Protozoa/Helminths

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 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 3: 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 4: 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.

Protozoa/Helminths US Medical PG Question 5: 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?

• A. Sulfadiazine and pyrimethamine
• B. Atovaquone and azithromycin
• C. Primaquine
• D. Chloroquine
• E. Fexinidazole (Correct Answer)

Protozoa/Helminths Explanation: ***Fexinidazole*** - This patient's symptoms (recurrent fevers, cervical lymphadenopathy, erythematous induration after a trip to Nigeria with a painful bite) are highly suggestive of **African trypanosomiasis (sleeping sickness)**. - **Fexinidazole** is an oral nitroimidazole derivative approved for treating both first and second-stage human African trypanosomiasis (HAT) caused by *Trypanosoma brucei gambiense*. *Sulfadiazine and pyrimethamine* - This combination is primarily used to treat **toxoplasmosis**, an infection caused by the parasite *Toxoplasma gondii*. - While it can cause fever and lymphadenopathy, the travel history to Nigeria and a "painful bite" are not typical for toxoplasmosis transmission. *Atovaquone and azithromycin* - This combination is utilized for treating **Babesiosis**, a tick-borne parasitic infection. - While Babesiosis can cause fever and fatigue, the characteristic erythematous induration and prominent lymphadenopathy point away from this diagnosis. *Primaquine* - **Primaquine** is an antimalarial drug specifically used for the **radical cure of *Plasmodium vivax*** and ***Plasmodium ovale*** malaria, targeting the hypnozoite liver stages. - Although the patient has a history of malaria and a travel history to an endemic area, the current presentation with distinct lymphadenopathy and skin lesion points away from a straightforward malarial relapse or new infection primarily requiring primaquine as the sole treatment. *Chloroquine* - **Chloroquine** is an antimalarial drug, but its use is limited primarily to areas where **chloroquine-sensitive *Plasmodium falciparum*** strains are prevalent. - While the patient traveled to Nigeria, a region where malaria is endemic, the specific constellation of symptoms, including the bite and lymphadenopathy, is less characteristic of typical malaria than of trypanosomiasis.

Protozoa/Helminths US Medical PG Question 6: 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?

• A. Ulcerative colitis
• B. C. difficile colitis (Correct Answer)
• C. Osmotic diarrhea
• D. Giardiasis
• E. Irritable bowel syndrome

Protozoa/Helminths Explanation: ***C. difficile colitis*** - The patient's recent **antibiotic use (levofloxacin)**, followed by the development of **watery diarrhea** (9 episodes in 2 days) with abdominal cramping, is highly suggestive of *Clostridioides difficile* infection. - The elevated **WBC count (13,400/mm3)** and **ESR (33 mm/hr)** indicate an inflammatory response, which is common in *C. difficile* colitis. *Ulcerative colitis* - Ulcerative colitis typically presents with **bloody diarrhea**, abdominal pain, and tenesmus, usually with a more chronic or relapsing course, which is not described. - While it can manifest with flares, the direct temporal relationship with **antibiotic use** and the lack of bloody stools make it less likely. *Osmotic diarrhea* - Osmotic diarrhea is often related to the ingestion of **non-absorbable substances** (e.g., lactulose, sorbitol) or malabsorption and generally resolves with fasting. - It is not typically associated with a significant **inflammatory response** (elevated WBC, ESR) or a clear link to recent antibiotic use. *Giardiasis* - Giardiasis is a parasitic infection that causes **protozoal diarrhea**, often characterized by foul-smelling, fatty stools, flatulence, and abdominal cramps. - It is usually acquired from contaminated water and typically doesn't follow **antibiotic therapy** in this manner. *Irritable bowel syndrome* - IBS is a functional gastrointestinal disorder characterized by **chronic abdominal pain** and altered bowel habits (diarrhea, constipation, or both) in the absence of structural or biochemical abnormalities. - It does not present as an acute, severe diarrheal illness linked to **antibiotic use** with systemic inflammatory markers.

Protozoa/Helminths US Medical PG Question 7: 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?

• A. CT scan of the abdomen
• B. IgG against deamidated gliadin peptide
• C. Schilling test
• D. Enteroscopy
• E. PAS-stained biopsy of small bowel (Correct Answer)

Protozoa/Helminths Explanation: ***PAS-stained biopsy of small bowel*** - The patient's history of travel to Bangladesh, chronic diarrhea, malabsorption (weight loss, fatigue, elevated fecal fat, macrocytic anemia), and negative celiac serology (anti-tissue transglutaminase IgA) are highly suggestive of **Whipple's disease**. - **Periodic Acid-Schiff (PAS) staining** of a small bowel biopsy is the gold standard for diagnosing Whipple's disease, revealing **PAS-positive macrophages** containing *Tropheryma whipplei*. *CT scan of the abdomen* - While a CT scan can identify structural abnormalities or masses, it is not the most direct diagnostic test for **malabsorptive conditions** like Whipple's disease. - It would likely show non-specific findings such as **bowel wall thickening** or **lymphadenopathy**, but not the definitive histological changes. *IgG against deamidated gliadin peptide* - This test is used to diagnose **celiac disease**, but the patient's IgA anti-tissue transglutaminase was already negative, and this IgG test is typically performed when IgA deficiency is suspected or in young children. - Given the strong suspicion of an infectious etiology due to travel history and systemic symptoms, focusing solely on celiac serology is less appropriate as the first next step. *Schilling test* - The Schilling test is an **obsolete test** that was historically used to assess **vitamin B12 absorption** and differentiate causes of B12 deficiency (pernicious anemia, bacterial overgrowth, or pancreatic insufficiency). - This test is **no longer performed in clinical practice** due to unavailability of radioactive B12; modern evaluation uses serum B12, methylmalonic acid, and homocysteine levels. - While the patient has macrocytic anemia, the test would not directly address the underlying cause of fat malabsorption and systemic symptoms present. *Enteroscopy* - Enteroscopy allows for visualization and biopsy of the small bowel beyond the reach of a standard upper endoscopy. - While useful for obtaining biopsies, simply performing an enteroscopy without knowing what to look for or what specific stain to request (referring to PAS) on the biopsy would be less targeted than ordering a **PAS-stained biopsy** specifically.

Protozoa/Helminths US Medical PG Question 8: 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?

• A. Home-canned vegetables
• B. Yogurt dip
• C. Reheated rice
• D. Toxic mushrooms
• E. Omelette (Correct Answer)

Protozoa/Helminths Explanation: **Omelette** - The symptoms, including **bloody diarrhea**, fever, and exposure to an international food festival suggest a **bacterial infection**, likely from contaminated eggs (e.g., **Salmonella**). - The presence of **polymorphonuclear leukocytes** in the stool indicates an **invasive bacterial infection**, consistent with salmonellosis. *Home-canned vegetables* - Poorly preserved home-canned vegetables are a classic cause of **botulism**, which presents with **neurological symptoms** (e.g., flaccid paralysis) and is not characterized by bloody diarrhea or fever. - While it can cause gastrointestinal upset, bloody stools are not typical, and the primary concern is neurotoxicity due to **Clostridium botulinum toxin**. *Yogurt dip* - Yogurt is a dairy product, and contamination typically leads to **non-bloody diarrhea** and vomiting, often caused by bacteria like *Staphylococcus aureus* or *Bacillus cereus* producing enterotoxins. - The symptoms would likely be less severe and lack the invasive features (bloody stools, fever, PMNs) seen in this patient. *Reheated rice* - Reheated rice is commonly associated with **Bacillus cereus** food poisoning, which typically causes either an emetic (vomiting) or diarrheal syndrome. - The diarrhea caused by *Bacillus cereus* is usually **watery and non-bloody**, and it rarely presents with significant fever or invasive features like polymorphonuclear leukocytes in stool. *Toxic mushrooms* - Mushroom poisoning can present with a wide range of symptoms, including gastrointestinal distress (vomiting, diarrhea), but the presentation varies greatly depending on the mushroom species. - **Bloody diarrhea** with fever and polymorphonuclear leukocytes in stool is not a typical hallmark of common toxic mushroom ingestions, which often involve hepatotoxicity or neurotoxicity.

Protozoa/Helminths US Medical PG Question 9: 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?

• A. Noninfectious inflammation of the bladder
• B. Ascending bacteria from the endocervix
• C. Decreased renal calcium reabsorption
• D. Decreased urinary pH
• E. Ascending bacteria from the bladder (Correct Answer)

Protozoa/Helminths Explanation: ***Ascending bacteria from the bladder*** - The patient presents with **fever**, **nausea**, **weakness**, and **right costovertebral angle (CVA) tenderness**, which are classic symptoms of **acute pyelonephritis**. - **Pyelonephritis** most commonly results from an **ascending urinary tract infection**, where bacteria (typically *E. coli*) from the bladder travel up the ureters to infect the kidneys. - This accounts for approximately **95% of pyelonephritis cases** in young women. *Noninfectious inflammation of the bladder* - **Noninfectious cystitis** (interstitial cystitis) would not typically present with systemic symptoms like **fever** and **nausea**, or with **CVA tenderness**, which indicates kidney involvement. - Bladder inflammation typically causes dysuria and frequency without systemic signs of infection. *Ascending bacteria from the endocervix* - **Ascending bacteria from the endocervix** can cause **pelvic inflammatory disease (PID)**, which presents with lower abdominal pain, cervical motion tenderness, and vaginal discharge. - While PID can cause fever, the **normal pelvic examination** in this patient rules out this diagnosis, and PID **does not typically cause CVA tenderness**. *Decreased renal calcium reabsorption* - **Decreased renal calcium reabsorption** is associated with **hypercalciuria** and **nephrolithiasis** (kidney stones), which can present with acute flank pain if obstruction occurs. - However, this condition does not explain the **fever** and systemic symptoms characteristic of an acute infectious process. *Decreased urinary pH* - **Decreased urinary pH** (acidic urine) can predispose to certain types of kidney stone formation but is not a direct cause of **pyelonephritis**. - It does not explain the presence of **fever**, **CVA tenderness**, and systemic symptoms indicative of a bacterial kidney infection.

Protozoa/Helminths US Medical PG Question 10: A 16-year-old female presents to her pediatrician complaining of 2 weeks of fever and 1 week of swollen lumps in her left armpit. Upon examination of the left upper extremity, her physician notes the presence of a single papule which the patient claimed appeared one week ago. The patient started her first job at a pet store 2.5 weeks ago. Which of the following is the vector of transmission of the causative agent?

• A. Cats (Correct Answer)
• B. Rabbits
• C. Animal urine
• D. Parrots
• E. Armadillos

Protozoa/Helminths Explanation: ***Cats*** - The combination of **fever**, **swollen lymph nodes** (lumps in the armpit), a **single papule**, and a recent history of working at a **pet store** strongly suggests **cat scratch disease**. - **Cat scratch disease** is caused by *Bartonella henselae*, which is primarily transmitted to humans through the **scratch or bite of a cat**, especially kittens. *Rabbits* - Rabbits are known vectors for diseases like **tularemia**, which can cause fever and swollen lymph nodes. - However, the typical presentation of tularemia often includes a more prominent **ulcerative lesion** at the site of inoculation, and the papule described is less characteristic. *Animal urine* - While animal urine can transmit diseases like **leptospirosis**, which can cause fever and various systemic symptoms, it typically does not present with a localized papule followed by regional lymphadenopathy in this manner. - Exposure to animal urine usually occurs through contact with contaminated water or soil, and the pet store context points more towards direct animal contact. *Parrots* - Parrots are associated with **psittacosis** (parrot fever), caused by *Chlamydia psittaci*. - Psittacosis primarily manifests as a **respiratory illness** (pneumonia) and does not typically present with a localized papule and regional lymphadenopathy. *Armadillos* - Armadillos are significant reservoirs for **Mycobacterium leprae**, the causative agent of **leprosy**. - Leprosy has a very long incubation period and presents with skin lesions, nerve damage, and sometimes lymphadenopathy, but a 2-week onset and the described acute symptoms are inconsistent with leprosy.

Protozoa/Helminths Flashcard 1 of 10

Question: Which species of helminths migrate against portal blood flow?_____

Answer: Schistosoma spp.

Protozoa/Helminths Flashcard 2 of 10

Question: Which protozoa causes visceral leishmaniasis?_____

Answer: Leishmania donovani

Protozoa/Helminths Flashcard 3 of 10

Question: _____ is a helminth, treated with albendazole, that can result in biliary tree abnormalities

Answer: Ascaris lumbricoides (giant roundworm)

Protozoa/Helminths Flashcard 4 of 10

Question: Entamoeba histolytica is most common in _____ countries

Answer: developing (developed or developing)

Protozoa/Helminths Flashcard 5 of 10

Question: Diagnosis of Plasmodium spp. includes blood smear or _____ stain

Answer: giemsa

Protozoa/Helminths Flashcard 6 of 10

Question: What is an ELISA looking for when testing for Giardia?_____

Answer: Stool antigens

Protozoa/Helminths Flashcard 7 of 10

Question: Schistosoma spp. is a _____ fluke

Answer: blood

Protozoa/Helminths Flashcard 8 of 10

Question: Toxoplasma gondii is an obligate _____ parasitic protozoa that causes toxoplasmosis

Answer: intracellular

Protozoa/Helminths Flashcard 9 of 10

Question: Trichomonas vaginalis

Answer:

Extra Information: wet mountvaginitissexual

Protozoa/Helminths Flashcard 10 of 10

Question: trichomonas vaginitis

Answer:

Extra Information: foul-smelling, greenish vaginal discharge, itching and burningmobile, pear-shaped trophozoites on wet mountmetronidazole