A critical review ofSalmonellaTyphimurium infection in laying hens

Abstract

Salmonella Typhimurium has been reported to contaminate egg production across the world, but where Salmonella Enteritidis is endemic it is this latter serovar that dominates egg-borne salmonellosis. However, Salmonella Typhimurium is a major food-borne pathogen so it is important to understand how it can impact the microbiological safety of eggs and what serovar-specific control strategies may be appropriate in the future as control over Salmonella Enteritidis continues to improve. To that end, the present review examines the published literature on Salmonella Typhimurium in laying hens and eggs, with particular reference to comparative studies examining different serovars. Experimentally Salmonella Enteritidis is more often isolated from egg contents and seems to adhere better to reproductive tract mucosa, whilst Salmonella Typhimurium appears to provoke a more intense tissue pathology and immune response, and flock infections are more transient. However, it is observed in many cases that the present body of evidence does not identify clear differences between specific behaviours of the serovars Typhimurium and Enteritidis, whether in laying hens, in their eggs, or in the laying environment. It is concluded that further long-term experimental and natural infection studies are needed in order to generate a clearer picture.

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

“…The Australian poultry industry differs from most other countries in that Salmonella enterica serovar Enteriditis ( S . Enteriditis) is not endemic in chicken breeding and egg‐laying flocks 3, 4…”

“…A review of Salmonella infection in laying hens noted that most studies conducted with Salmonella colonisation in chickens have been short term (2 weeks) and used single administration of very high infective doses and that this may not reflect the situation for the whole productive life of a commercial layer hen 4. It could be argued that if a vaccine merely lowers organism numbers compared with controls for a short period but natural decline in organism presence is essentially the same after approximately 2 weeks, the vaccine has not really achieved a long‐term improvement compared with no treatment.…”

Scientific Opinion on the public health risks of table eggs due to deterioration and development of pathogens

“…Other S. Typhimurium DTs, such as DT104 and DT49, can infect chickens and cause egg contamination Williams et al, 1998;Okamura et al, 2010). The virulence and invasiveness of S. Typhimurium are also determined by the bacterial strain (Barrow et al, 1987;Keller et al, 1997;Okamura et al, 2010;Wales and Davies, 2011). For example, a study investigating the invasiveness and egg contamination potential of 10 S. Typhimurium DT104 strains has shown that they differed in their ability to cause ovarian infection and egg contamination (Okamura et al, 2010).…”

“…The success of S. Enteritidis in the transovarian transmission route can be associated with the presence in this serovar of the SEF14 fimbriae (which might be involved in the colonization of the reproductive organs), the presence of the yafD gene (which is essential for resistance in the albumen), and with the lipopolysaccharide structure, a key factor in oviduct persistence and survival in egg albumen (Lu et al, 2003;Coward et al, 2013), particularly at a hen body temperature of 41.5 °C (Coward et al, 2013). S. Typhimurium is able to colonize ovaries and internally contaminate eggs (Okamura et al, 2001a;Wales and Davies, 2011;Martelli and Davies, 2012). Other Salmonella serovars are rarely isolated from egg contents, but can infect the hen reproductive organs (Okamura et al, 2001a;Gast et al, 2004;Martelli and Davies, 2012).…”

Characterization of aSalmonellaTyphimurium ghost carrying an adjuvant protein as a vaccine candidate for the protection of chickens against virulent challenge

“…In South Korea, the prevalence of Salmonella Typhimurium is widely reported in the broiler and layer chicken farms or poultry products (Rayamajhi et al, 2010;Kim et al, 2012;Choi et al, 2014). Chickens infected with Salmonella Typhimurium appear asymptomatic, but continue to shed the pathogen for long periods of time, with rare cases of systemic disease (Wales & Davies, 2011). Human exposure to poultry or poultry products infected with Salmonella Typhimurium is a major risk factor for human infection (Cheong et al, 2007).…”