Swayback (enzootic ataxia) in Alberta lambs

Area of Science:

• Veterinary Neurology
• Animal Pathology
• Toxicology

Background:

• Swayback (enzootic ataxia) is a neurological disease affecting newborn lambs.
• This disease was not previously documented in Canada before 1972.
• A significant outbreak occurred in Alberta, impacting over 60% of lambs in one flock.

Purpose of the Study:

• To describe a novel occurrence of swayback in Canadian newborn lambs.
• To investigate the pathological and etiological factors associated with the enzootic.
• To determine the relationship between ewe diet and the disease in lambs.

Main Methods:

• Necropsy and histopathological examination of affected lambs.
• Analysis of gross lesions, including cerebral cavitation and gelatinous changes.
• Biochemical analysis of copper levels in lambs and ewes.
• Evaluation of the ewes' diet during gestation and lactation.

Main Results:

• 66.67% of examined lambs presented with gross cerebral white matter lesions.
• Histopathology revealed neuronal damage (chromatolysis, hyalinization) and myelin deficiencies in the central nervous system.
• Affected lambs and their dams exhibited low hepatic and serum copper levels.
• The study discusses the potential role of sugar beet top silage in the ewes' diet.

Conclusions:

• The Alberta outbreak represents the first reported cases of swayback in Canada.
• Neuropathological findings and low copper levels are indicative of swayback.
• Dietary factors, specifically sugar beet top silage consumption by ewes, are implicated in the enzootic ataxia outbreak.