Protective immunity conferred by a DNA adenine methylase deficientSalmonella entericaserovar Typhimurium vaccine when delivered in-water to sheep challenged withSalmonella entericaserovar Typhimurium

• Published in: Vaccine 2011-04, Vol.29 (19), p.3571
• Main Authors: Mohler, VL, Heithoff, DM, Mahan, MJ, Walker, KH, Hornitzky, MA, Gabor, L, Thomson, PC, Thompson, A, House, JK
• Format: Article
• Language: English
• Subjects: Animals; Cytokines; Deoxyribonucleic acid; DNA; Drinking water; Environmental conditions; Factory farming; Feedlots; Health risks; Immunization; Infections; Livestock; Livestock production; Mortality; Neonates; Salmonella; Sheep; Studies; Vaccines
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2011.03.075

Stimulation of acquired immunity toSalmonellain livestock is not feasible in neonates (which can be infected within 24h of birth) and is challenging in feedlots, which typically source animals from diverse locations and vendors. Induction of innate immune mechanisms through mass vaccination of animals upon arrival to feedlots is an alternative approach. Transport, environmental conditions, changes in social grouping, and further handling during feedlot assembly are significant stressors. These factors, as well as concurrent exposure to a diversity of pathogens, contribute to the risk of disease. We have shown that oral immunization of calves with a modified liveSalmonella entericaserovar Typhimurium vaccine strain, which lacks the DNA adenine methylase gene (S.Typhimuriumdam), attenuates the severity of clinical disease, reduces fecal shedding, and promotes clearance of salmonellae following virulent homologous and heterologous challenge. This study examines the safety and efficacy of aS.Typhimuriumdamvaccine in sheep via oral delivery in drinking water (ad libitum), as a means to effectively vaccinate large groups of animals. Adult merino sheep were vaccinated in drinking water -28 days, -7 days and 24h pre and 24h post-virulentSalmonellaTyphimurium challenge which was administered via the oral route. Significant attenuation of clinical disease (temperature, appetite, and attitude) and reduction in mortality and virulentSalmonellaTyphimurium fecal shedding and tissue colonization was observed in animals that received the vaccine 28 and 7 days pre-challenge. Further, vaccination did not pose a risk to stock previously infected with virulent salmonellae as mortalities and clinical disease in sheep vaccinated prior to or following virulent challenge did not differ significantly from the non-vaccinated controls. The capacity ofS.Typhimuriumdamvaccines delivered in drinking water to protect livestock from virulentSalmonellachallenge offers an effective, economical, stressor freeSalmonellaprophylaxis for intensive livestock production systems.