Schistosoma Species (Blood Fluke) Test

Schistosoma species are parasitic worms known as blood flukes. They live within the veins that drain the intestines or bladder. The three species that most commonly cause intestinal disease are Schistosoma mansoni, Schistosoma japonicum, and Schistosoma mekongi. Infection occurs when larvae in contaminated freshwater penetrate the skin, enter the bloodstream, and mature into adult worms. These adults settle in the venous system around the intestines, where they mate and release eggs.

While adult worms cause little direct harm, the eggs are what drive nearly all the pathology. Many eggs successfully pass into the stool to continue the parasite’s life cycle, but a significant proportion become trapped in the intestinal wall or liver. When this happens, the immune system forms granulomas, which are clusters of immune cells surrounding foreign material. This chronic granulomatous inflammation creates the hallmark symptoms of intestinal schistosomiasis.

In the gut, these immune reactions can lead to abdominal pain, diarrhea, rectal bleeding, and anemia from chronic blood loss. Over time, repeated inflammation can cause polyps, strictures, or scarring. Some patients develop symptoms that resemble inflammatory bowel disease. In areas where S. japonicum is endemic, prolonged inflammation may slightly increase the risk of colorectal cancer.

Eggs also travel to the liver through the portal vein. When they lodge there, they trigger fibrosis, which is a form of scarring. Over time, this can lead to portal hypertension, which is increased pressure in the portal venous system. Portal hypertension can cause spleen enlargement, low platelet counts, fluid buildup, and even life-threatening bleeding from dilated veins in the esophagus or stomach.

Schistosoma infection also interacts closely with the gut microbiome. Egg-induced inflammation alters the gut environment, which can shift bacterial diversity and metabolic activity. Some bacterial populations may worsen inflammation, while others appear protective. Understanding this dynamic may eventually help identify individuals at higher risk for severe disease or guide microbiome-based therapies.