Strongyle faecal egg counts in Swiss horses: A retrospective analysis after the introduction of a selective treatment strategy

The standard parasite management of horses based on regular anthelmintic treatments, now practiced for decades has resulted in a worrying expansion of resistant helminth populations, which may considerably impair control on the farm level. The aim of the present study was to obtain a retrospective (year 2010 - 2016) nationwide analysis of faecal egg count (FEC) data from the Swiss adult horse population, related to horse age and geographic region. Thirteen labs provided a total of 16,387 FEC data of horses aged four to 39 years (average: 13.6 years). The annual number of performed FEC tests increased from 38 to 4,939 within the observation period. Independent of the annual sample size the yearly patterns of the FEC were very similar. Seventy-eight percent (n = 12,840) of the samples were negative and 90 % (n = 14,720) showed a FEC below 200 strongyle eggs per gram (EPG) of faeces. The annual mean strongyle FEC ranged between 60 and 88 EPG with a total mean of 75 EPG. Horses aged 4-7 years showed a significantly (p < 0.00001) higher mean FEC compared with the other age groups, differences were not significant among the older horses. Based on ZIP codes, samples were allocated by 70.0 %, 6.0 % and 0.2 % to the German-, French- and Italian-speaking regions of Switzerland, respectively. With 222 EPG the mean FEC in the French part of Switzerland was significantly higher (p < 0.05) than in the German-speaking region (60 EPG). Eggs of Parascaris spp., anoplocephalids and Strongyloides westeri were found in 0.36 %, 0.32 % and 0.01 % of the samples, respectively. Based on 3,813 questionnaire feedbacks from owners in 2017 covering a total of 12,689 horses, sixty-eight percent (n = 8,476) were dewormed without diagnosis, two percent (n = 240) were not dewormed at all, whereas for 30 % (n = 3,721) the selective anthelmintic treatment (SAT) concept was applied. The SAT implementation rate differed significantly (p < 0.0005) between regions, with 33 %, 20 % and 25 % for the German-, French- and Italian-speaking areas, respectively. The rate of horses spending 16-24 h on pasture per day was significantly higher in the French-speaking region compared to the German-speaking part of Switzerland (p < 0.0001). In addition, pasture hygiene was practiced at a significantly lower rate in the French-speaking part compared to the German- and Italian-speaking regions (both p < 0.0001). Overall, the shift towards the SAT-concept represents a very promising development with respect to mitigating the further spread of anthelmintic resistance.

The prevalence of equine odontoclastic tooth resorption and hypercementosis and the role of interincisal angulation in disease severity in a representative cohort of horses in Switzerland

INTRODUCTION

Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is an increasingly diagnosed degenerative dental disease in aged horses. The primary aim of this retrospective study was to determine the prevalence of EOTRH in horses admitted to the Equine Hospital, University of Zurich, for dental procedures from 2004 to 2017. A secondary goal was to measure and compare interincisal angles on two-dimensional radiographs of horses with EOTRH to determine whether the interincisal angle is associated with age and severity of the disease. Radiographs were assessed for the presence of lysis and/or hypercementosis, and the number and position of the teeth affected were determined. Each tooth was also evaluated using the modified classification system introduced by Rehrl et al. (2018), in which stage 0 indicates no radiographic abnormalities and stage 3 denotes severe abnormalities. The overall stage was defined by the tooth with the most severe lesions. The interincisal angle was determined in horses that had suitable radiographs. The medical records of 838 horses admitted for dental procedures were evaluated, and 85 (10,1 %) had clinical evidence of EOTRH. The mean interincisal angle was 136,06 ° in horses with mild to moderate EOTRH and 135,10 ° (SD = 11,90 °) in severely affected patients. In conclusion, the angle measurements on lateral radiographs were highly reproducible. However, the interincisal angle was not associated with age or the severity of EOTRH. The interincisal angle and the disease pattern were not correlated.