Archived posting to the Leica Users Group, 2003/06/11

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Subject: RE: [Leica] Parasites and the so called "third world' - way OT
From: Marty Deveney <sealpup@sharkattacks.com>
Date: Wed, 11 Jun 2003 18:09:41 -0700 (PDT)

Hello all,

>The parasites from animals typically don't develop normally in humans >and, as a result, wander all over wreaking havoc until they die. The >worst may be Lagochilascaris, which I studied in the 1970's. This >takes up residence in the tissues of the neck (usually) and is able to >reproduce there. Horrible death.

There can't be too many non-parasitology lists to which two parasitologists subscribe.

There are other impressively terrible zoonoses (infections normally found in animals that occur in humans). 

When the roundworm (nematode) Angiostrongylus cantonensis, which is normally a parasite of rats, infects humans, the larvae migrate through the nervous tissues of the spine and brain, often causing death after an awful meningo-encephalitis. 

Echinococcus multilocularis causes alveolar echinococcosis in humans, in which the intermediate stage of the tapeworm buds outwards, rather than forming a single cyst that grows in size as does the more common and closely related hydatid E. granulosis.  By the time of diagnosis of alveolar echinococcosis, the tapeworm has sometimes invaded so many tissues that removal is impossible and the infection can be fatal.  Death in these cases occurs in a very similar manner to a slow metastatic cancer.  Fortunately drug treatment is often curative, but of course is dependent on a correct diagnosis.

>Bird schistosomes usually produce the world's worst itching for a >week, but no serious health problems. From wading in salt water. Human >schistosomiasis is from wading in fresh water. It is nasty for the >long term.

Swimmer's itch in Australia is most often contracted in fresh water.  They itch like hell.  Human schistosomes have been shown to have a lifespan of over 30 years.  If you get 'em and don't treat 'em you've almost got a friend for life.

In Africa, surely the best (and Kyle Cassidy's favourite parasite!) thing to avoid is the guinea worm, Dracunculis medinensis, which you get by drinking water contaminated by infected cyclopoid copepods (a tiny crustacean).  The guinea worm grows to a meter or more in length and lives under the skin on your leg.  The head end pokes out a hole the worm makes in your leg and lays eggs into water when your foot is submerged.  The traditional fix is to slowly wind the worm out on a stick.  Lovely.

Warning: some of these links have some pretty gruesome images on them:
http://www.who.int/ctd/dracun/disease.htm
http://www.biosci.ohio-state.edu/~parasite/dracunculus.html

And people wonder why I studied parasites - fascinating!

Marty

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