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I'm Alan Fenwick.
I'm a professor of
tropical parasitology
in Imperial College, London.
And I'm Director of the
Schistosomiasis Control Initiative,
also in London.
But we work, controlling this
disease, in several countries,
particularly in sub-Saharan Africa.
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So schistosomiasis, which is
also commonly known as bilharzia,
is caused by trematode worms
which inhabit the blood vessels
around the bladder or in the
mesentery of the human hosts.
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Worldwide, there are several
species which infect humans.
But there are three major species.
In sub-Saharan Africa,
there are two major species.
One is Schistosoma
haematobium, which
causes urinary schistosomiasis.
It's only found in Africa, and
there is no animal reservoir.
The second species in Africa is
Schistosoma mansoni, which is also
known as intestinal schistosomiasis.
Not only is it found
in Africa, however,
but it was also exported to South
America, probably with the slaves.
And it's quite possible that
some rodents and primates can
be infected with
Schistosoma mansoni.
The third major species
is Schistosoma japonicum,
which also causes
intestinal schistosomiasis.
And several years ago, it was a
scourge of both Japan and China.
However, it is now very
restricted in its distribution.
It's actually been
eliminated from Japan.
And there are small foci in
China, and in the Philippines.
This parasite is very interesting,
because not only does it
infect human beings,
but it's also zoonotic,
and so the adult worms can
be found in domestic animals.
Two other less important species
are Schistosoma intercalatum, which
is found in Africa, and S. mekongi
in Asia, as you could expect,
in the Mekong River.
