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Ten lactating goats were randomly assigned to two groups of five vaccinates and five controls. The vaccine was a heat-killed rough mutant strain of Escherichia coli (E. coli) J5 containing 1.5 × 109 organisms per ml in incomplete Freund's adjuvant. The vaccinated group received three 1 ml doses of vaccine 14 days apart. The control group received three 1 ml doses of incomplete Freund's adjuvant in a similar regimen. Seventeen days after the third dose of vaccine or Freund's adjuvant all goats were intramammarily (IM) challenged with 15 colony forming units of live virulent E. coli into each teat. Severe clinical signs such as depression, anorexia and prolonged recumbency were observed after challenge in the control goats. In vaccinated goats the signs were less severe, although they had some depression and anorexia for 36 h postchallenge. Body temperature of the animals in both groups increased after challenge with live E. coli. However, peak temperature was significantly lower in vaccinated goats compared with control goats. E. coli count in the milk of vaccinated goats was significantly lower compared with control goats after IM challenge. E. coli from the milk of vaccinated goats was removed more rapidly compared with control goats. Serum J5 antibody levels of vaccinated goats were significantly higher on Days 14, 21, 28, 35 and 42 after vaccination. After challenge a significantly higher serum J5 antibody level was observed in vaccinated goats at 12, 24, 48 and 72 h. Milk anti-J5 antibody levels were significantly higher on Day 28 after vaccination in vaccinated goats. This study concludes that J5 vaccine provides partial protection against E. coli intramammary challenge and goats can be used as an economic model for studying bovine mastitis. |
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