Identifying challenges and opportunities for sustainable parasite control in Thoroughbreds


Drug (anthelmintic) resistance, in the parasites known as cyathostomins, poses a serious threat to the health and welfare of all horses, especially youngstock.  Whilst resistance to the other drug classes has become widespread in cyathostomin populations, the macrocyclic lactone anthelmintics (e.g ivermectin and moxidectin) have remained largely effective. However, the first case of ivermectin/moxidectin resistant cyathostomins was reported recently on a UK Thoroughbred stud, following similar reports in the US/Ireland, and in Australia. These reports of drug resistance are in young animals, at higher risk of parasite associated disease and often subjected to intensive anthelmintic use. The fact that ivermectin/moxidectin resistance have all occurred on studs, suggests that there may be predisposing management factors. Understanding the emergence of resistance and factors that mitigate its spread is vital as there are no new anthelmintics in development. The best way to achieve effective parasite control is to reduce reliance on drugs and encourage adoption of sustainable control practices.

Horses acquire cyathostomin infection when grazing pastures contaminated with infective larvae. We know that interventions that reduce pasture infectivity represent an opportunity for non-drug-based parasite control. For example, twice weekly removal of faecal matter reduces pasture contamination, resulting in lower egg shedding by horses and the need for fewer anthelmintic treatments. Similarly, co-grazing with ruminants can reduce pasture infectivity and group rotation of grazing horses on different pastures reduces infection prevalence. The recent case of UK ivermectin/moxidectin resistance in successive cohorts of yearlings (2021 and 2022 foals) highlighted that permanent pasture grazed by youngstock for several years prior raises the risk of infection of young horses with drug-resistant parasites. Targeted drug treatment of horses based on diagnostic tests has been widely promoted, to reduce excessive anthelmintic use. However, behaviour change has been slow, many anthelmintic treatments are still administered in the absence of diagnostic indicators and changes in attitudes are not occurring rapidly enough.

This project integrates parasitology, social and veterinary science to deliver impactful, evidence-based strategies specific for sustainable parasite control. The project will use a mixed methods approach to explore grazing practices and patterns of anthelmintic use on studs and training yards, and identify the behavioural drivers, beliefs, and barriers around parasite management. Using behaviour change science approaches such as systems mapping, we will identify the impact of different stakeholders and influences on behaviour, elucidating key “touchpoints” and opportunities for bringing about behaviour change. This will be delivered through several objectives: 1) identify current anthelmintic use and pasture management, 2) explore stakeholder pressures, and influences on parasite control measures, 3) conduct faecal egg count reduction tests (FECRT) on stud farms and 4) capture participants’ response to, and decision-making around receiving FECRT results. By working directly with stakeholders, challenges, and opportunities specific to their enterprises will be identified, prompting more sustainable means of parasite control, and optimising the health and welfare of Thoroughbreds and the wider horse population.

The student will gain expertise in a range of generic career and research skills as well as specific skills, particularly focused on qualitative and parasitology skills.

To apply please send a CV and cover letter to

For application enquires please contact Prof Jane Hodgkinson,



Open to UK applicants

Funding information

Funded studentship

This studentship would be suitable for a UK graduate with a veterinary science or related biological science or social science degree. Prior experience of qualitative research is not essential but aptitude and desire to develop deeper skills in this area is essential.   The student will liaise with equine enterprises and veterinarians so good communication skills are essential. This studentship is generously funded for a period of 4 years by the Horserace Betting Levy Board and includes a tax-free stipend of £23,400 per-annum, enhanced to £29,000 for a veterinary graduate. All research expenses and fees are included.  



Bull KE, Allen KJ, Hodgkinson JE, Peachey LE. The first report of macrocyclic lactone resistant cyathostomins in the UK. Int J Parasitol Drugs Drug Resist. 2023 Apr;21:125-130. doi: 10.1016/j.ijpddr.2023.03.001. Epub 2023 Mar 7. PMID: 36940551; PMCID: PMC10036890.