INFECTIONS - Medicine for Mountaineering and Other Wilderness Activities - page 321

No swimming, bathing, or even wading should be allowed in infested water. No other ef-
fective preventive measure exists. The snails that form an essential part of the schistosome
life cycle do not live in rapidly moving water, so the schistosomes are not found there.
Significant infestations have occurred among rafters on slow-moving streams that did not
occur during flood season when the water was flowing much faster.
More information is available at www.cdc.gov/ncidod/diseases/submenus/
sub_schistosomiasis.htm .

Onchocerciasis
Onchocerciasis (river blindness) is one of the most common causes of loss of vision in
developing countries. It is caused by a filarial parasite transmitted to humans by the bite
of black flies found near rivers in higher elevations of tropical Africa, Central America,
and South America. Adult worms live in hard, painless nodules under the skin. The adults
release microfilaria that cause intense itching in the skin and irritation of the eye. The dia-
gnosisismadebyexaminingskinbiopsiesorexaminingtheeyefortheorganism.Effective
treatment is now available with ivermectin (Stromectol®).
More

information is available at www.cdc.gov/ncidod/submenus/

sub_river_blindness.htm .

Chagas' Disease
Chagas' disease, or American trypanosomiasis, is found from southern South America
tonorthernMexico.Thecausativeorganism, Trypanosoma cruzi ,istransmittedfrominfec-
tedanimalstohumansbythebiteofseveralkindsofreduviid(kissingorassassin)bugsthat
inhabit the walls and ceilings of poorly constructed houses. After a bite, usually at night,
redness andswelling occurlocally andarefollowed byfever,headache, generalized lymph
node swelling, and enlargement of the liver and spleen. Ten to thirty years later signs of
irreversible damage to the heart, esophagus, or colon appear. Although no clearly effective
form of treatment in the late stages of disease is available, nifurtimox may be useful early.
Preventive measures include insecticide spraying of infested houses. Insecticide-im-
pregnated bed nets may reduce the risk of infection for travelers who cannot avoid camp-
ing, sleeping outdoors, or sleeping in poorly constructed houses in endemic areas.
More information is available at www.cdc.gov/chagas .

Trichinosis
Trichinosis (or trichinellosis) is a parasitic disease caused by eating improperly cooked
meat containing larvae of the roundworm Trichinella spiralis . Infection is common in wild
carnivores and may also be found in domestic pigs. After the larvae are ingested, they at-
tach themselves to the wall of the small bowel, mature, and produce eggs. The larvae re-