Introduction: This report highlights the need to consider liver fluke as a differential for liver disease in the donkey and the need for correct faecal sampling and treatment.
History and Clinical signs: An 11 year old donkey gelding was referred to investigate ongoing weight loss, elevated liver enzymes, hypoalbuminemia and eosinophilia. The donkey had received treatment for suspected colitis with moxidectin and prednisolone. The feed had been increased and dental correction performed as necessary. A routine strongyle faecal egg count had 0 epg. 1 week prior to referral, the donkey had developed pyrexia and dullness, which responded to Flunixin.
Examination and Diagnostic findings: The donkey was in BCS 2 /5. T 38, HR 64, RR 20, gut sounds and rectal examination were unremarkable. A routine oral glucose absorption test was normal. The only significant finding on ultrasound examination of the abdomen were changes in the liver parenchyma; large numbers of abnormally dilated bile ducts and blood vessels disrupted the liver architecture. A liver biopsy was not performed due to concerns about the risk of penetrating a vessel.
A full examination of the donkey’s parasite history revealed that there was an episode of liver fluke (Fasciola hepatica) noted 1 year prior to referral that had been treated with Triclabendazole at 18mg/kg oral. Subsequent tests had given two negative faecal egg tests for fluke at intervals of 16 and 35 days.
A repeat faecal examination was performed testing for liver fluke, which proved positive at the time of examination.
Treatment plan: Treatment was initiated with Closantel orally at 20mg/kg repeated after 8 weeks. A balanced diet supplemented by a vitamin /mineral supplement was provided.
Outcome: Subsequent faecal tests for fluke over the following 1 year have remained negative. Liver values and haematology returned to normal within 15 days. A repeat Ultrasound examination after 3 months showed the vasculature returned to normal size and the parenchyma appeared to be grossly normal. The donkey gained 23 kg in weight over the following 48 days and was scored at BCS 3/5.
Discussion: Fasciola hepatica (Liver fluke) infection is recognised in horses and donkeys, but few reports detail individual cases. The infection prevalence in UK donkeys based on faecal analysis has been variably stated as 4-8% (Matthews and Burden, 2013), and 9% in a recent study of 596 donkeys (Barrio pers. comm 2019). Howell et al. 2019 described a sero-prevalance of Fasciola based on a horse specific ELISA at 8.7% in a survey of 183 UK horses.
Clinical signs and liver pathology are usually considered to be mild.
Fox et al. (2011) describe an increasing infection risk with liver fluke across the UK due to climate change resulting in wetter, warmer weather that encourages the survival and development of the free living stage of the parasite and intermediate snail host. Equines are at risk if they co graze pastures with ruminants that carry the parasite.
There are no licensed products for treatment of liver fluke in equines and there is reported resistance to some products. After treatment repeat sampling is required and a further flukicide treatment may be needed.
References:
Fox, N.J., White, P.C., McLean, C.J., Marion, G., Evans, A. and Hutchings M.R. (2011) Predicting impacts if climate change on Fasciola hepatica risk PLoSOne Jan 10; 6 (1) 0. e16126 doi.10.1371/journal.pone.0016126.
Howell, A.K., Malalana, F., Beesley, N.J., Hodgkinson, J.E., Rhodes, H., Sekiya, M., Archer, D., Clough, H.E., Gilmore, P., and Williams, D.J.L.( 2019) Fasciola hepatica in UK horses . Equine Vet J. https://doi.org/10.1111/evj.13149
Matthews, J.B. and Burden F.A (2013) Common helminth infections of donkeys and their control in temperate climates. Equine Vet. Educ 25 (9) 461-467