Atypical myopathy in the south east of England: clinicopathological data and outcome in hospitalised horses
Within the UK, differences in case numbers of atypical myopathy (AM) and survival rates are present in different locations. Dunkel et al (Equine Vet Ed 2020; 32(2):90-95) hypothesized that admission serum creatine kinase (CK) activity and glucose, lactate and triglyceride concentrations were significantly associated with outcome in hospitalised horses with AM. Clinicopathological data are described. Medical records from three referral hospitals over 6 years were examined; data from 64 horses were collected. Blood glucose, lactate and triglyceride concentrations were increased in 76%, 89% and 92% of horses on admission, respectively. Survival was 44%. Increasing CK activities and triglyceride concentrations, but not aspartate aminotransferase activities during hospitalisation, were associated with outcome. No treatments apart from sedation were associated with outcome. In this study, presence or absence of increased recumbency, colic signs or bladder distension were not associated with survival. It was considered unlikely that any single predictive indicator or combination of predictive factors is 100% accurate. The authors concluded that decisions should be based on case progression in combination with individual circumstances. This study suggests that the mortality rate in hospitalised horses suffering from AM could be better than previously reported. Admission serum CK activity could be of prognostic value.
Facial nerve paralysis in 64 equids: clinical variables, diagnosis and outcome
Facial nerve paralysis (FNP) is poorly described in equids. This study by Boorman et al (J Vet Int Med 2020; 34:1308-1320) investigated causes and associations among clinical variables, diagnosis, and outcome in FNP as well as prognosis. Disease is frequently unilateral and signs include muzzle deviation, ptosis, partial or complete inability to blink and abnormal ear positions. Medical records over 19 years were reviewed. Anaesthetic complications were excluded. Sixty four equids were included. Common causes included trauma (31%), central nervous system (CNS) disease (25%), idiopathic (19%) and temporohyoid osteoarthropathy (THO) (16%). Resolution was complete in 53% of cases and partial in 11%. Ultimately 25% were euthanased. Pony breeds were 40.71 times more likely to have THO compared with Thoroughbreds. Animals with muzzle deviation were less likely to have a final diagnosis of trauma than those without. A negative association between presence of ear droop and CNS disease was found. Advanced age was associated with being less likely to have full resolution. Onset of disease within the last 7 days was more likely to have full resolution. In conclusion, the authors noted that the cause of FNP was markedly different in equids compared with other species. For surviving equids, the prognosis with FNP was generally good.
Fasciola hepatica in UK horses
Liver fluke may be responsible for some cases of undiagnosed equine liver disease. There is difficulty in diagnosis with faecal egg detection methods. Howell et al (Equine Vet J 2020; 52:194-199) aimed to define how liver fluke affects the UK horse population. Objectives included optimising an antibody-detection enzyme-linked immunosorbent assay (ELISA) to aid diagnosis; to determine prevalence of liver fluke infection in an abattoir population; and to investigate whether liver fluke is a cause of liver disease. A Fasciola hepatica antibody-detection ELISA validated in cattle was modified. Livers were inspected externally at an abattoir for flukes and, when present, blood was taken from the heart for the ELISA. Cases were then recruited from veterinarians, from patients that had liver disease. The ELISA had 71% sensitivity and 97% specificity. Out of 342 horses examined at the abattoir, 9.8% were ELISA positive and 1.8% had visible liver flukes. A case-control study included 109 cases and 160 controls. Horses testing positive (11% of cases and 2.5% of controls) for liver fluke were from a variety of locations. There were no significant differences between groups in any variable except grazing history. The authors concluded that liver fluke occurs frequently, and that it may be an under-recognised cause of liver disease.
Effect of long-term overfeeding of a high-energy diet on glucose tolerance in Shetland pony mares
Overfeeding is associated with obesity and insulin dysregulation (ID), both risk factors for equine metabolic syndrome. How chronic overfeeding affects development of these factors is poorly understood. It is thought that a limited amount of weight gain alone does not trigger ID. The study objective (Fonseca et al. J Vet Int Med 2020; 34:1339-1349) was to determine the influence of a long-term high-energy (HE) diet on the development of ID and obesity in young Shetland pony mares. It was hypothesized that ID would appear soon after initiating the diet, and that prolonged feeding would lead to progression of ID. Seven mares were fed a HE diet at 200% energy requirements for a 2-year period in two blocks. Four controls were included. Bodyweight, body condition scores and ultrasound fat measurements were performed regularly. Oral glucose tolerance tests were regularly performed. The HE group had a significant increase in mean basal plasma glucose and peak insulin concentration compared with controls when the HE diet was fed. Peak insulin timing was also earlier than in controls. The authors concluded that feeding the HE diet led to more efficient glucose metabolism within 5 weeks, followed by significant hyperinsulinaemia and obesity. Hyperinsulinaemic status was reversed during hay-only feeding, but returned rapidly after restarting the HE diet.