SCHISTOSOMIASIS Flashcards
- Caused by five species of the parasitic genus Schistosoma
- Contracted through contact with freshwater bodies harboring infected intermediate-hots snails
Human Schistosomiasis
Only stage of the parasites’ life cycle that can be detected in humans
Schistosome egg
Location:
- S. hematobium
- S. mansoni
- S. japonicum
S. hematobium — terminal spine
* 5S. mansoni — lateral spine
S. japonicum — small lateral spine or knob
MODE OF TRANSMISSION OF SCHISTOSOMA
Penetration of the skin
- Cercarial penetration of the skin may result in a maculopapular rash
- Develop in people who have not previously been exposed to schistosomiasis
- Rare among people living in endemic areas
- The rash may last for 1-2 weeks
- Requires no treatment
Cercarial Dermatitis (Swimmer’s Itch)
- Symptomatic acute schistosomiasis
- Travelers who have contracted the infection for the first time
- Onset occurs between 2 weeks and 3 months after exposure to the parasite
- Many patients recover spontaneously after 2- 10 weeks
- Illness may follow a mor severe clinical course in some individuals with:
+ Weight loss
+ Hepatomegaly
+ Dyspnea
+ Diarrhea
In rare cases, be fatal
Acute Schistosomiasis (Katayama Fever)
- Adult worms are located in the mesenteric veins
- Disease manifestations are associated with parasite eggs
passing through or becoming trapped in intestinal tissue - This induces mucosal granulomatous inflammation with
microulcerations, superficial bleeding, and sometimes
pseudopolyposis - Symptoms tend to be more pronounced with a high
intensity of infection and include:
+ Intermittent abdominal pain
+ Loss of appetite
+ Bloody diarrhea
Intestinal Schistosomiasis (S. mansoni, S. japonicum, S. mekongi)
- Caused by schistosome eggs trapped in liver tissue
- Occurs in S. mansoni and S. japonicum infections
- 2 distinct clinical entities
+ Early inflammatory
+ hepatosplenomegaly
+ Late hepatosplenic disease with periportal fibrosis
Hepatosplenic Schistosomiasis
- Main entity seen in children an adolescents
- Liver is enlarged, especially the left lobe, and is smooth and firm
- Spleen is enlarged, often extending below the umbilicus, and is firm and hard
- Ultrasonography shows no hepatic fibrosis
- Found in up to 80% of infected children
- Severity is closely associated with the intensity of infection
- May be associated with concomitant chronic exposure to malaria
Early Inflammatory Hepatosplenic Schistosomiasis
- Young and middle aged adults with long standing, high-level exposure to infection
- Patients with periportal fibrosis may excrete very few or no eggs in feces
- Ultrasonography reveals typical periportal fibrosis and dilation of the portal vein
Late Hepatosplenic Schistosomiasis with Periportal or Symmers fibrosis
- Signs and symptoms relate to the worms’ predilection for the veins of the urogenital tract
- Characteristic sign in the active stage: painless hematuria
- Dysuria and suprapubic discomfort or pain are associated with active urogenital schistosomiasis
- Associated with Squamous cell carcinoma of the urinary bladder
Urogenital Schistosomiasis (S. haematobium)
- Indicative of active infection
- Standard diagnostic method
Detection of schistosome eggs in stool or urine
Occasionally in Pap smears and semen samples diagnostic
Rectal biopsies (both S. mansoni and S haematobium)
More sensitive than parasitologic methods
PCR based detection of parasite DNA in stool or urine
Detection of specific antibodies
Serology
