Epidemiological Investigation of the Prevalence and Features of Postweaning Multisystemic Wasting Syndrome in Japan

Abstract

Abstract. To investigate the prevalence and features of postweaning multisystemic wasting syndrome (PMWS) in Japan, an epidemiological study was conducted in 692 weaned pigs with various clinical signs, commonly including wasting or weight loss, collected from 129 swine farms between 2000 and 2003. The presence of PMWS was diagnosed by the detection of characteristic histological lesions and moderate to large amounts of porcine circovirus type 2 (PCV2) antigen within the lesions in multiple lymphoid tissues. Postweaning multisystemic wasting syndrome was positive in 23.4% of pigs (162/692) over the course of the study, and occurred in 50.4% of the farms (65/129). Mortality in 30-120-day-old pigs in the farms positive for PMWS varied from 0.1 to 32.0%. No significant difference in mortality was seen between PMWS-positive and -negative farms (P 5 0.1). However, mortality was significantly higher in the PMWS-positive farms where PMWS was diagnosed in more than 50% of the pigs examined compared to farms negative for PMWS (P 5 0.02). These findings indicate that PMWS has spread widely in Japan. Moreover it may exist in variable forms in swine farms, including an epidemic form or a subtle endemic or sporadic form. A case-control study suggested that risk factors for the occurrence of PMWS include porcine reproductive and respiratory syndrome (PRRS) pneumonias and Mycoplasma hyorhinis infection.

Viral distribution and lesions in Kunming mice experimentally infected with porcine circovirus type 2b

“…It causes not only the progressive loss of body conditions, mortality and congenital tremor A2 (CT-AII) in weaned piglets ), but also abortion in pregnant sows (O'Connor et al 2001), porcine respiratory disease syndrome (PRDS) and porcine dermatitis nephritis syndrome (PDNS) in adult pigs (Johnstone and Lawton 2008;Phaneuf et al 2007). These diseases severely affect the pig industry, and cause huge economic losses worldwide Liu et al 2002;Gresham et al 2000;Grau-Roma et al 2009;Kawashima et al 2007;Elbers et al 2000). With the aim to study the disease caused by PCV-2, developing animal models for PCV-2 infection has been studied since the pathogenicity of PCV-2 was demonstrated.…”

Genotypic Change of Porcine Circovirus Type 2 on Japanese Pig Farms as Revealed by Restriction Fragment Length Polymorphism Analysis

“…PCV2 DNA was detected in 86.2-100% of farms between 2000 and 2003 [9]. These studies indicate a high prevalence of PCV2 infection on pig farms in Japan.…”

Mycoplasma hyorhinis infection in early cases of mycoplasmal pneumonia in swine and evaluation of diagnostic assays

“…As a result, it appears that immunosuppressive factors at the beginning of the nursery period may contribute to infection with M. hyorhinis. Several studies have shown the association of M. hyorhinis with other infectious agents and immunosuppressive factors, such as stress (Kinne et al 1991, Kawashima et al 1996, Kawashima et al 2007, Kixmoller et al 2008, which enables M. hyorhinis to colonize and propagate in these individuals. Reinforcing the hypothesis that M. hyorhinis could be considered a secondary agent of pneumonic lesions, experimental studies involving this pathogen rarely showed areas of pneumonia, and when pneumonic lesions were present they were mild and affected a small percentage of the inoculated animals (Poland et al 1971, Lin et al 2006).…”