24 Pages Fermo_7.cdr

In an attempt to understand the pathology of E.coli mastitis, six lactating rabbits each were infected with E. coli strains O9(36) and O147 isolated from bovine mastitis cases. One rabbit was euthanized at 24 hrs interval and the mammary glands were analyzed by gross and histopathology, electron microscopy and immunohistochemistry for induction of mastitis. The infected rabbits grossly revealed the inflammation of mammary glands by 24 hours post infection which intensified by 48 hours post infection. The gross lesions observed in the mammary glands were tumefaction, hyperemia, hard or firm consistency and oozing out of thick, slightly discolored milk upon incision. The histopathological lesions observed in the mammary glands of infected rabbits were very severe at 24 and 48 hours post infection with total loss of architecture and the lesions reduced in severity from 72 hours post infection. The lesions comprised hyperemia, perilobular and interlobular edema, degeneration and necrosis of the lining epitheliai cells, presence of large number of heterophils in the acini, septa and perivascular spaces, severe destruction of the acini and presence of E. coli organisms within the acini, septa and the perivascular areas. The ultrastructural changes in the mammary glands at 48 hours post infection consisted of disruption of basement membrane of the alveolar epithelium, loss of microvilli, disruption of the endoplasmic reticulum, degeneration of mitochondria and presence of bacteria as electron dense coccobacillary structures in the lumina of the alveoli and in the interacinar septa. The immunohistochemical analysis of the mammary gland tissue samples demonstrated the presence of E.coli in the infected mammary glands as brownish yellow coccobacillary rods in clumps or in dispersed manner. It was concluded that both O9(36) and O147 strains of E.coli successfully induced acute mastitis in rabbits.