Acquired equine polyneuropathy in Norway and Sweden: A clinical and epidemiological study

Abstract

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.

Science in brief: Clinical highlights from the American Association of Equine Practitioners' 58th Annual Convention and Equine Veterinary Journal Supplement 43

“…A second group of presentations in this session covered aspects of neurological conditions, including vertebral osteomyelitis, Sarcocystis neurona and Neospora hughesi . The EVJ supplement included a clinical and epidemiological study describing the novel disease acquired equine polyneuropathy or ‘Scandinavian knuckling syndrome’ . Of unknown aetiology, case clusters of acquired equine polyneuropathy have been reported sporadically since the 1990s.…”

Long‐term follow‐up of Norwegian horses affected with acquired equine polyneuropathy

“…Moreover, most affected horses have been fed wrapped forage, suggesting an environmental, possibly feed‐related trigger. Although previous studies concluded that there is no indication of an infectious aetiology, AEP often affects more than only one horse at the farm .…”

“…Most recumbent cases are subjected to euthanasia and fatality rates have varied from 29 to 53% . Although horses that remain able to rise up and stand with or without support, seem to recover, one study reported intermittent knuckling up to 17 months after onset of disease . Histopathological examination of peripheral nerves from horses subjected to euthanasia due to AEP has revealed large fibre predominant neuropathy with conspicuous inclusion body schwannopathy and demyelinating inflammation supporting ubiquitous histopathological features.…”

“…Although previous reports indicate that many AEP affected horses recover , there is a lack of large scale follow‐up studies of survivors and objective long‐term survival data. The only treatment recommendation is to rest for months or even years, and the lack of knowledge of the disease`s time‐course and outcome is frustrating for owners.…”

Evaluation of immunity and clinical disease following infection of horses with Equine herpesvirus-1 and mutants of differing neuropathogenic potential

“…Gr€ ondahl 1 , K Hultin J€ aderlund 2 , S. Hanche-Olsen 2 1 National Veterinary Institute, Uppsala, Sweden; 2 Department of companion animals clinical sciences, Norwegian University of Life Sciences, Oslo, Norway Acquired equine polyneuropathy (AEP) is an emerging disease of horses in northern Europe since the 1990's [1,2]. Gr€ ondahl 1 , K Hultin J€ aderlund 2 , S. Hanche-Olsen 2 1 National Veterinary Institute, Uppsala, Sweden; 2 Department of companion animals clinical sciences, Norwegian University of Life Sciences, Oslo, Norway Acquired equine polyneuropathy (AEP) is an emerging disease of horses in northern Europe since the 1990's [1,2].…”