Use of a saliva-based diagnostic test to identify tapeworm infection in horses in the UK

Background: Anthelmintic resistance combined with limited chemotherapeutic options has prompted a change in approaches to control of equine helminth infections. Targeted selective treatment strategies use diagnostics to reduce anthelmintic use by treating individuals with worm burdens or egg shedding levels above a set threshold. While faecal egg count analysis has limitations for informing tapeworm treatment, a commercially available saliva-based diagnostic test accurately diagnoses horses with tapeworm infection. Objectives: Evaluation of a saliva-based diagnostic test to identify horses naturally infected with tapeworm and assess the impact of using the test to inform anthelmintic administration. Study design: Retrospective longitudinal study. Methods: Saliva was collected from horses (n = 237) at a UK welfare charity from autumn 2015 to autumn 2016. Horses diagnosed as positive for tapeworm infection using the EquiSal^® Tapeworm test were anthelmintic treated according to weight. The number of horses that received anthelmintic treatment based on the test result was compared with an all-group treatment approach and the reduction in anthelmintic usage calculated. Incoming horses were also tested (n = 143) and the information was used to inform quarantine treatments. Results: In autumn 2015, 85% of 237 horses tested received no anthelmintic and the majority (71%) of these remained below the treatment threshold throughout the study. Of the 69 horses that received treatment, seven required treatment following three subsequent tests, while >50% of horses administered with anthelmintic fell below the treatment threshold at the following test. No increase in tapeworm prevalence within the 237 horses was observed during the study despite a substantial reduction in the application of antitapeworm treatments. A total of 41% of incoming horses required anticestode treatment. Main limitations: Other management practices were not included in the analysis. Conclusions: Compared with an all-group treatment strategy, the diagnostic-led approach used here considerably reduced application of anticestode anthelmintics. This could reduce selection pressure for anthelmintic resistance.