Survival of Salmonella and Escherichia coli in pig slurry: simulation of decay

Spreading of slurry infected with multi-resistant Salmonella Typhimurium DT104 (MRDT104) on arable land might constitute a risk of transmission to wildlife. To estimate survival time on farmland, we modeled the bacterial decay based on Escherichia coli data from a plot study carried out in spring 2002 in Denmark. Time until undetectable levels were modeled under different scenarios: 1) E. coli in swine slurry, 2) Salmonella in slurry from clinically infected swineherds, and 3) MRDT104 in slurry from sub-clinically infected swineherds. A log-linear model extended with time2 and time3 was used to describe bacterial decay. For scenarios 2 and 3, we assumed that the level of bacteria in the slurry would be log 4.0 cfu/g and log 3.4 cfu/g, respectively, and a similar effect of spreading and decimation to that of E. coli. Hereby, it was estimated that Salmonella counts fell below detectable levels after 10 and 5 days, respectively

Association between Ascaris suum and Salmonella enterica in finisher herds

A possible association between Salmonella enterica and Ascaris suum was investigated. Salmonella infection was measured by antibodies in meat juice samples taken at slaughter, expressed as an ELISA OD-value. Ascaris infection was measured as the presence of white spots in livers detected at slaughter. Data were collected in Denmark in 2001, comprising 128.316 finishers. There was a significant qualitative association between presence of Salmonella antibodies and presence of liver spots at herd level. In contrast, no significant quantitative association at herd level was found. Pigs with liver spots had lower antibody levels against Salmonella compared with pigs without white spots. However, despite the significant association between Salmonella and Ascaris at herd level, its causality remains to be determined

Longitudinal study of Salmonella enterica serovar Typhimurium infection in three Danish farrow-to-finish swineherds

A longitudinal study on Salmonella enterica was carried out in 3 Danish farrow-to-finish swineherds in 2001. Litters from each herd were divided into 2 cohorts of 30 pigs each (180 pigs in total). Individual pigs were examined for bacteriology and serology monthly from weaning to slaughter. At weaning, individual sows were also examined for bacteriology and serology. In total, 88 pigs were found to be shedding on ≥1 occasion. Only Salmonella enterica serovar Typhimurium was detected. The culture-prevalence peaked in the nursery, and subsequently declined to undetectable levels before slaughter. The sero-prevalence peaked approximately 60 days after peak culture-prevalence. Salmonella was detected in individual fecal samples at least once in 53% of the pigs, while 62% were sero-positive more than once. Only 3.7% of all pigs were found to be culture-positive on ≥1 occasion. The average shedding time was estimated to have been 18 days

Surveillance of Salmonella in low prevalence swine herds in Denmark

The nation-wide Danish Salmonella surveillance and control program in finisher herds is primarily based on the monitoring of the presence of specific antibodies against Salmonella enterica in meat juice from carcasses

Effect of benzoic acid in the feed on Salmonella typhimurium in weaned pigs

The effect of benzoic acid on Salmonella Typhimurium was compared to formic acid + lactic acid in naturally infected weaners. Addition of 1% benzoic acid or 0.5% lactic acid + 0.5% formic acid did not result in a significant reduction of Salmonella prevalence, neither bacteriological nor serological, after 5 weeks of administration, compared to a control diet consisting of pelleted feed without organic acid

Sensitivity of cultivation of Salmonella enterica in pooled samples of pig faeces

We aimed investigate if the cost of bacteriological examination at herd level could be reduced by cutting down on the number of analyses without loss of sensitivity. Faeces samples sent to the lab for bacteriological examination were analysed by both the standard procedure (20 pen samples) and by mixing the same 20 samples into 10, 5 or 1 pooled sample(s), respectively. The relative sensitivity of the bacteriological analysis decreased to 94% following pooling from 20 into 10; to 92% by pooling from 20 into 5; and to 73% following pooling from 20 into 1. Percent agreement between the standard procedure and pooled samples was \u3e90% if only Salmonella-negative samples, or only Salmonella-positive samples, were pooled. Agreement was \u3e60% for pools of originally negative and positive samples. The suggested alternative pooling methods should be carried out in the laboratory

Campylobacter in finisher pigs - from farm to slaughter

Campylobacter excretion and diversity was investigated in three cohorts of 20 pigs from three different pig herds, respectively. Feces were collected from all pigs in the herd and after transport during lairage. Carcass swab samples were collected from all pigs pre- and post-chilling. All pigs (n=60) excreted Campylobacter in the herd and in the lairage. The typical excretion levels were between log 4/g and log 5.5/g feces. Pre-chilling more than 90% of carcasses were positive for Campylobacter

Risk assessment for Toxoplasma gondii in the Danish pig industry

The parasite Toxoplasma gondii is capable of infecting most mammals including man. In humans, toxoplasmosis is usually asymptomatic but may have serious consequences for pregnant women or immuno-compromised patients. Contact with infected cats and cat litter, contaminated soil and Infected meat are risk factors for toxoplasmosis. Although the prevalence of Toxoplasma in pig production has declined significantly dunng the past 30 years, it has recently been suggested that a large part of human cases of toxoplasmosis may be ascribed to meat, mcluding pork and pork products. Moreover, perinatal screening of pregnant women and infants for Toxoplasma has proven to be of limited value. This has raised the question of how to survey for Toxoplasma· in humans or meat? Therefore, the role of meat, including pigs and pork, as a risk factor for human toxoplasmosis was assessed by the Danish Meat Association . The release assessment showed that outdoor-reared pigs as well as sows and boars were at higher risk of infection with Toxoplasma. With respect to exposure, consumption of mildly cured pork products and inadequately heat-treated pork were associated with increased risk. Knowledge on elimination or survival of Toxoplasma in cured pork products is sparse, which is unsatisfactory given current trends toward lower salt content and lower cooking temperatures. It was concluded that, aside from consumption of raw pork, which is rare in Denmark and not recommended for other reasons, certain mildly cured ready-to-eat pork products, that have not been heat-treated, may constitute a risk for toxoplasmosis, if not frozen prior to manufacturing. Information on the effects of cunng on survival of Toxoplasma in meat is sparse and therefore deserves further research. However, most of the pork used for manufacturing in Denmark onginates from pigs raised indoors and for logistic reasons it is frozen prior to processing, thereby reducing the risk for human toxoplasmosis

Breeding for genetic resistance to Salmonella in pigs

Previous experimental Salmonella infection studies in Denmark have shown that some pigs remain faecal culture negative and seronegative despite oral inoculation with 10 c.f.u. S. Typhimunum and housing in highly contaminated pens, suggesting that some pigs are genetically resistant to Salmonella. Our study tested the following hypothesis: The Salmonella-negative status in certain pigs is due to genetic resistance, related to a single gene The resistance gene was supposed to have a low frequency and to be recessive and that full resistance only would appear if both alleles were recessive

Experimental study of possible interaction between Salmonella enterica and Ascaris suum in pigs

An experimental inoculation study was performed to study possible interactions between Salmonella enterica and Ascaris suum in pigs. Pigs were inoculated with 109 cfu Salmonella Typhimurium, 10,000 infective A. suum eggs, or both, or left as uninfected controls. There was no significant difference in number of Salmonella-excreting animals or Salmonella excretion level in feces between pigs inoculated with Salmonella + Ascaris and pigs inoculated with Salmonella only. Occurrence of Salmonella in liver, lungs, intestines or intestinal lymph nodes was not different between these two groups either