"

1.4 Impetigo – Large Animals

Learning Objectives

  1. What bacteria typically cause impetigo in goats, cattle and sheep?
  2. Describe the clinical signs associated with this condition.
  3. What measures should you take to avoid spreading the disease to other milking animals and humans?
  4. How do you manage impetigo in large animals?
  5. Compare the disease in dogs and large animals.

  1. General Considerations

    1. Impetigo is common in goats, sheep and cattle.
    2. It is characterized by a superficial pustular dermatitis that does not affect hair follicles.
    3. Females appear to be predisposed.
    4. It typically occurs secondary to predisposing factors such as trauma, stress of parturition and a moist environment.
    5. The milker can spread the disease if good hygiene practice is not adopted during milking.
    6. It is zoonotic and may, occasionally, cause dermatitis on milker’s hands.

  2. Etiology

    1. Staphylococcus aureus is by far the most common agent but, streptococci may sometimes be involved.

  3. Clinical Signs

    1. Lesions are typically characterized by vesicles, pustules, papules, crusts, or nodules localized to the intermammary sulcus and base of the teats of milking animals.
Multiple single and coalescing pustules on the abdomen of a goat with impetigo.
Multiple single and coalescing pustules on the abdomen of a goat with impetigo. Courtesy of Prof. Stephen White.
    1. The lesions may spread to affect the whole teat, ventral abdomen, perineum, medial hind legs and ventral aspect of the tail.
    2. Pruritus is not present but lesions may be painful to the touch.
    3. Impetigo can predispose to staphylococcal mastitis in which case systemic signs may be present.
    4. Major differential diagnoses are viral causes of udder lesions.

  2. Diagnosis

    1. History and clinical signs.
    2. Cytology of pustules and/or exudate underneath a crust shows cocci bacteria and degenerated neutrophils.
    3. Bacterial culture will identify the causative agent.
    4. Skin biopsy may be needed if the patient does not respond to appropriate therapy.

  3. Treatment

    1. Local antiseptics (e.g. chlorhexidine, iodophors, hypochlorous acid) or antibiotic cream or ointment.
    2. If severe, appropriate systemic antibiotics, ideally based on culture and sensitivity, may be required. However, always try topical therapy first. Follow the canine guidelines for pyoderma treatment.  Choose “first choice drugs” first! These include amoxicillin clavulanic acid, cefalexin, cefadroxil, and clindamycin. Recheck before discontinuing therapy. Antibiotic therapy can be terminated when all lesions resolve.
    3. Impetigo may spread to other animals by the milker.
    4. Milk affected animals last. Use single-service paper towels to clean the teats and udder before and after milking, and make sure the milker will wash his/her hands after contact with affected animals.
    5. Remember! Infection may be transmitted to the exposed skin of humans.

Important Facts

  • Impetigo is common in goats, cattle and sheep.
  • Staphylococcus aureus is the most common agent and causes vesicles, papules, pustules, crusts, and/or nodules on the udder of milking animals.
  • Topical treatment may suffice for most cases.
  • If systemic therapy is required, choose the antibiotic based on culture and susceptibility test results. Choose “first choice drugs” first!
  • Impetigo can predispose to staphylococcal mastitis.
  • It can spread to other animals if proper hygiene is not adopted during milking.
  • It may cause dermatitis on the hands of milkers.

 

References

Foster AP. Staphylococcal skin disease in livestock. Vet Dermatol 2012; 23:342-351.

McNeil PE. Staphylococcal skin infections. In: Aitken ID, ed. Diseases of Sheep, 4th edn. Oxford: Blackwell Publishing, 2007; 312-315.

Scott DW. Bacterial Diseases. In: Large Animal Dermatology. Philadelphia, PA: W.B. Saunders, 1988; 121.

Scott DW, Smith MC, Manning TO. Caprine Dermatology. I. Normal Skin and Bacterial and Fungal Disorders. Comp Cont Educ 1984; 6:S 190.

Scott F M, Fraser J, Martin WBl. Staphylococcal Dermatitis of Sheep. Vet Rec 1980; 107: 572.

Smith MC. Caprine dermatologic problems: A review. J Am Vet Med Assoc 1981; 178: 724-9.

Yeruham I, Elad D, Perl S et al. Contagious impetigo in a dairy cattle herd. Vet Dermatol 1996; 7:239-242.

License

Icon for the Creative Commons Attribution 4.0 International License

Small and Large Animal Dermatology Handbook, Vol. 1 Copyright © 2025 by Sheila M.F. Torres, DVM, MS, PhD, DACVD is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book