Background: Dermatological conditions are a very common presentation of pet rabbits to the veterinarian. The aetiology varies; problems such as pododermatitis and parasitic and bacterial infections constitute a higher percentage of these cases, while viral infections are considered less common. Stress and pain also play an important role and should be considered during the initial consultation and treatment planning.
Aim of the article: This article provides an overview of skin diseases that may be presented to general veterinary practitioners, helping the practitioner to approach these cases with more confidence.
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Livia Benatoqualified from the University of Parma, Italy in 2002. She gained a certificate in zoological medicine in 2009 and completed a residency in rabbit and exotic animal medicine at the University of Edinburgh in 2011. She is an RCVS-recognised Specialist in zoo and wildlife medicine (mammalian) and a European-recognised Specialist in small mammal medicine. She currently works at CityVets in Exeter as a small mammal and exotics veterinary associate.
Key learning outcomes
After reading this article, you should:
Understand the basic approach to rabbit dermatology;
Know the most common clinical presentations and how to make a differential diagnosis;
Be able to distinguish between primary and secondary causes of a dermatological disease in rabbits;
Know the diagnostic tools and tests available for rabbits;
Be able to choose an appropriate management and supportive treatment programme.
Skin disorders are among the most common presentations of rabbits to veterinary practices. A UK survey showed that 25 per cent of rabbit cases treated by veterinarians were related to skin problems, second only to dental diseases (30 per cent) (Nielsen and others 2014). In a similar study, skin diseases were reported to make up 29 per cent of all cases treated in California, USA, with pododermatitis being the most frequent condition encountered (25 per cent of cases), followed by abscesses (20 per cent) and alopecia (16 per cent) (Snook and others 2013). However, in a survey on the health status of pet rabbits in Finland, it was found that skin conditions only made up 16 per cent of all cases, after dental disease and vertebral column problems (Mäkitaipale and others 2015). As the authors of this study suggested, rather than this lower percentage representing a lower prevalence of dermatological cases in Finland, it could be due to the fact that rabbits are not vaccinated against myxomatosis and rabbit haemorrhagic disease. These two diseases are not present in Finland and therefore rabbit owners may be less likely to take their pet rabbits to the vets for their annual health checks, where other conditions, such as dermatological diseases would be picked up. This highlights the importance of regular health checks to detect health problems that may be more subtle and less obvious to owners.
Age, sex and breed of the animal do not seem to have an impact on the type of skin disease that rabbits might develop (Snook and others 2013). However, this could be due to unexplored areas or insufficient findings of the few studies reported in the literature. Further research should focus on these areas with the aim of improving our understanding of dermatological problems in pet rabbits.
There are few licensed products available for use in pet rabbits in the UK; veterinary surgeons are reminded to consider guidance on prescribing under the cascade when dealing with rabbits. Furthermore, care should be exercised when administering certain antibiotics given the risk of causing enteritis. Rabbits are usually not treated with parenteral or topical steroids given the potential risk of side effects, especially immune suppression. Using topical products such as antimicrobial soaks should be applied with care given the risk of stress and hypothermia in debilitated rabbits. For further information on the use of antibiotics see Hedley (2018).
Common clinical presentations
In review articles (Snook and others 2013, Rooney and others 2014, Mäkitaipale and others 2015, Robinson and others 2015), the most common clinical signs reported to be associated with skin disease in rabbits (Table 1) are:
Accumulation of the faeces in the perineal region.
Alopecia has been described as ‘a decrease in amount or absence of hair’ (Jackson and Marsella 2012). Several pathological and non-pathological skin conditions can lead to either localised or diffuse alopecia.
Pregnant does close to giving birth will exhibit nesting behaviour and pull fur from the dewlap and the ventral abdomen to create a nest for the kits. This is normal rabbit behaviour and generally treatment is not required. However, it can also be seen in rabbits experiencing pseudopregnancy due to a hormonal imbalance following unsuccessful mating, or in does kept as a single pet. In these cases, rabbits also exhibit aggression and frantic behaviour due to stress. Clinical signs can resolve following ovariohysterectomy.
Barbering is also an abnormal behaviour due to dominance: the dominant rabbit overgrooms the submissive rabbit, causing lesions on areas which the submissive rabbit would not be able to reach itself. Risk factors for barbering are stress, overcrowding, boredom and general suboptimal husbandry. The alopecic areas present with broken hairs, but no signs of irritation and inflammation of the skin. Behaviour modification, such as positive reinforcement and removal of the cause of stress, may help to address the problem. In severe cases, rabbits should be separated.
Skin problems such as ectoparasite infestation, dermatophytosis, cutaneous and ovarian tumours can also lead to hair loss, often alongside other clinical signs. Ectoparasite infestation and dermatophytosis would present as broken distal hairs on a trichogram, whereas ovarian tumours may cause shedding of the whole hair with no broken shafts.
Moist dermatitis is an irritation and inflammation of the skin due to continued contact with moisture. It is generally localised around the chin and dewlap due to hypersalivation when dental disease is present.
Periocular dermatitis is secondary to tear overflow and ocular discharge due to ocular problems and dacryocystitis caused by chronic dental disease and infections of the tear duct (Fig 1).
Perineal moist dermatitis develops due to prolonged contact with urine (urine scalding) and faecal matter. Superficial pyoderma can occur if the primary cause is not addressed. A bluish colour of the area could indicate infection due to Pseudomonas aeruginosa. However, Staphylococcus aureus is generally the most common pathogen detected in skin conditions (Varga 2014). In mild to moderate cases, topical antibiotic treatment is often sufficient, while the underlying problem is investigated.
Scaling is the accumulation of large flakes of the stratum corneum on the coat (Patel and Forsythe 2008) (Fig 2), due to abnormalities of the desquamation process. It is often secondary to inflammation caused by ectoparasites such as mites and lice, and dermatophytosis. An exfoliative dermatitis has been associated with sebaceous adenitis and thymoma, with rabbits presenting with generalised scaling, alopecia and erythema of the skin (Prélaud and others 2013).
Swelling and nodules
The most common cause of swelling in rabbits is localised bacterial infection that develops into abscesses. Facial abscesses are the most common and they are often associated with dental problems. However, ear base abscesses are also commonly reported (Fig 3), affecting mainly lop-eared rabbits. Ear base abscesses should be investigated because they are often associated with otitis externa and media.
Nodules are generally described as a ‘solid elevation’ of circa greater than 1 cm, and they are commonly seen during myxomatosis infection. The main differential diagnosis is an infection due to the Shope papillomavirus. Other causes of nodules are mammary carcinoma and adenocarcinoma, characterised by small subcutaneous nodules.
Pododermatitis, also known as ‘sore hocks’, is one of the most common dermatological conditions; in a study by Mancinelli and others (2014) it was found to be present in 93.8 per cent of cases. It is characterised by pressure sores of the tarsal and metatarsal areas (Varga 2014) (Fig 4). Predisposing factors can lead to skin inflammation, ulceration and infection and, in severe cases, loss of the pedal function when bones and tendons are affected.
The most common causes include poor husbandry, hard flooring, obesity and musculoskeletal problems, such as arthritis. The diagnosis is made during clinical examination of the pedal region, with a 0 to 6 scoring system (pet rabbit pododermatitis scoring system), where ‘0’ represents no lesions and ‘6’ represents loss of pedal function (Mancinelli and others 2014). In severe cases, radiological examination should be carried out to assess the involvement of bones and tendons.
In mild cases, Sudocrem (Forest Tosara) can be used to reduce inflammation. However, in moderate and severe cases, the area should be thoroughly debrided and cleaned, and medical treatment (ie, antibiotics and analgesia) should be given. The underlying cause must be investigated and addressed.
Common dermatological conditions
Fur and ear mites
Mites are found on the skin of rabbits as part of the normal fauna. However, problems such as immunosuppression secondary to chronic stress or pain, inability to groom due to obesity or musculoskeletal problems such as arthritis, and suboptimal husbandry can lead to an increase in the number of mites and the development of clinical signs. Mite infestation is always secondary to an underlying problem that should be addressed and treated. In all situations, rabbits that are in contact with the patient should be considered to be infested and therefore treated.
Fur mite infestation, also known as ‘walking dandruff’, is caused by Cheyletiella parasitovorax (Fig 5), a superficial mite that lives on hair and fur and feeds on keratin. The clinical signs consist of excessive scaling, clumps of hair falling out and dermatitis. Pruritus is reported but may not always be present. It is generally found dorsally on the back of the neck and between the shoulders (Fig 2). However, in severe cases, it can affect other areas of the skin. After a physical examination, acetate tape strip examination is the main diagnostic test. Coat combings examined in liquid paraffin, superficial skin scraping and demonstration of eggs on hairs may be useful also for the detection of C parasitovorax. Treatment consists of topical application of ivermectin (Xeno; Dechra) every 10 to 14 days, up to three times or 6 to 12 mg/kg selamectin (Stronghold; Zoetis), repeated every two to four weeks, or until the resolution of the clinical signs. Cheyletiella mites can be zoonotic, with transmission occurring by direct contact with infected animals.
Another mite that also has a potential zoonotic implication is Leporacarus gibbus (Fig 6). This mite is associated with a highly pruritic dermatitis and alopecia. Diagnosis using only an acetate tape test can be difficult as the mite is located in the distal third of the hair shaft, and so a combination of tests, such as hair plucking and skin scraping, may be necessary. In one reported case of two rabbits, remission of the clinical signs was seen after one single application of a spot-on treatment containing 1 per cent moxidectin and 10 per cent imidacloprid, with concurrent environmental disinfection (d’Ovidio and Santoro 2014).
Ear mite infestation is caused by Psoroptes cuniculi, a non-burrowing mite that is found in ears and on the pinnae. In severe cases it can also affect the ventral abdomen, legs and perineal area. It is more likely to be found in younger rabbits (less than one year of age) due to an immature immune system (Snook and others 2013). The main clinical signs are pruritus, head shaking, and well-adhered crusts (Fig 7). If left untreated, infestation may lead to secondary bacterial infection and otitis interna. The condition is very painful and if the crusts are manually removed the skin can bleed profusely. The mites can be seen with the naked eye and a presumptive diagnosis can be made during a physical examination. A definitive diagnosis can be made by microscopic examination of the crusts and detection of the mites. Treatment consists of topical application of ivermectin or selamectin, as previously described for fur mites. The crusts will start to loosen within days. In the meantime, analgesia and antibiotic therapy should be started if necessary. Mites may persist in the environment so the rabbit’s hutch and bedding should be thoroughly cleaned to prevent reinfection.
The rabbit flea, Spilopsyllus cuniculi, can be found on both wild and pet rabbits. However, it is more common for pet rabbits to be affected by the cat and dog fleas Ctenocephalides felis and Ctenocephalides canis. The owner generally notices the animal scratching, and on physical examination fleas and flea faeces (dirt) are found dorsally on the back (Fig 8). Treatment consists of topical application of imidacloprid (Advantage; Bayer) at a dose of 0.4 ml for rabbits that weigh less than 4 kg and 0.8 ml for rabbits heavier than 4 kg, given once a month. Selamectin (Stronghold; Zoetis) is also found to be effective, although it is not licensed in rabbits. It is also advisable to treat all in-contact animals. Fipronil should be avoided because it can be toxic in rabbits and they can develop seizure and ataxia (Carpenter 2001). As a preventive measure, cats and dogs living in the same household should be treated regularly and the rabbit’s hutch and bedding thoroughly cleaned regularly.
Myiasis or fly strike is a condition that usually occurs in the summer but can affect rabbits throughout the year. It is caused by flies that are attracted to moist skin. The fly lays the eggs on the skin and the larvae (maggots) feed on the healthy skin. This is a problem that generally affects debilitated animals and those that present with problems such as caecotroph caking around the perineal area, urine scalding, primary or secondary skin wounds, arthritis, obesity and dental disease that prevents the animal from grooming properly. The clinical signs are generally associated with the irritation and damage of the skin caused by the maggots (Fig 9). However, the animal is often also anorexic and lethargic.
Treatment consists of clipping the affected area and manual removal of the larvae while the animal is under sedation. The area is then cleaned using warm 0.05 per cent chlorhexidine or 0.2 per cent povidone iodine solution. This should be repeated daily until no maggots are found and the wounds start to heal. The use of ivermectin should be used to kill the larvae and prevent further skin damage. Analgesia and supportive treatment, such as fluid therapy and assisted feeding, should be given in the meantime, while the primary problem is addressed. In my opinion, application of fly repellents such as cyromazine (Rearguard; Elanco) and F10 spray (F10 Germicidal Wound Spray with Insecticide; F10 Products) is advisable for those animals with chronic problems such as arthritis. Nevertheless, the animal should be kept dry and clean at all times to prevent the fly strike and euthanasia should be considered if the quality of life of the animal is poor.
Ringworm lesions are commonly seen in immunocompromised animals. The most common dermatophyte species in rabbits is Trichophyton mentagrophytes (Kraemer and others 2012). However, Microsporum canis and Microsporum gypseum have also been reported in rabbits (White and others 2002). A presumptive diagnosis can be made with the history and physical examination, where areas of hair loss, broken hairs and yellow crusts localised on the face, nose and ears and feet can be seen. Examination by Wood’s lamp is helpful for M canis infection only, because it is only the dermatophytes that fluoresce under the light. A definitive diagnosis can be made by trichogram, where fungal spores and broken infected hairs can be seen during microscopy. Fungal culture is generally recommended to identify the species, while skin biopsy can give information on the severity of the lesions and if any other concurrent skin problems are present.
A microsatellite primer PCR has been developed to identify rabbit dermatophytosis, clearly distinguishing between the three species T mentagrophytes, M gypseum and M canis, (Miao and others 2014). As rabbits can also be asymptomatic carriers of fungal infection (Canny and Gamble 2003), all in-contact animals should be treated. Treatment depends on the severity of the presentation and consists of either topical or systemic treatments. Topical treatment includes regular cleaning of the area using 0.05 per cent chlorhexidine or 0.2 per cent povidone iodine solution, in addition to application of creams containing enilconazole, clotrimazole or miconazole. Systemic treatment consists of oral treatment with itraconazole at a dose of 10 mg/kg once daily for two weeks or terbinafine at a dose of 8 to 20 mg/kg once daily for a minimum of two weeks. Griseofulvin may also be used, but it has teratogenic effects in rabbits and this should be taken into consideration in pregnant does.
Myxomatosis is a disease caused by the myxoma virus transmitted by fleas, mosquitoes, flies and mites. It is also transmitted by inhalation, direct contact with infected rabbits and by contact with infected objects such as hutches, bedding and food. The clinical signs are pathognomonic of this disease. An infected rabbit presents with swelling and oedema of the lips, nares, eyelids and genital area due to the replication of the virus in these tissues. The rabbit also develops flat, raised skin nodules, mucopurulent blepharoconjunctivitis and pneumonia due to secondary bacterial infections leading to death.
Atypical myxomatosis is also recognised and it affects vaccinated rabbits that get infected by the virus or that develop the infection after the administration of the vaccine. In this case, the rabbit only develops skin nodules that heal spontaneously. A definitive diagnosis of myxomatosis can be made via serology tests or skin biopsy and histopathology, with the identification of cytoplasmic inclusions. The best approach to this disease is prevention, and vaccination plays an important role. The first vaccination is generally given subcutaneously at the age of six weeks, with an annual booster.
Abscesses in rabbits are considered a common problem and are often associated with dental disease (Fig 10). However, they can be found in any part of the body and can be a consequence of otitis externa, trauma, bites from predators or fighting with other rabbits. Abscesses present with a thick fibrous capsule with poor vascularisation, making it difficult for antibiotics to penetrate it. The purulent material is thick and dense, as rabbits lack the lysosomal enzyme that digests dead cells transforming the pus into a liquid form. This makes it difficult to drain the abscess when it is lanced.
Therefore, treatment of abscesses can be a challenge and a medical approach alone is often unrewarding. A combination of medical and surgical treatment is considered the treatment of choice as it has a higher rate of success. In one study, the most common organisms detected in odontogenic abscesses were anaerobic bacteria, such as Fusobacterium species, followed by Peptostreptococcus species, Bacteroides species, and aerobic bacteria such as P aeruginosa, Pasteurella species, Streptococcus species, Staphylococcus species (Gardhouse and others 2017). Choice of surgical technique (eg, removal of the entire abscess or marsupialisation) depends on the location and severity of the abscess. For culture and sensitivity testing, a sample of both capsule and pus should be taken; pus alone can sometimes be sterile. Antibiotics such as penicillin G (40 mg/kg given subcutatneously every 24 hours), metronidazole (20 mg/kg given orally every 12 hours or 40 mg/kg given orally every 24 hours) and enrofloxacin (20 mg/kg given orally or subcutaneously every 24 hours) proved to be effective in most cases and could be started while awaiting the bacteriology results (Tyrrell and others 2002, Taylor and others 2010, Gardhouse and others 2017). Radiographic examination and computed tomography can be useful to assess whether the infection has involved the underlying bone and soft tissues.
Urine scalding is a painful condition that affects the skin of the ventral abdomen and thighs (Fig 11). This is caused by prolonged contact with urine leading to skin inflammation and secondary infection. Several predisposing factors, such as polyuria due to, for example, Encephalitozoon cuniculi infection, renal disease and cystitis have been reported. It is also seen in rabbits that are unable to assume a correct stance while urinating, due to, for example, arthritis, general pain, limb amputation and obesity. Suboptimal husbandry and stress can also lead to urine scalding, especially in already debilitated animals.
The main clinical signs are erythema, inflammation, alopecia and matted and wet fur. Even mild urine staining of the perineal area should not be overlooked as it is a clear indication of a problem that should be addressed. Treatment consists of treating the clinical signs and addressing the primary cause and concurrent problems. The affected area should be clipped and gently washed with warm diluted chlorhexidine at a concentration of 1:10 with water or iodine povidone solution. Application of a protective cream such as Sudocrem (Forest Tosara) or Dermisol cream (Zoetis) can be beneficial to reduce the inflammation if the skin is not broken or infected. Otherwise, silver sulfadiazine cream (Flamazine 1 per cent w/w Cream; Smith & Nephew) should be applied topically. Analgesia should be administered to relieve the pain and to ensure the rabbit is comfortable while reducing the inflammation and treating the cause.
Uncommon dermatological conditions
Box 1 summaries uncommon dermatological conditions, reported in literature, that are sometimes present in rabbits.
Uncommon dermatological conditions reported in pet rabbits
Sarcoptes scabiei is a burrowing mite that causes intense pruritus and localised or generalised hair loss and crusts. It is generally found on the head but can also affect the perineal area. A diagnosis is made by superficial skin scrape examination under the microscope. The treatment is similar as for other mites. This is a zoonosis.
Demodex cuniculi: clinical signs and diagnosis are similar to those of fur mites. Anecdotal reports suggest treatment consist of 0.5 mg/kg ivermectin given subcutaneously once a week may be effective. Alternatively, 0.01% amitraz solution (1:500) can be used weekly.
Trombicula autumnalis is a harvest mite that lives in low vegetation, such as grasslands, and feeds on the skin of animals. It usually occurs only in the summer and autumn months. They are distinguished from other mites by the red colour of their body. Common clinical signs are pruritus and small papules that generally affect the head and feet. Thorough and deep cleaning of the rabbit’s hutch reduces exposure and prevents infestation.
Haemodipsus ventricosis is a sucking louse that can be found on debilitated and older animals. Treatment consists of administrating ivermectin. However, the concurrent underlying problem should be addressed.
Anorectal papilloma is a cauliflower-like growth that develops at the anal mucocutaneous junction. It can bleed profusely if touched. Although it grows slowly it can be quite painful for the animal. The aetiology is unknown. The treatment of choice is surgical resection.
Rabbit syphilis is a bacterial infection caused by Treponema cuniculi. It is transmitted via direct contact and venereal transmission. Clinical signs include swelling and crusting of the genital area, eyes, nose and lips (Fig a). A presumptive diagnosis is made during physical examination, while a definitive diagnosis can be made by cytological and histological examination. Treatment consists of weekly subcutaneous administration of penicillin G.
A case of mucocutaneous bacterial pyoderma has been reported in a rabbit. The rabbit presented with swelling and erythema of the mucocutaneous junctions of lips, nares and vulva and secondary bacterial infection due to Staphylococcus intermedius. Treatment consisted of topical and systemic administration of fluoroquinolone drugs (Benato and others 2013).
Dermal fibrosis is a thickening of the skin along the dorsum. The aetiology is unknown, although hormonal changes are suspected. Diagnosis is based on physical and histological examination.
Apocrine gland hyperplasia are subcutaneous masses most likely of sweat gland origin. Surgical excision is considered the treatment of choice (Benato and Morrison 2011).
Given that rabbits are living longer, skin tumours are more commonly seen by veterinarians. However, there are few case reports and even fewer retrospective studies on cutaneous neoplasia reported in the literature. Clinical signs associated with skin tumours are generally nodules and masses, but other signs such as alopecia, crusty skin and erythema can also be observed. The ability to properly diagnose them is important for successful treatment (Table 2).
Skin tumours reported in rabbits include lipoma, fibrosarcoma, trichoepithelioma, squamous papilloma, spindle cell sarcoma, squamous cell carcinoma, basal cell tumour, cutaneous lymphoma and mammary gland carcinoma and adenocarcinoma (von Bomhard and others 2007, Foale and Demetriou 2010, Ritter and others 2012, Kanfer and Reavill 2013, Varga 2014). Diagnosis of these tumours can be made by fine needle aspiration, surgical biopsy or removal and histopathology.
Surgical removal is the treatment of choice; however, prior knowledge of the type of a tumour is recommended for the resection of the margins (Hedlund 2007). Margin excision of 1 cm around the tumour is advisable for benign tumours, such as lipomas, while marginal removal greater than 1 cm (ie, 1 to 3 cm) should be considered for malignant tumours (Hedlund 2007). Radiography of the chest is indicated if a malignant tumour is suspected.
Dermatological diseases in rabbits can be a primary condition, or secondary to stress, pain and chronic conditions that need to be thoroughly investigated and addressed. Routine checks and examinations of the pet rabbit, both at home by the owner and at the veterinary clinic, are recommended in order to detect a condition at an early stage. This will not only prevent pain and discomfort, but it will also help to more quickly select the appropriate treatment, if necessary.
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