Experimental trial in heifers vaccinated with Staphylococcus aureus avirulent mutant against bovine mastitis

Evaluation of a new vaccine against Staphylococcus aureus mastitis in dairy herds of southern Chile. I. Challenge trial

“…These results are consistent with those described by Pellegrino et al (2008) who in a similar challenge trial found that bacterial counts in the milk of vaccinated heifers was slightly lower than in the non-vaccinated group, but there was no significant difference. According to these authors, the heavy inoculum used for challenge (1000 cfu/mL), as it was the case in our study, is very different from natural infection and it may have obscured the protective effect of vaccination.…”

“…Consequently, it was logical to expect an increase in somatic cell counts immediately after the challenge with S. aureus in both groups of animals; in the vaccinated group somatic cell counts returned to normality (< 200×10 3 cells/mL) after day 6 post challenge, however in the control group somatic cells remained relatively high (> 600×10 3 cells/mL) until the end of the follow-up period, probably because the udders of vaccinated animals were in a better health condition (table 1). Our results are consistent with those reported by Pankey et al (1985), Leitner et al (2003), and Pellegrino et al (2008). Although there was no significant difference in SCC between vaccinated and non-vaccinated groups, control animals ended the evaluation period with a numerically higher average count than vaccinated animals.…”

“…No adverse effects were observed in vaccinated animals and, therefore, we can assure that the vaccine was safe; a similar result was observed by Pellegrino et al (2008) in an experimental challenge trial involving four pregnant heifers vaccinated subcutaneously 30 and 10 days before calving with two doses of a S. aureus avirulent mutant strain. No systemic effects (fever or loss of appetite) were observed in any of the vaccinated or non-vaccinated heifers after challenge with S. aureus and, therefore, in this study fever cannot be considered indicative of intramammary infection.…”

“…Vaccination effect on milk production has been reported by other researchers as well. In a similar challenge trial conducted in Argentina, Pellegrino et al (2008) reported a mean daily milk yield from inoculated quarters 20% higher than the non-vaccinated group 21 days after challenge, although this difference was not statistically significant. A significantly higher milk yield in vaccinated cows when compared to non-vaccinated cows has also been reported by several other authors (Watson 1992, Bradley et al 2015.…”

Efficacy of vaccination and nisin Z treatments to eliminate intramammary Staphylococcus aureus infection in lactating cows

“…One reason for the poor clinical cure rates could be the intracellular location of S. aureus, such as in epithelial cells or macrophages, and its ability to survive antibiotic treatments (Tuchscherr et al, 2011). Consequently, antibiotic therapy is often ineffective in eliminating chronic udder S. aureus infections (Pellegrino et al, 2008). Furthermore, regulatory methods tend to limit the use of antibiotics in dairy cattle to reduce their residues in milk.…”