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Abstract

Objective—To evaluate sensitivity and specificity of a real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay performed on pooled nasal swab specimens, compared with virus isolation performed on individual nasal swab specimens by use of 2 cell culture lines for detection of swine influenza A viruses.

Sample Population—900 nasal swab specimens obtained from pigs at an abattoir and 62 nasal swab specimens submitted for diagnostic testing.

Procedure—Primers were chosen to amplify a conserved portion of the influenza virus matrix gene. Assay sensitivity was initially determined by testing serial dilutions of various subtypes of swine influenza viruses. Sensitivity and specificity were confirmed by use of nasal swab specimens with or without addition of known concentrations of influenza virus and further validated by testing nasal swab specimens obtained through an abattoir surveillance program or submitted for diagnostic testing. Aliquots of specimens were pooled in sets of 10, and results of real-time RT-PCR assays were compared with results of virus isolation of individual specimens in Madin Darby canine kidney (MDCK) and mink lung (Mv1Lu) cells.

Results—Real-time RT-PCR assay was highly specific (100%) and sensitive (88% to 100%). Among the 16 viruses isolated, 3 grew only in Mv1Lu cells and 3 grew only in MDCK cells.

Conclusions and Clinical Relevance—Results indicate that real-time RT-PCR assay is a fast and accurate test for screening numerous nasal swab specimens for swine influenza virus. Some viruses were isolated in only MDCK or Mv1Lu cells, indicating that use of > 1 cell line may be required to isolate a broad range of influenza A viruses. (Am J Vet Res 2005;66:119–124)

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in American Journal of Veterinary Research

standardized protocol ( Appendix ). Rectal temperatures were measured on the same days during the afternoon. Rectal temperatures > 38.8°C were considered clinically relevant. Nasal swab specimens and virus isolation —Nasal swab specimens were taken daily from

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in American Journal of Veterinary Research

abnormalities were observed. Deep nasal swab samples were collected for aerobic and anaerobic culture; the results indicated a mixed growth of Staphylococcus spp, Micrococcus spp, and Bordetella spp, with the latter susceptible to chloramphenicol

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in Journal of the American Veterinary Medical Association

forms. The study was approved by the University of Guelph Research Ethics Board and Animal Care Committee. Procedures —For both parts of the study, nasal swab specimens were collected from consenting humans and nasal and rectal swab specimens were

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether correlations exist between viremia with porcine circovirus type 2 (PCV2) and serum antibody profiles and between detection of PCV2 in nasal cavities and viremia of pigs from farms with and without postweaning multisystemic wasting syndrome (PMWS).

Animals—495 pigs, ranging from the late nursery stage to the early grower-finisher stage of production.

Procedure—Serum antibodies to PCV2 were studied with an ELISA that detects the ORF2 viral protein. Nasal swab specimens and serum samples were tested with a PCV2-specific PCR assay.

Results—PCV2 DNA and serum antibodies to PCV2 were detected in pigs from all farms, although in different proportions. Overall, PCV2 DNA was detected in greater percentages in serum samples and nasal swab specimens of pigs from farms with PMWS. Although viral DNA was detected in both serum samples and nasal swab specimens, PCV2 detection in nasal swab specimens was higher than in serum samples of pigs from all farms. Serum antibodies to PCV2 were detected in a greater percentage of pigs from farms with PMWS, compared with farms without PMWS.

Conclusions and Clinical Relevance—A high prevalence of PCV2 infection was found in pigs from farms with and without PMWS. Besides the presence of PCV2, unknown additional factors may be necessary to induce the full expression of PMWS. ( Am J Vet Res 2004;65:88–92)

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in American Journal of Veterinary Research

Product name Species and indications for use Route of administration Remarks Swine Influenza Virus RNA Test Kit, Code 59A7.80 Firm 432 For detection of swine influenza virus RNA from porcine nasal swabs NA

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To assess the relationship between shedding of bovine coronavirus (BCV) via the respiratory tract and enteric routes and the association with weight gain in feedlot cattle.

Animals—56 crossbred steers.

Procedures—Paired fecal samples and nasal swab specimens were obtained and were tested for BCV, using antigen-capture ELISA. Paired serum samples obtained were tested for antibodies to BCV, using antibody-detection ELISA. Information was collected on weight gain, clinical signs, and treatments for enteric and respiratory tract disease during the study period.

Results—Number of samples positive for bovine respiratory coronavirus (BRCV) or bovine enteric coro navirus (BECV) was 37/224 (17%) and 48/223 (22%), respectively. Some cattle (25/46, 45%) shed BECV and BRCV. There were 25/29 (86%) cattle positive for BECV that shed BRCV, but only 1/27 (4%) cattle negative to BECV shed BRCV. Twenty-seven of 48 (56%) paired nasal swab specimens and fecal samples positive for BECV were positive for BRCV. In contrast, only 10/175 (6%) paired nasal swab specimens and fecal samples negative for BECV were positive for BRCV. Only shedding of BECV was associated with significantly reduced weight gain. Seroconversion to BCV during the 21 days after arrival was detected in 95% of the cattle tested.

Conclusions and Clinical Implications—Feedlot cattle infected with BCV after transport shed BCV from the respiratory tract and in the feces. Fecal shedding of BCV was associated with significantly reduced weight gain. Developing appropriate control measures for BCV infections could help reduce the decreased weight gain observed among infected feedlot cattle. (Am J Vet Res 2001;62:1436–1441)

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in American Journal of Veterinary Research

Abstract

Objective—To identify cytocidal viruses and Pasteurella spp that could be isolated from cattle involved in 2 natural outbreaks of shipping fever.

Design—105 and 120 castrated male 4- to 8-monthold feedlot cattle involved in 1997 and 1998 outbreaks, respectively.

Animals—Nasal swab specimens and blood samples were collected, and cattle were vaccinated on arrival at an order-buyer barn from 4 local auction houses. Four days later, they were transported to a feedlot, and additional nasal swab specimens and blood samples were collected. Nasal swab specimens were submitted for virus isolation and bacterial culture; blood samples were submitted for measurement of respiratory bovine coronavirus (RBCV) hemagglutinin inhibition titers.

Results—93 of 105 cattle and 106 of 120 cattle developed signs of respiratory tract disease during 1997 and 1998, respectively, and RBCV was isolated from 81 and 89 sick cattle, respectively, while at the orderbuyer's barn or the day after arrival at the feedlot. During the 1997 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 4 cattle 14 days after arrival at the feedlot. During the 1998 outbreak, bovine herpesvirus 1 was isolated from 2 cattle at the order-buyer's barn and on arrival at the feedlot and from 5 cattle 7 and 14 days after arrival at the feedlot, and parainfluenza virus 3 was isolated from 1 animal the day of, and from 18 cattle 7 and 14 days after, arrival at the feedlot. Pasteurella spp was cultured from 4 and 6 cattle at the order-buyer's barn and from 92 and 72 cattle on arrival at the feedlot during the 1997 and 1998 outbreaks, respectively.

Conclusion and Clinical Relevance—Results suggest that RBCV may play a causative role in outbreaks of shipping fever in cattle. More than 80% of the sick cattle shed RBCV at the beginning of 2 outbreaks when the Pasteurella spp infection rate was low. (J Am Vet Med Assoc 2000;216:1599–1604)

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in Journal of the American Veterinary Medical Association

SUMMARY

Pseudorabies virus (prv) latency was investigated, using polymerase chain reaction (pcr). A pcr protocol was developed that specifically amplified a 217-base pair sequence within the gene encoding the essential glycoprotein gp50 of prv. Using this pcr procedure, the gp50 sequence was amplifed from tissues of pigs infected with various doses of prv (Becker strain). At postinoculation day 64, viral isolation was performed on nasal swab specimens and homogenates of tonsils and trigeminal nerve ganglia obtained from 11 prv-convalescent, seropositive pigs. Results were negative in all cases. By use of pcr, 11 of 11 pigs had prv-positive trigeminal nerve ganglia and brain stem, 10 of 11 pigs had prv-positive tonsils, and 9 of 11 pigs had prv-positive olfactory bulbs.

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in American Journal of Veterinary Research

Summary

Effect of prior porcine respiratory coronavirus (PRCV) infection on replication of H1N1-influenza virus in the respiratory tract of swine was studied. In an initial experiment, 3 groups of 5 feeder pigs were studied. Pigs of 2 groups were inoculated sequentially with PRCV, followed by H1N1-influenza virus at 2- and 3-day intervals. Pigs of the other group were inoculated with H1N1-influenza virus only. Pigs were monitored clinically and examined for nasal excretion of influenza virus. In the singly influenza virus-inoculated group, 83% of nasal swab specimens were influenza virus-positive over a period of 6 days after inoculation. In the dually virus-inoculated groups, only 27% (2-day interval) and 53% (3-day interval) of nasal swab specimens were virus-positive over the same postinoculation period. However, clinical signs of infection in these dually inoculated pigs were more severe than those in the singly influenza virus-inoculated pigs. There were no significant differences in antibody responses against influenza virus among the 3 groups of pigs.

In a second experiment, 2 groups of pigs were studied. One group of pigs was inoculated sequentially with PRCV, followed by H1N1-influenza virus 2 days later; the other group was inoculated with H1N1-influenza virus only. Pigs of both groups were serially euthanatized on postinoculation days (pid) 1, 2, 3, and 4 (after influenza virus). At necropsy, influenza virus titer and immunofluorescence in lung tissue were determined and gross lung lesions were recorded. Influenza virus titer in the dually inoculated pigs (pid 1 and 2) was at least 100-fold reduced, compared with that in the corresponding singly inocu lated pigs, and fluorescence was either not detected (pid 1) or was scant (pid 2). Differences in influenza virus replication between pigs of dually and singly inoculated groups became gradually less pronounced at pid 3 and 4. Lung lesions in the dually virus-inoculated pigs were distinctly more severe than those in the corresponding singly virus-inoculated pigs, and became progressively more pronounced as time after influenza virus inoculation progressed.

These results indicate that PRCV infection may induce factors in the lungs that markedly interfere with replication and virus production during a subsequent influenza virus infection. On the other hand, clinical signs of infection and lung lesions were enhanced in the dually virus-inoculated pigs. It is believed that early nonspecific defense mechanisms in the lungs may have a role in the host antiviral response, as well as in development of lesions.

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in American Journal of Veterinary Research