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150  Research Yields Clues on Blood Disease
     Caused By Worms in Tropical Climates
     The Washington Post,  May 10, 1969

     Schistosomes, or blood flukes, infest from 100 million to 200
million people in tropical areas from Puerto Rico to Egypt to
Thailand.

     The worms lay eggs that pass out in human feces, which must then
be taken up by water snails to produce the larval stages that infect
men by burrowing into the skin.  The distribution of schistosome
disease thus follows closely on poor sanitation coupled with exposure
to waters in which the snails breed.

     The history of the worms in the body is not a pretty story.  The
mature parasites live within the larger veins, where they do
surprisingly little direct harm.  But the eggs migrate through the
liver or bowel or urinary tract, depending on the particular species
of worm.  The irritation of these organs by the eggs leads to
widespread debilitating disease.

     The parasite shows its successful adaptation to man by only
occasionally killing its host.  For a national economy, however, such
an ailment is a more serious and insidious burden than diseases with
more dramatic, rapid lethal effects.  According to experts of the
World Health Organization, schistosome disease vies with malaria
as the world's pre-eminent public health problem.

     The organization also characterizes the disease as peculiarly
man made, for it follows upon irrigation projects that provide
year-round waters in which the snails can thrive.  Many ecologists
have warned, for example, that Egypt's Aswan High Dam now being
completed may cost far more in schistosome disease than it can
benefit in agricultural progress.

     In similar situations, WHO reports have commented that "despite
continual advice given by the Health Department, irrigation schemes
are planned and developed without due consideration of the health
aspects... Unless the danger is realized at the outset, and plans 
for prevention made... large irrigation schemes may well wreck the
health of the country and bring the most grandiose schemes to a
pitiful end."

     Schistosome researchers have long been puzzled by the ability
of the mature worms to live in the bloodstream for many years without
provoking an immunological reaction.  Recently, several research
groups have found that the worms practice a kind of immunological
camouflage, for they carry substances on their skin similar to those
of their animal host.

     Drs. S. R. Smithers and R. J. Terry of the National Institute
of Medical Research in London, have now found that these substances
are probably assimilated from the host tissue, rather than made by the
worm.  After a few weeks of life in a new host, the worms shed their
old identity and acquire one to match their present host.  Worms grown
in mice could be transferred to monkeys, for example, but would be
rejected if the monkeys had been previously immunized against mouse
tissue cells.

     To learn how the worm incorporates these surface materials from
host cells into its own skin would, obviously, be of great interest
to studies of organ transplantation for these grafts face a similar
problem.  We could also imagine the breeding of domesticated strains
of blood flukes to accomplish medically desirable changes without
immunological rejection.  More appropriately to the present world
problem, the findings suggest that people might be vaccinated against
schistosome infection with material from the snails that transmit
the disease.

     Recent progress can also be reported for a promising new drug
against the worms, now in the process of large-scale trials.
Lucanthone was discovered by Sterling-Winthrop scientists as a
metabolic product found in the urine of patients treated with an
earlier, less satisfactory drug, hycanthone.  For commercial
production, the conversion of hycanthone into lucanthone was
accomplished by a mold specifically sought for the purpose. 
Whether the drug can be realistically useful in an economically
and socially retarded country cannot yet be foretold; this one has
the advantage of requiring only one injection for a good chance of
cure.

     Other fascinating approaches follow the observation that mice
bedded on cedar shavings are resistant to infection.  Further work has
led to the isolation of active, pure compounds from essential oils.
A certain amount of work is also devoted to biological predators
either of the snails or the larvae in natural waters.

     All in all, the research effort devoted to schistosome disease
is pitifully small compared to its human importance, but it is
beginning to respond to basic scientific approaches.  This work (as
always) is also returning some fascinating dividends in basic biology.
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