A study of the epidemiology of Anoplocephala perfoliata infection in horses and the oribatid mite vector in southern England.

Anoplocephala perfoliata is the most common equine tapeworm infection. This parasite is found at the small/large intestinal junction and has been associated with colic. The cestode has an indirect lifecycle involving oribatid mite intermediate hosts, though little is known of its epidemiology. This study aimed to monitor seasonal fluctuations in pasture oribatid mite numbers and the presence of Anoplocephala spp. DNA in mite samples collected from three equine premises in the UK. Exposure to infection in resident horses was assessed by measuring tapeworm-specific salivary antibodies. The data were analysed with management information to identify factors associated with the occurrence of (i) pasture samples containing different oribatid families, (ii) mite samples containing Anoplocephala spp. DNA, and (iii) a borderline or moderate high saliva score in the ELISA. Each yard was visited every four weeks (June 2016-August 2017) when three pastures were vacuum-sampled for mites. Three, one metre-square tetrads and grass surrounding 10 faecal pats were sampled per pasture. Mites collected were counted, identified to family level and pooled by family for Anoplocephala spp. DNA screening by polymerase chain reaction (PCR). Saliva samples were screened for A. perfoliata antibodies using the EquiSal® Tapeworm test in 10-23 horses at each yard every 2-3 weeks. Mixed-effects regression models were used to identify risk factors for each of the three outcomes. The results indicated that oribatid mite families not identified previously could act as intermediate hosts for Anoplocephala spp., and established that whilst oribatid mites might be found on pasture year-round, Damaeolidae and Oribatidae were 81 % (p = 0.005) and 64 % (p = 0.004) less likely to be detected in winter than in summer. Tapeworm-infected mites were more likely to be detected from March to September when more mites were recovered from paddocks, whilst saliva antibody test-positive horses were least likely to occur in autumn. Horses that grazed for half a day compared to those that grazed for full days were less likely to be positive in the saliva test. The findings yielded new insights into the epidemiology of equine tapeworm and its intermediate host in the UK, and contribute valuable information to support evidence-based control programmes for this parasite.