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Queensland worms, flies and lice update - November 2020

QLD WormBoss Worm Control Programs

QLD WormBoss Drench Decision Guides

Sheep

Goats

Sheep

Goats

Brisbane: Maxine Murphy, Veterinary Parasitologist (maxine@paraboss.com.au)

For the majority of the sheep production districts in southern Queensland, the lack of rain is still of concern. While year-to-date rainfall has been significantly higher this year compared to last, November has become very dry. For those regions lucky to have had some useful rain the ‘watch and act when necessary’ recommendation is still current; see the Drench Decision Guides for slopes and plains or tablelands and slopes. Worm egg counting should be once every four weeks over summer. While this month is dry, early December rains could spoil Christmas and New Year plans if worm monitoring is not already in place. Good worm management is about keeping ahead of the situation, and taking action before signs of infection become visible.

Currently, temperatures are soaring and the winds are carrying very little moisture. Worm eggs and larvae out on the paddock would be struggling to remain alive unless in a sheltered spot. Parasites accumulated in the host after the last storm rains will continue to drop eggs onto pastures. These will form the basis of a new population once rains fall. A few days of stormy and overcast weather greatly reduces the evaporation rate, leaving enough moisture for eggs to hatch and larvae to move out of the dung pellet.

Typically, lambs, kids and weaners are drenched in November. Adult sheep and goats are also drenched, but this year it would be wise to worm egg count (WEC or WormTest) the adults before drenching to confirm they are indeed wormy and in need of a drench.

Whether you do laboratory or on-farm testing, faecal samples collected for monitoring need to identify the worminess of individuals in the mob; otherwise, the information could result in not drenching the mob when drenching may indeed be necessary. 

We know that not all sheep in a mob carry the same worm burden, because many are genetically more resistant to worms than others (the basis of breeding for worm resistance). The tail of any mob of sheep will carry most of the worm burden (i.e. the 80/20 rule), whereas those animals at the top of the mob will always have a lower WEC under the same conditions. A wormy 20% of the mob will force the whole mob to be drenched.

Samples from at least 20 individuals provide a more accurate indication of the worm burden across a mob than 10 samples. For large mobs, where barber’s pole worm is a problem (can be a much wider variation in individual WEC), sampling from a higher number of animals (40 or more) is more accurate, especially in young sheep after good summer rains. 

Standard practise would be to collect faecal samples from the top group of sheep in any mob, and also from the wormy ‘tail’ group and perform WormTests on each of the two groups to give a range of the counts across the mob. This method also allows for the 20% tail group to be split off for drenching, and perhaps pastured elsewhere to reduce the overall worm burden of the original mob. 

Ideally, each mob should be tested individually, as there are usually differences between paddocks in terms of the favourability for worm survival, the number of worm eggs deposited, and the time since the last drench. When conditions are dry, testing one in every three very similar mobs (in terms of age, drenching history, paddocks etc.) may suffice, but the risk of missing a wormy mob remains.

Toowoomba: Peter Lynch, Veterinary Consultant, Livestock Veterinary Services (peterlynch@shwds.com.au)

Patchy storms have started to occur in pastoral areas of Queensland. We must remember that fresh green shoots mean that any eggs that have survived will be able to hatch and the larvae produced will have a good chance of survival. Barber’s pole worm numbers can increase rapidly. You need to start doing egg counts four weeks after rain and then continue to repeat them if you do not need to drench now.

If you need to drench, remember to use a drench with at least two active ingredients.

 

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