Abdolvahab Farzan

Occurrence of Salmonella, Campylobacter, Yersinia enterocolitica, Escherichia coli O157 and Listeria monocytogenes in Swine

The objective of this study was to investigate the occurrence of major bacterial foodborne pathogens in swine. In total, 359 samples from manure storage tanks (91) and fresh pooled faeces (268) obtained from finisher (110), sows (78) and weanlings (80) were collected and tested. Campylobacter, Salmonella, Yersinia enterocolitica, Escherichia coli O157 and Listeria monocytogenes were isolated from 36.5%, 31.5%, 5.8%, 3.3% and 3.3% of samples respectively. All E. coli O157 isolates found on 10 farms were tested but none was determined to be E. coli O157:H7. Salmonella and Campylobacter were more likely to be detected from stored manure rather than from fresh faecal samples. Yersinia enterocolitica tended to be detected more commonly from fresh samples than from manure pits. Listeria monocytogenes was not recovered from manure pits or from sow faecal samples and only infrequently found in the faeces of weanling pigs and finisher pigs. The proportion of positive samples showed a seasonal change. Salmonella was twice as likely not be recovered in winter, whereas the chance of culturing Campylobacter was higher in winter. The 113 Salmonella isolates recovered on 24 farms and the four most common serovars were Salmonella Typhimurium var. Copenhagen (31.0%), Salmonella Derby (12.4%), S. Typhimurium (10.6%) and Salmonella Agona (10.6%). Of 131 Campylobacter isolates recovered on 21 farms, 118 isolates were Campylobacter coli and 13 isolates could not be speciated. Fifteen of 21 Y. enterocolitica isolates found on 15 farms were detected in finisher pigs. The sero/biogroups of Y. enterocolitica were O3/biotype 4 (16 isolates), O6,30/biotype 1A (three isolates), O5/biotype 1A (one isolate) and O8/biotype 1B (one isolate). These findings provide baseline information on the distribution of important zoonotic pathogens in swine and indicate that pigs should be considered as a possible source of foodborne diseases in humans.

Detection and characterization of Giardia duodenalis and Cryptosporidium spp. on swine farms in Ontario, Canada.

As part of the C-EnterNet surveillance program of the Public Health Agency of Canada, 122 pooled swine manure samples from 10 farms in Ontario, Canada were collected and tested for Giardia and Cryptosporidium. Giardia duodenalis cysts and Cryptosporidium spp. oocysts were detected using immunofluorescence microscopy. Nested-polymerase chain reaction protocols were performed to amplify the small subunit rRNA gene and the β-giardin gene for G. duodenalis, and the small subunit rRNA gene and the heat shock protein-70 gene for Cryptosporidium spp. The DNA amplicons were sequenced to determine genotypes and species. A mixed multivariable method was used to compare the presence of Giardia and Cryptosporidium in different stages of production. Both Giardia cysts and Cryptosporidium oocysts were present on all tested farms, with 50.8% of the samples positive for G. duodenalis and 44.3% positive for Cryptosporidium spp. by microscopy, and 66.4% and 55.7%, respectively, positive by polymerase chain reaction (PCR). No significant agreement was observed between microscopy and PCR method to detect Giardia and Cryptosporidium (p<0.05). The prevalence of Giardia in manure pits and finisher pigs did not differ (p>0.05), however, it was less frequent (odds ratio, OR=0.21 [0.07, 0.63]) among sows. Cryptosporidium was more likely (OR=3.6 [1.3, 9.9]) to be detected in manure pits and weaners (OR=3.3 [1.1, 10.0]) compared to finisher pigs, and it was less frequent (OR=0.06 [0.007, 0.55]) in sows than in finishers (p<0.05). DNA sequencing demonstrated that 92.1% of the Giardia isolates were Assemblage B and 7.9% were Assemblage E. The most prevalent Cryptosporidium were Cryptosporidium parvum (55.4%), and Cryptosporidium sp. pig genotype II (37.5%). These findings indicate that the occurrence of zoonotic isolates of G. duodenalis and Cryptosporidium is very high on swine farms in southern Ontario, and that there is a potential for transmission between swine and humans by means of cyst and oocyst contaminated water or foods.

Evaluation of the risk factors for shedding Salmonella with or without antimicrobial resistance in swine using multinomial regression method.

A multinomial logistic regression method was used to investigate the risk factors for antimicrobial resistance (AMR) in Salmonella isolated from faecal samples collected on 80 Ontario swine farms in Canada. The samples were classified into three groups including Salmonella‐negative samples (S−), Salmonella‐positive samples without AMR (S+AMR−) and Salmonella‐positive samples with AMR (S+AMR+). The samples collected directly from pigs had a greater chance to be positive for Salmonella with AMR compared to those samples collected from the pen floor. The odds of culturing Salmonella with or without AMR was higher if pelleted feed was used compared with mash or liquid feed (Pu2003<u20030.001). The faecal samples collected on farrow‐to‐finish farms had a significant lower chance of testing positive for Salmonella with multidrug resistance than the samples from grow‐finisher farms (Pu2003=u20030.004). The chance of culturing Salmonella without AMR on farms with a continuous system was higher than on farms with an all‐in/all‐out system (Pu2003=u20030.009). However, there was no significant association between the flow system and recovery of Salmonella with AMR. The larger farms were more likely to be in S+AMR+ group than in S− group (Pu2003<u20030.001) whereas herd size did not appear as a risk factor for being in S+AMR− group compared with S− group. These findings indicate that although on‐farm antimicrobial use is one component of resistance, there might be other farm management factors that also affect the development of emerging resistant bacterial foodborne pathogens on swine farms. Finding different risk factors for shedding Salmonella with or without antimicrobial resistance would help to take the appropriate approach to each group if a control programme were to be implemented or an intervention applied.

An epidemiological investigation into the association between biomarkers and growth performance in nursery pigs.

BackgroundBiomarkers are useful tools in research and clinical practice where they are often used to detect and monitor differences in the physiological state of an animal. The proteins IGF-1, IGFBP-3, GHR, CRP, SAA, Hp, IFN-α, IFN-γ, TNF-α, IL-1β, IL-6, IL-10, and IL-18 have been proposed as potential biomarkers for monitoring growth in livestock. The objective of this study was to determine whether hepatic gene expression of these proposed biomarkers is associated with growth performance in nursery pigs. Herd information and growth parameters were collected for 168 piglets from 8 commercial farms in southern Ontario. From these pigs, a subset of liver tissue samples (nu2009=u200974) was used for gene expression analysis of the proposed biomarkers. Multivariable linear regression methods were used to determine whether genetic expression of the proposed biomarkers was associated with growth performance in the nursery.ResultsModelling the herd information and individual piglet traits in relation to growth performance revealed that the weight at weaning and the age at weaning are significantly associated with nursery performance. Average daily gain (ADG) was significantly associated with hepatic IGFBP-3 and GHR expression in the liver (Pu2009<u20090.05), and tended to be associated with hepatic IGF-1 expression (Pu2009=u20090.071). Similarly, 9-week body weight was significantly associated with hepatic expression of IGFBP-3 and GHR expression (Pu2009<u20090.05), and tended to be associated with hepatic expression of IGF-1 (Pu2009=u20090.055).ConclusionThe age and weight at which pigs are weaned is an important determinant for nursery performance. Hepatic gene expression of IGF-1, IGFBP-3, and GHR can be useful biomarkers for monitoring growth performance in nursery pigs.