Histology of ferret skin: preweaning to adulthood.

Ferrets are important companion animals that incur a multitude of cutaneous diseases requiring diagnostic dermatohistopathology. This study provides a description of the histology of normal ferret skin, emphasizing changes in the interval from preweaning to adulthood, an essential basis for identification of pathological situations. Skin samples obtained post-mortem from 29 topographical sites on 41 ferrets, revealed in the haired, general body surface skin an epidermis consisting of strata basale, spinosum, granulosum, and corneum and a dermis consisting of strata papillare and reticulare. Adult skin contained compound hair follicles composed of one primary hair and a collection of secondary hairs with a primary to secondary ratio of 1/5-1/15. All hairs emerged through the same follicle outlet of the skin surface. There was associated with each primary follicle, an arrector pili muscle, a multilobular sebaceous gland, and a coiled tubular sweat gland, but secondary hairs lacked these features. Compound follicles, grouped mainly as triads across the body surface, were already fully formed in the youngest group studied (3 to 6 weeks). The secondary hairs all developed from one specific region of the primary follicles and smaller ones were formed with increasing age. The differences found in specialized body regions are described. Demodex sp. mites were found in follicles and sebaceous glands in nine of 25 individuals in the perianal, vulvar, preputial, facial, and caudal abdominal skin.

Insect and arachnid hypersensitivity.

Insect hypersensitivity reactions can have a large number of clinical presentations. The majority of reactions are pruritic and involve the short- or sparsely haired areas of the body. Most are associated with eosinophilic infiltration into the skin, often in a perivascular pattern. The diagnosis may be based on compatible clinical signs and improvement with aggressive insect control and, in some cases, confirmation via provocative exposure. Intradermal, prick, or serum testing for allergen-specific IgE can be used to document the presence of reaginic antibodies against insect allergens. Treatments include avoidance, aggressive insect control, and symptomatic support; in some cases, immunotherapy may be useful in decreasing the severity of clinical reactions to insects.

Allergenic cross-reactivities in flea-reactive canine serum samples.

OBJECTIVES: To determine whether flea extract could be determined (via ELISA) to share allergenic epitopes with other insects, and to determine whether sera with different reactivities to insect extracts have different cross-reactivity patterns. SAMPLE POPULATION: 69 canine serum samples that were selected from samples submitted for routing ELISA allergy testing and had previously been found to have high reactivities to flea. PROCEDURE: Each serum sample was assessed by means of a direct ELISA for IgE binding to 11 common insects. Samples that were reactive primarily to flea extract alone were designated pool 1, samples that were reactive to small numbers of insects were designated pool 2, and samples that were reactive to all or almost all insects were designated pool 3. Samples that did not have any apparent patterns of cross-reactivity were not included in the rest of the study. Inhibition ELISA techniques were used with the 3 serum pools to determine whether multiple insect extracts inhibited reactivity on flea-coated ELISA plates. Those extracts were used to coat ELISA plates, and reciprocal inhibition studies were then performed. RESULTS: Black fly, black ant, and cockroach extracts were capable of > 50% inhibition of flea solid-phase IgE binding with all 3 serum pools. In the ELISA inhibition studies, flea extract was able to inhibit IgE binding to each extract with all pools, confirming reciprocal inhibition. CONCLUSIONS: Inhibition of IgE binding to solid-phase flea antigen by black ant, black fly, and cockroach extracts suggested sharing of allergenic epitopes among these species. Reciprocal inhibition studies further confirmed these findings. These results indicated in vitro cross-reactivity between flea, black ant, black fly, and cockroach extracts. These results need to be further investigated in vivo. CLINICAL RELEVANCE: It is possible that dogs may become sensitized to fleas via exposure to other insects, and flea allergenic dogs may have signs of pruritus, in the absence of fleas, if exposed to cross-reactive insects.

Cutaneous histamine reactivity, histamine content of commercial allergens, and potential for false-positive skin test reactions in dogs.

The cutaneous reactivity of normal and atopic dogs to intradermal injections of histamine phosphate was evaluated. Significant differences were not found in the mean wheal diameters of either group. Commercial allergens used for intradermal skin testing and immunotherapy were determined to contain histamine. To determine whether allergen histamine content was sufficient to cause false-positive skin test results, the cutaneous response of Johnson grass allergic dogs was compared, using commercial Johnson grass allergen and commercial Johnson grass allergen with histamine removed. Significant differences were not noticed between Johnson grass and dehistaminized Johnson grass. Therefore, the histamine content of commercial Johnson grass allergen did not appear to cause false-positive skin test results for this group of Johnson grass allergic dogs.

Long-term management of atopic disease in the dog.

Canine atopy is a common dermatologic disorder. Because the disease most frequently strikes young dogs, lifetime management strategies are necessary. Consideration must be given to the treatment of pruritus and secondary manifestations of the allergy, such as pyoderma, otitis externa, and seborrhea, to manage these patients successfully. The use of glucocorticoid therapy and hyposensitization are discussed.