Bumblefoot (ulcerative pododermatitis) is a painful condition in rats that causes ulcers on the bottoms of the animals' feet. It's not contagious to humans, but can be fatal to rodents if left untreated. Bumblefoot is relatively easy to prevent; basically, all an owner has to do is keep a pet rat's cage clean and dry.
This condition usually develops when a wound on the animal's body becomes infected with Staphylococcus aureus or E. coli, often due to unsanitary conditions in the animal's enclosure. The infection leads to chronic inflammation and abscesses, and the name "bumblefoot" refers to the red lesions or "bumbles" that develop on the feet that cause the animal to limp.
It often occurs in rats that are obese, or that have a genetic predisposition to the ailment. Rabbits, birds and other rodents are also susceptible to bumblefoot, but in rabbits, it's more commonly referred to as "sore hocks." Bumblefoot is also a major problem in chickens kept in captivity, particularly those kept in large numbers in small enclosures.
Bumblefoot starts out as small reddened bumps that look a bit like calluses. These bumps can eventually become quite large and may intermittently bleed and scab over. Limping, excessive licking of feet, bloody footprints, or a rat that is reluctant to walk or climb much may indicate that the animal has developed bumblefoot. It can be hard to spot bumblefoot at first since the lesions first appear on the soles of the animal's feet.
There's a fair amount of disagreement about what cages or cage conditions may contribute to bumblefoot. Trauma from irregular cage surfaces or roughly textured bedding materials may play a role, and waste left in the animal's cage is thought to be a factor as well. Rodents may pass bumblefoot to each other, especially if they're kept in the same enclosure.
Obese animals, rats included, appear to be more likely to develop bumblefoot. This may be due to uneven weight distribution or excessive pressure on the feet and legs when the animal walks. This is especially true in older rats, who naturally walk more slowly.
The use of wire-floored cages, including wire shelves or balconies, has been suggested as a possible cause of bumblefoot. Wire cage floors should be avoided, but many decent rat cages have upper levels made from wire mesh. However, even rats kept on solid flooring can get bumblefoot, with one theory suggesting that exposure to urine pooled on solid floors (especially plastic) may contribute to the problem.
Whatever the specific cause, bumblefoot is almost exclusively a disease of animals kept in captivity, so keeping enclosures clean and free of irritants is crucial.
If you notice your pet rat has a cut on its body or feet, immediately clean the affected area and clean and sanitize its enclosure. At the first sign of bumblefoot, see your veterinarian. A combination of oral antibiotic treatment along with topical cleaning and treatment of the wounds (as directed by your vet) is usually the first course of treatment.
For bumblefoot lesions that do not respond to this basic treatment, surgical treatment may be necessary, but this has significant risks and limited success. Early detection and treatment are vital for the best results, but even then, some cases may not respond well. Amputation of badly infected toes and feet is sometimes called for in severe cases of bumblefoot.
You'll want to seek out a veterinarian familiar with treating rodents if you haven't already. He or she may want to conduct culture and sensitivity tests on your pet, to determine which bacteria may have caused the infection in the first place. That's the best way to determine which antibiotic will be most effective in treating your rat's case of bumblefoot.
If the disease is left untreated, the infection can spread to other tissue in the animal's body, and cause it to die a slow, painful death. The earlier bumblefoot is identified and treated, the better, but ideally, you should take steps to prevent your animal from contracting bumblefoot in the first place.
Though the factors that lead to bumblefoot are not always present in every case, prevention of trauma or abrasions to the feet and keeping the cage and bedding meticulously clean and dry are the cornerstones of prevention (this goes for other infections as well as bumblefoot).
Rat owners should consider covering wire floors in their animal's enclosure with a solid surface, such as wood, vinyl, Plexiglass, plastic needlepoint canvas, Vellux blankets or towels. Flatter surfaces seem to cause less stress on rats' feet, and will likely result in fewer abrasions that may become infected with the bumblefoot-causing bacteria.
Remove soiled bedding as soon as possible and change it frequently. Using a litter box in your rat cage can help keep their bedding cleaner longer (although there can be a bit of a learning curve involved; rats and mice don't take to litter boxes as readily as cats do). In addition to walking more slowly as mentioned above, older rats may also walk more flat-footed, so be sure to provide soft bedding and surfaces for older or weak rats.
Prevent your rats from becoming overweight by providing a healthy diet and lots of opportunities for exercise. Rats' diets should consist of rat block or pellets, and to prevent overweight, try to limit treats (although the occasional supplement is fine).
Regularly check your rats' feet for abrasions, trauma, or early signs of bumblefoot. This will allow you to detect and treat any wounds early, preventing the painful abscesses and bumps associated with bumblefoot. It may also alert you to potential problems in your rats' cage or with the bedding that may be able to be corrected to help prevent further problems in the future.
Mecklenburg, Lars et al. Proliferative And Non-Proliferative Lesions Of The Rat And Mouse Integument. Journal Of Toxicologic Pathology, vol 26, no. 3_Suppl, 2013, pp. 27S-57S. Japanese Society Of Toxicologic Pathology, doi:10.1293/tox.26.27s
Bumblefoot (Pododermatitis) in Rodents. Sawneeanimalclinic.Com, 2020
Bumblefoot in Companion Rodents. U.S. Department of Agriculture Cooperative Extension, 2020