Schistosomiasis Flashcards
What are the species of Schistosoma that cause schistosomiasis?
S. mansoni (intestinal disease)
S. japonicum (intestinal disease)
S. mekongi (intestinal disease)
S. intercalatum (intestinal disease)
S. guineensis (intestinal disease)
S. haematobium (urogenital disease)
What is the infective stage of Schistosoma and how does it infect humans?
Cercariae (infective larval stage) released from snails
What happens after cercariae penetrate human skin?
- Transform to schistosomula
- Enter small vein or lymphatic vessel
- Circulate in bloodstream, pass through lung capillaries, and pumped via heart to all parts of body to reach the portal vein
What is the prepatent period of Schistosoma?
- Interval from cercarial penetration to sexual maturation and egg production
- Lasts 5–7 weeks (up to 12 weeks for S. haematobium)
How are Schistosoma eggs excreted?
- Female worm produces eggs
- Excreted via feces or urine (for S. haematobium)
What happens when excreted Schistosoma eggs reach water?
- Eggs hatch, releasing miracidium (free-swimming larval stage)
- Miracidium penetrates host snail, undergoes asexual multiplication
In what form can schistosome parasites be detected in humans?
As eggs in excreta or tissue biopsies
- About 140 mm long
- With a terminal spine
S. Haematobium
- About 150 mm long
- With a lateral spine
S. mansoni
- Smaller, rounder, about 90 mm long
- With a small lateral spine or knob
S. Japonicum
What is the lifespan of an adult schistosome?
- Averages 3–5 years, can be as long as 30 years.
Who are the most important definitive hosts for S. mansoni, S. haematobium, S. intercalatum, and S. guineensis?
- Humans
Which Schistosoma species are zoonotic, and what are their hosts?
- S. japonicum and S. mekongi
- Hosts include pigs, water buffaloes, and various rodents.
How does schistosomiasis infection vary with age?
- Convex age–prevalence curve: low in very young children, peaks at 10–15 years, declines in adults.
This happens around the time when oviposition commences. Antigen excess from eggs leads to formation of soluble immune complexes, depositing in tissues, causing serum sickness–like illness.
Acute Schistosomiasis (Katayama Fever)
Eggs/worms induce the organ-specific morbidity
Eggs
A maculopapular rash resulting from cercarial penetration of the skin
Cercarial Dermatitis (“Swimmer’s Itch”)
Who is more likely to develop Cercarial Dermatitis?
People who have not been previously exposed to schistosomiasis, such as travelers.
What treatments are available for Cercarial Dermatitis?
- Normally requires no treatment.
- Systemic antihistamines, topical antihistamines, or glucocorticoids can be used to reduce symptoms.
When does the onset of Katayama Fever typically occur?
2 weeks and 3 months after exposure to the parasite
A symptomatic form of acute schistosomiasis, usually seen in travelers contracting the infection for the first time
Katayama fever
What is the course and duration of the illness?
Many patients recover spontaneously after 2–10 weeks.
In intestinal schistosomiasis, disease manifestations are associated with parasite eggs passing through or becoming trapped in intestinal tissue. T/F
T
What causes hepatosplenic schistosomiasis?
- Caused by schistosome eggs trapped in liver tissue
- S. mansoni and S. japonicum infections
The most severe complication of hepatosplenic schistosomiasis
Hematemesis
(Schistosomiasis) Develops in young and middle-aged adults with long-term, high-level infection exposure.
Late hepatosplenic schistosomiasis with periportal or symmers fibrosis
Ascites, attributable both to portal hypertension and to hypoalbuminemia, may be seen, especially in ___ infection.
S. japonicum
What type of cancer is associated with chronic S. haematobium infection?
Squamous cell carcinoma of the urinary bladder
How is S. haematobium classified in terms of carcinogenic risk?
- Classified as definitely carcinogenic to humans (group 1 carcinogen) by the International Agency for Research on Cancer (IARC).
There is an association between female genital schistosomiasis and HIV infection T/F
True
A characteristic sign in the active stage of urogenital schistosomiasis
Painless, terminal hematuria
What causes urogenital schistosomiasis?
S. haematobium
What are the stages of S. haematobium infection?
Active stage
Chronic stage
one of the most severe clinical forms of schistosomiasis and is caused by the inflammatory response around eggs in the cerebral or spinal venous plexus
Neuroschistosomiasis
What schistosoma can end up in the spinal venous plexus, where they may cause transverse myelitis
S. Mansoni
S. Haematobium
What schistosoma is mainly associated with granulomatous lesions in the brain, causing epileptic seizures, encephalopathy with headache, visual impairment, motor deficit, and ataxia
S. japonicum
What is the standard diagnostic method for schistosomiasis and is indicative of active infection
Detection of schistosome eggs in stool or urine
Eggs can also be detected in rectal biopsies
S. mansoni and S. haematobium
Eggs can be detected in Pap smears and semen samples
S. haematobium
The drug of choice for treatment of schistosomiasis
Praziquantel
Is praziquantel effective against all schistosome species infecting humans. T/F
T
What are the standard regimens for praziquantel treatment?
What are the standard regimens for praziquantel treatment?
What should you do with patients who are not cured by initial treatment
The same dose can be repeated at weekly intervals for 2 weeks
What is the treatment for cerebral S. japonicum infections?
Praziquantel
When may it be necessary to repeat praziquantel treatment?
May need to repeat dose 6–12 weeks later, especially if eosinophilia or symptoms persist, as it does not affect young migrating stages of schistosomes.
How is schistosomiasis contracted?
Through direct contact with infested freshwater
A cornerstone of the management and control of schistosomiasis.
Praziquantel treatment of infected people, often during mass drug-administration programs
What is the characteristic sign of chronic urogenital schistosomiasis?
A) Painless terminal hematuria
B) Nocturia and urine retention
C) Severe abdominal pain
D) Persistent cough
B
Which species of Schistosoma is a zoonotic parasite requiring control measures for both humans and animals?
A) S. mansoni
B) S. haematobium
C) S. japonicum
D) S. mekongi
C
What preventive measure is recommended for travelers to schistosomiasis-endemic areas?
A) Vaccination
B) Avoiding direct contact with freshwater
C) Wearing mosquito repellent
D) Taking prophylactic antibiotics
B
What preventive measure is recommended for travelers to schistosomiasis-endemic areas?
A) Vaccination
B) Avoiding direct contact with freshwater
C) Wearing mosquito repellent
D) Taking prophylactic antibiotics
B
For which schistosomiasis condition is glucocorticoid treatment recommended in addition to praziquantel?
A) Acute schistosomiasis/Katayama fever
B) Chronic hepatosplenic schistosomiasis
C) Urogenital schistosomiasis
D) Intestinal schistosomiasis
A
A 35-year-old male patient is diagnosed with intestinal schistosomiasis. He is treated with praziquantel but continues to have symptoms six weeks later. Which of the following is the most appropriate next step in management?
A) Reassure the patient and wait for spontaneous resolution
B) Repeat praziquantel treatment after 6–12 weeks
C) Prescribe corticosteroids
D) Perform a liver biopsy
B
A 28-year-old woman recently returned from a trip to Southeast Asia and presents with seizures and visual disturbances. Brain MRI shows granulomatous lesions. Which Schistosoma species is most commonly associated with cerebral involvement?
A) Schistosoma mansoni
B) Schistosoma haematobium
C) Schistosoma japonicum
D) Schistosoma intercalatum
C
A 10-year-old boy living in a rural area endemic for schistosomiasis presents with painless terminal hematuria. Urinalysis confirms the presence of schistosome eggs. Which Schistosoma species is most likely responsible for this presentation?
A) Schistosoma japonicum
B) Schistosoma mansoni
C) Schistosoma mekongi
D) Schistosoma haematobium
D
