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University of Alberta
Giardiasis
in Alberta
Common
name
giardiasis, beaver
fever
Scientific
name
single-celled animal
(protozoan), Giardia
lamblia (=G. duodenalis, =G. intestinalis)
What’s
Bugging
Wild
Critters?
Fact sheet #37:
Giardiasis
Significance
Giardia lamblia is a widespread and
common intestinal inhabitant of humans. It also readily occurs in pets and
livestock, and spills over into wild species. Any of these species can produce
stages that are infectious to people.
Infections in humans range from mild
flu-like disease to more serious longterm illness. Infections in wild species
largely go unnoticed.
tion in a broad range of habitats, that
is, in other species.
Transmission Cycle
What? Where? How?
Giardia spp. passes from one individual
to another by direct transfer from
faeces to mouth (faecal-oral route).
The cycle starts with hardy free-living
cysts in the faeces. They can survive
a range of temperatures and humidity,
and can live for months in cold water
or in damp, cool substrates.
There are numerous species of Giardia, yet the same species occurs
commonly in humans, cattle, horses,
sheep, pigs, cats, and dogs throughout the world and also can survive in
a variety of wild mammals and some
birds. Young animals of all species are
more likely to be infected than older
individuals. It is likely that all these
species share their Giardia cysts with
each other! Thus these little animals
are a classic example of a generalist
species that can find suitable conditions for shelter, food, and reproduc-
Transfer of infective cysts often
involves water. The risk of cysts occuring in water is highest in situations
with high-density human populations,
poor hygiene, contamination of natural
watersheds, or inadequate treatment
of domestic water supplies. Large
concentrated livestock operations also
increase the risk of cysts in the environment.
Microscopic Giardia cysts were found
in faeces of ancient humans, and thus
this tiny protozoan (one-celled animal)
has co-existed with our own species
for many thousands of years. Indeed,
the two species no doubt evolved side
by side (or rather, one inside the other). The first description of Giardia
was in 1681 – probably some of the
first animals examined with a microscope. Nowadays giardiasis is the most
common intestinal disease in people.
Once they are eaten with water, food,
or faeces, each cyst releases a reproductive form (trophozoite) which attaches to the intestinal wall and multiplies rapidly. Damage associated with
trophozoites affects the intestine’s
ability to absorb water and nutrients,
and increases the movement of cells
lining the gut. This often results in
excess moisture in the faeces (i.e.,
diarrhoea!). As the environment in the
intestine changes, so does Giardia. As
they move down the gut, trophozoites
change back to cysts and are passed
out with the soggy faeces.
Giardiasis in Alberta
(Giardia lamblia)
Distribution in Alberta
Giardia likely occur throughout Alberta.
Cysts are commonly found in humans and
have been recovered from domestic (including dog, cattle, swine, farmed elk, farmed
bison) and wild (beaver, muskrat, various
voles and mice) sources in the province. Individual infections in humans are not uncommon. Outbreaks of human giardiasis have
occurred in various communities, including
Banff, Canmore, Edmonton, and Morley.
Importance for Wildlife
Management
Infections of Giardia spp. are not
known to adversely affect wildlife. Wild species seem to
live in harmony with these
protozoans.
of “beaver fever” is a complete misnomer.
“People fever” or perhaps “people, pets and
livestock fever” would be more accurate,
although admittedly not as easy to say!
Giardia is of concern to dog and cat breeders as well as livestock producers. Infections can lead to lower weight gain and
lower final body weight of infected animals.
In addition, these animals can contaminate
water sources and thus increase the risk
of infection in humans and wildlife. Pets
and livestock on backcountry trails, in
parks, and on grazing leases in forested areas are of particular concern. Similarly, treatment of
waste from intensive livestock
operations is essential if
further contamination of
the environment is to
be avoided.
Public Significance
Public water sources in Alberta are regularly screened
for Giardia and any cysts automatically removed during the
treatment processes. However, hikers, campers, hunters, fishermen, and
canoeists are at risk when using untreated water in the backcountry, and a bout of
giardiasis can certainly take the edge off
the enjoyment of your trip.
While this parasite is extremely common,
human outbreaks or serious infections are
relatively rare. The majority of cases are
asymptomatic (showing no signs of disease),
but some people exhibit acute or chronic
diarrhoea, abdominal cramps, bloating, dehydration, fatigue, and weight loss. Infections usually run their course in 2-3 weeks.
Children are particularly at risk.
Most infections result from contamination
of watersheds by humans or livestock rather than from wildlife. The common name
October 2014
Prevention/Control
Giardiasis can be readily avoided. Personal preventative measures include proper
disposal of faeces, wise personal hygiene
(including food preparation), and protection
of public water supplies from contamination with faeces of any species. Boiling kills
Giardia cysts. And certain water filtration methods remove most cysts. However,
chlorination at concentrations that kill most
other organisms in water does NOT kill
Giardia cysts.
If infection occurs, humans, pets, and
livestock can be treated successfully with
a variety of drugs. Progress is being made
towards a vaccine that could prevent infection in livestock and pets. However, potential transmission from people, livestock and
pets to wildlife should be avoided wherever
possible.
Wildlife diseases in Alberta: esrd.alberta.ca/fish-wildlife/wildlife-diseases/
Giardiasis in Alberta
Centers for Disese Control - trophozoites
(Giardia lamblia)
Summary
Giardia is one of the most common parasites in humans around the world, including Alberta.
Be sure that you do not add to the problem: properly dispose of all faeces from yourself,
your livestock, and your pets. Care should be taken whenever untreated water is used for
drinking or even brushing your teeth! Boiling prior to drinking kills all Giardia in the water.
Additional Information
Parasitic Diseases of Wild Mammals, Second Edition. Edited by William M. Samuel, Margo J. Pybus
and A. Alan Kocan. 2001. Chapter 16 – Enteric Protozoans.
Alberta Agriculture, Food & Rural Development:
cattle -www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/beef11744
dogs -www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex736?opendocument
cats - www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex737
Health Canada: www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/giardia_cryptosporidium-eng.php
Merck Veterinary Manual Online: www.merckmanuals.com/professional/infectious_diseases/intestinal_protozoa/giardiasis.html?qt=giardia&alt=sh
October 2014
Wildlife diseases in Alberta: esrd.alberta.ca/fish-wildlife/wildlife-diseases/