Industry intervention integral to tackling escalating dewormer resistance

The results of more than four years of research, funded through the AgriFutures Thoroughbred Horse Program, indicate resistance in intestinal parasites to commonly used dewormers is widespread across all major thoroughbred breeding regions. Tests carried out on more than 3,400 faecal samples from 78 thoroughbred breeding operations across Australia have revealed high worm burdens, especially in younger horses, and that the resistance is escalating.

Dewormer resistance is a serious threat to horse health and one that impacts the entire thoroughbred community. Research results indicate that – on the current trajectory – it may only be a few years until we have multi-resistant strains of parasites. In addition, there are no new dewormers in development. On pastures that harbour resistant parasites, the only way to keep burdens low enough to manage the risk of parasitic disease will be to vastly reduce stocking densities, which will in turn impact the economic viability of many commercial equine operations.

The AgriFutures Thoroughbred Horses Program is turning to industry to drive research to stop resistance in its tracks.

Evidence builds case for intervention

Research carried out from 2018–2022 by Prof. Abdul Jabbar and his team from The University of Melbourne and funded by the AgriFutures Thoroughbred Horses Program aimed to build a clear picture of intestinal worm burdens of thoroughbred horses across Australia.

“Prior to this project, there was a significant gap in our understanding of the intestinal worms that affect the health, performance and welfare of thoroughbred horses across Australia,” Prof. Jabbar said.

“And the true extent of resistance in these worms to commonly used dewormers was unknown.”

The project aimed to determine the types of intestinal worms affecting thoroughbred horses across Australia, assess current worm control practices, and understand the level of resistance to dewormers.

Current strategies are escalating resistance

According to Prof. Jabbar, more than three-quarters of breeders surveyed as part of the project were unaware of dewormer resistance on their properties.

“Most breeders surveyed are still controlling worms in their horses using an ‘interval-based’ deworming approach and not basing their administrations on faecal egg count (FEC) results. Few breeders carry out tests to assess the efficacy of the products they are using.”

“This commonly used strategy is not only ineffective, it’s also contributing to escalating resistance to available dewormers,” he noted.

“We found extensive resistance to common dewormers in 37 of 86 trials, where we tested a subsample of more than 2,200 faecal samples across 22 thoroughbred farms.”

Industry to drive future research direction

On the back of the results, the AgriFutures Thoroughbred Horses Program is ready for their next investment into tackling worm resistance.

Program Manager, Annelies McGaw says industry is integral in driving this investment.

“We want Australia’s thoroughbred breeders to lead us in a direction that best meets their needs when it comes to worm management,” she said.

“The research so far has given us a clear picture of what is happening on the ground with regards to worm resistance, but we know worms are just one part of a much larger, complex landscape for thoroughbred breeders.

“We want to understand where worm management fits within breeders’ overall management program and priorities, and how we can best target our next investment to support practical and effective control strategies.”

Your opportunity to contribute

Catriona Nicholls from Hot Tin Roof Communications, on behalf of the AgriFutures Thoroughbred Horse Program, is interviewing key industry stakeholders during June 2023 to better understand their key concerns, priorities and approaches to worm management.

From these interviews, Cat will deliver recommendations which will help drive the direction of future research into worm control in your industry.

To take part in an interview, email Cat at or Click here to complete a three-minute confidential survey.