in vitro culture and isoenzyme analysis of giardia lamblia

in which travellers (Brodsky et al., 1974), experimentally infected humans (Nash et
al., 1987) and animals (Roberts-Thompson et al., 1976; Aggarwal and Nash,
1987) developed symptoms after exposure. Infections give rise to varying clinical
signs and symptoms from asymptomatic cyst passage to acute and chronic
diarrhoea associated with villous atrophy, malabsorption and growth impairment in
children (Farthing et al., 1986; Hjelt et al., 1992). Consequently, renewed interest
has been shown in this genus. It has since been considered an important public
health problem and the most frequently identified intestinal protozoan parasite,
particularly in the United States (Wolfe, 1979; Smith et al., 1982; Hill, 1990).
Transmission is mainly via the faecal-oral route. For this reason, it is more likely to
be endemic in areas that are characterised by poverty, over-crowding, poor
personal hygiene, lack of proper sanitation facilities and inadequate purification of
water supplies. However, it also has a considerable impact in developed countries
such as the United States, Great Britain and Australia as discussed in the
preceding section.
Although establishment of axenic laboratory cultures was achieved two decades
ago thereby facilitating study of these organisms in vitro, many key areas still
require clarification such as:
1.5.1 Pathogenesis.
Many theories have been postulated. Early investigators (Erlandsen & Chase,
1974) suggested the possibility that numerous organisms in the small intestine act
as a mechanical barrier leading to malabsorption. This was disputed on the basis
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