Potential contributors to anemia in a patient with Fasciola hepatica:
(1) iron deficiency from chronic blood loss (from hemophagia by the parasite, from biliary and gastrointestinal bleeding)
(2) release from the parasite of a substance toxic to erythropoiesis (possible proline, possible soluble antigen)
(3) hemolysis secondary to immune complex vasculitis
(4) anemia of chronic disease secondary to chronic Fasciola infection and/or to secondary bacterial infections of the biliary tract and/or other parasites and/or elevated serum cytokines
(5) splenic sequestration
(6) malnutrition with or without anorexia
According to Valero et al (page 40) the estimated blood loss per adult fluke is 0.2 to 0.5 mL.
Risk factors for anemia:
(1) longstanding infection with Fasciola hepatica
(2) heavy worm burden with Fasciola hepatica (based on imaging studies or egg load in the stool)
(3) pre-existing malnutrition
(4) poor dietary intake of iron, protein and vitamins
(5) immune complex vasculitis
