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Objective—To determine relative detection rates and detection limits for 6 published polymerase chain reaction (PCR) assays used for detection of feline herpesvirus type 1 (FHV-1) DNA.
Sample Population—5 vaccines licensed for use in preventing FHV-1–associated disease; 15 conjunctival biopsy specimens collected from cats with keratitis, conjunctivitis, or both; and a plaque-purified field isolate of FHV-1 cultured in vitro.
Procedure—Vaccines and clinical samples were assessed for FHV-1 DNA by use of all 6 assays. Detection rates were calculated by assuming that any sample in which FHV-1 DNA was detected was a true-positive result. Detection limits were estimated by use of serial dilutions of DNA extracted from cultured FHV-1 and 1 clinical sample.
Results—Testing by use of all 6 assays resulted in detection of FHV-1 DNA in all 5 vaccines. Testing by use of all 6 assays yielded concordant results for 9 of 15 conjunctival biopsy specimens (8 with negative results and 1 with a positive result). Calculated detection rates for clinical samples ranged from 29% to 86%. Assay sensitivity was ranked similarly by use of detection rate or detection limit.
Conclusions and Clinical Relevance—Testing by use of all assays was equally likely to detect vaccine virus. Therefore, a positive PCR result in a cat may reflect vaccine virus rather than wild-type virus. Test sensitivity as assessed by detection limits and detection rates varied greatly. Because FHV-1 can be shed in clinically normal animals, high detection rate will not necessarily correlate with high diagnostic sensitivity. (Am J Vet Res 2005;66:1550–1555)
Objective—To establish the in vitro efficacy of 4 novel drugs (ie, ganciclovir, cidofovir, penciclovir, and foscarnet) against feline herpesvirus type-1 (FHV-1) and compare their antiviral efficacy with that of acyclovir and idoxuridine.
Sample Population—Cultured Crandell-Reese feline kidney (CRFK) cells and FHV-1 strain 727.
Procedure—For each drug, antiviral effect was estimated by use of conventional plaque-reduction assays, and inhibitory concentration 50 (IC50; drug concentration at which plaque numbers were reduced by 50% relative to the number of plaques for nontreated control wells) was calculated. To determine whether observed antiviral effects were related to alterations in the number or viability of CRFK cells, cytotoxicity assays were performed at 1, 2, and 10 times the median IC50 for each antiviral drug.
Results—Median IC50 for each drug was as follows: ganciclovir, 5.2µM; cidofovir, 11.0µM; penciclovir, 13.9µM; foscarnet, 232.9µM; idoxuridine, 4.3µM; and acyclovir, 57.9µM. Obvious changes in morphologic characteristics, confluence, or viability of CRFK cells were not observed at concentrations up to and including 2 times the IC50 for each drug.
Conclusions and Clinical Relevance—In vitro efficacy of idoxuridine and ganciclovir against FHV-1 was approximately equivalent and about twice that of cidofovir and penciclovir. Foscarnet appeared to be comparatively ineffective. Given the reasonable clinical efficacy of idoxuridine in cats infected with FHV-1, clinical trials of ganciclovir, cidofovir, and penciclovir or their prodrug forms appear to be warranted. (Am J Vet Res 2004;65:399–403)
Objective—To determine reference values, intertest correlations, and test-retest repeatability of Schirmer tear test 1 (STT-1), phenol red thread test (PRTT), tear film breakup time (TFBUT), tear osmolarity, and meibometry in healthy cats.
Animals—135 healthy domestic cats aged 0.5 to 12.8 years.
Procedures—Each test was performed once in 120 cats and repeated in 40. Pearson correlation was used to assess correlation among tests. Intraclass correlation coefficients (ICCs) and 95% limits of agreement (LOA) were used to evaluate test-retest repeatability.
Results—Median (95% central range) values were 18 mm/min (9 to 34 mm/min) for STT-1, 29 mm/15 s (15 to 37 mm/15 s) for PRTT, 12.4 seconds (9.1 to 17.7 seconds) for TFBUT, 322 mOsm/L (297 to 364 mOsm/L) for osmolarity, and 32 meibometry units (MU; 11 to 114 MU) for peak meibometry value. The STT-1 and PRTT values were positively correlated. Age was weakly associated with TFBUT and osmolarity. Meibometry measurements were higher for strips that contacted the tear film (285 MU) than for those that touched the eyelid margin only (32 MU). All ICCs were < 0.75, and 95% LOA were wide.
Conclusions and Clinical Relevance—Tear deficiency should be suspected in cats with STT-1 < 9 mm/min, PRTT < 15 mm/15 s, or TFBUT < 9 to 10 seconds. Generally poor correlation among tests suggested that thorough tear film analysis requires performance of multiple tests in concert. Relatively poor test-retest repeatability should be considered when repeated tests are used to monitor tear film dysfunction and response to treatment.
Objective—To assess effects of disease severity, sampling instrument, and processing technique on extracted DNA yield and detection rate for feline herpesvirus-1 (FHV-1) via PCR assay.
Sample Population—Crandell-Rees feline kidney (CRFK) cells grown in vitro and conjunctival samples from 40 eyes of 20 cats.
Procedures—Samples of CRFK cells (collected by use of a swab or cytology brush, with or without suspension in PBS solution) underwent DNA extraction; DNA yield was quantified spectrophotometrically. In affected cats, signs of herpetic disease were subjectively assessed. Conjunctival swab and brush samples were collected bilaterally for measurement of DNA concentration; a defined mass (DM) of DNA and defined volume (DV) of sample were assessed for FHV-1 via PCR assays.
Results—For CRFK cells, DNA yields from unsuspended swabs and brushes were greater than for suspended swabs and brushes; suspended swab samples yielded less DNA than suspended brush samples. For conjunctival samples, DNA yields from swabs were greater than for brushes. Clinical score was not correlated with double-stranded DNA yield collected via either sampling instrument; however, cats with FHV-1–positive assay results had higher clinical scores than cats with FHV-1–negative results. Detection of FHV-1 in swab and brush samples was similar. Double-stranded DNA yield and FHV-1 detection were inversely related via DM-PCR assay. The DV-PCR assay had a significantly higher FHV-1 detection rate than the DM-PCR assay.
Conclusions and Clinical Relevance—The DV-PCR assay of DNA extracted from an unsuspended swab sample was the preferred method for assessment of conjunctival shedding of FHV-1 in cats.
Objective—To examine the effects of orally administered L-lysine on clinical signs of feline herpesvirus type 1 (FHV-1) infection and ocular shedding of FHV-1 in latently infected cats.
Animals—14 young adult, FHV-1-naive cats.
Procedure—Five months after primary conjunctival inoculation with FHV-1, cats were rehoused and assigned to receive 400 mg of L-lysine in food once daily for 30 days or food only. On day 15, all cats received methylprednisolone to induce viral reactivation. Clinical signs of infection were graded, and viral shedding was assessed by a polymerase chain reaction assay throughout our study. Peak and trough plasma amino acid concentrations were assessed on day 30.
Results—Fewer cats and eyes were affected by conjunctivitis, and onset of clinical signs of infection was delayed on average by 7 days in cats receiving L-lysine, compared with cats in the control group; however, significant differences between groups were not demonstrated. Significantly fewer viral shedding episodes were identified in the treatment group cats, compared with the control group cats, after rehousing but not following corticosteroidinduced viral reactivation. Mean plasma L-lysine concentration was significantly increased at 3 hours but not at 24 hours after L-lysine administration. Plasma arginine concentration was not significantly altered.
Conclusion and Clinical Relevance—Once daily oral administration of 400 mg of L-lysine to cats latently infected with FHV-1 was associated with reduced viral shedding following changes in housing and husbandry but not following corticosteroid administration. This dose caused a significant but short-term increase in plasma L-lysine concentration without altering plasma arginine concentration or inducing adverse clinical effects. (Am J Vet Res 2003;64:37–42)
Objective—To determine the immediately antecedent cause of secondary glaucoma and the prevalence of secondary glaucoma with anterior uveitis or lens dislocation in dogs.
Design—Retrospective case series.
Animals—156 dogs with secondary glaucoma.
Procedures—Cause of glaucoma was determined from records. Breed, age, sex, and neuter status of all dogs with secondary glaucoma were compared with the general hospital population. The prevalence of secondary glaucoma in dogs with a primary diagnosis of lens dislocation or anterior uveitis during the same period was determined.
Results—Secondary glaucoma was diagnosed in 156 of 2,257 (6.9%) dogs examined because of ophthalmic disease and was bilateral in 33 (21.2%) of those dogs. In 31 (94%) bilaterally affected dogs, the antecedent cause was the same in both eyes. Common causes of secondary glaucoma were non-surgical anterior uveitis (44.9%), anterior uveitis associated with prior phacoemulsification (15.8%), and lens dislocation (15.2%). Parson Russell Terriers, Poodles, Boston Terriers, Cocker Spaniels, Rhodesian Ridgebacks, and Australian Cattle Dogs had diagnoses of secondary glaucoma more often than expected, compared with the reference population. Age, sex, neuter status, and laterality were not associated with secondary glaucoma. The prevalence of secondary glaucoma in dogs with lens dislocation or uveitis was 15% or 17%, respectively.
Conclusions and Clinical Relevance—Glaucoma develops secondary to many intraocular diseases, particularly uveitis and lens dislocation. Diagnosis of these diseases should prompt frequent monitoring of intraocular pressure, regardless of signalment.
Objective—To determine how frequently Malassezia spp were identified on the periocular skin of dogs and assess the respective associations between the presence of Malassezia spp on the periocular skin and blepharitis, ocular discharge, and the application of ophthalmic medications.
Design—Prospective clinical study.
Animals—167 eyelids of 84 dogs.
Procedures—Samples obtained from the surface of the eyelid skin by use of adhesive tape were evaluated cytologically for the presence of Malassezia spp. Dogs were grouped on the basis of the presence of blepharitis, nature of ocular discharge, and whether ophthalmic medications were applied, and the proportion of samples with Malassezia spp was compared among the groups.
Results—Malassezia spp were detected in 19 samples, of which 15 were obtained from eyes without blepharitis and 14 were obtained from eyes treated with topical ophthalmic medications. The proportion of samples with Malassezia spp was significantly higher for eyes with ocular discharge than for eyes without ocular discharge, especially if that discharge was mucoid or mucopurulent, and for eyes that were treated with aqueous-based medications only or a combination of oil- and aqueous-based medications than for eyes that were not treated.
Conclusions and Clinical Relevance—Malassezia organisms were detected on the periocular skin of 3 of 56 (5%) clinically normal dogs. Malassezia organisms were also frequently found on the periocular skin of dogs that had mucoid or mucopurulent ocular discharge or that were administered topical aqueous-based ophthalmic medications, and the periocular skin of these dogs should be cytologically evaluated for Malassezia organisms. (J Am Vet Med Assoc 2014;244:1304–1308)
Objective—To investigate penciclovir pharmacokinetics following single and multiple oral administrations of famciclovir to cats.
Animals—8 adult cats.
Procedures—A balanced crossover design was used. Phase I consisted of a single administration (62.5 mg, PO) of famciclovir. Phase II consisted of multiple doses of famciclovir (62.5 mg, PO) given every 8 or 12 hours for 3 days. Plasma penciclovir concentrations were assayed via liquid chromatography—mass spectrometry at fixed time points after famciclovir administration.
Results—Following a single dose of famciclovir, the dose-normalized (15 mg/kg) maximum concentration (Cmax) of penciclovir (350 ± 180 ng/mL) occurred at 4.6 ± 1.8 hours and mean ± SD apparent elimination half-life was 3.1 ± 0.9 hours. However, the dose-normalized area under the plasma penciclovir concentration-time curve extrapolated to infinity (AUC0→∞) during phase I decreased with increasing dose, suggesting either nonlinear pharmacokinetics or interindividual variability among cats. Accumulation occurred following multiple doses of famciclovir administered every 8 hours as indicated by a significantly increased dose-normalized AUC, compared with AUC0→∞ from phase 1. Dose-normalized penciclovir Cmaxfollowing administration of famciclovir every 12 or 8 hours (290 ± 150 ng/mL or 780 ± 250 ng/mL, respectively) was notably less than the in vitro concentration (3,500 ng/mL) required for activity against feline herpesvirus-1.
Conclusions and Clinical Relevance—Penciclovir pharmacokinetics following oral famciclovir administration in cats appeared complex within the dosage range studied. Famciclovir dosages of 15 mg/kg administered every 8 hours to cats are unlikely to result in plasma penciclovir concentrations with activity against feline herpesvirus-1.
Objective—To detect feline herpesvirus type 1 (FHV-1) in blood of cats undergoing experimental primary herpetic disease or with spontaneous disease presumed to be caused by FHV-1 reactivation.
Animals—6 young specific-pathogen–free (SPF) cats and 34 adult cats from a shelter.
Procedures—Conjunctiva and nares of SPF cats were inoculated with FHV-1, and cats were monitored for 21 days. Periodically, blood was collected for CBC, serum biochemical analyses, and detection of FHV-1 DNA via PCR assay. For shelter cats, a conjunctival swab specimen was collected for FHV-1 PCR assay, and blood mononuclear cells were tested via virus isolation (with or without hydrocortisone) and FHV-1 PCR assay.
Results—All SPF cats developed clinical and clinicopathologic evidence of upper respiratory tract and ocular disease only. Via PCR assay, FHV-1 DNA was detected in blood of all SPF cats at least once between 2 and 15 days after inoculation. Feline herpesvirus type 1 DNA was detected in conjunctival swabs of 27 shelter cats; 25 had clinical signs of herpetic infection. However, virus was not isolated from mononuclear cell samples of any shelter cat regardless of passage number or whether hydrocortisone was present in the culture medium; FHV-1 DNA was not detected in any mononuclear cell sample collected from shelter cats.
Conclusions and Clinical Relevance—A brief period of viremia occurred in cats undergoing primary herpetic disease but not in cats undergoing presumed recrudescent herpetic disease. Viremia may be important in the pathogenesis of primary herpetic disease but seems unlikely to be associated with recrudescent disease.
Objective—To determine whether cyclooxygenase-2 (COX-2) is expressed in benign or malignant canine uveal melanocytic neoplasms and whether expression correlates with malignancy.
Sample Population—Tissue sections from 71 globes; 57 with benign (n = 15), malignant (34), or mixed (8) uveal melanocytic neoplasms; 10 with nonneoplastic disease; and 4 with no abnormalities.
Procedures—Bleached sections from all globes and canine kidney were incubated with mouse monoclonal antibody directed against rat COX-2 protein or mouse antibody isotype control. Location, intensity, and percentage of immunolabeled cells were scored.
Results—Expression of COX-2 was detected in all but 5 globes, all of which contained neoplasms. Expression of COX-2 was detected in regions infiltrated by neoplasia in 21 globes; however, definitive labeling of tumor cells was detected in only 2 of those. In the remaining 19 globes, COX-2 expression was detected in areas also labeled in globes without disease and globes with nonneoplastic disease, especially the aqueous outflow tract and ciliary body. However, only globes with uveal malignant melanomas had detectable COX-2 expression in the iris. Expression of COX-2 was detected in the ciliary body of more globes with uveal malignant melanoma (20/34) than in those without disease (1/4), with nonneoplastic disease (4/10), or with melanocytoma (3/15) or mixed neoplasms (3/8).
Conclusions and Clinical Relevance—Canine globes with uveal melanocytic neoplasia appeared to express COX-2 in similar sites and with similar intensity as globes without neoplasia. Differentiation of benign from malignant canine uveal melanocytic neoplasms was not possible.