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  • Author or Editor: William J. Reagan x
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Abstract

Objective—To develop a polymerase chain reaction (PCR) assay that detects and differentiates the Ohio strain of Haemobartonella felis (H felis-OH) and the California strain of H felis (H felis-CA) and to apply the assay to blood samples from cats with and without suspected haemobartonellosis (suspect and control cats, respectively).

Sample Population—220 blood samples were examined; 82 were from suspect cats, and 138 were from control cats.

Procedure—A PCR assay was designed to detect and differentiate H felis-OH and H felis-CA.

Results—On the basis of PCR assay results, the overall prevalence of H felis infection was 19.5% (43/220). Suspect cats (28.0%; 23/82) were significantly more likely than control cats (14.5%; 20/138) to be H felis infected. Significantly greater numbers of suspect cats were H felis-OH infected (12.2%, 9/82) or H felis-OH and H felis-CA infected (4.9%, 4/82) than control cats (0% [0/138] and 0.7% [1/138], respectively). Significantly more anemic cats were H felis-OH infected (14.3%; 4/28) or H felis-OH and H felis-CA infected (7.1%; 2/28) than nonanemic cats (2.3% [3/128] and 0.8% [1/128], respectively). The PCR assay was more accurate than cytologic examination for detection of H felis.

Conclusion and Clinical RelevanceHaemobartonella felis infections are more common in cats than previously recognized. Haemobartonella felis-OH is apparently more pathogenic than H felis-CA. The PCR assay is more accurate than cytologic examination for detection of H felis infection and is an effective clinical tool for the detection and differentiation of both H felis strains known to infect cats. (Am J Vet Res 2001;62:604–608)

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in American Journal of Veterinary Research

Abstract

Objective

To determine whether the cell measuring function of a laser flare-cell photometer is accurate and reproducible, using an in vitro model.

Sample Population

Leukocytes from 8 clinically normal Beagles.

Procedure

Latex beads 11.9 and 6.4 μm in diameter were used to simulate canine WBC and RBC, respectively. Beads were diluted to known concentrations, placed in a model eye, and counted by use of the laser flare-cell photometer. A range of protein diluents from 0 to 2,000 mg/dl was used to suspend beads and simulate anterior uveitis, when cells and protein would be in the aqueous humor. A similar series of experiments were repeated, using leukocytes isolated from the blood of Beagles.

Results

The laser flare-cell photometer can count 6.4-μm beads reproducibly and linearly up to a total of 510 cells/mm3, and 11.9-μm beads up to 1,300 cells/mm3 over a protein range of 0 to 2,000 mg/dl. The instrument can also count canine leukocytes reproducibly and linearly up to 1,300 cells/mm3 over that protein range.

Conclusions and Clinical Relevance

Cell and bead sizes and concentrations and protein concentrations were chosen to mimic the range observed in dogs with uveitis. Because the laser flare-cell photometer accurately counted these cells in a range of protein concentrations in the model eye, it has the potential for use in noninvasive quantitative evaluation and monitoring of uveitis in dogs. (Am J Vet Res 1998;59:1221–1226)

Free access
in American Journal of Veterinary Research

Objective—

To evaluate the efficacy and safety of intravenous administration of human immune globulin in the treatment of dogs with immune-mediated hemolytic anemia (IMHA).

Design—

Prospective clinical trial.

Animals—

10 dogs with confirmed primary IMHA that had failed to respond to conventional immunosuppressive treatment (administration of prednisone and cyclophosphamide or azathioprine).

Procedure—

Diagnosis of IMHA was confirmed by detecting spherocytosis or autoagglutination in blood smears and by excluding secondary causes of IMHA. Dogs were treated with human immune globulin (1 g/kg (0.45 glib] of body weight. IV) during a 6- to 12-hour period. Prednisone treatment was continued in all dogs, and cyclophosphamide treatment was continued in 4.

Results—

Median duration of prior immunosuppressive treatment was 12.5 days. Short-term response could not be evaluated in 2 dogs, because they were given blood transfusions within 7 days after immune globulin treatment. However, there was a significant increase in mean Hct and hemoglobin concentration in 8 other dogs from day 0 to 28 after treatment. Five dogs had clinically meaningful responses to treatment. Three dogs were alive 12 months after treatment. There were not any adverse effects that could be definitively attributed to immune globulin treatment; however, thrombocytopenia was observed in 6 dogs after treatment, and evidence of thromboembolism was detected at necropsy in 5 of the 7 dogs that died.

Clinical Implications—

Human immune globulin may be useful for Short-term stabilization of some dogs with IMHA; however, it did not appear to improve long-term survival. (J Am Vet Med Assoc 1997;210:1623–1627)

Free access
in Journal of the American Veterinary Medical Association

Abstract

Objectives—To describe clinical and laboratory findings associated with cats experimentally infected by inoculation with the 2 recognized genotypes of Hemobartonella felis (small variant, Hfsm; large variant, Hflg) and to determine the response of cats to treatment with azithromycin.

Animals—18 young adult domestic shorthair cats of both sexes.

Procedures—Cats were inoculated with H felis and monitored weekly, using CBC counts and a polymerase chain reaction (PCR) designed to detect both genetic variants of H felis. Beginning 26 days after inoculation, 11 cats were administered azithromycin (15 mg/kg of body weight, PO, q 12 h, for 7 days).

Results—Inoculation resulted in coinfection with Hflg and Hfsm, and both variants were detected by PCR. Clinical abnormalities and anemia were most severe in Hflg- and dual-infected cats. Results of PCR and CBC were positive for H felis in 112/112 (100%) and 42/112 (37.5%), respectively, samples collected after inoculation. Administration of azithromycin had little effect on clinical variables, including anemia. All cats, regardless of treatment with azithromycin, had positive results for the PCR at the end of the study period.

Conclusions and Clinical Relevance—In these cats, Hflg was more pathogenic than Hfsm, and coinfection with both variants was detected. Results of the PCR were superior to results of CBC for detecting infection with H felis. Azithromycin administered at the dose and duration reported here was not efficacious for the treatment of cats with hemobartonellosis. ( Am J Vet Res 2000;62:687–691)

Full access
in American Journal of Veterinary Research

Abstract

Objective

To evaluate interactions of human intravenous immunoglobulin (IVIG) with canine lymphocytes and monocytes.

Sample Population

Heparinized blood samples from 4 clinically normal Beagles.

Procedure

Binding ability of IVIG to canine lymphocytes and monocytes was measured by flow cytometry and an indirect immunofluorescent assay. Dualstaining fluorescent assays were done to determine lymphocyte subsets that bind IVIG. Competitive assays were done, using intact canine IgG and Fc fragments, and inhibition of binding was compared with that of F(ab)2 fragments. Ability of IVIG to inhibit phagocytosis of antibody-coated canine RBC also was determined, using a canine mononuclear cell phagocytic assay.

Results

IVIG concentrations (10, 1, 0.1, and 0.01 mg/ml) bound to (mean ± SD) 99.6 ± 0.4, 92.4 ± 6.1, 20.4 ± 24.6 and 2.0 ± 5.1% of canine lymphocytes, respectively, Dual staining analyses with IVIG and canine lymphocyte markers indicated that IVIG bound to CD4, CD8, and B lymphocytes. The aforementioned 4 IVIG concentrations bound to 98.0 ±2.1, 85.5 ± 13.5, 64.7 ± 32.8, and 26.5 ± 17.1% of monocytes, respectively. Inhibition of IVIG (0.01 mg/ml) binding to monocytes was significant (P < 0.05) in the presence of 1 and 10 mg of canine IgG/ml and 1 mg of canine Fc fragments/ml. In the presence of F(ab')2 fragments of canine IgG, inhibition was not significant, suggesting that binding is Fc mediated. Co-culturing of monocytes, opsonized RBC, and the 4 concentrations of IVIG and no IVIG resulted in 11.8 ± 5.1, 27.7 ± 12.3, 31.8 ± 15.1, 53.8 ± 6.7, and 45 ± 12% of the monocytes containing RBC, respectively. Phagocytosis inhibition was significant (P < 0.05) at an IVIG concentration of 10 mg/ml.

Conclusions

IVIG binds to canine lymphocytes and monocytes; binding to the latter is Fc mediated. IVIG also inhibits Fc-mediated phagocytosis of antibody-coated RBC.

Clinical Relevance

Owing to its ability to inhibit Fc-mediated phagocytosis of antibody-coated RBC, IVIG may be an effective short-term treatment for dogs with immune-mediated hemolytic anemia. (Am J Vet Res 1998;59:1568-1574)

Free access
in American Journal of Veterinary Research

SUMMARY

Piroxicam and other nonsteroidal anti-inflammatory drugs (nsaid) have antitumor activity against naturally acquired cancer in dogs and human beings, and against experimentally induced tumors in rodents. We are investigating potential mechanisms of nsaid antitumor activity. The direct cytotoxicity of piroxicam, indomethacin, and aspirin against 4 canine tumor cell lines (transitional cell carcinoma, squamous cell carcinoma, melanoma, and soft tissue sarcoma) was determined in short-term growth rate assays and in clonogenic assays. Piroxicam was evaluated alone and in combination with the lipoxygenase inhibitor zileuton, and in combination with the chemotherapeutic agents cisplatin and carboplatin. The 50% inhibitory concentrations (lC50) against melanoma cells in short-term growth rate assays were: 530 μM piroxicam, 180 μM indomethacin, and greater than 1 mM aspirin. These IC50 values were over 10 times greater than serum concentrations of these drugs that could safely be achieved in vivo. The IC50 of zileuton combined with piroxicam (280 μM) was not different from the IC50 of zileuton alone (230 μM; anova P = 0.47) in melanoma cells. Similarly, addition of piroxicam did not alter the IC50 of either cisplatin (1.6 μM) or carboplatin (6.1 μM). These results suggest that nsaid, at serum concentrations achievable in vivo, do not have direct cytotoxicity against canine tumor cells tested. It is unlikely that the in vivo antitumor activity of nsaid is attributable to a direct cytotoxic effect.

Free access
in American Journal of Veterinary Research