An outbreak of pneumonic mannheimiosis in a livestock farm in sub-temperate region of India.

Respiratory mannheimiosis is a highly contagious disease of ruminants caused by Mannheimia haemolytica. A sudden onset of a respiratory disease characterized by high fever with ocular and nasal discharge was observed in the month of July, 2011 in cow calves (six months to one year age) in a livestock farm. Necropsy examination was conducted on four carcasses. Grossly, lungs revealed congestion, haemorrhages and the prominent interlobular septa which were massively filled with fibrinous exudate. Microscopically, there was congestion, haemorrhages, fibrinous exudation along with massive infiltration of neutrophils in the alveoli, bronchi and bronchioles. Giemsa and Gram's stained impression smears from the lung tissue and other body tissues/fluid revealed the presence of characteristic oat shaped cells and bipolar gram negative bacteria, respectively. The presence of oat shaped cells along with gross and microscopic changes predominant in the lungs was indicative of an outbreak due to pneumonic mannheimiosis. Sick animals were isolated and immediately treated with antibiotics along with administration of non-steroidal anti-inflammatory drugs which lead to uneventful recovery.