

Question 7

A 58-year-old female, being treated on the medical floor for community-acquired pneumonia with levofloxacin, develops watery diarrhea. She reports at least 9 episodes of diarrhea within the last two days, with lower abdominal discomfort and cramping. Her temperature is 98.6° F (37° C), respiratory rate is 15/min, pulse is 67/min, and blood pressure is 122/98 mm Hg. Her physical examination is unremarkable. Laboratory testing shows:
Hb%   13 gm/dL
Total count (WBC):   13,400/mm3
Differential count:    
  Neutrophils: 80%
  Lymphocytes: 15%
  Monocytes: 5%
ESR:   33 mm/hr
What is the most likely diagnosis?

Accepted Answer

C. difficile colitis

Answer

Ulcerative colitis

Answer

Osmotic diarrhea

Answer

Giardiasis

Answer

Irritable bowel syndrome

Question 8

A 54-year-old man comes to the physician because of diarrhea that has become progressively worse over the past 4 months. He currently has 4–6 episodes of foul-smelling stools per day. Over the past 3 months, he has had fatigue and a 5-kg (11-lb) weight loss. He returned from Bangladesh 6 months ago after a year-long business assignment. He has osteoarthritis and hypertension. Current medications include amlodipine and naproxen. He appears pale and malnourished. His temperature is 37.3°C (99.1°F), pulse is 76/min, and blood pressure is 140/86 mm Hg. Examination shows pale conjunctivae and dry mucous membranes. Angular stomatitis and glossitis are present. The abdomen is distended but soft and nontender. Rectal examination shows no abnormalities. Laboratory studies show:
Hemoglobin 8.9 g/dL
Leukocyte count 4100/mm3
Platelet count 160,000/mm3
Mean corpuscular volume 110 μm3
Serum
Na+ 133 mEq/L
Cl- 98 mEq/l
K+ 3.3 mEq/L
Creatinine 1.1 mg/dL
IgA 250 mg/dL
Anti-tissue transglutaminase, IgA negative
Stool culture and studies for ova and parasites are negative. Test of the stool for occult blood is negative. Fecal fat content is 22 g/day (N < 7). Fecal lactoferrin is negative and elastase is within normal limits. Which of the following is the most appropriate next step in diagnosis?

Accepted Answer

PAS-stained biopsy of small bowel

Answer

CT scan of the abdomen

Answer

IgG against deamidated gliadin peptide

Answer

Schilling test

Answer

Enteroscopy

Question 9

A 32-year-old woman comes to the emergency department with a 2-day history of abdominal pain and diarrhea. She has had about 8 voluminous stools per day, some of which were bloody. She visited an international food festival three days ago. She takes no medications. Her temperature is 39.5°C (103.1°F), pulse is 90/min, and blood pressure is 110/65 mm Hg. Examination shows a tender abdomen, increased bowel sounds, and dry mucous membranes. Microscopic examination of the stool shows polymorphonuclear leukocytes. Stool culture results are pending. Which of the following most likely caused the patient's symptoms?

Accepted Answer

Omelette

Answer

Home-canned vegetables

Answer

Yogurt dip

Answer

Reheated rice

Answer

Toxic mushrooms

Question 10

A previously healthy 24-year-old woman comes to the physician because of a 1-day history of nausea and weakness. She is sexually active with 2 male partners and uses an oral contraceptive; she uses condoms inconsistently. Her last menstrual period was 4 days ago. Her temperature is 38.4°C (101°F). Physical examination shows right costovertebral angle tenderness. Pelvic examination is normal. Which of the following is the most likely cause of this patient's condition?

Accepted Answer

Ascending bacteria from the bladder

Answer

Noninfectious inflammation of the bladder

Answer

Ascending bacteria from the endocervix

Answer

Decreased renal calcium reabsorption

Answer

Decreased urinary pH

Protozoa/Helminths

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Malaria parasites and life cycle

Intestinal protozoa (Giardia, Entamoeba)

Toxoplasma gondii

Trypanosomes

Leishmania species

Nematodes (roundworms)

Cestodes (tapeworms)

Trematodes (flukes)

Blood and tissue parasites

Antiparasitic medications

Laboratory diagnosis of parasites

Global health impact of parasitic infections

Ectoparasites and vector-borne diseases

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About Protozoa/Helminths for USMLE

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