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Equine veterinary journal2000; 32(6); 515-526; doi: 10.2746/042516400777584721

Control of strangles outbreaks by isolation of guttural pouch carriers identified using PCR and culture of Streptococcus equi.

Abstract: Previous use of repeated nasopharyngeal swabbing and culture of Streptococcus equi showed that healthy carriers developed in more than 50% of 'strangles' outbreaks. The guttural pouches were the only detectable site of S. equi colonisation on endoscopic examination of horses during one of these outbreaks and S. equi was sometimes not detected by culture of nasopharyngeal swabs from carriers for up to 2 or 3 months before nasal shedding resumed sporadically. A more sensitive way of detecting S. equi on swabs from established guttural pouch carriers was therefore required. Conveniently selected 'strangles' outbreaks were investigated in detail using endoscopy, in order to develop and assess a suitable polymerase chain reaction (PCR) test. We report here 3 protracted 'strangles' outbreaks on different kinds of establishments in which between 29 and 52% of sampled horses were infected as detected by culture and/or PCR. Of the infected horses, between 9 and 44% were identified as carrying S. equi after clinical signs had disappeared and the predominant site of carriage was the guttural pouch. Prolonged carriage of S. equi, which lasted up to 8 months, did not cease spontaneously before treatment was initiated to eliminate the infections. The detection and isolation of the carriers, in conjunction with strict hygiene measures, apparently resulted in the control of the outbreaks and allowed the premises to return to normal activity. Comparing PCR and culture, many more swabs were found to be positive using PCR (56 vs. 30% of 61 swabs). Similar results were obtained for guttural pouch samples from 12 established carriers (PCR 76% and culture 59%). These results from repeated samples from relatively few animals need confirming using more long-term carriers. PCR can also detect dead organisms and is, therefore, liable to yield false positive results. Despite this drawback, it is argued that PCR provides a potentially useful adjunct to culture of nasopharyngeal swabs in the detection of asymptomatic carriers of S. equi following outbreaks of 'strangles'.
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Publication Date: 2000-11-28 PubMed ID: 11093626DOI: 10.2746/042516400777584721Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research investigates the effectiveness of using a polymerase chain reaction (PCR) test and isolation techniques to manage outbreaks of a serious equine disease known as ‘strangles’, caused by Streptococcus equi. The study found that more than half of strangles outbreaks resulted in healthy horses becoming carriers, primarily in their guttural pouches, and PCR was found to detect more infections compared to traditional testing methods.

Strangles Outbreaks and Carrier Identification

  • The study looked at how repeated nasopharyngeal swabbing and the culturing of Streptococcus equi, the bacterium that causes strangles, indicated that over 50% of disease outbreaks resulted in healthy horses becoming carriers.
  • During an outbreak, the guttural pouches—air sacs located in the horse’s head—were found to be the only site of S. equi colonization visible through endoscopic examination.
  • Interestingly, in some cases, S. equi wasn’t detected from nasopharyngeal swabs taken from carriers for up to two to three months before they began sporadic nasal shedding of the bacteria.

PCR Testing and Its Impact

  • The researchers sought a more effective detection method and decided to use endoscopy combined with a polymerase chain reaction (PCR) test to investigate selected strangles outbreaks.
  • The results indicated that PCR testing was more sensitive in detecting S. equi on swabs taken from the guttural pouches.
  • PCR testing allowed for the identification of more S. equi carriers, which helped control the spread of the disease and allowed the facilities to resume normal activity.
  • However, it was noted that PCR might also detect dead organisms, potentially leading to false positives.

Results and Conclusion

  • Between 29 and 52% of sampled horses were infected in the three examined outbreaks, with 9 to 44% identified as carriers after clinical signs disappeared. The main site of the disease carriage was the guttural pouch.
  • In comparison to traditional culture techniques, PCR found more positive cases (56% of 61 swabs vs. 30%). The same pattern was observed in guttural pouch samples from 12 established carriers (76% by PCR, 59% by culture).
  • Despite the possibility of false positives, the study concluded that PCR testing could serve as a useful addition to culture of nasopharyngeal swabs in finding asymptomatic S. equi carriers following outbreaks of strangles.

Cite This Article

APA
Newton JR, Verheyen K, Talbot NC, Timoney JF, Wood JL, Lakhani KH, Chanter N. (2000). Control of strangles outbreaks by isolation of guttural pouch carriers identified using PCR and culture of Streptococcus equi. Equine Vet J, 32(6), 515-526. https://doi.org/10.2746/042516400777584721

Publication

Equine veterinary journal
ISSN: 0425-1644
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 32
Issue: 6
Pages: 515-526

Researcher Affiliations

Newton, J R
  • Centre for Preventive Medicine, Animal Health Trust, Newmarket, Suffolk, UK.
Verheyen, K
    Talbot, N C
      Timoney, J F
        Wood, J L
          Lakhani, K H
            Chanter, N

              MeSH Terms

              • Animals
              • Carrier State / diagnosis
              • Carrier State / veterinary
              • Disease Outbreaks / prevention & control
              • Disease Outbreaks / veterinary
              • Horse Diseases / epidemiology
              • Horses
              • Nasopharynx / microbiology
              • Polymerase Chain Reaction / methods
              • Polymerase Chain Reaction / veterinary
              • Streptococcal Infections / prevention & control
              • Streptococcal Infections / veterinary
              • Streptococcus equi / isolation & purification

              Citations

              This article has been cited 28 times.
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