IN HUMANS continued
• The initial phase of the primary infection is typically asymptomatic. Small, well-encapsulated, non-progressive or calcified cysts may not induce clinical signs, and patients may remain asymptomatic for years or permanently. 9,21 • Clinical presentation of hydatid disease is variable, with the nature and severity of signs dependent on the size, location and number of cysts. The onset of symptoms may be gradual once cysts become large enough to exert pressure on surrounding tissues and structures. Symptoms reflect impairment of the organ involved. Sudden onset of clinical signs is likely due to cyst rupture, which can lead to
• The liver is the most frequently parasitised human organ, accounting for 50-70% of cases, followed by the lungs (20- 30%) and less commonly the spleen, kidneys, heart, bones and central nervous system. 21 • Diagnosis of cystic echinococcosis is based on clinical findings, imaging and serology. A standardised classification system is used for the analysis of cystic echinococcosis in the liver, which can also be applied to cysts located in other tissues. Cysts that are not accessible to ultrasound can be examined using other imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI). Standard radiology is useful to diagnose thoracic and bone involvement. Microscopic examination of protoscolices post cyst fluid aspiration and histology can provide further evidence of the viability of cysts. 23 • Treatment options for cystic echinococcosis vary depending on the number, size and stage of cysts, using criteria developed by the WHO, and range from observation alone, drug therapy alone, percutaneous drainage, and surgical excision.
anaphylaxis or secondary bacterial infection. 20,22 • Ruptured or leaking cysts can cause secondary
echinococcosis, with leaking cysts releasing viable larval tissue stages (protoscolices). Surgical treatment can also cause trauma-induced rupture of primary cysts resulting in secondary hydatidosis. 19,22
KEY CONSIDERATIONS 1. An essential aspect of canine infestation is access to raw carcasses of livestock and wild animals. Dogs should not be fed raw meat or offal 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. 2. Infested dogs, even those with high worm burdens, do not show clinical disease. 3. If dogs have known or suspected exposure to E. granulosus, deworming every six weeks with praziquantel is recommended to minimise the public health risk from shedding of infectious eggs. Faeces from recently dewormed dogs should be disposed of by burning or deep burial.
Restricting access to raw carcasses (including offal) of livestock and wild animals can prevent E. granulosus infestation in dogs
References: 1. Beveridge, I., et al (2015) Australasian Animal Parasites: Inside and Out. Australian Society for Parasitology. 2. Armua-Fernandez, M.T., et al (2014) First case of peritoneal cystic echinococcosis in a domestic cat caused by Echinococcus granulosus sensu stricto (genotype 1) associated to feline immunodeficiency virus infection. Parasitol Int, 63(2), 300-2. 3. Konyaev, S.V., et al (2012) The first report on cystic echinococcosis in a cat caused by Echinococcus granulosus sensu stricto (G1). J Helminthol, 86(4), 391-4. 4. Jenkins, D.J., et al (2003) Transmission ecology of Echinococcus in wild-life in Australia and Africa. Parasitology , 127, S63-S72.. 5. Jenkins, D.J. (2006) Echinococcus granulosus in Australia, widespread and doing well! Parasitol Int, 55 Suppl, S203-6. 6. King, S., et al (2007) Hydatids - you, too, can be infected NSW DPI primefact, 475. 7. Barnes, T.S., et al (2007) Clustering of hydatid infection in macropodids. Int J Parasitol, 37(8-9), 943-52. 8. Mandal, S., et al (2012) Human cystic echinococcosis: epidemiologic, zoonotic, clinical, diagnostic and therapeutic aspects. Asian Pac J Trop Med, 5(4), 253-60. 9. Beugnet, F., et al (2018) Textbook of Clinical Parasitology in Dogs and Cats. Grupo Asís Biomedia, SL. 10. Palmer, C.S., et al (2008) National study of the gastrointestinal parasites of dogs and cats in Australia. Vet Parasitol, 151(2-4), 181-90. 11. Jenkins, D.J., et al (2014) Echinococcus granulosus and other intestinal helminths: current status of prevalence and management in rural dogs of eastern Australia. Aust Vet J, 92(8), 292-8.
12. Jenkins, D.J., et al (2006) Detection of Echinococcus granulosus coproantigens in faeces from naturally infected rural domestic dogs in south eastern Australia. Aust Vet J, 84(1-2), 12-6. 13. Harriott, L., et al (2019) Geographical distribution and risk factors for Echinococcus granulosus infection in peri-urban wild dog populations. Int J Parasitol Parasites Wildl, 10, 149-155. 14. Jenkins, D.J., et al (2003) Echinococcus granulosus in wildlife in and around the Kosciuszko National Park, south-eastern Australia. Aust Vet J, 81(1-2), 81-5. 15. Craig, P., et al (2015) Echinococcus granulosus: Epidemiology and state-of-the-art of diagnostics in animals. Vet Parasitol, 213(3-4), 132-48. 16. Varcasia, A., et al (2004) The diagnosis of Echinococcus granulosus in dogs. Parassitologia, 46(4), 409-12. 17. Jenkins, D.J., et al (2004) Cystic echinococcosis in Australia: the current situation. Southeast Asian J Trop Med Public Health, 35(1). 18. Keong, B., et al (2018) Hepatic cystic echinococcosis in Australia: an update on diagnosis and management. ANZ J Surg, 88(1-2), 26-31.
19. McManus, D.P., et al (2003) Echinococcosis. Lancet, 362(9392), 1295-304. 20. Moro, P., et al (2009) Echinococcosis: a review. Int J Infect Dis, 13(2), 125-33.
21. Bhutani, N., et al (2018) Hepatic echinococcosis: A review. Ann Med Surg (Lond), 36, 99-105. 22. da Silva, A.M. (2010) Human echinococcosis: a neglected disease. Gastroenterol Res Pract, 2010. 23. Brunetti, E., et al (2010) Expert consensus for the diagnosis and treatment of cystic and alveolar echinococcosis in humans. Acta Trop, 114(1), 1-16.
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Companion Animal Zoonoses Guidelines 57
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