Graduate Thesis Or Dissertation
 

The pathogenesis, diagnosis and treatment of canine allergic and bacterial dermatitis

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/z316q414w

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  • The pathogenesis, diagnosis and treatment of bacterial dermatitis and various canine allergic dermatitidies including allergic inhalant dermatitis, contact dermatitis and flea allergy dermatitis were studied. The effect of specific nonprotein and protein components of commercial flea antigens on the gross and microscopic appearance of intradermal injections was investigated. Additionally, a preliminary evaluation of lymphocyte stimulation by mitogens and flea antigen was performed on a limited number of blood samples. The predominant bacteria isolated from primary or secondary bacterial dermatitis is Staphylococcus auerus (coagulase positive). The history and lesions associated with bacterial dermatitis are quite variable, depending upon the presence of concurrent problems and the nature of the infection such as superficial or deep. Histopathological changes are not pathognomonic for bacterial dermatitis, but are generally characteristic. Diagnosis is confirmed by bacterial isolation from lesions. Treatment includes long term bactericidal antibiotic therapy based upon in vitro antibiotic sensitivity testing, autogenous bacterins and treatment of concurrent problems. Allergic inhalant dermatitis is characterized by intermittent or continuous pruritus accompanied by primary or secondary lesions in a young dog, usually one to three years of age. There tends to be a familial history of allergic dermatitis. The distribution of lesions is usually more generalized than other allergic etiologies. Diagnosis is based on history and intradermal skin tests. The predominant allergens identified with intradermal skin testing in the Pacific Northwest include molds, weeds, trees, grass and house dust. In 80 percent good or fair response to treatment by hyposensitization and in some cases minimal maintenance dosages of corticosteroids is expected. Approximately 20 percent of the cases require higher levels of corticosteroids to control allergic symptoms with or without concurrent hyposensitization. Canine contact dermatitis is characterized by a predominantly ventral dermatitis accompanied by pruritus. Approximately 50 percent of the dogs manifest contact allergies by one year of age, while 25 percent are four years or older. Usually both primary and secondary lesions are present. Diagnosis is based on history, clinical appearance, isolation from suspected contactant and then provacative exposure to the same contactant. Histopathologic characteristics of allergic contact dermatitis are not specific, but can be helpful in broadly categorizing dermatoses providing direction from further study and treatment. Treatment includes avoidance of contact exposure or corticosteroid administration. A high incidence of flea allergy dermatitis is commonly found in dogs with a low grade 'flea infestation. Clinical signs include intense pruritus involving the posterior of the body, especially the dorsal back and abdomen. Both primary and secondary lesions are often present. Diagnosis is usually based on history, distribution of lesions and response to treatment. Intradermal skin tests using flea antigen may help in confirming the presence of a flea hypersensitivity, but are not adequate for making a definitive diagnosis in many cases. The wheal induced by the flea antigen is mainly due to edema without a remarkable inflammatory response. There is no correlation between gross wheal formation and microscopic changes, particularly in the degree of upper dermal edema. Treatment includes control of fleas in the environment by fumigation, continuous flea control on all of the animals in the household and hyposensitization with flea antigen. The uptake of tritiated thymidine by lymphocytes stimulated with phytohemmaglutinin, concanavalin A, lipopolysaccharides and diluted flea antigen was evaluated on a limited number of blood samples. A wide variation between replicate samples precluded establishment of definite conclusions.
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