ISSN 2398-2977      

Streptococcus spp





  • Family: Streptococceae.
  • Genus:Streptococcus.


  • Gk: streptos - twisted;Gk: kokkos - grain, berry, seed.

Active Forms

This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Clinical Effects



  • Many commensals on mucosal surfaces of respiratory and urogenital systems in healthy horses.


  • Streptococci are resident on the mucous membranes of the upper respiratory tract, lower genital and alimentary tract.
  • Reproduction is by binary fission to form chains or pairs.


  • Many infections stress-related from commensals.
  • Inhalation, ingestion, congenital, sexual or indirect transmission via feed, water or fomites.

Pathological effects

  • Capsules of some species antiphagocytic.
  • Purpura hemorrhagica may follow strangles   Strangles (Streptococcus equi infection)  and may be mediated by immune complexes.
  • Immune-complex glomerulonephritis reported followingS. equi zooepidemicussubspecies infection.
  • Host defense mainly relies on phagocytosis.
  • Antibodies may be raised against M protein.
  • Recovered animals are temporarily immune to reinfection.
  • Immunity is serotype-specific.
  • Pyogenic bacteria often cause abscess formation and suppuration.
  • Beta-hemolytic isolates mostly pathogenic.
  • Exotoxins produced - streptolysin O and S, hyaluronidase, DNase, protease and streptokinase.
  • Adhesins mediate attachment.
  • Trigger inflammation and suppuration.
  • Strangles, or contagious rhinopharyngitis   Strangles (Streptococcus equi infection)  , is caused byStreptococcus equisubspeciesequi.
  • Equine metritis   Uterus: contagious equine metritis  , neonatal infections, and secondary pneumonia caused byS. equisubspecieszooepidemicus.

Other Host Effects

  • Many are commensals on mucosal surfaces of upper respiratory and urogenital tracts.


Control via animal

  • Isolate suspected cases of strangles.
  • Treat adequately to avoid systemic spread.
  • Hygiene.

Control via chemotherapies

  • Pathogenic streptococci are usually susceptible to penicillin, chloramphenicol, cefalosporins, and potentiated sulfonamides.
  • Streptococci are often resistant to aminoglycosides and tetracyclines.

Control via environment

  • Hygiene.
  • Isolate affected animals.



This article is available in full to registered subscribers

Sign up now to start a free trial to access all Vetlexicon articles, images, sounds and videos, or Login

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Wilsher S & Allen W R (2006) Effects of a Streptococcus equi infection-mediated nutritional insult during mid-gestation in primiparous Thoroughbred fillies. Part 1: Placental and fetal development. Equine Vet J 38 (6), 549-557 PubMed.
  • Jacobs A A C et al (2000) Investigations towards an efficacious and safe strangles vaccine; submucosal vaccination with a live attenuated Streptococcus equi. Vet Rec 147, 563-567 PubMed.
  • Wood J L N, Burrell M H, Roberts C A, Chanter N & Shaw Y (1993) Streptococci and Pasteurella spp associated with disease of the equine lower respiratory tract. Equine Vet J 25 (4), 314-318 PubMed.

Other sources of information

  • Horserace Betting Levy Board (2016) Codes of Practice. 5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email:; Website:
  • Biberstein E L (1999) Streptococci. In: Veterinary Microbiology. Eds: D C Hirsh & Y C Zee. Blackwell Scientific, USA. pp 157-164. ISBN: 0 86542 085 8.


Abdomen: peritonitis

Abortion: EHV-1

Abortion: overview


Bladder: urinary tract infection

Blood: microbiology




Conjunctivitis: bacterial

Conjunctivitis: overview


Diarrhea: antimicrobial associated

Digital sheath: tenosynovitis

Endometrium: bacteriology

Equine influenza

Equine influenza virus

Eye: microbiology - overview

Feces: bacteriology

Foal: neonatal septicemia syndrome


Guttural pouch: empyema

Heart: endocarditis

Joint: septic arthritis - adult

Joint: septic arthritis - foal


Keratitis: bacterial

Keratitis: traumatic - ulcerative

Kidney: glomerulonephritis

Lung: pleuropneumonia - bacterial (pleuritis)

Lung: pneumonia - bacterial

Lung: pneumonia - neonatal bacterial

Mammary gland: mastitis

Nasolacrimal duct: obstruction - acquired

Navicular bursa: puncture

Nose: nasal discharge

Optic nerve: neuritis

Orbit: retrobulbar abscess

Pasteurella multocida

Penis: bacterial colonization

Penis: balanoposthitis

Purpura hemorrhagica

Respiratory: meconium aspiration

Respiratory: neonatal respiratory distress syndrome

Rhodococcus equi infection

Semen: bacteriospermia

Severe equine asthma

Skin grafting overview

Skin grafting techniques

Skin: bacterial disease - overview

Skin: pastern dermatitis - overview

Spine: osteomyelitis

Strangles (Streptococcus equi infection)

Streptococcus equi vaccine

Synovial fluid: microbiology

Testis: castration - post-operative complications

Testis: orchitis

Therapeutics: aminoglycosides

Therapeutics: beta-lactam antibacterials

Therapeutics: eye

Therapeutics: macrolides / lincosamides


Uterus: contagious equine metritis

Uterus: endometritis - bacterial

Uterus: pyometra

Uveitis: bacterial

Uveitis: recurrent

Vagina: bacterial infection

Want more related items, why not
contact us

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!


To show you are not a Bot please can you enter the number showing adjacent to this field