Aside from drenches at one or two strategic times the mob’s average worm egg count should be the basis for other drenching decisions.
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Checking a mob of sheep for worms with a WormTest
How-to guide to collect and submit samples for a mob worm test to a laboratory.
Worm egg counting
How worm egg counting is carried out.
Assessing worm burdens without a WormTest
Other ways to assess whether sheep have worms and what level of worms exist.
Collecting dung samples from individual sheep (optional)
How-to guide on collecting dung samples from individual sheep (for drench resistance tests or genetic assessment of worm resistance).
Worm testing for ram breeders (optional)
How-to guide for ram breeders who want to gain worm egg count or dag breeding values for individual sheep.
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Each of the questions below links further down the page to the answers.
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Answers:
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1. How many individuals should be sampled for a WormTest?
Collect the number of samples per mob as recommended by your laboratory (ideally this would be from at least 20 sheep—if you are doing your own worm egg count on farm, try the following ‘bulk collection’ method.
Bulk collection method
2. Name a standard time when you should WormTest.
WormTests can be done at any time, however there are also set times to WormTest (preferably with a larval culture in warm/wet times to check for barber’s pole worm):
WormTest more often in high rainfall years and less often in very dry years. However, when sheep congregate on smaller areas due to tall thick pastures, heavy rain/flooding or bore drains WormTest more often.
Check the intestines: Nodule worm can be a problem in this area; check for signs when any sheep die or are killed for rations. Open the sheep’s abdomen and find the large and small intestines. Examine the outside wall of each for firm white pimples or nodules. If these are present, you should routinely drench in May with a drench that contains either a macrocyclic lactone (ML) or a benzimidazole (BZ).
3. What 2 things does a larval culture tell you and how these help you make a drenching decision?
A WormTest refers to a ‘Worm Egg Count Test’ or ‘WEC test’; it will identify the number of worm eggs in faeces, which is a good indication of the worm burden of the sheep. Some laboratories can also perform a ‘Larval Culture’ (also called a ‘Larval Differentiation’) to identify the types of worms present and their proportion (the importance of this varies according to your location).
4. Name a situation when you would drench without a WormTest?
A) When giving a quarantine drench.
B) When giving a strategic drench. The timing of strategic drenches depends on the region and the class of sheep, as their use is closely associated with times when sheep are most susceptible to worms or when development of eggs to infective larvae on pasture is likely to be extremely low (to reduce pasture contamination) or high (to pre-empt likely immediate problems). Strategic drenches are given regardless of the average worm egg count of the mob.
There are six common strategic drenches; not all are used in every region. The WormBoss programs outline which strategic drenches to use in each region.
Details of when/how to use strategic drenches are in Your Program.
5. You can use the WormTest from one mob to make drenching decisions about similar mobs. For every mob you test how many other mobs could this represent?
Ideally each mob should be tested individually, as there are usually differences between paddocks in the favourability for worm survival, the number of worm eggs being deposited by different mobs, and the time since a drench was given. However, if there are a number of mobs that have the same drenching history, same class of sheep and very similar paddock type (including recent level of contamination from worms) then one mob can represent two others (i.e. test one in every three similar mobs).
Testing representative mobs saves the cost of testing all mobs, but carries the risk that the result may not be representative. If in doubt, test additional mobs. Testing individual mobs is suggested for Western Australia, South Australia, Victoria and Tasmania.
6. If only very few sheep (less than 2%) in a mob appear to be badly affected by worms: ? What could be a cause of this? What action would you take?
If less than 2% of a mob are showing signs that include pale inside eyelids and gums, bottle jaw, lagging or collapse, you should treat these affected sheep immediately with a drench suitable for barber's pole worm, but also sample and test the remainder of the mob now. If these signs are not visible, but a few sheep are scouring badly, test the mob now. In both cases, use the results with your Drench Decision Guide to decide whether the whole mob should be treated.
When less than 2% of a mob show signs of worms these are the possible causes:
In all of the above situations, a WormTest on the remainder of the mob (don't include these badly affected sheep) to determine the worm egg count will inform your decision of whether to treat the rest of the mob.
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