Ulcerative Pododermatitis

Common name: Bumblefoot

Definition

The inflammation and infection of the plantar surface and connective tissue of the foot/feet.

Clinical Signs

May observe any of the following:

Raised, reddened tissue on the sole of one or both hind feet.
Open sore or ulceration on the sole of one or both hind feet.
Intermittent bleeding from the ulceration.
Presence of pus if the area is abscessed.

*Note: for information on recognizing various signs of pain or discomfort refer to: Signs of Pain In Rats.

Etiology

Ulcerative pododermatitis is a chronic granulomatous condition resulting from ulcerative lesions, and necrosis of the tissue on the plantar or heel portion of the feet.

The lesions, often resulting from abraded tissue or pressure, begin as small, reddish, raised areas of keratinized growth that develop crusts/scabs. Intermittent bleeding results when these areas filled with blood break open, drain, and then close. If the area is abscessed, then along with the blood, pus fills the area and drains upon rupture. This cycle is repeated when continuous pressure is placed on these raised, filled areas of tissue.

Secondary bacterial and fungal infections often develop when the abraded or ulcerated areas on the feet are exposed to normal skin flora, soiled bedding, or cages with accumulated urine-soaked feces. If the wounds are left untreated, or if treatment is not effective, infection can spread to the lymphatic system, to the bone causing osteomyelitis, or travel to the blood causing bacteremia and sepsis. If there is secondary infection Staphylococcus aureus is the bacteria most often cultured; however, other pathogens can be involved.

Factors that may play a part in the development of ulcerative pododermatitis are: rats that are overweight with or without hind limb neuropathies which places continued or excessive pressure on the feet, trauma, or minute abrasions from rough or irregular cage flooring, or rats having a genetic predisposition. It is also thought that the use of pine or cedar shavings used to cover cage flooring may play a part.

Although ulcerations of this sort, if caught early, can be cured, the treatment may require weeks to months of diligent care. It is also important to try to determine the underlying reason and correct it, or the condition is likely to return.

In cases where conservative treatment has been unsuccessful, or when surgical debridement has failed in more advanced conditions, amputation of the foot may be required. For cases such as these the prognosis is guarded.

Overall, it is by far easier to try and prevent ulcerative pododermatitis than to affect a cure.

Figures

Case Histories of Ulcerative Pododermatitis

Fig. 1: Ulcerative pododermatitis of both feet
Fig. 2: Ulcerative pododermatitis in male rat (Lance)
Fig. 3: Ulcerative pododermatitis and Blu-Kote application in male rat (Stu!)
Fig. 4: Ulcerative pododermatitis (Snowy)

Diagnostics

Assess for ulceration, bleeding, necrosis and infection.

Obtain a history for causative factors.

Culture and Sensitivity.

Treatment

Recommended treatment includes: cleaning lesions with an antiseptic solution, the application of a topical antibiotic ointment, as well as including an oral broad-spectrum antibiotic.

The following are various treatment options.

Clean ulcerations using an antiseptic soap and water, or a 1% dilute solution of chlorhexiderm/chlorhexidine flush. Apply Blu-Kote spray (wound medication for horses found in feed stores) to wound area at least two times a day, or more if the feet become soiled. An alternative to Blu-Kote is Granulex spray.
Clean ulcerations using an antiseptic soap and water, or a 1% dilute solution of chlorhexiderm/chlorhexidine flush. Apply Zymox (ear cleanser) otic solution to ulcerative areas, with or without hydrocortisone, depending on inflammation present. Give broad-spectrum antibiotic Clavamox (amoxicillin-clavulanate) orally.
Cleaning the ulceration with a Betadine solution (dilute to color of weak tea), and then applying a Betadine ointment at least three times a day.
Cleaning of the ulceration and application of Polysporin or Bacitracin topical antibiotic ointment along with Blu-Kote application if bumbles are persistent.
Cleaning ulceration with antiseptic solution and apply DILUTED tea tree oil to the bumbles several times each day.
*Note: tea tree oil contains phenol-containing essential oil. Active ingredients are cyclic terpenes which are similar in structure and action to turpentine. There have been reports of toxicity after consuming tea tree oil by mouth. There has also been reports that when applied to the skin, tea tree oil can be mildly irritating, resulting in the development of allergic contact dermatitis. If choosing to use this agent be sure to adequately dilute the tea tree oil, and do not let the rat lick the area.
Cleaning the ulceration with antiseptic solution and apply diluted Grapefruit Seed Extract (found in Health Food Stores) to the ulceration several times a day. (Recommended by Virginia Simpson, RMCA member.)

Alternative Meds: Give Grapefruit Seed Extract (GSE) orally.

Use 1 drop per 10 pounds of rat. Mix as 1 drop GSE for 9 drops fruit juice per dropper in a dropper bottle so each drop of juice contains 1/10th of a drop of GSE. Give 1 to 2 drops on a piece of bread twice daily. Store in refrigerator.

Refer to Nutriteam: Pets and Grapefruit Extract — Archived page from 2018-02-07 (via the Wayback Machine) for more information and ordering.

In persistent, difficult to treat bumbles, where previous treatments have not achieved desired results, the following solution may be mixed, by or per order of the veterinarian, for application once or twice a day to the bumble as directed.

In the event an oral medication would be required any of the following may be prescribed by the veterinarian. Dosages can be obtained by reviewing the Rat Medication Guide:

Trimethoprim/sulfa
Enrofloxacin
Clavamox
Flagyl (where anaerobic bacterial infections are suspected or confirmed)
Ketoconazole (where fungal infection is suspected or confirmed)

Treatment and the healing of bumbles may take up to several weeks, or be persistent throughout the life of the rat. What is important here is that the treatment chosen, if showing signs of effectiveness, should be continued until the ulceration is healed. If signs indicate that the ulceration is not improving over time, or in the event there are signs of further infection both locally or systemically, the treatment needs to be reevaluated and changed.

In any case a veterinarian should be consulted, especially if condition worsens or fails to resolve with any prescribed treatment.

It is also important to note that while debridement may be an option in severe cases of ulceration where necrotic tissue or abscess is present, or where more conservative treatment has been unsuccessful, it often poses greater difficulty due to the fact that rats normally do not have a great deal of tissue or adequate blood supply on that portion of the foot.

In cases that are very severe where surgical intervention may be required, there is the risk that the rat will require amputation of the foot. (See article BumbleFoot by Mary Ann Isaksen, RMCA Founder.)

Medication that may be used for pain control when surgical intervention is required:

For severe pain or first 24 hours post-op: Buprenex (buprenorphine), or Torbugesic (butorphanol).
For mild to moderate pain: Banamine (flunixin meglumine), Metacam (meloxicam), or carprofen. Do not use if a corticosteroid has already been prescribed.

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.
When applying Blu-kote, allow time for the application to dry as much as possible (or as rat allows). This ointment does tend to be messy and will stain.
Maintain cleansing treatment and ointment applications until ulcerations are healed.
If antibiotics are given remember to include Bene-Bac or yogurt with live active cultures in order to prevent normal gut flora from being destroyed by the antibiotics.
During treatment, provide clean bedding daily such as felt, soft t-shirt type material, or ink-free paper towels. Avoid litter-type bedding during treatment to prevent contamination or infection if wounds are present, and to prevent the litter from sticking to medicated areas of the foot or feet.
Monitor for extent of bleeding in order to prevent anemia.
Maintain healthy diet and reduce percentage of fat intake. Reduce number of treats if rat is overweight.
If no progress in healing is seen after several weeks, or if rat shows signs of further ulceration, abscess, foul smelling pus, or general apathy, contact veterinarian.

Outcome

Ulcerations heal
Ulcerations do not develop into septic condition
Healthy weight obtained

Prevention

Do a head-to-toe physical assessment of your rat weekly, paying attention to the soles of feet. Clean and treat any cuts or abrasions found to prevent infection.
Maintain a clean cage environment.
Cover portions of, or any irregular areas in, wire-floored cages. Examples of coverings can include vinyl floor covering, plastic needlepoint canvas, carpeting, towels, self-stick tiles, plastic placemats, fiberboard, and Plexiglas.
Use of litter boxes will help to prevent continued walking on either rough or soiled litter.

References

Atwal, R. (2003). In vitro antimicrobial activity assessment of Zymox otic solution against a broad range of microbial organisms. The International Journal of Applied Research in Veterinary Medicine, 1(3). Retrieved November 21, 2008, from http://www.jarvm.com/articles/Vol1Iss3/Atwal.htm.