Page 187 - The Veterinary Laboratory and Field Manual 3rd Edition

156 Susan C. Cork and Mani Lejeune

the vesicular fluid forming hydatid ‘sand’. The trEatMEnt
cyst progressively increases in size, displacing • The hydatid tapeworm can be more difficult
organs. Not all the cysts contain protoscolices to remove than the Taenia sp. but several
but those that do are infective to dogs after 5 anthelmintics, notably praziquantel, are now
to 6 months. Infectious scolices are transmitted available which are highly effective. After
to dogs when they eat raw infected meat. Adult treatment it is advisable to confine dogs for
tapeworms reach maturity 6 to 7 weeks later. up to 48 hours to facilitate collection and
disposal of faeces containing parasite eggs.
cLInIcaL SIGnS • In humans, hydatid cysts may be excised
The adult tapeworm is not pathogenic and thou- surgically. In some cases, hydatid cysts have
sands may be present in a dog without clinical been found incidentally when a patient is
signs. Domestic animals with hydatid cysts in undergoing surgery or radiography for other
the liver or lungs may not demonstrate clear conditions.
signs of the disease and the majority of the
infections are only revealed at post-mortem controL
inspection. However, the rupture of a cyst may • Health education.
cause sudden death due to the development of • Control of livestock slaughter with confisca-
anaphylactic shock. Pressure by the growing tion and destruction of affected viscera.
cyst may cause a variety of clinical manifesta- • Regular treatment of dogs to eliminate the
tions if hydatid cysts are located in the kidney, adult tapeworms and prevention of infection
pancreas, nervous system or marrow of the long in dogs by exclusion from their diet of animal
bones. material containing hydatid cysts. This can be
done by preventing the access of dogs to abat-
dIaGnoSIS toirs and by proper disposal of carcasses.
Diagnosis in the intermediate host is generally • In some countries, incidental benefit from the
made by post-mortem examination of viscera destruction of stray dogs for rabies control
and other organs. The protoscolices and their has seen a great reduction in the incidence of
hooks inside the cysts can be identified under the hydatid infection in humans.
microscope. In live animals, specific diagnosis of
hydatid infection is rarely possible. Percussion of
infected liver and lungs may lead to detection of diseases caused by trematodes
hydatid cysts but these must be distinguished
from abscesses or other cystic structures. Flukes of veterinary importance include Fasciola
sp., Paramphistomum sp., Dicrocoelium sp. and
• In humans, serological tests such as ELISA, Schistosoma sp. Effective fluke prevention and
complement fixation or immunoelectrophore- control strategies require accurate and early
sis are commonly used. Scanning techniques diagnosis and an understanding of the life cycle
may also be used to locate the cysts in organs. of the parasite involved. As with other helminth
• In dogs, adult tapeworms are difficult to iden- diseases the clinical signs are variable and
tify because the segments are small. Faecal depend on the level of infection as well as the
examination for the presence of eggs can be immunity of the host.
attempted but Echinococcus eggs are difficult
to distinguish from those of other tapeworm
belonging to family: Taeniidae.

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