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Cattle Lice Active this Winter

As the weather becomes cooler and we head into winter we will see cattle lice populations become active. Louse activity and populations are the highest in the winter months and lowest in the summer months. This is due to the cooler weather, cooler skin temperatures and a denser winter coat favouring their survival.


There are many treatments for lice, however an Ivermectin based pour on tends to be the most effective on lice (both sucking and biting) with a repeat application within a 2-3 week period (providing there is no resistance to the active).

If worms are also of concern it is possible to treat with a number of other pour on or injectable products. However, when choosing an active and product (Pour on or Injectable) you must be aware of the parasite being treated i.e. Is it a biting or sucking louse? This will determine whether to use a pour on or injectable.


The reason it’s advised to re-treat within a 2-3 week period is because most insecticides registered for use on cattle are not very active against the louse eggs; a follow-up treatment 2–3 weeks post initial treatment is highly recommended to achieve control. This allows time for the eggs to hatch but not to mature into adults which will then lay eggs and repeat the cycle.


The life cycle of both the biting and sucking lice are very similar with eggs laid taking 8-19 days to hatch into nymphs. The nymphs then undergo three moults on the beasts before developing into adults with the entire life cycle taking between 3 and 6 weeks.

Eradication:  Assuming that there is no resistance to the chemical used, eradication of lice should be relatively simple providing the following is strictly adhered to:

1. Treat all cattle and ensure that you repeat the treatment according to the manufacturer’s instructions. 

2. Ensure that the dose rate is accurate. Preferably weigh all cattle and dose to the heaviest. 

3. Treat all cattle on the property at the same time (prior to calving where possible). Choose a time when they are not stressed or in poor condition.




If groups are treated separately, ensure that there is no contact possible between treated and untreated mobs. 

4. Immediately after treatment, move treated groups to a paddock that has not had cattle in it for at least a week. 

5. Ensure that no contact with neighbouring cattle is possible, either through straying or by contact across fences.   


Consider a treatment in autumn before louse numbers build up. This will allow a longer ‘test period’ of cold weather to follow the treatment allowing a better gauge on whether eradication has been successful.


For further enquiries or advice please feel free to contact the team at Western Ag Supplies.

Article produced by - Janette Densley, Western AG Naracoorte

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