Bovis ISSN 2398-2993

Mastitis: Streptococcus dysgalactiae

Synonym(s): Summer mastitis complex

Contributor(s): Peter Down , Anja Sipka

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  • Cause: Streptococcus dysgalactiae.
  • Signs: mastitis.
  • Diagnosis: bacteriology.
  • Treatment: antibiotics.
  • Prognosis: good.



  • Strep. dysgalactiae is typically classified as an ‘environmental’ pathogen but some strains are known to behave in a contagious manner.
  • Widely distributed in the cow environment and most new infections will be acquired via the environment.

Predisposing factors


  • Poor environmental hygiene.
  • Poor teat condition.


  • Bovine strains of S. dysgalactiae are a homogeneous group of non-hemolytic or α-hemolytic cocci.
  • Several cell-associated and extracellular factors of S. dysgalactiae have been identified but the relative importance of these factors in the transmission and pathogenesis of mastitis caused by S. dysgalactiae are not understood.
  • Streptococcus dysgalactiae can interact with several plasma and extracellular host-derived proteins such as immunoglobulin G, albumin, fibronectin, fibrinogen, collagen, vitronectin, plasminogen, and α2-macroglobulin.
  • Also produces hyaluronidase and fibrinolysin, which may be involved in promoting dissemination of the organism into host tissue.
  • Streptococcus dysgalactiae adheres to and invades bovine mammary epithelial cells.
  • S. dysgalactiae may survive within mammary epithelial cells for extended periods of time.
  • There is only limited information on the role of bacterial and epithelial cell factors during the early stages of host-pathogen interactions.


  • This organism has characteristics of both a contagious and an environmental pathogen.
  • It has been isolated from infected mammary glands and teat injuries and transmitted during milking.
  • It has also been detected in cattle tonsils, mouth and vagina, and dry period infections in herds with no previous history of S. dysgalactiae IMI have also been demonstrated, thus highlighting the potential for environmental transmission.
  • S. dysgalactiae is also involved in the ‘summer mastitis complex’ which affects dry cows and heifers during summer months.
  • It has been isolated from the common cattle fly Hydrotaea irritans Cattle flies, which may play a significant role in establishment and maintenance of bacterial contamination of teats of healthy cattle.
  • Streptococcus dysgalactiae is considered to be the first bacterial species to colonize the bovine teat, and is thought to provide a favorable environment for colonization by Truperella pyogenes T. pyogenes mastitis and anerobic bacteria such as Peptostreptococcus indolicus and Fusobacterium necrophorum Fusobacterium necrophorum.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Huijps K, Lam T J & Hogeveen H (2008) Costs of mastitis: facts and perception. J dairy res 75, 113–20 PubMed.
  • Calvinho L F, Almeida R A & Oliver S P (1998) Potential virulence factors of Streptococcus dysgalactiae associated with bovine mastitis. Vet microbiol 61, 93–110 PubMed.
  • Kossaibati M A & Esslemont R J (1997) The costs of production diseases in dairy herds in England. Vet J 154, 41–51 PubMed.
  • Cruz Colque J I, Devriese L A & Haesebrouck F (1993) Streptococci and enterococci associated with tonsils of cattle. Lett appl microbiol 16, 72-74 PubMed.
  • Madsen M, Sorensen G H & Nielsen S A (1991) Studies of the possible role of cattle nuisance flies, especially Hydrotea irritans, in the transmission of summer mastitis in Denmark. Med vet entomol 5, 421-429 PubMed.
  • Madsen M, Sorensen G H & Aalbaek B (1990) Summer mastitis in heifers: a bacteriological examination of secretions from clinical cases of summer mastitis in Denmark. Vet microbiol 22, 319-328 PubMed.
  • Bramley A J, Hillerton J E, Higgs T M & Hogben E M (1985) The carriage of summer mastitis pathogens by muscid flies. Br vet j 141, 618-627 PubMed.
  • Bramley A J & Dodd F H (1984) Reviews of the progress of dairy science: mastitis control- progress and prospects. J dairy res 51, 481-512 PubMed.
  • Schalm O W, Carroll E J & Jain N C (1971) Bovine Mastitis. Lea and Febiger, 360.