CHRONICAL GRASS SICKNESS (EQUINE DYSAUTONOMIA) IN A 2-1 2 YEARS OLD ICELANDIC MARE ON A NORTH FRISIAN ISLAND/

Chronic grass sickness (equine dysautonomia) was diagnosed in a two an d a half years old Icelandic pony mare from a herd grazed on one of th e Northern Frisian islands. Since 1988, a total of seven young horses up to four years of age died in the same herd under clinical signs of the acute form of grass sickness. In the same area, six additional cas es occurred in other herds. Typically, the affected animals were graze d on green pastures. Outbreaks of the disease occurred from March to J uly and were associated with weather changes towards a cooler weather with heavy, chilly winds. After an acute onset oi clinical symptoms su ch as sweating, muscular tremor, dyspnea, tucking up the abdominal flo or and arching the back, clinical signs in the presented case were dom inated by dysphagia and emaciation. The animal did not pass faeces unt il the fourth day after realisation of the disease when diarrhoea was observed for one day. From the fifth to the ninth day of the disease n o faeces were passed. However, diarrhoea reoccurred from the tenth day on. intensive symptomatic therapy was carried out. Since the clinical symptoms persisted and the animal developed an additional hyperlipemi a, euthanasia was performed two weeks after onset of clinical signs, A t necropsy, macroscopic findings included a focal, chronic ulceration of the cutaneous gastric mucosa, an acute parasitic colitis and lympha denitis of the colonic lymphnodes. By histology, degenerative lesions were identified in the autonomic nervous system, the dorsal root gangl ia, specific brain stem nuclei and tile spinal cord grey matter. Affec ted neurones and ganglial cells exhibited an eosinophilia of the cytop lasm, chromatolysis, margination of pyknotic nuclei and to some degree vacuolisation. In the autonomic plexus and ganglia, the number of gan glial cells was markedly reduced. in the coeliacomesenteric ganglion, the amount of non neuronal cells was increased. By immunohistochemistr y, infiltrations of predominantly T-lymphocytes were detected in a dif fuse and follicular pattern. The direct cause of the disease was not d etermined. However, it was concluded that grass sickness may occur on a sporadic basis in Germany.