Onset of immunity in kittens after vaccination with a non-adjuvanted vaccine against feline panleucopenia, feline calicivirus and feline herpesvirus

The induction of a quick onset of immunity against feline parvovirus (FPV), feline herpesvirus (FHV) and feline calicivirus (FCV) is critical both in young kittens after the decline of maternal antibodies and in cats at high risk of exposure. The onset of immunity for the core components was evaluated in 8–9 week old specific pathogen free kittens by challenge 1 week after vaccination with a combined modified live (FPV, FHV) and inactivated (FCV) vaccine. The protection obtained 1 week after vaccination was compared to that obtained when the challenge was performed 3–4 weeks after vaccination. The protocol consisted of a single injection for vaccination against FPV and two injections 4 weeks apart for FHV and FCV.At 1 week after vaccination, the kittens showed no FPV-induced clinical signs or leukopenia following challenge, and after FCV and FHV challenges the clinical score was significantly lower in vaccinated animals than in controls. Interestingly, the relative efficacy of the vaccination was comparable whether the animals were challenged 1 week or 3–4 weeks after vaccination, indicating that the onset of protection occurred within 7 days of vaccination. Following the 1-week challenge, excretion of FPV, FHV and FCV was significantly reduced in vaccinated cats compared to control kittens, confirming the onset of immunity within 7 days of vaccination.     

Effects of human recombinant alpha-2b interferon and feline recombinant omega interferon on in vitro replication of feline herpesvirus-1

OBJECTIVE: To evaluate the effects of recombinant human interferon alpha-2b (rHuIFN-alpha2b) and recombinant feline interferon omega (rFeIFN-omega) on in vitro replication of feline herpesvirus (FHV)-1. SAMPLE POPULATION: Cultures of Crandell-Rees feline kidney (CRFK) cells. PROCEDURES: CRFK cells were treated with rFeIFN-omega or rHuIFN-alpha2b at concentrations ranging from 100 to 500,000 U/mL. Cultures were then inoculated with FHV-1. Constant concentrations of interferon products were maintained throughout the study. Reductions in the number and size of plaques were used as indicators of antiviral activity. Six plaque reduction assays were performed in duplicate. A 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide assay was used to detect cytotoxic effects of interferon. A 1-way ANOVA and Dunnett test were used to determine significant differences. RESULTS: Treatment with rFeIFN-omega at various concentrations resulted in significant reductions in the number of plaques (100,000 U/mL, 54.7%; and 500,000 U/mL, 59.8%) and in plaque size (100,000 U/mL, 47.5%; 250,000 U/mL, 81.0%; and 500,000 U/mL; 70.5%). Treatment with various concentrations of rHuIFN-alpha2b resulted in a significant reduction in plaque size (100,000 U/mL, 56.0%; 250,000 U/mL, 75.7%; and 500,000 U/mL, 69.0%). None of the tested concentrations of interferon caused significant cellular toxicosis. CONCLUSIONS AND CLINICAL RELEVANCE: At some of the higher concentrations, the antiviral effect of rFeIFN-omega was greater than the antiviral effect of rHuIFN-alpha2b. Reduction in plaque size appeared to be a good indicator of the antiviral activity of interferon against FHV-1.     

Carrier-state infection of feline T-lymphoblastoid cells with feline calicivirus

The susceptibility of feline T lymphocytes to feline calicivirus (FCV) in vitro was investigated using feline T-lymphoblastoid cell lines, namely MYA-1 and FL74 cells. The virus titers of supernatants in FCV-infected MYA-1 and FL74 cell cultures increased rapidly, and FCV antigens were also detected in the FCV-infected cells. There were slight differences in the molecular weights of capsid proteins expressed in FCV-infected MYA-1, FL74 and Crandell feline kidney cells. MYA-1 and FL74 cells were productively and persistently infected with FCV, and FCV antigens were observed in the FCV-infected cells for more than one month. At 3 months post infection, FCV-infected FL74 cells that stopped producing infectious FCV could be reinfected with FCV. However, no cytopathic effects were observed.     

A study of feline upper respiratory tract disease with reference to prevalence and risk factors for infection with feline calicivirus and feline herpesvirus.

A cross-sectional survey of a convenience sample of cats was carried out to determine the prevalence of and risk factors for respiratory tract disease, feline calicivirus (FCV) infection and feline herpesvirus (FHV) infection. Seven hundred and forty cats were studied; samples for isolation of FCV and FHV were obtained from 622 (84%). Data on individual cat and household variables were obtained by questionnaire for each cat and analysed using univariable and logistic regression analysis. Thirty-eight percent (282/740) of cats surveyed had respiratory tract disease. Eighteen of 24 predictor variables were found to be significantly (P<0.05) associated with the presence of respiratory tract disease in a cat on univariable analysis. Following logistic regression, several factors retained significance including isolation of FCV and FHV, younger cats (4-11 months of age) and multiple cat households. A negative association was found with breeding catteries and other types of household in comparison with rescue catteries. Overall, feline calicivirus was isolated from 162/622 (26%) of cats sampled; 33% of the cats with respiratory tract disease were FCV positive compared to 21% of healthy cats. Variables significantly associated with FCV isolation on logistic regression were the presence of respiratory tract disease and contact with dogs with and without respiratory tract disease. Feline herpesvirus was isolated from 30/622 (5%) of all cats sampled; 11% of cats with respiratory tract disease were FHV positive compared to 1% of healthy cats. Variables significantly associated with FHV isolation on univariable analysis included age, gender, and the presence of respiratory tract disease. Vaccination showed a negative association. Logistic regression analysis of the data for FHV was limited by the sample size and the low prevalence of FHV.     

Isolation of feline calicivirus and feline herpesvirus from domestic cats 1980 to 1989

Isolation rates of feline herpesvirus (FHV) and feline calicivirus (FCV) from oropharyngeal swabs, taken from 6866 cats in 1980 to 1989 were studied retrospectively. FCV was isolated from 1364 (19.9 per cent) and FHV from 285 (4.2 per cent). The ratio of FCV:FHV isolations varied from 1.3:1 to 15:1 in individual years with an overall ratio of 4.8:1. Isolation of both viruses was fairly uniform for each year and there was no breed or sex disposition to either virus. Of 872 cats shedding FCV and 213 cats shedding FHV, of known age, 447 (51.3 per cent) with FCV and 140 (65.7 per cent) with FHV were under one year old, compared to only 35.3 per cent of the whole population sampled. For the years 1985 to 1989, more information was obtained about the cases. Of 4626 cats tested, 1180 (25.5 per cent) had acute upper respiratory tract disease (URTD) of which 348 (29.5 per cent) were shedding FCV and 162 (13.7 per cent) FHV. A further 597 had chronic URTD and of these, 102 (17.1 per cent) were shedding FCV and 18 (3 per cent) FHV. In 120 cases of suspected vaccine reaction/breakdown, FCV was isolated from 34 (28.3 per cent) and FHV from only two (1.7 per cent). FHV was not isolated from any of 412 cases presenting with chronic gingivitis/stomatitis alone; 181 (43.9 per cent) were shedding FCV and when cats with other signs in addition to chronic gingivitis were included, this proportion increased to 70.4 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of protective antibody titers against feline panleukopenia virus, feline herpesvirus-1, and feline calicivirus in shelter cats using a point-of-care ELISA

Serum antibody titers are a useful measurement of protection against infection (feline panleukopenia virus [FPV]) or clinical disease (feline herpesvirus-1 [FHV] and feline calicivirus [FCV]), and their determination has been recommended as part of disease outbreak management in animal shelters. The objective of this study was to determine the sensitivity, specificity, and inter-observer and inter-assay agreement of two semi-quantitative point-of-care assays for the detection of protective antibody titers (PAT) against FPV, FHV and FCV in shelter cats. Low sensitivity for FPV antibodies (28%) rendered a canine point-of-care assay inappropriate for use in cats. The feline point-of-care assay also had low sensitivity (49%) and low negative predictive value (74%) for FPV PAT detection, but was highly accurate in the assessment of FHV and FCV PAT. Improvements in accuracy and repeatability of FPV PAT determination could make this tool a valuable component of a disease outbreak response in animal shelters.     

Relevance of feline calicivirus, feline immunodeficiency virus, feline leukemia virus, feline herpesvirus and Bartonella henselae in cats with chronic gingivostomatitis

Despite its common occurrence, the aetiology of chronic gingivostomatitis in cats remains uncertain. Aetiology is likely multifactorial, and several infectious agents may be associated with chronic gingivostomatitis. The purpose of this study was to investigate the prevalence of feline calicivirus (FCV), feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), feline herpesvirus (FHV), and Bartonella henselae (B. henselae) in cats with chronic gingivostomatitis and in an age-matched control group. In addition, other factors, e. g., environmental conditions were investigated. In 52 cats with chronic gingivostomatitis and 50 healthy age-matched control cats, the presence of FCV ribonucleic acid (RNA), and FHV deoxyribonucleic acid (DNA) (polymerase chain reaction [PCR] from oropharyngeal swabs), and B. henselae DNA (PCR from oropharyngeal swabs and blood), as well as FeLV antigen (serum), and antibodies against FCV, B. henselae, and FIV (serum) were examined. FCV RNA was significantly more common in cats with chronic gingivostomatitis (53.8%, p < 0.001) than in controls (14.0%); a significant difference was also found in the prevalence of antibodies to FCV between the cats with chronic gingivostomatitis (78.8%, p = 0.023) and controls (58.0%). Of the other infectious agents investigated, there was no significant difference in the prevalence between the cats with chronic gingivostomatitis and the controls. The results of this study allow the conclusion that FCV, but no other infectious agents, is commonly associated with chronic gingivostomatitis in cats.     

Isolation of feline herpesvirus-1 and feline calicivirus from healthy cats in Swedish breeding catteries

Feline calicivirus (FCV) could be isolated from four cats (2.6%) and feline herpesvirus-1 (FHV) from none of 152 clinically healthy cats from 22 Swedish breeding catteries. These cats had all previously shown signs of respiratory tract disease or conjunctivitis, although several years ago. The results suggest that carriers of FCV and FHV were uncommon in Swedish breeding catteries studied. Prevalence rates in other European countries and North America are usually higher, especially of FCV. The lower prevalence rates in our study might be explained by test group selection, differences in factors such as management, environment, or genetic constitution of the cats, or by sample handling. It was concluded that the presence of an FCV shedder in the cattery does not mean that all cats in the group are infected, but special measures are recommended to avoid infection of susceptible cats.     

Common virus infections in cats, before and after being placed in shelters, with emphasis on feline enteric coronavirus

The purpose of this study was to determine the origin and subsequent spread of feline calicivirus (FCV), feline herpesvirus (FHV), and feline enteric coronavirus (FECV) in cats relinquished to shelters. FCV was isolated from the oral fauces of 11% of healthy cats upon entry, and isolation rates were highest for kittens (33%). FHV shedding was very low (4%) at the time of entry and occurred mainly in juveniles. FECV shedding was also common among newly relinquished cats (33%), especially older kittens and juveniles (90%). The subsequent spread of all three viruses was rapid and efficient in the shelter environment. Fifteen percent of cats were shedding FCV, 52% FHV, and 60% FECV after 1 week. More detailed studies were done with FECV shedding, which could be accurately quantitated. The amounts of FECV shed by infected cats ranged from 10(2)to 10(16)particles/swab of feces. FECV shedding was several logs higher in young kittens with primary infection than adult cats with primary infections. The mean levels of FECV shedding among adults were the same for primary and chronic infections. Although shelters were not the primary source of these viruses for many relinquished cats, factors intrinsic to the shelter environment were critical in amplifying shedding and spread to susceptible individuals. Extrinsic factors were especially important for the spread of FHV and FECV. FHV shedding rates increased from 4% to 50% in 1 week's time. The speed and magnitude of the increase in FHV shedding suggested that there was reactivation of latent infections as well as acquisition of new infections. FECV shedding increased 10 to 1,000,000 fold in 1 week among cats that were already infected at entry, and more than one-half of initially negative cats were shedding FECV a week later. Feline calicivirus infection was the least likely to spread in the shelter. The infection rate only increased from 11 to 15% in 1 week.     

Effects of interferon-alpha on cytopathic changes and titers for feline herpesvirus-1 in primary cultures of feline corneal epithelial cells

OBJECTIVE: To assess the effect of interferon (IFN)-alpha on viability of feline corneal epithelial cells, replication of feline herpesvirus (FHV)-1, and virus-induced cytopathic changes. SAMPLE POPULATION: Healthy eyes from 10 recently euthanatized cats. PROCEDURE: 4 replicate primary cultures of feline corneal epithelial cells were grown after the addition of 10(2) to 10(6) IU of IFN-alpha/mL. Cultures were examined every 24 hours for evidence of cytotoxic changes. Viable cell counts and percentage of viable cells were determined 48 hours after initiation of culture. In a separate experiment, cultures of corneal cells were inoculated with FHV-1 and cultured for 72 hours with or without 10(5) IU of IFN-alpha/mL. The FHV-1-infected cultures were evaluated for viral-induced cytopathic effects, and viral titers were determined in samples of culture supernatant. RESULTS: Interferon-alpha did not have cytotoxic effects on corneal epithelial cells at concentrations ranging from 10(2) to 10(6) IU of IFN-alpha/mL. Interferon-alpha at a concentration of 10(5) IU/mL significantly reduced the cytopathic changes and FHV-1 titers. CONCLUSIONS AND CLINICAL RELEVANCE: Lack of in vitro cytotoxic effects and efficacy against FHV-1 infection in primary cultures of feline corneal cells suggests that the in vivo therapeutic effect of IFN-a should be assessed in controlled clinical trials.     

EQUINE HERPESVIRUSES: ON THE DIFFERENTIATION OF RESPIRATORY FROM FOETAL STRAINS OF TYPE 1

SUMMARY Confirmation of the occurrence of equine herpesvirus type 1 (EHV1) abortion in both epizootic and sporadic form epizootic in Australia for the first time in 1977 against a background in which a reasonably diligent search for such viruses during the preceeding 11 years failed to associate EHV1 with abortion, provided a special opportunity to compare the properties of the newly isolated foetal (F) strains with a collection of endemic respiratory (R) strains that had been recovered at fairly regular intervals since 1967. Using plaque size and host cell range all of 7 R strains tested were clearly distinguishable from 7 of 11 F isolates. The remaining 4 F strains had plaque diameters of R strains but 3 of the 4 viruses conformed in their host cell range with F strains. Only one F isolate (from Tasmania) had both plaque morphology and host cell range of R strain viruses. The mean diameter of plaques produced by R strains in equine foetal kidney (EFK) cells after 4 days under a methyl cellulose overlay was 1.52 mm (range 1.30–1.84 mm) while the mean diameter of small plaques produced by F strains was 0.82 mm (range 0.68–0.91 mm). In addition to EFK cells all R and F strains grew in an equine dermal (EDerm) cell line and all but two of 19 isolates grew in a pig kidney (PK) cell line. None of the low passage R strains grew in bovine embryo tracheal (EBTr) or feline embryo (FEmb) cells whereas all but one of 11 F isolates grew in EBTr cells. 8/11F isolates also grew in FEmb cell line. Growth of viruses at 33° and 40.5°cf. a usual growth temperature of 37° was of no detectable value in differentiating R and F strains of EHV1. In a limited geographic and time frame the criteria of plaque size in EFK cells and growth in EBTr cells unambiguously distinguished between R and F isolates and represent simple markers worthy of additional study.     

Factors associated with upper respiratory tract disease caused by feline herpesvirus, feline calicivirus, Chlamydophila felis and Bordetella bronchiseptica in cats: experience from 218 European catteries

A full history of the management practices and the prevalence of upper respiratory tract disease (URTD) at 218 rescue shelters, breeding establishments and private households with five or more cats was recorded. Oropharyngeal and conjunctival swabs and blood samples were taken from 1748 cats. The prevalences of feline herpesvirus (FHV), feline calicivirus (FCV), Chlamydophila felis and Bordetella bronchiseptica were determined by PCR on swab samples. An ELISA was applied to determine the prevalence of antibodies to B. bronchiseptica. The rates of detection by PCR of each pathogen in the cats in catteries with and without ongoing URTD were, respectively, FHV 16 per cent and 8 per cent; FCV 47 per cent and 29 per cent; C. felis 10 per cent and 3 per cent; and B. bronchiseptica 5 per cent and 1.3 per cent; the seroprevalences of B. bronchiseptica were 61 per cent and 41 per cent, respectively. There was evidence that FHV, FCV and B. bronchiseptica played a role in URTD. The risk factors associated with the disease were less than excellent hygiene, contact with dogs with URTD, and larger numbers of cats in the cattery or household.     

Comparison of prevalence of feline herpesvirus type 1, calicivirus and parvovirus infections in domestic and leopard cats in Vietnam

A serosurvey of feline herpesvirus type 1 (FHV-1), feline calicivirus (FCV), and feline parvovirus (FPV) in cats from Ho Chi Minh City area in southern Vietnam was conducted in December 1998, and we compared the results with our previous results in northern Vietnam (Hanoi area). The positive rate of FHV and FCV in domestic cats were 44% and 74%, respectively. They were rather higher than those in Hanoi area, while the seropositivity of FPV (44%) was similar to that in Hanoi area. In leopard cats, the positive rate of FPV was high (3/4) and it indicated that FPV was prevailing in leopard cats in Vietnam.     

Effects of cidofovir on cell death and replication of feline herpesvirus-1 in cultured feline corneal epithelial cells

OBJECTIVE: To assess the effect of cidofovir on viability of feline corneal epithelial (FCE) cells, replication of feline herpesvirus (FHV)-1, and virus-induced cytopathic changes. SAMPLE POPULATION: Healthy eyes from 14 recently euthanatized cats. PROCEDURE: Cidofovir at concentrations ranging from 0.05 to 0.000005 mg/mL was added to primary cultures of FCE cells, and cytopathic changes and effects on cell proliferation and cell viability were determined during the subsequent 48 hours. Efficacy of cidofovir (0.02 and 0.05 mg/mL) to prevent in vitro infection of FCE cells with FHV-1 was determined during 72 hours of culture by assessing viral cytopathic effects and viral titers. RESULTS: Cidofovir at concentrations of 0.05, 0.005, and 0.0005 mg/mL significantly reduced mean viable cell counts, and cidofovir at a concentration of 0.05 mg/mL significantly reduced the percentage viability of cultured FCE cells. Minimal cytopathic changes were observed at concentrations of 0.02 and 0.05 mg of cidofovir/mL. Cidofovir at concentrations of 0.05 and 0.02 mg/mL abrogated the cytopathic effects attributable to FHV-1 infection and reduced viral titers from > or =10(14) TCID(50)/mL to < or =10(3.5) TCID50/mL. CONCLUSIONS AND CLINICAL RELEVANCE: Cidofovir in vitro was highly efficacious against FHV-1 infection of a primary culture of FCE cells but had cytostatic effects on cultured cells.     

Effects of bovine lactoferrin on in vitro replication of feline herpesvirus

Objective To investigate the effects of bovine lactoferrin on in vitro replication of feline herpes virus (FHV‐1) and to determine at what points during viral replication these effects occur. Sample population Cultured Crandell‐Reese feline kidney (CRFK) cells and FHV‐1 strain 727. Procedure Five concentrations of bovine lactoferrin (0.5, 1, 2, 5, and 10 mg/mL) were added at one or more of three time points during conventional plaque reduction assays: (a) uninfected CRFK cells were incubated in lactoferrin‐containing medium for 30 min prior to viral adsorption; (b) virus was suspended in lactoferrin‐containing medium prior to and during adsorption, or (c) CRFK cells were incubated with lactoferrin‐containing medium for 48 h following viral adsorption. Plaques were counted and antiviral effect expressed as percent inhibition relative to control medium that contained no lactoferrin. Results Exposure of CRFK cells to lactoferrin prior to or during viral adsorption inhibited FHV‐1 replication by 87–96% (mean: 91%). Application of lactoferrin following viral adsorption had no appreciable effect on FHV‐1 replication. No additive or synergistic effects were noted when lactoferrin was added at multiple steps. These effects were similar at all concentrations of lactoferrin tested. Cytotoxic effects of lactoferrin on CRFK cells were not observed at any concentration tested. Conclusions and clinical relevance Bovine lactoferrin has a notable inhibitory effect on the in vitro replication of FHV‐1 prior to and during, but not following viral adsorption. These findings strongly suggest that lactoferrin inhibits FHV‐1 adsorption to the cell surface and/or penetration of the virus into the cell. Clinical effects of topical lactoferrin in acute or recrudescent herpetic episodes in cats warrant investigation.     

Culture of feline corneal epithelial cells and infection with feline herpesvirus-1 as an investigative tool

OBJECTIVE: To isolate and characterize pure cultures of feline corneal epithelial cells and to assess the extent and nature of feline herpesvirus (FHV)-1 infection in these cells. SAMPLE POPULATION: Healthy eyes from 23 recently euthanatized cats. PROCEDURE: Stroma and epithelium of the rostral portion of the cornea were surgically isolated, and epithelial cells were detached from the stroma by enzymatic incubation. Epithelial cells were cultured in hormone-supplemented media. Cells were passaged, and cytokeratin expression was assessed. Cells were then infected with FHV-1, and cytopathic effects were determined. RESULTS: Cell cultures were readily established from samples obtained from each eye and could be maintained through 6 passages. Cultured cells expressed cytokeratins 3 and 12 but not other cytokeratins. Infection with FHV-1 was rapid and caused widespread cytopathic effects. CONCLUSIONS AND CLINICAL RELEVANCE: Feline corneal cells cultured in vitro during multiple passages maintain consistent morphologic characteristics and intermediate filament expression. They are susceptible to infection with FHV-1 and may provide a useful in vitro model for investigation of ocular drugs.     

Interferon induction in bovine and feline monolayer cultures by four bluetongue virus serotypes.

The interferon inducing ability of bluetongue viruses was studied in bovine and feline monolayer cultures inoculated with each of four bluetongue virus serotypes. Interferon was assayed by a plaque reduction method in monolayer cultures with vesicular stomatitis virus as challenge virus. Interferon was produced by bovine turbinate, Georgia bovine kidney, and Crandell feline kidney monolayer cultures in response to bluetongue virus serotypes 10, 11, 13 and 17. The antiviral substances produced by the bluetongue virus infected cultures had properties of interferon.     

Mapping neutralizing and non-neutralizing epitopes on the capsid protein of feline calicivirus

Neutralizing epitopes on feline calicivirus (FCV) capsid protein were mapped using chimeric capsid proteins recombinant between two FCV isolates that do not show any cross-neutralization. The three chimeric proteins examined were expressed in murine L929 cells employing an MVA/T7 vaccinia virus expression system and inoculated into major histocompatibility complex haplotype-matched C3/HN mice. Based on the neutralizing antibody titre the neutralizing epitope(s) could be mapped to the 5' hypervariable region of the E region or potentially to the C region. The epitopes of some non-neutralizing antibodies were mapped with the same chimeric proteins to the regions B or D and F of the FCV capsid protein.