Julie A. Funk

Longitudinal study of Salmonella enterica in growing pigs reared in multiple-site swine production systems.

Intensive longitudinal investigations of breeding and growing pig populations in two multiple-site swine production systems were conducted in NC, USA. Five cohorts of sows and individually identified growing pigs from their litters were serially sampled in order to determine the prevalence and serotypes of Salmonella enterica in each stage of production based on fecal culture. In addition to fecal samples, feed and environmental samples were obtained. Fifteen different serotypes were isolated from the two systems, the most frequently isolated serotypes were S. typhimurium var Mbandaka and S. typhimurium var Copenhagen. Pig prevalence estimates ranged from 0 to 48.1%. Environmental contamination was frequently encountered despite cleaning and disinfection. Feed was rarely (2/800, 0.25%) identified as S. enterica positive. We observed highly variable patterns of S. enterica prevalence and serotype profiles within cohorts over time and among cohorts within systems. These observations indicate that point estimates of S. enterica prevalence and serotypes cannot be considered as reliable indicators of the S. enterica status of farms, and that uncontrolled studies of interventions to control S. enterica may yield misleading results. These findings are critical to the design of epidemiological studies of S. enterica on swine farms and may suggest that cohort level, as opposed to farm or company level events or management practices, may be important as potential risk factors for S. enterica fecal shedding in market age pigs.

Comparison of methods for isolating Salmonella bacteria from faeces of naturally infected pigs

A series of experiments was conducted using faecal samples collected from commercial swine farms to evaluate the effects of variation in methods used for the detection of Salmonella bacteria. The primary objective of the studies was to compare the protocols routinely used in two laboratories in the USA. The studies included five experiments comparing the enrichment protocols used routinely in the respective laboratories (Method 1:u200310 g faeces—buffered peptone water (BPW) pre‐enrichment—selective enrichment in Rappaport/Vassiliadis (RV) broth; Method 2: ∼1g faeces—primary enrichments in tetrathionate and Hajna GN broths—secondary enrichment in RV broth). The effects of enrichment temperatures (37 vs 42u2003°C) using RV broth (two experiments) and delayed secondary enrichment (four experiments) were also evaluated. Direct comparison of Method 1 and Method 2 indicated comparable results. However, when compared using faecal samples of equal weight, the Method 2 enrichment protocol was more sensitive for detecting Salmonella bacteria than the Method 1 protocol. Enrichment in RV at 42u2003°C was superior to 37u2003°C, particularly for samples that were pre‐enriched in BPW. Delayed secondary enrichment increased detection of Salmonella bacteria in swine faeces. These results highlight the imperfect sensitivity of culture methods, and the need for researchers to consider the sensitivity of bacteriological methods in the design and interpretation of the results of epidemiologic studies based on faecal culture

Seroprevalence of Trichinella, Toxoplasma, and Salmonella in Antimicrobial-Free and Conventional Swine Production Systems

There has been a growing niche-market, outdoor, antimicrobial-free (ABF) swine production system in the last few years prompted by consumers demand for a more natural pork product. The impact of such production systems on reemergence of current and historically significant swine-associated pathogens has not been determined. The objectives of the current study were to determine and compare Salmonella, Toxoplasma, and Trichinella seropositivity in two swine production systems: outdoor ABF and intensive indoor production systems. These three foodborne pathogens represent those with the highest importance for pork consumption. A total of 675 serum samples from three participating states, Wisconsin, North Carolina, and Ohio, were investigated. We found significantly higher seroprevalence of Salmonella and Toxoplasma from ABF herds (54% and 7%, respectively) than conventional (39% and 1%, respectively) (p = 0.001). Two pigs, both from ABF herds, were found to be seropositive for Trichinella. The results from this preliminary study suggest that all three pathogens were more commonly present in pigs that were reared in an ABF, outdoor, niche-market type of environment than the conventional, indoor-reared herds though there were some geographical variation in Salmonella. This warrants a robust epidemiologic study to determine the role of various risk factors in the two production systems that may lead to persistence of bacterial (Salmonella) pathogens and reemergence of parasites (such as Trichinella) of historical significance.

Salmonella enterica serovars from pigs on farms and after slaughter and validity of using bacteriologic data to define herd Salmonella status

The primary objective of this study was to evaluate the validity of using data obtained from slaughtered pigs for farm-level epidemiologic studies of Salmonella. The study involved groups of pigs from five farms. Salmonella isolates were obtained from on-farm samples, and a total of 370 on-farm and an additional 486 isolates from samples collected after commercial slaughter were subsequently tested. Preharvest samples included feces of individual animals from defined groups of nursery and finishing pigs on commercial farms and swabs from trucks. Postslaughter samples were cecal contents and mesenteric lymph node samples. The concordance between Salmonella serovars isolated from on-farm samples and those serovars isolated after slaughter varied widely among farms. Results of paired lymph node and cecal cultures were strongly associated (odds ratio, 7.0), but the agreement between on-farm and postslaughter results at the pig level was poor (kappa = 0.34). The results support recent findings that risk of exposure to Salmonella during transport and lairage remains a concern under contemporary industry conditions. The findings further imply that slaughter plant studies based on phenotyping of Salmonella alone (such as serovars) may not reliably indicate the Salmonella status of commercial swine farms.

Prevalence of pathogenic Yersinia enterocolitica in groups of swine at slaughter

In order to estimate the prevalence of swine herds infected with pathogenic Yersinia enterocolitica, 103 lots of market swine were randomly selected at slaughter during six 1-month intervals. Pigs within each lot were sampled by swabbing the oral-pharyngeal surface, poststunning and postexsanguination but prescalding. Ninety-five lots (92.2%) contained at least one pig infected with Y. enterocolitica. Pathogenic strains were defined as those harboring the ail gene which has been identified in Y. enterocolitica that causes human clinical disease. Identification of those strains harboring the ail gene was accomplished using a polymerase chain reaction technique. Twenty-nine lots (28.2%) contained at least one pig from which ail-containing (pathogenic) Y. enterocolitica were isolated. Of the 107 pathogenic Y. enterocolitica isolates identified, 89.7% were serotype O:5 and 3.7% were serotype O:3. The results from this study will aid in the design of future epidemiological investigations concerning on-farm prevalence and associated risk factors for pathogenic Y. enterocolitica. Additionally, the results support the hypothesis that swine are a significant potential reservoir for human infections by Y. enterocolitica.

Characterization of Antimicrobial-Resistant Phenotypes and Genotypes among Salmonella enterica Recovered from Pigs on Farms, from Transport Trucks, and from Pigs after Slaughter

The main objectives of this study were to determine antimicrobial resistance patterns among Salmonella serotypes and to evaluate the role of transport trucks in dissemination of antimicrobial-resistant strains of Salmonella. Salmonella from groups of nursery and finishing pigs on farms, from trucks, and from pigs after slaughter were compared using serotyping, patterns of antimicrobial resistance, and pulsed-field gel electrophoresis patterns. The five farms included in the study yielded 858 isolates representing 27 Salmonella serovars. The most common resistance observed (80% of all isolates) was to tetracycline; resistance to ampicillin (42%), chloramphenicol (31%), amoxicillin/clavulanic acid (30%), and piperacillin (31%) also were common. We found a correlation between serovar and antimicrobial resistance. High correlation was found between Salmonella Typhimurium var. Copenhagen and chloramphenicol resistance (Spearman rank correlation, rho = 0.7). Multidrug resistance was observed primarily in Salmonella Typhimurium var. Copenhagen (94%) and Salmonella Typhimurium (93%) and was much less common in the other common serovars, including Salmonella Derby (7%) and Salmonella Heidelberg (8%). Of the 225 isolates exhibiting the most common pentaresistance pattern in this study, amoxicillin/clavulanic acid-ampicillin-chloramphenicol-piperacillin-tetracycline, 220 (98%) were Salmonella Typhimurium var. Copenhagen, and 86% of the isolates of this serovar had this pattern. Isolates from the trucks were similar, based on pulsed-field gel electrophoresis patterns, to those from the cecum and mesenteric lymph nodes of pigs on two of the farms, suggesting the probable infection of pigs during transport. Class I integrons were also common among various serovars.

Prevalence of Yersinia enterocolitica in different phases of production on swine farms.

Swine have been identified as the primary reservoir of pathogenic Yersinia enterocolitica (YE), but little research has focused on the epidemiology of YE at the farm level. The objective of this study was to describe the prevalence of YE in different production phases on swine farms. In this cross-sectional study, individual pigs on eight swine operations were sampled for the presence of YE. On each farm, both feces and oral-pharyngeal swabs were collected from pigs in five different production phases: gestating, farrowing, suckling, nursery, and finishing. A pig was considered positive if either sample tested positive. Samples were cultured with cold enrichment followed by isolation on selective media plates. Presumptive isolates were confirmed as YE and assayed for the presence of ail with a multiplex PCR. Of the 2,349 pigs sampled, 120 (5.1%) tested positive, and of those, 51 were ail positive (42.5% of YE isolates). On all farms, there was a trend of increasing prevalence as pigs mature. Less than 1% of suckling piglets tested positive for YE. Only 1.4% (44.4% of which were ail positive) of nursery pigs tested positive, but 10.7% (48.1% of which were ail positive) of finishing pigs harbored YE. Interestingly, gestating sows had the second highest prevalence of YE at 9.1% (26.7% of which were ail positive), yet YE was never detected from the farrowing sows. These results represent the first on-farm description of YE in U.S. herds and provide the initial step for designing future studies of YE.

A REVIEW OF SOME OF THE HEALTH ISSUES OF CAPTIVE BLACK RHINOCEROSES (DICEROS BICORNIS)

Abstract In captivity, black rhinoceroses (Diceros bicornis) are beset by many disease syndromes not described in black rhinoceroses in the wild. Hemolytic anemia, hepatopathy, and ulcerative dermatopathy that lead to increased morbidity and mortality characterize these syndromes. It is uncertain whether these are separate disease syndromes with different etiologies or the same disease with different manifestations. This article offers a brief review of some of the health issues of concern for the captive black rhinoceros population and proposes some possible avenues of research for consideration.

In vitro susceptibility of Yersinia enterocolitica isolated from the oral cavity of swine.

Antimicrobial susceptibility of 181 (107 ail-harboring isolates and 74 non-ail-harboring) Yersinia enterocolitica isolates obtained from the oral cavity of swine was determined against 24 antimicrobial agents. All Y. enterocolitica isolates were susceptible to sulfamethoxazole/trimethoprim, enrofloxacin, aminoglycosides, and nitrofurantoin. Susceptibility to tetracycline appeared to vary by lot of origin. Isolates were resistant to sulfonamides (other than sulfamethoxazole/trimethoprim), penicillin, ampicillin, ticarcillin, cephalothin, macrolides, and tiamulin.

RISK FACTORS ASSOCIATED WITH A SKEWED NATAL SEX RATIO IN CAPTIVE BLACK RHINOCEROSES (DICEROS BICORNIS) IN THE UNITED STATES

Abstract The skew toward males in the sex ratio of calves is considered to be a problem for the captive population of black rhinoceroses (Diceros bicornis) in North America. This study used a retrospective case-control design to determine whether there was a predisposition toward birth of male calves over female calves and to examine risk factors associated with the occurrence of any detected skewed natal sex ratio in captive black rhinoceroses in the United States. The study population included captive female black rhinoceroses housed in the United States that had given birth to at least one calf of known sex. This study confirmed a skewing of the natal sex ratio toward male calves in the captive black rhinoceros population. The skewed ratio was found in calves born to wild-born dams, for which an increased time in captivity, irrespective of age, was associated with an increased likelihood of a male calf. Dams between 12 and 19 yr of age had a decreased likelihood of a male calf. The data also suggested a possible trend for the southern subspecies of black rhinoceros (Diceros bicornis minor) to be more likely to produce male calves than the eastern subspecies (Diceros bicornis michaeli). No associations were found with the sex of offspring in captive-born dams; however, this lack of association could be a result of low power in the study.