**8.2 Autogenous vaccine against** *S. aureus* **mastitis**

These vaccines are the preparations having specific strains of bacteria obtained from mastitis suffered by animals and used to immunize the herd for protection against further new udder infections with the same strain of bacteria. There are evidences which shows that the use of autogenous *S. aureus* vaccines enhances antibody titer in vaccinated animals as compared to non-vaccinated herd and reduce the risk of both clinical and sub-clinical mastitis [71]. Some studies also show that autogenous vaccines provide almost 70% protection from infection and provide protection from clinically ill mastitis cases challenged with *S. aureus* [80].

Early studies suggest that vaccines for *S. aureus* will increase cure rate and lower SCC but in actuality, it does not work against adult cows. Experimental success was also seen with commercial *S. aureus* vaccine Lysigin® in the young dairy animals. When serum samples from vaccinated animals were checked they showed higher antibody titer as compared to non-vaccinated animals to combat against *S. aureus* infections [71]. So experimental and commercial preparations of *S. aureus* vaccine

provide protection against mastitis. Efficacy of these preparations against *S. aureus* ranges between 44%–66% and this strategy for prevention of *S. aureus* in the future, some new antigens and adjuvants are added to the vaccine preparations to enhance their effectiveness [72, 84].

#### **8.3 Vaccine response in vaccinated dairy animals**

*Staphylococcus aureus* is a predominant organism causing mastitis in different species. So, different experiments were conducted in different animal species to determine vaccine efficacy. The production and implementation of *S. aureus* vaccine in milk animals has a great impact towards public health. Inactivated vaccine was prepared and checked by using different adjuvants against *S. aureus* [85].

She camel having sub-clinical mastitis, vaccinal isolates were taken from her having alpha and beta hemolysin toxin, also some were multidrug resistant. Inactivated alum precipitated *S. aureus* vaccine (APSV) and oil adjuvant *S. aureus* vaccine (OASV) were prepared after confirming its antigenicity in rabbits. Experiments showed that APSV and OASV were safe, effective and expressed immunogenic responses in experimental rabbits [86, 87].

*S. aureus* is a major cause of mastitis in dairy cows causing mild to severe and chronic infections having drastic effects on cow's wellbeing, lifespan and milk production. Irrespective of years of research on mastitis issues still there is no production of an effective vaccine against *S. aureus mastitis.* Experimental studies showed that it's possible to vaccinate *S. aureus* naïve cattle and also this experimental immunization leads to humoral immune response which is different from response that occurs after natural exposure [79, 88].

Experiments are still in progress for the use of vaccine against *S. aureus* mastitis in small ruminants. Still, there is gap in using mastitis vaccine for prevention of *S. aureus* mastitis which is a major issue in dairy industry and causes huge economic losses every year. Perhaps there might be bright future for farmers because trails of mastitis vaccine in lab animals are showing satisfactory results, which is a hope [43, 50].

#### **8.4 Vaccine success rate**

Mastitis is one of the most dangerous disease of dairy industry. Vaccination and other managemental practices are the tools to prevent mastitis caused by contagious as well as environmental pathogens. The success rate of immunization depends upon type of vaccine, adjuvant used and route of administration of vaccination regardless of type of vaccine, only vaccine is not enough in the large herds with high mastitis cases. For achieving success, it is necessary to use up to date manage mental practices along with vaccine and culling of chronically ill cases to reduce intra mammary infections [50, 89].

Experiments conducted from last 15 decades show that experimental *S. aureus* vaccines as well as commercial vaccines reduce new infections in dairy heifers. *S. aureus* vaccine was prepared by focusing on two major components of *S. aureus* (pseudo-capsules and alpha toxins). 2 and 4 weeks before calving heifers were given injections in the supra-mammary lymph node of mammary glands. Injections were given subcutaneously. After caving these heifers were challenged with *S. aureus* infections. These heifers showed 46% reduction in *S. aureus* infections as compared with control group of animals. There was almost 70% success rate from infection in vaccinated animals and less than 10% in non-vaccinated animals. Clinical signs of mastitis were also mild in vaccinated herds compared to control group of animals [6, 72].
