SUMMER MASTITIS EXPERIMENTALLY-INDUCED BY HYDROTAEA IRRITANS EXPOSED TO BACTERIA

Summer mastitis is an acute suppurative bacterial infection of the udd er in heifers and dry cows. To ascertain the possible role of flies in the transmission of the disease, experimental exposures of recipient heifers to Hydrotaea irritans previously exposed to bacteria were carr ied out. Flies were allowed to feed on secretions from clinical cases of summer mastitis. The pathogens present were the bacteria Staphyloco ccus aureus, Streptococcus dysgalactiae, Actinomyces pyogenes, Stuart- Schwan cocci, Peptococcus indolicus, Fusobacterium necrophorum and Bac terioides species. The teats of eight heifers were exposed to flies wi th verified pathogen content. Two teats of each animal were deliberate ly damaged before fly exposure. One teat was cut, another pricked with insect needles to mimic insect bites. Two of the heifers developed su mmer mastitis in the quarters where teats had been cut. The bacterial species isolated from these quarters corresponded to those that had pr eviously been fed to the flies. For the first time, it is now demonstr ated that H.irritans is capable of transmitting summer mastitis pathog ens and so causing summer mastitis in recipient heifers. Lesions on th e teat orifice may be a predisposing factor in the development of the disease.