Three cases of a presumptive atypical myopathy in New Zealand horses.

The article reports on three cases of a rare and potentially deadly muscle disorder, known as atypical myopathy, in young thoroughbred fillies in New Zealand. All three horses showed similar symptoms and on examination and biochemical tests, they were diagnosed with the condition, marking the first time such cases have been reported in New Zealand.

Summary of the case study

• Three weanling Thoroughbred fillies in New Zealand developed symptoms like depression, muscle rigidity and, in one case, colic symptoms and cardiovascular shock.
• Physical examinations of the fillies revealed abnormal signs such as elevated heart and respiratory rates along with muscle stiffness, particularly in the back and rump.
• The horses underwent biochemical testing, which revealed increased levels of creatinine kinase and aspartate aminotransferase, substances typically elevated in cases of muscle damage or myopathies.
• On the basis of the clinical signs and testing, all three were diagnosed with a presumptive atypical myopathy – a disease that had not been previously reported in New Zealand.

Methodology and Results

• The horses were treated with supportive therapy, following the guidelines available in the literature on this particular condition.
• While two of the fillies responded to the treatment and recovered, one had to be euthanised due to rapidly deteriorating health.
• Post-mortem of the euthanised horse indicated acute, severe degeneration of muscle fibers in the trapezius muscle, confirming myopathy.

Research Conclusions

• This research reveals the existence of atypical myopathy in New Zealand for the first time, a fatal muscle disorder typically linked to pasture grazing that has previously been reported in Europe and North America.
• The study suggests that the disease, along with a very similar condition known as seasonal pasture myopathy in North America, may be more widespread than previously thought.
• Finally, this report adds to the body of literature on atypical myopathy, providing case examples and clinical data that aid in better understanding, diagnosing, and managing this rare condition.