1. A 54-year-old man (J.M.) who immigrated from rural Southeast Asia two decades ago is about to begin high-dose prednisone plus a biologic agent for newly diagnosed giant cell arteritis. Routine labs show a peripheral eosinophil count of 1,200 cells/microliter. He is asymptomatic from a gastrointestinal standpoint. What is the most appropriate next step before initiating immunosuppression?
A) Proceed with immunosuppression now and investigate the eosinophilia only if he later develops symptoms
B) Treat empirically with mebendazole, the definitive agent for the most dangerous occult helminth in this setting
C) Treat empirically with praziquantel before steroids, since the most dangerous occult helminth here is a fluke
D) Test for Strongyloides stercoralis and treat with ivermectin before starting corticosteroids, because immunosuppression can convert latent strongyloidiasis into a frequently fatal hyperinfection syndrome
E) Begin diethylcarbamazine empirically, since it is the standard agent for occult tissue nematodes before immunosuppression
ANSWER: D
Rationale:
In a patient from an endemic region with unexplained eosinophilia, the dominant safety concern before immunosuppression is latent Strongyloides stercoralis, because corticosteroids and other immunosuppression can precipitate a frequently fatal hyperinfection syndrome. The correct step is to test for Strongyloides and treat with ivermectin, the first-line agent, before starting steroids.
Option A: Option A is incorrect; waiting for symptoms risks fatal hyperinfection.
Option B: Option B is incorrect; benzimidazole efficacy against Strongyloides is inferior, so mebendazole is not the definitive agent.
Option C: Option C is incorrect; the dangerous occult parasite here is the nematode Strongyloides, not a fluke, and praziquantel does not treat it.
Option E: Option E is incorrect; diethylcarbamazine is a filarial agent and is not the agent for occult strongyloidiasis before immunosuppression.
2. A 30-year-old woman (A.K.) from a rural region of Cameroon presents with lymphatic filariasis. Before treatment, a daytime blood smear reveals a very high Loa loa microfilarial density of approximately 40,000 microfilariae/milliliter. The team is preparing to give a microfilaricidal agent. Which consideration must most urgently shape management?
A) Proceed immediately with standard-dose diethylcarbamazine, since a high Loa loa burden poses no special hazard
B) A very high Loa loa microfilarial density markedly raises the risk of severe, potentially fatal encephalopathy from rapid microfilarial death with diethylcarbamazine or ivermectin, so the high burden must drive a modified, risk-mitigating approach rather than routine dosing
C) Give a single standard dose of ivermectin without burden-based modification, since ivermectin carries no encephalopathy risk in loiasis
D) Withhold all antifilarial therapy permanently, since loiasis is untreatable at any microfilarial density
E) Treat with praziquantel, the agent of choice for high-burden loiasis
ANSWER: B
Rationale:
At very high Loa loa microfilarial densities, both diethylcarbamazine and ivermectin can precipitate a severe, potentially fatal encephalopathy as enormous numbers of microfilariae die rapidly within central nervous system vessels. The high measured burden must therefore drive a modified, risk-mitigating strategy rather than routine dosing.
Option A: Option A is incorrect; a high Loa loa burden is precisely the hazard that demands caution.
Option C: Option C is incorrect; ivermectin also carries encephalopathy risk at high Loa loa burdens and cannot be given without burden-based modification.
Option D: Option D is incorrect; loiasis is treatable, and the issue is safe execution at high burden, not permanent withholding.
Option E: Option E is incorrect; praziquantel is a fluke and tapeworm agent and is not used for loiasis.
3. A 41-year-old man (R.S.) from a region where Taenia solium is endemic presents with new-onset seizures. MRI shows several viable parenchymal cysts, some with a visible scolex and surrounding enhancement. The neurology team plans antiparasitic therapy. Which regimen is most appropriate?
A) Albendazole as the antiparasitic backbone, given together with a corticosteroid to control the inflammatory response to dying cysts, with an antiepileptic for seizure control
B) Praziquantel monotherapy without any corticosteroid, to preserve praziquantel cerebrospinal fluid levels
C) No antiparasitic therapy, because viable parenchymal cysts never benefit from treatment
D) Diethylcarbamazine plus a corticosteroid, since diethylcarbamazine penetrates the central nervous system best
E) Triclabendazole plus a corticosteroid, because tissue cestodes respond preferentially to triclabendazole
ANSWER: A
Rationale:
Viable parenchymal neurocysticercosis cysts benefit from antiparasitic therapy, and killing them incites inflammation that mandates a concurrent corticosteroid; an antiepileptic addresses the seizures. Albendazole is the preferred antiparasitic backbone because its central nervous system penetration is preserved despite the corticosteroid, whereas the steroid lowers praziquantel cerebrospinal fluid levels.
Option B: Option B is incorrect; omitting the corticosteroid while killing viable cysts is unsafe, and praziquantel alone is the wrong central choice under steroid co-treatment.
Option C: Option C is incorrect; viable cysts do benefit from treatment, unlike calcified-only cysts.
Option D: Option D is incorrect; diethylcarbamazine is a filarial agent with no role in neurocysticercosis.
Option E: Option E is incorrect; triclabendazole is the Fasciola agent and is not used for neurocysticercosis.
4. A 38-year-old woman (L.T.) has a remote history of neurocysticercosis and now presents with a breakthrough seizure. MRI demonstrates only small calcified lesions with no viable cysts, no scolex, and no active enhancement. What is the most appropriate management of the parasitic component?
A) Start a 28-day course of high-dose albendazole to dissolve the calcified lesions
B) Give albendazole plus praziquantel to ensure complete destruction of the calcified cysts
C) Administer praziquantel monotherapy, since calcified cysts respond preferentially to it
D) Begin diethylcarbamazine to penetrate and clear the calcified foci
E) Do not give antiparasitic therapy, because the lesions are calcified and dead and would gain no benefit; manage the seizures with antiepileptic therapy and avoid the needless inflammatory risk of treating dead cysts
ANSWER: E
Rationale:
Calcified neurocysticercosis lesions are dead; antiparasitic drugs act only on living parasites, so treating calcified-only disease offers no benefit while adding the risk of inflammation around the lesions. The correct approach is to withhold antiparasitic therapy and manage the seizures with antiepileptic treatment.
Option A: Option A is incorrect; albendazole cannot dissolve dead calcified lesions and would only add risk.
Option B: Option B is incorrect; combination antiparasitic therapy of dead cysts provides no benefit.
Option C: Option C is incorrect; calcified cysts do not respond to praziquantel or any antiparasitic.
Option D: Option D is incorrect; diethylcarbamazine is a filarial agent with no role here, and dead cysts would not benefit regardless.
5. A 26-year-old traveler (D.P.) returns from swimming in fresh water in Lake Malawi and, weeks later, develops hematuria and is diagnosed with schistosomiasis. He is treated with a single weight-based dose of praziquantel. What additional step most improves his likelihood of cure, and why?
A) Add a continuous 28-day albendazole course, since albendazole is required to eradicate adult schistosomes
B) Substitute triclabendazole, because schistosomes are inherently resistant to praziquantel
C) Schedule a second praziquantel course four to six weeks after the first, because praziquantel is most active against adult worms and weakly active against immature schistosomula; worms still maturing at the first dose survive it and become susceptible by the time of the second
D) Give a single dose of diethylcarbamazine as consolidation, since it kills the schistosome microfilariae the first dose missed
E) No further action is needed because a single praziquantel dose is always fully curative for all schistosome stages
ANSWER: C
Rationale:
Praziquantel is most active against adult worms and only weakly active against immature schistosomula. Worms that were still maturing at the time of the first dose survive it; scheduling a second praziquantel course four to six weeks later catches these worms once they have matured into susceptible adults, raising the cure rate.
Option A: Option A is incorrect; albendazole is not required to eradicate adult schistosomes, and a prolonged course is the regimen for tissue cestode disease.
Option B: Option B is incorrect; schistosomes are susceptible to praziquantel, unlike Fasciola, so triclabendazole is not substituted.
Option D: Option D is incorrect; schistosomiasis management does not rely on diethylcarbamazine, and the issue is immature-worm survival, not microfilariae.
Option E: Option E is incorrect; a single dose is not invariably curative across all stages, which is exactly why the delayed second course helps.
6. A 47-year-old woman (M.V.) from a sheep-farming region presents with right upper quadrant pain, eosinophilia, and imaging showing migratory hepatic tract lesions; serology confirms Fasciola hepatica infection. She was previously given praziquantel elsewhere without improvement. What is the correct treatment and the reason praziquantel failed?
A) Repeat praziquantel at a higher dose, since the prior failure reflects underdosing rather than intrinsic resistance
B) Albendazole as a single dose, because benzimidazoles are the agents of choice for all liver flukes
C) Ivermectin, because Fasciola responds to glutamate-gated chloride channel activation
D) Triclabendazole, because the Fasciola tegument is inherently resistant to praziquantel, so praziquantel failure is expected and triclabendazole is the agent of choice for fascioliasis
E) Diethylcarbamazine, since Fasciola is a tissue-migrating organism best treated with a microfilaricidal agent
ANSWER: D
Rationale:
Fasciola hepatica is the classic trematode exception to praziquantel: its tegument is inherently resistant, so praziquantel failure is expected, and triclabendazole is the established agent of choice for fascioliasis.
Option A: Option A is incorrect; the failure reflects intrinsic resistance, not underdosing, so repeating praziquantel will not work.
Option B: Option B is incorrect; benzimidazoles such as albendazole are not the agents of choice for Fasciola, and not all liver flukes are treated alike.
Option C: Option C is incorrect; Fasciola does not respond to ivermectin's chloride-channel mechanism.
Option E: Option E is incorrect; diethylcarbamazine is a filarial agent and is not used for fascioliasis.
7. A 35-year-old man (T.B.) has a large hepatic hydatid cyst from Echinococcus granulosus and is scheduled for PAIR (puncture-aspiration-injection-reaspiration). The interventional team asks how albendazole should be timed relative to the procedure. What is the correct recommendation?
A) Give albendazole only if the patient develops symptoms after the procedure, since pre-procedure dosing is harmful
B) Start albendazole several days before the procedure and continue it afterward, because protoscoleces spilled during puncture can seed new (secondary) cysts, and perioperative albendazole provides antiparasitic cover that reduces this risk
C) Give a single albendazole dose at the moment of puncture only, with no pre- or post-procedure dosing
D) Avoid albendazole entirely, since the procedure alone is curative and the drug adds no value
E) Replace the procedure with albendazole alone, since medical therapy reliably cures all active hydatid cysts without intervention
ANSWER: B
Rationale:
During puncture of a hydatid cyst, viable protoscoleces can spill and seed new secondary cysts. Starting albendazole several days before the procedure establishes antiparasitic cover in advance, and continuing it afterward reduces the chance that any spilled protoscoleces establish secondary disease.
Option A: Option A is incorrect; pre-procedure dosing is recommended, not harmful, and waiting for symptoms defeats the prophylactic purpose.
Option C: Option C is incorrect; a single dose at puncture without pre- and post-procedure cover does not provide adequate protection against seeding.
Option D: Option D is incorrect; the procedure is not reliably curative without antiparasitic cover, given the seeding risk.
Option E: Option E is incorrect; for active cysts the drug complements rather than replaces the procedure, so albendazole alone is not a reliable cure.
8. A 24-year-old woman (N.O.), 22 weeks pregnant, lives in a high-prevalence region and has a heavy hookworm burden contributing to symptomatic anemia. Which treatment approach is most appropriate?
A) A single dose of a benzimidazole (albendazole or mebendazole), which is used for soil-transmitted helminthiasis from the second trimester onward in high-prevalence settings, since treating a heavy burden is a net benefit in pregnancy
B) Diethylcarbamazine, the preferred antihelminthic during pregnancy
C) Routine ivermectin as the first-line agent for hookworm in any pregnancy
D) Defer all treatment until after delivery, since all antihelminthics are absolutely contraindicated throughout pregnancy
E) Triclabendazole, since it is the safest soil-transmitted nematode agent in pregnancy
ANSWER: A
Rationale:
A heavy hookworm burden with symptomatic anemia is a clear indication to treat in pregnancy, and a single dose of albendazole or mebendazole is used for soil-transmitted helminthiasis from the second trimester onward in high-prevalence settings; at 22 weeks she is in the second trimester.
Option B: Option B is incorrect; diethylcarbamazine is contraindicated in pregnancy and is a filarial agent, not a treatment for hookworm.
Option C: Option C is incorrect; ivermectin has limited pregnancy safety data and is generally avoided except in life-threatening disease, so it is not a routine first-line choice.
Option D: Option D is incorrect; treating a heavy burden from the second trimester is beneficial, so blanket deferral is wrong.
Option E: Option E is incorrect; triclabendazole is the Fasciola agent, not a soil-transmitted nematode treatment.
9. A 7-year-old child (K.W.) has perianal itching worst at night, and pinworm (Enterobius vermicularis) is confirmed. The parent is treated as well. After choosing an appropriate luminal agent such as pyrantel pamoate, what dosing feature is most important to ensure cure, and why?
A) A single dose is always sufficient and no repeat is needed, since pinworm cannot reinfect after one treatment
B) The agent must be given intravenously to reach the worms in the colon
C) Triclabendazole should be substituted, since pinworm is a tissue-invasive helminth requiring systemic therapy
D) Diethylcarbamazine should be added, since enterobiasis is a filarial infection
E) A repeat dose about two weeks after the first is important, because the initial dose does not kill eggs, and newly hatched worms from environmental egg contamination or reinfection emerge after treatment; the repeat dose targets this second generation
ANSWER: E
Rationale:
Enterobiasis is prone to reinfection: the first dose kills existing worms but not eggs, and newly hatched worms from environmental egg contamination or autoinfection emerge afterward. A repeat dose about two weeks later targets this second generation and is important for cure (treating close contacts and hygiene measures also help).
Option A: Option A is incorrect; reinfection and newly hatched worms make a single dose frequently insufficient.
Option B: Option B is incorrect; pyrantel is given orally and acts in the gut lumen, not intravenously.
Option C: Option C is incorrect; pinworm is a luminal, not tissue-invasive, helminth, and triclabendazole is the Fasciola agent.
Option D: Option D is incorrect; enterobiasis is a nematode infection of the gut, not a filarial infection, so diethylcarbamazine has no role.
10. A public-health physician (overseeing patient cohorts in a West African district) is selecting the mass drug administration regimen for lymphatic filariasis. The district is also endemic for onchocerciasis (river blindness). Which regimen is appropriate, and why?
A) Diethylcarbamazine plus albendazole, the standard regimen regardless of onchocerciasis status
B) Praziquantel plus pyrantel, since these cover filarial infection in onchocerciasis-endemic areas
C) Ivermectin plus albendazole, because diethylcarbamazine is hazardous where onchocerciasis is co-endemic (it can provoke a severe Mazzotti reaction from rapid death of Onchocerca microfilariae, including ocular harm), so the diethylcarbamazine-containing regimen is avoided here
D) Triclabendazole plus mebendazole, the preferred filariasis regimen in onchocerciasis-endemic zones
E) Diethylcarbamazine alone, since adding albendazole increases the onchocerciasis-related risk
ANSWER: C
Rationale:
In areas co-endemic for onchocerciasis, diethylcarbamazine can provoke a severe Mazzotti-type reaction from the rapid death of Onchocerca volvulus microfilariae, including the risk of ocular injury; therefore lymphatic filariasis mass drug administration uses ivermectin plus albendazole where onchocerciasis is present, reserving diethylcarbamazine plus albendazole for non-onchocerciasis areas.
Option A: Option A is incorrect; the diethylcarbamazine regimen is precisely what must be avoided in onchocerciasis co-endemicity.
Option B: Option B is incorrect; praziquantel and pyrantel are not the filariasis regimen.
Option D: Option D is incorrect; triclabendazole and mebendazole are not the lymphatic filariasis mass treatment regimen.
Option E: Option E is incorrect; the hazard comes from diethylcarbamazine in onchocerciasis, not from adding albendazole, so diethylcarbamazine alone remains the wrong choice here.
11. A 33-year-old man (G.H.) is mid-course on rifampicin-based therapy for pulmonary tuberculosis when he is also diagnosed with intestinal schistosomiasis and a clinician proposes starting praziquantel concurrently. What is the most appropriate action, and why?
A) Start praziquantel at a reduced dose, because rifampicin inhibits its metabolism and would otherwise cause toxicity
B) Start standard praziquantel without concern, since rifampicin and praziquantel do not interact
C) Increase the rifampicin dose to enhance praziquantel absorption and efficacy
D) Avoid giving praziquantel concurrently with rifampicin and arrange an alternative timing or approach, because rifampicin potently induces CYP3A4 and sharply lowers praziquantel plasma levels, threatening treatment failure
E) Replace praziquantel with diethylcarbamazine, which rifampicin does not affect, for this schistosome infection
ANSWER: D
Rationale:
Rifampicin is a potent CYP3A4 inducer, and praziquantel undergoes extensive CYP3A4-dependent first-pass metabolism; co-administration sharply lowers praziquantel plasma concentrations and risks treatment failure. The appropriate action is to avoid concurrent administration and arrange an alternative timing or approach (for example, completing or adjusting therapy so the two are not given together).
Option A: Option A is incorrect; rifampicin induces rather than inhibits CYP3A4, so praziquantel levels fall, not rise, and a reduced dose worsens the problem.
Option B: Option B is incorrect; the interaction is real and clinically important.
Option C: Option C is incorrect; raising rifampicin would deepen induction and further reduce praziquantel levels, not improve efficacy.
Option E: Option E is incorrect; diethylcarbamazine is a filarial agent and does not treat schistosomiasis, so it is not a valid substitute.
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