A study has revealed a growing trend in the proportion of positive faecal worm counts (FWECs) among horses in the UK.
Research which analysed quarterly surveillance data summaries of FWEC test results that were submitted to the Equine Quarterly Disease Surveillance report (EQDSR) by 36 UK laboratories over a period of 17 years between 2007 and 2023 displayed an increasing trend in positive FWECs.
The study, which is entitled Reasons to be fearful? Rising proportions of positive faecal worm egg counts among UK horses (2007–2023), was carried out by The Equine Infectious Disease Surveillance (EIDS) group based at the University of Cambridge, in collaboration with Animal Health Vision International, the University of Liverpool and jDATA Pty (Ltd) and has been published in the Equine Veterinary Journal.
“Analysis revealed an increase in the proportion of positive FWECs over time, even after accounting for the time of year that testing was conducted, the FWEC positivity threshold used for reporting a sample as positive and the laboratory undertaking the testing,” said a statement from the EIDS group.
Of the 36 UK laboratories who contributed data to the investigation, 18 provided additional details through a survey on the testing methods adopted. A variety of testing methods and positivity thresholds were used across the laboratories.
Questions raised
“These findings raise questions about targeted treatment strategies, where anthelmintics are administered if FWECs exceed a certain threshold,” continued the statement.
“If this threshold remains low, the increasing proportion of positive FWECs that we identified would lead to increased use of wormers, potentially accelerating the development of anthelmintic resistance.
“This highlights the need to better understand the factors driving rising FWEC positivity rates and if they are a cause for concern.”
The data obtained was unable to capture certain background information like the age of the horse and their prior anthelmintic treatment history and worm risk. Also, as the results are only categorised as positive or negative, it is not known the exact eggs per gram count for each FWEC test result.
The EIDS group, which is dedicated to monitoring and researching infectious diseases affecting equine populations, will look for ways to enhance data collection methods to be able to obtain this information.
‘Remarkable achievements’
“This paper highlights the remarkable achievements of two decades of sustained surveillance efforts, showcasing how data contributions and analysis can deepen our understanding and drive progress,” said lead author Fleur Whitlock MRCVS.
“It emphasises the critical importance of advancing the monitoring and interpretation of surveillance data to better address industry challenges, such as the growing concerns around anthelmintic resistance.”
The study is available to read for free in the Equine Veterinary Journal.
