in vitro culture and isoenzyme analysis of giardia lamblia

waterborne diarrhoeal disease in North America and Europe (Craun, 1984;
Jephcott et al., 1986). The organisms have been shown to resist the level of
chlorination used in many bulk water purification systems. Sole reliance on this
method can result in widespread transmission. Filtration and flocculation in
addition to chlorination is recommended in order to effectively eliminate Giardia
cysts from water supplies (Longsdon et al., 1979)
Travel (particularly to endemic areas) has also been documented to facilitate
transmission of Giardia. For example Brodsky et al. (1974) collected data on
surveillance of giardiasis in American travellers to the Soviet Union. This data
implicated Leningrad as the site of infection and tap water as the probable sburce.
Flies have been implicated in playing a role in transmission of intestinal protozoa
including Giardia, as cysts may remain alive in the fly intestine for a considerable
period (at least 24hours) and may be deposited in a viable state as early as 40
minutes after the fly has fed on contaminated material (Hegner, 1926b).
Furthermore, it is suggested that since the infective dose is very small (10-25
cysts), it is likely that flies may act as reservoirs and transmit Giardia cysts.
However Hall, (1994) noted that it would be difficult to establish whether cysts
isolated from flies are viable.
Other modes of transmission have been reported. Food-borne cases of giardiasis
have been reported with food-handlers being the most common source of
transmission of cysts to freshly prepared food (Adam, 1991) and sexual
transmission, particularly in homosexual males also occurs (Schmerin et al., 1978;
11