rcine reproductive and respiratory syndrome, caused by the porcine reproductive and respiratory syndrome virus (PRRSV), is an economically important disease in the swine industry. Previous studies demonstrated the presence of the virus in pig meat and its transmissibility by oral consumption. This study further analyzed the infectivity of PRRSV in commercial pig meat. Fresh bottom meat pieces (n = 1500) randomly selected over a period of 2 y from a pork ham boning plant located in Quebec, Canada, were tested by reverse transcriptase polymerase chain reaction (RT-PCR). Each trimmed meat was stored in the plant freezer, subsampled weekly for up to 15 wk, and tested with quantitative RT-PCR to determine the viral load. Meat infectivity was evaluated using specific pathogen-free piglets, each fed with approximately 500 g of meat at the end of the storage time. Genotype-specific RT-PCR confirmed the presence of PRRSV mainly during cold weather in 0.73% of the fresh meat pieces. Wild and vaccine strains of genotype 2 were detected. Porcine reproductive and respiratory syndrome virus nucleic acid was stable in meat stored at around -20°C during the 15 wk. Serological and molecular analysis showed the transmission of infection by a majority of PRRSV positive meat pieces (5/9) fed orally to naïve recipients. The results confirmed a low prevalence of PRRSV in market's pig meat, and virus transmissibility by oral consumption to naïve recipients even after several weeks of storage in a commercial freezer. It occurred mainly with meat harboring the highest PRRSV RNA copies, in the range of 109 copies per 500 g of meat, with both wild type and vaccine-related strains.

Porcine infectious anemia caused by Mycoplasma suis is a global disease and results in serious economic losses. To determine the prevalence of M. suis infection in eastern China, a cross-sectional serologic study was conducted with 3458 porcine serum samples randomly obtained from January 2014 to August 2016. The samples were tested with a blocking enzyme-linked immunosorbent assay developed in our laboratory. The seroprevalence was 33.3% in the complete sample set and was 25.9%, 37.8%, and 37.8% in 2014, 2015, and 2016, respectively. The seroprevalence was distinctly higher in summer (39.9%) and autumn (42.0%) than in spring (28.9%) and winter (23.3%). Shanghai was the region with the highest seroprevalence (54.2%) and Jiangsu the region with the lowest (23.0%). The seroprevalence was markedly higher in boars (47.1%), multiparous sows (47.0%), and replacement gilts (39.2%) than in piglets (24.2%), fattening pigs (17.2%), and nursery pigs (12.5%). These data demonstrate that the prevalence of M. suis infection is increasing yearly in eastern China.

The objective of this study was to test the hypothesis that porcine circovirus type-2 (PCV2) vaccination is efficacious when administered in the first week of life. Three groups of pigs were vaccinated with Circumvent either early (at the end of week 1), late (at the end of week 4), or not at all. All 3 groups were later challenged intranasally with PCV2 (at the end of week 5). Two other groups were immunized with keyhole limpet hemocyanin (KLH) as a novel antigen at the end of either week 1 or week 4. Weight, PCV2 genome copy number in serum and saliva, anti-KLH antibody titer, and serum PCV2-neutralizing antibodies were measured weekly. Early PCV2 vaccination or KLH antigen exposure resulted in earlier humoral responses that were slower to develop than in older piglets, yet converged with the responses to later vaccination within 5 wk. Both groups of vaccinated piglets had periods of higher PCV2-neutralizing antibody titers and lower viral levels shortly after weaning and PCV2 challenge, thus supporting the recent labelling of 1 Canadian PCV2 vaccine for use in week 1 and suggesting that early PCV2 vaccination can reduce piglet handling without compromising vaccine efficacy.

The objective of this study was to compare the protection against challenge with porcine circovirus 2 (PCV2) induced by an experimental vaccine based on open reading frame (ORF) 2 of PCV2 DNA plus an adjuvant (aluminum hydroxide, cobalt oxide, or liposome) and a commercial PCV2 subunit vaccine. A total of 35 colostrum-fed, cross-bred, conventional piglets were randomly divided into 7 groups. The commercial vaccine was more efficacious against PCV2 challenge than the 4 experimental vaccines according to immunologic, virologic, and pathological outcomes. The pigs inoculated with the experimental vaccine containing the liposome adjuvant had significantly higher levels (P < 0.05) of neutralizing antibodies and interferon-γ-secreting cells, and significantly lower levels (P < 0.05) of PCV2 viremia than the pigs inoculated with the other experimental vaccines. The pigs inoculated with the experimental vaccines containing either the liposome adjuvant or the cobalt oxide adjuvant had significantly lower lymphoid lesion scores (P < 0.05) than the pigs in the group inoculated with the PCV2 DNA vaccine dissolved in phosphate-buffered saline. Liposome proved to be a potent adjuvant that efficiently enhanced both humoral and cellular immune responses induced by the PCV2 DNA vaccine.

The objective of this study was to assess the efficacy of a trivalent inactivated Haemophilus parasuis serovars 4, 5, and 12 vaccine with polymeric adjuvant gel (GEL) and commercial vaccines against Glässer's disease in piglets. Commercial vaccines containing inactivated H. parasuis serovars 4 and 5 (China), inactivated H. parasuis serovars 1 and 6 (Spain), and inactivated H. parasuis serovar 5 (USA) were also evaluated. Our results demonstrated that the trivalent inactivated H. parasuis serovars 4, 5, and 12 vaccine with GEL adjuvant can provide better protection against the 3 most common pathogenic serovars circulating in China than other commercial vaccines tested. Our findings also indicated that inactivated H. parasuis serovars 1 and 6 vaccine cross-protects piglets against H. parasuis serovars 4 and 5; inactivated H. parasuis serovar 5 vaccine cross-protects piglets against H. parasuis serovar 4 challenge; but none of the commercial vaccines tested in this study protected piglets against H. parasuis serovar 12. Our results provide a basis for further identification of common protective antigens that can induce cross-protection against heterogeneous serovars.