Hepatic disease in Alberta horses: A retrospective study of ‘alsike clover poisoning’ (1973-1988).

This is a study which took place over 16 years that looked at incidences of ‘alsike clover poisoning‘ in horses in Alberta. The research found that the disease, characterized by distinct liver damage, was more common in certain areas, signaling it could be related to exposure to some environmental factors, potentially the locally cultivated alsike clover. Yet, the evidence collected in this retrospective study isn’t sufficient to directly blame the clover.

Horse Health in Alberta and Alsike Clover Poisoning

• Between 1973 and 1988, 49 horses in Alberta were diagnosed by veterinary laboratories with ‘alsike clover poisoning’. This long-term study aimed to investigate this condition and look for any patterns or correlations.
• The reported cases revealed a distinct northwestern distribution, predominantly from the Peace River District. Interestingly, this distribution did not align with the main populations of horses in Alberta, hinting that the local environment could influence the occurrence of the disease.
• The area where the disease was prevalent correlated with locations of alsike clover cultivation, hence the term ‘alsike clover poisoning’.

Clinical Presentations and Histological Findings

• The disease presented itself in two different forms: chronic and nervous. These presentations follow the descriptions given by a researcher named Schofield, suggesting consistency in the condition’s symptoms and effects.
• Post-mortem, histological examination of tissues from 45 horses showed significant damage localized in the liver. The damage was characterized by biliary fibrosis and epithelial proliferation, both signs of serious liver disease.

Disease Etiology and Conclusions

• The condition, termed ‘alsike clover poisoning’, was determined to be a distinct disease, most likely caused by exposure to an external toxin. The study’s results, while inconclusive, suggest that the alsike clover, prevalent in the disease-heavy areas, could be the source of this toxin.
• Despite the correlation between the areas of alsike clover cultivation and the location of poisoning cases, the data collected were not strong enough to definitively attribute the disease to alsike clover. More research is needed to identify the exact cause of ‘alsike clover poisoning’ in horses.