Dermatophilosis in Bears and Lagomorphs:

• Contagious dermatitis 
• Proliferative dermatitis 
• Mycotic dermatitis 

(B209.28.w28c)

See also: Bacterial Dermatitis in Lagomorphs

• Dermatophilus congolensis. (J4.167.w2, P1.1977.w1)
  • This Gram-positive bacterium has an unusual fungus-like morphology and life-cycle. (B209.28.w28c)
  • Dermatophilus is an actinomycete. (B614.8.w8)
  • This organism shows limited survival off the host. (J4.167.w2)

• Dermatophilus congolensis

• This bacteria can cause a superficial, purulent dermatitis with crust formation, in many species of animals. 

In Lagomorphs:

• Rabbits are susceptible to this disease and have been used in experimental studies of the infection. (B614.8.w8)
• Infection with Dermatophilus congolensis is reported to occur in wild rabbits in North America. (B209.28.w28c)
  • "Only one spontaneous case has been reported, and that was in a cottontail rabbit (S. floridanus)". (B614.8.w8)

Clinical findings

• The first feature noted may be areas of hair loss covered by thick scabs. (B209.28.w28c)
• Dermatophilus causes a marked epidermal hyperplasia and an inflammatory exudate; this results in the production of the thick crusts. (B209.28.w28c)
• Lesions are initially discrete areas with hair that is "held stiffly by an enveloping crust of layers of shed epidermis and exudate". (B209.28.w28c)
• These encrustations can be detached to reveal an underlying inflamed, red dermis that bleeds. (B209.28.w28c)
• In a naturally infected Sylvilagus floridanus - Eastern Cottontail, crusts of dry purulent material were mixed with hairs and were up to a quarter-inch thick. Under the crusts, which could be removed easily, the skin was deep red, covered in fibrinopurulent exudate. (J4.157.w7)
• Distribution of lesions:
  • Infection of the skin surface can occur anywhere on the body. (B209.28.w28c)
  • In a case of spontaneous infection in a Sylvilagus floridanus - Eastern Cottontail, lesions were found on the foot pads of the fore feet, on the hind feet from the foot pads up to the hocks, and around the anus and urethra, with two small lesions on the muzzle. (J4.157.w7)

Histopathology

In a naturally infected Sylvilagus floridanus - Eastern Cottontail: (J4.157.w7)

• Covering the epidermis, a mass of necrotic debris, keratinised epithelial cells, serum and leucocytes. 
• Stratum corneum appearing separated into layers due to focal exudate accumulation.
• Hyperkeratosis.
• Erosion of the epithelium.
• Dermis infiltrated by lymphocytes and neutrophils.
• Dermatophilus organisms: "narrow filamentous branching hyphae." 

(J4.157.w7)

Susceptibility and transmission

• Risk factors

  • Conditions that lead to persistently wet skin (this macerates the epidermis and provides a medium for zoospore motility). 
  • Cuts and abrasions 

  Transmission

  • Usually by direct contact with infected animals. 
  • Mechanical transmission by ticks and flies has been reported to occur in some wild mammals.

  (B209.28.w28c)

In Bears:

• Generalised dermatitis associated with Dermatophilus congolensis infection in Ursus maritimus - Polar bears. (B16.9.w9, B336.51.w51, J4.167.w2)
• Chronic infections in captive bears have been reported to last from two to ten years. (B16.9.w9)

Clinical signs

• In Ursus maritimus - Polar bear: 
  • Initially a hair colour change from white to yellow-white, diffuse exudation, hair matting and red wet skin beneath scabs. Hair dirty and yellow, skin and hair greasy, skin thickened, formation of crusts, and pruritus. Reluctance to bathe. Later detachment of scabs and hair from skin areas with resultant thinning of the hair coat and greying at the hair base. Eventually complete alopecia revealing black skin and occasional red areas of ulceration. Lesions usually occurred first on the dorsal head, thorax and lumbar area, spreading down the sides and onto the legs. (J35.128.w1)
  • Initially yellowing of the hair, then darkening and greasiness, progressing to formation of black, flattened clumps in the coat and eventually a crusty, dark scab material matting the coat; this may be present over most of the body. (J4.167.w2)
  • Associated pruritus. (J4.167.w2)
  • Bears with the coat encrusted with this material are reluctant to bathe. (J4.167.w2)
  • Thickening of the skin and pruritus in Ursus maritimus - Polar bears at Knoxville Zoo. Signs were worse in summer and considered to be exacerbated by the heat and abundant flies. (P1.1977.w1)
  • Chronic alopecia and urticaria in three Ursus maritimus - Polar bears. (P1.1981.w5)

Histopathology

• Skin:
  • Acanthosis, epidermal suppuration and microabscessation. There were alternating layers of purulent exudate and parakeratotic epithelium over the surface of the skin (grossly visible as the scab material).
  • Hair follicles: distended with keratinous debris.
  • Superficial dermis: increased vascularisation, inflammatory cell infiltration (mixed cell). 
  • On the surface of the epidermis, Dermatophilus congolensis filaments, often in dense aggregates.

  (J4.167.w2)

  • From biopsy or post mortem samples in five polar bears, dermatitis with acanthosis, parakeratosis and hyperkeratosis; the exudate was rich in neutrophils. The epithelium was two to three times normal thickness, due to epithelial hyperplasia, and on the surface was a thick layer of necrotic and cornified epithelial cells, degenerate neutrophils and coagulated proteinaceous fluid. There were foci of neutrophils between this layer and the epidermis. Lesions in hair follicles were similar but less severe; some follicles were distended with cellular debris and keratin, but usually the hair root was intact. In the epidermis, above the granular layer, and deep in the scabrous layer, were long, branching filamentous bacterial colonies, characteristic of Dermatophilus congolensis. Single cocci were present in superficial layers. In some areas, the corium adjacent to the epidermis showed mesenchymal cell proliferation and small perivascular inflammatory cell accumulations (lymphocytes, plasma cells and neutrophils). In some areas there was pronounced hypertrophy of endothelial cells. (J35.128.w1)

Transmission & Susceptibility

• Transmission is usually from an inapparent carrier individual. (J4.167.w2)
• Moisture is an important predisposing factor. (J4.167.w2)
  • Wetting stimulates release of zoospores. (J35.128.w1)
  • Spread by insects when wet conditions reduce the normal resistance of the skin and release zoospores (motile cocci) from pre-existing lesions. (J4.167.w2)
• Biting flies may mechanically transmit zoospores and may cause lesions with serum exudation creating conditions on the skin favourable for the survival of zoospores. (J35.128.w1)
  • See: Biting-Blood-sucking and Nuisance Flies Affecting Elephants, Bears and Lagomorphs
• Susceptibility to infection may be increased by nutritional or environmental factors. (J35.128.w1)

In Lagomorphs:

Diagnosis

• Direct smears of detached crusts or purulent material
  • Useful stains: Wright's, or a Giemsa type stain or Gram stains. (B609.2.w2)
  • Dermatophilus congolensis has a classic morphology: long parallel rows (usually two or more) of gram-positive cocci in a hypha-like array. (B609.2.w2, B614.8.w8)
• Culture. (J4.157.w7)

Treatment

• Treatment of dermatophilosis can be problematic because the bacteria are protected from topical or parenteral antibiotics by their location in the avascular epidermis under thick crusts of exudate. (B609.2.w2)
• In other species, treatment with 22,000 IU penicillin G plus 22 mg/kg streptomycin (repeated after five days if necessary), or a single dose of long-acting oxytetracycline(20 mg/kg) is commonly used. (B101)

In Bears:

Diagnosis

• The organism may be detected by one or more of the following methods: stained impression smears of moist scab material, culture of skin scrapings, examination of hair, or histopathological examination of skin biopsies.
  • Impression smears of moist scab material stained with Gram's stain or Giemsa revealed multiple rows of Gram-positive coccoid organisms forming branching filaments, typical of Dermatophilus congolensis. (J4.167.w2)
  • Histopathological findings. (J4.167.w2)
  • In Ursus maritimus - Polar bears at Knoxville Zoo, Dermatophilosis congolensis was found in hair samples, but not in skin biopsies. (P1.1977.w1)
  • In three Ursus maritimus - Polar bears, culture of Dermatophilus congolensis from skin scrapings. (P1.1981.w5)
  • Histopathological findings from biopsy, also culture.(J35.128.w1)

Treatment

• Various topical (medicated sprays or baths), and parenteral antibiotic treatments have been used, singly or in combination. Nutritional supplementation with cod liver oil was used successfully in one group of bears.
  • Long-acting Penicillin G, 10⁶ units intramuscularly by dart twice weekly for four weeks. (J35.128.w1)
    • In one bear, this was combined with triamcinolone treatment. (J35.128.w1)
  • Streptomycin, 5 g daily for five days. (J35.128.w1)
  • Long acting penicillin intramuscularly: 
    • in an adult bear, initially 30,000 units/kg (3 megaunits benzathine Penicillin G, 1.5 megaunits procaine penicillin G, 1.5 megaunits potassium penicillin G, 45,000 to 60,000 units per kg twice weekly for eight weeks. Then increased to 45,000 units/kg (9 megaunits total), twice weekly for eight weeks. (J4.167.w2)
    • In an eighteen-month-old bear, initially 60,000 units/kg (6 megaunits), followed by 30,000 units/kg (3 megaunits) on subsequent treatments, intramuscularly twice weekly for eight weeks. (J4.167.w2)
    • Initial bathing with a detergent preparation containing phemerol as a germicide. (J4.167.w2)
    • This treatment was effective with definite improvement after 3-4 weeks, and nearly normal coats after six weeks. J4.167.w2)
  • Oral doxycycline, 1 g per bear for 12 consecutive days. (J3.92.w2)
  • Oral tetracycline and chloramphenicol with topical treatment is been reported to be effective for the treatment of Dermatophilus congolensis in bears. (B336.51.w51)
  • In severe cases with greasy exudate, bathe under anaesthesia using a germicide detergent (e.g. Liquid Germicidal Detergent-- Parke-Davis),. (B16.9.w9)
  • In Ursus maritimus - Polar bears at the Knoxville Zoo, topical treatment with antibiotics was effective: initially nitrofurazone, 500 mg/gallon water sprayed onto each affected bear weekly, increasing to twice weekly, later chloramphenicol, 10 g/gallon weekly. (P1.1977.w1)
  • In three Ursus maritimus - Polar bears, temporary response occurred following treatment with antibiotics and medicated baths (e.g. oral doxycycline, 1200 mg once daily for 12 days), but lesions recurred. (P1.1981.w5)
  • In three Ursus maritimus - Polar bears, supplementation of the diet with cod liver oil (two cups per day) produced rapid resolution of lesions and pruritus, return to a normal skin and coat within three months and development of "exceptionally long and white coats resembling that of the wild polar bear". (P1.1981.w5)

• Environmental Assessment
• History & Documentation
• Physical Examination of Mammals
• Necropsy of Mammals
• Imaging in Lagomorph Diagnosis and Treatment
• Clinical Pathology of Lagomorphs
• Treatment and Care
• Environmental and Population Management
• Preventative Medicine for Mammals
• Chapter 2 - B36 Field Manual of Wildlife Diseases - Specimen Collection and Preservation
• Chapter 3 - B36 Field Manual of Wildlife Diseases - Specimen shipment
• Appendix A - B36 Field Manual of Wildlife Diseases - Sample specimen history form

• Bears (Ursidae - Bears (Family))
  • Ursus maritimus - Polar bear
• Lagomorphs
  • Oryctolagus cuniculus domesticus - Domestic European rabbit
  • Sylvilagus floridanus - Eastern Cottontail

(List does not contain all other species groups affected by this infectious agent)