HISTOPATHOLOGICAL CHANGES IN MICE INFECTED WITH RIVER WATER CONTAMINATED BY PASTEURELLA MULTOCIDA TYPE B:2

Haemorrhagic Septicaemia (HS) is a fatal systemic disease of bovines typified by an acute, highly fatal septicaemic disease with high morbidity and mortality. In this study, sixty five adult ICR mice were used for the study. In the first phase, 5 mice each were inoculated with 10⁹ cfu of P. multocida type B:2 through the intraperitoneal route. After development of classical signs of HS, the mice were euthanised and dropped into a tank of river waterfor 24, 48 and 72 h. Contaminated water from the tank were collected at the three different times (24, 48 and 72 h) and was used for intraperitoneal, oral and aerosol inoculation of 15 mice each with a dose of 1 mL^-1 10⁹ cfu (intraperitoneal and aerosol) and 0.4 mL^-1 10⁹cfu (oral). The control group (n = 5) was given phosphate buffered saline. All mice in the three groups and control were culled after 72 h post inoculation and the vital organs (liver, spleen, lung, kidney, heart, brain) were collected in 10% buffered formalin, procesed, sectioned and stained with H&E. Degeneration and necrosis, hemorrhage and infiltration of inflammatory cells were the most observed lesions in all the organs, while thrombosis and oedema were least observed. The lesion severity was moderate to severe using contaminated water at 72 h post contamination and mild to moderate when inoculated with water 24 and 48 h post contamination. Mice inoculated through the oral and intraperitoneal routes recorded more severe lesion compared with those inoculated through the aerosol route. However, using contaminated water at 24 h, mice inoculated through the aerosol route had the highest distribution of inflammatory cells in the lungs, which declined following inoculation with contaminated water at 48 and 72 h, respectively.This study has shown that contamination of water bodiesby carcasses of HS infected animals is a likely source of infection to heathy animals in the wild and that development of lesions severity is time dependant and significantly higher using contaminated water at 72 h than water contaminated for 24 and 48 h. This further indicates the danger of leaving decomposing carcasses in water bodies for prolonged periods.