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SUMMARY

Indirect immunofluorescent antibody (ifa), latex agglutination (la), and enzyme immunoassay (eia) methods were compared for evaluation of the serum antibody responses of dogs experimentally and naturally exposed to spotted fever-group rickettsiae. Selected sera (obtained on days 1, 42, 53, 124, 145, 236, 255, 264, and 292) were examined from three 8-month-old female Beagles inoculated with Rickettsia rickettsii on days 34 and 250 of the study. A second group of dogs comprised three 8-month-old female Beagles inoculated with R montana on days 34 and 102. Subsequently, these dogs were inoculated with R rickettsii on day 250. Serum samples were obtained from the second group of dogs on days 1, 96, 103, 132, 180, 215, 292, and 494. A third group consisted of 21 naturally exposed dogs, from which sequentially obtained serum samples were available, and which had clinical signs compatible with Rocky Mountain spotted fever. Clinical signs of disease in dogs of the third group resolved after treatment with tetracycline (22 mg/kg of body weight, po, q 8 h) was instituted. At least 2 sequentially obtained serum samples from each dog were tested. In general, the first sample was obtained just prior to treatment and the convalescent serum samples were obtained at weekly or greater intervals thereafter.

For correlation and reactivity data, an ifa test for IgG/IgM (using heavy and light chains-specific conjugate) was used as the reference standard for comparison of results with those of the other tests.

For analyzing sensitivity and specificity data in naturally exposed dogs, the assumption was made that fourfold change in the ifa IgG/IgM titer for R rickettsii or titer ≥ 1,024 identified infected dogs. Threshold titer indicative of specific rickettsial antibody was determined for each test: ifa IgG/IgM, 64; ifa IgM, 8; la, 16; EIA IgG, 64; and EIA IgM, 64. Marked cross-reactivity of sera with R rickettsii, R rhipicephali, and R montana was apparent for the ifa method using these antigens; lesser cross-reactivity was observed for R bellii. Although the ifa test for IgM, using R rickettsii as antigen, had high specificity (88.2%), it had low sensitivity (21.7%), limiting its use as a sole diagnostic test. The la test had a higher sensitivity (58.5%) than did any of the IgM ifa tests. The la test results correlated best with IgM ifa test results, and the closest agreement was obtained when R bellii was used as antigen. Because of its relatively high sensitivity (58.5%) and specificity (83.6%), the la procedure may be a valuable screening test for diagnosis of Rocky Mountain spotted fever in dogs. The IgG and IgM EIA methods had high sensitivity- 90.6 and 83.1%, respectively. The IgM EIA performed by us had low specificity; it detected infection with R montana in inoculated dogs. Comparing results of all test methods in naturally exposed dogs, the IgM EIA results were positive for the greatest number of samples with corresponding negative results by the reference IgG/IgM ifa test. This low specificity may preclude its routine use as a diagnostic test. No single serologic method correctly identified all affected dogs. On the basis of comparison with results obtained for the other serologic procedures and antigen-detection methods in 1 dog, the IgG/IgM ifa test used as a reference test may not have detected some infected dogs. Combination of a test that detects predominantly IgG, with either the la or IgM ifa test, would help to identify most infected dogs.

Free access
in American Journal of Veterinary Research

Summary

Serologic evidence of infection by Toxoplasma gondii, feline leukemia virus, feline coronaviruses, or feline immunodeficiency virus (fiv) is commonly found in cats with uveitis. Serum samples from 124 cats with uveitis were assayed by use of elisa for the detection of T gondii-specific immunoglobulin M (IgM), IgG, and circulating antigens (Ag), as well as an elisa for feline leukemia virus Ag, an elisa for antibodies to fiv, and an indirect fluorescent antibody assay for antibodies to feline coronaviruses. Serologic evidence of infection by 1 or more of the infectious agents was detected in 83.1% of the samples. Serologic evidence of T gondii infection, defined as the detection of T gondii-specific IgM, IgG, or Ag in serum, was found in 74.2% of the samples. The seroprevalence of T gondii infection was significantly greater in cats with uveitis than in healthy cats from a similar geographic area. Serum samples from cats with serologic evidence of both T gondii and fiv infections were more likely to contain T gondii-specific IgM without IgG than samples from cats with serologic evidence of T gondii infection alone. Cats with serologic evidence of fiv and T gondii coinfection had a higher T gondii-specific IgM titer geometric mean and a lower T gondii-specific IgG titer geometric mean than did cats with serologic evidence of T gondii infection alone. Serologic evaluation for T gondii infection should include assays that detect IgM, IgG, and Ag, particularly in cats coinfected with fiv.

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objective—To estimate the prevalence of perinuclear antineutrophilic cytoplasmic autoantibodies (pANCA) in the serum of healthy Soft Coated Wheaten Terriers (SCWTs) in the United Kingdom and to identify potential risk factors and heritability patterns associated with a positive result for pANCA.

Animals—188 SCWTs (age range, 18 months to 14.3 years).

Procedures—Blood samples were obtained from SCWTs in various locations in England. Serum was tested for pANCA by use of an immunofluorescence assay, and total protein and albumin concentrations were determined. Pedigrees were evaluated to identify close relatives that had protein-losing enteropathy (PLE) or protein-losing nephropathy (PLN).

Results—39 of 188 (20.7%) dogs, including young dogs, had positive results for pANCA. Dogs had significantly higher odds of having positive results for pANCA if they had at least 1 littermate that had PLE or PLN (odds ratio, 12.1) or if they had at least 1 full sibling from another litter known to be affected with PLE or PLN (odds ratio, 4.0).

Conclusions and Clinical Relevance—This study revealed a high prevalence of pANCA in the serum of a representative sample of healthy SCWTs in the United Kingdom and a significant association between positive results for pANCA and a diagnosis of PLE or PLN in a sibling.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To compare pharmacokinetics and clearances of creatinine and iohexol as estimates of glomerular filtration rate (GFR) in dogs with various degrees of renal function.

Animals—50 Great Anglo-Francais Tricolor Hounds with various degrees of renal function.

Procedures—Boluses of iohexol (40 mg/kg) and creatinine (647 mg/kg) were injected IV. Blood samples were collected before administration and 5 and 10 minutes and 1, 2, 4, 6, and 8 hours after administration. Plasma creatinine and iohexol concentrations were assayed via an enzymatic method and high-performance liquid chromatography, respectively. A noncompartmental approach was used for pharmacokinetic analysis. Pharmacokinetic variables were compared via a Bland-Altman plot and an ANOVA.

Results—Compared with results for creatinine, iohexol had a significantly higher mean ± SD plasma clearance (3.4 ± 0.8 mL/min/kg vs 3.0 ± 0.7 mL/min/kg) and a significantly lower mean volume of distribution at steady state (250 ± 37 mL/kg vs 539 ± 73 mL/kg), mean residence time (80 ± 31 minutes vs 195 ± 73 minutes), and mean elimination half-life (74 ± 20 minutes vs 173 ± 53 minutes). Despite discrepancies between clearances, especially for high values, the difference was < 0.6 mL/min/kg for 34 (68%) dogs. Three dogs with a low GFR (< 2 mL/min/kg) were classified similarly by both methods.

Conclusions and Clinical Relevance—Plasma iohexol and creatinine clearances can be used interchangeably for screening patients suspected of having chronic kidney disease (ie, low GFR), but large differences may exist for dogs with a GFR within or above the reference range.

Full access
in American Journal of Veterinary Research