Subacute Necrotizing Encephalopathy of Simmental Calves

Abstract

Neurologic disorders in feedlot cattle are common. These "brainer" cases often occur sporadically and do not warrant diagnostic investigation. The occurrence of this recently recognized neurologic disorder warrants investigations to establish a definite diagnosis when purebred Simmental calves are affected and parentage data may be available. In excess of 30 cases have been confirmed since this disorder was first reported in the USA in 1991.³ Many more cases were reported by owners but no data was available to confirm the diagnosis. Due to its clinical similarity to many currently recognized conditions and lack of familiarity with the disease it likely goes undiagnosed in most feedlots. The disease was first described in Australia in 1989 and Australian cases were clinically and pathologically similar to those reported in North America.^2,3,4,5 The American cases have been reported in Oregon, Iowa, Kansas and North Dakota. As diagnostic criteria were well established by 1994, cases may have been diagnosed at other laboratories and not reported to the program.⁵ Most recent cases were examined in the fall of 1997 indicating the problem persists in North American cattle populations.