INFECTIONS - Medicine for Mountaineering and Other Wilderness Activities - page 320

etrating through intact skin, a step that requires about thirty minutes. After two days, the
organisms spread through the bloodstream to the lungs and liver. A month later, the worms
mature and migrate through veins to their final dwelling place in the intestines or urinary
bladder. Adult worms live five to ten years.
The clinical manifestations of schistosomiasis occur in stages and are produced by the
effects of the organism. Skin penetration by the cercariae usually is not associated with
any reaction, but repeated exposure may lead to a red rash that is called swimmer's itch or
schistosome dermatitis where such infestations occur.
Sometimes, with particularly heavy infestations, fever, chills, headache, and a cough
occur when adult worms form and eggs are first produced. Such episodes are known as
Katayama fever or acute schistosomiasis. The liver, spleen, and lymph nodes are enlarged,
and eosinophilia is present.
The chronic effects of infestation are produced when the body responds to the eggs. S.
mansoni and S. japonicum adults live in the intestines and release their eggs into blood
that goes to the liver. Scarring occurs around the eggs, producing obstruction to liver
blood flow. First the liver and then the spleen become enlarged. In late stages catastrophic
gastrointestinal bleeding and liver failure may occur.
Different complications are associated with infestation by S. haematobium because the
adultsliveintheveinsaroundtheurinarybladderinsteadofintheintestines.Scarringfrom
the eggs of these organisms produces obstruction of the bladder and ureters. Blood in the
urine and painful urination are the usual symptoms. Eventually, the chronic irritation asso-
ciated with the infestation can lead to malignant changes. Squamous cell carcinoma of the
urinary bladder is rare in most of the world but is one of the most common malignancies in
areas where schistosomiasis is endemic.
Thethreemain Schistosoma speciesarefoundinfreshwaterlakesandriversworldwide.
Infectionscausedby S. mansoni arefoundthroughoutallofAfrica,Arabia,SouthAmerica
(Brazil,Venezuela,andSurinam)andtheCaribbean. S. japonicum occursinSoutheastAsia
and the Philippines, whereas S. haematobium occurs in Africa and the Middle East.
The diagnosis of schistosomiasis is made by finding the characteristic eggs in the stool
orurineofindividualswithanyoftheclinicalmanifestationsofinfection,suchasdermatit-
is, Katayama fever, or liver disease. A blood test is available through the CDC.
Safe and effective oral drugs have recently been introduced for the treatment of schisto-
somiasis. The most broadly effective is praziquantel (Biltricide®) in differing dosages for
S. mansoni , S. haematobium , and S. japonicum . Treatment should be undertaken only by a
physician. The drugs kill the organisms but do not eliminate them from the body, and they
produce inflammatory reactions similar to—although considerably less severe than—those
produced by living eggs.
Avoiding infestation is far more satisfactory. Infestation can be avoided only by staying
completely out of stagnant or slowly moving water in areas where the parasites are found.