The product you choose to treat ticks on cattle depends on the following factors:
1. Tick species
Treatment for 1-host ticks (cattle tick) are very different from those used for multi-host ticks (paralysis tick, bush tick), so it is important to understand which species is the target for control. Product labels should be checked to ensure that the product is effective at killing the target species.
2. Impact on other parasites
The spectrum of activity of chemical products varies widely. For instance, amitraz has a narrow spectrum, killing ticks while having no impact even on other external parasites, whereas synthetic pyrethroids (SP) have a medium spectrum, providing control of a range of external parasites, and macrocyclic lactones (ML) have a broad spectrum, killing internal parasites such as roundworms as well as external parasites. Consider other parasites when choosing products. Where possible, choose a product to address only the parasites of concern at the time of treatment to reduce the risk of resistance developing from unnecessary overtreatment of non-target species.
3. Chemical resistance
Acaricide resistance is common and widespread in Australia. Resistance has been reported to all chemical classes used to control ticks. Where resistance is suspected, a sample of ticks should be tested to determine the resistance profile of the tick population. A chemical should not be used where resistance to that chemical class has been detected.
4. Speed of activity
Some chemical acaricides (e.g. amitraz) are contact poisons that act immediately whereas others (e.g. macrocyclic lactones) act systemically and require the ticks to take blood meals to acquire a lethal dose, meaning it may take up to a week for all of the ticks to be killed. Other products (e.g. fluazuron) are development inhibitors that provide control by preventing the ticks from moulting and ticks may survive several weeks after treatment. The required speed of activity must be taken into account when choosing a product. For instance, if clearing cattle of ticks immediately prior to sending them to a saleyard or when needing to knock paralysis ticks off calves, a fast acting product must be used.
5. Short vs long acting products
While some products (e.g. amitraz) provide no persistent activity, other products (e.g. fluazuron, long-acting macrocyclic lactones and chemical eartags) can provide ongoing control for many weeks. In general it is best to use long-acting products where there is ongoing high tick pressure or in high risk situations (e.g. young calves exposed to paralysis ticks). Indiscriminate use of long-acting products can increase the risk of developing resistance through unnecessary exposure of tick populations to a particular class of chemical.
6. Withholding periods (WHP), export slaughter interval (ESI) and retreatment intervals
It is essential to choose a product with appropriate withholding periods (WHP) and export slaughter interval (ESI) according to the time left before the animals go to slaughter or their milk is used for human consumption. Retreatment intervals may be important where frequent application of a product is required to ensure ongoing protection in high risk situations (e.g. calves exposed to paralysis ticks). Consult the APVMA website.
For help in selecting a product to treat ticks see the TickBoss cattle products search guide.