Masters Theses

Date of Award

12-2022

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Oudessa Kerro Dego

Committee Members

Jun Lin, Elizabeth Eckelkamp

Abstract

Bovine mastitis, an inflammation of the mammary gland, is the single most costly disease of dairy cattle. Staphylococci, a major bacteria that cause bovine mastitis, are commonly divided into two major groups: Staphylococcus aureus and non-aureus staphylococci (NAS), previously known as coagulase-negative Staphylococcus species (CNS). Current mastitis control programs are not fully effective against staphylococcal mastitis and antibiotics are not sustainable due to limited success and the emergence of antimicrobial resistant bacteria. Non-antibiotic sustainable control tools, such as effective vaccines, are critically needed. Our lab developed and evaluated Staphylococcus aureus surface associated protein (SASP) and Staphylococcus chromogenes surface associated protein (SCSP) based experimental vaccines. The objective of this study was to evaluate efficacy of SCSP and SASP vaccines against staphylococcal intramammary infection and mastitis via natural exposure over 300 days of lactation. A total of 45 pregnant Holstein dairy cows were randomly enrolled in the study in three groups of 15 (Group1), 16 (Group 2) and 14 (Group 3) cows. Cows in groups 1 and 2 were vaccinated with 1.2 mg of SASP and SCSP with Emulsigen-D® adjuvant respectively. Cows in group 3 (control) were injected with phosphate buffered saline (pH 7.4) with Emulsigen-D adjuvant. Cows were monitored for increase in antibody titers in serum and milk, milk yield, milk somatic cells count, mastitis, adverse reactions to the vaccinations, and S. aureus and non-aureus staphylococci count from milk over 300 days of lactation. Our results showed increased milk and serum anti-SASP and -SCSP antibody titers in vaccinated cows compared to controls. The incidence and incidence density of staphylococcal subclinical mastitis were reduced both at the cow (SCSP group) and quarter (SCSP and SASP) levels. Overall, the SCSP vaccine conferred higher protective effects compared to the control and SASP vaccinated groups. Anti-SASP and -SCSP antibody titers began to wane at about 120 DIM indicating the length of immunity is about 4 months. About 3 - 4 doses would be required over 300 days of lactation. In conclusion, with further optimization of vaccination regimen staphylococcal surface associated protein vaccines particularly SCSP is a promising vaccine for the control of staphylococcal mastitis in dairy cows.

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Dairy Science Commons

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