Comparison of the Prevalence of Salmonella Infection in Layer Hens from Commercial Layer Farms with High and Low Rodent Densities

College of Veterinary Medicine, University of the Philippines, Los Baños College, Laguna, 4031 Philippines.
Avian Diseases (Impact Factor: 1.24). 03/2012; 56(1):29-34. DOI: 10.1637/9704-030711-Reg.1
Source: PubMed


A comparison on the prevalence of Salmonella infection in layer hens from commercial layer farms with high and low rodent densities was investigated. Out of 280 laying hens sampled from three commercial layer farms with high rodent densities, Salmonella enterica subsp. enterica serovar Enteritidis (Salmonella Enteritidis) was isolated from 20 (7.14%) hens and Salmonella enterica subsp. enterica serovar Infantis (Salmonella Infantis) from three (1.07%) hens. In contrast, layer hens sampled from four commercial layer farms with low rodent densities were negative for any salmonellae. Significant differences (P < 0.05) in the isolation rates of Salmonella from various organs of infected layer hens were also noted. For Salmonella Enteritidis, liver (55.0%) and the oviduct (55.0%) had the highest isolation rates while all Salmonella Infantis isolates were from the oviduct. Pulsed field gel electrophoresis (PFGE) analysis of BlnI-digested chromosomal DNA of Salmonella Enteritidis isolated from layer hens and rodents showed similar patterns. PFGE analysis of Salmonella Infantis isolated from layer hens, rodents, eggs, and the environment yielded identical patterns. In this study, the significantly higher prevalence rate (P < 0.05) of Salmonella Enteritidis and Salmonella Infantis in layer hens from high rodent density farms could be attributed to the high rodent population density. The persistent Salmonella Enteritidis and Salmonella Infantis infection inside layer houses may have been amplified by the increasing numbers in the rodent population over the years, which increased the opportunity for environment-rodent-chicken interaction and the transmission of salmonellae to chickens. Monitoring of salmonellae from rodents inside poultry premises is recommended to be an effective additional tool in the assessment of the Salmonella status of layer flocks.


Available from: Dennis V. Umali
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    • "The persistence of environmental contamination in egg production facilities creates an important potential reservoir for introducing Salmonella Enteritidis infection into successive laying flocks (Dewaele et al., 2012a, b; Lapuz et al., 2012 ). Distributed widely throughout laying houses in association with dust and feces (Garber et al., 2003; Kinde et al., 2005), Salmonella Enteritidis contamination can be magnified by severe rodent or insect infestations to levels that will survive standard cleaning and disinfection procedures (Carrique-Mas et al., 2009b; Snow et al., 2010 ). "
    [Show abstract] [Hide abstract] ABSTRACT: Salmonella Enteritidis can be deposited inside eggs laid by infected hens, so the prevalence of this pathogen in commercial egg-producing flocks is an important risk factor for human illness. Opportunities for the introduction, transmission, and persistence of salmonellae in poultry are potentially influenced by flock housing and management systems. Animal welfare concerns have spurred the development of alternatives to traditional cage-based housing. However, the consequences of poultry housing systems for food safety have not been fully resolved by prior research. The present study assessed the effects of two different housing systems (conventional cages and colony cages enriched with perching and nesting areas) on the persistence of fecal shedding of Salmonella Enteritidis by groups of experimentally infected laying hens. In each of two trials, 136 hens were distributed among cages of both housing systems and orally inoculated with doses of 10(8) cfu of Salmonella Enteritidis (phage type 13a in one trial and phage type 4 in the other). At weekly intervals, samples of voided feces were collected from beneath each cage and cultured to detect Salmonella Enteritidis. Fecal shedding of Salmonella Enteritidis was detected for up to 8 wk post-inoculation by hens housed in enriched colony cages and 10 wk by hens housed in conventional cages. For both trials combined, the frequency of positive fecal cultures was significantly (P < 0.05) greater for conventional cages than for enriched colony cages at 1 wk (84.7 vs. 71.5%), 2 wk (54.2 vs. 31.3%), 3 wk (21.5 vs. 7.6%), and 4 wk (9.7 vs. 2.8%) post-inoculation. These results demonstrate that the susceptibility of hens to intestinal colonization by Salmonella Enteritidis can differ between conventional and enriched cage-based production systems, although this effect does not necessarily translate into a corresponding difference in the longer-term persistence of fecal shedding. © 2015 Poultry Science Association Inc.
    Full-text · Article · Apr 2015 · Poultry Science
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    [Show abstract] [Hide abstract] ABSTRACT: Rodents play a major role in the transmission and maintenance of Salmonella contamination cycles in poultry facilities. However, very limited field data are available regarding the transmission routes, infection cycle, and shedding patterns of Salmonella by naturally infected wild rodents from commercial layer farms. In this study, a total of 128 resident wild roof rats (Rattus ratus) were captured from a Salmonella-contaminated layer facility. All roof rats were divided into 51 laboratory cages, and weekly monitoring of Salmonella fecal shedding patterns was conducted for 53 wk. Seven roof rats from cages that were observed to frequently shed Salmonella were isolated in individual cages, and daily Salmonella monitoring was performed for 35 days. At the end of monitoring, each roof rat was euthanatized, and isolation of Salmonella from different organs was performed. Results of weekly monitoring of Salmonella showed that 21 of 51 cages (41.2%) were positive for Salmonella Infantis, while two cages (3.92%) were positive for Salmonella Enteritidis. Moreover, 11 cages were positive for Salmonella for at least two sampling weeks. Isolation of Salmonella from fecal droppings was mainly observed during the first 12 wk of captivity. The longest interval between two Salmonella-positive fecal dropping was 24 wk. In the daily Salmonella monitoring, only Salmonella Infantis was isolated from fecal droppings, in which the highest number of Salmonella Infantis organisms per fecal dropping was at 1 x 10(8) colony-forming units (cfu), while the lowest measured quantity was 1 x 10(3) cfu. It was noted that the frequency of Salmonella shedding in fecal droppings appeared to have a linear correlation (r = 0.85) with the number of Salmonella organisms (cfu) per fecal pellet (P < 0.05). Moreover, pulsed-field gel electrophoresis analysis of Salmonella Infantis isolates revealed a single identical pulsed-field pattern. Salmonella Enteritidis isolates from fecal droppings and internal organs also generated a single identical pulsed-field pattern. Interestingly, Salmonella Infantis was not isolated from any of the organs examined, while Salmonella Enteritidis was isolated from the spleen and liver of one roof rat. These results may indicate that wild roof rats could persistently carry Salmonella and contaminate commercial poultry facilities through intermittent fecal shedding. Moreover, Salmonella Enteritidis in wild roof rats appears to be more of a systemic infection, in which isolation is most likely to occur in internal organs, whereas Salmonella Infantis is more likely an enteric type of infection, in which isolation is most likely to occur in the intestinal contents. It is very plausible that layer chickens could become infected with Salmonella through ingestion of Salmonella-positive fecal droppings or feeds contaminated with these fecal droppings from infected resident roof rats. This is likely one of the major reasons why layer houses can be persistently infected by Salmonella even if the facilities are thoroughly cleaned and disinfected and if replacement stocks are obtained from Salmonella-free breeders and rearing units. It is therefore a noteworthy suggestion that rodent control programs inside poultry premises comprise an essential and effective tool in the management and control of Salmonella contamination in layer flocks.
    Full-text · Article · Jun 2012 · Avian Diseases
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    [Show abstract] [Hide abstract] ABSTRACT: In total, 40 commercial layer farms and 32 replacement pullet farms with a combined population of 7.5 million adult layers and 6.6 million replacement pullets from six prefectures in eastern Japan were investigated for Salmonella Senftenberg contamination. We randomly collected 17,956 environmental samples, 5816 feed samples, and 218,470 egg samples from commercial layer farms; and 427 feed samples and 2896 environmental samples from replacement pullet farms. We monitored all samples for Salmonella. Samples were primarily enriched in Hajna tetrathinoate broth for 24 hr at 37 C followed by incubation in desoxycholate hydrogen sulfide lactose agar for 18 hr at 37 C. Salmonella colonies were confirmed and identified by biochemical tests and serotyped using Salmonella O and H antigens. We recorded 171 environmental samples (0.95%) and 10 feed samples (0.17%) that were positive for Salmonella spp. in which 36 environmental samples (0.20%) and six feed samples (0.10%) were identified as Salmonella Senftenberg. All Salmonella Senftenberg strains were isolated from nine replacement pullet farms. No Salmonella Senftenberg strains were isolated from adult layer farms and from eggs. Pulse field gel electrophoresis of BlnI-digested chromosomal DNA of 19 Salmonella Senftenberg isolates from feeds and environmental samples yielded a single identical DNA pattern. Traceback information showed that all positive feed samples were from a single feed source. Timeline studies showed that Salmonella Senftenberg contamination occurred first mostly in the feeds and then spread to the environment and other farms. This study demonstrated that the prevalence of Salmonella Senftenberg contamination in commercial layer facilities in eastern Japan is very low. Moreover, feed contamination played a major role in the epizootiology and spread of this pathogen in commercial poultry flocks. Given the resilient and persistent nature of this particular Salmonella serotype, routine monitoring and strict quality control measures at the feed level are recommended to prevent the colonization of poultry facilities with Salmonella Senftenberg that may lead to future outbreaks.
    Full-text · Article · Sep 2012 · Avian Diseases
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