Acquired equine polyneuropathy in Norway and Sweden: a clinical and epidemiological study.

The study looks into acquired equine polyneuropathy (AEP), a serious and fatal disease affecting horses in Norway and Sweden, predominantly in winter and spring. Using neurological examinations, demographic data, and observations, the researchers highlighted AEP’s signs, affected horse characteristics, seasonality, and links to farm practices, particularly the use of wrapped forage.

Study method

• The authors conducted neurological examinations on affected horses and studied 157 horses from 13 different farms that had seen outbreaks between 2007 and 2009.
• They collected data regarding the horses’ demography, usage, turning-out, feeding habits, prophylactic strategies, and long-term outcomes.
• The sample represented diverse breeds and age-groups.

Findings

• A total of 42 horses were confirmed to have acquired equine polyneuropathy (AEP).
• The definitive signs of AEP included a specific dysfunction in the digital extensors and “knuckling” of the pelvic limbs, noted in 34 of the confirmed cases.
• Eight additional horses were suspected to have AEP due to the acute presence of neurological diseases.
• The disease appeared primarily during winter and spring. New cases occurred within about 100 days of the first (“index”) case.
• Both affected and unaffected horses were found to have been fed wrapped forage.
• In the studied population, the AEP prevalence was 27% and the fatality rate was 29%.

Implications

• The median duration of AEP in surviving horses was 4.4 months, with a recovery range of 1 to 17 months. After this period, they could return to their full working capacity.
• Younger horses (<12 years) were found to be less prone to AEP and had higher survival rates.
• None of the management practices at the affected farms appeared to differ significantly between affected and healthy horses, suggesting that factors contributing to the disease surpass just farm management.
• The fact that all farms used wrapped forage points towards a potential link, yet no definitive causal relationship has been established.

Conclusions

• The study provides significant clinical and epidemiological insights into AEP, previously an unknown and emerging disease with fatal potential
• While highlighting the characteristics and signs of AEP, the study underscores its seasonality and potential links to farm practices (specifically the use of wrapped forage), which warrant further investigation.