Live and inactivated vaccine regimens against caecal Salmonella Typhimurium colonisation in laying hens

Abstract

ObjectiveIn Australia, Salmonella serovar Typhimurium (S. Typhimurium) is the predominant zoonotic serovar in humans and is frequently isolated from layer hens. Vaccination against this serovar has been previously shown to be effective in broilers and the aim of this current study was to assess and determine the best vaccination strategy (live or inactivated) to minimise caecal colonisation by S. Typhimurium.MethodsA long‐term experiment (56 weeks) was conducted on ISABROWN pullets using a commercial live aroA deleted mutant S. Typhimurium vaccine and an autogenous inactivated multivalent Salmonella vaccine (containing serovars Typhimurium, Infantis, Montevideo and Zanzibar). These vaccines were administered PO or by SC or IM injection, either alone or in combination. Pullets were vaccinated throughout rearing (to 18 weeks of age) and sequentially bled for antibody titre levels. The birds, vaccinated and controls, were challenged orally with a field isolate of S. Typhimurium at different ages, held for 21 days post‐challenge, then euthanased and their caeca cultured for the presence of Salmonella. ResultsNone of the oral live‐vaccinated groups exhibited lasting protection. When administered twice, the inactivated vaccine gave significant protection at 17 weeks of age and the live vaccine given by SC injection given twice produced significant protection at 17, 25 and 34 weeks.ConclusionsVaccination regimens that included parenteral administration of live or inactivated vaccines and thus achieved positive serum antibody levels were able to provide protection against challenge. Hence, vaccination may play a useful role in a management strategy for Salmonella carriage in layer flocks.

The Epidemiology of Salmonella enterica Outbreaks in Australia, 2001–2016

“…While there are state-based guidelines, there are no rules or restrictions on the use of raw eggs in ready-to-eat foods in Australia (Moffatt et al, 2016). As Australian states and territories have oversight of food safety regulation, some states have implemented control measures across the supply chain to try to reduce the burden of egg-related salmonellosis, including targeted communication and education for bakeries, mandatory training at retail level, industry food safety plans, and the vaccination of many laying flocks against S. Typhimurium (NSW Food Authority, 2007;Groves et al, 2016;Ford et al, 2018). Unlike in other countries where S. Enteritidis is more prevalent in eggs, S. Typhimurium caused most (84%) foodborne or suspected foodborne Salmonella spp.…”

Correlating bacterial shedding with fecal corticosterone levels and serological responses from layer hens experimentally infected with Salmonella Typhimurium

“…Previous literature stated that intestinal persistence of Salmonella Typhimurium in chickens was longer when birds were challenged at day old compared to day 7 and that older birds are considerably more resistant to salmonellae than are young chicks [ 41 , 42 ]. Our study indicated that infection of adult birds (14 weeks old in this study) can also result in continued harbouring of the Salmonella Typhimurium and intermittent faecal shedding.…”

A Long-Term Efficacy Trial of a Live, Attenuated Salmonella Typhimurium Vaccine in Layer Hens

“…For a vaccine to be highly successful in a layer hen environment, it should also reduce the total bacterial load shed in feces, thus reducing the overall abundance of Salmonella in the environment in which eggs are laid. Furthermore, few studies in layer hens have trialed the effectiveness of live, attenuated vaccine strains over a commercially relevant period ( Hassan and Curtiss, 1997 ; Groves et al, 2016 ).…”

“…Vaccination of poultry with the aroA mutant has been shown to elicit IgG, IgM, and IgA responses ( Alderton et al, 1991 ) and has been shown to provide protection against wild-type challenge ( Barrow et al, 1990 ; Alderton et al, 1991 ). Mode of inoculation has, however, been shown to have an effect on the strength of the antibody response and the protective effect of the vaccine ( Groves et al, 2016 ). Currently, there is limited knowledge regarding the long-term efficacy of Salmonella vaccines at mitigating shedding over the productive life span of a layer hen, which can exceed 60 weeks of age.…”