Prevalence and associated risk factors of trematode infections in equids from selected practices in Gauteng, South Africa

Abstract

Reasons for performing study: Prevalence of infection with Gastrodiscus aegyptiacus and Fasciola hepatica has not been established in equids presenting with the relevant clinical signs. Various environmental and management practices with regards to equid husbandry are hypothesised to place equids at greater risk of infection, but no link has been established. There are currently two testing techniques for patent gastrodiscosis in equids, however the difference in accuracy between the tests has not yet been established. Objectives: To determine the prevalence of patent gastrodiscosis and fasciolosis in equids presenting with clinical signs of infection, to determine the difference in sensitivity and specificity between the two currently available testing techniques and to establish which management and environmental factors place equids at a greater risk of infection. Study design: Analytical cross-sectional study design. Methods: Samples were obtained from equids presenting to the Equine Clinic of the Onderstepoort Veterinary Academic Hospital, as well as three equine private practices in the Gauteng region (Fourways Equine Clinic, Glen Austin Equine Clinic and Pierre van Ryneveld Large Animal Clinic) and these samples were categorised according to their reason for seeking veterinary care, namely: 1) equids presenting with a gastrointestinal complaint, namely chronic weight loss and/or diarrhoea and/or recurrent colic, 2) equids presenting for elective procedures and/or non-gastrointestinal reasons Two fresh faecal balls were collected from each equid and each sample underwent testing using both the Sedimentation after Benedek and the Visser-filtration techniques. A questionnaire was completed by the primary caretaker for each sampled equid, with questions relating to the equids management and environment in which they are kept. Results: The overall prevalence of infection with G. aegyptiacus was found to be 11.6%. The prevalence of horses which tested positive and showed clinical signs of gastrointestinal dysfunction was 8.9% whereas the prevalence of horses which tested positive and were healthy at the time of testing was 15.5%. The overall prevalence of infection with F. hepatica was found to be 4.3%. The prevalence of horses which tested positive and showed clinical signs of gastrointestinal dysfunction was 4.9% whereas the prevalence of horses which tested positive and were healthy at the time of testing was 3.6%. One horse had co-infection of both trematodes. No statistically significant difference in detection sensitivity was found between the sedimentation method compared to the filtration method. Access to a water body showed a greater risk of infection with gastrodiscosis, whilst extensive management and grazing had a greater risk for infection with fasciolosis. Exposure of horses to livestock was found to increase risk of infection of horses with gastrodiscosis. Previous treatment of a horse for gastrodiscosis, or treatment with a product containing activity against this specific trematode, had an increased risk of infection with fasciolosis. Conclusions: Testing for gastrodiscosis should not be restricted to horses showing signs of gastrointestinal dysfunction. The prevalence of fasciolosis infection in horses in South Africa may be underestimated. The use of either faecal testing technique (Visser filtration and sedimentation after Benedek) is acceptable for trematode egg detection. Furthermore, access to a water body has a greater risk of infection for gastrodiscosis whilst extensive management practices and previous treatment with an anthelmintic targeted against gastrodiscosis had a greater risk of infection for fasciolosis.