Emma N. Adam

Summary Rotaviral infection is the most common cause of foal diarrhoea, leading to severe dehydration and electrolyte derangements, which, left untreated, can be rapidly fatal. Until 2021, equine rotaviruses of group A (ERVA) were considered to be the only rotaviruses affecting horses; however, equine rotavirus group B (ERVB) has recently been identified in association with neonatal foal diarrhoea outbreaks. ERVA has been observed globally in many countries with large equine industries. Equine rotaviruses (ERV) are extremely contagious. Foals as young as 12 hours of age can show clinical signs. These clinical signs include inappetence, dullness, colic and characteristic watery diarrhoea that can be orange‐yellow to reddish‐brown in colour. Nowadays diagnosis relies mainly on qPCR—a test limited by the fact that PCR is a directed test requiring a priori knowledge of a pathogen's genome. The mainstay of therapy for rotaviral diarrhoea is supportive care since treatment directly targeting the virus itself is not available. Prevention relies on proper biosecurity protocols and, in the case of ERVA, vaccination of mares. Currently, researchers at the University of Kentucky are working on developing a vaccine for ERVB.

Background A single dose of metformin administered 1 h prior to oral glucose challenge was previously shown to reduce insulinaemic responses in horses with experimentally‐induced insulin dysregulation (ID). Targeted administration could be useful for controlling post‐prandial hyperinsulinaemia in horses with naturally‐occurring ID. Objectives The objective was to compare the insulinaemic and glycaemic responses to oral sugar testing (OST) performed at different intervals after a single dose of metformin in horses with naturally‐occurring ID. We hypothesised that pre‐treatment with one dose of metformin would significantly decrease the insulinaemic response to OST. Study design Randomised cross‐over in vivo experiment. Methods Eight university‐owned adult horses with naturally‐occurring ID underwent OST 1, 2 and 6 h following a single oral dose of metformin (30 mg/kg) or 1 h after placebo (240 mL water) with a 7‐day washout between treatments over a period of 3 weeks. Plasma insulin, C‐peptide and glucose concentrations were measured at 0, 60 and 90 min after 0.45 mL/kg light corn syrup and the effect of treatment (and the interval since dosing) examined using a mixed effects linear regression model. Results Metformin treatment had no significant effect on plasma glucose, insulin or C‐peptide concentrations at any time point compared with placebo ( p > 0.05). For OST 1 h post metformin, median (IQR) plasma insulin was 91.3 (62.4–114.9) μIU/mL at 60 min versus 76.2 (59.1–134.5) for placebo ( p = 0.8) and 62.7 (31.4–109.7) at 90 min versus 51.8 (29.2–126.3) for placebo ( p = 0.9). Main limitations Small sample size may limit identification of more subtle decreases in insulin concentration with metformin pre‐dosing. The results of this study are relevant only for one pre‐treatment dose (30 mg/kg) which limits extrapolation to predictions about the effects of longer‐term metformin administration on insulin and glucose dynamics in the horse. Conclusions and clinical importance The results do not support the use of targeted metformin treatment to reduce post‐prandial hyperinsulinaemia in horses with naturally‐occurring ID.

Background Intra‐articular (IA) corticosteroids are regularly used in equine athletes for the control of joint inflammation. Objectives The goal of this study was to use an acute synovitis inflammation model to determine the residual effects of IA betamethasone and triamcinolone acetonide on various inflammatory parameters and lameness. Study design Crossover randomised trial. Methods Five mixed‐breed, 2‐year‐old horses were randomly allocated to an IA treatment of the radiocarpal joint with 9 mg of either betamethasone or triamcinolone acetonide. Two weeks following treatment, horses were injected with 1 μg of lipopolysaccharide (LPS) diluted in 1 ml of saline. Following LPS injection, horses were crossed‐over and both sets of injections were repeated after a washout period. Blood samples were collected at multiple time points for mRNA analysis, as well as serum amyloid A (SAA) and cortisol determination. At each time point, lameness was also subjectively scored. Additional injections with saline‐only or LPS‐only (twice) were conducted as negative and positive controls, respectively. Two‐way repeated measures analysis of variance was used to analyse all data. Results Corticosteroid‐only treatments result in significant mRNA expression differences, as well as significant and prolonged cortisol suppression. Following LPS injection, there was a residual treatment effect with triamcinolone evidenced by a significant treatment effect on IL‐6 and PTGS1 (cyclooxygenase‐1), lameness, SAA and cortisol concentrations, while only IL‐6 expression was affected by betamethasone. Main limitations The acute synovitis model used here results in significant inflammation and is not representative of the low‐grade inflammation seen with typical joint disease and residual anti‐inflammatory effects may be more profound in naturally occurring joint disease. Conclusions Current regulatory guidelines may be insufficient if the concern is residual anti‐inflammatory effects. Additionally, intra‐articular corticosteroid administration is not without risk, as evidenced by a significant suppression of serum cortisol concentration and, as such, the benefits of their administration should be weighed against those risks.