A nosocomial outbreak of feline calicivirus associated virulent systemic disease in France

Molecular epidemiology and phylogenetic analysis of feline calicivirus in Kunshan, China

Feline calicivirus (FCV) is a highly contagious virus in cats, which typically causes respiratory tract and oral infections. Despite vaccination against FCV being a regular practice in China, new FCV cases still occur. Antigenic diversity of FCV hinders the effective control by vaccination. This is first report which aims to investigate the molecular epidemiology and molecular characteristics of FCV in Kunshan, China. The nasopharyngeal swabs were collected from cats showing variable clinical signs from different animal clinics in Kunshan from 2022 to 2023. Preliminary detection and sequencing of the FCV capsid gene were performed to study genetic diversity and evolutionary characteristics. FCV-RNA was identified in 52 (26%) of the samples using RT-PCR. A significant association was found between FCV-positive detection rate, age, gender, vaccination status and living environment, while a non-significant association was found with breed of cats. Nucleotide analysis revealed two genotypes, GI and GII. GII predominated in Kunshan, with diverse strains and amino acid variations potentially affecting vaccination efficacy and FCV detection. Notably, analysis pinpointed certain strains' association with FCV-virulent systemic disease pathotypes. This investigation sheds light on FCV dynamics, which may aid in developing better prevention strategies and future vaccine designs against circulating FCV genotypes.

In Vitro Antiviral and Virucidal Activity of Ozone against Feline Calicivirus

The Caliciviridae family includes several viral pathogens of humans and animals, including norovirus (NoV), genus Norovirus, and feline calicivirus (FCV), genus Vesivirus. Due to their resistance in the environment, NoV and FCV may give rise to nosocomial infections, and indirect transmission plays a major role in their diffusion in susceptible populations. A pillar of the control of viruses resistant to an environment is the adoption of prophylaR1.6ctic measures, including disinfection. Since NoVs are not cultivatable in common cell cultures, FCV has been largely used as a surrogate of NoV for the assessment of effective disinfectants. Ozone (O3), a molecule with strong oxidizing properties, has shown strong microbicidal activity on bacteria, fungi, protozoa, and viruses. In this study, the virucidal and antiviral activities of an O3/O2 gas mixture containing O3 were tested at different concentrations (20, 35, and 50 μg/mL) for distinct contact times against FCV. The O3/O2 gas mixture showed virucidal and antiviral activities against FCV in a dose- and contact time-dependent fashion. Ozonation could be considered as a valid strategy for the disinfection of environments at risk of contamination by FCV and NoV.

Virulent systemic feline calicivirus infection: a case report and first description in Ireland

BACKGROUND

Virulent systemic feline calicivirus (VS-FCV) infection is an emerging disease. It is distinct from classic oronasal calicivirus infection as it manifests with unique systemic signs including severe cutaneous ulcerations, limb oedema, and high mortality, even in adequately vaccinated cats. Devastating epizootic outbreaks with hospital-acquired infections have been described in the United States, the United Kingdom, continental Europe and Australia with up to 54 cats affected in one outbreak and a mortality rate of up to 86%. This highly contagious and potentially fatal disease has not yet been reported in Ireland.

CASE PRESENTATION

An 11-month-old male neutered vaccinated domestic shorthair cat was presented with a 10-day history of lethargy, decreased appetite and progressively worsening pitting oedema in all four limbs. The signs were first noted after another kitten from a high-density cat shelter was introduced in to the household. Additional physical examination findings included marked pyrexia, and lingual and cutaneous ulcers. Virulent systemic feline calicivirus was diagnosed based on compatible history and clinical signs, exclusion of other causes, and calicivirus isolation by RT-PCR both in blood and oropharyngeal samples. Negative calicivirus RT-PCR in blood following resolution of the clinical signs further supported the diagnosis.

CONCLUSION

This case represents the first known case of VS-FCV infection in Ireland. Given the severity of the clinical signs, and the high risk for epizootic outbreaks, Irish veterinarians should be aware of the disease to ensure prompt diagnosis and implementation of adequate preventive measures, in order to limit the threat that this disease represents for the wider cat population and particularly given the risk of hospital-acquired VS-FCV infection. Virulent systemic calicivirus should be suspected in cats with pyrexia of unknown origin, oedema or ulceration affecting the limbs or the face, and exposure to rescue cats from high-density households.

High-resolution melting analysis for simultaneous detection and discrimination between wild-type and vaccine strains of feline calicivirus

High-resolution melting (HRM) analysis, a post-polymerase chain reaction (PCR) application in a single closed tube, is the straightforward method for simultaneous detection, genotyping, and mutation scanning, enabling more significant dynamic detection and sequencing-free turnaround time. This study aimed to establish a combined reverse-transcription quantitative PCR and HRM (RT-qPCR-HRM) assay for diagnosing and genotyping feline calicivirus (FCV). This developed method was validated with constructed FCV plasmids, clinical swab samples from living cats, fresh-frozen lung tissues from necropsied cats, and four available FCV vaccines. We performed RT-qPCR to amplify a 99-base pair sequence, targeting a segment between open reading frame (ORF) 1 and ORF2. Subsequently, the HRM assay was promptly applied using Rotor-Gene Q® Software. The results significantly revealed simultaneous detection and genetic discrimination between commercially available FCV vaccine strains, wild-type Thai FCV strains, and VS-FCV strains within a single PCR reaction. There was no cross-reactivity with other feline common viruses, including feline herpesvirus-1, feline coronavirus, feline leukemia virus, feline immunodeficiency virus, and feline morbillivirus. The detection limit of the assay was 6.18 × 101 copies/µl. This study, therefore, is the first demonstration of the uses and benefits of the RT-qPCR-HRM assay for FCV detection and strain differentiation in naturally infected cats.

A cDNA-based reverse genetics system for feline calicivirus identifies the 3' untranslated region as an essential element for viral replication

Virulent systemic feline calicivirus (VS-FCV) is a newly emerging FCV variant that is associated with a severe acute multisystem disease in cats that is characterized by jaundice, oedema, and high mortality (approximately 70%). VS-FCV has spread throughout the world, but there are no effective vaccines or therapeutic options to combat infection. VS-FCV may therefore pose a serious threat to the health of felines. The genomic characteristics and functions of VS-FCV are still poorly understood, and the reason for its increased pathogenicity is unknown. Reverse genetics systems are powerful tools for studying the molecular biology of RNA viruses, but a reverse genetics system for VS-FCV has not yet been reported. In this study, we developed a plasmid-based reverse genetics system for VS-FCV in which infectious progeny virus is produced in plasmid-transfected CRFK cells. Using this system, we found that the 3' untranslated region (UTR) and poly(A) tail are important for maintaining the infection and replication capacity of VS-FCV and that shortening of the poly(A) tail to less than 28 bases eliminated the ability to rescue infectious progeny virus. Whether these observations are unique to VS-FCV or represent more-general features of FCV remains to be determined. In conclusion, we successfully established a rapid and efficient VS-FCV reverse genetics system, which provides a good platform for future research on the gene functions and pathogenesis of VS-FCV. The effects of the deletion of 3' UTR and poly(A) tail on VS-FCV infectivity and replication also provided new information about the pathogenesis of VS-FCV.

Detection and Characterization of Feline Calicivirus Associated with Paw and Mouth Disease

Feline calicivirus (FCV) infection in cats can led to several diverse clinical presentations, ranging from mild upper respiratory signs to virulent systemic disease. Herein, we report a paw and mouth disease case in a 7-year-old household cat due to an FCV infection. An asymptomatic cat living in the same household was also infected with FCV. Clinical and pathological investigations were combined with the molecular and phenotypical characterization of the FCV strains. The RNA of the FCV was detected using qualitative and quantitative reverse transcription (RT)-PCR assays, and FCV antigen was confirmed by immunohistochemistry. After the whole genome analysis, the strains detected in the two cats appeared to be genetically diverse from FCVs previously detected in association with paw and mouth disease and with virulent systemic disease. Interestingly, the isolates obtained in this study were resistant to low pH conditions and slightly susceptible to bile salts, but they were susceptible to a trypsin treatment, revealing a phenotype pattern that is different from that which has been observed for respiratory FCVs.

Calicivirus Infection in Cats

Feline calicivirus (FCV) is a common pathogen in domestic cats that is highly contagious, resistant to many disinfectants and demonstrates a high genetic variability. FCV infection can lead to serious or even fatal diseases. In this review, the European Advisory Board on Cat Diseases (ABCD), a scientifically independent board of experts in feline medicine from 11 European countries, presents the current knowledge of FCV infection and fills gaps with expert opinions. FCV infections are particularly problematic in multicat environments. FCV-infected cats often show painful erosions in the mouth and mild upper respiratory disease and, particularly in kittens, even fatal pneumonia. However, infection can be associated with chronic gingivostomatitis. Rarely, highly virulent FCV variants can induce severe systemic disease with epizootic spread and high mortality. FCV can best be detected by reverse-transcriptase PCR. However, a negative result does not rule out FCV infection and healthy cats can test positive. All cats should be vaccinated against FCV (core vaccine); however, vaccination protects cats from disease but not from infection. Considering the high variability of FCV, changing to different vaccine strain(s) may be of benefit if disease occurs in fully vaccinated cats. Infection-induced immunity is not life-long and does not protect against all strains; therefore, vaccination of cats that have recovered from caliciviral disease is recommended.

Feline Calicivirus Virulent Systemic Disease: Clinical Epidemiology, Analysis of Viral Isolates and In Vitro Efficacy of Novel Antivirals in Australian Outbreaks

Feline calicivirus (FCV) causes upper respiratory tract disease (URTD) and sporadic outbreaks of virulent systemic disease (FCV-VSD). The basis for the increased pathogenicity of FCV-VSD viruses is incompletely understood, and antivirals for FCV-VSD have yet to be developed. We investigated the clinicoepidemiology and viral features of three FCV-VSD outbreaks in Australia and evaluated the in vitro efficacy of nitazoxanide (NTZ), 2′-C-methylcytidine (2CMC) and NITD-008 against FCV-VSD viruses. Overall mortality among 23 cases of FCV-VSD was 39%. Metagenomic sequencing identified five genetically distinct FCV lineages within the three outbreaks, all seemingly evolving in situ in Australia. Notably, no mutations that clearly distinguished FCV-URTD from FCV-VSD phenotypes were identified. One FCV-URTD strain likely originated from a recombination event. Analysis of seven amino-acid residues from the hypervariable E region of the capsid in the cultured viruses did not support the contention that properties of these residues can reliably differentiate between the two pathotypes. On plaque reduction assays, dose–response inhibition of FCV-VSD was obtained with all antivirals at low micromolar concentrations; NTZ EC₅₀, 0.4–0.6 µM, TI = 21; 2CMC EC₅₀, 2.7–5.3 µM, TI > 18; NITD-008, 0.5 to 0.9 µM, TI > 111. Investigation of these antivirals for the treatment of FCV-VSD is warranted.

Molecular Characterization and Cross-Reactivity of Feline Calicivirus Circulating in Southwestern China

Feline calicivirus (FCV) is an important pathogen of cats that has two genogroups (GI and GII). To investigate the prevalence and molecular characteristics of FCVs in southwestern China, 162 nasal swab samples were collected from cats in animal shelters and pet hospitals. In total, 38 of the clinical samples (23.46%) were identified as FCV positive using nested RT-PCR. Phylogenetic analyses using 10 capsid protein VP1 sequences revealed that 8 GI and 2 GII strains formed two independent clusters. Additionally, three separated FCVs that were not clustered phylogenetically (two GI and one GII strains) were successfully isolated from clinical samples and their full-length genomes were obtained. Phylogenetic and recombinant analyses of a GI FCV revealed genomic breakpoints in ORF1 and ORF2 regions with evidence for recombinant events between GI sub-genogroups, which is reported in China for the first time. Furthermore, sera obtained from mice immunized independently with the three FCV isolates and a commercial vaccine were used to evaluate the cross-reactivity of neutralizing antibodies. The three separate FCVs were neutralized by each other at a 1:19 to 1:775 titer range, whereas the triple-inactivated vaccine was at a titer of 1:16, which suggested that different genogroup/sub-genogroup FCV strains exhibit significantly different titers of neutralizing antibodies, including the commercial FCV vaccine. Thus, our study revealed the genetic diversity and complex cross-reactivity levels of FCVs in southwestern China, which provides new insights for application in vaccination strategies.

Feline calicivirus strain 2280 p30 antagonizes type I interferon-mediated antiviral innate immunity through directly degrading IFNAR1 mRNA

Feline calicivirus (FCV) belongs to the Caliciviridae, which comprises small RNA viruses of both medical and veterinary importance. Once infection has occurred, FCV can persist in the cat population, but the molecular mechanism of how it escapes the innate immune response is still unknown. In this study, we found FCV strain 2280 to be relatively resistant to treatment with IFN-β. FCV 2280 infection inhibited IFN-induced activation of the ISRE (Interferon-stimulated response element) promoter and transcription of ISGs (Interferon-stimulated genes). The mechanistic analysis showed that the expression of IFNAR1, but not IFNAR2, was markedly reduced in FCV 2280-infected cells by inducing the degradation of IFNAR1 mRNA, which inhibited the phosphorylation of downstream adaptors. Further, overexpression of the FCV 2280 nonstructural protein p30, but not p30 of the attenuated strain F9, downregulated the expression of IFNAR1 mRNA. His-p30 fusion proteins were produced in Escherichia coli and purified, and an in vitro digestion assay was performed. The results showed that 2280 His-p30 could directly degrade IFNAR1 RNA but not IFNAR2 RNA. Moreover, the 5’UTR of IFNAR1 mRNA renders it directly susceptible to cleavage by 2280 p30. Next, we constructed two chimeric viruses: rFCV 2280-F9 p30 and rFCV F9-2280 p30. Compared to infection with the parental virus, rFCV 2280-F9 p30 infection displayed attenuated activities in reducing the level of IFNAR1 and inhibiting the phosphorylation of STAT1 and STAT2, whereas rFCV F9-2280 p30 displayed enhanced activities. Animal experiments showed that the virulence of rFCV 2280-F9 p30 infection was attenuated but that the virulence of rFCV F9-2280 p30 was increased compared to that of the parental viruses. Collectively, these data show that FCV 2280 p30 could directly and selectively degrade IFNAR1 mRNA, thus blocking the type I interferon-induced activation of the JAK-STAT signalling pathway, which may contribute to the pathogenesis of FCV infection.

Vaccination against FCV has been available for many years and has effectively reduced the incidence of clinical disease. However, vaccines cannot prevent infection, and vaccinated cats can still become persistently infected by FCV, suggesting that FCV has evolved several strategies for counteracting various components of the innate and adaptive immune systems. Here, we show that FCV strain 2280 is resistant to the antiviral effect of IFN. The molecular mechanism by which this occurs is that FCV 2280 infection blocks the JAK-STAT pathway through promoting the degradation of IFNAR1 mRNA by FCV p30 protein. An in vitro degradation assay demonstrated that 2280 p30, but not p30 of the vaccine strain F9, could directly and selectively decay IFNAR1 RNA. The exchange of p30 between 2280 and F9 strains using a reverse genetic system also showed that 2280 p30 is a key factor that contributes to the resistance to IFN and enhances virulence. Our findings reveal a new mechanism evolved by FCV to circumvent the host antiviral response.

Identification of feline calicivirus in cats with enteritis

Feline calicivirus (FCV) is a major pathogen of cats associated with either respiratory disease or systemic disease, but its possible role as an enteric pathogen is neglected. Using RT-PCR, the RNA of FCV was identified in 25.9% (62/239) of stools of cats with enteritis and in 0/58 (0%) of cats without diarrhoea or other clinical signs. Isolates of enteric origin were obtained and a large 3.2-kb portion of the genome was sequenced, encompassing the 3' end of the RNA polymerase, the capsid protein precursor and the minor capsid protein. Also, the complete genome sequence of one such strain, the 160/2015/ITA, was determined. Upon sequence analysis, the enteric viruses were found to be genetically heterogeneous and to differ from each other and from isolates of respiratory origin. The enteric isolates were found to be more resistant to low pH conditions, to trypsin and to bile treatment than respiratory isolates. Overall, these findings are consistent with the hypothesis that some FCVs may acquire enteric tropism and eventually act as enteric pathogens. Whether this enteric tropism is maintained stably and whether it may affect, to some extent, the ability of the virus to trigger the classical and/or hypervirulent forms of disease should be assessed. Also, FCV should be included in the diagnostic algorithms of enteric diseases of cats to gain further information about FCV strains displaying enteric pathotype.

Precise location of linear epitopes on the capsid surface of feline calicivirus recognized by neutralizing and non-neutralizing monoclonal antibodies

We report the generation, characterization and epitope mapping of a panel of 26 monoclonal antibodies (MAbs) against the VP1 capsid protein of feline calicivirus (FCV). Two close but distinct linear epitopes were identified at the capsid outermost surface (P2 subdomain) of VP1, within the E5′HVR antigenic hypervariable region: one spanning amino acids 431-435 (PAGDY), highly conserved and recognized by non-neutralizing MAbs; and a second epitope spanning amino acids 445-451 (ITTANQY), highly variable and recognized by neutralizing MAbs. These antibodies might be valuable for diagnostic applications, as well as for further research in different aspects of the biology of FCV.

Multiple Correspondence Analysis on Amino Acid Properties within the Variable Region of the Capsid Protein Shows Differences between Classical and Virulent Systemic Feline Calicivirus Strains

Feline calicivirus (FCV) is a widespread and highly prevalent pathogen of domestic cats, responsible for mild upper respiratory tract disease. Outbreaks of severe virulent systemic disease (VSD) associated with FCV infection have been reported worldwide. VSD FCV strains have a broader tropism and cause a systemic vascular compromise. Despite clear differences in the pathogenesis of VSD and oral respiratory infections, attempts to identify specific molecular markers of VSD strains on the major capsid protein VP1 have failed. Region E of VP1 is responsible for the interaction with the cell receptor Junctional Adhesion Molecule JAM-1 (FeJAM-1) and with VP2 minor capsid protein during the entry of the virus. We carried out an original analysis on the sequences from region E of VSD and classical strains. A Multiple Correspondence Analysis was performed on a Boolean matrix built by coding sequences on the basis of their amino acid properties. For the first time, this approach was able to differentiate VSD and classical FCV. Seven remarkable residue positions were shown to be statistically significant for pathotype differentiation, mainly located in the N-terminal hypervariable part of region E. As structural analysis suggested an interaction of these residues with FeJAM-1 or VP2, post-binding events, and specific conformational changes may explain the difference of pathogenesis between pathotypes.

Cat flu: Broad spectrum polymeric antivirals

Feline herpesvirus type 1 (FHV-1) and feline calicivirus (FCV) are considered as main causes of feline upper respiratory tract disease and the most common clinical manifestations include rhinotracheitis, conjunctivitis, and nasal/facial ulcerations. While the primary infection is relatively mild, secondary infections pose a threat to young or immunocompromised cats and may result in a fatal outcome. In this study, we made an effort to evaluate antiviral potency of poly(sodium 4-styrenesulfonates) (PSSNa) as potent FHV-1 and FCV inhibitors for topical use. Mechanistic studies showed that PSSNa exhibits a different mechanism of action depending on target species. While PSSNa acts directly on FHV-1 particles blocking their interaction with the host's cell and preventing the infection, the antiviral potency against FCV is based on inhibition at late stages of the viral replication cycle. Altogether, PSSNa polymers are promising drug candidates to be used in the treatment and prevention of the viral upper respiratory tract disease (URTD), regardless of the cause.

Infection control practices employed within small animal veterinary practices-A systematic review

Effective infection control (IC) provides a safe environment for staff, clients and animals of veterinary practices by reducing the risk of nosocomial and zoonotic infections, which are associated with increased hospital stays, costs, morbidity and mortality. An equally important issue arising from nosocomial infection is the loss of trust between the client and the veterinary practice that has potential negative impacts on the veterinary practice in terms of economic risk and the well-being of staff. Furthermore, an emerging and significant threat, in this context, is antimicrobial resistance. The aim of this systematic review was to critically review published reports that documented current IC practices and evaluated interventions to improve IC practices. A systematic literature search using ten databases to identify papers published over a 20-year period (February 1996 to February 2016) was conducted for studies that met the inclusion criteria. Included studies were assessed using the PRISMA and STROBE-Vet statements. A total of 14 of 1,615 identified studies met our inclusion criteria. Infection control practices included hand hygiene, sharps handling, environmental cleaning, personal protective equipment and personnel vaccination. Descriptive studies were the predominant research design for assessing IC compliance. Only three studies were interventions. Compliance with IC protocols was poor and only marginally increased with multimodal educational campaigns. There was significant variation in the implementation of IC by veterinary staff. Workplaces that had IC policies, management support and a staff member supporting their implementation were more likely to embrace good IC. Infection control data in veterinary practices were inconsistently reported and collected. Clearly defining IC and determining prevalence of these practices within the veterinary field is important given the limited research in this area. Further, developing and implementing educational campaigns for this sector is needed.

Feline calicivirus infection in cats with virulent systemic disease, Italy

Feline calicivirus (FCV) is a contagious viral pathogen that usually causes a mild, self-limiting respiratory disease. More recently, highly virulent FCV strains have emerged and have been associated with severe systemic infection, referred to as virulent systemic disease (VSD). The objective of this study is to report VSD cases in Italian cats along with the molecular characterization of two detected FCV strains. Three client-owned cats showed clinical signs resembling to those described for VSD cases. The cats were subjected to molecular investigations for detection of FCV and other feline pathogens. Histopathology and immunohistochemistry were performed on internal organs of one cat; molecular characterization of two detected FCV strains was obtained through sequence and phylogenetic analyses. Putative VS-FCV strains were detected in all three cats, which were co-infected with feline panleukopenia virus. The cat submitted to histopathology and immunohistochemistry displayed severe histological changes and FCV antigens in internal organs. Two Italian FCV strains, for which amplification of ORF2 was successful, were strictly related and formed a unique phylogenetic cluster. These viruses did not show consistent changes in the amino acid sequences with respect to reference VS-FCVs. The results of our study confirm that VS-FCV strains are circulating in Italy and that VSD diagnosis is complicated since both genetic and clinical markers have not been identified so far.

Potential Therapeutic Agents for Feline Calicivirus Infection

Feline calicivirus (FCV) is a major cause of upper respiratory tract disease in cats, with widespread distribution in the feline population. Recently, virulent systemic diseases caused by FCV infection has been associated with mortality rates up to 50%. Currently, there are no direct-acting antivirals approved for the treatment of FCV infection. Here, we tested 15 compounds from different antiviral classes against FCV using in vitro protein and cell culture assays. After the expression of FCV protease-polymerase protein, we established two in vitro assays to assess the inhibitory activity of compounds directly against the FCV protease or polymerase. Using this recombinant enzyme, we identified quercetagetin and PPNDS as inhibitors of FCV polymerase activity (IC₅₀ values of 2.8 μM and 2.7 μM, respectively). We also demonstrate the inhibition of FCV protease activity by GC376 (IC₅₀ of 18 µM). Using cell culture assays, PPNDS, quercetagetin and GC376 did not display antivirals effects, however, we identified nitazoxanide and 2′-C-methylcytidine (2CMC) as potent inhibitors of FCV replication, with EC₅₀ values in the low micromolar range (0.6 μM and 2.5 μM, respectively). In conclusion, we established two in vitro assays that will accelerate the research for FCV antivirals and can be used for the high-throughput screening of direct-acting antivirals.

[Isolation and phylogenetic analysis of feline calicivirus in Siberia.]

The results of the study of the distribution of calicivirus infection in a population of domestic cats of different breeds, contained individually or the group method, the virus isolation in the cell culture and a comparative phylogenetic analysis of their nucleotide sequences with published sequences of reference feld and vaccine strains of Feline calicivirus (FCV) from other countries: USA, Germany, Japan, China and Korea are presented. Clinical signs of infection were found in 14.3% of the animals examined. After several passages in the primary kidney cells of the kitten embryo, seven cytopathogenic isolates FCV were isolated: 1 - from a cat with an acute infection, 5 - subclinical infection, 1 - systemic infection. They were adapted to continuous FK-81 cells in which they reached a maximum infectious activity of 10.0 ± 1.15 lg TCD 50 / cm3. Based on the sequence analysis of the open reading frame 2 region of the viral genome Eshli strain showed a close relationship with strain KM016908 from China with the identity of the nucleotide sequences between them of 81.0%. The results of the investigations showed that FCV isolates obtained from animals on the territory of Siberia are genetically different from strains included to imported vaccines used to prevent disease in Russian Federation and also among themselves. This causes a decrease in the effectiveness of preventive measures. In nurseries that do not have contacts and connections between themselves but located in the same geographic region FCV populations may have some genetic differences. A close relationship of some feld isolates with strains from other countries geographically located so far from the Siberian region has been revealed. Studies on the molecular epizootology of caliciviruses are important in the development of test systems and the monitoring of the spread of strains in Russia.

Relationship between Feline calicivirus Load, Oral Lesions, and Outcome in Feline Chronic Gingivostomatitis (Caudal Stomatitis): Retrospective Study in 104 Cats

Objective

This study was performed to assess the relationship between oral Feline calicivirus (FCV) load and severity of lesions at the time of presentation of cats suffering from feline chronic gingivostomatitis (FCGS) (part 1) and treatment outcome after dental extractions (part 2). We hypothesized that a higher FCV viral load would be positively correlated with the severity of lesions at presentation and negatively correlated with treatment outcome. In addition, the effect of dental extractions on outcome and the influence of preoperative severity of lesions on the outcome were investigated.

Materials and methods

Cats with FCGS were included in the study if they had been diagnosed with caudal stomatitis, had been tested positive for FCV using a real-time reverse transcriptase-PCR test on oropharyngeal swab, and had dental extractions performed within the authors’ department. General practitioners provided all previous medical treatments. Cats with recheck examinations were included in part 2 of the study. Multivariate statistical analysis was performed to assess the relationship between the different parameters.

Results

One hundred four cats met the requirements for part 1 and 56 cats for part 2 of the study. Data collected from patients’ record included patient history, viral testing results, extent and severity of oral lesions, extent of teeth extraction. Signalment, history, preoperative treatment, and severity of caudal and alveolar stomatitis score were not associated with FCV load (P > 0.05). Presence of lingual ulcers was significantly correlated with FCV load (P = 0.0325). Clinical cure (32.1%) or very significant improvement (19.6%) was achieved in 51.8% of cats within 38 days. Concomitantly, 60.7% of the owners considered their cat cured (41.1%) or significantly improved (19.6%). Extent of teeth extraction was not found to influence the clinical outcome (P > 0.05).

Conclusion

The results of this study did not support the hypothesis that FCV oral load is correlated with the severity of oral lesions or with the outcome following dental extractions. In addition, the severity of caudal inflammation was not correlated with healing time or achievement of cure.

Molecular detection of feline calicivirus in clinical samples: A study comparing its detection by RT-qPCR directly from swabs and after virus isolation

Feline caliciviruses (FCVs) are non-enveloped RNA viruses that exhibit high genetic variation. Two reverse transcription quantitative polymerase chain reaction (RT-qPCR) FCV assays (S1 and S2) were evaluated using samples from 300 field cats. The direct detection of FCV in swabs and after propagation in cell culture, as well as the influence of storage conditions, was assessed. FCV-RNA detectability on dry swabs was similar after storage at either 4°C or -20°C, but viral burdens were maintained for a longer time period when viral transport medium was used. A total of 97 (32%) samples was considered FCV PCR-positive. Of these, 81% and 77% tested positive directly from swabs using S1 and S2, respectively; 84% and 81% tested positive after enrichment in cell culture, respectively. Combined detection by RT-PCR directly from swabs and after VI was most sensitive (up to 96%). Neither of the methods alone were able to detect all FCV-positive samples. In conclusion, clinical samples should be collected in viral transport medium, stored at ≤4°C and processed as soon as possible. The combination of cell culture with RT-qPCR or detection directly from swabs using a combination of different RT-qPCR assays is recommended to reach a high sensitivity of FCV detection.

First report of Feline Calicivirus (FCV) infection in stray cats in northeast China

To improve our understanding of Feline calicivirus (FCV) infection in cats in Northeast China, 1584 serum samples from 974 domestic cats and 610 stray cats were collected between 2012 and 2015. The samples were tested for FCV antibodies using a commercially available ELISA kit. The results revealed an overall seroprevalence of 37.56% (595/1584), a seroprevalence in domestic cats of 32.85% (320/974) and a seroprevalence in stray cats of 45.08% (275/610). Risk factor analysis indicated that species was the only risk factor for the presence of FCV (OR=1.678, 95% CI=1.362-2.066, P<0.001); age, season, region and gender were not risk factors. This is the first report of FCV infection in stray cats in China, and the results of this study can aid in FCV infection control in the felidae family.

Intranasal immunization with inactivated feline calicivirus particles confers robust protection against homologous virus and suppression against heterologous virus in cats

The protective efficacy of intranasal (IN) administration of inactivated feline calicivirus (FCV) vaccine against homologous or heterologous FCV infection was investigated. Groups of cats immunized with the experimental inactivated, non-adjuvanted FCV vaccine via either the IN or subcutaneous (SC) route were exposed to homologous or highly heterologous FCV. Both the IN and SC immunization protocols established robust protection against homologous FCV infection. Although neither immunization regimen conferred protection against the heterologous strain, clinical scores and virus titres of oral swabs were lower in cats in the IN group compared to those in the SC group, accompanying a faster neutralizing antibody response against the heterologous virus in cats in the IN group. The IN group secreted more IgA specific to FCV proteins in oral washes (lavage fluids from the oral cavity) than the SC group. IN immunization with an inactivated whole FCV particle, which protects cats from homologous virus exposure and shortens the period of heterologous virus shedding, may serve as a better platform for anti-FCV vaccine.

Isolation and phylogenetic analysis of three feline calicivirus strains from domestic cats in Jilin Province, China

Feline calicivirus (FCV) is a highly prevalent pathogen that can cause infectious felid upper respiratory tract disease. The majority of complete genome sequences of FCV strains reported to date are from the USA. In this study, three FCV strains, CH-JL1, CH-JL2 and CH-JL3, were isolated from domestic cats in Jilin Province, China. Sequence analysis revealed that except for strains HRB-SS, WZ-1, XH, 12Q087-1 and 12Q087-5, the 3' untranslated regions (UTRs) of CH-JL2 and CH-JL3 are more than 20 nucleotides longer than those of all other reference isolates. The complete sequences of the three CH-JLs were compared with other reference strains, with nucleotide sequence identity values in the range of 76.2%-82.2%, 76.8%-96.4 and 76.8%-96.4%. Phylogenetic analysis showed that CH-JL1 forms a branch with FB-NJ-13, GD, 12Q087-1 and 12Q087-5. CH-JL2 was found to be most closely related to CH-JL3, forming another branch together with the other isolates. CH-JL1 shares a long nucleotide span with CH-JL2 and CH-JL3. It can be inferred that many FCV strains are co-circulating in Jilin Province. The availability of complete genome sequences will serve as a reference for future epidemiological studies of FCV.

Genetic diversity and phenotypic associations of feline caliciviruses from cats in Switzerland

Feline calicivirus (FCV) is a common viral pathogen in domestic cats worldwide. The variable regions of the capsid (VP1) gene of FCV have one of the highest recorded rates of molecular evolution. Understanding the genetic diversity and phylogeny of FCV is a prerequisite to exploring the epidemiology and pathogenesis of this virus and to the development of efficacious vaccine strategies. In this study, we undertook a nationwide molecular characterization of FCV using for the first time nearly complete capsid (VP1) gene sequences. Sequences from 66 FCV samples were used to investigate the correlation between viral phylogeny and several traits, including geographic origin, signalment, husbandry, FCV vaccination and co-infections. Codon-based nucleotide alignment showed that individual nucleotides and their corresponding amino acid sites were either invariant or highly variable. Using a threshold of 20 % genetic distance in variable region E, FCV samples were grouped into 52 strains, 10 of which comprised two to three samples. Significant associations between FCV phylogeny and host characteristics were found, specifically the pedigree status of the cats, and two well-supported lineages were identified in which the current FCV strain definition was confounded. No correlation between viral genetic distances and geographic distances was evident. The greater resolution of the FCV phylogeny in this study compared to previous studies can be attributed to our use of more conserved regions of the capsid (VP1) gene; nonetheless, our results were still hampered by sequence saturation. The study highlights the need for whole-genome sequences for FCV phylogeny studies.

Multi-drug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex infection outbreak in dogs and cats in a veterinary hospital

BACKGROUND

Members of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex cause severe outbreaks in humans, and are increasingly reported in animals.

OBJECTIVE AND METHODS

A retrospective study, describing a severe outbreak in dogs and cats caused by a multidrug resistant member of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex in a veterinary hospital, between July 2010 and November 2012.

RESULTS

The study included 19 dogs and 4 cats. Acinetobacter calcoaceticus-Acinetobacter baumannii complex bacteria were isolated from urine (9 animals), respiratory tract (11), tissues (3) and blood (1). The most common infection-associated findings included fever, purulent discharge from endotracheal tubes, hypotension, and neutropaenia. Infections led to pneumonia, urinary tract infection, cellulitis and sepsis. Infection was transmitted in the intensive care unit, where 22 of 23 animals were initially hospitalised. The mortality rate was 70% (16 of 23 animals), and was higher in cases of respiratory infection compared to other infections. Aggressive environmental cleaning and disinfection, with staff education for personal hygiene and antisepsis, sharply decreased the infection incidence.

CLINICAL SIGNIFICANCE

Health care-associated outbreaks with multidrug resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex in dogs and cats are potentially highly fatal and difficult to eradicate, warranting monitoring, antiseptic techniques and judicious antibiotic use.

Feline calicivirus and other respiratory pathogens in cats with Feline calicivirus-related symptoms and in clinically healthy cats in Switzerland

Background

Cats with feline calicivirus (FCV)-related symptoms are commonly presented to veterinary practitioners. Various clinical manifestations have been attributed to FCV, i.e. upper respiratory tract disease (URTD), oral ulcerations, gingivostomatitis, limping syndrome and virulent systemic disease. Additionally, healthy cats can shed FCV. The aims of this study were 1) to investigate the frequency of FCV in cats with FCV-related symptoms and in healthy cats in Switzerland, 2) to assess risk and protective factors for infection, such as signalment, housing conditions, vaccination, and co-infection with URTD-associated pathogens, and 3) to address the association between clinical symptoms and FCV infection.

Results

Oropharyngeal, nasal and conjunctival swabs were collected in 24 veterinary practices from 200 FCV-suspect and 100 healthy cats originating from 19 cantons of Switzerland. The samples were tested for FCV using virus isolation and reverse-transcription real-time quantitative polymerase chain reaction (qPCR) and for feline herpesvirus-1 (FHV-1), Mycoplasma felis, Chlamydophila felis, Bordetella bronchiseptica using real-time qPCR. Within the two populations (FCV-suspect/healthy), the observed PCR prevalences were: FCV 45 %/8 %, FHV-1 20 %/9 %, C. felis 8 %/1 %, B. bronchiseptica 4 %/2 %, M. felis 47 %/31 % and any co-infections thereof 40 %/14 %. Based on multivariable regression models amongst FCV-suspect cats (odds ratio [95 % confidence interval]), co-infection with M. felis (1.75 [0.97; 3.14]), group housing (2.11 [1.02; 4.34]) and intact reproductive status (1.80 [0.99; 3.28]) were found to be risk factors for FCV infection. In healthy cats, intact reproductive status (22.2 [1.85; 266.7]) and group housing (46.4 [5.70; 377.7]) were found to be associated with FCV infection. Based on an univariable approach, FCV-suspect cats were found to be significantly less often FCV-positive when vaccinated (0.48 [0.24; 0.94]). Oral ulcerations, salivation, gingivitis and stomatitis, but not classical signs of URTD were significantly associated with FCV infection (all p < 0.001).

Conclusions

FCV was detected in less than half of the cats that were judged FCV-suspect by veterinary practitioners. For a clinical diagnosis, FCV-related symptoms should be revisited. FCV infection was present in some healthy cats, underlining the importance of asymptomatic carriers in FCV epidemiology. To reduce FCV-related problems in multi-cat environments, reduction of group size in addition to the generally recommended vaccination are advocated.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0595-2) contains supplementary material, which is available to authorized users.

Nosocomial feline calicivirus-associated virulent systemic disease in a veterinary emergency and critical care unit in France

CASE SERIES SUMMARY

In October 2011, an abnormally large morbidity and mortality event was noted in the intensive care unit (ICU) of a veterinary school hospital in Nantes, France. Cats, and cats only, transferred from the emergency room presented with fever, ulcers on the tongue and cutaneous lesions around venepuncture or surgical incision sites, leading to suspicion of a feline calicivirus-associated virulent systemic disease confirmed with reverse transcriptase-polymerase chain reaction. A total of 14 cats were suspected. The clinical features and the origin of the contamination were described for each cat. The median length of incubation was 4.5 days. Fifty-seven percent of the cats were euthanased (8/14) and 21% died (3/14), with a combined mortality of 79% (11/14) - the highest ever reported. Median survival was 12 days. The recovery rate was 21% (3/14).

RELEVANCE AND NOVEL INFORMATION

Eight outbreaks have been reported, in veterinary clinics or in group-housed cats. The main unusual aspects of the present outbreak were: (1) the extreme flare-up of lesions at sites of skin breach, precluding any puncture/incision; (2) the suggested better survival rate at home than in hospital; and (3) the immediate control of the outbreak after recognition of the disease. Other striking but less unusual features of this outbreak were: (4) the increasing of the virulence of the calicivirus with the passage of time; and (5) the primary role that the caregivers' hands played in the spread of the outbreak.

Broad-spectrum inhibitors against 3C-like proteases of feline coronaviruses and feline caliciviruses

Feline infectious peritonitis and virulent, systemic calicivirus infection are caused by certain types of feline coronaviruses (FCoVs) and feline caliciviruses (FCVs), respectively, and are important infectious diseases with high fatality rates in members of the Felidae family. While FCoV and FCV belong to two distinct virus families, the Coronaviridae and the Caliciviridae, respectively, they share a dependence on viral 3C-like protease (3CLpro) for their replication. Since 3CLpro is functionally and structurally conserved among these viruses and essential for viral replication, 3CLpro is considered a potential target for the design of antiviral drugs with broad-spectrum activities against these distinct and highly important viral infections. However, small-molecule inhibitors against the 3CLpro enzymes of FCoV and FCV have not been previously identified. In this study, derivatives of peptidyl compounds targeting 3CLpro were synthesized and evaluated for their activities against FCoV and FCV. The structures of compounds that showed potent dual antiviral activities with a wide margin of safety were identified and are discussed. Furthermore, the in vivo efficacy of 3CLpro inhibitors was evaluated using a mouse model of coronavirus infection. Intraperitoneal administration of two 3CLpro inhibitors in mice infected with murine hepatitis virus A59, a hepatotropic coronavirus, resulted in significant reductions in virus titers and pathological lesions in the liver compared to the findings for the controls. These results suggest that the series of 3CLpro inhibitors described here may have the potential to be further developed as therapeutic agents against these important viruses in domestic and wild cats. This study provides important insights into the structure and function relationships of 3CLpro for the design of antiviral drugs with broader antiviral activities.

IMPORTANCE

Feline infectious peritonitis virus (FIPV) is the leading cause of death in young cats, and virulent, systemic feline calicivirus (vs-FCV) causes a highly fatal disease in cats for which no preventive or therapeutic measure is available. The genomes of these distinct viruses, which belong to different virus families, encode a structurally and functionally conserved 3C-like protease (3CLpro) which is a potential target for broad-spectrum antiviral drug development. However, no studies have previously reported a structural platform for the design of antiviral drugs with activities against these viruses or on the efficacy of 3CLpro inhibitors against coronavirus infection in experimental animals. In this study, we explored the structure-activity relationships of the derivatives of 3CLpro inhibitors and identified inhibitors with potent dual activities against these viruses. In addition, the efficacy of the 3CLpro inhibitors was demonstrated in mice infected with a murine coronavirus. Overall, our study provides the first insight into a structural platform for anti-FIPV and anti-FCV drug development.

Humoral response to calicivirus in captive tigers given a dual-strain vaccine

The current feline vaccine with a single strain of calicivirus has been used for captive tigers, yet it may not protect against virulent systemic calicivirus infections. A cross-institutional study investigated the humoral response to a new dual-strain, killed-virus calicivirus vaccine for nine captive tigers. The subspecies of these tigers were Amur (Panthera tigris altaica), Bengal (Panthera tigris tigris), and Malayan (Panthera tigris jacksoni). Serum neutralization titers for virulent feline calicivirus strain FCV-DD1 were higher following dual-strain vaccine administration. There were no reports of adverse vaccine reactions. Dual-strain vaccination may afford broadened cross-protection against different calicivirus strains and is desirable to reduce the risk of virulent systemic calicivirus disease in tigers.

Ocular manifestations of feline viral diseases

Feline viral diseases are common and cats can be presented with a variety of clinical manifestations. Ocular disease associated with viral pathogens is not unusual, particularly with viruses causing upper respiratory tract disease in cats, such as feline herpesvirus type 1 and feline calicivirus. These agents mainly cause ocular surface disease. Other viruses, such as feline immunodeficiency virus and feline coronavirus, can cause uveitis, while feline leukemia virus can induce ocular lymphosarcoma. This review covers the most common viral pathogens of cats that cause ocular manifestations, the specific features of the ocular diseases caused by these viruses and therapeutic recommendations.

Inactivation of coxsackievirus B4, feline calicivirus and herpes simplex virus type 1: unexpected virucidal effect of a disinfectant on a non-enveloped virus applied onto a surface

OBJECTIVE

To evaluate the effect of a disinfectant onto viruses in suspension on the one hand and applied onto a surface on the other.

METHODS

A system combining flocked swabs to recover viruses dried onto stainless steel carriers and gel filtration to eliminate cytotoxic products has been developed to study the virucidal effect of a quaternary ammonium-based disinfectant towards herpes simplex virus type 1 (HSV-1), coxsackievirus B4 (CVB4) and feline calicivirus F9 (FCV). The recovery of FCV has been estimated by RT real-time PCR.

RESULTS

HSV-1, CVB4 and FCV had a titer over 10(4) TCID50 · ml(-1) after 2 h drying and were recovered from the carriers using flocked swabs. HSV-1 was inactivated in suspension and on stainless steel carriers by the disinfectant (a reduction factor of 4 and 2.83 log, respectively) whereas CVB4 was resistant. The reduction of infectious titer was moderate, 1.5 log in 30 min, when FCV was in suspension, whereas it was up to 4 log in 10 min when the virus was dried on a carrier. Dried FCV was efficiently recovered from carriers as demonstrated by RT real-time PCR.

CONCLUSION

A non-enveloped virus, FCV, applied on a surface, but not in suspension, was inactivated by a quaternary ammonium-based disinfectant. The resistance of viruses applied onto a surface to the effect of disinfectants should be investigated further.

Virulent feline calicivirus disease in a shelter in Italy: a case description

Feline calicivirus (FCV) is a common pathogen of cats that is particularly widespread in multi-cat environments such as shelters and catteries. FCV infections are usually associated with acute, mild and self-limiting upper respiratory tract disease characterized by oral vesicles/ulcers. Recently, virulent systemic disease (VSD) associated with FCV infection has been reported in the USA and Europe. This paper describes a case of VSD affecting one adult, FIV infected cat ("Oscar") living in a shelter located in Northern Italy; the clinical, post-mortem and laboratory findings indicate that this is the first case of suspected FCV-VSD in this country. Similar to a previous report (Meyer et al., 2011), the disease affected only one cat, while others remained asymptomatic, despite their direct contact with "Oscar". Phylogenetic analysis identified unique features in the "Oscar" FCV isolate. The FIV infection of the patient might have favoured the generation of the virulent FCV strains in this cat.

Mechanisms, causes, investigation and management of vomiting disorders in cats: a literature review

Vomiting is a common presenting complaint in feline practice. This article differs from previous reviews in that it is an evidence-based review of the mechanisms, causes, investigation and management of vomiting in the domestic cat. Published evidence was reviewed, and then used to make recommendations for clinical assessment, diagnosis, antiemetic drug treatment, dietary management and monitoring of cats presenting with vomiting. The strength of the evidence on which recommendations are made (and areas where evidence is lacking for cats) has been highlighted throughout.

Large-scale spatial and temporal genetic diversity of feline calicivirus

Feline calicivirus (FCV) is an important pathogen of domestic cats and a frequently used model of human caliciviruses. Here we use an epidemiologically rigorous sampling framework to describe for the first time the phylodynamics of a calicivirus at regional and national scales. A large number of FCV strains cocirculated in the United Kingdom at the national and community levels, with no strain comprising more than 5% and 14% of these populations, respectively. The majority of strains exhibited a relatively restricted geographical range, with only two strains (one field virus and one vaccine virus) spreading further than 100 km. None of the field strains were identified outside the United Kingdom. Temporally, while some strains persisted locally for the majority of the study, others may have become locally extinct. Evolutionary analysis revealed a radial phylogeny with little bootstrap support for nodes above the strain level. In most cases, spatially and temporally diverse strains intermingled in the phylogeny. Together, these data suggest that current FCV evolution is not associated with selective competition among strains. Rather, the genetic and antigenic landscape in each geographical location is highly complex, with many strains cocirculating. These variants likely exist at the community level by a combination of de novo evolution and occasional gene flow from the wider national population. This complexity provides a benchmark, for the first time, against which vaccine cross-protection at both local and national levels can be judged.

Comparative efficacy of a recombinant feline interferon omega in refractory cases of calicivirus-positive cats with caudal stomatitis: a randomised, multi-centre, controlled, double-blind study in 39 cats

Chronic caudal stomatitis with alveolar/buccal mucositis in calicivirus-positive cats is the most severe presentation of feline chronic gingivostomatitis. Refractory cases are helped by antibiotic and anti-inflammatory treatments often including glucocorticoids. In order to evaluate the comparative efficacy of oromucosal administration of recombinant feline interferon omega (rFeIFN-ω) versus oral administration of glucocorticoids, a randomised, multi-centre, controlled, double-blind study was performed in 39 cats. The progression of behavioural, clinical and lesional scores was assessed over 90 days. Daily oromucosal treatment with 0.1 MU of rFeIFN-ω was associated with a significant improvement of clinical lesions (caudal stomatitis and alveolar/buccal mucositis) and a decrease of pain scores from D0 to D90. Although no such statistical improvement was noticed in the prednisolone group, there was, however, no significant difference between the two groups for most of the parameters, except pain at D60 and D90.