Influence of On‐farm pig Salmonella status on Salmonella Shedding at Slaughter

The risk of Salmonella shedding among pigs at slaughter with regard to their previous on‐farm Salmonella status was assessed in a group of pigs from a farm from NE of Spain. A total of 202 pigs that had been serologically monitored monthly during the fattening period and from which mesenteric lymph nodes (MLN) and faecal (SFEC) samples were collected at slaughter for Salmonella isolation were included. A repeated‐measures anova was used to assess the relationship between mean OD% values during the fattening period and sampling time and bacteriology on MLN and SFEC. Pigs were also grouped into four groups, that is pigs seronegative during the fattening period and Salmonella negative in MLN (group A; n = 69); pigs seronegative during the fattening period but Salmonella positive in MLN (B; n = 36); pigs seropositive at least once and Salmonella positive in MLN (C; n = 50); and pigs seropositive at least once but Salmonella negative in (D; n = 47). Pigs shedding at slaughter seroconverted much earlier and showed much higher mean OD% values than non‐shedders pigs. The proportion of Salmonella shedders in groups A and D was high and similar (26.1% and 29.8%, respectively), but significantly lower than that for groups B and C. The odds of shedding Salmonella for groups B and C were 4.8 (95% CI = 1.5–15.5) and 20.9 (3.7–118) times higher, respectively, when compared to A. It was concluded that a large proportion of Salmonella seronegative pigs may shed Salmonella at slaughter, which would be likely associated to previous exposure with contaminated environments (i.e. transport and lairage). For pigs already infected at farm, the likelihood of shedding Salmonella was much higher and may depend on whether the bacterium has colonized the MLN or not. The odds of shedding Salmonella spp. were always much higher for pigs in which Salmonella was isolated from MLN.     

Looking for new approaches for the use of serology in the context of control programmes against pig salmonellosis

Most swine Salmonella national control programmes in Europe have been based on the categorization of herds according to risk levels based on serological results. However, none of the non‐Scandinavian countries have reported of any significant success on Salmonella infection reduction in fattening pigs or the number of human cases attributable to pigs or pork. The limited accuracy of the tests used, the small number of animals sampled and the likely lack of herd representativeness of the samples used could be major factors affecting the suitability of these programmes. Focusing on minimizing Salmonella shedding at slaughter appears more important to prevent human infections than focusing on detection of seropositive pigs/herds at this stage. This study assessed whether performing on‐farm serology may help to predict shedding at slaughter. Between 2010 and 2016, pigs from six cohorts from a Salmonella‐positive herd were bled at 30, 60 and 90 days on fattening and before slaughter, and faecal samples collected at slaughter. Serology on days 60, 90 and before slaughter predicted somewhat shedding at slaughter with no significant differences among them. Pigs with higher OD% values at these point times would have higher risk of shedding when arriving to slaughter. The probability of shedding for a pig sampled on day 90 and showing an OD% value of 10 was 43%, and the risk increased up to 65% if the OD% was 40. Concluding, on‐farm serology may help to determine to some extent the risk of Salmonella shedding at slaughter from seropositive fattening units, which would allow for prompt on‐farm and slaughter interventions to reduce the likelihood of slaughter contamination with Salmonella.     

Evaluation of protection conferred by a Salmonella Typhimurium inactivated vaccine in Salmonella-infected finishing pig farms

The efficacy of an inactivated S. Typhimurium vaccine administered to pigs at the beginning of the fattening period was evaluated in four clinical trials (trials A, B, C and D). Faecal shedding and the systemic antibody response during fattening, as well as, the cecal contents and mesenteric lymph nodes collected after slaughtering were used to assess the outcome. Salmonella shedders prevalence in the control groups was six times higher than in the treated groups in trials A and D, both herds infected by S. Typhimurium. The risk of positive pens was also four or five times higher for the pens housing control pigs in trials A and C. Lower prevalence of Salmonella was observed in the slaughter samples from the vaccinated pigs in trial D and in the cecal content samples in trial A, when just the S. Typhimurium results were compared. The results suggest the effective homologous protection of the vaccinated pigs; however, the high humoral response elicited in the vaccinated pigs complicates their use in farms under serological surveillance programmes.     

Meat Juice Serology and Improved Food Chain Information as Control Tools for Pork‐Related Public Health Hazards

The seroprevalence of Salmonella spp., pathogenic Yersinia spp., Toxoplasma gondii and Trichinella spp. was studied in 1353 finishing pigs from 259 farms that were allocated according to farm types: large fattening farms (≥1000 pig places), small fattening farms (< 1000 pig places) and farrow‐to‐finish farms. The antibodies were analysed with commercial ELISA kits in meat juice samples that were collected at Finnish slaughterhouses. Salmonella antibodies were rare (3% of pigs, 14% of farms) when the cut‐off optical density (OD) value 0.2 was used. Antibodies to pathogenic Yersinia spp. and T. gondii were detected in 57% of pigs and 85% of farms (OD ≥0.3) and in 3% of pigs and 9% of farms (OD ≥0.15), respectively. No antibodies to Trichinella spp. were detected (OD ≥0.3). The European Food Safety Authority (EFSA) considers Salmonella spp., Yersinia enterocolitica, T. gondii and Trichinella spp. as the most relevant biological hazards in the context of meat inspection of pigs. The seroprevalence of these important zoonotic pathogens was low in Finland, except that of Yersinia. The seroprevalence of Toxoplasma was significantly higher in pigs originating from small‐scale fattening farms (P < 0.05). Strong positive correlation was observed at the animal level between Salmonella and Yersinia seropositivity and between Salmonella and Toxoplasma seropositivity (P < 0.05). We suggest that these results reflect the level and importance of biosecurity measures applied on the farms. Meat juice serology at slaughter is a useful tool for targeting measures to control these pathogens. The information obtained from analyses should be used as part of the food chain information (FCI).     

Herd-level risk factors for faecal shedding of Salmonella enterica in Spanish fattening pigs

Herd-level risk factors for faecal shedding of Salmonella enterica were investigated in a cross-sectional study on Spanish finishing units. For this purpose, 10 faecal samples were collected from 10 different pens containing pigs close to market weight in a total of 232 fattening units. The total sample size was proportionally distributed according to the fattener census in each of the regions and provinces of the country in order to ensure a sample representative of the entire swine population. All samples were individually examined by culture of 25 g of faecal material. Data regarding characteristics and management of each fattening unit were collected by means of a questionnaire. Logistic regression was used to detect relationships between the detection of faecal shedding of S. enterica and potential herd-level risk factors. The feeding of pelleted feed was associated with an increased risk of culture-positive faecal samples (OR = 2.28; 95% CI: 1.22, 4.26). The odds of a farm being Salmonella positive were associated with its size. Fattening units that slaughtered more than 3500 pigs per year had a higher risk for Salmonella faecal shedding (OR = 1.78; 95% CI: 0.96, 3.31). Interventions at these two points should be considered when designing or managing growing pig facilities to reduce Salmonella faecal shedding by fatteners.     

A longitudinal observational study of Salmonella shedding patterns by commercial turkeys during rearing and fattening,showing limitations of some control measures

1. The onset and progression of Salmonella infections was investigated in commercial turkey flocks from placement at 1 d old until slaughter in “brood and move” systems using a longitudinal observational approach based on faeces and environmental sampling with subsequent culture of Salmonella.

2. Persistent Salmonella Newport contamination was found within rearing houses and on their external concrete aprons after cleaning and disinfection between crops of heavily shedding young birds.

3. Salmonella shedding was often detected by 5 d of age and the frequency of positive samples peaked at 14–35 d. Thereafter Salmonella isolations declined, especially in the later (fattening) stages. Samples were still Salmonella-positive at low prevalence in half of the intensively sampled houses at slaughter age.

4. A number of management interventions to combat Salmonella infection of flocks, including sourcing policy, competitive exclusion cultures and cleaning and disinfection, were inadequate to prevent flock infection, although improved disinfection on one unit was associated with a delay in the onset of flock infection.

     

An investigation of shedding and super‐shedding of Shiga toxigenic Escherichia coli O157 and E. coli O26 in cattle presented for slaughter in the Republic of Ireland

Shiga toxigenic Escherichia coli (STEC) are an important group of pathogens and can be transmitted to humans from direct or indirect contact with cattle faeces. This study investigated the shedding of E. coli O157 and O26 in cattle at the time of slaughter and factors associated with super‐shedding (SS) animals. Rectoanal mucosal swab (RAMS) samples were collected from cattle (n = 1,317) at three large Irish commercial beef abattoirs over an 18 month period, and metadata were collected at the time of sampling regarding farm of origin, animal age, breed and gender. RAMS swabs were examined for the presence and numbers of E. coli O157 and O26 using a previously developed quantitative real‐time PCR protocol. Samples positive by PCR were culturally examined and isolates analysed for the presence of stx subtypes, eae and phylogroup. Any samples with counts >10⁴ CFU/swab of STEC O157 or O26 were deemed to be super‐shedders. Overall, 4.18% (55/1,317) of RAMS samples were positive for STEC O157, and 2.13% (28/1,317) were classified as STEC O157 SS. For STEC O26, 0.76% (10/1,317) of cattle were positive for STEC O26, and 0.23% (3/1,317) were classified as super‐shedders. Fewer STEC shedders and SS were noted among older animals (>37 months). There was a seasonal trend observed for STEC O157, with the highest prevalence of shedding and SS events in the autumn (August to October). The majority of E. coli O157 (50/55) isolates had stx2 and were eae positive, with no significant difference between SS and low shedders (LS). Interestingly, all STEC O26 (n = 10) were eae negative and had varied stx profiles. This study demonstrates that, while the overall shedding rates are relatively low in cattle at slaughter, among positive animals there is a high level of SS, which may pose a higher risk of cross‐contamination during slaughter.     

Prevalence and Characterization of Salmonella Isolated from Feral Pigs Throughout Texas

Feral pigs are one of the most abundant free‐roaming ungulates in the United States, yet their role in the ecology and transmission of foodborne pathogens is poorly understood. Our objectives were to estimate the prevalence of Salmonella shedding among feral pigs throughout Texas, to identify risk factors for infection, and to characterize the isolates. Faecal samples were collected from feral pigs in Texas from June 2013 through May 2015. Standard bacteriologic culture methods were used to isolate Salmonella from samples, and isolates were characterized via serotyping and anti‐microbial susceptibility testing. The prevalence of faecal Salmonella shedding among sampled pigs was 43.9% (194/442), with positive pigs originating from 50 counties. Pigs sampled during fall and summer were significantly more likely to be shedding Salmonella than pigs sampled during winter. High serovar diversity was evident among the isolates, and many of the detected serovars are leading causes of human salmonellosis. The most common serovars were Montevideo (10.0%), Newport (9.1%), and Give (8.2%). Resistance to anti‐microbial agents was rare. The burgeoning feral pig population in the United States may represent an emerging threat to food safety.     

Evaluation of Faecal Salmonella Shedding Among Dogs at Seven Animal Shelters across Texas

Estimates of prevalence of faecal Salmonella shedding among dogs in the United States have varied widely. Surveillance among shelter dogs has been limited, although dogs in animal shelters may be at elevated risk of Salmonella infection because of their previous exposure history as well as factors inherent to shelter environments. Our objectives were to estimate the prevalence of Salmonella shedding among shelter dogs across Texas, to identify risk factors for shedding and to characterize the isolates. Using a repeated cross‐sectional study design, we collected faecal samples from dogs on two or three visits to each of seven Texas animal shelters between May 2013 and December 2014. Standard bacteriologic culture methods were used to isolate Salmonella from samples, and isolates were characterized via serotyping and anti‐microbial susceptibility testing. The prevalence of faecal Salmonella shedding among sampled dogs was 4.9% (27/554), and within‐shelter prevalence ranged from 1.9% to 8.3%. There was a marginal association (P = 0.09) between watery faecal samples and positive Salmonella status, as estimated by a logistic regression model that controlled for shelter as a random effect. However, over 60% of Salmonella‐positive dogs had grossly normal faeces. Salmonella prevalence did not vary significantly by age group or sex. The most common serovars were Newport (22%) and Javiana (15%), both of which were widespread among shelters. Resistance to anti‐microbial agents was uncommon. The prevalence of faecal Salmonella shedding among shelter dogs in Texas appears to be comparable to that seen among pet dogs in general.     

Prevalence and Characteristics of Salmonella in the Beef Chain in the Republic of Ireland

The study investigated the prevalence, concentration and characteristics of Salmonella spp. in the Irish beef chain. A total of 900 samples including bovine hides, carcasses and ground beef were examined for the pathogen over a 2‐year study (July 2007–June 2009). Salmonella prevalence was low in all sample types; bovine hide (0.75%, 3 of 400); carcasses (0.25%, 1 of 400); and ground beef (3%, 3 of 100). All positive samples contained the pathogen in low concentrations (<10 CFU per cm² or per g). Serovars recovered were S. Dublin from hide and carcasses and S. Braenderup in ground beef. All isolates were susceptible to 13 anti‐microbials. The study highlights that Salmonella can be found at low levels at all stages of beef chain production, processing and retail and that there is a need for multiple hurdle interventions and practices along the beef chain, which will reduce consumer exposure to this pathogen.     

A Cross‐Sectional Study Examining Campylobacter and Other Zoonotic Enteric Pathogens in Dogs that Frequent Dog Parks in Three Cities in South‐Western Ontario and Risk Factors for Shedding of Campylobacter spp.

An estimated 6 million pet dogs live in Canadian households with the potential to transmit zoonotic pathogens to humans. Dogs have been identified as carriers of Salmonella, Giardia and Campylobacter spp., particularly Campylobacter upsaliensis, but little is known about the prevalence and risk factors for these pathogens in pet dogs that visit dog parks. This study examined the prevalence of these organisms in the faeces of dogs visiting dog parks in three cities in south‐western Ontario, as well as risk factors for shedding Campylobacter spp. and C. upsaliensis. From May to August 2009, canine faecal samples were collected at ten dog parks in the cities of Guelph and Kitchener‐Waterloo, Ontario, Canada. Owners were asked to complete a questionnaire related to pet characteristics and management factors including age, diet and activities in which the dog participates. Faecal samples were collected from 251 dogs, and 189 questionnaires were completed. Salmonella, Giardia and Campylobacter spp. were present in 1.2%, 6.4% and 43.0% of faecal samples, respectively. Of the Campylobacter spp. detected, 86.1% were C. upsaliensis, 13% were C. jejuni and 0.9% were C. coli. Statistically significant sparing factors associated with the shedding of Campylobacter spp. included the feeding of a commercial dry diet and the dog's exposure to compost. Age of dog had a quadratic effect, with young dogs and senior dogs having an increased probability of shedding Campylobacter spp. compared with adult dogs. The only statistically significant risk factor for shedding C. upsaliensis was outdoor water access including lakes and ditches, while dogs >1 year old were at a lower risk than young dogs. Understanding the pet‐related risk factors for Campylobacter spp. and C. upsaliensis shedding in dogs may help in the development of awareness and management strategies to potentially reduce the risk of transmitting this pathogen from dogs to humans.     

Contamination of Salmonella spp. in a pig finishing herd, from the arrival of the animals to the slaughterhouse

The aim of the present study was to investigate the contamination sources and the transmission of Salmonella within a pig finishing herd in Italy. Nine sets of samples were collected during the fattening period from cleaned and disinfected pens, animals at different ages (4 days after arrival, 90, 150, 170 and 240 days of age) and at slaughter. Salmonella was isolated from cleaned pens, individual faecal samples, the truck used to transport the pigs to the abattoir and after slaughter (cecal contents, mesenteric lymph nodes and carcasses). Several serovars were isolated: Salmonella typhimurium and Salmonella derby on farm; Salmonella bovismorbificans, Salmonella bredeney, Salmonella blockley, Salmonella hadar and Salmonella corvallis from the truck; S. derby, S. hadar, S. bredeney, S. bovismorbificans and Salmonella infantis at slaughter. Antibiotic resistance of the strains was tested and PFGE was carried out to investigate the on-farm epidemiology of Salmonella. The results showed that the environmental contamination may have represented a major source of infection for the pigs both on farm and during transport to the abattoir.     

Prevalence of enteric non‐typhoidal Salmonella in humans in the Middle East and North Africa: A systematic review and meta‐analysis

To enhance efforts related to controlling foodborne pathogens in the Middle East and North Africa (MENA), information on epidemiology of non‐typhoidal Salmonella enterica (hereafter termed “Salmonella”) is limited. We quantified the overall regional and country‐specific Salmonella prevalence in different human populations and identified the most common serotypes. Published literature of Salmonella prevalence was systematically reviewed and reported following the Preferred Items for Systematic Reviews and Meta‐Analysis (PRISMA) guidelines. Pooled Salmonella prevalence measures were estimated using a random‐effects model. We identified 46 research reports that reported 84 Salmonella prevalence measures in 15 out of 24 countries in MENA. There were 252,831 tested humans with 6,356 Salmonella‐positive cases. The pooled Salmonella prevalence in MENA was estimated at 6.6% (95% confidence interval (CI): 5.4%–7.9%). The highest pooled Salmonella prevalence measures were in Morocco (17.9%, 95% CI: 5.7%–34.8%, 1997–2012), Tunisia (10.2%, 95% CI: 4.3%–18.0%, 1988–2009) and Sudan (9.2%, 95% CI: 6.5%–12.2%, 2006–2008), while the lowest were in Jordan (1.1%, 95% CI: 0.1%–3.0%, 1993–2010), Oman (1.2%, 95% CI: 1.2%–1.3%, 1998–2002) and Palestine (1.2%, 95% CI: 0.4%–2.1%, 1999–2011). In MENA, Salmonella pooled prevalence in gastrointestinal symptomatic, gastrointestinal asymptomatic and food handlers population groups was 13.0% (95% CI: 7.6%–19.6%), 11.4% (95% CI: 2.2%–25.7%) and 3.8% (95% CI: 1.0%–8.0%), respectively. Salmonella prevalence was 14.5% (95% CI: 8.7%–26.1%) in studies tested <100 subjects, whereas 4.6% (95% CI: 3.6%–5.8%) in studies tested ≥100 subjects. Salmonella Enteritidis (29.8%) and Typhimurium (23.6%) were the most common serotypes. Salmonella was a common foodborne pathogen in MENA countries, particularly in North African countries. Findings inform the scientific community, the public and the decision‐makers with Salmonella prevalence and gaps in evidence in MENA to support control and prevention strategies and could leverage more research studies.     

Infections with Mycoplasma hyopneumoniae and Actinobacillus pleuropneumoniae in fattening pigs. Influence of piglet production systems and influence on production parameters

Two hundred and sixty-four feeder pigs from an age-segregated herd (A-pigs) and 264 feeder pigs from a continuous production system (C-pigs) were transferred into identical but separate rooms in a fattening herd employing all-in all-out production. On arrival, none of the A-pigs and 39% of the C-pigs were seropositive to Mycoplasma hyopneumoniae (M. hyo). At slaughter 30% of the A-pigs and 99% of the C-pigs were seropositive to M. hyo. Pigs with acute swine enzootic pneumonia (SEP) at slaughter and pigs that seroconverted to M. hyo late in the rearing period showed a lower growth rate compared with pigs with chronic SEP or pigs that seroconverted to M. hyo early or not at all. No A-pigs and 12% of the C-pigs were seropositive to Actinobacillus pleuropneumoniae 2 (A. pp 2) at arrival to the fattening herd. At slaughter, 10% of the A-pigs and 13% of the C-pigs were seropositive to A. pp 2. On arrival, the prevalence of pigs seropositive to A. pp 3 was lower among A-pigs than C-pigs. During the fattening period the situation was reversed. The prevalence of pleuritis at slaughter was low (2.7-4.2%) and there were no associations between pleuritis at slaughter and developments of antibodies to A. pp 2 or 3. However, pigs with pleuritis developed antibodies to M. hyo to a greater extent than pigs without pleuritis. Pigs with pleuropneumonia at slaughter and pigs that seroconverted to A. pp 2 or 3 had, during certain periods of the rearing, higher growth rates compared with pigs without pleuropneumonia or pigs that did not seroconvert to A. pp 2 or 3.     

Fecal Shedding of Salmonella in Horses Admitted to a Veterinary Teaching Hospital

Fecal samples were collected from 724 horses admitted to, and 232 horses hospitalized at, a veterinary teaching hospital between October 2000 and June 2001, and cultured for Salmonella. Salmonella was isolated on 24 occasions from 12 horses. S. Newport was the most commonly isolated serotype. The estimated prevalence (95% confidence interval [CI]) of Salmonella shedding on admission was 0.5% (0.1, 2.0). The estimated incidence rate of Salmonella shedding during hospitalization was 4.3% (95% CI, 2.2-8.1). The highest incidence of Salmonella shedding during hospitalization occurred during June 2001, but no significant (P > .5) temporal clusters of horses shedding Salmonella were detected.Horses shed Salmonella in their feces at a low rate. Horses shedding Salmonella occurred only sporadically and no obvious serotype pattern was observed. The occurrence of fecal shedding probably reflected the prevalence of inapparent Salmonella infection in the hospital source population, providing a baseline against which future potential outbreaks can be identified.

Introduction

Infection of horses by Salmonella organisms is a serious health issue. It is particularly troubling when outbreaks occur in hospitalized patients because these outbreaks can result in substantial economic losses and have a major impact on the welfare of patients.[1] Establishments with a high-density of horses, including veterinary teaching hospitals (VTHs) and private veterinary clinics, [1 and 2] are most vulnerable to outbreaks of disease attributable to Salmonella infection. Host susceptibility and environmental persistence of Salmonella are also factors contributing to outbreaks.Estimates of the prevalence of Salmonella-shedding horses admitted to veterinary hospitals have generally been made under outbreak conditions.[1] For example, between 1971 and 1982, 245 hospitalized horses (1.7%) at the University of California were found to shed Salmonella.[3 and 4] Three major outbreaks occurred during the study period, with no apparent periodicity. Between 1996 and 1999, 35 hospitalized horses (5.5%) at the Michigan State University were found to shed Salmonella.[5] One major outbreak occurred during the study period. Only one national survey of nonhospitalized horses in the United States for Salmonella infection has been undertaken: the prevalence of fecal shedding of Salmonella was estimated to be 0.8%, and the farm prevalence of shedding was 1.8%.[6]Many factors have been associated with the risk of Salmonella isolation from hospitalized horses, including diarrhea, fever, change in diet, large colon impaction, colic, withholding feed, feeding bran mash, antibiotic treatment, intubation with nasogastric tubes, and average daily ambient temperature.[7, 8, 9 and 10] Many of theses factors are thought to operate primarily through the effect of stress, increasing the susceptibility of horses to infection. Also, if a horse is infected by Salmonella but not shedding the organisms in its feces, the presence of stressors may reactivate fecal shedding. Most studies that have been conducted on risk factors for Salmonella shedding in horses have included horses with clinical salmonellosis, with or without inclusion of horses inapparently infected by Salmonella.[7, 8 and 10] Risk factors for Salmonella fecal shedding versus clinical salmonellosis have not been clearly delineated.An outbreak (epidemic) of disease can be defined as “an occurrence of disease in excess of its anticipated frequency.”[11] To more effectively identify future outbreaks of Salmonella infection in hospitalized horses, it is necessary to have accurate estimates of the prevalence of endemic fecal shedding of Salmonella in horses admitted to VTHs, and the incidence of fecal shedding during hospitalization. The aims of this study were to estimate the prevalence of fecal shedding in horses admitted to a VTH, to estimate the incidence of fecal shedding during hospitalization, and to describe the seasonal distribution of fecal Salmonella-shedding prevalence and incidence.

Materials and Methods

Study Design

Fecal samples were collected from horses admitted to the Purdue University VTH between October 12, 2000 and June 30, 2001. Horses admitted as inpatients were sampled at least on the day of admission, the day after admission, the day of discharge, and once or more in between. All horses admitted to the VTH during the study period were eligible to be sampled. In the case of mares accompanying sick foals, samples were also collected from the mare. Fecal samples were collected generally from freshly voided fecal material in stalls. Samples were stored at 4°C for up to 24 hours before processing.

Data Collection

For all horses included in the study, date of examination (outpatients) or date of hospitalization (inpatients) was recorded. For inpatients, date of discharge or date of death was also recorded. Horse characteristics were recorded as part of each horse's medical record, and included date of birth, sex (mare, stallion, gelding), and specific breed. The outcome of each admission (discharged alive, died, euthanized) and whether a necropsy was performed were also recorded. The number of samples collected per horse was recorded in a laboratory-reporting system, but specific date of collection of each sample (except for the first and last samples collected) was not routinely recorded.

Bacteriologic Cultures

All fecal samples were cultured for Salmonella species using standard techniques. Specimens were streaked onto brilliant green (BG) and xylose-lysine-tergitol (XLT-4) plates, and approximately 10 g of fecal material was put into 100 mL of tetrathionate Hajna broth. BG plates were incubated at 35° to 37°C for 18 to 24 hours and XLT-4 plates were incubated for 24 to 48 hours. Tetrathionate broth was incubated at 35° to 37°C for 24 to 48 hours, and then streaked to BG and XLT-4 plates. These plates were incubated as previously described. Suspect colonies on plates were subcultured and further identified by the Vitek GNI system. All Salmonella isolates were speciated and serotyped (National Veterinary Services Laboratory, Ames, Ia).

Data Analysis

The total number of horses examined (admissions), the total number of examinations (including admissions), the total number of horses hospitalized during the study period, and the number of samples collected per horse were calculated (Excel 2000, Microsoft Corp, Redmond, Wash) from recorded information. The frequency distributions of admissions (1-6) per horse, sex, breed, and patient outcome were calculated based on owner/horse identity and hospital record number, and the frequency distribution of number of samples collected per horse (nil to 8) was calculated from laboratory records and owner/horse identification and laboratory submission number. Length of hospitalization (days) was calculated from recorded date of hospitalization and date of discharge information, and was summarized by median and mean lengths of hospitalization and 95% confidence intervals (CIs), based on the Wilcoxon test (Minitab for Windows, Minitab Inc, State College, Penn) and the normal distribution (Statistix for Windows, Analytical Software, Tallahassee, Fla), respectively. Normality of the distributions of lengths of hospitalization and age were tested using the normal probability plot and Wilks-Shapiro statistic (Statistix).To estimate the incidence of Salmonella shedding, only hospitalized horses that were sampled on at least three occasions were included, because the sensitivity of culture is suboptimal and repeated attempts to culture Salmonella are necessary to increase the sensitivity of this technique.[12] The total number of days at-risk of shedding Salmonella was calculated as the sum of lengths of hospitalization. The incidence density rate (true incidence) of Salmonella shedding was calculated as

(No. horses detected shedding Salmonella)/(total No. horse-days at-risk)

and expressed as the number of horses shedding Salmonella per 1000 horse-days at-risk. For example, if 10, 10, and 30 horses were hospitalized for periods of 3, 6, and 9 days each, horse-days at-risk would be (10.3)+(10.6)+(30.9) = 360. If one case of Salmonella-shedding was detected in this group, the estimated incidence density rate would be one per (1000/360) 1000 horse-days AT-RISK = 2.8 per 1000 horse-days at-risk. Horses that were culture-positive on the first sampling were not considered incident cases of Salmonella-shedding, and therefore were not included in the numerator of the incidence density rate. Horses shedding Salmonella after hospitalization were assumed to have commenced shedding at the midpoint of their hospitalization, and therefore contributed half their length of hospitalization to the rate denominator. A 95% CI for the estimated incidence density rate was calculated assuming shedding Salmonella to be Poisson distributed.[13] Incidence-density rates were also calculated for each month of the study, the contribution of each horse to each month's horse-days at-risk being calculated on the basis of date of hospitalization and date of discharge information. Cumulative incidence (risk) rate (%) was calculated as described for the incidence density rate, except that the denominator used was the number of horses at-risk of Salmonella-shedding when hospitalized. For cumulative incidence rate, a 95% CI was calculated based on the binomial distribution.[14]The prevalence of Salmonella-shedding in horses admitted to the VTH was calculated as

(No. horses detected shedding Salmonella by culturewhen admitted)/(total No. horses admitted and sampled)

Ninety-five percent CIs for prevalence estimates were calculations based on the binomial distribution.[14]The temporal clustering of horses shedding Salmonella was investigated using the scan statistic.[15] For horses shedding Salmonella after hospitalization, the midpoint of their length of hospitalization was used as the date of first occurrence of Salmonella-shedding. The population at-risk used in these analyses was the monthly total number of horse-days at-risk. The occurrence of horses shedding Salmonella was assumed to be Poisson distributed, so the expected number of horses shedding Salmonella in any given time period was proportional to the incidence of Salmonella-shedding during the entire study period. The study period was scanned for clusters of horses shedding Salmonella using a scanning window of as much as 50% (130 days) of the time period (SatScan, Bethesda, Md).

Results

Between October 12, 2000 and June 30, 2001, 724 horses were admitted to the VTH. Six hundred and thirty-two horses (87.3%) were admitted only once during the study period; 69 (9.5%), 15 (2.1%), 2 (0.3%), 5 (0.7%), and 1 (0.1%) horses were admitted on 2, 3, 4, 5, and 6 separate occasions, respectively. Length of hospitalization was not recorded for 2 horses. Three-hundred and sixty (42.3%) of the 854 admissions performed did not result in hospitalization of the horse. The distribution of length of hospitalization of all horses hospitalized during the study is shown in Figure 1. The median and mean lengths of hospitalization (95% CI) were 3.0 (2.5, 3.5) and 4.3 (3.8, 4.7) days, respectively. The minimum and maximum lengths of hospitalization were 1 and 57 days. The distribution of lengths of stay was nonnormally distributed (Wilks-Shapiro statistic, 0.7317).     

Frequent human‐poultry interactions and low prevalence of Salmonella in backyard chicken flocks in Massachusetts

The backyard chicken (BYC) movement in the USA has increased human contact with poultry and subsequently, human contact with the pathogen Salmonella. However, to date, there have been few studies assessing prevalence of Salmonella in backyard flocks, despite the known public health risk this zoonotic bacterium poses. The objective of this study was to characterize human‐BYC interactions and assess the prevalence of Salmonella among BYC flocks. We interviewed 50 BYC owners using a structured questionnaire to determine flock and household characteristics that facilitate contact with BYC and that may be associated with Salmonella in the BYC environment. Composite faecal material, cloacal swabs and dust samples from 53 flocks housed on 50 residential properties in the Greater Boston, Massachusetts area were tested for Salmonella using standard culture techniques and confirmed using Matrix‐Assisted Laser Desorption/Ionization‐Time of Flight Mass Spectrometer. Microbroth dilution and whole genome sequencing were used to determine phenotypic and genotypic resistance profiles, respectively, and sequence results were used to determine multilocus sequencing type. No owners self‐reported a diagnosis of salmonellosis in the household. Over 75% of a subset of owners reported that they and their children consider BYC pets. This perception is evident in how owners reported interacting with their birds. Salmonella enterica subspecies enterica serotype Kentucky ST152 (serogroup C)—a strain not commonly associated with human infection—was confirmed in one flock, or 2% of tested flocks, and demonstrated resistance to tetracycline and streptomycin. We detected Salmonella at low prevalence in BYC. Further study of the health effects of exposure to zoonotic gastrointestinal pathogens such as Salmonella among families with BYC is warranted.     

Review on the effects of potential prebiotics on controlling intestinal enteropathogens Salmonella and Escherichia coli in pig production

Salmonella enterica serotypes (Salmonella sp.) are the second cause of bacterial foodborne zoonoses in humans after campylobacteriosis. Pork is the third most important cause for outbreak‐associated salmonellosis, and colibacillosis is the most important disease in piglets and swine. Attachment to host cells, translocation of effector proteins into host cells, invasion and replication in tissues are the vital virulence steps of these pathogens that help them to thrive in the intestinal environment and invade tissues. Feed contamination is an important source for Salmonella infection in pig production. Many on‐farm feeding strategies intervene to avoid the introduction of pathogens onto the farm by contaminated feeds or to reduce infection pressure when pathogens are present. Among the latter, prebiotics could be effective at protecting against these enteric bacterial pathogens. Nowadays, a wide range of molecules can potentially serve as prebiotics. Here, we summarize the prevalence of Salmonella sp. and Escherichia coli in pigs, understanding of the mechanisms by which pathogens can cause disease, the feed related to pathogen contamination in pigs and detail the mechanisms on which prebiotics are likely to act in order to fulfil their protective action against these pathogens in pig production. Many different mechanisms involve the inhibition of Salmonella and E. coli by prebiotics such as coating the host surface, modulation of intestinal ecology, downregulating the expression of adhesin factors or virulence genes, reinforcing the host immune system.     

A Longitudinal Study of Salmonella Infection in Different Types of Turkey Flocks in Great Britain

Salmonella is, after Campylobacter, the most reported zoonotic pathogen in the EU. Poultry are a common source of infection to humans, and turkey flocks are commonly colonized with the organism. We investigated the prevalence and risk factors of Salmonella infection in 179 houses in 60 holdings representative of turkey meat and breeder production in Great Britain. From each holding, up to four houses were chosen, and two consecutive flocks per house were sampled/tested for Salmonella to investigate the persistence, elimination and introduction of Salmonella in consecutive crops. At the first sampling, the overall flock‐level Salmonella prevalence was 32.8% and 8.9% for meat and breeding flocks respectively. There was a higher prevalence of Salmonella in flocks in the rearing stage than in the fattening and breeding stages. At the first sampling, the flock‐level prevalence of Salmonella was 26.8% (95% CI: 20.7–33.7%), while the prevalence level in the subsequent flock was 20.5% (95% CI: 13.6–29.7%). No houses were positive for any of the EU‐regulated serovars. The most commonly encountered serovars were S. Kottbus and S. Kedougou. Carry‐over of infection was observed in 44.8% of the positive houses, and introduction of new infection occurred in 8.4% of houses. Data from the questionnaires and auditing of all holdings and houses were combined and used to calculate adjusted farm‐ and house‐adjusted risk factors. Significant risk factors were feed from a source other than a national compounder (OR = 2.4), feeder type other than pan feeders (OR = 2.4) and hygiene practices other than terminal cleaning and disinfection using power‐washing with sanitizer and anteroom with boot change (OR = 2.8). The study discusses the main challenges currently faced by the industry to control Salmonella in turkey production.     

Epidemiology of Salmonella on the Paws and in the Faeces of Free‐Ranging Raccoons (Procyon Lotor) in Southern Ontario,Canada

Raccoons are common in urban and rural environments and can carry a wide range of bacteria, including Salmonella, that can negatively affect human and livestock health. Although previous studies have reported that raccoons shed a variety of Salmonella serovars in their faeces, it is unknown whether Salmonella is carried on raccoon paws. Our objective was to compare the prevalence of Salmonella on the paws and in the faeces of raccoons in south‐western Ontario. Raccoons were sampled in a repeat cross‐sectional study on five swine farms and five conservation areas from May to October 2012. A total of 416 paired faecal and paw samples were collected from 285 individual raccoons. Salmonella was detected in 18% (75/416; 95% CI, 14–22%) and 27% (111/416; 95% CI, 22–31%) of paw and faecal samples, respectively. Salmonella was detected only on paws in 8% (35/416; 95% CI, 5.9–11.5%), only in faeces in 17% (71/416; 95% CI, 13.6–21.0%) and on both paws and in faeces in 10% (40/416; 95% CI, 7.0–12.9%) of raccoon captures. Multilevel logistic regression models were used to examine associations between the presence of Salmonella and age (adult, juvenile), sex (male, female), location type (swine farm, conservation area), sample type (faeces, paw) and season (May–July and August–October). Random intercepts were included to account for clustering by individual animal and location. Significant differences, that varied by sample type and season, were noted in the prevalence of Salmonella carriage between sexes. Raccoons can carry Salmonella serovars known to infect humans and livestock on their paws and/or in their faeces and therefore have the potential to mechanically and biologically disseminate Salmonella among livestock facilities and human recreational areas.