To report history, clinical examination findings, clinicopathologic findings, diagnostic test results, treatment, and outcome in horses with a novel idiopathic hepatitis syndrome.
13 client-owned horses.
Medical records of horses that were presented with fever and increased blood liver enzyme activity over a 16-month period were reviewed (December 1, 2020, to April 1, 2022). Collected data included signalment, history, clinical and clinicopathologic findings, diagnostic test results, treatment, clinical progression, and short-term outcome.
Affected horses were presented between December and April of each of the 2 seasons investigated. The majority of horses developed cyclic fevers over the course of 3 weeks, during which time histologic evidence of hepatitis was observed. Histologic lesions included hepatic necrosis, neutrophilic to lymphohistiocytic inflammation, biliary epithelial injury, and portal fibrosis. Systemic inflammation was evidenced by increased serum amyloid A concentration and leukon changes. No horse developed signs of hepatic insufficiency, and all horses clinically recovered. Return of serum activity of GGT to within the reference range occurred within 16 weeks in most horses. Histologic lesions remained evident up to 27 weeks after initial presentation in 1 horse.
Although an etiologic agent has not been identified, an apparently seasonal equine hepatitis syndrome was characterized by fever, systemic inflammation, increased liver enzyme activity, and histologic evidence of hepatitis. An infectious cause is suspected on the basis of histology and outcome.
To investigate the role of omega-3 polyunsaturated fatty acids (Ω-3)–derived proresolving lipid mediators (PRLM) in the resolution of mild airway inflammation in horses.
20 horses with mild airway inflammation.
Horses previously eating hay were fed hay pellets (low Ω-3 content; n = 10) or haylage (high Ω-3 content; 9) for 6 weeks. Dust exposure was measured in the breathing zone with a real-time particulate monitor. Bronchoalveolar lavage (BAL) was performed at baseline, week 3, and week 6. The effect of PRLM on neutrophil apoptosis and efferocytosis was examined in vitro. BAL fluid inflammatory cell proportions, apoptosis of circulating neutrophils, efferocytosis displayed by alveolar macrophages, and plasma lipid concentrations were compared between groups fed low and high amounts of Ω-3 by use of repeated measures of generalized linear models.
Dust exposure was significantly higher with hay feeding, compared to haylage and pellets, and equivalent between haylage and pellets. BAL fluid neutrophil proportions decreased significantly in horses fed haylage (baseline, 11.8 ± 2.4%; week 6, 2.5 ± 1.1%) but not pellets (baseline, 12.1 ± 2.3%; week 6, 8.5% ± 1.7%). At week 6, horses eating haylage had significantly lower BAL neutrophil proportions than those eating pellets, and a significantly lower concentration of stearic acid than at baseline. PRLM treatments did not affect neutrophil apoptosis or efferocytosis.
Despite similar reduction in dust exposure, horses fed haylage displayed greater resolution of airway inflammation than those fed pellets. This improvement was not associated with increased plasma Ω-3 concentrations. Feeding haylage improves airway inflammation beyond that due to reduced dust exposure, though the mechanism remains unclear.