Back to Integumentary / Skin

Definition

Any pus forming infection of the skin.

Clinical Signs

May observe any of the following:

Surface pyoderma

• Patches of pruritic, red , irritated-looking skin with or without scabbing.

Superficial pyoderma

• Inflammation (redness and swelling), moist eczematous lesions, papules or pustules.
• Itching (pruritus), scratching, or chewing of affected area along with hair loss.

Deep pyoderma

• Inflammation, ulcerative lesions with serosanguinous crusting and pus, and hair loss.
• Itching may not be present at this stage, however the rat may continue to chew, lick, or attempt to groom that area if in reach, particularly if there is discomfort or pain.

Etiology

An infection of the skin, pyoderma is is seen as an inflammatory destructive disease that is frequently of unknown origin. Bacteria, primarily staphyloccocal organisms, may be cultured although in many cases the bacterial cause may be elusive. This is due to the fact that often the bacteria that is cultured is normal resident flora of the skin.

Pyoderma can be divided into the following classifications: surface, superficial, and deep. It is also defined as being of a primary or secondary infection.

Surface pyodermas are called such because bacteria present on the skin, and involved in the infections, are confined to the surface of the skin. It may be seen as red, irritated looking, pruritic patches of skin. Scabs may present if the rat persists in scratching the affected areas .

Primary pyoderma is often ideopathic in nature (occurring without any predisposing cause), and may be a result of suppressed or compromised immune states. If bacterial infection is involved it is usually one organism as opposed to mixed or more than one organisms such as in deep pyodermas.

Superficial (sometimes seen as a cellulitis affecting the layer of skin at the level of the hair follicle) and secondary pyoderma is primarily caused by bacterial infection below the epidermal layer of skin. However, other conditions can contribute to the presence of superficial and secondary pyoderma, such as ecto-parasite infestation, fungal infections, atopic or contact type allergic responses, immunologic or endocrine diseases like diabetes, hypothyroidism, or hypoadrenocorticism.

Deep pyodermas are just as the name suggests, extending well beneath the level of the hair follicle (necrotizing fascitis/flesh-eating disease is a deep pyoderma). Abscesses, tunneling of the skin, ulcerative (and necrotic) lesions, lesions with serosanguinous crusting and pus, and hair loss may be among the signs that are seen.

Most often the bacteria found in surface or primary pyodermas in rats is staphylococcus, a Gram-positive cocci bacterium. Staphylococcus is commonly found in the nasopharynx, lower GI tract, and as a natural resident on the fur and skin of rats.
In rats with dermatitis, intense itching causes the rat to scratch and continually groom the area. This constant scratching and grooming initiates lesions or aggravates them, and contributes to the source of staphylococcus in the wound. Other bacteria that may be a factor to a lesser degree is streptococcus (found to be a factor in necrotizing fascitis/flesh-eating disease), which may contribute to abscess formation in deep pyodermas.

Excoriated skin lesions vary in size and are often supperative having a sero-sanguinous type of weeping or drainage. Although lesions are most likely to be seen in areas of the skin that have the most exposure to warmth and moisture, they can be found on other areas of the body as well. In these areas higher bacteria counts are likely to be seen on culture.

The length of the therapy will be based on successful elimination of whatever is causing the irritant. Pyodermas are difficult to resolve and many tend to reoccur. Treatment tends to be long term.

Figures

Case Histories of Pyoderma (*note: graphic photos)

• Fig. 1: Pyoderma involving the bacteria staphylococcus.
• Fig. 2: Pyoderma of unknown etiology, may be autoimmune.
• Fig. 3  Deep Pyoderma showing abscess with necrotizing fascitis.
• Fig. 4  Stress related pyoderma in a 15 month old rat - Selene.
• Fig. 5  Superficial pyoderma in a 28 month old male rat - Ritchie.

Diagnostics

Any or all of the following may help to diagnose what what may be responsible for the occurring pyoderma.

Try to identify the type of lesions, if there is swelling, pus, ulceration or tunneling, and if loss of hair is present.

A hallmark of tissue invasion by staphylococcus aureus is a pus producing inflammation. It also has the ability to tunnel through and break down connective tissue.

Obtaining smears from intact pustules may help to determine bacteria involved.

Gram stain of affected tissue.

Skin scrapings for parasites, however, parasites may still be present even though the scrapings are negative.

Fungal culture for the presence of dermatophytes.

Skin tests for allergic or atopic dermatitis.

Work-up for metabolic or endocrine disease.

Try elimination diet provided in Food Allergies listed in the Rat Health Guide.

Treatment

In all cases as in dermatitis:
Clip toenails of rear feet to prevent increased trauma to lesions from scratching.

Surface Pyodermas

Application of topical therapy using skin cleansers, shampoos, creams, gels, or lotions can be used if appropriate.

Bathe affected area with a 1% Chlorhexidine, or 1% Chlorhexaderm solution, or Oxydex (contains Benzoyl Peroxide 2.5%) shampoo two times a week or as often as every other day depending on severity of condition. Allow affected area to remain soapy for 10 to 20 minutes. Prevent rat from licking or eating shampoo. Dry thoroughly and apply ointment if appropriate.

Topical antibiotic cream for use with surface or superficial pyoderma:

• Vet Aloe Vera cream
• Bacitracin and Polymixin B (for Gram-negative), not to be used in the presence of purulent exudate.

The use of a systemic antimicrobial, although not generally needed with surface pyodermas, may be required if topical agents do not resolve the condition. See listing under Superficial Pyodermas.

Superficial Pyodermas

Use of both topical therapy and systemic antimicrobials as appropriate.
Recommended antimicrobials should be used for approximately 21 days or longer and continued for a week following resolution of lesions. Refer to the Rat Medication Guide for information on medications.

• Cephlasporins
• Clavamox
• Trimethoprim-Sulfa

For treatment modalities of parasitic infestations see Ecto-Parasites on the Rat Health Guide Index page.

For treatment of fungal infections see Dermatophytosis on the Rat Health Guide Index page.

Deep Pyodermas

Systemic antimicrobials as noted above, as well as one of the aminoglycosides (e.g., amikacin or gentamicin) may be used.

Streptococcus spp. remains sensitive to Penicillin G, along with the addition of Clindamycin (dosages for these two drugs not yet listed in the Rat Medication Guide. veterinarian to extrapolate dosage for rats), if this bacteria is believed to be involved.

Possible debridement may be required.

For surface, superficial, and deep pyoderma, corticosteroids such as: prednisone or prednisolone may be needed to reduce inflammation, swelling, or acute pruritus (itching) if present.
*Note: Antihistamines like diphenhydramine/Benadryl or chlorpheniramine/Chlortrimeton may be used if corticosteroids are not advised or need to be reduced.

Nursing Care

• Use chlorhexiderm, or chlorhexidine at a concentration of not greater than 1%. Diluted solution should appear lighter than a robin’s egg blue.
• Wash hands before care and after care to prevent further infection.
• If rat persists in scratching affected area:
  May apply a 1” width self-stick vet wrap (e.g. Co-flex wrap) to the hind feet, like socks, to reduce the intensity of the scratching. *Important Note: do not wrap so tightly as to impair circulation.
• Continue treatment or followup care until healing occurs, or if no improvement discuss change of medication treatment with veterinarian.
• If antibiotics are given remember to include Benebac, or yogurt with live active cultures, to prevent normal gut flora from being destroyed by the antibiotics.
• Provide safe environment to help prevent traumatic injuries to skin or mucosal surfaces.
• Look to eliminate offending causative agent.

Outcome

• Infection resolved.
• Lesions healed.

Prevention

• Eliminate use of known litters to cause problems such as cedar and pine.
• Freeze CareFresh Litter prior to using to reduce chance of ecto-parasite infestation.
• Thoroughly rinse cages when cleaning them with antiseptic solutions, prior to placing rats back in cages.
• Refrain from serving foods known to cause allergic reactions such as peanuts/nuts.
• Treat infestations of mites, lice, or fleas, early.
• Assess skin on a daily basis and seek treatment advice from a veterinarian if signs and symptoms present.

Posted on June 25, 2003, 10:15, Last updated on April 28, 2009, 13:29 | Integumentary / Skin