HYDATID DISEASE (Echinococcus granulosus)
• Echinococcus granulosus sensu stricto (s.s.) is a tapeworm endemic to parts of Australia. • Echinococcosis is asymptomatic in the primary host (domestic and wild canids), however infestation of intermediate hosts can result in disease. • Infection of humans results in hydatidosis or unilocular (cystic) echinococcosis, a cyst forming disease that can present as a clinically significant zoonosis.
ACAZAP RECOMMENDATIONS
• Feeding dogs cooked meat or commercial dog food is recommended. Provision of raw meats or meat by-products increases the risk of hydatid tapeworm infestation. • Avoid feeding raw meat and offal to dogs, especially liver, lungs and other organs from on-farm slaughtering processes. • Dogs, particularly in endemic or rural areas, should be supervised or restrained to prevent scavenging on dead livestock and wild animals (including macropods and feral pigs).
• If dogs have known exposure to E. granulosus or access to offal, deworming every six weeks with praziquantel is required. • Praziquantel is not ovicidal, therefore tapeworm eggs within proglottids passed in the faeces are infective and could contaminate the environment following deworming. Faeces from ‘at risk’ dogs should be safely disposed of by deep burial or burning for 24 hours following deworming with praziquantel. • Practice good hand hygiene following contact with dogs, playing outdoors, and prior to eating.
IN ANIMALS
AETIOLOGY AND EPIDEMIOLOGY • The life cycle of E. granulosus is indirect involving predator-prey transmission between the definitive
canid host and intermediate (mammalian) hosts. Dogs and other canids are infested after ingesting viscera, offal or meat containing fertile hydatids from an intermediate host. • Domestic dogs, wild dogs, dingoes (and their hybrids), and less commonly foxes, are the known definitive hosts in Australia. 1 • Cats are not definitive hosts for E. granulosus but may serve as an accidental intermediate host. 2,3 • Intermediate hosts are herbivorous or omnivorous mammals. Echinococcus granulosus s.s . is widespread in mainland Australian native wildlife including macropods (e.g. eastern grey kangaroos, red-necked wallabies and swamp wallabies) and wombats, as well as domestic and feral introduced species (including sheep, cattle, goats and pigs). • The larval (metacestode) stages commonly develop in the liver, lungs and various organs of the intermediate host. Clinical signs associated with infestation of livestock are rare, however production losses may be seen. Lung cysts leading to pulmonary dysfunction and fatalities in macropods have been reported. 4
Scavenging on macropod carcasses is a risk factor for echinococcosis in dogs
• Two major transmission patterns are noted to occur: the sylvatic (or wildlife) pattern involving wild dogs and dingoes via predation of macropods, and the domestic pattern involving farm dogs and sheep. 5 Cattle and feral pigs are mostly infected with sterile cysts. 6 Sheep and certain species of macropods are the primary intermediate hosts in Australia, being the main source of fertile cysts. 5,6 • When mature fertile cysts are ingested by canids, the cyst wall is digested away, freeing the protoscolices, which attach and develop into adult tapeworms in the dog’s small intestine.
CONTENTS
54 Companion Animal Zoonoses Guidelines
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