Summer Mastitis in Hokkaido: Clinical and Pathological Findings in Mastitis Experimentally Induced withActinomyces pyogenesandPeptococcus indolicus

Abstract

Purulent mastitis occurred in 26 out of 46 quarters of 9-14-month-old heifers experimentally infected with a mixture ofActinomyces pyogenesandPeptococcus indolicus. The infection occurred in 17 out of 21 quarters, 5 out of 9 quarters, 2 out of 4 quarters and 2 out of 4 quarters by inoculation of the mammary gland, lactiferous sinus, muscles of the teat and cutis of the udder, respectively. Inoculation of the cutis of the teat and subcutis of the udder did not cause any disease. Infection in the estrogen-injected group and estrogen-uninjected group occurred in 13 out of 21 quarters and 13 out of 25 quarters, respectively. Systemic signs in the affected cases were pronounced within 1-3 weeks after inoculation. Inflammatory edema of the abdomen was seen in 3 out of 8 cases 1-2 weeks after inoculation, while inflammation such as redness, swelling, heat and pain, and presence of pus after squeezing of the udder were observed 1 week after, persisting for 8 weeks after inoculation. Indulation of the udder and absence of pus after squeezing of the udder were seen 1-2 weeks and 3 weeks after inoculation, respectively. Cutaneous fistulas of the udder were pronounced after 3-4 weeks. High protease serum antibody titre persisted for 8 weeks after inoculation in the affected cases. Pathologically, suppurative colliquation and fibrous proliferation in the mucosa of the lactiferous sinus and mammary gland, cutaneous fistulas of the udder and obliteration of the lactiferous sinus were pronounced in the affected quarters. As a result, the experiment was able to reproduce the same lesions as those found in spontaneous cases of summer mastitis.