The first assessment to detect Mycoplasma hyopneumoniae by sampling laryngeal swabs to investigate sow stability in South Korea.

BACKGROUND: Mycoplasma hyopneumoniae (M. hyopneumoniae), a representative pathogen causing swine enzootic pneumonia, generally infects piglets vertically. However, it is difficult to ascertain the M. hyopneumoniae infection state of sows due to limited detection methods. This report investigated sow herd stability by applying nested PCR to laryngeal swabs of suckling pigs, which is reportedly the most sensitive method. RESULTS: M. hyopneumoniae was detected in 14 farms (63.6%) and 127 piglets (6.5%). The prevalence of sows likely to transmit M. hyopneumoniae in herds (11.1%) was calculated. In addition, there was a significant difference in detection rates among farms depending on herd size, gilt replacement rate, acclimation method, and antibiotic usage, suggesting various parameters that influence sow stability. CONCLUSIONS: The results demonstrated that laryngeal swabs from suckling pigs have provided useful information regarding vertical transmission from sows in South Korean farm conditions. This result demonstrated that farms with larger herd sizes, higher gilt replacement rates, and a practice of naturally exposing gilts for acclimation had higher detection rates in weaning piglets, indicating an unstable sow infection state.

Efficacy of a commercial live attenuated Lawsonia intracellularis vaccine in a large scale field trial in Korea.

PURPOSE: Porcine proliferative enteropathy (PPE) is known as one of the most important risk factors causing economic losses in swine industry worldwide. This study was conducted to evaluate the efficacy of a commercial oral attenuated Lawsonia intracellularis vaccine (Enterisol Ileitis) against PPE under a commercial pig farm condition in Korea. MATERIALS AND METHODS: Thirty two-day-old 672 piglets were randomly allocated into vaccinated and control groups. All piglets in the vaccinated group were inoculated with a commercial attenuated L. intracellularis vaccine as following the manufacturer's instruction. Body weights of all pigs in both groups were measured on the vaccination day and 6, 14, and 20 weeks post vaccination and an average daily weight gain (ADWG) was calculated. Health status was observed biweekly during the whole trial. RESULTS: The vaccinated group showed significantly higher body weight (p<0.05) and ADWG (p<0.05) than those of the control group. The vaccinated group had significantly reduced impairments in activity, growth, defecation frequency, and stool hardness (p<0.05). Additional health benefits and improved weight gain by the vaccination produced a 4.2:1 return of investment, and the higher gross margin was $4.80 per pig. CONCLUSION: Our finding suggests that the L. intracellularis vaccine program has effects on the substantial health and economic benefits in the Korean swine industry.

Microarray analysis of differential expression of cell cycle and cell differentiation genes in cells infected with Lawsonia intracellularis.

Infection of intestinal crypt epithelial cells by the obligate intracellular bacterium Lawsonia intracellularis is directly linked to marked proliferation of the infected enterocytes within 3-5days post-infection. The virulence factor for this unique host cell-proliferative response is not known, but is considered to involve altered crypt cell cycle or differentiation events. McCoy mouse fibroblast cells were infected with L. intracellularis, and then harvested for expressed mRNA at daily time points, with matching non-infected control cell cultures. Mouse DNA microarray (>44,000 transcript targets) analysis of cDNA derived from matching mRNA samples showed over 40 identifiable genes with at least 4-fold changes between days 0 and 3 after infection with L. intracellularis. These included altered transcription of typical host cell 'alarm' response genes, such as interferon-related response genes Isgf3g and Igtp, known to be associated with invading microbial agents. Altered transcription of several genes in these cells known to be active in regulation of the cell cycle or cell differentiation genes, including usp18, Hr, Elavl2 and Slfn2, were also detected. The altered transcription of several of these genes via RT-PCR analysis was confirmed. The microarray-detected altered transcription of cell cycle and cell differentiation genes is of possible interest for links to Lawsonia-related disturbances in epithelial cell differentiation within the intestinal crypt, but this would need to be confirmed in intestinal epithelial cell studies.