伪狂犬病（Pseudorabies,PR）是危害全球养猪业最严重的急性传染病之一。猪伪狂犬病的临床症状主要表现在:（1）母猪流产、产死胎、木乃伊胎;（2）公猪感染睾丸肿胀、萎缩,失去种用能力;（3）新生

In order to investigate immunization schedules of classical swine fever(CSF) in large-scale pig farms,and to evaluate the immune status,seven large-scale pig farms in Hubei province were selected.Pigs were divided into the sows,the boars,the prepubertal gilts,the breast-feeding piglets(about 0-30 days),the nursing piglets(about 31-60 days old) and the growing pigs(above 61 days old).In each herd,blood were collected from 5%-8% of pigs and antibody titers were tested.Results showed that the qualification rate of all immunized herds were 99.55%,96.43%,99.22%,89.88%,81.68% or 78.64%,and different immunization schedule induced different immune status.Overall,the nursing piglets and the growing pigs were the weakest of all pig groups.Piglets received primary vaccination on day 14,21,28 and 35 after birth based and the antibody examined 7 and 14 days after immunization.Results indicated that 28 days after birth was the best time for primary immunization.This study provides valuable references to the control of CSF.

To investigate the pathogenic properties of enterohemorrhagic Escherichia coli prevalent in pigs,bacteria were isolated from pigs with diarrhea;isolates were typed with biochemical tests and the antibiotics susceptibility assay was performed in accordance to the routine methods.The PCR assay was used to detect the virulence genes and resistance genes.Meanwhile,the pattern of outer membrane proteins of the pathogenic strains of bacteria was typed and the Entrobacter repetive intergenic consensus(ERIC)and the repetitive element PCR genomic fingerprinting(REP-PCR)were used to analyze the correlation of the pathogenicity of Escherichia coli.It was found that 21 sorbitol-negative strains of EHEC were isolated from 315 E.colis,of which 3,4 and 17 isolates harbored the stx2,stx1 and eae gene respectively.The pattern of outer membrane proteins showed three different types,of which 15.3 and 3 strains were OMP-1,OMP-2 and OMP-3 types respectively.As demonstrated by REP-PCR and ERIC-PCR the band type difference of these pathogenic strains were quite evident and they were belonged to different sub-groups.From these observations,it is apparent that the EHEC infection is a potential threat in central area of China where the proportion of consumption of the pig-meat is rather high.So,the surveillance against this infection in these area should be strengthened in order to prevent the transmission and spreading of infection.

OBJECTIVE To construct an attenuated Salmonella choleraesuis vaccine strain expressing the gene SLT-IIeB and FedF of Shiga-like toxin Escherichia coli (SLTEC) O138 with balanced lethal system. METHODS The gene of SLT-IIeB and FedF of SLTEC O138 was amplified, and then recombined with a vector pYA3493 (Asd+). The recombinant was electroporated into attenuated Salmonella choleraesuis C500 (Asd-). The expression of SLT-IIeB and FedF was analyzed by SDS-PAGE. The stability of the vaccine strains was studied by generation culture in vitro. RESULTS The stable attenuated Salmonella choleraesuis vaccine strain expressing SLT-IIeB and FedF of SLTEC O138 was constructed with balanced lethal system. The expressed products with protein quality 37000 could react with the antibody of FedF and SLT-IIeB. CONCLUSION The attenuated Salmonella choleraesuis vaccine strain could probably serve as a vaccine against edema disease and piglets paratyphoid.

Objective: To investigate the resistance to common antibiotics and resistance genes to aminoglycoside antibiotics of extraintestinal pathogenic Escherichia coli (ExPEC) isolated from infecjed pigs and chickens. Methods: The resistance of ExPEC isolates to 19 kinds of antibiotics were detected by Kirby-Bauer (KB) diffusion method. Extended-spectrum β-lactamases (ESBLs) producing isolates were detected by double-disc synergy test and were classified. PCR and sequencing were designed to detect aadA1, aadA2, strA-strB, aadB, aacC2, aac(3)-IV, aph(3′)-Ia, and aph(3′)-IIa. Results: These isolates showed multi-drug resistance. The highest proportion of susceptible isolates was to cephalosporins and amikacin (63%-97%). 93% of the isolates were resistant to more than 10 antibiotics. Two ESBLs-producing isolates were found, their genotypes had been classified as TEM-1 + CTX-M-14. More than 74% of the resistance-isolates were amplified to those resistance genes above and showed high levels of sequence conservation. Conclusion: The ExPEC isolates were highly resistant to the common antibiotics. The main resistance mechanism of aminoglycosides was to product the modified enzymes of these antibiotics.