Ulcerative Dermatosis of Sheep

Ulcerative dermatosis is an infectious disease of sheep caused by a virus similar to the ecthyma virus. It manifests in 2 somewhat distinct forms, one characterized by formation of ulcers around the mouth and nose or on the legs (lip and leg ulceration), and the other as a venereally transmitted ulceration of the prepuce and penis or vulva.

Contagious Ecthyma -Orf

Contagious ecthyma is an infectious dermatitis of sheep and goats that affects primarily the lips of young animals. The disease is usually more severe in goats than in sheep. Humans are occasionally affected, and the disease has been reported in dogs that have eaten infected carcasses.

Pyoderma

---

Pyoderma literally means “pus in the skin” and can be caused by infectious, inflammatory, and/or neoplastic etiologies; any condition that results in the accumulation of neutrophilic exudate can be termed a pyoderma. Most commonly, however, pyoderma refers to bacterial infections of the skin. Pyodermas are common in dogs and less common in cats.

Interdigital Furunculosis

Etiology:

The most common cause is a deep bacterial infection. Many dog breeds (eg, Shar-Pei, Labrador Retriever, English Bulldog) are predisposed to bacterial interdigital furunculosis because of the short bristly hairs located on the webbing between the toes, prominent interdigital webbing, or both. The short shafts of hairs are easily forced backward into the hair follicles during locomotion (traumatic implantation). Hair, ie, keratin, is very inflammatory in the skin, and secondary bacterial infections are common. Less commonly, foreign material is traumatically embedded in the skin. Demodicosis ( Mange in Sheep and Goats) may be a primary cause of interdigital furunculosis. Canine atopy ( Allergic Inhalant Dermatitis: Introduction) is also a common cause of recurrent interdigital furunculosis.

Exudative Epidermitis

• Lesions are caused by Staphylococcus hyicus (hyos) , which can produce an exfoliative toxin but seems unable to penetrate intact skin. Both virulent and avirulent strains exist. Abrasions on the feet and legs or lacerations on the body precede infection. Such injuries are usually caused by fighting or by abrasive surfaces such as new concrete. Other predisposing factors that may affect the severity and progress of the disease include immunity, hygiene, nutrition, and the presence of mange mites or anything that damages the skin. Mature sows that have acquired a high level of immunity from previous exposure will provide protection to piglets via their colostrum. The incidence is often higher in gilt litters and in newly established SPF herds in which the majority of breeders are gilts.

Pigs develop resistance with age, but S hyicus may be recovered from the skin of older pigs, the vagina of sows, and the preputial diverticulum of boars. These inapparent carriers serve as a source of contamination for naive herds. Suckling pigs are usually infected by their dams, in some cases during birth from sows with vaginal infections, or from contamination in the farrowing unit. Suckling piglets are the most commonly and severely affected, but cross-infection occurs after mixing at weaning with a morbidity of up to 80%. However, mortality is usually low in this age group. The incidence appears to have increased due to pig production units with high stocking densities and possibly earlier weaning.

Dermatophilosis

Etiology, Transmission, and Epidemiology:

D congolensis is a gram-positive, non-acid-fast, facultative anaerobic actinomycete. It is the only species in the genus, but a variety of strains can be present within a group of animals during an outbreak. It has 2 characteristic morphologic forms—filamentous hyphae and motile zoospores. The hyphae are characterized by branching filaments (1-5 µm in diameter) that ultimately fragment by both transverse and longitudinal septation into packets of coccoid cells. The coccoid cells mature into flagellated ovoid zoospores (0.6-1 µm in diameter). The natural habitat of D congolensis is unknown. Attempts to isolate it from soil have been unsuccessful, although it is probably a saprophyte in the soil. It has been isolated only from the integument of various animals and is restricted to the living layers of the epidermis. Asymptomatic chronically infected animals are considered the primary reservoir. Factors such as prolonged wetting by rain, high humidity, high temperature, and various ectoparasites that reduce or permeate the natural barriers of the integument influence the development, prevalence, seasonal incidence, and transmission of dermatophilosis. The organism can exist in a quiescent form within the epidermis until infection is exacerbated by climatic conditions. Epidemics usually occur during the rainy season. Moisture facilitates release of zoospores from preexisting lesions and their subsequent penetration of the epidermis and establishment of new foci of infection. High humidity also contributes indirectly to the spread of lesions by allowing increases in the number of biting insects, particularly flies and ticks, that act as mechanical vectors. Shearing, dipping, or introducing an infected animal into a herd or flock can spread infection. Dermatophilosis is contagious only in that any reduction in systemic or local skin resistance favors establishment of infection and subsequent disease.

Urticaria

---

Urticaria, horse Urticaria is characterized by multiple plaque-like eruptions that are formed by localized edema in the dermis and that often develop and disappear suddenly. It occurs in all domestic animals but most often in horses (see also sweet itch, Biting Midges). Allergic urticaria may be exogenous or endogenous. Exogenous hives may be produced by toxic irritating products of the stinging nettle, the stings or bites of insects, medications, or chemicals (eg, carbolic acid, turpentine, carbon disulfide, or crude oil). Nonimmunologic factors such as pressure, sunlight, heat, exercise, psychologic stress, and genetic abnormalities may precipitate or intensify urticaria. Pruritus is not always present.

Sensitive animals, particularly shorthaired dogs and purebred horses, also may exhibit dermographism, a phenomenon wherein rubbing or whipping produces urticaria-like skin lesions. It is of no clinical significance.

Endogenous or “symptomatic” urticaria may develop after inhalation or absorption of ingested allergens; it has been seen mostly in horses and dogs. In horses, it has been noted in the course of GI conditions, particularly severe constipation or inflammation of the intestinal mucosa. A unique form of urticaria has been described chiefly in the Channel Island breeds of cattle (Jersey, Guernsey), which become sensitized to the casein in their own milk (see also Localized Anaphylactic Reactions); it occurs in cases of milk retention or unusual engorgement of the udder with milk. Urticaria has been seen in bitches during estrus. In young horses, dogs, and pigs, urticaria may be associated with intestinal parasites. Angioneurotic edema is a life-threatening variant of urticaria in which there is diffuse subcutaneous edema, often localized to the head, limbs, or perineum. In horses, dermatophytosis (ringworm) and pemphigus foliaceus may present as urticaria early in the disease.