Читать книгу Sierra South. Backcountry Trips in California's Sierra Nevada онлайн

17 страница из 140

Giardia and Cryptosporidium: Giardiasis is a serious gastrointestinal disease caused by a waterborne protozoan, Giardia lamblia. Any mammal (including humans) can become infected. It will then excrete live giardia in its feces, from which the protozoan can get into even the most remote sources of water, such as a stream issuing from a glacier. Giardia can survive in snow through the winter and in cold water as a cyst resistant to the usual chemical treatments. Giardiasis can be contracted by drinking untreated water. Symptoms appear two to three weeks after exposure.

Cryptosporidium is another, smaller, very hardy pest that causes a disease similar to giardiasis. It’s been found in the streams of the San Gabriel Mountains of Los Angeles, and it is spreading throughout Southern California. Probably it will eventually infest Sierra waters.

At this time, boiling and filtering are the only sure backcountry defenses against giardia and cryptosporidium. Bring water to a rolling boil; this is easy to do while you’re cooking and is now judged effective at any Sierra altitude. To be effective against both giardia and the much-smaller cryptosporidium, a filter must trap particles down to 0.4 micron.