Streptococcus & Enterococcus Infections - Poultry

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Also Known As: Enterococcosis — Streptococcosis

Most commonly isolated: S. dysgalactiae — S. equi — S. equi subsp. zooepidemicus — S. bovis/S. gallylyticus — S. gallinaceus — S. mutans — S. pluranimalium — S. suis — Enterococcus avium — E. cecorum — E. columbae — E. faecalis — E. faecium — E. durans — E. gallinarum — E. hirae


Streptococcal and enterococcal infections in poultry can cause acute septicaemia and chronic infections in affected birds.

There are ~50 recognised members of the Streptococcus genus and 21 of Enterococcus spp. all are commensal organisms, primarily of the gastrointestinal tract and mucosal surfaces, in both animals and humans. Some are also ubiquitous in the environment.

The majority of infections from these pathogens are opportunistic.

There does not appear to be any zoonotic risk to humans from ingestion of infected birds with these infections, with the exception of Streptococcus suis which is rare in birds and more commonly acquired from pigs. There are however concerns regarding the spread of Vancomycin Resistant Enterococci (VRE) to humans from poultry.





This group of pathogens cause a range of syndromes, most commonly septicaemia, peritonitis[1], salpingitis[1] and endocarditis.[2]

Thus clinical signs also vary widely and may range from anorexia, lethargy and diarrhoea to high mortality rates and severe neurological signs, lameness or jaundice.

Many other species not discussed here have been isolated from healthy birds and are thought to be non-pathogenic.

S. gallinaceus

Septicaemia and endocarditis in broiler parents.

S. gallolyticus

Known as a facultative pathogen in racing pigeons causing acute mortality, lameness, weight loss, diarrhoea and inability to fly. Also causes mortality in turkey poults.[3]

S. dysgalactiae

Associated with cellulitis in broilers.


Septicaemia and mortality in geese.[4]

S. pluranimalium

Associated with valvular endocarditis and septicaemia in adult broiler parents.

S. equi subsp. zooepidemicus

Associated with endocarditis, peritonitis, salpingitis, egg drop, septicaemia and high mortality in chickens[5] [1] and also massive mortality in eared grebes. In turkeys, the same pathogen is thought to be responsible for septicaemia.

S. suis

S. suis has been associated with septicaemia in psittacine birds.[6]


Enterococci are frequently involved in infections of day old chicks, affecting primarily the yolk sac.

E. faecalis has been most frequently associated with avian clinical disease including endocarditis in chickens[2] and hepatic granulomas in turkeys.[7] It can also cause amyloid arthropathies and concurrent systemic amyloidosis.[8] In ducks, the same pathogen can cause arthritis[9] and septicaemia in ducklings.[10] E. faecalis can also affect canaries, causing tracheitis.[11]

E. durans can cause bacteraemia and encephalomalacia in young chicks.[12] E. hirae can also cause similar brain lesions.[13]


On necropsy, changes in chickens, ducks and turkeys are similar and various organs may be affected, dependent of the species involved. Septicaemic birds are the most common presentation, in which the liver is pale and friable and viscera within both abdominal and thoracic cavities are congested with yellow or orange-ish discolouration. There may be a sero-fibrinous or serosanguinous exudate covering some organs. The skin may be discoloured and crusting in cases of cellulitis/dermatitis and joint lesions possibly with yellow caseous exudates occur in septic arthritis. Vegetative lesions are indicative of endocarditis. Infarcts can be present in any organ. In birds with encephalomalacia, lesions may be found anywhere except the cerebellum and yellow discolourations will be seen; malacia and heterophilic infiltration are visible microscopically. Pectoral muscle necrosis is pathognomic for S. gallolyticus septicaemia in pigeons.


Isolation and identification is essential for confirmed diagnosis. Bacteriology can be performed on yolk, embryo fluid, valvular vegetations from necropsy, blood samples from septicaemic birds, joint and any suspected lesions. It is thought that capillary microblood cultures may be more sensitive due to trapping of the micro-organisms in these small vessels.

The pathogens can then be cultured on sheep or ox blood agar, selective blood agar or MacConkey agar. Serological Lancefield testing can also be performed on beta haemolytic colonies.

The organism can often be visualised in microscopic sections as generic gram positive cocci.


Culture and sensitivity should always be performed whenever possible before selecting treatment. The efficacy of treatment deteriorates with progression of disease within a flock. Chronic cases, especially those involving endocarditis and arthritis, often do not respond.

Amoxycillin appears to be the drug of first choice for most infections according to sensitivity studies in poultry.

Ampicillin, doxycycline and erythromycin are effective in pigeon outbreaks of S. gallolyticus.


Good hygiene, management and housing strategies are imperative. Hygiene in the hatcher is particularly important to prevent iatrogenic transmission. It is possible to transmit these opportunistic bacteria when giving vaccinations, e.g. those for Mareks Disease. Minimisation of stress and immunosuppressive disease is also key.

Vaccines are available against S. gallolyticus and provide a degree of clinical protection for pigeons.

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  1. 1.0 1.1 1.2 Edwards, P. R., Hull, F. E (1937) Haemolytic streptococci in chronic peritonitis and salpingitis of hens. J American Vet Med Assoc, 44:656-660
  2. 2.0 2.1 Jortner, B. S., Helmboldt, C. F (1971) Streptococcal bacterial endocarditis in chickens associated lesions of the central nervous system. Veterinary Pathology, 8:54-62
  3. Droual, R., Ghazikhanian, G. Y., Shivaprasad, H. L., Barr, B. C., Bland, M. B (1997) Streptococcus bovis infection in turkey poults. Avian Pathology, 26(2):433-439; 10
  4. Ivanics, é., Bitay, Z., Glávits, R (1984) Streptococcus mutans infection in geese. Magyar Allatorvosok Lapja, 39(2):92-95; [5 fig.]; 20
  5. Peckham, M. C (1966) An outbreak of streptococcosis (apoplectiform septicemia) in white rock chickens. Avian Diseases, 10:413-421
  6. Devriese, L. A., Haesebrouck, F., Herdt, Pde., Dom, P., Ducatelle, R., Desmidt, M., Messier, S., Higgins, R (1994) Streptococcus suis infections in birds. Avian Pathology, 23(4):721-724; 10
  7. Hernandez, D. J., Roberts, E. D., Adams, L. G., Vera, T (1972) Pathogenesis of hepatic granulomas in turkeys infected with Streptococcus faecalis var. liquefaciens. Avian Diseases, 15:201-216
  8. Landman, W. J. M., Gruys, E., Dwars, R. M (1994) A syndrome associated with growth depression and amyloid arthropathy in layers: a preliminary report. Avian Pathology, 23(3):461-470; 38
  9. Bisgaard, M (1981) Arthritis in ducks. Etiology and public health aspects. Avian Pathology, 10:11-21
  10. Sandhu, T. S (1988) Fecal streptococcal infection of commercial white pekin ducklings. Avian Diseases, 32(3):570-573; 9
  11. Devriese, L. A., Uyttebroek, E., Ducatelle, R., Viaene, N., Derijcke, J., Gevaert, D (1990) Tracheitis due to Enterococcus faecalis infection in canaries. J Assoc Avian Veterinarians, 4(2):113-116; 5
  12. Cardona, C. J., Bickford, A. A., Charlton, B. R., Cooper, G. L (1993) Enterococcus durans infection in young chickens associated with bacteremia and encephalomalacia. Avian Diseases, 37(1):234-239; 9
  13. Randall, C. J., Wood, A. M., MacKenzie, G (1993) Encephalomalacia in first-week chicks. Veterinary Record, 132(16):418; 2


This article was originally sourced from The Animal Health & Production Compendium (AHPC) published online by CABI during the OVAL Project.

The datasheet was accessed on 6 July 2011.

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