Experimentally induced coliform (Aerobacter aerogenes) mastitis in normal cows and in cows made neutropenic by an equine anti-bovine leukocyte serum
Jain, N.C.; Schalm, O.W.; Lasmanis, J.
American Journal of Veterinary Research 32(12): 1929-1935
1971
ISSN/ISBN: 0002-9645 PMID: 5167169 Document Number: 40523
Three cows having normal peripheral blood neutrophil counts developed acute mastitis within 4-6 hours after infusion of Aerobacter aerogenes into a normal lactating quarter. The resulting leucocytosis into the milk immediately restricted bacterial multiplication. Swelling and firmness of the gland subsided in 24-36 hours, Aerobacter disappeared from the glands after 7-9 days, and leucocytosis into the milk gradually subsided; normal milk returned within 2 weeks. Two cows were made neutropenic with an equine anti-bovine leucocyte serum and were exposed to viable Aerobacter in doses similar to those given the control cows. These cows developed only slight swelling and little leucocytosis into the milk during the 1st day. In the absence of significant leucocyte diapedesis into the milk, Aerobacter increased to billions per milliliter of milk between the 10th and 30th hour after inoculation. Massive amounts of endotoxin so generated resulted in an extreme inflammatory reaction, developing after 24-30 hours, which led to necrosis and irreversible damage to the mammary parenchyma and cessation of milk secretion by all quarters. The results substantiate the major role that neutrophil leucocytes have in the mammary gland in defence against virulent coliform organisms whether susceptible or resistant to humoral inhibition. Furthermore, increased vascular permeability of the udder, the initial stage of a developing inflammatory reaction, seemed to be mediated largely by a system dependent on neutrophil leucocyte participation. The delayed inflammatory reaction in the neutropenic cows seemed to be initiated in the beginning stages by a system working independently of the neutrophil leucocyte.