Shedding of Salmonella Typhimurium in vaccinated and unvaccinated hens during early lay in field conditions: a randomised controlled trial

Abstract

BackgroundSalmonella vaccination is one of the control measure that farmers can use to reduce bacterial shedding in their flocks. This study aimed to examine the efficacy of the Vaxsafe® ST (Strain STM-1) attenuated live vaccine administered as ocular and oral doses followed by an intramuscular (IM) dose in rearing, in reducing contamination by Salmonellae of both eggs and the environment in the commercial multi-age cage layer sheds. A randomised controlled trial was conducted up to 26 weeks post last vaccine on two different multi-age caged egg farms.ResultsNo clinical symptoms were observed following IM administration of STM-1 during rearing. Following the first two STM-1 doses, both vaccinated and unvaccinated birds exhibited antibody titres below the positive cut-off value, however after IM administration of STM-1, antibody titres in the vaccinated group were above the cut-off value. Wild type Salmonella Typhimurium was not detected during the rearing of pullets. During production, the antibody titres were significantly higher in the vaccinated group at all sampling points during this trial. There was no significant difference in the prevalence of Salmonella (detected by culture and PCR method) between the vaccinated and unvaccinated groups on the egg belt and faeces in early lay. Wild-type Salmonella spp. were consistently found in dust samples. Quantitative PCR (qPCR) assay was able to differentiate between the live vaccine strain and wild type Salmonella. The load of wild-type Salmonella in shed environment was relatively low (1.3 log10 ± 0.48 CFU/m2 of surface area).ConclusionGiven that Salmonella Typhimurium and other serovars are able to survive/persist in the shed environment (such as in dust), regular cleaning and or removal of dust from shed is important. Use of the Vaxsafe® ST vaccine in multi-age flocks is “not an ultimate intervention” for reduction of Salmonella Typhimurium because of the complexities involved in achieving control, such as the efficacy of cleaning of sheds, the lack of resting periods between batches and the possible carry over of contamination from existing flocks. Hence implementation of more than one or several interventions strategies is essential.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1201-0) contains supplementary material, which is available to authorized users.

Onsite investigation at a mail-order hatchery following a multistate Salmonella illness outbreak linked to live poultry—United States, 2018

“…Adherence to recommendations intended to reduce Salmonella in the hatchery environment was lower than expected for a large, commercial mail-order hatchery for the categories of sanitation (15%), biosecurity (39%), quality assurance (40%), and education of consumers (50%). Some of these finding are also lower than what was previously noted in a survey of other hatcheries (Nakao et al, 2015; Sharma et al, 2018). Significant sanitation findings included the observation that beverages intended for human consumption were stored in the hatchery; employees consumed food and beverages on the table used for sexing chicks; the incubators are constructed of unsealed wood which cannot be sterilized; and the potable water source is an unchlorinated and unfiltered well.…”

“…(Brownell et al, 1969; Nakamura et al, 1993; Gast and Holt, 1998). In attempts to reduce Salmonella shedding, vaccinations are often used; however, research has shown that vaccines do not eliminate Salmonella from the environment (Sharma et al, 2018), thus, a multifactor approach is required for Salmonella reduction in poultry (Barton-Behravesh et al, 2014).…”

From hatch to egg grading: monitoring of Salmonella shedding in free-range egg production systems

“…The sample size calculations and sampling strategy of rearing sheds was conducted as designed for a previous study [23]. For Flock A, 1 week prior to placement of chicks, 10 litter and 10 dust swabs were collected and tested for Salmonella using culture methods.…”

Antibody‐mediated crosslinking of gut bacteria hinders the spread of antibiotic resistance

“…In particular, antibiotic treatment and vaccines inducing IgA production might have non-trivial interplays. In practice, vaccines protect the host, but may or may not reduce shedding of bacteria (Desin et al 2013;Sharma et al 2018). Reduction of shedding clearly hinders pathogen propagation.…”