Scientists uncover mode of resistance in cattle ticks

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Researchers at the University of Glasgow have identified the genetic basis for at least one form of pesticide resistance in the cattle tick Rhipicephalus microplus, an important parasite of cattle in the tropics and subtropics. Populations of these ticks have developed resistance to Amitraz, a widely used acaricide for controlling the pests, which cause anaemia, reduced rate of growth and death.

According to an article from, about 80 percent of cattle around the world, mostly in the tropics and sub-tropics, are exposed to the cattle tick, with a global cost of tick-borne diseases and control measures estimated to be more than $6 billion annually.

Resistance to acaricides is found in about 20 percent of Australian tick populations and more than 50 percent of Mexican ticks.

In their report, published in the Proceedings of the National Academy of Sciences, the researchers describe in detail the evolution of amitraz resistance in replicated populations of ticks in the field, using divergent selection pressures with amitraz.

They also demonstrate a close association between resistance to amitraz and a specific allele of the β-adrenergic octopamine receptor gene, which they propose confers resistance to amitraz.

The researchers established six populations of R. microplus ticks in similar paddocks, using strains of ticks known to be susceptible and resistant to amitraz and synthetic pyrethroids. They managed each population using one of three acaricide treatment regimes: always amitraz, always spinosad, or rotation between amitraz and spinosad.

Using DNA testing, they found that treatment witn amitraz increased the frequency of a particular gene mutation while increasing the prevalence of amitraz-resistance. They conclude that polymorphisms in the RmβAOR gene are likely to confer resistance to amitraz.

This research could lead to new genetic tests for resistance to assist farmers in making tick-control decisions. Better understanding of the mode of resistance also could enable empirical studies on field and laboratory populations of ticks to test the effectiveness of resistance management strategies, according to the article.

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Wyo  |  October, 10, 2013 at 07:50 AM

As Johann Zietsman says......... "The only lasting solution is dependent on the breeding of parasite resistant cattle and not poison resistant parasites."

Reno, NV  |  October, 10, 2013 at 09:29 AM

Good luck.

Wyo  |  October, 10, 2013 at 12:39 PM

Thanks Doc........not sure Johann needs any good he has already done it.

Australia  |  October, 11, 2013 at 08:38 AM

There are currently several natural or botanically-based insecticides/acaricides that can be used against ticks. Because they are natural acaricides with very complex molecular structures, ticks and other bugs have never mounted resistance against them. Here in Australia, in Tasmania, we grow acres of pyrethrum plants where natural pyrethrins are extracted from. Why keep on using amitraz? Why keep on banging your head on concrete? Look for new and effective products!

Jane Gerard    
AL.USA  |  October, 12, 2013 at 07:39 AM

Why not have bird/fowl ( I use Guinea fowl and turkey) they follow my herd neatly cleaning up the parasites. Use one species to help with another, cheaper than chemicals and helps fertilise the soil too! Chemicals always run the risk of wiping out other species that keep the insects and parasites under control, this is not new information but we are experiencing the results of use over decades, when ticks become chemical resistant you have to stop and think.

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