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Health and Safety Photo: Fleur Muller Zoonotic diseases Fleur Muller Take tapeworms by the collar ©Kondinin Group Reproduction in whole or part is not permitted without permission. FreecalL 1800 677 761 kondinin group 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 9