This covers the important worms and aspects about them you should know most about.
For those who like to see all the information and simply read through it in order. Each heading is a link to a page of information—the dot point provides a summary of the page.
Tip: Keep this page open and open the links in new tabs.
The cost of roundworms
A short description of the cost of worms to Australia’s sheep industry.
Roundworm life cycle
A diagram and description of the stages within the worm life cycle and how these affect control of and contamination by roundworms.
Worms on pasture
A table showing factors contributing to paddock contamination with worms
Signs of worms
The clinical signs that can be present with infection by various worms.
Barber's pole worm
A description about barber’s pole worm, its location, signs, diagnosis and treatment.
Black scour worm
A description about black scour worm, its location, signs, diagnosis and treatment.
Brown stomach worm
A description about brown stomach worm, its location, signs, diagnosis and treatment.
Sheep intestinal tapeworm
A description about the sheep intestinal tapeworm, its location, signs, diagnosis and emphasis that treatment for this very obvious and common worm is NOT warranted.
Other worm pages
These pages are optional reading, as the worms are less important and are generally controlled when treatment of the more important worms is carried out.
For those who prefer a problem based approach to learning, answer the following questions.
Each of the questions below links further down the page to the answers.
You can also click on each question below to go to WormBoss pages with related information.
The impact of roundworms represents the highest animal heath cost to the Australian sheep industry. Typically, lost production accounts for over 80% of the total cost with control accounting for less than 20%.
This is the time taken for infective larvae, eaten by a sheep grazing pasture, to develop to adult worms in the gut, mate and start laying eggs, which appear in dung. The time depends on the worm species with barber’s pole worm completing this period in a minimum time of 18 days under ideal conditions. Most scour worms take about 21 days.
Therefore, little, if any, worm egg contamination of pastures will come from sheep in the pre-patent period from a few days after they have been given an effective drench that kills 98% or more of the worms present. Allow sheep to graze up to 21 days in barber’s pole worm areas and to 30 days in southern scour worm areas. This is a principle used in ‘Smart grazing’.
As worms require both warmth and moisture for eggs to develop to larvae (above 10–18°C depending on worm species, but ideally below 35°C, and with usually more than 15 mm rain over 4–7 days of rainy or overcast weather when the evaporation rate is low), there can be extended periods of the year in some locations when worms cannot successfully complete their life cycle. These include regions with particularly cold winters or hot summers or where there are lengthy dry periods.
Barber's pole worm eggs will die if these conditions are not met within about 10 days of them being deposited on the pasture. Scour worm eggs are able to survive a few more weeks awaiting suitable conditions for hatching
Hypersensitivity typically occurs in the winter and spring months, in animals that have developed their adult worm immunity, and is most evident in mature ewes or wethers. In south-east Australia scouring occurs in a large proportion of some flocks (30–40%) every year, and may last for 3–4 months. In Mediterranean climatic zones, hypersensitivity scouring usually occurs after the relatively worm-free period of summer and autumn, after sheep are re-exposed to worm larvae. The occurrence between flocks and years varies considerably, and it generally lasts for only 4–6 weeks in a particular flock.
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).
Barber’s pole worm is most commonly found in Queensland and the northern half of NSW where summer rainfall is common or dominant. This worm is less of a problem in the winter rainfall areas of Australia, but localised pockets exist in all states and infections are worse in summers that are wetter than usual.
Black scour worms occur in all sheep production districts of Australia. Trichostrongylus colubriformis and Trichostrongylus vitrinus are the main species causing disease in Australia. Generally, T. colubriformis occurs in the warmer summer rainfall areas and T. vitrinus occurs more frequently in winter rainfall areas.
T. vitrinus is considerably more pathogenic than T. colubriformis, meaning that it needs to be treated at lower egg counts. Regular worm egg counts are essential for successful management.
While tapeworms are large and the segments passing in the dung are very obvious, there is no consistent evidence that they cause production loss or ill-health. Therefore, treatment for tapeworms is not warranted.
Intestinal tapeworms (Moniezia) are blamed for a range of sheep problems, but there is no hard evidence for any effects on production or health. Treating specifically for intestinal tapeworm is unlikely to be beneficial, whether in terms of scouring or weight gains. It is more important to effectively treat the less visible worms (the important sheep roundworms), which can cause severe production losses and death.
The most important treatment is carried out in April–May and should be based on the flukicide, triclabendazole, which is effective against all stages of the fluke found in the sheep. If treatments are also required in August–September and/or February, one or both of these treatments should be a flukicide other than triclabendazole (if this was used in April). This treatment rotation will reduce the rate of development of fluke resistant to triclabendazole.
Links to the learning topics for NSW Non-Seasonal Rainfall