Atypical Dermatophilus Congolensis Infection in a Three-Year-Old Pony

Abstract

Abstract. Dermatophilosis caused by Dermatophilus congolensis causes exudative dermatitis in a variety of species. The infection is generally limited to the cutaneous tissues, where infection is acquired from the environment and bacteria penetrate into keratinized epithelium through epithelial disruption. A 3-year-old pony filly was examined for enlarging mandibular lymph nodes during the preceding 10 months. Biopsy of the node revealed mixed and granulomatous inflammation and thick, filamentous Gram-positive bacteria. Dermatophilus congolensis, confirmed by biochemical testing and sequencing of the ribosomal RNA gene, was cultured from a sample aspirated from the infected site. Dermatophilus congolensis should be considered as a possible etiologic agent associated with lymphadenopathy and granulomatous inflammation in the horse.Key words: Dermatophilosis; Dermatophilus congolensis; horses; lymphadenopathy.Dermatophilus congolensis is a Gram-positive coccobacillary actinomycete that causes an exudative dermatitis in a variety of species, most notably in ruminants and horses, although rare infections occur in cats, dogs, and humans.1,2,12 Infection is generally restricted to the skin and subcutaneous tissue, although uncommon involvement of lymphoid tissue in ruminants and cats has been described. 3,4,12A 3-year-old female palomino pony was referred to the William R. Pritchard Veterinary Teaching Hospital at the University of California, Davis (Davis, CA) with the primary complaint of progressively enlarging bilateral mandibular lymphadenopathy during the previous 10 months. Intermandibular swelling was noticed the winter of the previous year (10 months before referral), and a biopsy of the affected area revealed inflamed lymphoid tissue. Prior to referral, the first premolar teeth had erupted and were removed; significant hooks on cheek teeth were treated with dental floatation. The pony was also reported by the owner to be lethargic and appeared pruritic, as evidenced by biting at or rubbing her sides. The filly had been regularly vaccinated and had most recently been dewormed with pyrantel pamoate 3 weeks prior to referral.The filly was slightly depressed on examination. Her temperature and heart rate were within normal limits. A slightly elevated respiratory rate of 25 breaths per minute was detected, although there were no abnormal lung sounds on thoracic auscultation. Large, firm, nonpainful multilobulated masses in the intermandibular space were palpable. The only other abnormalities on physical examination were small areas of superficial cutaneous excoriations over the flanks, thorax, and gluteal musculature. Dark, loose fecal material was observed after normal defecation.A complete blood count was unremarkable, and plasma fibrinogen was 300 mg/dl. A serum biochemistry panel was within normal limits, with the exceptions of slightly elevated alkaline phosphatase ( A lymph node aspirate and biopsy were performed on the affected tissue; a small amount of inspissated pus was observed during the biopsy procedu...

Transmission of pathogens byStomoxysflies (Diptera, Muscidae): a review

“…Dermatophilus congolensis is a Gram-positive coccobacillary actinomycete that causes an exsudative dermatitis in a variety of species, most notably in ruminants and horses, although rare infections occur in cats, dogs, and humans [1, 15]. It has a worldwide distribution but is more prevalent in the humid tropics and subtropics [133].…”

Dermatophilus congolensis in a feral cat

“…4 The infection is usually limited to the cutaneous tissues, including the hair follicles, but rare reports describe affected lymphoid tissue. 1…”

“…4 The infection is usually limited to the cutaneous tissues, including the hair follicles, but rare reports describe affected lymphoid tissue. 1 D congolensis has been rarely reported in cats. 5,6 In cats, the subcutaneous tissues, muscle and lymph nodes are more commonly affected.…”

“…D congolensis is a Gram-positive coccobacillary actinomycyte and normal dermal organism in commonly affected species such as cattle, horses and sheep. 1 In susceptible species, the organism is opportunistic and disease results after chronic trauma or moisture allowing for bacterial overgrowth. 2,3 In these species the lesion is an exudative skin disease involving the epidermis and is often referred to as 'rain scald' in horses and 'fleece rot' in sheep.…”

Dermatophilus congolensis associated bronchopneumonia in an alpaca

“…In temperate countries, sheep and goats are commonly affected and a sporadic proliferative pyogranulomatous pododermatitis has been seen in alpacas in Australia (Horadagoda unpublished data). Apart from skin infections, in rare instances, the organism can cause pyogranulomatous infections in the lymph nodes (Byrne, Rand, McElliott, Samitz, & Brault, ). To the author's knowledge, this is the first report of D. congolensis associated with a case of bronchopneumonia in an animal.…”