Earlier in December I came across this blog
about the Guinea worm, a parasite you really don't want to be infected
with. For more information about it, follow the link in the previous sentence,
or this
about efforts by the Carter Center (founded by former US President Jimmy
Carter) to eradicate it. The worm relies on humans to complete its life cycle,
so there is no reservoir of infection in other species, and infection can be
avoided by measures as simple as filtering drinking water through fine cloth; as
a result, these efforts have been very successful, reducing the number of cases
from 3.5 million in Africa alone in 1986 to less than 5000 (all in a few African
countries) in 2008.

It seems likely that before long, Guinea worm disease (or dracunculiasis to
use its technical name) will join smallpox to become the second disease to be
eradicated worldwide. This will still require a considerable amount of effort
and money, as the last few areas where transmission occurs are often poor,
remote and politically unstable; the Bill & Melinda Gates Foundation and the
UK's Department for International Development recently announced that they were
providing 55 million dollars to ensure eradication. Almost everyone,
especially people living in areas where the disease used to be a problem, will
agree that it will be very good news when the Guinea worm is extinct.

One website takes a different view, however: the Save the Guinea Worm
, which asks 'Why are we willingly destroying an endangered
species?', and tries to make the reader feel sorry for the poor little Guinea
worms ('It has a nervous system. Its hearts pump blood through its small body',
and so on). They even claim to be recruiting volunteers to host Guinea worms and
so save them from extinction.

I think this site is intended as a joke (and I suspect that this page is meant to
satirize people who maintain that HIV does not cause AIDS) — let me know if you
disagree! However, if you consider the wider question of parasite biodiversity,
there is a serious issue — biodiversity includes all species, not just those
that are cute or charismatic (and of course cute or charismatic species may be
troublesome to people who live near them). Robert Poulin and Serge Morand in
their book Parasite Biodiversity1 estimate that more than
100,000 of the approximately 1.5 million known species are parasites, and that
the true number of parasite species is likely to be much higher. They argue that
people have a responsibility to conserve all organisms, and cite studies
indicating that parasites often play important roles in ecosystems and sometimes
turn out to be beneficial to humans (for example, a number of studies indexed in
CAB Abstracts suggest that exposure to parasitic worms, or compounds from them,
can make allergies less likely).

This2 and other articles by Donald Windsor under the title 'Equal
Rights for Parasites' make similar points, and this
describes a particular example: when some rhinoceroses were moved to
a safe reserve to protect them from hunting, all their parasites were removed,
but it was found that oxpeckers (birds that sit on the backs of rhinos and catch
insects) stopped breeding in the absence of large ticks to feed to their young;
if they had disappeared as a result, the rhinos would have lost their protection
against biting insects.

It's interesting that the last official stocks of smallpox virus, which you
might think would be of even less concern to conservationists, have still not
been destroyed as far as I know, although this owes more to the fear that
unofficial stocks might be used for bioterrorism, and the consequent continued
interest in smallpox research, than to any ethical qualms about exterminating a

Of course few will mourn the extinction of the guinea worm, most parasites of
humans and common animals aren't in any danger, and conservation of wild animals
will automatically conserve many of their parasites too, so I doubt if we will
be seeing serious appeals to save parasite species in the near future. But it's
probably worth wondering whether killing off everything that (however
justifiably) we don't like may sometimes not be an unmixed blessing.

1: Poulin, R. and Morand, S.: Parasite Biodiversity (Smithsonian
Books, 2004) ISBN: 1-58834-170-4.

2: Windsor, D.A.: 'Equal rights for parasites'. Perspectives in Biology
and Medicine
(1997) 40 (2), pp. 222-229

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