[Incidence and serotypes of Salmonella in apparently healthy swine at slaughterhouses in Japan: 1975-1989]

Oral sodium chlorate, topical disinfection, and younger weaning age reduce Salmonella enterica shedding in pigs

Salmonella enterica subsp. enterica can cause swine illness or human foodborne disease. Although nontoxic to mammalian cells, chlorate can be converted to cytotoxic chlorite by salmonellae. To test whether chlorate is effective at reducing Salmonella shedding in weaned pigs exposed to shedding dams, a chlorate-nitrate-lactate (chlorate) oral dose was administered daily for 5 days following weaning, and this treatment was evaluated in combination with two weaning ages and a topical disinfectant. A total of 80 pigs were weaned at 10 or 21 days of age. Half within each age group were topically disinfected at weaning. Piglets were selected from dams for which Salmonella was detected in feces shortly after giving birth. Chlorate treatment reduced Salmonella prevalence and estimated Salmonella concentration in feces, cecal contents, and ileocolic lymph nodes. Younger weaning age (10 days of age) was associated with reduced shedding (lower concentration and prevalence) in samples collected at 10 days postweaning (DPW) and later. Chlorate treatment reduced the concentration of Salmonella in fecal samples at 5 DPW and in cecal samples at 14 DPW. The protective effects persisted through the end of the study at 14 DPW, 9 days after the final administration of chlorate. Disinfectant treatment reduced shedding in fecal samples at 14 DPW. Interactions were detected between the effects of chlorate and disinfection and between chlorate and weaning age. Chlorate treatment, topical disinfection, and younger weaning age may be useful tools for reducing Salmonella shedding on farms that practice segregated weaning and where sow-to-piglet transfer of Salmonella is an important source of infection in nursery pigs.

Isolation and serological survey of Salmonella in pigs in Japan

A total of 267 fecal and serum samples collected from individual pigs reared on a Salmonella-positive farm were subjected to bacteriological and serological examinations of Salmonella. Salmonella was isolated from 47 pigs (17.6%) and prevalence of antibody to lipopolysaccharide (LPS) of S. Typhimurium, which was partly common to S. O4, 12: d: -, was observed in 90 pigs (33.7%). Salmonella was isolated from 26 (28.9%) of 90 antibody-positive pigs and 21 (11.9%) of 177 antibody-negative pigs. Twenty-one of 36 pigs (58.3%) positive for S. O4, 12: d: -, five of 10 pigs (50.0%) positive for S. Havana, and none for S. Anatum had antibodies. Thus, seropositive rates were higher than isolation-positive rates, and antibody prevalence was associated with serovars of the isolates. Then, we analyzed antibody prevalence among pigs on Japanese pig farms. The antibodies to LPS of S. Typhimurium were found in 195 of 1,498 pigs (13.0%) and in at least one serum sample on 35 of 52 farms (67.3%). Our results indicate that Salmonella does not seem to be so prevalent in pigs though it is widely prevalent among pig farms.

Isolation of Salmonella from diarrheic feces of pigs

A survey of Salmonella was carried out in fecal samples of 887 pigs with diarrhea collected from 235 pig farms between April 1996 and March 2001. Salmonella was isolated from 84 feces (9.5%) of 887 pigs and from 45 (19.1%) of 235 farms. The higher prevalence was found in weaned pigs (12.4%) and fattening pigs (17.3%) than in sows (4.2%) and suckling pigs (4.5%). Isolation rates of S. Typhimurium were higher from weaned and fattening pigs than from the others. Therefore, risk of horizontal infection of S. Typhimurium will increase, if no adequate health managements are practiced when weaned and fattening pigs have diarrhea.

The major sources of Salmonella enteritidis in Thailand

The data of Salmonella serotypes during 1989-1993 from the World Health Organisation (WHO) National Salmonella and Shigella Center, Division of Clinical Pathology, Department of Medical Science, Ministry of Health, Thailand was analysed and found that the prevalence of Salmonella enteritidis had been dramatically increased since 1990. The average S. enteritidis isolates from human patient samples was 0.70% +/- 0.41% of the total reported Salmonella isolates during 1972-1989 and increased to 1.33%, 2.98%, 9.54%, and 16.98% in 1990, 1991, 1992, and 1993, respectively. The similar trend of S. enteritidis isolates from chicken meat samples were also observed. However, the conclusive epidemiological relationship between human and chicken S. enteritidis isolates needs to be proved by phage typing or other Salmonella typing methods.