Search Results

You are looking at 1 - 6 of 6 items for :

  • "nasal swab" x
  • Microbiology x
  • Refine by Access: All Content x
Clear All

Summary

Rapid and accurate detection of a virus in a population is a critical factor in the eventual treatment and/or control of the virus. In this study, we examined use of the polymerase chain reaction (pcr) to detect swine influenza virus in nasal swab specimens from infected pigs. This approach was first standardized, using viral rna purified by guanidinium/phenol-chloroform extraction and placed in the same transport medium as the swabs. By using highly conserved primers for the swine H1 hemagglutinin, we amplified a 591-base pair fragment that was analyzed by use of agarose gel electrophoresis, Southern blot, and dna sequencing.

To evaluate pcr as a potential diagnostic tool for detection of swine influenza virus infection, we obtained nasal swab specimens from experimentally infected pigs. Amplification by pcr and reamplification of extracted samples with internal primers yielded detectable bands for an amount of virus less than that required to infect embryonating chicken eggs. We also tested swab specimens from pigs involved in 3 separate, natural episodes of swine influenza. These swab specimens were extracted, amplified and reamplified, producing visible bands on the gel and in Southern blots. We performed Southern blot analyses on all pcr products, to confirm that they were from viral H1 rna. We also cloned and sequenced a 591-base pair product from 1 specimen and found that it was 100% identical to the hemagglutinin gene sequence of A/Sw/Ind/1726/88. Results indicate that pcr can be used to detect swine influenza virus, even in nasal swab specimens, the specimen typically collected for diagnosis of virus infection.

Free access
in American Journal of Veterinary Research

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.

Free access
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.

Free access
in American Journal of Veterinary Research

SUMMARY

Two indirect elisa containing outer membrane protein (omp) and lipopolysaccharide (lps) antigens from a field isolate of Salmonella choleraesuis var kunzendorf developed and evaluated in experimentally infected and uninfected control pigs. Experimentally induced infection with S choleraesuis was successfully established in 10 pigs by oral inoculation with 108 organisms, and 3 pigs died of clinical salmonellosis at postinoculation (pi) weeks 1, 2, and 4. Swab specimens from tonsils, nostrils, and rectum of pigs were obtained for culture, and sera were evaluated at weekly intervals for 9 weeks after inoculation. The elisa containing omp and lps antigens with either anti-swine IgG or protein albumin-to-globulin ratio (antiglobulin) conjugates were standardized for serologic evaluation. All 4 elisa (2 omp and 2 lps) detected seroconversion by pi week 3 and had sensitivities and specificities of 97.8 and 88.8, 100 and 100, 95.6 and 88.8, and 93.3 and 72.5%, at their ideal cutoff points (negative mean optical density + 2 sd). There was excellent agreement between all 4 elisa systems as determined by kappa values. Cultures of fecal, tonsil, and nasal swab specimens were positive for S choleraesuis until the fourth week of infection. Fecal swab specimens from 1 pig were positive for S choleraesuis until pl week 7. Persistent infection after antemortem culture results were negative was detected by all 4 elisa, which indicated consistently high titers until the end of pi week 9. Conventional bacteriologic examination of intestines, mesenteric lymph nodes, bone marrow, lung, liver, spleen, and bile yielded positive results for S choleraesuis in the 3 pigs that died of clinical infection, whereas results were negative in the other 7 pigs infected by the end of pl week 9. Histologic examination of lung, liver, spleen, intestines, and mesenteric lymph nodes from the 3 pigs that died of S choleraesuis infection revealed severe ulceration and inflammatory cell infiltration in the lamina propria and submucosa of the intestine, whereas minimal changes were observed in other organs.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To investigate in vitro antigenic relations, in vivo cross-protection, and isotype antibody responses to a winter dysentery (WD) and calf diarrhea strain of bovine coronavirus (BCV).

Design and Animals

Gnotobiotic and colostrum-deprived calves were inoculated oronasally with a WD (DBA) or a calf diarrhea (DB2) BCV, and were challenge exposed with the heterologous BCV.

Procedure

Nasal swab and feces specimens and blood samples were collected. Fecal and nasal specimens were assayed for BCV shedding by antigen-capture ELISA or immune electron microscopy. Bovine coronavirus antigens were detected in nasal epithelial cells by immunofluorescence. Antibody titers to BCV in serum were assayed by virus neutralization (VN), and BCV antibody isotype titers in feces and sera were quantitated by ELISA.

Results

All calves developed diarrhea and shed BCV nasally and in feces, then recovered and were protected from BCV-associated diarrhea after challenge exposure with the heterologous BCV. After challenge exposure with either strain, fecal shedding of DBA was detected in 1 of 4 calves and nasal shedding of DB2 was detected in 2 of 4 calves. Immunoglobulin M was the principal coproantibody to BCV early, followed predominantly by IgA. Immunoglobulin G1 coproantibody titers to BCV were low, but increased after challenge exposure. Immunoglobulin G1 antibodies were predominant in serum. After challenge exposure, all serum antibody isotype titers increased except IgG2. The VN antibody responses paralleled serum IgG1, antibody responses.

Conclusions and Clinical Relevance

Immunoglobulin A coproantibodies at challenge exposure were associated with protection against diarrhea. Nasal shedding of BCV after challenge exposure confirmed field data documenting reinfection of the respiratory tract of cattle, suggesting that, in closed herds, respiratory tract infections constitute a source of BCV transmission to cows (WD) or young calves. (Am J Vet Res 1996;57:48-53)

Free access
in American Journal of Veterinary Research

embryonated chicken eggs) from 2 of the 4 nasal swab specimens that had positive results when tested by use of the real-time RT-PCR assay; the virus was designated as Eq/CO. After the diagnosis was established, initial (acute) serum samples were obtained from

Full access
in American Journal of Veterinary Research