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in Journal of the American Veterinary Medical Association

Objective

To determine the value of virus isolation (VI), immunofluorescent antibody (IFA) assay, serum neutralization (SN), and ELISA for the diagnosis of clinical feline herpesvirus-1 (FHV-1) infection in cats.

Animals

46 clinically normal cats, 17 cats with signs of acute respiratory tract disease, and 38 cats with signs of chronic ocular disease.

Procedure

Conjunctival swabs for VI, conjunctival scrapings for IFA testing, and venous blood samples for SN or ELISA testing were obtained from all cats.

Results

FHV-1 was detected in 10.9 and 28.3% of clinically normal cats and in 18.2 and 33.3% of cats with FHV-1-associated disease by VI and the IFA assay, respectively. There were no significant differences in the viral detection rate between cats with acute respiratory tract disease and cats with chronic ocular disease or between diseased cats and clinically normal cats; however, FHV-1 was never detected by both methods in clinically normal cats. Overall FHV-1 seroprevalence was 97% when tested by ELISA and 66% when tested by SN. Seroprevalence did not vary significantly among the 3 groups for either serologic test. Magnitude of SN and ELISA titers varied greatly but independently of presence or absence of clinical signs of FHV-1-associated disease. Sensitivity, specificity, and positive and negative predictive values were assessed for VI and the IFA assay—jointly and individually—and for each SN and ELISA titer magnitude. Values never all exceeded 50%.

Clinical Implications

Because FHV-1 can be detected commonly in clinically normal cats by the IFA assay or VI, neither test appears to aid in the clinical diagnosis of FHV-1 infection. Seroprevalence does not appear to vary between affected and clinically normal cats. SN, ELISA, VI, and the IFA assay appear to be of limited value in the diagnosis of FHV-1-associated disease in cats. Concurrent assessment of the IFA assay and VI results may permit exclusion of FHV-1 as an etiologic agent if results of both tests are negative. (J Am Vet Med Assoc 1999;214:502–507)

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in Journal of the American Veterinary Medical Association

SUMMARY

Intraocular production of Toxoplasma gondii-specific antibody in cats has been estimated by comparing the ratio of T gondii-specific antibody in aqueous humor and serum with the ratio of total immunoglobulins in serum and aqueous humor (Goldmann-Witmer coefficient; aqueous antibody coefficient; C value). It has been proposed that in human beings, comparison of the ratio of T gondii-specific antibody in aqueous humor and serum with the ratio of antibodies against a nonocular pathogen in serum and aqueous humor is more accurate than methods using total immunoglobulin quantification. We developed an elisa for detection of calicivirus-specific antibodies in the serum and aqueous humor of cats. By evaluating calicivirus-specific antibody concentrations in the aqueous humor of healthy and diseased cats, calicivirus was assessed as a nonintraocular pathogen. The ratio of T gondii-specific antibodies in the aqueous humor and serum and the ratio of calicivirus-specific antibodies in serum and aqueous humor were evaluated as a means of estimating intraocular T gondii-specific antibody production.

A field strain of feline calicivirus was isolated, cultured, and purified. A calicivirus-specific IgG elisa was developed for detection of feline calicivirus-specific IgG in serum and aqueous humor. Calicivirus-specific IgG was measured in the serum and aqueous humor from 3 groups of control cats. Results suggested that calicivirus is a nonintraocular pathogen in cats and that calicivirus IgG detected in aqueous humor is attributable to leakage across a damaged blood-ocular barrier.

Intraocular production of T gondii-specific antibodies was estimated, using 2 formulas. The C value was calculated by multiplying the ratio of T gondii-specific IgM or IgG in aqueous humor and serum by the ratio of total immunoglobulins (using the corresponding IgM or IgG class) in serum and aqueous humor. The C tc value (Toxoplasma-calicivirus Goldmann-Witmer coefficient) was calculated by multiplying the ratio of T gondii-specific IgM or IgG in aqueous humor and serum by the ratio of calicivirus-specific IgG in serum and aqueous humor.

Serum and aqueous humor samples were obtained from 41 client-owned cats with uveitis, and T gondii-specific C values and Ctc values were calculated. Toxoplasma gondii-specific IgM or IgG C values of 10 or greater or T gondii-specific IgM or IgG Ctc values of 1 or greater were considered to be suggestive of intraocular T gondii-specific antibody production. Of the 41 cats, 20 (48.7%) had evidence of intraocular production of T gondii-specific antibody on the basis of either an IgM or IgG C value of 10 or greater. A Ctc value could not be calculated in 3 cats because calicivirus-specific IgG was not present in aqueous humor. Of the 38 cats for which Ctc values could be calculated, 25 (65.8 %) had evidence of intraocular production of T gondii-specific antibody on the basis of either an IgM or IgG Ctc value of 1 or greater. The C values and Ctc values were in agreement for 75.9 % of IgM containing samples and 75% of IgG containing samples. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result for an IgM or IgG C value, when compared with the corresponding IgM or IgG Ctc value were determined. The results indicate that use of the C value for estimation of intraocular T gondii-specific antibody production will result in 28.6 (IgM) to 50 % (IgG) false-negative results and 12.5% (IgM and IgG) false-positive results, when compared with the Ctc value.

Free access
in American Journal of Veterinary Research
in Journal of the American Veterinary Medical Association

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.

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in Journal of the American Veterinary Medical Association

SUMMARY

Enzyme-linked immunosorbent assays for the detection of Toxoplasma gondii antigen-containing IgM immune complexes (T gondii-specific IgM-lC) and IgG immune complexes (T gondii-specific IgG-IC) in the serum of cats were developed. Serum from clinically ill, naturally infected cats; healthy, naturally infected cats; and healthy cats experimentally inoculated with T gondii was assayed. All combinations of T gondii-specific IgM, IgG, antigens, IgM-IC and IgG-IC were detected in naturally infected and experimentally infected cats. Clinically ill cats and cats with ocular signs of toxoplasmosis were more likely than healthy cats to have Tgondii-specific IC in serum. It was concluded that T gondii-specific IC form in the serum of cats, may play a role in clinical disease development, and affect the results of Tgondii-specific IgM, IgG, and antigen serologic assays.

Free access
in American Journal of Veterinary Research

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

Abstract

Objective—To determine whether administration of Crandell-Rees feline kidney (CRFK) cell lysates or vaccines against feline viral rhinotracheitis, calicivirus, and panleukopenia (FVRCP vaccines) that likely contain CRFK cell proteins induces antibodies against CRFK cell or feline renal cell (FRC) lysates in cats.

Animals—14 eight-week-old cats.

Procedure—Before and after the study, renal biopsy specimens were obtained from each cat for histologic evaluation. Each of 4 FVRCP vaccines was administered to 2 cats at weeks 0, 3, 6, and 50. Between weeks 0 and 50, another 3 pairs of cats received 11 CRFK cell lysate inoculations SC (10, 50, or 50 µg mixed with alum). Clinicopathologic evaluations and ELISAs to detect serum antibodies against CRFK cell or FRC lysates were performed at intervals.

Results—Cats had no antibodies against CRFK cell or FRC lysates initially. All cats administered CRFK cell lysate had detectable antibodies against CRFK cell or FRC lysates on multiple occasions. Of 6 cats vaccinated parenterally, 5 had detectable antibodies against CRFK cell lysate at least once, but all 6 had detectable antibodies against FRC lysate on multiple occasions. Cats administered an intranasal-intraocular vaccine did not develop detectable antibodies against either lysate. Important clinicopathologic or histologic abnormalities were not detected during the study.

Conclusions and Clinical Relevance—Parenteral administration of vaccines containing viruses likely grown on CRFK cells induced antibodies against CRFK cell and FRC lysates in cats. Hypersensitization with CRFK cell proteins did not result in renal disease in cats during the 56-week study. (Am J Vet Res 2005;66:506–511)

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in American Journal of Veterinary Research