Sore Hock or Ulcerative Pododermatitis in Rabbits

What are sore hocks?

Ulcerative pododermatitis, ‘sore hocks’, or ‘bumblefoot’ in rabbits is a bacterial skin infection that predominantly affects the bottom of their feet as well as hock - the part of the hind feet near the elbow that rests on the surface while a rabbit is sitting or resting.

When a rabbit is moving or hopping all its weight rests on its toes (i.e., rabbits have a digitigrade locomotion) and while it is resting, sitting, or on plantigrade stance, most of its “weight is borne on the area between the hind claws and hock.” [1]. Since they do not have footpads like cats and dogs, they rely on fur protection.

Anything that will affect a rabbit’s digitigrade locomotion making it move on its hock for instance or whatever disrupts the fur cushioning may be a triggering factor for ulcerative pododermatitis including poor conformation and posture.

Constant pressure on the feet bottom and hocks can cause a ‘pressure sore’ that will lead to the disrupted blood supply, tissue death, irritation, and pain especially if rabbits sit on a place without a soft, solid surface such on a wire mesh flooring.

Therefore, excess pressure will not only cause calluses, pain and irritation but also hair loss on the affect areas and it may also cause skin damage resulting in open wounds or ulceration and secondary infections.

In the beginning, the ulceration can be superficial. However, if left untreated, it could deep, and it can occur with osteomyelitis (bone infection). Also, your rabbit may have pus-filled lesions or abscesses.

Causes and risk factors

This is both a health and welfare problem predominant in rabbits housed in units (cages and hutches) have a wire mesh floor [2], overweight and obese rabbits or those kept in small hutches that allows minimal movement with no space to exercises forcing them to spend most of their time in a sitting or resting position.

Why you need to avoid the wire flooring is because they do “not allow the rabbit to walk or rest on its claws so the weight is taken entirely by the hock and metatarsus.” [3]

Other causes and risk factors include:

• The size and breed – “large breeds are affected more often than small breeds, and specific breeds like Rex or Angora more often than others” [4]. Also, those with thin or short fur on their hocks are more vulnerable as opposed to breeds such as Holland lops that have more fur in this area.
• Adult ones are more vulnerable as opposed to young ones.
• Besides the hutch and cage floor with a wire mesh floor, a hard surface (vinyl or concrete), irregular and rough surface can also cause abrasion (increase shearing and friction on the rabbit’s skin). Furthermore, the hard surface does not allow claws to sink into them and the metatarsus bone bears most of the weight.  
• Infections by bacteria such as commonly Staphylococcus aureus and others including Pasteurella multocida, Proteus spp., Escherichia coli or Bacteroides spp. can cause this condition.
• Poor hygiene that might encourage bacterial overgrowth in their living environment
• Constant encounters with moisture such as on wet or damp housing floors or rabbit bedding can make their feet moist increasing the infection risks.
• Some behavioral factors such as repeated hind leg thumping on the floor often caused by stress and fear.
• Pododermatitis is common in humid and warm weather conditions
• Aging makes some breeds such as the New Zealand white to lose hock fur
• Musculoskeletal diseases or conditions that cause pain and affect normal movement including spondylosis, arthritis, hind-end paralysis, and ataxia may cause urine scald, feces stuck on their feet, and stay in one place for a long time. This can trigger flystrike.
• Recent research claim that spayed does are more likely to develop this problem when compared to a male since they will be less active and have a higher chance of being obese. [5]
• Hock fur clipping, bad posture, trauma on hock or feet may be a contributing factor.
• Pregnancy (increases pressure due to weight)
• A gastrointestinal and urinary disease that may cause diarrhea or any condition that may cause excessive urination, may cause feces to be stuck to their feet as well as urine scald. 

Symptoms of pododermatitis

Behavioral changes such as reluctance to walk, appearing to be lame, preferring one leg may be an indication of this condition.

Other signs to expect include cellulitis, “loss of hair on the affected foot (alopecia), thickening of the skin, swelling, redness (erythema), and sometimes open, draining areas or scabs” [6]. The hocks can also be sensitive to touch.

It is also possible for the rabbit to be stressed and refuse to eat primarily due to the pain it may be experiencing.

The hard surface may also cause pressure sores. In this case, soft tissues may be trapped or lodged into the bone. Lethargy is another possible symptom that your rabbit may have.

All these symptoms can be divided into stages that note the severity and they are as following:

• Grade I – It’s in its early  stage, characterized by hair loss on hocks and feet
• Grade II– Redness, swelling and skin loss. The disease is mild.
• Grade III– The disease is now moderate. You expect hair loss, swelling, red skin, ulcers as well as the formation of scabs.
• Grade IV– A severe stage with symptoms such as redness, swelling, red skin, hair loss, abscesses, tendon or deeper tissue inflammation as well as scabbing.
• Grade V – This is a severe and often irreversible stage. There will be hair loss, ulcers, scabs, swelling, osteomyelitis, swollen joint tissue, deeper tendon and tendon involvement, and an abnormal stance.

If this condition is very painful, teeth grinding may be notice accompanied by anorexia, weight loss, and possible death if it is left untreated.

Diagnosis

Physical observation, bloodwork, bacterial culture (to help select the right antibiotic) and radiographs (X-rays) to determine if the infection has entered the bone might be necessary. An ultrasound may also be done by your vet to know if there are other causes of pain and their depth.

Treatment and recovery

Treatment involves pressure relieving and treating secondary infections. Depending on the severity, the vet may recommend outpatient care for mild cases of redness and hair loss or inpatient where bandaging, wound care and surgical procedures are necessary. Here are some of the common treatment options:

• For grades, I and II, provide your rabbits with dry, thick (deep) and soft bedding including hay, shredded paper, peat moss, straws, among other bedding alternatives. Avoid smooth hard surfaces.
• Severe cases may require regular dead tissue removal, bandaging, pain control medications, and antibiotic use. Bandaging is recommended for open wounds or after surgical tissue removal. The bandages must be changed whenever they are soiled. Liquid bandages such as Nu Skin or Germolene are often preferred to traditional or protective ones as the rabbits will remove the protective bandages.
• Trim hair around the wound to avoid it extending to the wound.
• Medications will include pain medicines such as carprofen, meloxicam, and butorphanol, especially after a surgical procedure.
• Antibiotics are only used for severe cases of infection and abscesses. They are not recommended as they can alter the intestinal bacteria and microorganism balance. Some of the safely prescribed antibiotics include enrofloxacin, marbofloxacin, ciprofloxacin, chloramphenicol, trimethoprim-sulfa or azithromycin. In the case of Penicillin, only injections are recommended.

For mild cases of infection, topical antiseptics including “salicylic acid (0.006%), medical-grade manuka honey” [7], Mupirocin 2%,  Neomycin 2%, Neomycin 2% and  Calendula/Echinacea 5%  may be recommended[8]

Prevention

Prevention will involve dealing with the various risk factors and causative agents with revolves around proper housing, the right diet, exercise, hygiene and treating underlying diseases.  

• Provide proper diet to avoid GI infections including GI stasis, enteritis, among others.
• Manage obesity as the excess weight may discourage physical activities and put pressure on the feet and hocks.
• Provide the recommended rabbit cage size as small ones will limit movement.
• Provide, dry, soft and stable surfaces and provide separate littering trays and bedding places to avoid them spending much time of their bedding area as they may be soiled. Remove any soiled substrate and regularly change the substrate.
• Encourage them to exercise by providing them a playpen or run enriched with the various rabbit toys.
• Regularly groom your furry friends to remove any feces stuck on their feet and clip their nails too.

Conclusion

Ulcerative pododermatitis is largely a husbandry and handling problem with few instances of anatomical conformation. Put in place prevention measures and early begin treatment to improve prognosis as some of the symptoms may be irreversible including fur regrowth, amputation, and so on if the condition advances.

In some cases, septicemia and anorexia can lead to the death of a rabbit. Ensure you seek help from a vet in case infections are serious.