Tick-tock! Countdown to tick season!
It’s estimated that cattle ticks cost the Australian grazing industry $160 million annually in productivity losses and control. An average tick burden of 50 ticks per animal can reduce weight gain by 1.5kg or milk production by 13.5 litres every 30 days (1) . Cattle ticks are also a vector for the blood parasites that cause tick fever.
Cattle ticks prefer warm and wet conditions and with the milder winter this year, it could mean an early start to the tick season so it’s important to be prepared now. Cattle ticks are most active from September to February but eggs can start hatching from late July/early August if winter conditions are milder. Eggs can lay dormant for up to three months in pastures over winter. Once hatched, larvae climb to the top of pasture where they can survive for up to 6 months waiting to come into contact with a host. The higher and lusher the pasture, the easier it is for tick larvae to attach. Larvae attach and feed on a single host, and over a period of 3 weeks, phase through their growth cycle from larvae (5-6 days) to nymph (6-8 days) to adult (7-12 days). Engorged female ticks then drop from the host onto pasture and can lay up to 3,000 eggs before dying.
Chemical treatments options available: Chemical treatment options available for tick control differ in a number of aspects. The choice of chemical used depends on chemical class, resistance status, length of protection, application method, management practices and residue limits. Short acting chemicals include pour-on mectins, Amitraz dip, organophosphates and synthetic pyrethroids. Their effective period is approximately 18-21 days with a recommended treatment interval of 21 days. Medium acting chemicals include injectable methrins. These have a 28–30 day effective period with a treatment interval of 28 days. Medium to long-acting chemicals include Fluazuron with an effective period and treatment interval of 42 days. Long-acting chemicals include injectable moxidectin which has an effective period and treatment interval of 56 days.
It’s important to have a cattle tick management strategy in place before the season starts as unplanned or sporadic chemical treatments do not effectively reduce tick numbers. Management of cattle ticks takes a multi-pronged approach but integrating the following six strategies will increase any management plan’s effectiveness:
1. Treat early:
Treat early in spring to prevent a high summer surge in tick numbers. Early control keeps populations low so treat with a medium-long or long-acting product as eggs start to hatch in August-September. This will reduce the number of larvae and nymphs reaching adulthood and reproducing, leading to lower numbers in the following generations.
2. Monitor and treat appropriately during the season peak:
During the peak season of November to January, cattle should be monitored to ensure treatments are effective and to retreat when necessary. The most susceptible animals include calves, bulls and Bos taurus herds, including cross-bred animals. A shorter acting knockdown chemical can be applied once numbers reach the chosen treatment threshold if the spring preventative application has been missed and ticks are already in their adult phase. This is a reactive strategy where a treatment is applied every three weeks once ticks are present. Insect growth regulators are no longer effective at this point as the ticks have already completed their phases of moulting.
3. Treat in autumn to reduce pasture contamination:
Once autumn arrives, it may be prudent to treat cattle one final time to reduce the number of eggs being dropped on pasture for next season. Consider using a medium-long to long-acting product or a couple of short acting product applications to take you through to cooler weather.
4. Use treated cattle to ‘sweep’ paddocks of ticks to allow grazing for more susceptible animals:
Cattle that have been treated with a long-acting treatment can be used to graze tick infested pastures to reduce tick numbers. The pasture is then considered lower risk for more susceptible animals to graze afterwards.
5. Vaccinate to protect susceptible animals:
Newborn calves are at a higher risk of serious illness or death from ticks and as such, it’s best to avoid calving when ticks are most active. Vaccinating calves with tick fever vaccine when they are 3-9 months of age will aid in their immunity development, protecting the animal against tick fever for life.
6. Utilise non-chemical strategies to reduce the frequency of chemical treatments:
Genetics is a management tool that can be used in any tick control program. Increasing the amount of Bos indicus (i.e. Brahman) genetics in your herd will provide inherited natural immunity and increased tolerance to cattle ticks and tick fever.
In addition, pasture management strategies can provide multiple opportunities to reduce tick numbers. Long term spelling can significantly reduce tick numbers as female ticks needs to feed in order to reproduce. In winter, a 5-month spell is required while in summer, 3 months spelling is adequate.
(1) Jonsson, N. N., Mayer, D. G., Matschoss, A. L., Green, P. E., & Ansell, J. (1998). Production effects of cattle tick (Boophilus microplus) infestation of high yielding dairy cows. Veterinary parasitology, 78(1), 65-77.
(2) NSW Department of Primary Industries. April 2020. Primefact: Cattle Tick. Animal Biosecurity and Welfare, NSW DPI.
THERE IS MORE TO THIS STORY!
This is an extract from the full article that was published in the Spring 2023 issue of Farmacist News. To read the full article, download the printable version using the link below: