化学发光直接竞争免疫分析法检测猪尿中莱克多巴胺残留

本试验研究建立了猪尿中莱克多巴胺（Ractopamine, RAC）残留的直接竞争化学发光免疫检测方法。合成了莱克多巴胺和辣根过氧化物酶的偶联物（RAC-HRP）,方法的检测限为0.09 ng/mL,空白猪尿中添加浓度为0.5、10和100 ng/mL RAC时,检测范围为0.3～157.0 ng/mL;回收率为76.3%～87.6%,批内变异系数为10.0%～12.2%,批间变异系数为14.2%～15.2%。     

化学发光免疫分析法检测猪尿中莱克多巴胺残留

本试验运用化学发光免疫分析法（chemiluminescence immunoassay,CLIA）检测猪尿中莱克多巴胺（Ractopamine,RAC）的残留。检测限为0.01 ng/mL,检测范围为0.036～32.2 ng/mL。添加浓度分别为0.1、1、10 ng/mL,平均回收率为73.2%,批内平均变异系数为9.7%,批间平均变异系数为11.3%。而本研究所建立的化学发光免疫检测方法(CLISA)可以达到检测RAC残留的要求。     

Pharmacokinetics of sulfamethazine in male, female and castrated male swine

The concentration of sulfamethazine in plasma and sulfamethazine and its metabolites in urine were compared in male, female and castrated male swine. A surgical technique for placement of catheters in the urinary bladder was used to facilitate the collection of urine in males and castrated males. The elimination rate of sulfamethazine from plasma and the excretion of parent drug and metabolites into urine did not differ significantly among females, males and castrated male swine.     

Sulfamethazine residues in swine

Two possible causes of violative sulfonamide residues in swine were studied. To determine if sulfamethazine accumulated in the tissues of swine when the drug was administered in feed, the rates of plasma drug disappearance following a single oral dose and continuous feeding of the drug were compared. The rate of plasma drug disappearance was not significantly different (α= 0.05) when the two methods of drug dosing were compared. When feed containing 2 μg sulfamethazine/gm was fed to swine during a 7—day period preceding slaughter, the animal's liver contained violative residues. Violative concentrations of sulfamethazine were detected in the livers, kidneys, and skeletal muscle of swine which consumed feed containing 8 μg sulfamethazine/gm.     

Validation of the fluorescence polarization assay as a serological test for the presumptive diagnosis of porcine brucellosis.

Sera from Canadian pigs (brucellosis free, n = 14037) and sera from pigs infected with Brucella suis (n = 401) were tested by the buffered antigen plate agglutination test, the complement fixation test, an indirect and a competitive enzyme immunoassay and a fluorescence polarization assay. The results were analysed and assay sensitivity and specificity estimates were calculated. The sensitivity and specificity of the tests were as follows: the buffered antigen plate agglutination test, 77.1 and 96.9%; the complement fixation test (considering anticomplementary sera as negative), 93.3 and 95.5%; the complement fixation test (considering anticomplementary sera as positive), 58.1 and 99.9%; the indirect enzyme immunoassay, 94.0 and 97.9%; the competitive enzyme immunoassay, 90.8 and 96.6%; and the fluorescence polarization assay, 93.5 and 97.2%; respectively. It was concluded that the fluorescence polarization assay was a valuable asset to the diagnosis of porcine brucellosis because of its accuracy, ease of performance and relative cost.     

Quantitative and Qualitative Study of Enzyme-linked Immunosorbent Assay to Detect IgG against Japanese Encephalitis Virus in Swine Sera

This study was designed to investigate the application of indirect enzyme-linked immunoassay (ELISA) in detecting IgG against Japanese encephalitis virus in swine sera and the qualitative nature of this test. The attenuated strain SA14-14-2 of Japanese encephalitis virus (JEV) was inoculated into 9-day-old chicken embryos and virus was harvested, purified and suspended in 0.9% saline as JEV antigen. The control antigen was prepared by the same method as for the antigen. In the ELISA, the optimal concentrations of antigen coated and dilution factor were selected using chi2 test. Ninety-two swine sera negative to haemagglutination inhibition (HI) were tested by this assay and the positive threshold was determined. The results of this study indicate that indirect ELISA has high specificity, sensitivity and reproducability. Simultaneous testing of 74 serum samples from nine pig farms was carried out to compare the existing HI test and the indirect ELISA. The coincidence rate of the two assays was 85.1% (63/74) and no significant difference was observed between them (p > 0.05). This ELISA test can detect 46 swine serum samples qualitatively and the titre of eight swine serum samples through endpoint dilution quantitatively within one 96-well plate.     

Comparison of the microtitration agglutination test and the enzyme-linked immunosorbent assay for the detection of herds affected with swine dysentery

A method was designed to evaluate and compare the microtitration agglutination test (MAT) and the enzyme-linked immunosorbent assay (ELISA) to detect antibodies in swine sera to Treponema hyodysenteriae and thereby establish a method for determining the prevalence of swine dysentery (SD) in herds. According to sampling criteria based on the hypergeometric distribution, sera were collected from 3 age groups of swine from farms having a history of SD on the premises (SD+) recently or being free of the disease (SD-). The highest degree of test sensitivity was obtained when sera from market age swine were evaluated with the ELISA. Of 14 SD+ herds from which sera were obtained from market-age swine, 13 were positive with the ELISA (93%); none of the 8 SD- herds was positive. The detection rates of individual swine in the SD+ herds for the 2 tests by age group were as follows: MAT--adult swine 1.4%, market-age swine 6%, and weaned pigs 0.8%; ELISA--adult swine 16%, market swine 31%, and weaned pigs 0.5%.     

Validation of a second generation competitive enzyme immunoassay (CELISA) for the diagnosis of brucellosis in various species of domestic animals

A second generation competitive enzyme immunoassay (CELISA) for detection of bovine antibody to Brucella abortus was developed to eliminate reagent variables in the assay. This assay was different from earlier CELISA formats in that it used recombinant protein A and protein G immunoglobulin receptors (PAG), labelled with horseradish peroxidase, thus eliminating the requirement for polyclonal anti-mouse-enzyme conjugate for detection. This allowed standardization of the assay. The CELISA uses a monoclonal antibody specific for a common epitope of the O-polysaccharide (OPS) of smooth lipopolysaccharide (SLPS) derived from B. abortus S1119.3. This antibody did not react with PAG. This monoclonal antibody was used to compete with antibody in the bovine test serum to the smooth lipopolysaccharide (SLPS) antigen. Reaction of bovine antibody was then measured directly with the PAG enzyme conjugate. In this case, development of colour in the reaction indicated a positive reaction. The performance characteristics of the new CELISA, sensitivity, specificity and exclusion of antibody of B. abortus S19 vaccinated animals, were very similar to those of the classical CELISA and to the indirect enzyme immunoassay (IELISA) when using sera deemed positive by isolation of the bacterium, either from individual animals or from some animals on the premises. All sera were tested by the buffered antigen plate agglutination test (BPAT) and the complement fixation test (CFT). Only samples positive on both BPAT and CFT were considered as positive and only samples negative on both tests were used considered negative. Sufficient samples from cattle, swine, sheep and goats to validate the test were included based on OIE guidelines suggesting inclusion of a minimum of 300 positive and 1000 negative samples.     

Use of enzyme immunoassay in a serological survey of leptospirosis in sheep

A total of 731 serums, all from Merino rams from 20 farms, were tested for antibodies against Leptospira interrogans serovars hardjo, pomona and tarassovi using the microscopic agglutination test (MAT). The enzyme immunoassay (EIA) technique was used to test all serums for IgM and IgG antibodies to serovar hardjo. In the MAT, reactions to serovar hardjo were most common with 236 rams (32.3%) reacting at 1/100 or greater. Only 1.9% of serums reacted against serovar tarassovi and 1.1% against serovar pomona. The percentage of sheep with positive MAT reactions to serovar hardjo ranged from 0 0 to 94.9 between farms. When using EIA, 46 (6.2%) of the serums were positive for IgM antibody and 246 (33.6%) were positive for IgG antibody. Correlation of the EIA for detection of IgG antibody with the MAT was good. The EIA detection of IgG antibody was considered to be a good alternative test to the MAT for epidemiological studies in sheep.     

Evaluation of a test for Clostridium difficile toxins A and B for the diagnosis of neonatal swine enteritis.

A commercially available 1-hour enzyme immunoassay (EIA) for detecting the presence of Clostridium difficile toxins A and B was evaluated for use in diagnosis of C. difficile infections in neonatal swine. This test was compared with a tissue culture cytotoxicity assay, which is considered to be the reference standard for the detection of C. difficile toxins. Twenty-seven samples of colonic contents and 23 fecal samples were collected from freshly euthanized neonatal swine with a history of scours. Of the 50 specimens tested, 20 were positive by the EIA test and tissue culture and 24 were negative by both tests, for an overall correlation of 88%. The sensitivity and specificity of the EIA were 91% and 86%, respectively, and the positive and negative predictive values were 84% and 86%, respectively. The EIA test is considered suitable as an aid for the diagnosis of C. difficile enteritis because of the high correlation between EIA results and those of the tissue culture cytotoxicity assay.     

Elimination of sulfamethazine residues from swine.

Tissue concentrations of sulfamethazine in swine fed the drug at the rate of 500 g/ton of ration (550 g/1,000 kg) for a 30-day period depleted to 0.1 ppm or less within 4 to 10 days after withdrawal of medicated feed. Depletion from the tissues and plasma of treated pigs showed a linear relationship with time when the concentrations were plotted on a semilogarithmic graph. Six untreated pigs that were placed on bedding in pens formerly occupied by the treated group developed tissue residues at or above 0.1 ppm sulfamethazine; the mean plasma concentration of sulfamethazine reached 2.8 ppm by day 15.     

贵州省猪弓形虫病的血清学调查

为全面了解贵州省猪弓形虫感染情况,对采自9个市（州、地）264个养猪场（户）的2 906份血清用酶联免疫吸附试验（ELISA）检测猪弓形虫抗体,总体阳性率为65.83%,变化范围为27.88%~85.42%。采集65份猪血清做ELISA和间接血凝试验（indirect heamagglutination assay,IHA）比较测定,两种方法总体符合率为58.46%。IHA方法补充检测177份猪血清,弓形虫抗体阳性率为27.68%。血清学调查结果与国内部分省（市）报道相符。     

广西主要动物源性产品中磺胺二甲嘧啶残留调查与分析

为了解广西动物源性产品中磺胺二甲嘧啶（SM₂）残留情况，本研究采用磺胺二甲嘧啶化学发光酶免疫分析法（SM₂-CLEIA）对2013-2017年采集的4 637份动物源性产品进行检测，共检出超标样品122份，涉及鲜乳、猪肉、水产品和猪尿，其中超标猪尿92份，SM₂含量100.51~860.44 μg/kg，猪尿中抗生素残留会污染水体、土壤，再通过动植物的富集作用进入食物链，危害人类健康，应引起重视；而本次受检的水牛奶、鸡肝脏、鸭肝脏、鸭肉均合格。所有受检样品超标率逐年下降，同时规模化养殖场样品合格率高于农村散养户、超市高于农贸市场。不同年份超标样品含量以2014年最高。采用食品安全指数（IFS）对广西动物源性食品中SM₂残留风险进行评估，结果均远小于1，说明在广西地区，现有的SM₂残留对人体的潜在危害较低。     

Development and evaluation of an indirect enzyme immunoassay for detection of porcine antibodies to pseudorabies virus.

An indirect enzyme immunoassay is described for detection of porcine serum antibody to pseudorabies virus. The analytical sensitivity of the enzyme immunoassay was found to be approximately 4.5 log 4 X 10 (5120 times) greater than the serum neutralization test, based on parallel end point titrations. The diagnostic sensitivity of the enzyme immunoassay was comparable or superior to that of the serum neutralization, based on the earliest detectable antibody after infection of swine with pseudorabies virus by intranasal or intrauterine routes or by contact with infected pigs. The enzyme immunoassay, at a screening dilution of 1:20, gave 100% agreement with ELISA results provided with a U.S. Department of Agriculture-Animal and Plant Health Inspection Service proficiency panel of 40 sera. One serum having demonstrable antibody by the enzyme immunoassay was seronegative by the serum neutralization test.     

National serologic survey for trichinellosis in sows in Canada 1996-1997

Sera from 14,408 market sows from the Canadian domestic swine herd were tested for trichinellosis using an indirect-ELISA as a screening test and a competitive ELISA for confirmatory testing. Three sera (0.02%) gave low level reactions on the competitive ELISA. These reactions were considered nonspecific, and this designation was supported by data from previous and subsequent national surveys, in which serologic, trichinoscopic, and digestion test methodologies was used. This study provides additional evidence that Canada is free of trichinellosis in domestic swine.     

Neospora caninum antibodies in wild carnivores from Spain

Serum samples from 251 wild carnivores from different regions of Spain were tested for antibodies to Neospora caninum by the commercial competitive screening enzyme linked immunosorbent assay (c-ELISA) and confirmed by Neospora agglutination test (NAT) and/or by indirect fluorescent antibody test (IFAT). Samples with antibodies detected by at least two serological tests were considered seropositive. Antibodies to N. caninum were found in 3.2% of 95 red foxes (Vulpes vulpes); in 21.4% of 28 wolves (Canis lupus); in 12.0% of 25 Iberian lynx (Lynx pardinus); in 16.7% of 6 European wildcats (Felis silvestris); in 6.4% of 31 Eurasian badgers (Meles meles); in 21.4% of 14 stone martens (Martes foina); in 66.7% of 3 pine martens (M. martes) and in 50% of 2 polecats (Mustela putorius). Antibodies to N. caninum in common genets (Genetta genetta) and Egyptian mongooses (Herpestes ichneumon) were only observed by c-ELISA but were not confirmed by IFAT and/or NAT. No antibodies were detected in 5 Eurasian otters (Lutra lutra) by any technique. Statistically significant differences were observed among species and among geographical areas. The highest seroprevalence of N. caninum infection was observed in the Cantabric Coastal region characterized by high humidity. To our knowledge, this is the first report of antibodies to N. caninum in free ranging wild carnivores, other than wild canids, in Europe. The existence of a possible sylvatic cycle could have important implications in both sylvatic and domestic cycles since they might influence the prevalence of infection in cattle farms in those areas.     

Seroprevalence of economically important viral pathogens in swine populations of Trinidad and Tobago,West Indies

The objective of this study was to evaluate the seroprevalence and identify the strains of swine influenza virus (SwIV), as well as the seroprevalence of porcine parvovirus (PPV), transmissible gastroenteritis virus (TGEV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine respiratory coronavirus (PRCV), porcine circovirus type 2 (PCV-2), and classical swine fever virus (CSFV) in pigs in Trinidad and Tobago (T&T). Blood samples (309) were randomly collected from pigs at farms throughout T&T. Serum samples were tested for the presence of antibodies to the aforementioned viruses using commercial ELISA kits, and the circulating strains of SwIV were identified by the hemagglutination inhibition test (HIT). Antibodies against SwIV were detected in 114 out of the 309 samples (37%). Out of a total of 26 farms, 14 tested positive for SwIV antibodies. HI testing revealed high titers against the A/sw/Minnesota/593/99 H3N2 strain and the pH1N1 2009 pandemic strain. Antibodies against PPV were detected in 87 out of the 309 samples (28%), with 11 out of 26 farms testing positive for PPV antibodies. Antibodies against PCV-2 were detected in 205 out of the 309 samples tested (66%), with 25 out of the 26 farms testing positive for PCV-2 antibodies. No antibodies were detected in any of the tested pigs to PRRSV, TGEV, PRCV, or CSFV.     

USDA regulation of residues in meat and poultry products

The National Residue Program conducted by the Food Safety and Inspection Service (FSIS) of the USDA includes a comprehensive testing program for residues of pesticides, drugs and other chemical contaminants in meat and poultry. Prevention strategies encourage producers to adopt quality control measures in their production management to prevent illegal residues in food. These activities have been effective in reducing the occurrence of violative residues and the potential for adverse health effects. Overall, the number of domestic monitoring samples containing violative residues is low-about 1% of samples tested. Violative residues are found less frequently in poultry than in livestock. More occur in swine than in other species; the least number occur in fed cattle and broilers. Testing results over the last 10 yr show that most drugs and pesticides used to enhance agricultural productivity are not causing a residue problem in meat and poultry. However, the FSIS cannot be complacent about its program achievements. Unacceptably high incidences of violative residues of certain drugs, namely, sulfonamides and antibiotics, still occur in particular production classes. For example, the incidence of violative sulfonamide residues in liver samples from swine slaughtered in 1985 was about 6%, with significant differences between geographical areas. An estimated 2.5% of market hogs had violative sulfamethazine residues in the muscle tissue. The FSIS is taking steps to correct this and other residue problems by strengthening the link between residue detection and enforcement and by expanding its analytical capability to monitor for residues.     

Chlamydial infections in duck farms associated with human cases of psittacosis in France

Five severe cases of psittacosis in individuals associated with duck farms were notified in France between January and March 2006. Diagnostic examination included serology and/or molecular detection by PCR from respiratory samples. As a consequence, we investigated all duck flocks (n=11) that were housed in the three farms where human infections occurred. While serology by complement fixation test was negative for all samples, cloacal and/or tracheal chlamydial excretion was detected by PCR in all three units. Notably, one duck flock was tested strongly positive in 2 of the 3 affected farms, and Chlamydophila (C.) psittaci strains were isolated from cloacal and/or tracheal swab samples from both farms. Human samples and duck isolates exhibited the same PCR-RFLP restriction pattern, which appeared to be an intermediate between genotypes A and B. Analysis of ompA gene sequences and comparison to those of the type strains showed that the isolates could not be strictly assigned to any of the generally accepted genotypes of C. psittaci. Further analysis by MLVA of the PCR-positive human samples revealed two distinct patterns, which were related to previously isolated C. psittaci duck strains.     

龙岩地区部分猪场弓形虫病的血清学调查

通过间接血凝(IHA)试验对采自龙岩地区12个猪场的2055份猪血清进行弓形虫病的抗体检测,结果表明猪弓形虫病在龙岩地区呈散发性流行。样品阳性率为5.99%,各猪场之间的抗体阳性率有一定差异,最高为16.22%,最低为0。在母猪群中随着胎次的增加,弓形虫病抗体阳性率也升高,由1～2胎的6.72%上升到5胎以上的12.18%;育肥猪群总体弓形虫病抗体阳性率较低,由哺乳仔猪的10.94%缓慢降至育肥猪的1.62%,呈现出随日龄增加弓形虫病抗体阳性率逐渐降低的趋势。