Schistosomiasis

Epidemiology

  • Most common cause of cor pulmonale in endemic areas (although not a common cause in USA)
  • Schistosoma mansoni is most common species causing cardiopulmonary schistosomiasis
  • Common etiology of pulmonary HTN worldwide

Endemic Areas

  • S. Mansoni: Arabia/ Africa/ South America/ Caribbean
  • S. Japonicum: China/ Japan/ Philippines
  • S. Haematobium: Africa/ Middle East

Etiology

  • Schistosoma Mansoni
  • Schistosoma Japonicum
  • Schistosoma Haematobium
  • Schistosoma Intercalatum (less common in man)
  • Schistosoma Mekongi (less common in man)

Physiology

  • 3 mechanisms of pulmonary HTN:
    • Anatomic obstruction of pulmonary arteries by organism itself:
    • Inflammatory pulmonary vasculitis due to organism: granulomatous reaction
    • Development of portopulmonary HTN:

Pathogenesis: pulmonary HTN due to anatomic obstruction by eggs/ intense granulomatous response to eggs
-Transmission: intermediate snail host release cercariae into fresh water: cercariae enter human through skin and transform into schistosomulae (which migrate through lungs and liver and develop into mature fluke in venous plexuses)
-Focus of infection: S. Mansoni reside in inferior mesenteric vein/ S. Japonicum reside in superior mesenteric plexus/ S. Haematobium reside in the vesical plexus
-S. Mansoni/ S. Japonicum: flukes release eggs into intestinal circulation, which lodge in portal veins (late in course, eggs travel via porto-systemic collaterals to pulmonary circulation)
-S. Haematobium: flukes release eggs into circulation, which lodge in urinary bladder
-Stool/ urine of infected persons transmits eggs back to soil, which hatch into miracidia (which invade the snail, intermediate host)


Diagnosis

  • Stool/urine schistosomal ova: positive

Acute worm migration:
-Katayama fever: transient pulmonary infiltrates/ leuko-cytosis (with eosinophilia)/ elevated immune complexes

Chronic infection:
-S. Mansoni/ S. Japonicum:
-Liver biopsy with characteristic pre-sinusoidal fibrosis (“Symmer’s pipestem fibrosis”): may aid in diagnosis of pulmonary HTN
-Hypoxemia (occurs late/ may occur early in cases with micro-scopic pulmonary A-V fistulae)
-PFT abnormalities: decreased DLCO/ obstruction/ decreased lung volumes
-CXR abnormalities: basilar or mid-zone infiltrates/ miliary infiltrates/ evidence of pulmonary HTN/ isolated granulomas (occasional)
-Stool O+P: demonstrates eggs (Kato thick smear: quantitative exam of stool)
-Urine O+P: eggs may be filtered out with a microfilter
-Rectal Bx: demonstrates eggs
-Sputum O+P: may rarely demonstrate eggs


Clinical

  • Pulmonary Hypertension (see Pulmonary Hypertension, [[Pulmonary Hypertension]])
    • Pulmonary HTN in schistosomiasis can have similar presentation and histologic plexiform lesions to [[Idiopathic Pulmonary Arterial Hypertension]]
    • Mechanism: probably involves portopulmonary HTN and local vascular inflammation due to impacted schistosoma eggs (mechanical obstruction by schistosoma eggs probably plays a minor role)
    • Estimated that >200 million people are infected worldwide and that 4-8% of patients develop hepatosplenic schistosomiasis
    • With hepatosplenic schistosomiasis: pulmonary HTN is present in 4.6% of cases and post-capillary HTN is present in 3% of cases
  • Hepatic Fibrosis:

Skin penetration:
-“Swimmer’s itch”: local transient dermatitis

Katayama fever (syndrome due to acute worm migration, probably due to reaction to invading schistosome rather than to eggs/ usually associated with heavy primary infection: mainly with S. Japonicum, rarely with S. Haematobium)
-Systemic: fever/ chills/ headache/ myalgias/ arthralgias
-GI: weight loss/ abdominal pain/ diarrhea/ hepatosplen-omegaly and lymphadenopathy (occur in 20-30% of cases)
-Pulmonary: dry cough/ wheezing
-Neurologic: transverse myelitis

Chronic infection:
-S. Mansoni/ S. Japonicum: fatigue/ intermittent diarrhea/ abdominal pain/ portal HTN (with relatively spared hepatic synthetic function)/ pulmonary HTN (dyspnea/ precordial chest pain)/ cyanosis, clubbing (may occur in cases with pulmonary A-V fistulae within granulomas or due to portopulmonary shunting)
-25% of patients with hepatic involvement have some evidence of pulmonary involvement (but <5% have Cor Pulmonale): hepatic involvement always precedes pulmonary involvement
-S. Haematobium: bladder and urinary tract involvement/ pulmonary HTN (may occur due to embolization of eggs via IVC)


Treatment

  • Praziquantel: effective
    • Minimal toxicity
    • However, cardiopulmonary changes are not usually reversible due to degree of fibrotic changes that have already occurred

Praziquantel
-S. Mansoni/ S. Haematobium: 20 mg/kg BID X 1 day (alternate foro S. Haema-tobium: Metri-fonate/ alter-nate for S. Mansoni: Oxamiquine)
-S. Japonicum: 20 mg/kg TID X 1 day
-efficacy for treatment of Katayama fever is not known
-efficacy of treatment to re-verse hepatic/ pulmonary dis-ease in adults has not been shown (only proven in children)
-may precipitate an acute self-limited pulmonary reaction (due to released antigens from worms): cough/ wheezing/ eosinophilia/ new pulmonary infiltrates


References

  • Lapa MS, Ferreira EV, Jardim C, Martins Bdo C, Arakaki JS, Souza R. [Clinical characteristics of pulmonary hypertension patients in two reference centers in the city of Sao Paulo]. Rev Assoc Med Bras 2006;52:139-43
  • Chaves E. The pathology of the arterial pulmonary vasculature in Manson’s schistosomiasis. Chest 1966;50:72-7
  • de Cleva R, Herman P, Pugliese V, et al. Prevalence of pulmonary hypertension in patients with hepatosplenic Mansonic schistosomiasis-prospective study. Hepatogastroenterology 2003;50:2028-30
  • Lapa M, Dias B, Jardim C, et al. Cardiopulmonary manifestations of hepatosplenic schistosomiasis. Circulation 2009;119:1518-23