Echinococci and other tissue helminths US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Echinococci and other tissue helminths. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Echinococci and other tissue helminths US Medical PG Question 1: A 4-year-old girl presents with recurrent abdominal pain and a low-grade fever for the past 2 months. The patient’s mother says that she has lost her appetite which has caused some recent weight loss. She adds that the patient frequently plays outdoors with their pet dog. The patient is afebrile and vital signs are within normal limits. On physical examination, conjunctival pallor is present. Abdominal examination reveals a diffusely tender abdomen and significant hepatomegaly. There is also a solid mass palpable in the right upper quadrant measuring about 3 x 4 cm. Laboratory findings are significant for the following:
Hemoglobin (Hb%) 9.9 g/dL
Total count (WBC) 26,300/µL
Differential count
Neutrophils 36%
Lymphocytes 16%
Eosinophils 46%
Platelets 200,000/mm3
Erythrocyte sedimentation rate 56 mm/h
C-reactive protein 2 mg/L
Serum globulins 5 g/dL
Laparoscopic resection of the mass is performed, and a tissue sample is sent for histopathology. Which of the following is the organism most likely responsible for this patient’s condition?
- A. Ancylostoma braziliense
- B. Ascaris lumbricoides
- C. Toxocara canis (Correct Answer)
- D. Trichuris trichiura
- E. Toxocara cati
Echinococci and other tissue helminths Explanation: ***Toxocara canis***
- The child's history of playing outdoors with a pet dog, **eosinophilia**, **hepatomegaly**, abdominal mass, and **elevated globulins** are highly suggestive of **visceral larva migrans (VLM)**, most commonly caused by *Toxocara canis*.
- *Toxocara canis* larvae migrate through human tissues, particularly the liver, causing granuloma formation that can present as palpable masses and systemic symptoms.
*Ancylostoma braziliense*
- This hookworm primarily causes **cutaneous larva migrans**, presenting as an intensely pruritic, serpiginous rash.
- It does not typically cause systemic symptoms like hepatomegaly, abdominal masses, or significant eosinophilia in the way described.
*Ascaris lumbricoides*
- *Ascaris lumbricoides* causes **ascariasis**, primarily manifesting as intestinal symptoms, malnutrition, or pulmonary symptoms during larval migration (Löffler syndrome)
- While it can cause eosinophilia, it rarely presents with solid hepatic masses or the specific constellation of symptoms seen here.
*Trichuris trichiura*
- *Trichuris trichiura* causes **trichuriasis** (whipworm infection), primarily leading to **gastrointestinal symptoms** such as abdominal pain, diarrhea, and rectal prolapse in heavy infections.
- It is not associated with migratory visceral larvae, hepatomegaly, or palpable liver masses.
*Toxocara cati*
- While *Toxocara cati* also causes visceral larva migrans, it is associated with **cats** rather than dogs. The patient's history specifically mentions a pet dog.
- The clinical presentation with hepatomegaly, abdominal mass, and eosinophilia would otherwise be consistent with *Toxocara* infection.
Echinococci and other tissue helminths US Medical PG Question 2: A 42-year-old woman comes to the physician because of episodic abdominal pain and fullness for 1 month. She works as an assistant at an animal shelter and helps to feed and bathe the animals. Physical examination shows hepatomegaly. Abdominal ultrasound shows a 4-cm calcified cyst with several daughter cysts in the liver. She undergoes CT-guided percutaneous aspiration under general anesthesia. Several minutes into the procedure, one liver cyst spills, and the patient's oxygen saturation decreases from 95% to 64%. Her pulse is 136/min, and blood pressure is 86/58 mm Hg. Which of the following is the most likely causal organism of this patient's condition?
- A. Clonorchis sinensis
- B. Trichinella spiralis
- C. Echinococcus granulosus (Correct Answer)
- D. Strongyloides stercoralis
- E. Schistosoma mansoni
Echinococci and other tissue helminths Explanation: ***Echinococcus granulosus***
- The presentation of a **calcified liver cyst** with **daughter cysts** in a patient with animal exposure (**animal shelter worker**) is highly suggestive of **hydatid disease** caused by *Echinococcus granulosus*.
- The **anaphylactic-like reaction** (decreased oxygen saturation, hypotension, tachycardia) upon cyst spillage during aspiration is a classic and dangerous complication, indicating a severe allergic response to the **hydatid fluid**.
*Clonorchis sinensis*
- This parasite causes **cholangitis** and **cholangiocarcinoma**, and typically presents with symptoms related to biliary obstruction, rather than large calcified cysts with daughter cysts.
- It is acquired by eating **undercooked freshwater fish** and is endemic in East Asia, which doesn't align with the patient's exposure history or cyst morphology.
*Trichinella spiralis*
- This parasite is acquired by consuming **undercooked pork** and causes **trichinosis**, characterized by muscle pain, periorbital edema, and eosinophilia, and does not typically form liver cysts.
- Liver involvement with *Trichinella* is rare and does not manifest as calcified cysts with daughter cysts.
*Strongyloides stercoralis*
- This nematode causes **strongyloidiasis**, often manifesting as gastrointestinal symptoms, skin rash (**larva currens**), and pulmonary symptoms in cases of autoinfection.
- It does not form macroscopic liver cysts, and liver involvement is generally non-cystic.
*Schistosoma mansoni*
- Causes **schistosomiasis**, which can lead to **hepatic fibrosis** (**pipestem fibrosis**) and **portal hypertension**, but does not typically cause large, calcified hydatid-like cysts with daughter cysts.
- Infection is acquired through contact with **freshwater contaminated with snails** carrying the parasitic larvae.
Echinococci and other tissue helminths US Medical PG Question 3: A 45-year-old man comes to the physician because of a 5-day history of fever, malaise, and right upper abdominal pain. Examination of the abdomen shows tenderness in the right upper quadrant. His leukocyte count is 18,000/mm3 (90% neutrophils) and serum alkaline phosphatase is 130 U/L. Ultrasonography of the abdomen shows a 3-cm hypoechoic lesion in the right lobe of the liver with a hyperemic rim. Which of the following is the most likely underlying cause of this patient's condition?
- A. Diverticulitis
- B. Echinococcosis
- C. Pyogenic liver abscess
- D. Cholangitis (Correct Answer)
- E. Perinephric infection
Echinococci and other tissue helminths Explanation: The patient presents with a **pyogenic liver abscess** (fever, RUQ pain, leukocytosis, hypoechoic liver lesion with hyperemic rim). The question asks for the **underlying cause** of this abscess.
***Cholangitis***
- **Cholangitis** (ascending biliary infection) is the **most common underlying cause** of pyogenic liver abscesses, accounting for 40-60% of cases
- The elevated **alkaline phosphatase** (130 U/L) suggests **biliary tract pathology**, supporting cholangitis as the source
- Bacteria ascend from the biliary tree through the portal venous system to seed the liver parenchyma
- The **leukocytosis with neutrophilia** (18,000/mm³, 90% neutrophils) indicates acute bacterial infection
- **Clinical correlation**: Biliary obstruction from stones, strictures, or malignancy → cholangitis → hematogenous/direct spread → liver abscess
*Diverticulitis*
- **Diverticulitis** typically causes **left lower quadrant pain** and fever, not right upper quadrant symptoms
- While portal pylephlebitis from diverticulitis can rarely cause liver abscesses, the **elevated alkaline phosphatase** points more toward biliary pathology than colonic source
- Absence of GI symptoms (diarrhea, constipation, lower abdominal pain) makes this less likely
*Echinococcosis*
- **Echinococcosis** (hydatid cyst) presents with a **slow-growing, asymptomatic cyst** over months to years, not acute fever
- Imaging shows **multiloculated cysts with daughter cysts** and calcifications ("water lily sign"), not a hyperemic rim suggesting acute inflammation
- Would not cause marked leukocytosis unless the cyst ruptures
*Pyogenic liver abscess*
- This is the **condition the patient HAS**, not the underlying cause
- A pyogenic liver abscess is the result of bacterial seeding, which can occur from biliary sources (cholangitis), hematogenous spread, or direct extension
- The question asks for what **caused** the abscess, not what the abscess is
*Perinephric infection*
- **Perinephric abscess** causes **flank pain** and costovertebral angle tenderness, not RUQ pain
- Imaging would show perirenal or intrarenal findings, not an **isolated liver lesion**
- No urinary symptoms are mentioned
Echinococci and other tissue helminths US Medical PG Question 4: Nucleic acid amplification testing (NAAT) of first-void urine confirms infection with Chlamydia trachomatis. Treatment with the appropriate pharmacotherapy is started. Which of the following health maintenance recommendations is most appropriate at this time?
- A. Take medication with food
- B. Avoid sun exposure
- C. Avoid drinking alcohol
- D. Avoid sexual activity for the next month (Correct Answer)
- E. Schedule an ophthalmology consultation
Echinococci and other tissue helminths Explanation: ***Avoid sexual activity for the next month***
- **CDC guidelines** recommend abstinence from sexual activity until 7 days after treatment completion AND until all sexual partners have been treated and cured. The recommendation of "the next month" provides adequate time to ensure both conditions are met, as **partner notification**, testing, and treatment often takes several weeks.
- This is the **most important health maintenance recommendation** as preventing **reinfection** and further **transmission** is the primary public health concern, superseding medication-specific advice.
*Take medication with food*
- This recommendation is specific to certain antibiotics to reduce gastrointestinal upset or improve absorption, but it is not a universal health maintenance recommendation for all Chlamydia treatments (e.g., **azithromycin** can be taken with or without food; **doxycycline** should be taken with food to reduce GI upset, but not milk products).
- While relevant to **medication adherence**, it is not the most crucial health maintenance advice regarding preventing transmission or re-infection.
*Avoid sun exposure*
- This advice is primarily given for medications that cause **photosensitivity**, such as **doxycycline**, which is a common treatment for Chlamydia.
- However, it's not applicable to all Chlamydia treatments (e.g., **azithromycin**) and is not the most critical health recommendation in the context of preventing disease transmission.
*Avoid drinking alcohol*
- This is a general recommendation for many antibiotic treatments to prevent potential interactions or increased side effects, but it is not a specific contraindication for the primary antibiotics used for Chlamydia.
- **Metronidazole**, used for other STIs (e.g., trichomoniasis), has a strong interaction with alcohol. However, it's not the primary treatment for Chlamydia, making this recommendation less universally appropriate here.
*Schedule an ophthalmology consultation*
- While Chlamydia can cause **conjunctivitis** (ophthalmia neonatorum in newborns or adult inclusion conjunctivitis), it is not a typical complication requiring routine ophthalmology consultation unless specific **ocular symptoms** are present.
- This recommendation is not a standard health maintenance strategy for **uncomplicated Chlamydia infections**.
Echinococci and other tissue helminths US Medical PG Question 5: A 38-year-old man comes to the physician because of a 2-week history of abdominal pain and an itchy rash on his buttocks. He also has fever, nausea, and diarrhea with mucoid stools. One week ago, the patient returned from Indonesia, where he went for vacation. Physical examination shows erythematous, serpiginous lesions located in the perianal region and the posterior thighs. His leukocyte count is 9,000/mm3 with 25% eosinophils. Further evaluation is most likely to show which of the following findings?
- A. Rhabditiform larvae on stool microscopy (Correct Answer)
- B. Entamoeba histolytica antibodies on stool immunoassay
- C. Branching septate hyphae on KOH preparation
- D. Oocysts on acid-fast stool stain
- E. Giardia lamblia antibodies on stool immunoassay
Echinococci and other tissue helminths Explanation: ***Rhabditiform larvae on stool microscopy***
- The patient's symptoms, including **abdominal pain**, **diarrhea with mucoid stools**, **itchy rash (larva currens)**, and **eosinophilia** after traveling to Indonesia, are highly suggestive of **Strongyloidiasis**.
- **Rhabditiform larvae** are typically found in stool samples during the diagnostic phase of strongyloidiasis, as adult worms live in the small intestine and release these larvae.
*Entamoeba histolytica antibodies on stool immunoassay*
- While *Entamoeba histolytica* can cause **dysentery**, **abdominal pain**, and fever, it does not cause an **itchy migratory rash** or significant **eosinophilia**.
- Diagnosis typically involves detecting **trophozoites or cysts** in stool or specific **antigen detection**, not usually antibodies in stool.
*Branching septate hyphae on KOH preparation*
- **Branching, septate hyphae** are characteristic of **fungal infections**, such as dermatophytosis, which primarily affect the skin.
- This finding would not explain the systemic symptoms like **abdominal pain**, **diarrhea**, **fever**, and eosinophilia described in the patient.
*Oocysts on acid-fast stool stain*
- **Oocysts detected by acid-fast stain** are indicative of parasitic infections like **Cryptosporidiosis** or **Cyclosporiasis**, which cause **watery diarrhea** and abdominal cramps.
- These infections do not typically present with the **pruritic serpiginous rash** (larva currens) or the high level of **eosinophilia** seen in this patient.
*Giardia lamblia antibodies on stool immunoassay*
- *Giardia lamblia* causes **giardiasis**, characterized by **diarrhea**, **abdominal cramps**, **bloating**, and **malabsorption**.
- However, giardiasis typically does not cause **eosinophilia** or an **itchy migratory rash**, which are key features in this case.
Echinococci and other tissue helminths US Medical PG Question 6: A 22-year-old man comes to the physician because of abdominal pain, diarrhea, and weight loss that started after a recent backpacking trip in Southeast Asia. He does not smoke or drink alcohol. His leukocyte count is 7,500/mm3 (61% segmented neutrophils, 13% eosinophils, and 26% lymphocytes). Stool microscopy shows rhabditiform larvae. This patient is most likely to develop which of the following?
- A. Perianal serpiginous rash (Correct Answer)
- B. Hematuria
- C. Rectal prolapse
- D. Peripheral lymphedema
- E. Muscle tenderness
Echinococci and other tissue helminths Explanation: ***Perianal serpiginous rash***
- The patient's symptoms (abdominal pain, diarrhea, weight loss, recent travel to Southeast Asia, eosinophilia, and rhabditiform larvae in stool) are highly suggestive of **Strongyloidiasis**.
- The **rhabditiform larvae** of **Strongyloides stercoralis** can autoinfect the host, migrating through the skin from the perianal area, causing a characteristic **larva currens** or **perianal serpiginous rash**.
*Hematuria*
- **Hematuria** is typically associated with **Schistosomiasis** (especially *Schistosoma haematobium*), which involves the genitourinary tract.
- While schistosomiasis is prevalent in some parts of Southeast Asia, the patient's presentation with **rhabditiform larvae** and **eosinophilia** points away from it.
*Rectal prolapse*
- **Rectal prolapse** can occur with chronic straining due to severe diarrhea or constipation, or in conditions like **Trichuriasis (whipworm infection)**.
- While diarrhea is present, the specific finding of **rhabditiform larvae** and the high eosinophil count are not characteristic of conditions directly leading to rectal prolapse.
*Peripheral lymphedema*
- **Peripheral lymphedema** is a hallmark symptom of **Filariasis**, caused by parasitic worms like *Wuchereria bancrofti* or *Brugia malayi*, transmitted by mosquitoes.
- The patient's presentation, particularly the **rhabditiform larvae in stool**, does not support a diagnosis of filariasis.
*Muscle tenderness*
- **Muscle tenderness** and myalgia can be associated with several parasitic infections, most notably **Trichinellosis**, caused by *Trichinella spiralis*.
- However, the finding of **rhabditiform larvae in stool** and the absence of specific symptoms like periorbital edema or splinter hemorrhages make trichinellosis less likely than strongyloidiasis.
Echinococci and other tissue helminths US Medical PG Question 7: A 45-year-old man with a history of poorly controlled human immunodeficiency virus (HIV) infection presents to the emergency room complaining of clumsiness and weakness. He reports a 3-month history of worsening balance, asymmetric muscle weakness, and speech difficulties. He recently returned from a trip to Guatemala to visit his family. He has been poorly compliant with his anti-retroviral therapy and his most recent CD4 count was 195. His history is also notable for rheumatoid arthritis and hepatitis C. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 95/min, and respirations are 18/min. On exam, he has 4/5 strength in his right upper extremity, 5/5 strength in his left upper extremity, 5/5 strength in his right lower extremity, and 3/5 strength in his left lower extremity. His speech is disjointed with intermittent long pauses between words. Vision is 20/100 in the left eye and 20/40 in his right eye; previously, his eyesight was 20/30 bilaterally. This patient most likely has a condition caused by which of the following types of pathogens?
- A. Arenavirus
- B. Bunyavirus
- C. Herpesvirus
- D. Polyomavirus (Correct Answer)
- E. Picornavirus
Echinococci and other tissue helminths Explanation: ***Polyomavirus***
- The patient's **poorly controlled HIV**, **low CD4 count (195)**, and progressive neurological symptoms (clumsiness, weakness, speech difficulties, vision changes) are highly suggestive of **Progressive Multifocal Leukoencephalopathy (PML)**.
- PML is caused by the **JC virus**, which is a type of **polyomavirus**, typically reactivating in immunocompromised individuals.
*Arenavirus*
- Arenaviruses (e.g., Lassa fever virus) are known to cause **hemorrhagic fevers** and can lead to neurological complications, but the clinical presentation described (progressive focal neurological deficits in an HIV patient) is not typical for an arenavirus infection.
- While some arenaviruses cause **meningoencephalitis**, the progressive, demyelinating-like course seen in this patient points away from arenavirus.
*Bunyavirus*
- Bunyaviruses (e.g., Hantavirus, La Crosse encephalitis virus) can cause **encephalitis**, fever, and myalgia, but they don't typically present with the specific constellation of **progressive white matter lesions** and focal neurological signs characteristic of PML in an HIV patient.
- Hantaviruses are more associated with **hemorrhagic fever with renal syndrome** or **hantavirus cardiopulmonary syndrome**.
*Herpesvirus*
- While herpesviruses (e.g., HSV, CMV, VZV) can cause severe neurological disease in HIV patients (e.g., **CMV encephalitis**, **HSV encephalitis**, **VZV vasculopathy**), the described progressive multifocal deficits, especially with rapid worsening, in an HIV patient with a low CD4 count strongly favor PML.
- Herpesviral encephalitides often present with more acute onset, fever, and seizures, or specific radiographic patterns not directly matching PML.
*Picornavirus*
- Picornaviruses, such as enteroviruses, can cause **aseptic meningitis** or **encephalitis**, particularly in immunocompromised individuals.
- However, the progressive, multifocal neurological deficits, particularly affecting **white matter**, are not characteristic of picornavirus infections, which tend to cause more diffuse or acute inflammatory processes.
Echinococci and other tissue helminths US Medical PG Question 8: A 41-year-old male with a history of Pneumocystis jirovecii pneumonia is found to have multiple ring-enhancing lesions on brain CT. Which of the following is most likely responsible for this patient's abnormal scan?
- A. Protozoa (Correct Answer)
- B. Virus
- C. Neoplasm
- D. Bacteria
- E. Prion
Echinococci and other tissue helminths Explanation: ***Protozoa***
- The patient's history of **Pneumocystis jirovecii pneumonia** (PJP) suggests an **immunocompromised state**, likely due to HIV/AIDS.
- In such patients, **ring-enhancing brain lesions** are highly characteristic of **cerebral toxoplasmosis**, an opportunistic infection caused by the protozoan *Toxoplasma gondii*.
*Virus*
- While viruses like **CMV** or **JC virus** (causing PML) can affect the brain in immunocompromised patients, they typically present with different imaging features (e.g., non-enhancing lesions in PML) and are less likely to cause multiple ring-enhancing lesions.
- Though HIV can cause **HIV encephalopathy**, it typically involves **diffuse atrophy** and **white matter changes**, rather than distinct ring-enhancing lesions.
*Neoplasm*
- **Primary central nervous system lymphoma (PCNSL)** can present with ring-enhancing lesions, especially in HIV-positive individuals.
- However, given the association with PJP, **infectious etiologies** like toxoplasmosis are generally more common as the initial diagnosis for multiple ring-enhancing lesions in this patient population.
*Bacteria*
- **Bacterial brain abscesses** can cause ring-enhancing lesions but are less common in disseminated opportunistic infections in HIV/AIDS compared to protozoal or fungal infections.
- They also typically present with a more **acute inflammatory picture** and may be preceded by a source of bacterial infection (e.g., endocarditis, sinusitis) not mentioned here.
*Prion*
- **Prion diseases** (e.g., Creutzfeldt-Jakob disease) cause rapidly progressive dementia and characteristic EEG and MRI findings (e.g., cortical ribboning, basal ganglia hyperintensity) that do not typically include multiple ring-enhancing lesions.
- They are also not associated with the immunocompromised state indicated by PJP.
Echinococci and other tissue helminths US Medical PG Question 9: A 27-year-old dental radiographer presented to a clinic with red lesions on his palate, right lower and mid-upper lip, as well as one of his fingers. These lesions were accompanied by slight pain, and the patient had a low-grade fever 1 week before the appearance of the lesions. The patient touched the affected area repeatedly, which resulted in bleeding. Two days prior to his visit, he observed a small vesicular eruption on his right index finger, which merged with other eruptions and became cloudy on the day of the visit. He has not had similar symptoms previously. He did not report drug usage. A Tzanck smear was prepared from scrapings of the aforementioned lesions by the attending physician, and multinucleated epithelial giant cells were observed microscopically. According to the clinical presentation and histologic finding, which viral infection should be suspected in this case?
- A. Herpes simplex infection (Correct Answer)
- B. Varicella-zoster infection
- C. Measles
- D. Herpangina
- E. Hand-foot-and-mouth disease
Echinococci and other tissue helminths Explanation: ***Herpes simplex infection***
- The presence of **red lesions on the palate, lips, and finger**, along with **vesicular eruptions** that become cloudy and are accompanied by **pain** and a preceding **low-grade fever**, are classic signs of **herpes simplex virus (HSV) infection**.
- The histological finding of **multinucleated epithelial giant cells** on a **Tzanck smear** is highly characteristic of herpes virus infections, including HSV.
*Varicella-zoster infection*
- While **varicella-zoster virus (VZV)** also causes vesicular lesions and produces multinucleated giant cells, it typically presents with a **widespread rash** (chickenpox) or a **dermatomal distribution** (shingles), which is not described here.
- The patient's initial symptoms are more consistent with **primary herpes simplex infection**, particularly with the localized presentation.
*Measles*
- **Measles** presents with a characteristic **maculopapular rash** that starts on the face and spreads downwards, often preceded by **Koplik spots** in the mouth, and significant **catarrhal symptoms** (cough, coryza, conjunctivitis).
- It does not typically involve vesicular lesions or the presence of multinucleated giant cells on a Tzanck smear.
*Herpangina*
- **Herpangina** is characterized by painful **vesicles and ulcers localized to the posterior oropharynx** (soft palate, tonsillar pillars, uvula), typically caused by Coxsackieviruses.
- It does not usually affect the lips or fingers, and a Tzanck smear would not show multinucleated giant cells.
*Hand-foot-and-mouth disease*
- **Hand-foot-and-mouth disease (HFMD)** is caused by coxsackieviruses and presents with **vesicular lesions** on the **hands, feet, and oral cavity**, particularly the tongue and buccal mucosa.
- While oral lesions are present, the specific involvement of the palate and the characteristic Tzanck smear findings point away from HFMD.
Echinococci and other tissue helminths US Medical PG Question 10: A 29-year-old internal medicine resident presents to the emergency department with complaints of fevers, diarrhea, abdominal pain, and skin rash for 2 days. He feels fatigued and has lost his appetite. On further questioning, he says that he returned from his missionary trip to Brazil last week. He is excited as he talks about his trip. Besides a worthy clinical experience, he also enjoyed local outdoor activities, like swimming and rafting. His past medical history is insignificant. The blood pressure is 120/70 mm Hg, the pulse is 100/min, and the temperature is 38.3°C (100.9°F). On examination, there is a rash on the legs. The rest of the examination is normal. Which of the following organisms is most likely responsible for this patient’s condition?
- A. Schistosoma mansoni (Correct Answer)
- B. Schistosoma haematobium
- C. Vibrio cholerae
- D. Onchocerca volvulus
- E. Schistosoma japonicum
Echinococci and other tissue helminths Explanation: ***Schistosoma mansoni***
- The patient's symptoms (fevers, diarrhea, abdominal pain, rash, fatigue) after swimming and rafting in Brazil are classic for **acute schistosomiasis (Katayama fever)**, and *Schistosoma mansoni* is endemic to South America, including Brazil, affecting the **gastrointestinal tract**.
- The rash on the legs is consistent with the entry points of **cercariae** through the skin, and the systemic symptoms develop as the adult worms mature and lay eggs.
*Schistosoma haematobium*
- This species primarily causes **urinary schistosomiasis**, with symptoms like **hematuria**, dysuria, and bladder wall calcification.
- It is prevalent in Africa and the Middle East, not typically associated with Brazil.
*Vibrio cholerae*
- *Vibrio cholerae* causes severe, watery **diarrhea** (rice-water stools) and rapid **dehydration**, usually without a prominent rash or prolonged systemic symptoms like fatigue and fever as the primary presentation.
- While diarrhea is present, the array of other symptoms and the exposure history do not align with cholera.
*Onchocerca volvulus*
- This parasite causes **onchocerciasis (river blindness)**, transmitted by blackflies, and primarily manifests as **dermatitis**, subcutaneous nodules, and significant eye disease leading to blindness.
- It does not typically cause acute febrile illness with prominent gastrointestinal symptoms like those described.
*Schistosoma japonicum*
- *Schistosoma japonicum* is found in East Asia (e.g., China, Philippines), not South America, and primarily affects the **gastrointestinal tract** and liver, similar to *S. mansoni*.
- The geographical exposure to Brazil makes *S. mansoni* the most likely cause, despite similar clinical features to *S. japonicum*.
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