Fasciola hepatica in UK horses

Abstract

Summary Background Fasciola hepatica (liver fluke) affects grazing animals including horses but the extent to which it affects UK horses is unknown. Objectives To define how liver fluke affects the UK horse population. Study design Descriptive, cross‐sectional, observational study. Methods An F. hepatica excretory‐secretory antibody detection ELISA with a diagnostic sensitivity of 71% and specificity of 97% was validated and used to analyse serum samples. An abattoir study was performed to determine prevalence. A case‐control study of 269 horses compared fluke exposure between horses with liver disease and controls. Data on clinical signs and blood test results were collected for sero‐positive horses. Genotyping of adult fluke was used to produce a multilocus genotype for each parasite. Results Four (2.2%) of 183 horses registered in the UK, sampled in the abattoir, had adult flukes in the liver, and the sero‐prevalence of F. hepatica was estimated as 8.7%. In the case‐control study, horses showing signs consistent with liver disease had significantly higher odds of testing positive for F. hepatica on ELISA than control horses. In 23 sero‐positive horses, a range of non‐specific clinical signs and blood test abnormalities was reported, with a third of the horses showing no signs. Genotypic analysis of liver flukes from horses provided evidence that these came from the same population as flukes from sheep and cattle. Main limitations Bias could have arisen in the prevalence and case‐control studies due to convenience sampling methods, in particular the geographic origin of the horses. Only a small number of horses tested positive so the data on clinical signs are limited. Conclusions Exposure to liver fluke occurs frequently in horses and may be an under‐recognised cause of liver disease. Flukes isolated from horses are from the same population as those found in ruminants. When designing and implementing parasite control plans, fluke should be considered, and horses should be tested if appropriate.

Parasitic diseases of equids in Iran (1931–2020): a literature review

“…Horses and donkeys can acquire infection with both Fasciola hepatica and F. gigantica in their liver [ 210 , 211 ]. Infected horses with liver flukes show clinical signs including poor performance, fatigue, diarrhea, inappetence and jaundice [ 212 ]. Very recently failure to establish infection of horses after oral challenge with metacercariae raised fundamental questions on the pathophysiology and epidemiology of equine fasciolosis [ 213 ].…”

Equines as reservoirs of human fascioliasis: transmission capacity, epidemiology and pathogenicity inFasciola hepatica-infected mules

“…The strongly increased values of GGT, AST and ALP indicate pronounced liver function alterations, as reported in other animal species (Valero et al ., 2016), including horses (Montes et al ., 1984; Soule et al ., 1989; Howell et al ., 2020). Furthermore, an increase in creatinine suggests alterations in protein metabolism, and the increase of the CPK enzyme may underlie potential effects as endocrine disorders, heart damage and skeletal muscle disease.…”

“…In this Bolivian hyperendemic area, donkeys are considered one of the four important reservoir species. Interestingly, horses from the UK do not appear to be ‘high’ egg excretors (Howell et al, 2020).…”

“…A review of the countries in which natural infection of horses has been reported was made in 1988 in a report from South Africa (Alves et al ., 1988). Additional findings in horses include countries as different as Italy (Galli-Valerio, 1893), Ireland (Quigley et al ., 2017), the UK (Howell et al ., 2020), Egypt (Haridy et al ., 2002), Chile (Alcaino & Aguilar, 1985; Alcaino et al ., 1988, 1990, 1992), Uruguay (Sanchis Polto et al ., 2014; Bargues et al ., 2017), Argentina (Mera y Sierra et al ., 2009) and Australia (Bucknell et al ., 1995). Infected racehorses have also been the focus of research, as in Europe (Krawiecki, 1986) and Chile (Alcaino et al ., 1983, 2005; Montes et al ., 1984; Muñoz et al ., 2008).…”

Update on liver fluke in sheep

“…Sheep and cattle are the main hosts in the UK, but deer, rabbits, hares and horses can also be infected. F hepatica are genetically heterogeneous and recent findings suggest that F hepatica in sheep, cattle and horses are drawn from the same population and imply that anthelmintic resistance genes can flow rapidly through F hepatica populations (Beesley and others 2017b, Howell and others 2019).…”