in vitro culture and isoenzyme analysis of giardia lamblia

Owen, 1984)
1.3. 2 The Zoonosis of giardiasis
The role of wild and domestic animals in the transmission of giardiasis to humans
remains unclear. Many animals including dogs, cats, cattle, sheep and wild aquatic
mammals have been proposed as both potential reservoirs as well as amplification
hosts for spreading human Giardia infections (Isaac-Renton, 1991). In the USA
beavers have been incriminated as an animal reservoir (Wolfe, 1979; Isaac­
Renton et al., 1993). Cross-species infections effected by several investigators in
animals such as rats (Filice, 1952), gerbils (8elosevic et al., 1983; Aggarwal &
Nash, 1987) and mice (Hill et al., 1983; Byrd et al., 1994) with Giardia from
humans provide evidence for lack of absolute host-specificity in these organisms.
Furthermore, Faubert (1988), proposed that giardiasis is a zoonosis since Giardia
species isolated from beavers and calves were indistinguishable from isolates of
human G.duodenalis at the light microscope level and, as with human G.lamblia
strains the trophozoites could be cultivated in vitro. Additionally, a report on the
occurrence of giardiasis in backpackers who drank water from areas with no
human inhabitants strongly suggested that beavers or other wild animals are
reservoirs (Barbour et al., 1976). Thompson et al. (1988) reported that all six feline
isolates (5 from Australia and 1 from the USA) were genetically identical (as
revealed by isoenzyme and DNA analyses). They were also very similar to 20 of
30 human isolates, thereby indicating that cats are a likely reservoir of infection for
humans. Meloni et al., (1988) also advocated that felines act as a reservoir of
infection to humans; therefore their potential in zoonotic transmission is important.
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