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1. Name two common signs associated with a severe infection of either barber’s pole worm or liver fluke.
2. In summer rainfall areas, should dag scores be used to reduce fly strike risk?
3. What can be added to many dipwashes to limit the spread of dermo?
Image: Angora goats. Source GT Ferriera, AZ Genetics P/L.
Severe acute or ongoing (chronic) blood loss from either barber’s pole worm or liver fluke leads to obvious signs of anaemia. These are pale gums and conjunctiva (inside the eyelids); lack of stamina causing lagging or collapse when mustered; and ultimately death from lack of red blood cells needed to carry oxygen around the body.
Swelling under the jaw (bottle jaw) results from both severe barber’s pole worm and liver fluke infections. The loss of blood results in anaemia and less protein in the blood. This imbalance in the normal body fluids results in fluid accumulating under the jaw in some, but not all, affected animals. It does not always occur during an outbreak of barber’s pole worm disease, and can also be caused by other factors (e.g. a severe lack of protein in under-nourished sheep).
In the summer dominant rainfall environment few sheep get severe dags, but those that do so in the fly season are at extreme risk. Therefore, it can be worthwhile to cull sheep with heavy dag (same as culling sheep that actually get flystruck).
Generally, in environments where dag is sporadic or few sheep are affected, dag is better handled through management, rather than applying valuable selection pressure to dags, which could be used for other traits.
Zinc sulphate heptahydrate is registered as a bacteriostat to minimise the spread of dermo between sheep during dipping, but will not have any effect on active lesions. Product labels carry directions for the addition of 10 kg of zinc sulphate heptahydrate per 1000 litres of dip water (1% solution). Some dipping product labels suggest adding chlorhexidine disinfectants (e.g. Hibitane®) for general dip hygiene, but these have no registered claims against the spread of dermo.