IN ANIMALS continued
into a metacestode (larval or hydatid cyst). 8 In sheep, the larvae are infective to canids within a year and may remain viable for a number of years. 9 PREVALENCE AND RISK FACTORS • A 2008 national study of gastrointestinal parasites in domestic dogs (owned and in shelters) did not find E. granulosus in any faecal samples, the authors noting infection is dependent on access to carcasses, an unlikely event for many pets in Australia. 10 A 2014 study of farm and rural
0.5 mm
Echinococcus granulosus (note the small size)
• Eggs, contained in proglottids, are shed in the faeces of the definitive host following a prepatent period of approximately 6-7 weeks and are immediately infective to intermediate hosts. 8 • Susceptible intermediate hosts are infested through ingestion of eggs on pasture and in water. Following ingestion, the eggs hatch to release the oncosphere, which uses its hooks to burrow through the intestinal wall. They then enter the circulation and are transported to the organs, especially the liver and lungs. After localisation, the oncosphere develops Life cycle of Echinococcus granulosus sensu lato
Hepatic echinococcosis in a sheep (Public Health Image Library, CDC)
Life cycle of Echinococcus granulosus
D.H. Dog and other canids
Protoscolices (evaginated-above, invaginated-below)
Cysts, typically 2–3 cm across, containing numerous protoscolices
Unilocular hydatid cysts
Adult
Immediately infective, persist for months in the external environment
The embryo migrates through the intestinal wall of the I.H. and disseminates through the blood vessels
Segments excreted in the faeces
I.H.
Embryonated egg
D.H. = definitive host I.H. = intermediate host
Extracted from the Textbook of Clinical Parasitology in dogs and cats, Beugnet F., Halos L., Guillot J., Ed Servet, 2018. Life cycles adapted from Pet Owner Educational Atlas. Parasites, Carithers D. and Miro G., Ed Servet, 2012. Life cycle from Beugnet, F., et al (2018) Textbook of Clinical Parasitology in Dogs and Cat. Grupo Asis Biomedica, S.L.; Adapted from Carithers, D., et al (2012) Pet Owner Educational Atlas.
CONTENTS
Companion Animal Zoonoses Guidelines 55
Made with FlippingBook - professional solution for displaying marketing and sales documents online