SummaryReasons for performing study: Acquired equine polyneuropathy (AEP, also known as 'Scandinavian knuckling syndrome'), is a serious disease of unknown aetiology, which emerged clustering in horse farms in Sweden, Norway and Finland in the 1990s. Clinical and epidemiological data regarding the syndrome are scarce. Objectives: To describe the clinical and epidemiological findings and outcome in outbreaks of AEP and compare risk factors in affected and unaffected horses on affected farms in Norway and Sweden during [2007][2008][2009]. Methods: Neurological examinations were performed and data collected regarding demography, usage, turning-out, feeding, prophylactic strategies and long-term outcome. Results: Thirteen affected farms with 157 horses of various breeds, of which 42 were AEP cases, were studied. Typical digital extensor dysfunction and knuckling of pelvic limbs were noted in 34 definitive cases. Eight additional plausible cases had a severe, acute course of neurological disease. There were no signs of brain or cranial nerve dysfunction. Cases occurred from December to April, with new cases emerging within 100 days of the index case. Affected and unaffected horses were fed wrapped forage. Prevalence for AEP was 27% and case fatality 29%. The median duration of AEP in survivors was 4.4 months (1-17 months). Survivors returned to full work within 19 months (median 6.6 months). Acquired equine polyneuropathy was less prevalent in horses aged >12 years and young horses had a higher chance of survival than older horses. Management factors did not differ between affected and unaffected horses. Conclusions: Acquired equine polyneuropathy is a potentially fatal neurological disease characterised by pelvic limb knuckling. Surviving horses returned to normal function after a long period of rest. Cases were clustered in farms during the winter/spring season. Wrapped forage was used in all farms. Potential relevance: The results provide valuable insights into the clinical examination, handling and prognosis of cases of AEP, an emerging neurological disease of unknown aetiology in horses.

Wrapped forages such as haylage and silage are increasing in popularity in equine feed rations, but knowledge of their microbial composition, especially of haylage, is scarce. Haylage may be more at risk of mould growth compared to silage, and methods for the assessment of hygienic quality of haylage are needed. Varying culturing conditions, including aerobic ⁄ anaerobic incubation, four substrates and three incubation temperatures were therefore evaluated for analysis of fungi in haylage samples from eighteen horse farms, taken on two occasions (autumn and the following spring). Average mould counts in forage samples were low, but fungi with the potential for producing mycotoxins, such as Aspergillus fumigatus and Penicillium spp., were present. The microbial composition and content of fermentation products were similar in haylage samples taken in autumn and in spring. The type of substrate used for cultivation did not influence mould or yeast counts, but not all mould species were present on all substrates. Incubation temperature influenced fungal counts and the presence of mould species. By using at least two substrates (malt extract agar and dichloran 18% glycerol agar) and two incubation temperatures (25 and 37°C), all mould species ⁄ genera that were identified in this study could be detected.

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SummaryThe effects of an endurance ride on neutrophil functions in endurance-trained horses were evaluated and related to metabolic changes and changes in cortisol concentrations. Blood samples were taken from 7 horses (aged 9-15 years) one day before, and then 30-60 min, 1 day and 8 days after the ride. The race resulted in elevated serum cortisol levels (<465 nmoy1) and an increased neutrophiklymphocyte ratio.Immediately post race, the neutrophil ability to engulf yeast was increased. One day after the race, a decrease in leukotriene BQ production (approximately 40%) and in the respiratory burst (approximately 75%) was observed.Blood glucose concentration remained unchanged, as did serum lactate, which was low. After the race, the muscle glycogen stores were about 33% of the values noted after 8 days of recovery. Histochemical staining showed that 22 * 2% of the muscle fibres were totally depleted of glycogen. CK activity increased significantly from 40 * 10 mmoVmin pre-race to 228 * 38 mmoVmin post race. It was concluded that both hormonal and metabolic changes occurred during an endurance ride, which not only triggered neutrophil activation, but also induced alterations in their functional capacities.

Summary The aim of this study was to investigate the phagocytic and killing capacities as well as expression of CD18 of neutrophils obtained from healthy foals from birth to age 8 months. Blood was taken from 6 Standardbred foals at 7 time‐points between ages 2–56 days and thereafter once a month. For comparison, cells from 16 mature horses were evaluated. Neutrophil phagocytosis of yeast cells was assessed by flow cytometry after opsonisation with mature pooled serum, autologous serum or anti‐yeast IgG. The killing capacity of the neutrophils, as indicated by the oxidative burst, was monitored by chemiluminescence. Serum IgG concentration was measured by radial immunodiffusion. In addition to clinical examination, the amount of serum amyloid A and the total leucocyte count were used as markers for infection. The phagocytic ability was impaired until age 3 weeks, when autologous serum was used as opsonin. Killing capacity was also low initially but, from 3 months onwards, chemiluminescence values were equal to or higher than in mature horses. Serum IgG decreased from 10 g/l at 2 days to 5 g/l at 2 months and then increased gradually to 10 g/l at the end of the study. These findings may in part explain the increased susceptibility to bacterial infections in young horses.

Automated total cell counts obtained on the Medonic analyzer correlate well with manual counts in equine synovial fluid; however, pretreatment with hyaluronidase is required to minimize error flags. Automated differential counts are not accurate for synovial fluid.

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