Trematodes (parasitic animal organisms) or flukes (trematode worms) cause distomiasis.

Trematode infections in humans usually are secondary to those that reproduce sexually and produce eggs in the host. The trematodes that infect humans are most often found in the intestines, biliary tract, lungs, and small veins of the intestines or genitourinary (GU) tract. Intestinal schistosomiasis, (the state of being infected with flukes of the genus Schistosoma), whose major species reside in the intestine and manifest most in the liver, can easily be associated with the major factors surrounding other trematode infections. The different species of the schistosome are found in parts of South America; Caribbean Islands; Africa; the Middle and Far East; China, along the Mekong River in Indochina; and certain areas of West Africa. Infected water is the source for human infections. After entrance into the body, the schistosomes move through the body to different sites, depending on the type of organism, and deposit their eggs. These eggs may remain in these tissues or get swept back to the liver.

Immediately after exposure to the schistosome organism, the person may be asymptomatic, or may have a manifestation, e.g., episodes of itching. After 2 to 6 weeks, the person may experience moderate symptoms including fever; chills; headache; hives or angioedema; weakness; weight loss; nonproductive cough; abdominal pain; and diarrhea. These symptoms may cease, but return with greater intensity when egg-laying begins, and may last 2 to 3 months. More severe symptoms may occur depending on the extent of the infection. However, light infections may still cause severe illness, e.g., central nervous system (CNS) lesions.

The presence of eosinophils are suggestive of acute infection as well as other clinical findings, e.g., leukocytosis, increased levels of immune complexes, and the detection of antibodies.

Chemotherapy has been used to relieve symptoms and glucocorticoids may be useful. However, there has been no documented clinical evidence of their usefulness.

The most significant complication of intestinal schistome infection is hepatic fibrosis and portal hypertension. These complications can occur 10 to 15 years after exposure and infection. In addition, glomerulonephritis and pulmonary hypertension may occur in patients who develop periportal (around the portal vein and its branches) fibrosis.

• None.

• Ratings under diagnostic codes 7301 to 7329, inclusive, 7331, 7342, and 7345 to 7348 inclusive will not be combined with each other. A single evaluation will be assigned under the diagnostic code which reflects the predominant disability picture, with elevation to the next higher evaluation where the severity of the overall disability warrants such elevation.[38 CR 4.114]

• There are diseases of the digestive system, particularly within the abdomen, which, while differing in the site of pathology, produce a common disability picture characterized in the main by varying degrees of abdominal distress or pain, anemia and disturbances in nutrition. Consequently, certain coexisting diseases in this area, as indicated in the instruction under the title “Diseases of the Digestive System,” do not lend themselves to distinct and separate disability evaluations without violating the fundamental principle relating to pyramiding as outlined in 38 CFR 4.14.  [38 CFR 4.113]