The occurrence of Giardia in cats and dogs in New Zealand and subsequent isolation and differentiation of strains : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Microbiology, Massey University, New Zealand
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Date
1988
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Massey University
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Abstract
Giardiasis, a debilitating diarrhoea that affects many people every year
is caused by the ubiquitous protozoan parasite Giardia intestinalis (syn
lamblia, duodenalis) . This parasite infects and causes disease in birds
and animals as well as man and has no known host specificity. Dogs and
cats are some of the animals infected by Giardia and due to their close
association with man, may be carrier sources of human giardiasis.
In an attempt to discover a relationship between man and these animals,
a survey of the level of Giardia infection in cats and dogs in both
Hamilton and Palmerston North, New Zealand, was undertaken. Percentages
of 25% and 8% for dogs and 3% and 7% for cats respectively were
obtained. Statistically the level of infection in Hamilton was higher
than that of Palmerston North. In both cities the sex and breed of the
animals showed no correlation to infection although animals less than 3
years old were more likely to be infected. Clinical manifestations of
giardiasis were observed but did not significantly correlate with the
presence of Giardia and were not necessarily caused by the Giardia when
present.
To further enhance the relationship hypothesized it was attempted to
culture the Giardia from the cats and dogs and relate them to cultured
human isolates. Our attempts were unsuccessful and from 91 samples only
8 human strains from 5 geographical areas were isolated. These
isolations were made by both in vitro and in vivo techniques that both
yielded 7% sample to culture success. The isolated Giardia strains plus a control culture, Bris/83/HEPU/106
supplied by Boreham, Australia, were compared by growth rate and sodium
dodecylsuphate polyacrylamide gel electrophoresis (SDS-PAGE) . Both these
tests showed the similarity of these strains. The average growth rate
was 0.09 ± 0.01 hours-1 and no strain varied from the statistical mean.
In relation to the total protein banding patterns measured by SDS-PAGE,
the isolates varied, at most, by one or two bands.
An isolate of G. muris extracted from a naturally infected mouse and a
human isolate that was extracted from an experimentally infected mouse
were also compared by SDS-PAGE to a cultured isolate. The results showed
many different bands between all three samples and suggests that an
adaption, or selection, of the Giardia must take place when it is
cultured. If this is so, then perhaps the emphasis put on strain
variation of cultured Giardia trophozoites is to be questioned.
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Keywords
Giardiasis, Giardia intestinalis, Giardia infection in cats, Giardia infection in dogs