Atypical myoglobinuria in grazing horses

In autumn 1995 for the first time horses were taken to the clinic for horses in Hannover that showed symptoms of a muscular disease. not seen so far. None of the twelve patients survived this atypical myoglobinuria although extensive treatment was performed. At the same time other veterinarians reported on 103 cases. 99 of them died. Without exception all horses and ponies were not in training and kept on pasture just before the disease set on. In most of the cases more than one horse of a single pasture was affected. Different breeds, sexes and age groups were concerned. In the beginning all horses showed muscular tremor, stiffness and stagger. They were dull or apathetic. Heart rates and breathing frequencies were elevated. Appetite was maintained very long and only a few horses were painful. The rectal palpation revealed only a highly filled bladder. All patients showed a massive elevation of creatine kinase and myoglobinuria was characteristic. Treatment included infusion of isotonic solutions, analgesics, anti-inflammatory agents and doses of Vitamin E/selenium. Despite intensive medical care and treatment all horses came to recumbency within three days and finally died. In pathologic-anatomical examinations various muscle groups showed a marked, acute rhabdomyolysis of type I fibres. Up to this day laboratory diagnostics, clinical, pathologic-anatomical, histological and toxicological findings could not reveal the etiology of atypical myoglobinuria.