Checking a mob of sheep for worms with a WormTest
What is a WormTest?
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).
Use the WormTest results to assist your decisions on:
- whether sheep should be drenched
- what drench group should be used
- when to conduct another WormTest
WormTest kits can be supplied by a number of laboratories and veterinarians and these may have different names and contents. Each WormTest kit is for one mob only. Some laboratories do not supply kits but describe how you should collect, store and send your samples to them. Always follow the procedure described by the testing laboratory that you will use.
Note: The worm egg counting process can be carried out on farm, but is not explained here. Workshops teaching how to do worm egg counts may be offered in your state. Larval cultures are almost only done in a laboratory.
How many mobs need to be tested and how often?
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.
Should I test a mob if a few appear to be affected by worms?
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:
- These sheep were not drenched when the rest of the mob were (e.g. didn't get mustered, were missed or spat out the drench in the race, strayed in from another mob). Their worm egg count may be a lot higher than the rest of the mob.
- These sheep are suffering from some other illness or injury that has reduced their immunity and they have acquired a larger worm burden than the rest of the mob. Signs of another problem may be evident.
- These sheep are the most susceptible in the mob because of lower worm-resistance and the mob has been tested just when these first sheep are starting to show signs.
- These sheep are not actually affected by worms at all. Instead, anaemia could be the result of liver fluke and scouring could be from larval hypersensitivity, coccidiosis or excess lush feed.
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.
What equipment is required?
WormTest kits (of the type supplied or recommended by your testing laboratory, or your own equipment)
How is a WormTest conducted?
1. Obtain a WormTest kit from your preferred supplier
2. Decide when to collect the samples
- If samples are to be posted or couriered, collect them in time to send from Sunday through Wednesday so that samples are not held in the post over the weekend.
3. Collect dung from fresh piles of dung
- Ideally, choose a time when the mob is camped or grazing close together.
- Approach the mob just close enough that they are alerted and they either stand or run only a short distance into a close group. Alternatively, muster sheep into a group or to a corner or fence line and hold them there.
- After a few minutes (longer if the mob is small or if they have been mustered), slowly approach the mob so that they walk away (running sheep will trample the dung piles).
- Ensure the dung is fresh—it should be both moist and warm.
- Choose dung with the least amount of dirt and debri attached and collect from a separate pile of dung for each bag/bottle or tray compartment.
- Very soft or runny dung can be collected with a plastic spoon (into bottles or trays) or if bags are used, insert your hand in the bag, grasp the dung through the bag and then invert the bag around the dung.
- If some piles are pellets and some are soft, collect a proportionate amount of both.
- If lambs are still with ewes, collect lamb and/or ewe samples separately for separate tests.
- 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 ‘bulk collection’ method described at the end of this note).
4. Complete the submission form
- If a larval culture is an option, ensure it is requested when the average worm egg count is 200 eggs per gram or above in areas where barber’s pole worm is a concern.
5. Pack the samples
- Exclude as much air as possible from samples if they are in plastic bags.
- Pack the samples as instructed on the kit, a freezer brick may need to be included if suggested by your laboratory.
- Complete and enclose the submission form and seal the kit.
6. Submit samples to the laboratory
- Keep samples in a cool place (e.g. in hot weather use an esky with a freezer brick), but not in the refrigerator, until they are delivered or collected for postage/couriering.
- Worm egg count results will generally be sent back within 24 hours of the laboratory receiving the samples.
- Larval culture results will be sent back in 7–10 days.
7. Use the results
- The results will indicate the average level of worm infection throughout the mob, expressed as the number of worm eggs per gram (epg) of dung.
- The larval culture will identify the types of worms present and the proportion of each type.
- The laboratory will generally provide recommendations with the results.
- In addition, use the WormBoss Drench Decision Guide* for your region in conjunction with your results to decide whether to drench; what drench group to use; and when to WormTest next.
Bulk collection method
When conducting your own worm egg counts on farm:
- Collect three pellets per adult pile (or the equivalent amount if soft or runny) or five for weaners.
- Collect from at least 20 dung piles.
- Where Haemonchus (barber’s pole worms) are an issue, and if the mob has over 200 sheep, collect from each of 40 dung piles.
- Collect all dung into one container
- The dung then needs to be mixed extremely thoroughly.
- Conduct your worm egg count using a sub-sample from the bulk mixture.
See the WormBoss Drench Decision Guides.