Streptococcus equi, subspecies equi ("strangles") and zooepidemicus ("strep zoo")

Test code: B0019 - Ultrasensitive qualitative detection and differentiation of Streptococcus equi, subspecies equi and zooepidemicus by real time polymerase chain reaction.

B0019 is included in P0013 - equine respiratory panel and in P0024 - equine breeding panel.

Streptococcus equi subsp. equi is the etiologic agent of strangles and is responsible for nearly 30% of all reported equine infections worldwide (Chanter, 1997). Strangles is characterized by pharyngeal constriction in the horse's upper respiratory tract as a consequence of lymph node swelling and is often accompanied by abscessation. The very closely related organism Streptococcus zooepidemicus (S. equi subsp. zooepidemicus) is a significant cause of equine lower airway disease, foal pneumonia, endometritis, and abortion (Chanter, 1997). There is currently no effective vaccine or treatment for strangles.

In the past, identification of S. equi bacteria usually relied on culture of the bacteria, but this technique is slow and not very sensitive. A recent study (Newton, 2000) has shown that repeated nasopharyngeal swabbing and culture of Streptococcus equi could not detect the development of healthy carriers in more than 50% of strangles outbreaks. 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. The study found that PCR was a more sensitive technique for detecting S. equi on swabs: many more known positive swabs were detected using PCR than using culture (56 of 61 swabs positive by PCR vs. 18 of 61 swabs positive by culture). Similar results were obtained for guttural pouch samples from 12 established carriers (PCR 76% vs. culture 59%). PCR also allows differentiation of the two subspecies, equi and zooepidemicus.

Utilities:

• Help confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of S. equi infection.
• Help ensure that horse populations are free of S. equi
• Early prevention of spread of this bacterium
• Minimize personnel exposure to this bacterium
• Safety monitoring of biological products that derive from horses

References:
Chanter, N. (1997) Streptococci and enterococci as animal pathogens. J. Appl. Microbiol. Symp. Suppl. 83:100S-109S.
Newton, J.R., Verheyen, K., Talbot, N.C., Timoney, J.F., Wood, J.L., Lakhani, K.H. and Chanter, N. (2000) Control of strangles outbreaks by isolation of guttural pouch carriers identified using PCR and culture of Streptococcus equi. Equine Vet J. 32:515-526.

Specimen requirements: Nasopharyngeal swab, or lymph node abscess swab, or gutteral pouch swab, or 0.2 ml fresh, frozen or fixed tissue, or 0.2 ml whole blood in EDTA (purple top) tube.

Contact Zoologix if advice is needed to determine an appropriate specimen type for a specific diagnostic application. For specimen types not listed here, please contact Zoologix to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative real time PCR

Normal range: Nondetected