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Infestation of humans and animals by parasitic worms has
been known since ancient times. The prevalence of Toxocara
in dogs was first reported in the 18th Century, but the first
systematic study of its extent was made in 1908 (Nuttall
and Strickland). It was found that 17 out of 24 dogs in
Cambridge were infested. Surprisingly however, it was not
until 1950 that the first nematode larva was observed in a
human liver (Mercer et al 1950) and assessed
as the cause of the symptoms we now associate with toxocariasis.
Soon after, larvae were found in other human tissues, and
the connection between the disease and the dog became firmly
established.
There have been many contributions to the understanding of
the subject, but is was probably the work of Sprent (1958)
that finally elucidated the life-cycle of Toxocara canis
and the mechanisms underlying the disease syndrome. In the
years following the 1950 discovery, of the link between dogs
and toxocariasis in humans, there was much interest among
medical scientists and a consequent research effort into all
aspects of it. Ashton (1960) demonstrated some of the
difficulties in diagnosis.
In recent years, the development of sensitive and more specific
tests have made diagnosis more certain. It was not long before
dog interests began to re-state the findings and to focus
public attention on the comparative rarity of blindness due
to toxocariasis. For many years this was the only manifestation
of the disease of which the public, and then only a small
minority, seemed to be aware. After those first discoveries,
later research tended to be on other effects of the disease,
and its findings did not receive significant media attention.
The findings of clinicians were similarly under-publicised.
Excellent reviews of the subject have been carried out (Woodruff
1970; Gillespie 1987) and more recently a reminder that
blindness from toxocariasis is still a matter for concern
has been published (Gillespie 1993). But the mass of
evidence the research has uncovered over the years since 1950
is not readily available to the general public and the tomes
in which it is recorded are forbidding to many people.
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