**8. Prevention and control measures**

The fundamental basis for the control of NTS is food safety at every step from farm to fork. Even antibiotic treatment is not recommended in uncomplicated gastroenteritis cases as this condition is self-limiting. The list for preventive and control measures include good sanitation practices, safer food, and water handling methods, vaccination, public awareness, malaria control, and antiretroviral therapy programmes. To limit the number of infections arising as a result of animal contact it is advisable to wash hands properly after each animal contact, as in many cases the organism is in colonized state in animals without showing any sign and symptoms. Proper food cooking contributes to limit infections. Although irradiation technology has been approved by several health agencies like WHO, CDC, and European commission's Scientific Committee on Food, its use is partially implemented. Curtailment to the indiscriminate antibiotic usage in poultry feed along with better farm managerial practices leads to decreased multidrug resistant bacterial load. One health approach including multiple interventions is mandatory to enhance understanding, prevention, and control of NTS, as human health is completely related to the animal health and their environment. Adoption of different on-farm interventions strategies such as genetic selection of *Salmonella*resistant birds, regular flock testing, use of natural antimicrobial products such as prebiotics or probiotics and egg washing on farms can reduce infection. The incidences of NTS infections have been observed more in individuals suffering from malaria and HIV because of immune-compromised health status in such individuals. So, adoption of strategies, such as malaria control, and antiretroviral therapy programmes, will not only lower the chances of primary sufferings but will greatly reduce NTS infections also.

Vaccination could be considered as a potential tool to control NTS, but currently no licensed vaccine is available for this in humans. The available typhoidal vaccine does not provide protection against NTS infections. Vaccination in animals may limit transmission of the micro-organism to humans. With this objective researchers are trying different vaccine strategies on livestock for NTS prevention. It includes live attenuated vaccines, killed vaccines, and a combination of both. Oral administration of live attenuated *S.* Gallinarum to chickens prevented not only wildtype infections by *S.* Gallinarum but also infections by *S.* Enteritidis [64]. Delivery of a killed vaccine comprising three different *Salmonella* serogroups i.e. Typhimurium, Mbandaka and Orion to chickens resulted in significant reduction in bacterial load when compared to the unvaccinated groups [65]. Administration of live attenuated *S.* Typhimurium vaccine followed by a killed *Salmonella* serovars Berta and Kentucky into chickens, showed a significant decrease in *Salmonella* sp. in the vaccinated animals when compared to the unvaccinated group [66].

Subunit vaccine development may pave a better way towards control scheme. Such vaccines come with an advantage of raising a protective immune response by using only a part of the infectious micro-organism. Common sub-cellular components of *Salmonella* used for development of vaccines are outer membrane proteins (Omps), porins, toxins and ribosomal fractions. Such vaccines have been tried in different animals and have variable success rates [67–70]. Many of the cell surface carbohydrates of pathogenic bacteria like capsular polysaccharides are important antigenic determinants as in case of Vi-based vaccines against *S.*Typhi in humans. Omps are the surface exposed proteins which play a crucial role in pathogenic processes such as motility, adherence and colonization of the host cells, injection of toxins and cellular proteases, and formation of channels for the antibiotics removal [71]. Administration of Omps of *S.* Enteritidis can elicit high antibody responses and prevent bacterial shedding in chicken challenged with virulent *Salmonella* [72]. These functions make them attractive targets for the development of vaccines. *Salmonella* is an intracellular pathogen and generation of both B-cell and T-cell immune responses are essential. Live attenuated vaccines provide both humoral and cell mediated immune response; but, they may pose a risk in immunocompromised individuals. Whereas, inactivated vaccines induce only humoral immunity. Hence, the development of subunit vaccines after B-cell and T-cell epitope prediction and assessment of peptides with high affinity for class I and II MHC proteins are a better approach, and studies focussing this [73], increase the likelihood of developing a successful vaccine. Successful induction high levels of anti-porin antibodies and enhanced cell mediated immunity against *Salmonella* also have been demonstrated [74].
