FURTHER-STUDIES ON THE EFFICACY OF A LIVE VACCINE AGAINST MASTITIS CAUSED BY STREPTOCOCCUS-UBERIS

Three groups of diary cows were immunized by subcutaneous (s.c.) admin istration of a preparation of live Streptococcus uberis (strain 0140J) and an intramammary infusion of a soluble surface extract derived fro m same the bacteria. Animals in Groups 1 and 2 received two s.c. vacci nations plus an intramammary inoculation. Animals in Group 3 received two s.c. vaccinations but did not receive the intramammary infusion. I n addition to the vaccinated animals, each group also contained two no n-vaccinated (control) animals. All animals were challenged experiment ally by intramammary infusion (in two quarters per animal) of ca 100 c .f.u. of S. uberis (strain 0140J or C221) and monitored for clinical s igns of disease, bacterial numbers in milk, somatic cell count in milk , and daily milk yield for the following 10 days. Animals in Group 1 w ere challenged with strain 0140J. Only one out of six challenged quart ers of three vaccinated cows developed clinical disease compared to al l (four out of four) quarters of non-vaccinated cows. Animals in Group 2 were challenged with strain C221. All challenged quarters of three vaccinated (six out of six) and two non-vaccinated (four out of four) cows developed clinical mastitis. Animals in Group 3 were challenged w ith strain 0140J. Five out of eight quarters on four vaccinated co,vs developed clinical mastitis but the onset was delayed in comparison wi th that in both non-vaccinated cows in which four out of four challeng ed quarters developed clinical mastitis. These results indicated that vaccination with live S. uberis protects against challenge with the ho mologous strain but was less effective against a heterologous strain. Reduced protection,vas also seen when the intramammary booster was omi tted. (C) 1997 Elsevier Science Ltd.