Throughout 2008 there has been a substantial increase in the number of sheep being condemned due to C. ovis at Hillside, and other abattoirs.

C. ovis (Cysticercus ovis) are small (3 - 10mm) white oval cysts found various muscles of sheep and goats including the heart. They are also known as ‘Sheep Measles’ and are the ‘larval cystic’ (Larval Stage) of the tapeworm ‘Taenia ovis’ (T. ovis) found in dogs.

While Sheep and Goats are the intermediate host of T. ovis, Dogs are the definitive or final hosts of the T. ovis tapeworm. The adult T. ovis tapeworm lives in the dog’s intestine and the adult can grow to 2m in length. Dogs are infected by eating raw sheepmeat or offal, ether fed to the dog or scavenged from a carcass infected with C. ovis larvae.

The mature T. ovis tapeworm lays eggs in massive numbers which are shed in the dog’s droppings and are ingested by sheep grazing on pastures in contact with the droppings.

Once ingested by the sheep the sheep becomes the immediate host and the cycle starts over again.

Treatment and control C. ovis Tapeworm cysts in sheep.

As there are no commercially available treatments for C. ovis cysts in sheep and goats the only control method is to break the dog-sheep-dog cycle. This is done by ‘worming’ all domestic dogs on the property every 6 weeks with treatment that contains Praziquantel.

Adult sheep carry the cysts for a very long time, so control may take several years. While there is some evidence that Dingos and Foxes can become infected with tapeworms, it is rarely T. ovis and the most likely source of infection is domestic working and house dogs.

Costs to lamb production.

Hillside is an export abattoir and sheep found with C. ovis cysts are ineligible for export. To maintain high standards and a quality product, Hillside does not allow it to go to domestic consumption either. Severe cases are fully condemned, while the remainder are fully cut up and inspected, with the unaffected meat going to trim.
In past years, C. ovis would only account for a few lambs per day. We are now condemning up to 30 carcasses for C. ovis EACH DAY. As there is a considerable loss of value of the product, Hillside have introduced a 40% deduction in value of all partially condemned C. ovis bodies, effective 20/10/2008.

For further information on the control of C. ovis please contact Dr Anna Erickson, the Veterinary Officer at the Department of Agriculture and Food in Narrogin on 08 9881 0222, or Dr Caroline Jacobson, Murdoch University on 08 9360 6397.

Rob Shepherd, Hillside.