Masters Theses

Date of Award

8-2018

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Oudessa Kerro Dego

Committee Members

Jun Lin, Gina M. Pighetti

Abstract

Bovine mastitis is the major cause of economic losses in dairy production worldwide. Staphylococcus aureus is a major causative agent that possesses multiple virulence factors responsible for successful colonization of mammary glands. Despite the adoption of current mastitis control measures, S. aureus continues to be one of the most prevalent mastitis pathogens throughout the world. Lysigin® (Boehringer Ingelheim Vetmedica, Inc, St. Joseph, MO) is a commercial S. aureus vaccine currently available in the US and Startvac® (Hipra, Girona, Spain) is a commercial S. aureus vaccine in Europe. Although some studies evaluated efficacy of these vaccines reported reduction in the duration and intensity of clinical signs, none of them prevent S. aureus intramammary infection (IMI) in either field trials or under controlled experimental studies. Because of the tendency of this organism to cause chronic IMI, treatment with antibiotics is of limited success. Therefore, there has been an increasing demand for alternative control measures, such as a vaccine to effectively prevent S. aureus IMI. The objectives of this study were to evaluate the immune responses and protection against S. aureus IMI in dairy cows vaccinated with Staphylococcus aureus surface proteins (SASP) and Staphylococcus chromogenes surface proteins (SCSP). A total of 18 pregnant Holstein dairy cows ranging from heifers to 3rd lactation cows were divided into three groups of 6 animals each. Animals in Groups 1 and 2 were vaccinated with 1.2 mg/dose of SASP and SCSP proteins with Emulsigen-D adjuvant, respectively. Animals in Group 3 were injected with PBS mixed with Emulsigen-D at equal proportion (1. 5 ml each) and used as control. Animals were vaccinated subcutaneously in the neck area during late lactation at 28 (D-28) and 14 (D-14) days before drying off, and at drying off (D0). Subsequently, each animal was challenged with S. aureus strain 60 by teat dipping in bacterial suspension at 107 CFU/ml culture medium. Results showed that vaccinated cows had increased milk and serum antibody titers and reduced bacterial shedding through milk. Interestingly, SCSP vaccine cross-protected against S. aureus clinical mastitis thus suggesting its potential as immunogenic antigens to control bovine S. aureus mastitis.

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