Role of endotoxin in the pathogenesis of haemorrhagic septicaemia in the buffalo

The pathogenesis of haemorrhagic septicaemia in buffalo infected with Paste urella multocida is poorly understood. However, the characteristic of sudde n onset leading to the rapid death of infected animals is similar to that s een in other clinical conditions known to involve endotoxic shock. The obje ctives of the work were to assess the contribution of endotoxaemia to the d isease's pathogenesis and to characterize the pathophysiological reaction, including the acute phase response, of buffalo to experimental infection wi th P. multocida serotype B:2, the bacterium responsible for the disease in Asia. After intranasal infection of eight buffaloes with a culture of a fie ld isolate of P. multocida serotype B:2, three animals succumbed to the dis ease at 26-30 h post-infection (p.i.) and five survived. Rectal temperature s of infected animals rose to a peak at about 10 h p.i. and surviving anima ls showed a second peak in rectal temperature at 36 h p.i. Endotoxin was pr esent only in serum of non-surviving animals 3-5 h before death or killing during which time concentrations increased rapidly, correlating with the de velopment of overt clinical signs and reductions in rectal temperature, con centrations of white blood cells, serum thyroxine, iron, copper and zinc, a n increase in serum haptoglobin and cortisol and the detection of a low-gra de bacteraemia. A strong acute phase response was maintained in surviving a nimals with a progressive rise in serum haptoglobin over 96 h p.i., a slow rise in the serum copper concentration from 24 h p.i. and an increase, from about 65 h p.i., in serum alpha (1)-acid glycoprotein. The findings demons trate that a progressive endotoxaemia and associated sequelae correlates wi th the development of overt haemorrhagic septicaemia disease and sudden dea th in buffalo. (C) 2001 Academic Press.