What if we were no longer able to protect cattle from parasites?

Parasite control is essential to ensuring cattle well-being and health, as well as productivity. To date, parasiticides are still the most effective way to protect cattle from parasite infestations. But inappropriate use of such products can lead to resistance, making parasites much harder to control. This can be mitigated with judicious use, says Dr Chandra Bhushan, Veterinary Scientific Affairs Manager at Bayer Animal Health.


Parasites impact cattle well-being and health and pose a major challenge for cattle professionals across the world. Control programs may encompass a combination of non-chemical and chemical methods, but to date, chemical control products – parasiticides – are still our most effective defense against parasites.

But what is of growing concern is that key tick, fly and worm species are showing signs of resistance to major classes of parasiticides. This makes it much harder for producers to protect cattle from parasites, as well as the diseases they can transmit.  


Why is parasiticide resistance an issue?

A degree of resistance can be expected with the regular use of any type of chemical. Overuse or misuse of parasiticides can hasten this process, which is why it is vital to use parasiticides only as prescribed. With the development of resistance in tick populations, for example, this means that even when a parasiticide is used as prescribed, it is hard to achieve the desired control. This adds avoidable costs to cattle producers. But what is of greater concern is that these resistant tick populations will continue to thrive on the farm.

The annual cost of ticks and tick-borne diseases worldwide was estimated at US$14-19 billion in 1997.1 Today, the inflation-adjusted cost would be estimated at US$ 22-30 billion.2  Considering that more than 75 percent of the world’s cattle are raised in tick-infested areas and as such are exposed to important ticks and tick-borne diseases, resistance to parasiticides presents a big challenge.

In some parts of the world, resistance is a significant problem. For example, in a large part of Latin America, including Mexico and Brazil, ticks are getting harder to control because a sizable part of the tick population has developed resistance to one or more parasiticide chemical classes available. This means that for cattle producers to be able to protect their cattle from tick infestations, the tick resistance profile should be tested so that they can choose the right parasiticide.  

Parasiticide resistance has clear implications on animal well-being and production. Ticks, for example, feed on the blood of cattle, which is distressing for the animal. In addition to being an animal welfare challenge, tick infestations have also been linked with reduced feed intake in cattle, which in turn leads to reduced weight gain or even weight loss. Ticks can also carry and transmit serious diseases, such as anaplasmosis, babesiosis, theileriosis and cowdriosis, that can compromise animal health or even kill cattle. In short, parasites can have major economic impact on producers.


Judicious use of parasiticides is essential

Novel chemicals would certainly be welcome in the global fight against parasites. Veterinary pharmaceutical companies, including Bayer Animal Health, are actively conducting research and development in this area, but it takes time and substantial investments.

In the meantime, judicious use is vital to preserving the efficacy of the parasiticides that are on the market – this can help mitigate the development of parasite resistance across most parts of the world. This means that cattle professionals should always ensure the right parasiticide is used in the proper dose, at the appropriate time, and that it is applied properly. Proper rotation of parasiticides is also essential.


What does proper parasiticide rotation look like?

If one were to consider the many tick control product brands on the market, for example, one could easily think that parasiticide rotation is a simple matter. However, this is far from reality, as most tick control product brands belong to one of several main chemical classes such as amidines, organophosphates, phenypyrazoles, synthetic pyrethroids and macrocyclic lactones.

The most important thing to understand about proper parasiticide rotation is that it must involve switching chemical classes. Merely changing formulation or application method does not count as rotation if the parasiticide is still from the same chemical class.

So regardless of brand or application method as a pour-on, eartag or dustbag, a good tick control program should involve switching parasiticides from the amidine, organophosphate, synthetic pyrethroid, phenypyrazole or macrocyclic lactone classes – in whatever order, depending on what’s available in the respective country.


Bayer Animal Health field representatives are trained to help cattle professionals with best practices and customized parasite control programs to meet farm-specific needs. We also recently introduced ParaSight app in the US, a digital information resource to aid producers in their efforts to combat parasite infestations effectively and sustainably.

For us at Bayer Animal Health, the quest to discover and develop new parasite control solutions for the benefit of animals and their keepers, continues. In the meantime, we can all help protect and preserve the effectiveness of parasiticides for the future by ensuring that these important products are always used judiciously, in the interest of animal well-being and health.


1 de Castro JJ. Sustainable tick and tickborne disease control in livestock improvement in developing countries. Vet Parasitol. 1997;71(2-3):77-97.
2 Estimated cost calculated with https://www.calculator.net/inflation-calculator.html