by Tim Bolen  

Worldwide Issues...

Quoting from the Introduction on the website of the British Society for Parasitology...

Continuous effort by the world community of parasitologists is necessary to understand and further the control of parasites and their vectors.

Modern research is providing this increased understanding using techniques such as molecular biology, immunology, vaccine technology, field studies and mathematical modelling.

Funding of research in parasitology has been maintained by the national Research Councils, international agencies including the World Health Organisation, the World Bank, European Economic Community and major charities such as The Wellcome Trust."

The Society aims to advance the study of parasitology, promote interest and discussion, aid training and education, and disseminate information about recent advances. The B.S.P. furthers these aims through its regular Newsletter to its membership and through the organisation of its meetings."

The WHO (World Health Organization) website is full of information about parasite problems.  As an example, try their write-up on "African Sleeping Sickness."  Then keep in mind that U.S. Citizens are World Travelers.

World travelers are carriers of parasites.

On that note, read this article out of the December, 2000 issue of Time magazine called "For Every Paradise, There's A Parasite."  

The University of Cambridge,
Department of Pathology,
Schistosomiasis Research Group says:

"There are a number of Digenean parasitic trematode (flatworms) capable of causing disease in man. Schistosomiasis (Bilharzia) is the most important of these helminth infections, and is caused by members of the genus Schistosoma. These parasites are important pathogens, estimated to be infecting some 200 million people in tropical and subtropical regions. 

The most important species that infect man are S. japonicum, S. mansoni and S. haematobium. 

Work in our group concentrates on S. mansoni. Infection occurs through contact with fresh water that contains infective cercariae released from an intermediate host snail. The cercaria penetrates intact human skin and transforms into the migrating schistosomulum larva, that migrates through the bloodstream to the hepatic portal system to complete the parasites lifecycle. 

Penetration of the skin by the cercaria (usually from species unable to develop in man, particularly cercaria of species of avian schistosomes) may result in a form of dermatitis, cercarial dermatitis, though this is not as important in terms of pathology as egg induced pathology, (see below). 

Male and female worms differentiate, pair and migrate into the small venules draining the intestine (S. mansoni, S. japonicum ) or the bladder (S. haematobium ). In these sites, and fully exposed to the host immune system, adult worms live for 3 to 8 years, although cases have been reported of individuals still excreting parasite eggs 30 years after leaving a schistosome endemic area. 

The female worm produces 300 to 3000 eggs each day. Eggs pass into the lumen of the intestine or bladder and, if deposited in fresh water, hatch to release ciliated miracidia that infect the snail host.

 However, many eggs also lodge in the definitive host's liver and intestine or bladder, where they cause the pathology associated with schistosomiasis. In the chronic form of the disease, eggs trapped in the liver elicit the development of a cellular, granulomatous reaction which, with its ensuing fibrosis, gives rise to the most serious disease symptoms of infection. 

Hepatosplenic disease associated with S. mansoni infections results from liver portal tract fibrosis. This progressive fibrosis can lead to obstructive vascular lesions, portal hypertension, ascites and fatal bleeding from oesophagogastic varices.

The number of cases of schistosomiasis is increasing world-wide."

The U.S. Center for Disease Control and Prevention has a web page devoted to the health risks assumed by American travelers to foreign countries - It is called "Travelers Health."

Ann Louise Gittleman, in her book "Guess Who Came to Dinner", says that "Parasites are alive and well in the United States."

For an critical analysis of the problems in the United States try Kansas State University's Parasitology website by Stephen Upton PhD. Then try Tucker Crum's website at  Dept. of Biology, Simmons College.

How do we get parasites in our bodies?  Lots of ways.  Read the article entitled "Is Unsafe Drinking Water Really Less Expensive?" by Hans Peterson of the Safe Drinking Water Foundation.

An article by WHO (World Health Organiation), called "Water and Sanitation,"  says that "Every eight seconds a child dies of a water-related disease. Every year more than five million human beings die from illnesses linked to unsafe drinking water, unclean domestic environments and improper excreta disposal."   The article points out that WATER is the single-most carrier of parasites in the world.

Terribly important is our food supply.  In an issue of Agricultural Research magazine, an article called "Crossing the Equator With Science: New Partnership Between Brazil and ARS," says "Internal parasites - worms - are one of the major problems facing the beef and dairy industries in both the United States and Brazil. Worms cost these industries $2 billion a year in the United States alone and have started to build resistance to commercial anthelmintics."

In an issue of Agricultural Research magazine, February 2000, an article called "Zoonoses," says "Zoonoses - animal diseases that are naturally communicable to humans  - have inflicted health problems on millions of people worldwide. But the power of three devastating zoonotic diseases - brucellosis, leptospirosis, and tuberculosis (TB) - may someday be broken up by new knowledge of how they are transmitted from wildlife to domestic animals to humans. Agricultural Research Service researchers at the National Animal Disease Center (NADC) in Ames, Iowa, are gaining this  knowledge."

A recent entry into the United States "Chagas Disease," demonstrates another way to get infected - insect bites.

It is time to wake up to the problem...

If none of the rest of this page got your serious attention - then an article in The Atlantic magazine called "Resurgence of a Deadly Disease." just might.  It says "Malaria kills roughly twice as many people worldwide as AIDS, drugs no longer work against some strains, and mosquitoes in diverse parts of the United States now carry the disease. Why aren't we doing more to fight it?"