Survey of numbers and types of lesions detectable in pig heads and the implications for human and animal health
subclinical sheep scab in bighorn sheep when mite numbers have been very low (Boyce and others 1991). More important, however, is how early in the progression of the disease a diagnosis can be made by serological methods. ELISAs are one of the most frequently used methods for this but there is a wide variation in the time at which ELISA seropositivity occurs, usually coinciding with the onset of clinical signs, an increase in the number of mites and lesion spread. While diagnosis of scab can be made by ELISA as early as seven days after infestation in experimentally infested cattle (Lonneux and others 1998), this does not appear to be the case in sheep in which circulating antibodies detectable by ELISA appear only after about four weeks, coinciding with the onset of the rapid growth phase of the disease (Bates 1997). The present observations would appear to confirm this. In a separate experiment (not reported here), two sheep were experimentally infested with P ovis and serum taken from them at weekly intervals was assayed by immunoblotting and ELISA. The sheep were positive by immunoblotting two and three weeks after infestation whereas they were unequivocally ELISA positive only five and six weeks after infestation (one was just positive after four weeks) (Fig 1). In the serological investigations of the second outbreak on the affected farm, the two methods were compared. The most significant finding was that immunoblotting was superior to ELISA not only in early diagnosis, but also in differential diagnosis of sheep scab in cases where the ELISA results were negative. The reason for this is not clear, but it is worth noting that native antigens were used in ELISA, while denatured antigens were used in immunoblotting.
Assessment of risk for humans associated with Supply Chain Meat Inspection – The Danish Way
The abstract summarizes the report in an adequate way, and brings the reader into the questions addressed as well as summarizes well the conclusions of the report.
Herd prevalence of Salmonella enterica infections in Danish slaughter pigs determined by microbiological testing
Abstract As a part of a nationwide programme to survey and control salmonella in pig herds, a microbiological survey of 1363 pig herds was performed in Denmark. A total of 13 468 slaughter pigs were examined at slaughter by culture of 5 g of caecal contents. Overall, 30 different serotypes of Salmonella enterica were isolated from 832 pigs (6.2%). The predominant serotype was S. Typhimurium, comprising 536 (64.4%) of the isolates. Four hundred and forty-eight isolates of S. Typhimurium were examined by phage typing, resulting in detection of 17 different phage types (definitive types, DT) with DT12 being the most frequent (49.1%). Salmonella enterica was found in 302 herds (22.2%), S. Typhimurium was found in 61.1% of these. 279 (23.1%) large herds (producing more than 2600 slaughter pigs per year) were found to be salmonella positive compared with 23 (14.7 %) small herds (annual production of 500 to 550 slaughter pigs). Practical constraints in the study design did not allow for a firm conclusion on the interplay among herd size, geographical location and occurrence of salmonella. In 284 of 302 infected herds (94.0%) only one serotype was detected. Infections with two different serovars were seen in 18 herds (6.0%).