Reactivity to intradermal injections of extracts of house dust and housedust mite in healthy dogs and dogs suspected of being atopic.

Fifty dogs underwent intradermal allergy testing with housedust mite and house dust extracts, using concentrations recommended by the manufacturer. Twelve dogs (group I) were healthy dogs obtained from a pound; 12 dogs (group II) were healthy, privately owned dogs; 15 dogs (group III) were suspected of being atopic and had had multiple positive reactions to intradermal injections of allergens of specific trees, weeds, grasses, or molds; and 11 dogs (group IV) were suspected of being atopic, but only had had positive reactions to intradermal injections of housedust mite, house dust, and flea antigen extracts. Use of the concentrations of housedust mite and house dust extracts currently recommended for intradermal allergy testing resulted in false-positive reactions in 14 of 24 (58%) and 12 of 24 (50%) healthy dogs tested, respectively. Differences in number of dogs with positive reactions or grade of reaction to housedust mite or house dust allergens were not detected between groups of healthy dogs (groups I vs II), between groups of suspected atopic dogs (groups III vs IV), or between healthy dogs and dogs suspected of being atopic (groups I and II vs III and IV). Therefore, clinical importance of positive results of intradermal allergy testing of house dust or housedust mite allergens was equivocal for dogs suspected of being atopic. Threshold concentrations for intradermal allergy testing were determined in 24 healthy dogs (group I and II) by intradermal administration of 5 dilutions each of housedust mite extract and house dust extract.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of computed tomography with radiography as a noninvasive diagnostic technique for chronic nasal disease in dogs.

Computed tomography was evaluated as a noninvasive technique for the diagnosis of chronic nasal disease in dogs. Computed tomographic images, radiographs, and histopathologic findings were compared in 11 dogs with chronic nasal disease. Definitive diagnosis was made following traumatic nasal flush, exploratory surgery, or necropsy. The study included 8 dogs with intranasal tumors, 2 dogs with bacterial rhinitis (Pasteurella sp), and 1 dog with mycotic rhinitis (Aspergillus sp). Computed tomography was superior to radiography in defining the extent of the disease process and in differentiating infectious rhinitis from nasal neoplasms. It defined lesions in the palate, nasopharyngeal meatus, maxillary sinus, caudal ethmoturbinates, and periorbital tissues that were difficult to demonstrate by use of conventional radiography. Tumors appeared as space-occupying lesions that obliterated the turbinates, caused deviation of the nasal septum, and eroded bone. Rhinitis appeared as a cavitating lesion that spared the paranasal sinuses, thickened and distorted the turbinates, and widened the meatus. Although morphologically distinct on computed tomographic images, infectious rhinitis and nasal neoplasms could not be differentiated by attenuation measurements or degree of contrast enhancement. Computed tomography appeared to be a reliable, noninvasive technique for the diagnosis of chronic nasal disease in dogs, and a promising alternative to diagnostic techniques currently in use.

Comparison of intradermal allergy test and enzyme-linked immunosorbent assay in dogs with allergic skin disease.

Results of an ELISA for allergen-specific IgE were compared with results of an intradermal (ID) allergy test in 5 clinically normal dogs and 36 dogs referred for evaluation of allergic dermatitis. The ELISA had a sensitivity of 100% and a specificity of 0%. Agreement between ID allergy test and ELISA for positive and negative results ranged from 44 to 56% for pollens, 39% for house dust/dust mite, 22% for fungi, and 54% for fleas. Agreement between ID allergy test and ELISA scores for all pollens was only 10% greater than that expected by chance alone, and a kappa value of 0.17 confirmed poor test agreement. The greatest disparity in results was seen in dogs with negative ID and positive ELISA results. Median ELISA absorbance values for 15 groups of related allergens were compared in 4 groups of dogs: clinically normal dogs, atopic dogs with positive ID reactivity, suspected atopic dogs with negative ID reactivity, and flea-allergic dogs. There was no significant difference in median ELISA values between clinically normal dogs and flea-allergic dogs, or clinically normal dogs and atopic dogs for any allergen group. Although the ELISA absorbance value for fungal antigens was significantly higher in dogs suspected of being atopic than in clinically normal dogs, there was no significant difference in median ELISA values for any other allergen group. These findings suggested the disparity between ID allergy test and ELISA results was primarily attributable to false-positive ELISA reactions rather than greater ELISA sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of glomerular lesions in dogs with acute experimentally induced Ehrlichia canis infection.

Six male Beagles were inoculated with Ehrlichia canis. Transient proteinuria was confirmed during the acute phase of infection by serial determination of urinary protein-to-creatinine ratio. Peak urine protein loss, consisting principally of albumin, was observed 2.5 to 3.5 weeks after inoculation. Renal biopsy specimens were obtained before inoculation, during peak proteinuria, and 10 weeks after inoculation when proteinuria had resolved. Renal tissue was evaluated by use of light, immunofluorescent, and electron microscopy to correlate specific glomerular lesions with development of proteinuria. Histologic examination revealed perivenular and interstitial infiltrates of lymphocytes and plasma cells localized principally to the renal cortex. Glomerular lesions were minimal to absent. Immunofluorescent staining revealed moderate to marked deposition of anti-canine IgG and IgM in the glomerular tufts and mesangium. Depositions of anti-canine complement factor C3 were not observed. Immunofluorescent staining persisted 10 weeks after inoculation, despite resolution of proteinuria, and probably represented passive trapping of immunoglobulins. Ultrastructural examination revealed fusion of podocyte processes that coincided with development of proteinuria. Electron-dense deposits or changes in the basement membrane were not observed. Morphometric measurements of average podocyte process length and percentage of coverage of basement membrane by podocyte processes were used to quantify the degree of process fusion. Both measurements increased significantly (P < 0.05) during peak proteinuria, and returned to preinoculation values when proteinuria had resolved 10 weeks after E canis inoculation. These findings indicated possible minimal-change glomerulopathy, rather than immune-complex glomerulonephritis, during acute E canis infection and could explain transient proteinuria without histologic evidence of glomerular disease.

Effect of tiletamine/zolazepam sedation on intradermal allergy testing in atopic dogs.

Seven atopic dogs underwent intradermal allergy testing with 46 inhalant antigens before and after administration of a tiletamine/zolazepam solution (4 mg/kg of body weight, IV). This anesthetic protocol had no significant effect on the intradermal response caused by histamine, whole flea extract, or various inhalant allergens. Short-acting chemical restraint induced by the drug combination facilitated the intradermal testing procedure.

Investigation of renal protein loss in dogs with acute experimentally induced Ehrlichia canis infection.

Urinary protein-to-creatinine ratios and serum albumin concentrations were measured in 8 adult male dogs experimentally inoculated with Ehrlichia canis. Urinary protein concentration increased significantly, but transiently, during the acute phase of infection. Urinary protein-to-creatinine ratios were highest (mean, 8.6) during the third and fourth weeks after infection, and decreased to less than 0.5 by 6 weeks after infection. Correspondingly, albumin concentration decreased significantly during the acute phase. Serum albumin concentrations were lowest (mean, 2.1 g/dl) the fourth week after infection and increased to greater than 3.0 g/dl by 11 weeks after infection. There was an inverse linear correlation between urinary protein-to-creatinine ratio and serum albumin concentration. The magnitude of proteinuria and its inverse relationship with serum albumin concentration suggested that hypoalbuminemia associated with acute E canis infection may be attributable primarily to increased renal loss of protein, rather than decreased hepatic synthesis as previously suggested. Another dog was subsequently inoculated with E canis from 1 of the experimentally infected dogs and a renal biopsy was performed during peak proteinuria (urinary protein-to-creatinine ratio = 22 and serum albumin = 1.1 g/dl). Immunofluorescent staining revealed mild to moderate deposits of anti-canine IgM, and to a lesser extent, anti-canine IgG and complement factor C3 in the glomerular tufts and mesangium. Ultrastructural evaluation revealed distortion and fusion of podocyte foot processes and increased microvilli on podocytes. These morphologic changes were consistent with transient glomerular leakage of protein of a magnitude that would significantly contribute to hypoalbuminemia during acute E canis infection. An underlying immunologic mechanism was suggested by positive glomerular immunofluorescence and previously described histologic findings.

Characterization of the subclinical phase of ehrlichiosis in dogs.

Prevalence of subclinical Ehrlichia canis infection in a Mississippi kennel was 53%. Most of the dogs probably had been infected for 4 or 5 years. The subclinical phase of the infection was characterized by high antibody titers to E canis (9 of 10 dogs with titers of 1:5, 120), hyperglobulinemia (9 of 10 dogs), thrombocytopenia (5 of 10), absolute lymphocytosis (4 of 10), and absolute neutropenia (3 of 10). The dogs had normal PCV, serum albumin concentrations, and urine protein excretion. Findings indicated that a high percentage of dogs in an enzootic area may develop subclinical ehrlichiosis that may last several years. Despite persistent antigenic stimulation, dogs subclinically infected for a prolonged time did not develop clinically apparent glomerular disease. However, evaluating dogs for antibody titers against E canis is recommended in endemic areas because subclinically infected dogs eventually may develop severe chronic disease, which may be less responsive to therapy.

Atypical findings in 16 cases of canine ehrlichiosis.

Sixteen cases of clinically and serologically diagnosed canine ehrlichiosis were studied retrospectively. Findings not previously reported included diffuse, pulmonary interstitial radiopacities; weak-positive results for blastomycosis, using agar gel immunodiffusion; normal platelet counts; hemorrhage despite platelet counts greater than 100,000/mm3, and positive results for platelet factor 3 and antinuclear antibody assays. These atypical findings showed that the differential diagnosis of canine ehrlichiosis, blastomycosis, immune-mediated thrombocytopenia, and primary nasal lesions may be confusing, warranting careful assessment. The increased release of platelet factor 3 and the finding of antinuclear antibodies supported an immune mechanism in the pathogenesis of canine ehrlichiosis, as suggested by previous experimental studies.