Septicemia and meningoencephalitis in pastured cattle caused by a Haemophilus-like organism ("Haemophilus somnus").

Septicemia and meningoencephalitis developed in 10 pastured cattle 7 months to 3 years of age. Two unrelated herds were involved. Necropsy findings were similar to those previously reported in cattle infected with a Haemophilus-like organism, including multifocal hemorrhages in some muscles, suppurative polyarthritis, and multifocal hemorrhagic thrombi in the brain. A Haemophilus-like organism was isolated from one animal. It was characterized by growth on blood agar or tryptose agar plus a feeder streak under raised carbon dioxide tension, and lack of response to Haemophilus growth factors X and V.