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Health and Safety
Photo: Fleur Muller
Zoonotic diseases
Fleur
Muller
Take tapeworms
by the collar
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Close contact: Dogs can become infected with
hydatid tapeworms by eating sheep offal
containing hydatid cysts.
At a glance
Contact with dog faeces infected
with tapeworm eggs can cause
hydatid disease in humans.
Hydatid cysts can form in the
internal organs of humans, which
in some cases can result in death.
Washing hands thoroughly after
gardening and handling dogs and
before eating and drinking can
help protect against infection.
Control tapeworm in farm and
house dogs through regular worm
treatments and by not feeding
dogs raw offal.
Wild dogs can carry high levels of
hydatid tapeworms.
Keeping man’s best friend parasite free is essential to ensuring working
dogs remain in peak condition. Importantly it also protects owners and their
families from the potentially serious but highly-preventable, hydatid disease.
Prevention is the key to managing the
dangerous zoonotic disease — hydatids.
Passed on to humans through tapeworm
eggs from dogs and other animals, hydatid
cysts can lodge in the soft internal organs
of humans, such as the lungs or brains,
causing organ failure and possibly death.
The history of hydatids
For more than 200 years hydatid disease
has threatened the health of farmers
and their families, particularly in the
sheep-producing regions of Australia.
The introduction of
worming tablets containing
praziquantel and dried dog
food saw the incidence of
the disease fall from the
high levels recorded during
the 1960-1970s.
But producers need to remain vigilant so
working dogs do not become a source of
infection for livestock and people.
Tiny tapeworm
Hydatid disease is caused by a tapeworm
Echinococcus granulosus, which infects
animals including dogs, dingoes and foxes.
Thousands of adult hydatid tapeworms
can live in the small intestine of an
apparently healthy dog without causing
disease. Infected dogs can pass hydatids
onto humans, sheep, cattle, pigs,
kangaroos, wallabies and wombats, where
8 Farming Ahead March 2010 No. 218 www.farmingahead.com.au
they form cysts in internal organs. Goats,
camels and deer also are considered
potential hosts in Australia.
Human hydatid disease is serious,
potentially fatal and treatment usually
requires major surgery. In domestic livestock
hydatid cysts can lead to a downgrading of
edible offal by-products.
Cysts put health at risk
Human infection occurs as a result of
close contact with infected dogs, foxes or
dingoes and their faeces. Farmers and
hunters who have regular contact with
domestic and wild dogs and foxes have a
high risk of accidental infection.
Wild dogs (dingoes and dingo hybrids)
can carry up to 300,000 tapeworms making
them a significant threat to human health.
Children also have a high risk of
infection due to their close contact with
dogs and generally lower standards of
personal hygiene.
Sticky situation
Tapeworm eggs are microscopic and
sticky and easily transferred from dogs to
human hands. They are readily ingested
via eating or smoking and when in the
body the eggs release a small hooked
embryo, which burrows through the gut
wall and into soft tissue such as the lungs,
liver and kidney via the bloodstream. The
embryo lodges in these tissues and forms a
water cysts.
Cysts grow at different speeds depending
on the species of host and can range in size
from 0.4 millimetres to 200mm. A mature
Health and Safety
Zoonotic diseases
Symptoms and diagnosis
About 80–100 new cases of human
hydatids are diagnosed in Australia annually
but some experts say the incidence is under
reported with actual numbers higher. Since
2001 hydatid cases are no longer required to
be reported to health authorities. Hospital
records from New South Wales and the
Australian Capital Territory indicate that
321 patients were treated during the period
1987–92 with 195 new cases and 117
recurrent cases. But regardless of the
number for those affected by hydatids the
results can be serious and ongoing.
Cysts in humans can grow slowly in the
body for long periods without causing
symptoms making hydatid disease hard to
diagnose. Often an infection picked up as a
child may not appear until months or even
years later with some reports of cases
appearing 20 years after infection. In some
instances the body can fight the parasite and
prevent cysts from forming but this is not
always the case.
Patients can display various symptoms
depending on the location of the cysts within
the body. The liver is most commonly
affected (70%), while other soft tissue organs
such as lungs (20%), kidneys and the brain
can also be affected. Rare cases of hydatid
cysts forming in the thyroid gland, heart or
even within bone have been reported. Often
the patient only discovers they have been
infected when the hydatid cysts rupture or
leak. A heavily infested organ may fail or a
cyst can rupture and cause a life threatening
allergic reaction.
Hydatid symptoms include:
• Swollen Abdomen.
• Weakness and fatigue.
• Cough.
• Blood or the fluid from a ruptured cyst
may be coughed up.
Photo: Fleur Muller
Out with offal
Dogs, dingoes or foxes can become
infected by swallowing tapeworm heads
contained in fertile cysts present in raw offal
or by eating meat or blood that was
contaminated by cyst fluid during slaughter.
After becoming imbedded in the lining of
the dog’s intestine the tapeworm head
grows, reaching maturity after 42 days.
When mature a segment of the tapeworm
containing up to 1000 eggs is shed in the
dog’s faeces every 7–10 days.
These tapeworm eggs are resistant to
weathering, readily scattered by wind, water
and flies and are cold tolerant. Their ability
to survive outside a host for at least one year
means dog kennel areas, playgrounds,
vegetable gardens and pastures can all be
sources of contamination.
Photo: David Jenkins, CSU
cyst can contain hundreds of thousands of
tapeworm heads, which can potentially
form new secondary cysts when the
primary cysts ruptures and releases the
tapeworm heads. Not all hydatid cysts are
fertile. Sheep, kangaroos and wallabies
generally carry the most fertile cysts. Some
cysts can die as the host animal ages.
Close contact: The close relationship between children and dogs means extra care is needed to
prevent children becoming infected. Teaching them the importance of hand washing after playing
with dogs should start from an early age. INSET: Hydatid cysts: Hydatid tapeworms need an
intermediate host, such as sheep, to complete their life cycle with infected animals developing cysts
in soft tissue such as the liver.
• Jaundice — pressure from an enlarging
cyst may cause jaundice
Seek treatment
Without adequate medical treatment
hydatid disease can be fatal.
Surgery is the main form of
treatment but it comes with
the risk that a hydatid cyst
may rupture, resulting in
the spread of tapeworm
heads.
High doses of drugs may also be used in
combination with surgery to destroy any
remaining tapeworms. The disease can
reoccur and about one in three people
treated may develop hydatid disease again.
Control and treatments
While thorough hygiene will reduce the
chance of infection, preventing dogs
becoming infected is the best way to break
the hydatid disease cycle. Reduce the
incidence of becoming infected with hydatid
tapeworm by:
• Feeding only manufactured dog foods
and not feeding dogs uncooked or
cooked offal from sheep and kangaroos
— this includes offal bought from the
supermarket or butcher.
• Preventing dogs from roaming or
straying and in particular, accessing dead
sheep and kangaroos.
• Washing hands with soap and water after
handling dogs, gardening and working
in potentially contaminated areas such as
around kennels.
• Instructing children to do the same
— and supervise their hand washing
activities. Teach them sound
hygiene habits.
• Worm dogs every 4–6 weeks to prevent
infection, especially rural dogs that may
have access to animal carcasses.
• Keep in mind, infected dogs may not
show any symptoms, so do not assume
apparently healthy dogs are parasite free.
• Remove and bury dog faeces away from
dog kennels.
• Bury offal in a covered pit to prevent
dogs gaining access.
• Fence the vegetable patch to prevent pets
and wild animals from defecating on the
soil and wash all vegetables before eating.
Canine health
Worm dogs with an all wormer containing
praziquantel — the only drug 100 per cent
effective against the hydatid tapeworm. It is
safe to give to dogs and can be readily
administered in dog food. Remember, dogs
may remain infected for 2–3 days after
treatment. Dogs at an ongoing risk of
infection, such as working dogs, will need to
be treated every six weeks.
Contact David Jenkins,
Charles Sturt University
(02) 6933 4179
[email protected]
Corporate support
The health and safety
section in Farming Ahead
is supported by WFI, a
member of the Wesfarmers group.
Farming Ahead March 2010 No. 218 www.farmingahead.com.au
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