Evaluation of serologic and viral detection methods for diagnosing feline herpesvirus-1 infection in cats with acute respiratory tract or chronic ocular disease

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.     

Isolation of Feline Herpesvirus 1 from the Trigeminal Ganglia of Acutely and Chronically Infected Cats

Feline herpesvirus 1 (FHV-1) is one of the most common viral infections of domestic cats worldwide, estimated to cause 50% of all respiratory infections in this species. Feline herpesvirus 1 is also an important ocular pathogen of cats, causing conjunctivitis, epithelial and stromal keratitis, symblepharon formation, keratocon-junctivitis sicca, and corneal sequestration. Despite the importance of this viral disease, major questions remain unanswered concerning the pathogenesis of its most important manifestation, the recrudescent infection. Although the taxonomic classification of FHV-1 as an alpha herpesvirus implies the ability of FHV-1 to establish neural latency, attempts at recovering the virus from the trigeminal ganglia of latently infected cats have typically yielded negative results. This failure has stimulated speculation that neural tissue is not an important site for latent FHV-1. However, in the most successful of such studies, FHV-1 was isolated from the trigeminal ganglia of 3 of 17 cats using an explant technique. In the present study, we describe the successful isolation of FHV-1 from the trigeminal ganglia of cats using a similar tissue culture method.     

Feline Herpesvirus 1 and Mycoplasma spp. Conventional PCR Assay Results From Conjunctival Samples From Cats in Shelters With Suspected Acute Ocular Infections

Signs of ocular infections like discharge and conjunctivitis occur commonly in cats in shelters and feline herpesvirus 1 (FHV-1), Chlamydia felis, Mycoplasma spp, and feline calicivirus (FCV) are thought to be the most common causes. While molecular assays are available to amplify nucleic acids of each of these agents as single tests or in panels, additional information is needed concerning whether the assay results can be used to predict response to treatment. The objectives of this study were to report results for conventional polymerase chain reaction (PCR) assays that amplify nucleic acids of FHV-1, Mycoplasma spp., C. felis, and FCV from cats with signs of acute ocular and upper respiratory infections in an animal shelter and to determine whether the results are associated with treatment responses to topical administration of cidofovir (anti-FHV-1) or oxytetracycline (anti-Mycoplasma spp. and C. felis). Conjunctival samples were collected from both eyes of 60 cats with ocular signs of disease. Total deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) were extracted from each sample and assayed for DNA of FHV-1, Mycoplasma spp., and C. felis and RNA of FCV by conventional PCR assays. Cats were randomized to be administered either oxytetracycline ointment or cidofovir drops in both eyes and a standardized ocular disease score system was used to determine a total ocular score for each cat prior to treatment on Day 0 and on Day 7. Nucleic acids of one or more agents were amplified from one or both eyes from 39 of 60 cats (65%). FHV-1 DNA (21 cats), Mycoplasma spp. DNA (25 cats) or FCV RNA (2 cats) were amplified most commonly. After treatment for 7 days, 32 of 60 cats (53.3%) were considered improved with 27 of 32 cats (84.4%) having ocular scores of 0 (21 cats) or 1 (6 cats). When the results of the FHV-1 PCR assay were compared to cidofovir treatment responses, the positive and negative predictive values of the assay were shown to be 29.4% and 60%, respectively. When the results of the Mycoplasma spp. PCR assay were compared to oxytetracycline treatment responses, the positive and negative predictive values of the assay were shown to be 40% and 38.5%, respectively. The predictive value of conventional PCR assay results for FHV-1 or Mycoplasma spp. DNA was low, suggesting that performing these tests to formulate a treatment protocol has minimal clinical utility in cats with suspected acute ocular infections.     

Evaluation of different sampling methods and results of real-time PCR for detection of feline herpes virus-1, Chlamydophila felis and Mycoplasma felis in cats

Objective To investigate how different sampling techniques affect detection of DNA from feline herpes virus Type 1 (FHV-1), Chlamydophila felis and Mycoplasma felis and to study the correlation between positive test results and clinical signs in cats. Animals Fifty-one cats; 24 with ocular signs and 27 healthy control cats. Procedures Samples were collected from all cats using cotton swabs, conjunctival and corneal biopsies, and corneal scrapings. Samples were analyzed for presence of FHV-1, C. felis, M. felis, and feline DNA, defined by 28S rDNA, by using real-time PCR. Results In affected cats, FHV-1 was detected in only one cat; C. felis and M. felis were not detected in any affected cats. None of the three organisms was detected in any control cats. Feline DNA was demonstrated in all conjunctival samples, in 82% of corneal swabs, 92% of corneal scrapings, and 100% of keratectomy samples. Conclusions Because of the generally low detection rate for FHV-1, C. felis, and M. felis DNA in this study, differences regarding sampling technique could not be determined and correlation between positive test results and degree of clinical signs could not be made. Detection of feline DNA in most samples irrespective of sampling technique, suggests a low prevalence of FHV-1, C. felis and M. felis in this population of cats.     

Assessment of infectious organisms associated with chronic rhinosinusitis in cats

OBJECTIVE: To determine detection rates for feline herpesvirus type 1 (FHV-1), Mycoplasma spp, fungi, and bacteria in flush samples and biopsy specimens from the nasal cavities of cats with and without chronic rhinosinusitis (CRS). DESIGN: Prospective study. ANIMALS: 10 CRS-affected cats and 7 cats without signs of respiratory tract disease. PROCEDURES: Nasal flush samples and biopsy specimens were collected from all cats for bacterial (aerobic and anaerobic), fungal, and mycoplasmal cultures; additional biopsy specimens were collected for virus isolation and polymerase chain reaction (PCR) assay (to detect FHV-1 DNA). RESULTS: Aerobic bacteria were detected in flush samples from 5 of 7 control cats; culture of flush samples from CRS-affected cats yielded aerobic bacteria (9/10 cats), anaerobic bacteria (3/10), and Mycoplasma spp (2/10). No fungal organisms were isolated from any cat. Potential pathogens were isolated significantly more often from CRS-affected cats than from control cats. Bacterial culture of biopsy specimens yielded aerobic bacteria (2/7 control cats and 4/10 CRS-affected cats) and anaerobic bacteria (2/10 CRS-affected cats). Although FHV-1 was not detected in nasal biopsy specimens from control or CRS-affected cats, FHV-1 DNA was detected via PCR assay in specimens from 4 of 7 control cats and 3 of 10 CRS-affected cats. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with findings in control cats, anaerobic bacteria, Mycoplasma spp, and a variety of potentially pathogenic organisms were detected more commonly in samples from cats with CRS. In both groups, FHV-1 was detected via PCR assay as a nonviable organism or in noncultivable amounts.     

Cytologic findings, and feline herpesvirus DNA and Chlamydophila felis antigen detection rates in normal cats and cats with conjunctival and corneal lesions

Samples were collected from 36 cats with feline herpesvirus (FHV-1)-related ocular disease (conjunctivitis, epithelial or stromal keratitis, or corneal sequestration), and 17 cats without ocular changes. Corneoconjunctival swabs, scrapings and biopsies were tested in various combinations for presence of FHV-1 DNA using single round (sr) polymerase chain reaction (PCR) and nested PCR (nPCR). Additional swabs from the inferior conjunctival fornix were tested by enzyme-linked immunosorbent assay for Chlamydophila felis antigen. Cytologic evaluation was carried out on conjunctival (cats with conjunctivitis) and corneal (cats with keratitis) cytobrush preparations. FHV-1 DNA was detected by PCR in 14 (39%) cats with ocular disease and 1 (6%) of the control group. Agreement between srPCR and nPCR results was significant (P < 0.01). FHV-1 DNA was detected in 3/7 cats with conjunctivitis, 5/6 cats with epithelial keratitis, 3/11 cats with stromal keratitis, and 3/12 cats with corneal sequestration. There was a significant association (P = 0.0027) between viral presence and epithelial keratitis. However, no significant association was found between viral presence and conjunctivitis (P = 0.059), stromal keratitis (P = 0.15), or corneal sequestration (P = 0.18). With respect to FHV-1 DNA detection, intersample agreement was significant (P < 0.03). No sampling technique seemed more likely than another to harvest detectable viral DNA, except for cats with corneal sequestrum in which viral DNA was not detected using corneoconjunctival swabs. FHV-1 DNA was detected in 6/9 samples with intranuclear inclusion bodies and in 6/7 cats with eosinophils on cytologic examination. All samples tested negative for C. felis antigen.     

Pretreatment with feline interferon omega and the course of subsequent infection with feline herpesvirus in cats

OBJECTIVE: Recombinant feline interferon omega (rFeIFN-omega), a type I IFN, may have the potential to limit virus replication and associated clinical signs when administered early on in the course of feline herpesvirus type 1 (FHV-1) infection and reactivation, respectively. The effect of rFeIFN-omega pretreatment on the course of subsequent FHV-1 infection in cats was investigated. ANIMALS STUDIED: Nine SPF cats were divided into an IFN group (n = 5) and a control-group (n = 4). PROCEDURES: The IFN group was pretreated for 2 days with 10 000 units rFeIFN-omega twice a day topically into both eyes and 20 000 units rFeIFN-omega once a day orally, whereas the control group was mock-treated. Subsequently all cats were infected with FHV-1. Samples for FHV-1 DNA detection and quantitation, virus isolation, and titration of FHV-1 antibodies were collected. Clinical and ocular signs were recorded and scored. RESULTS: Courses of median individual clinical and ocular scores and virus load did not differ significantly between both groups using anova for repeated measurements. Analysis (anova) of each individual ocular parameter revealed significantly high scores for epithelial keratitis (P = 0.016) in the IFN group compared to the control group. Periods of virus shedding did not differ significantly between both groups using the Wilcoxon rank sum test. CONCLUSIONS: Results indicated a lack of beneficial effects of rFeIFN-omega pretreatment in the course of primary FHV-1 infection in cats.     

Clinical and antiviral effect of a single oral dose of famciclovir administered to cats at intake to a shelter

Although famciclovir is efficacious in feline herpesvirus type 1 (FHV-1)-infected cats, effects of a single dose early in disease course have not been reported. In this two part, randomized, masked, placebo controlled study, cats received a single dose of 125 mg famciclovir (n = 43) or placebo (n = 43; pilot study), or 500 mg famciclovir (n = 41) or placebo (n = 40; clinical trial) on entering a shelter. FHV-1 PCR testing was performed, bodyweight and food intake were recorded, and signs of respiratory disease were scored prior to and 7 days following treatment. FHV-1 DNA was detected in 40% of cats in both parts at study entry. In the pilot study, ocular and nasal discharge scores increased from days 1 to 7 in famciclovir and placebo treated cats. Sneezing scores increased and bodyweight decreased in famciclovir-treated cats. The proportion of cats in which FHV-1 DNA was detected increased over time in all cats in the pilot study. In the clinical trial, food intake and median clinical disease scores for nasal discharge and sneezing increased from days 1 to 7 in both groups and demeanor scores worsened in famciclovir-treated cats. The proportion of cats shedding FHV-1 DNA was greater on day 7 than on day 1 in cats receiving 500 mg famciclovir. A single dose of famciclovir (125 or 500 mg) administered at shelter intake was not efficacious in a feline population in which 40% were already shedding FHV-1.     

Detection of virulent feline herpesvirus-1 in the corneas of clinically normal cats

To evaluate the clinically normal feline cornea for the presence of virulent feline herpesvirus-1 (FHV-1), corneas from 31 cats (25 with normal eyes and six with active disease or corneal scarring) euthanased at a shelter were collected. Corneas from two specific pathogen-free cats were included as negative controls. Virus isolation (VI), fluorescent antibody (FA) staining and real-time polymerase chain reaction (rt-PCR) were performed on all samples. The presence or absence of dexamethasone in the media was evaluated for its effect on VI. VI was positive for FHV-1 in six corneas from five cats, all with clinically normal eyes. One cornea was positive for feline calicivirus (FCV) in addition to FHV-1, but only in media that included dexamethasone. Eight corneas were positive on rt-PCR for FHV-1, all from cats with clinically normal eyes. All positive VI samples were confirmed with FA staining. VI and rt-PCR were negative for FHV-1 and FCV in cats with active disease or corneal scarring. Data from this study indicate that virulent FHV-1 and FCV can be present in feline corneas that are clinically normal. Dexamethasone may enhance viral spread through a cell receptor mechanism.     

Efficacy of oral supplementation with L-lysine in cats latently infected with feline herpesvirus

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 corticosteroid-induced 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. CONCLUSIONS 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.     

Detection of feline herpesvirus-specific antibodies and DNA in aqueous humor from cats with or without uveitis.

OBJECTIVE: To determine whether uveitis in cats was associated with intraocular production of feline herpesvirus type 1 (FHV-1)-specific antibodies or with detection of FHV-1 DNA in aqueous humor (AH). ANIMALS: 44 cats with idiopathic uveitis, 29 cats with uveitis attributed to Toxoplasma gondii infection, 13 FHV-1 seropositive cats without uveitis, and 9 FHV-1 seronegative cats without uveitis. PROCEDURE: ELISA were used to detect FHV-1-specific antibodies and total IgG antibodies in serum and AH, and the Goldmann-Witmer coefficient (C-value) for intraocular antibody production was calculated. A polymerase chain reaction assay was used to detect FHV-1 DNA in AH. RESULTS: FHV-1 seroprevalence among cats with uveitis was not significantly different from seroprevalence among cats without uveitis. Intraocular FHV-1 antibodies were never detected in cats without uveitis. Significantly more cats with idiopathic uveitis (22/44) or with toxoplasmic uveitis (11/29) had evidence of intraocular antibody production (C-value > 1) than did cats without uveitis. Only cats with idiopathic uveitis had FHV-1 C-values > 8. Among cats with evidence of intraocular antibody production, cats with idiopathic uveitis had a significantly higher median FHV-1 C-value (9.61) than did cats with toxoplasmic uveitis (2.56). Overall, FHV-1 DNA was detected in AH from 12 cats, 11 of which had uveitis. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that FHV-1 can infect intraocular tissues of cats and that intraocular FHV-1 infection may be associated with uveal inflammation in some cats.     

Effect of topical ophthalmic application of cidofovir on experimentally induced primary ocular feline herpesvirus-1 infection in cats

OBJECTIVE: To evaluate the efficacy of twice-daily ophthalmic application of 0.5% cidofovir solution in cats with experimentally induced primary ocular feline herpesvirus-1 (FHV-1) infection. ANIMALS: Twelve 6-month-old sexually intact male cats. PROCEDURES: Cats were randomly assigned to either a treatment or control group. Ocular infection with FHV-1 was induced (day 0) in all cats via inoculation of both eyes with 10(4) plaque-forming units of a plaque-purified FHV-1 field strain. Twice daily for 10 days beginning on day 4 after virus inoculation, the treatment group received 1 drop of 0.5% cidofovir in 1% carboxymethylcellulose in both eyes, and the control group received 1 drop of 1% carboxymethylcellulose in both eyes. A standardized scoring method was used to evaluate clinical signs of FHV-1 infection in each cat once daily for 24 days. The amount of ocular viral shedding was assessed by use of a quantitative real-time PCR procedure every 3 days during the study period. Clinical scores and viral quantification were averaged over the pretreatment (days 0 to 3), treatment (days 4 to 14), and posttreatment (days 15 to 24) periods for each cat. RESULTS: During the treatment period, clinical scores and amount of viral ocular shedding were significantly lower in the treatment group, compared with findings in the control group. CONCLUSIONS AND CLINICAL RELEVANCE: Twice-daily application of 0.5% cidofovir solution in both eyes significantly decreased the amount of viral shedding and the severity of clinical disease in cats with experimentally induced ocular FHV-1 infection.     

Prevalence of feline herpesvirus 1, Chlamydophila felis, and Mycoplasma spp DNA in conjunctival cells collected from cats with and without conjunctivitis

OBJECTIVE: To use PCR assays to determine the prevalence of feline herpesvirus 1 (FHV-1), Chlamydophila felis, and Mycoplasma spp DNA in conjunctival cells collected from cats with and without conjunctivitis; to compare results of conventional and real-time fluorogenic PCR assays for amplification of FHV-1 DNA; and to determine whether copy numbers of FHV-1 DNA are correlated with conjunctivitis. ANIMALS: 55 cats with active conjunctivitis, 39 healthy cats that never had conjunctivitis, and 32 cats with a history of conjunctivitis that had been resolved for at least 3 months. PROCEDURES: Samples were obtained by rolling cotton-tipped applicators on the ventral conjunctiva of awake cats treated topically with proparacaine. The DNA was extracted from the swab specimens and assessed in PCR assays to detect DNA of FHV-1 (fluorogenic PCR assay and conventional PCR assay), Mycoplasma spp (conventional PCR assay), and C felis (conventional PCR assay). RESULTS: Overall prevalence rates of FHV-1, C felis, and Mycoplasma spp as assessed by the conventional PCR assays were 6.7%, 3.2%, and 9.6%, respectively. Percentage concordance between conventional PCR and fluorogenic PCR assays for FHV-1 was 92.5%. There were no significant differences among the 3 groups of cats for the mean copy number of FHV-1 divided by the copy number of glyceraldehyde-3-phosphate dehydrogenase. CONCLUSIONS AND CLINICAL RELEVANCE: Mycoplasma spp were the most prevalent organism detected and was associated with conjunctivitis. This study could not confirm that there are increased copy numbers of FHV-1 DNA in cats with conjunctivitis, compared with the copy numbers for cats without conjunctivitis.     

Detection of feline herpesvirus 1 DNA in skin biopsy specimens from cats with or without dermatitis

OBJECTIVE: To compare detection rates of feline herpesvirus 1 (FHV-1) DNA in skin biopsy specimens from cats with herpetic dermatitis, cats with nonherpetic dermatitis, and cats without dermatitis. DESIGN: Prevalence survey. Animals-5 cats (9 biopsy specimens) with herpetic ulcerative dermatitis, 14 cats (17 biopsy specimens) with nonherpetic ulcerative dermatitis, and 8 cats (21 biopsy specimens) without clinically apparent skin lesions. PROCEDURES: A single-phase PCR assay was used to detect FHV-1 DNA in biopsy specimens. Assay results were compared with results of histologic examination. RESULTS: FHV-1 DNA was detected in all 9 biopsy specimens from the 5 cats with herpetic dermatitis and in 1 of 17 biopsy specimens from the 14 cats with nonherpetic dermatitis, but was not detected in any of the 21 biopsy specimens from the 8 cats without dermatitis. When results of histologic examination were used as the gold standard, sensitivity and specificity of the PCR assay were 100% and 95%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirmed that FHV-1 DNA can be detected in the skin of cats with herpetic dermatitis and suggest that the virus may play a causative role in the disease. In addition, the PCR assay may be useful in confirming a diagnosis of herpetic dermatitis.     

Feline herpesvirus

Feline herpesvirus (FHV-1; felid herpesvirus 1 (FeHV-1)) is an alphaherpesvirus of cats closely related to canine herpesvirus-1 and phocine herpesvirus-1. There is only one serotype of the virus and it is relatively homogenous genetically. FeHV-1 is an important cause of acute upper respiratory tract and ocular disease in cats. In addition, its role in more chronic ocular disease and skin lesions is increasingly being recognised. Epidemiologically, FeHV-1 behaves as a typical alphaherpesvirus whereby clinically recovered cats become latently infected carriers which undergo periodic episodes of virus reactivation, particularly after a stress. The primary site of latency is the trigeminal ganglion. Conventional inactivated and modified-live vaccines are available and protect reasonably well against disease but not infection, although viral shedding may be reduced. Genetically engineered vaccines have also been developed, both for FeHV-1 and as vector vaccines for other pathogens, but none is as yet marketed.     

Feline herpesvirus-1: ocular manifestations, diagnosis and treatment options

PRACTICAL RELEVANCE: Feline herpesvirus-1 (FHV-1) is a major cause of feline morbidity. Following exposure to the virus, virtually all cats become persistently infected and many of these will develop recrudescent disease on one or more occasions during their lifetime. Acute ocular herpetic disease manifests as conjunctivitis, corneal ulceration and keratitis, and can be severe and painful. Repeated bouts of recrudescent ocular disease can lead to progressive corneal pathology that can be ultimately blinding in affected cats. GLOBAL IMPORTANCE: FHV-1 has a worldwide distribution, with reported exposure rates in some cat populations of up to 97%. As such it is a significant cause of clinical disease in the global cat population. PATIENT GROUP: Young and adolescent cats are most at risk of acute primary disease, and the vast majority of these will become persistently infected. Around half of all persistently infected cats will shed virus at some stage in their life and these may develop recrudescent ocular disease. CLINICAL CHALLENGES: Treatment of FHV-1 ocular disease is challenging. Antiviral medications may be expensive, and require good owner and patient compliance. Clinical responses in patients can be variable. Selecting the appropriate therapeutic approach requires good clinical judgement, with assessment of factors such as severity and stage of clinical disease, patient and owner compliance, and financial considerations. EVIDENCE BASE: Although a wide range of antiviral treatments is available, few have been tested in controlled clinical trials. Therapeutic decisions are, therefore, often based on results of in vitro studies, case-based reports and anecdote. Large, masked, controlled clinical trials are required in order to determine the efficacy of the antiviral drugs currently available to treat FHV-1.     

Schirmer tear test values and tear film break-up times in cats with conjunctivitis

OBJECTIVES: (1) To document tear film break-up time (TFBUT) in a group of cats with conjunctivitis; (2) to determine if TFBUTs from cats with conjunctivitis vary significantly from previously established normal values for TFBUT in young cats without ocular disease; (3) to determine if a correlation exists between Schirmer tear test (STT) values and TFBUTs in cats with conjunctivitis; (4) to determine if the TFBUTs in cats with conjunctivitis are influenced by the detection of DNA from feline herpes virus-type 1 (FHV-1), Chlamydophila felis, Mycoplasma spp., and feline calicivirus. ANIMALS STUDIED: Fourteen cats between the ages of 0.8 years to 12 years with active, untreated conjunctivitis and without active keratitis or other ocular or systemic abnormalities were included in this study. Procedures Complete ophthalmic examinations, including TFBUT, were performed on all cats. Polymerase chain reaction (PCR) screening for FHV-1, Chlamydophila felis, Mycoplasma spp., and feline calicivirus was performed on conjunctival swabs from affected eyes and blood samples from all cats. RESULTS: Mean TFBUT for cats in this study was 8.9 (+/- 4.8) s in the right eye (OD) and 8.1 (+/- 4.6) s in the left eye (OS). No correlation existed between mean TFBUTs and mean STT values OD or OS. Conjunctival swabs from seven cats (n = 9 eyes) tested positive via PCR for one of the above infectious agents. Blood samples from nine cats tested positive for FHV-1. Mean TFBUTs for cats from which the DNA from FHV-1 was isolated from the blood were significantly lower than mean TFBUTs for cats from which no such DNA was isolated from the blood. CONCLUSIONS: In this study, the mean TFBUT in cats with conjunctivitis was significantly lower than previously established values for clinically healthy cats. This supports the theory that qualitative tear film deficiency, and thus tear film instability, may play a role in the pathogenesis of feline conjunctivitis. Qualitative tear film deficiency may predispose to the development of conjunctivitis or may occur secondarily to this condition.     

Efficacy of topical aciclovir for the treatment of feline herpetic keratitis: results of a prospective clinical trial and data from in vitro investigations

This study aimed to evaluate the efficacy of topical ophthalmic aciclovir applied five times daily as a treatment for feline herpesvirus type 1 (FHV-1) keratitis in a group of cats in a first-opinion practice setting. Cats with ocular signs indicative of FHV-1 or Chlamydophila species infection, predominantly conjunctivitis and keratitis, were tested for FHV-1 antigen using an immunofluorescent technique on air-dried conjunctival swabs. They were first treated with topical chlortetracycline with efficacy against Chlamydophila species and then, in cases positive for FHV-1, with topical aciclovir. The time to recovery was determined and illustrated using a Kaplan-Meier plot. Three cats were infected with Chlamydophila species and showed a median time to recovery of 14 days (95 per cent confidence interval [CI] 10 to 18 days), while 30 cats infected with FHV-1 showed a median time to recovery of 12 days (95 per cent CI 10 to 14 days). The drug dose at which 50 per cent plaque reduction (ED50) occurred in a standard plaque reduction assay was determined in an in vitro study. This showed a mean (SD) ED50 of aciclovir of 25 (3.5) mg/ml compared with 0.4 (0.05) mg/ml for trifluorothymidine, a drug known to be efficacious against FHV-1. The study shows that even though aciclovir is generally considered to lack efficacy against ocular FHV-1 infection, when used frequently it can have a beneficial effect in FHV-1 conjunctivitis and keratitis.     

Clinical improvement in feline herpesvirus 1 infected cats by oral low dose of interleukin-12 plus interferon-gamma

Feline herpesvirus 1 (FHV-1) is a widespread cat pathogen inducing rhinitis, conjunctivitis and corneal ulcers. To alleviate acute FHV-1-induced disease, antiviral agents are used often with antibiotics. But sometimes, these treatments, as well as conventional doses of cytokines have moderate efficacy and/or collateral effects. Herein we have investigated the effects of low dose interleukin (IL)-12 plus interferon (IFN)-gamma, prepared by Sequential Kinetic Activated (SKA), on the treatment of FHV-1 infection. Twenty-five, unvaccinated FHV-1-positive cats were recruited into a prospective, randomized, placebo-controlled, double-blinded clinical trial. Fifteen cats were treated for 6 months with oral low doses of SKA IL-12 plus IFN-gamma and 10 cats were treated with placebo. At 1, 6 and 12 months (follow-up) after the beginning of treatment, clinical assessment, PCR assay and blood count were carried out. At follow-up, in treated group, we observed significant (p < 0.05) improvements in clinical signs and PCR became negative in 12/15 cats (80%). In placebo, 10/10 cats were PCR-positive, with improvements (30%) or worsening (70%) in clinical signs. Blood values were normal in both groups.Our results show that the low dose therapy, based on activated solutions of IL-12 plus IFN-gamma, represents a novel approach to treat FHV-1 infection in cats.     

Relative sensitivity of polymerase chain reaction assays used for detection of feline herpesvirus type 1 DNA in clinical samples and commercial vaccines

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.