Protective effect of previous intramammary infection with Streptococcus uberis against subsequent clinical mastitis in the cow

Following challenge of 23 quarters of 17 lactating cows with 10 3 colony forming units of Streptococcus uberis 0140J, 20 (87 per cent) developed clinical mastitis. Once the disease had resolved each animal was rechallenged in two quarters, one previously challenged and one additional quarter. Of the 34 secondary quarter challenges 11 (32·2 per cent) led to clinical mastitis, a highly significant reduction over the primary challenges.