Feline herpesvirus

Presumed calcific band keratopathy in a 10-month-old domestic shorthair cat

OBJECTIVE

To describe a case of presumed band keratopathy in a young cat with no known history of corneal disease who was not receiving topical phosphate-based steroids.

ANIMAL STUDIED

A 10-month-old domestic shorthair cat was evaluated for severe ocular discomfort that did not improve despite the initiation of topical antibiotic treatment.

METHODS

A complete ophthalmic examination and ancillary tests such as biomicroscopy and corneal cytology were performed at the time of presentation. A superficial lamellar keratectomy was excised, and the corneal button was sent for histopathology. In addition to routine hematoxylin-eosin staining, sections were stained with Gram, PAS, von Kossa, and trichrome stains.

RESULTS

Biomicroscopic examination revealed an extensive corneal epithelial ulcer with a hard white plaque in the central area of the right cornea with associated superficial neovascularization. Ultrasound biomicroscopy showed a 0.63 mm, slightly hyperechoic band in the anterior corneal stroma. Corneal cytology evidenced numerous neutrophils with toxic changes and few macrophages. Histopathologic analysis excluded corneal sequestration as a differential diagnosis and confirmed superficial corneal mineralization. At the last follow-up, 16 months after surgery, corneal transparency had returned, and visual acuity was good with some corneal conjunctivalization.

CONCLUSIONS

In this case report, the presumptive diagnosis is calcific band keratopathy. To the best of the author's knowledge, this is the first presumed case in a cat not receiving topical phosphate-based steroids and without previous corneal damage. Lamellar keratectomy represents a curative approach that successfully resolved the clinical signs, with no reported recurrence.

Construction and in vitro characterisation of virus-vectored immunocontraceptive candidates derived from felid alphaherpesvirus 1

There is a pressing need for effective feral cat management globally due to overabundant feline populations, disease transmission and their destructive impact on biodiversity. Virus-vectored immunocontraception (VVIC) is an attractive method for cat population management. Virus-vectored immunocontraceptives could be self-disseminating through horizontal transmission of the VVIC in feral cat populations, or they may be modified to act as non-transmissible vaccine-type immunocontraceptives for delivery to individual cats. These later constructs may be particularly attractive for use in owned (pet) cats and stray cats but could also be used for feral cats that are caught, vaccinated, and released. Here, we report the construction of three felid alphaherpesvirus 1 (FHV-1) derived immunocontraceptive candidates containing genes that encode for feline zona pellucida subunit 3 (ZP3) and gonadotropin-releasing hormone (GnRH). Two of the vaccine candidates were engineered to include disruptions to the thymidine kinase viral virulence gene to reduce the ability of the vaccines to be horizontally transmitted. Analysis of in vitro growth characteristics and protein expression are reported, and their potential for use as a population management tool for cats is discussed.

The Latest Prevalence, Isolation, and Molecular Characteristics of Feline Herpesvirus Type 1 in Yanji City, China

Epidemiological surveys revealed that 33 of the 93 samples were positive for FHV-1, with the gD gene of these 33 samples exhibiting low variation, high homology, and no critical amino acid mutation. Feline herpesvirus type 1 (FHV-1), also known as feline viral rhinotracheitis (FVR) virus, is one of the main causes of URT disease in cats. All cats can become hosts of FHV-1, and the spread of this disease affects the protection of rare feline animals. Nasal swabs from cats with URT disease were collected at five veterinary clinics in Yanji City from 2022 to 2024. The purpose of this study was to isolate and investigate the epidemiology of FHV-1. The gD gene of the FHV-1 strain was cloned and inserted into the pMD-18T vector and transformed into a competent Escherichia coli strain. Subsequently, the gD gene of the positive samples was sequenced and phylogenetic analysis was performed to determine the genetic evolution relationship between the strains. We successfully isolated the FHV-1 strain YBYJ-1 in Yanji City for the first time. The diameter of the virus is approximately 150-160 nm. After 48 h of virus inoculation, the cells were round, isolated, and formed grape-like clusters. The gD gene of the virus was sequenced, and the length was 1125 bp, which proved the isolate was FHV-1. This study found that the genetic evolution of the FHV-1 gD gene was stable, expanding the molecular epidemiological data on FHV-1 in cats in Yanji City.

Green tea extract reduces viral proliferation and ROS production during Feline Herpesvirus type-1 (FHV-1) infection

BACKGROUND

Feline Herpesvirus type-1 (FHV-1) is a worldwide spread pathogen responsible for viral rhinotracheitis and conjunctivitis in cats that, in the most severe cases, can lead to death. Despite the availability of a variety of antiviral medications to treat this illness, mainly characterized by virostatic drugs that alter DNA replication, their use is often debated. Phytotherapeutic treatments are a little-explored field for FHV-1 infections and reactivations. In this scenario, natural compounds could provide several advantages, such as reduced side effects, less resistance and low toxicity. The purpose of this study was to explore the potential inhibitory effects of the green tea extract (GTE), consisting of 50% of polyphenols, on FHV-1 infection and reactive oxygen species (ROS) production.

RESULTS

Crandell-Reese feline kidney (CRFK) cells were treated with different doses of GTE (10-400 µg/mL) during the viral adsorption and throughout the following 24 h. The MTT and TCID50 assays were performed to determine the cytotoxicity and the EC50 of the extract, determining the amounts of GTE used for the subsequent investigations. The western blot assay showed a drastic reduction in the expression of viral glycoproteins (i.e., gB and gI) after GTE treatment. GTE induced not only a suppression in viral proliferation but also in the phosphorylation of Akt protein, generally involved in viral entry. Moreover, the increase in cell proliferation observed in infected cells upon GTE addition was supported by enhanced expression of Bcl-2 and Bcl-xL anti-apoptotic proteins. Finally, GTE antioxidant activity was evaluated by dichloro-dihydro-fluorescein diacetate (DCFH-DA) and total antioxidant capacity (TAC) assays. The ROS burst observed during FHV-1 infection was mitigated after GTE treatment, leading to a reduction in the oxidative imbalance.

CONCLUSIONS

Although further clinical trials are necessary, this study demonstrated that the GTE could potentially serve as natural inhibitor of FHV-1 proliferation, by reducing viral entry. Moreover, it is plausible that the extract could inhibit apoptosis by modulating the intrinsic pathway, thus affecting ROS production.

Evaluation of feline mesenchymal stem cell susceptibility to feline viruses

Feline mesenchymal stem cells (fMSCs) are well known for their robust differentiation capabilities and are commonly used in studying immune-related diseases in cats. Despite their importance, the susceptibility of fMSCs to viral infections remains uncertain. This study aimed to assess the susceptibility of feline adipose-derived mesenchymal stem cells (fAD-MSCs) and feline umbilical cord-derived mesenchymal stem cells (fUC-MSCs) to common feline viruses, including feline coronavirus (FCoV), feline herpesvirus type 1 (FHV-1), and feline panleukopenia virus (FPV). The results demonstrated that both FCoV and FHV-1 were able to infect both types of cells, while FPV did not exhibit cytopathic effects on fUC-MSCs. Furthermore, all three viruses were successfully isolated from fAD-MSCs. These findings suggest that certain feline viruses can replicate in fMSCs, indicating potential limitations in using fMSCs for treating viral diseases caused by these specific viruses. This study has important clinical implications for veterinarians, particularly in the management of viral diseases.

Detection of Mycoplasma spp. and feline calicivirus in cats with ocular surface disease

OBJECTIVE

To survey the prevalence of pathogens in shelter-housed cats with active ocular surface disease (OSD).

ANIMALS STUDIED

A total of 255 shelter-housed domestic cats with evidence of active OSD. No normal, unaffected cats were sampled.

PROCEDURE(S)

OSD scoring was performed on cats with active OSD. Combined oropharyngeal/conjunctival swabs were submitted for rt-PCR/PCR for feline herpesvirus (FHV-1), feline calicivirus (FCV), Chlamydia spp. (CHL), Bordetella bronchiseptica (BORD), and Mycoplasma spp. (MYC).

RESULTS

Pathogens were detected as follows: 76.4% (195/255) MYC, 57.6% (147/255) FHV-1, 42.7% (109/255) FCV, 26.7% (68/255) CHL, and 5.5% (14/255) BORD. Monoinfections affected 21.1% (54/255) animals, with MYC being the most common monoinfection (12.5%, 32/255), followed by FHV-1 (4.7%, 12/255), followed by CHL (2.4%, 6/255), followed by FCV (1.6%, 4/255), with no animals having a BORD monoinfection. Dual infections affected 36.4% of animals (93/255), with MYC detected in 30.1% (77/255) dual infections and FCV detected in 12.9% (33/255) dual infections. Dual infections with MYC and FCV together were detected in 9.8% (25/255) animals. Many animals (35.3%, 90/255) were found to be affected by 3 or more pathogens, and 7.1% (18/255) animals had no pathogens detected. OSD scores were not influenced by any variable assessed, including the number and type of pathogens detected.

CONCLUSION

MYC, FHV-1, FCV, and CHL were commonly detected in this group of animals with OSD. Both MYC and FCV (alone or in combination with each other) were detected in multiple animals with active OSD, supporting prior evidence that either may independently act as a primary ocular surface pathogen.

Identification, Genetic Characterization, and Pathogenicity of Three Feline Herpesvirus Type 1 Isolates from Domestic Cats in China

(1) Background: Feline herpesvirus (FHV-1) is a significant pathogen in cats, causing respiratory and ocular diseases with consequential economic and welfare implications. (2) Methods: This study aimed to isolate and characterize FHV-1 from clinical samples and assess its pathogenicity. We collected 35 nasal and ocular swabs from cats showing symptoms of upper respiratory tract infection and FHV positivity detected by polymerase chain reaction (PCR). Viral isolation was carried out using feline kidney (F81) cell lines. Confirmation of FHV-1 presence was achieved through PCR detection, sequencing, electron microscopy, and indirect immunofluorescence assay. The isolated strains were further characterized by evaluating their titers, growth kinetics, and genetic characteristics. Additionally, we assessed the pathogenicity of the isolated strains in a feline model, monitoring clinical signs, viral shedding, and histopathological changes. (3) Results: Three strains of FHV-1 were isolated, purified, and identified. The isolated FHV-1 strains exhibited high homology among themselves and with domestic isolates and FHV-1 viruses from around the world. However, they showed varying degrees of virulence, with one strain (FHV-A1) causing severe clinical signs and histopathological lesions. (4) Conclusion: This study advances our understanding of the genetic and pathogenic characteristics of FHV-1 in China. These findings underscore FHV-A1 isolate as a potentially ideal candidate for establishing a challenge model and as a potential vaccine strain for vaccine development.

Advances in the immunoescape mechanisms exploited by alphaherpesviruses

Alphaherpesviruses, categorized as viruses with linear DNA composed of two complementary strands, can potentially to induce diseases in both humans and animals as pathogens. Mature viral particles comprise of a core, capsid, tegument, and envelope. While herpesvirus infection can elicit robust immune and inflammatory reactions in the host, its persistence stems from its prolonged interaction with the host, fostering a diverse array of immunoescape mechanisms. In recent years, significant advancements have been achieved in comprehending the immunoescape tactics employed by alphaherpesviruses, including pseudorabies virus (PRV), herpes simplex virus (HSV), varicella-zoster virus (VZV), feline herpesvirus (FeHV), equine herpesvirus (EHV), and caprine herpesvirus type I (CpHV-1). Researchers have unveiled the intricate adaptive mechanisms existing between viruses and their natural hosts. This review endeavors to illuminate the research advancements concerning the immunoescape mechanisms of alphaherpesviruses by delineating the pertinent proteins and genes involved in virus immunity. It aims to furnish valuable insights for further research on related mechanisms and vaccine development, ultimately contributing to virus control and containment efforts.

First report of molecular epidemiology and phylogenetic characteristics of feline herpesvirus (FHV-1) from naturally infected cats in Kunshan, China

BACKGROUND

Feline herpesvirus type 1 (FHV-1) is a life threatening highly contagious virus in cats and typically causes upper respiratory tract infections as well as conjunctival and corneal ulcers. Genetic variability could alter the severity of diseases and clinical signs. Despite regular vaccine practices against FHV-1 in China, new FHV-1 cases still commonly occur. The genetic and phylogenetic characteristics of FHV-1 in Kunshan city of China has not been studied yet. Therefore, this study was planned to investigate the prevalence, molecular characteristics of circulating strains, and phylogenetic analyses of FHV-1. This is the first report of molecular epidemiology and phylogenetic characteristics of FHV-1 from naturally infected cats in Kunshan, China.

METHODS

The occulo-nasal swabs were collected from diseased cats showing respiratory distress, conjunctivitis, and corneal ulcers at different veterinary clinics in Kunshan from 2022 to 2023. Clinical data and general information were recorded. Swab samples were processed for preliminary detection of FHV-1. Thymidine kinase (TK), glycoprotein B (gB) and glycoprotein D (gD) genes were sequenced and analyzed to investigate genetic diversity and evolution of FHV-1.

RESULTS

The FHV-1 genome was detected in 43 (43/200, 21.5%) samples using RT-PCR targeting the TK gene. Statistical analysis showed a significant correlation between age, vaccination status and living environment (p < 0.05) with FHV-1 positivity, while a non-significant correlation was observed for FHV-1 positivity and sex of cats (p > 0.05). Additionally, eight FHV-1 positive cats were co-infected with feline calicivirus (8/43,18.6%). FHV-1 identified in the present study was confirmed as FHV-1 based on phylogenetic analyses. The sequence analyses revealed that 43 FHV-1 strains identified in the present study did not differ much with reference strains within China and worldwide. A nucleotide homology of 99-100% was determined among gB, TK and gD genes nucleotide sequences when compared with standard strain C-27 and vaccine strains. Amino acid analysis showed some amino acid substitutions in TK, gB and gD protein sequences. A potential N-linked glycosylation site was observed in all TK protein sequences. Phylogenetic analyses revealed minor variations and short evolutionary distance among FHV-1 strains detected in this study.

CONCLUSIONS

Our findings indicate that genomes of 43 FHV-1 strains are highly homogenous and antigenically similar, and the degree of variation in major envelope proteins between strains is low. This study demonstrated some useful data about prevalence, genetic characteristics, and evolution of FHV-1 in Kunshan, which may aid in future vaccine development.

Immunogenicity evaluation of a bivalent vaccine based on a recombinant rabies virus expressing gB protein of FHV-1 in mice and cats

Feline viral rhinotracheitis (FVR) is caused by the feline herpesvirus-1 (FHV-1), which commonly results in upper respiratory symptoms, and can result in death in the kittens and weak cats. Rabies is an infectious disease with zoonotic characteristics highly relevant to public health and also poses a serious threat to cats. Vaccines are the most effective method to control the spread of both FHV-1 and RABV and have the advantage that they produce long-term specific immune responses. In this study, we constructed a bivalent vaccine against FHV-1 and rabies virus (RABV) simultaneously. The vaccine was constructed by cloning FHV-1 gB into a RABV based vector, and the recombinant RABV (SRV9-FHV-gB) expressing the FHV-1 gB protein was rescued. The growth characteristics of SRV9-FHV-gB were analyzed on NA and BSR cells. To assess the immunogenicity of the vaccine, mice and cats were immunized with SRV9-FHV-gB supplemented with Gel02 adjuvant. The SRV9-FHV-gB exhibited the same growth characteristics as the parent virus SRV9 in both BSR cells and NA cells. The safety of SRV9-FHV-gB was evaluated using 5-day-old and 14-day-old suckling mice. The results showed that mice infected with the SRV9-FHV-gB survived for longer than those in the SRV9 group. Mice immunized with inactivated SRV9-FHV-gB produced high titers of specific antibodies against FHV-1 and neutralizing antibodies against RABV. Cats that received three immunizations with SRV9-FHV-gB also produced neutralizing antibodies against both FHV-1 and RABV. This study represents the first time that a bivalent vaccine targeting FHV-1 and RABV has been constructed, laying the foundations and providing inspiration for the development of other multivalent vaccines.

A potential dual protection vaccine: Recombinant feline herpesvirus-1 expressing feline parvovirus VP2 antigen

Recently, herpesvirus viral vectors that stimulate strong humoral and cellular immunity have been demonstrated to be the most promising platforms for the development of multivalent vaccines, because they contain various nonessential genes and exhibit long-life latency characteristics. Previously, we showed that the feline herpesvirus-1 (FHV-1) mutant WH2020-ΔTK/gI/gE, which was safe for felines and provided efficacious protection against FHV-1 challenge, can be used as a vaccine vector. Moreover, previous studies have shown that the major neutralizing epitope VP2 protein of feline parvovirus (FPV) can elicit high levels of neutralizing antibodies. Therefore, to develop a bivalent vaccine against FPV and FHV-1, we first generated a novel recombinant virus by CRISPR/Cas9-mediated homologous recombination, WH2020-ΔTK/gI/gE-VP2, which expresses the VP2 protein of FPV. The growth characteristics of WH2020-ΔTK/gI/gE-VP2 were similar to those of WH2020-ΔTK/gI/gE, and WH2020-ΔTK/gI/gE-VP2 was stable for at least 30 generations in CRFK cells. As expected, we found that the felines immunized with WH2020-ΔTK/gI/gE-VP2 produced FPV-neutralizing antibody titers (27.5) above the positive cutoff (26) on day 14 after single inoculation. More importantly, recombinant WH2020-ΔTK/gI/gE-VP2 exhibited severely impaired pathogenicity in inoculated and cohabiting cats. The kittens immunized with WH2020-ΔTK/gI/gE and WH2020-ΔTK/gI/gE-VP2 produced similar levels of FHV-specific antibodies and IFN-β. Furthermore, felines immunized with WH2020-ΔTK/gI/gE-VP2 were protected against challenge with FPV and FHV-1. These data showed that WH2020-ΔTK/gI/gE-VP2 appears to be a potentially safe, effective, and economical bivalent vaccine against FPV and FHV-1 and that WH2020-ΔTK/gI/gE can be used as a viral vector to develop feline multivalent vaccines.

Saikosaponin B2, Punicalin, and Punicalagin in Vitro Block Cellular Entry of Feline Herpesvirus-1

In the realm of clinical practice, nucleoside analogs are the prevailing antiviral drugs employed to combat feline herpesvirus-1 (FHV-1) infections. However, these drugs, initially formulated for herpes simplex virus (HSV) infections, operate through a singular mechanism and are susceptible to the emergence of drug resistance. These challenges underscore the imperative to innovate and develop alternative antiviral medications featuring unique mechanisms of action, such as viral entry inhibitors. This research endeavors to address this pressing need. Utilizing Bio-layer interferometry (BLI), we meticulously screened drugs to identify natural compounds exhibiting high binding affinity for the herpesvirus functional protein envelope glycoprotein B (gB). The selected drugs underwent a rigorous assessment to gauge their antiviral activity against feline herpesvirus-1 (FHV-1) and to elucidate their mode of action. Our findings unequivocally demonstrated that Saikosaponin B2, Punicalin, and Punicalagin displayed robust antiviral efficacy against FHV-1 at concentrations devoid of cytotoxicity. Specifically, these compounds, Saikosaponin B2, Punicalin, and Punicalagin, are effective in exerting their antiviral effects in the early stages of viral infection without compromising the integrity of the viral particle. Considering the potency and efficacy exhibited by Saikosaponin B2, Punicalin, and Punicalagin in impeding the early entry of FHV-1, it is foreseeable that their chemical structures will be further explored and developed as promising antiviral agents against FHV-1 infection.

Feline herpesvirus-1-related multiple respiratory eosinophilic nodules in an adult cat receiving long-term oral prednisolone

Case summary

A 10-year-old male castrated domestic shorthair cat was presented for evaluation of a 3-day history of increased inspiratory effort. The cat had received prednisolone 1 mg/kg PO q24h for 1 year due to chronic diarrhea. On physical examination, the patient exhibited severe stridor, intermittent open-mouth breathing and bilateral mucopurulent nasal discharge. Subcutaneous emphysema was palpated over the dorsal cervical region. Mild hypoventilation (PvCO2 55.1 mmHg; approximate reference interval 35-45 mmHg) was identified. Cervicothoracic radiographs showed marked gas tracking within cervical soft tissues with concurrent laryngeal thickening, pulmonary nodules, a bronchial pulmonary pattern, pneumomediastinum and aerophagia. The cat was hospitalized and treated overnight with oxygen and intravenous fluid therapy before anesthesia the next day. On laryngoscopy, a large tracheal mass was observed arising from the right subglottic region and was removed using biopsy forceps. CT revealed an additional mass at the level of the tracheal bifurcation causing marked luminal narrowing of the trachea and proximal main bronchi. The cat made a good initial recovery, although moderate stridor persisted. Five days later, the cat was re-examined due to recurrence of respiratory distress and orthopnea, and the owner elected euthanasia. Histopathology revealed severe nodular obstructive eosinophilic plasmacytic laryngotracheitis with intranuclear inclusion bodies positive for feline herpesvirus-1 on immunohistochemistry.

Relevance and novel information

This report describes the presentation and management of a cat with respiratory distress secondary to intratracheal eosinophilic masses caused by feline herpesvirus-1. Although the outcome was ultimately unsatisfactory, to the authors' knowledge, this clinical presentation has not been previously reported.

Frequency of feline herpesvirus 1 (FHV-1) in domestic cats from Campo Grande, MS, Brazil

Feline herpesvirus type 1 (HVF-1) is the infectious agent of feline viral rhinotracheitis. The main clinical signs are cough, nasal and eye discharge, fever, conjunctivitis and sneezing. Although the occurrence of the virus is known in some regions of Brazil, in Campo Grande, Mato Grosso do Sul (MS), there is no epidemiological information about its frequency. Thus, this study aimed to determine the frequency of feline herpesvirus type 1 in the region, and to evaluate its possible association with clinical and epidemiological factors. Ocular, nasal and oropharyngeal swabs, and blood were collected from 152 animals and analyzed through PCR and sequencing. In addition, epidemiological and clinical data were obtained through clinical examination and anamnesis. FHV-1 was detected in samples from 84 (55.26%) animals. There was no association between infection and age or sex. However, there was a significant association between infection and nasal (p < 0.0001) and ocular (p = 0.014) discharge and sneezing (p = 0.001). The results demonstrate the occurrence of the virus in domestic cats in the region with a high frequency of infection. Thus, FHV-1 should be considered as a potential causal agent of upper respiratory tract disease in domestic cats from Campo Grande, MS, Brazil.

A bacterium-like particle vaccine displaying protective feline herpesvirus 1 antigens can induce an immune response in mice and cats

Feline herpesvirus 1 (FHV-1) is a highly transmissible virus that mainly causes ocular and upper respiratory infections in cats and seriously threatens the health of domestic cats and captive or wild cats (such as tigers, cheetahs, and lions). Vaccination is crucial to reduce the incidence rate and mortality of cats infected with FHV-1. In this study, three bacterium-like particles (BLPs) displaying the gB, gC, and gD proteins of FHV-1 were constructed based on a gram-positive enhancer matrix-protein anchor (GEM-PA) surface display system. Indirect immunofluorescence assay, western blot, and electron microscopy results showed that gB, gC or gD protein of FHV-1 was successfully displayed on the surface of GEM particles. Additionally, we designed one more BLPs, designated gB&gC&gD-GEM, which consisted of a mixture of gB-GEM, gC-GEM, and gD-GEM at a protein content ratio of 1:1:1. Mice were immunized with the four BLPs mixed with Gel02 adjuvant, and the results indicated that neutralizing antibody level in the gB&gC&gD-GEM group was superior than those in the other groups. Moreover, gB&gC&gD-GEM significantly increased the secretion of cytokines, as well as the activation and maturation of B cells. It also boosted the production of central memory T cells among CD4 + and CD8 + T cells. Moreover, gB&gC&gD-GEM mixed with Gel02 adjuvant provoked an antibody response in cats. In conclusion, the BLPs vaccine prepared from gB&gC&gD-GEM induced specific humoral and cellular immune responses to FHV-1 and be used as a potential vaccine candidate for the control of FHV-1 infection in cats.

Autophagy up-regulation upon FeHV-1 infection on permissive cells

FeHV-1 is a member of the Herpesviridae family that is distributed worldwide and causes feline viral rhinotracheitis (FVR). Since its relationship with the autophagic process has not yet been elucidated, the aim of this work was to evaluate the autophagy mediated by FeHV-1 and to determine its proviral or antiviral role. Our data showed that autophagy is induced by FeHV-1 in a viral dose and time-dependent manner. Phenotypic changes in LC3/p62 axis (increase of LC3-II and degradation of p62) were detected from 12 h post infection using western blot and immuno-fluorescence assays. In a second step, by using late autophagy inhibitors and inducers, the possible proviral role of autophagy during FeHV-1 infection was investigating by assessing the effects of each chemical in terms of viral yield, cytotoxic effects, and expression of viral glycoproteins. Our findings suggest that late-stage autophagy inhibitors (bafilomycin and chloroquine) have a negative impact on viral replication. Interestingly, we observed an accumulation of gB, a viral protein, when cells were pretreated with bafilomycin, whereas the opposite effect was observed when an autophagy inducer was used. The importance of autophagy during FeHV-1 infection was further supported by the results obtained with ATG5 siRNA. In summary, this study demonstrates FeHV-1-mediated autophagy induction, its proviral role, and the negative impact of late autophagy inhibitors on viral replication.

Safety and immunogenicity of a TK/ gI/gE gene-deleted feline herpesvirus-1 mutant constructed via CRISPR/Cas9 in feline

Feline herpesvirus-1 (FHV-1) is the aetiological agent of feline viral rhinotracheitis, which accounts for approximately 50 % of all viral upper respiratory diseases in cats. Commercially available modified live vaccines containing FHV-1 are generally safe and effective, but these FHV-1 vaccines retain full virulence genes and can establish latency and reactivate to cause infectious rhinotracheitis in vaccine recipients, raising safety concerns. To address this shortcoming, we constructed a novel TK/gI/gE -gene-deleted recombinant FHV-1 (WH2020-ΔTK/gI/gE) through CRISPR/Cas9-mediated homologous recombination. The growth kinetics of WH2020-ΔTK/gI/gE were slightly delayed compared to those of the parent strain WH2020. Recombinant FHV-1 had severely impaired pathogenicity in cats. Felines immunized with WH2020-ΔTK/gI/gE produced high levels of gB-specific antibodies, neutralizing antibodies and IFN-β. Additionally, WH2020-ΔTK/gI/gE provided greater protection against challenge with FHV-1 field strain WH2020 than did the commercial modified live vaccine. After challenge, the cats vaccinated with WH2020-ΔTK/gI/gE showed significantly fewer clinical signs, pathological changes, viral shedding, and viral loads in the lung and trigeminal ganglia than those vaccinated with the commercial vaccine or unvaccinated. Our results suggest that WH2020-ΔTK/gI/gE is a promising candidate as a safer and more efficacious live FHV-1 vaccine, with a decreased risk of vaccine-related complications, and could inform the design of other herpesvirus vaccines.

Surveillance for feline herpesvirus type 1 mutation and development of resistance in cats treated with antiviral medications

Feline herpesvirus type 1 (FHV-1) commonly causes ocular surface disease in cats and is treated with antiviral medications targeting viral DNA polymerase (UL30/42). Herein, we describe a method to assess the FHV-1 genome for mutation development and to assess the functional impact of mutations, if present. Fourteen shelter-housed domestic cats with FHV-1 ocular surface disease were assigned to one of four treatment groups: placebo (n = 3), cidofovir 0.5% ophthalmic solution (n = 3), famciclovir oral solution (n = 5), or ganciclovir 0.15% ophthalmic solution (n = 3). Swabs were collected before (day 1) and after (day 8) 1 week of twice-daily treatments to isolate viable FHV-1. Viral DNA was extracted for sequencing using Illumina MiSeq with subsequent genomic variant detection between paired day 1 and day 8 isolates. Plaque reduction assay was performed on paired isolates demonstrating non-synonymous variants. A total of 171 synonymous and 3 non-synonymous variants were identified in day 8 isolates. No variants were detected in viral UL23, UL30, or UL42 genes. Variant totals were not statistically different in animals receiving antiviral or placebo (p = 0.4997). A day 8 isolate from each antiviral treatment group contained a single non-synonymous variant in ICP4 (transcriptional regulator). These 3 isolates demonstrated no evidence of functional antiviral resistance when IC₅₀ was assessed. Most (10/14 pairs) day 1 and 8 viral isolate pairs from the same host animal were near-identical. While functional variants were not detected in this small sample, these techniques can be replicated to assess FHV-1 isolates suspected of having developed resistance to antiviral medications.

Pathogenicity and immunogenicity of gI/gE/TK-gene-deleted Felid herpesvirus 1 variants in cats

BACKGROUND

Felid herpesvirus 1 (FHV-1) is a major pathogenic agent of upper respiratory tract infections and eye damage in felines worldwide. Current FHV-1 vaccines offer limited protection of short duration, and therefore, do not reduce the development of clinical signs or the latency of FHV-1.

METHODS

To address these shortcomings, we constructed FHV ∆gIgE-eGFP, FHV ∆TK mCherry, and FHV ∆gIgE/TK eGFP-mCherry deletion mutants (ΔgI/gE, ΔTK, and ΔgIgE/TK, respectively) using the clustered regularly interspaced palindromic repeats (CRISPR)/CRISP-associated protein 9 (Cas9) system (CRISPR/Cas9), which showed safety and immunogenicity in vitro. We evaluated the safety and efficacy of the deletion mutants administered with intranasal (IN) and IN + subcutaneous (SC) vaccination protocols. Cats in the vaccination group were vaccinated twice at a 4-week interval, and all cats were challenged with infection 3 weeks after the last vaccination. The cats were assessed for clinical signs, nasal shedding, and virus-neutralizing antibodies (VN), and with postmortem histological testing.

RESULTS

Vaccination with the gI/gE-deleted and gI/gE/TK-deleted mutants was safe and resulted in significantly lower clinical disease scores, fewer pathological changes, and less nasal virus shedding after infection. All three mutants induced virus-neutralizing antibodies after immunization.

CONCLUSIONS

In conclusion, this study demonstrates the advantages of FHV-1 deletion mutants in preventing FHV-1 infection in cats.

The morbidity and the spectrum of applied drugs in shelter cats in the Czech Republic

Maintaining appropriate living conditions and good health of the animals should be one of the main priorities of cat shelters. The aim of this study was to assess the morbidity of shelter cats on the basis of analysis of the shelter health records in terms of the nature and quantity of medicaments and other supportive products administered in two no-kill shelters in the Czech Republic. The subject of the study were the health records of 1,884 cats, which were admitted to the selected shelters from 1.1.2013 to 31.12.2021 and their stay in the shelter was terminated in the monitored period. More than half of all cats whose records were analyzed had at least one health record made during their stay in the shelter. The overall length of stay of cats in the shelter (regardless of the outcome) in which one or more health records were found was significantly longer compared to the length of stay of cats without any health records. The highest number of health records was found in kittens <6 months old. Antibiotics, antiparasitics, and complementary/protective substances were the most used among all administered drugs. Broad-spectrum antibiotics have been administered to cats most often. In terms of classification of antibiotics according to the active substance, the most used antibiotics were penicillins, tetracyclines, and fluoroquinolones. Antibiotics were mostly used to treat diseases related to the upper and lower respiratory tract and their symptoms and gastrointestinal problems. The findings of the study contribute to understanding health problems and approaches to treating the shelter cats.

A Retrospective Study of Viral Molecular Prevalences in Cats in Southern Italy (Campania Region)

From 2019 to 2021, a retrospective molecular study was conducted in the Campania region (southern Italy) to determine the prevalence of viral diseases in domestic cats. A total of 328 dead animals were analyzed by Real-Time PCR for the presence of feline panleukopenia virus (FPV), feline leukemia virus (FeLV), feline enteric coronavirus (FCoV), rotavirus (RVA), feline herpesvirus type 1 (FHV-1), and feline calicivirus (FCV). The possible presence of SARS-CoV-2 was also investigated by Real-Time PCR. The cats included in this study were specifically sourced and referred by local veterinarians and local authorities to the Zooprofilactic Experimental Institute of Southern Italy (IZSM) for pathological evaluation. The samples consisted of owners, catteries, and stray cats. Results revealed: 73.5% positive cats for FPV (189/257), 23.6% for FeLV (21/89), 21.5% for FCoV (56/266), 11.4% for RVA (16/140), 9.05% for FeHV-1 (21/232), and 7.04 for FCV (15/213). In contrast, SARS-CoV-2 was never detected. FPV was more prevalent in winter (p = 0.0027). FCoV FHV-1, FCV, and RVA predominated in autumn, whereas FeLV predominated in summer. As expected, viral infections were found more frequently in outdoor and shelter cats than in indoor ones, although no statistical association was found between animal lifestyle and viral presence. The study showed a high prevalence of FPV, FeLV, and FCoV and a moderate prevalence of RVA, FHV-1, and FCV. Moreover, the prevalence of these pathogens varied among the cat populations investigated.

Antiviral Effects of Adipose Tissue-Derived Mesenchymal Stem Cells Secretome against Feline Calicivirus and Feline Herpesvirus Type 1

Mesenchymal stem cells (MSCs) have excellent anti-inflammatory and immunomodulatory capabilities and therapeutic effects in some viral diseases. The therapeutic impact of MSCs mainly relies on the paracrine effects of various secreted substances. Feline calicivirus (FCV) and feline herpesvirus type 1 (FHV1) are common and highly prevalent pathogens causing upper respiratory diseases, and FCV is associated with gingivostomatitis in cats. Recently, feline MSC treatment has been reported to improve the clinical symptoms of feline chronic gingivostomatitis, but the antiviral effects of feline MSCs on FCV and FHV1 are not known. In this study, we evaluated the antiviral efficacy of using feline MSC secretome as a conditioned medium on FCV and FHV1 viral replication in Crandell–Reese feline kidney (CRFK) cells, and RNA sequencing was used to analyze how the CRFK cells were altered by the MSC secretomes. The feline MSC secretome did not inhibit FCV or FHV1 viral entry into the CRFK cells but had antiviral effects on the replication of both FCV and FHV1 in a dose-dependent manner.

Generalized and fatal felid alphaherpesvirus-1 natural infection with liver involvement in a feline leukaemia virus-positive adult cat: a case report

Generalized and fatal felid alphaherpesvirus-1 (FeHV-1) natural infection with liver involvement is rarely reported in cats, and the occurrence of herpesvirus viraemia with internal organ histologic lesions in adult cats is unknown. A 1.5-year-old cat, female, mixed breed, positive for feline leukaemia virus (FeLV) presented in a veterinary teaching hospital with sneezing, nasal discharge, anorexia, and diarrhoea after two weeks, evolving to inspiratory dyspnoea. Complete blood count and serum biochemistry analysis showed marked leukopenia and thrombocytopenia. After clinical worsening and lack of treatment response, the cat was euthanized. Pathological findings included hepatic necrosis, fibrinonecrotic tracheitis, and bronchointerstitial pneumonia. Marked amounts of coccobacillary bacteria were observed covering the necrotic tracheal and bronchial mucosa, at the cytoplasm of alveolar macrophages, and free in alveoli lumen, mimicking a primary bacterial tracheitis and pneumonia. Both lung and tracheal bacteria exhibited marked immunolabeling in anti-Escherichia coli immunohistochemistry. In addition, rare epithelial cells of bronchi contained round, eosinophilic, intranuclear viral inclusion bodies (4-7 µm) that marginate the chromatin, characteristic of FeHV-1 infection. Strong multifocal anti-FeHV-1 immunolabeling was observed in necrotic epithelial cells of the liver, trachea, and lungs. Generalized herpesvirus infection with the occurrence of acute hepatic necrosis and severe respiratory illness is a potential differential diagnosis in FeLV-positive cats with respiratory signs. The immunodepression in these cats probably favours a FeHV-1 viraemia in addition to the development of opportunistic bacterial infections, such as Escherichia coli, and it is associated with a poor outcome.

Comparative Efficacy of Topical Ophthalmic Ganciclovir and Oral Famciclovir in Cats with Experimental Ocular Feline Herpesvirus-1 Epithelial Infection

Purpose: To determine the comparative efficacy of ganciclovir ophthalmic gel and famciclovir oral tablets in cats with experimentally induced ocular feline herpesvirus-1 (FHV-1) epithelial infection. Methods: A randomized, placebo-controlled trial was performed using 16 nonvaccinated, specific pathogen-free cats with experimental FHV-1 infection induced by topical ocular inoculation. Cats received topical ganciclovir 0.15% ophthalmic gel (1 drop 3 times daily, n = 6 cats), oral famciclovir (90 mg/kg twice daily, n = 6), or topical artificial tear gel (1 drop 3 times daily, n = 4) for 14 days. Cats were monitored after inoculation for 30 days. Ophthalmic examinations were performed every 2 days and ocular disease scores calculated. In vivo confocal microscopy was performed, and corneal leukocyte infiltrates quantified. Ocular samples for FHV-1 quantitative polymerase chain reaction (qPCR) and virus isolation assays were collected every 3 days. Hemograms and serum biochemistry panels were performed at intervals. Results: Clinical ocular disease scores and corneal leukocyte infiltrates were significantly lower in the ganciclovir and famciclovir groups compared with placebo, but no significant differences were detected between the antiviral treatment groups. Ocular viral loads determined by qPCR were significantly lower in the ganciclovir group compared with the placebo group, but there were no significant differences between the other study groups. Hemograms and biochemistry panels were unremarkable. Conclusion: Topical application of ganciclovir gel 3 times daily was well-tolerated and displayed similar efficacy at reducing clinical ocular disease scores and corneal inflammation as twice daily oral famciclovir treatment in cats with experimental ocular FHV-1 infection.

Feline herpesvirus infection and pathology in captive snow leopard

Feline herpesvirus type 1 (FHV-1) is a common causative agent of domestic cats’ rhinotracheitis in domestic cats, and it increasingly threatens wild felids worldwide. The endangered snow leopard (Panthera uncia) belongs to the family Felidae, and it is the top predator on the Tibetan Plateau. Here we report the identification and isolation of FHV-1 from three dead captive snow leopards that presented with sneezing and rhinorrhea. To explore the relationship between FHV-1 and their deaths, organs and nasal swabs were collected for histopathology, viral isolation and sequence analysis. The results revealed that all three snow leopards were infected with FHV-1. The first animal died primarily of cerebral infarction and secondary non-suppurative meningoencephalitis that was probably caused by FHV-1. The second animal died mainly of renal failure accompanied by interstitial pneumonia caused by FHV-1. The cause of death for the third animal was likely related to the concurrent reactivation of a latent FHV-1 infection. The gD and gE gene sequence alignment of the isolated FHV-1 isolate strain revealed that the virus likely originated from a domestic cat. It was found that FHV-1 infection can cause different lesions in snow leopards than in domestic cats and is associated with high risk of disease in wild felids. This suggests that there should be increased focus on protecting wild felids against FHV-1 infections originating from domestic cats.

First Report of Isolation and Molecular Characterization of Felid Herpesvirus-1 from Symptomatic Domestic Cats in Egypt

Feline herpesvirus 1 (FHV-1) is one of the main causes of upper respiratory tract infection in cats. Despite its veterinary importance, no previous studies investigated the occurrence of this virus in Egypt. In the present work, a total number of one hundred forty (N = 140) conjunctival and/or oropharyngeal swabs were collected from symptomatic cats during veterinary clinic visits located in two Egyptian provinces. Virus isolation was performed in the Chorioallantoic membranes (CAMs) of 12-days-old SPF eggs. Interestingly, the embryos showed stunting growth and abnormal feathering and infected CAMs showed edematous thickening and cloudiness with characteristic white opaque pock lesions. Polymerase chain reaction (PCR) amplification of the thymidine kinase gene (TK) was successful in 16/140 (11.4%) of the suspected cases. Two of the amplified genes were sequenced and the TK gene sequences of the FHV-1 isolates were highly similar to other reference strains in the GenBank database. Given the above information, the present study represents the first report of feline herpesvirus type 1 (FHV-1) in domestic cats in Egypt. Further studies on the causes of upper respiratory tract infections in cats as well as vaccine efficacy are needed.

Update on feline alphaherpesvirus-1 seroprevalence in Victorian feral and owned cats

The seroprevalence of feline alphaherpesvirus‐1 (FHV‐1) in feral cats in Victoria, Australia, was last assessed in 1981 when serum‐virus‐neutralising antibodies (VNAb) against FHV‐1 were detected in 11% of the sampled population from two Victorian locations. In this current study, VNAb were assessed in serum from feral cats located in Phillip Island, Point Cook and Hattah in the Mallee region in Northern Victoria. In feral cats, the seroprevalence of VNAb to FHV‐1 was highest in Point Cook at 24.6% (17/69), followed by Phillip Island at 16.7% (11/66) and Hattah where no feral cats had detectable VNAb to FHV‐1 (0/12). In contrast, virus‐neutralising antibodies were observed in 84.1% (37/44) of Victorian‐owned cats. This higher seroprevalence in owned cats is likely due to the use of FHV‐1 vaccines; however, the vaccination history of the cats was not known and the development of neutralising antibodies after infection or vaccination can vary. The results are useful for understanding FHV‐1 exposure in feral and owned cats and are important background information in the context of any potential future use of FHV‐1‐vectored vaccines.

Full Viral Genome Sequencing and Phylogenomic Analysis of Feline Herpesvirus Type 1 (FHV-1) in Cheetahs (Acinonyx jubatus)

Feline herpesvirus type 1 (FHV-1) is endemic in captive cheetahs and sporadically causes devastating disease. Modified live vaccines (MLV), intended for use in domestic cats, are used in some captive cheetah populations and have been anecdotally linked to disease in certain subpopulations. Ten FHV-1 isolates from ten captive cheetahs and one isolate from an MLV used to inoculate four of the host animals were analyzed. Viral DNA was extracted for full-genome sequencing by Illumina MiSeq with viral genomes then used for phylogenomic and recombinational analyses. The FHV-1 shed by vaccinated cheetahs were almost identical to the MLV, with few variants among viral genomes. Eight cheetah FHV-1 isolates and the MLV were grouped in a clade along with FHV-1 isolates from domestic cats in the USA. The remaining two cheetah FHV-1 isolates (unknown host vaccine status) were not associated with a clade. The likely ancestral origin of these two isolates involves recombination events between Australian domestic cat and cheetah FHV-1 isolates. Collectively, these data suggest that the MLV is capable of causing clinical disease and viral shedding in some cheetahs and represents evidence of interspecies transmission of virus between domestic and wild cats.

In vivo confocal microscopic features of naturally acquired canine herpesvirus-1 and feline herpesvirus-1 dendritic and punctate ulcerative keratitis

OBJECTIVE

To describe the in vivo confocal microscopy (IVCM) features of the corneal epithelium and stroma in dogs and cats with herpetic dendritic ulcerative keratitis.

ANIMALS

6 client-owned dogs and 10 client-owned cats with herpetic dendritic ulcerative keratitis (affected group) and 10 dogs and 10 cats from specific-pathogen-free laboratory colonies (nonaffected group).

PROCEDURES

After complete ophthalmic examination, IVCM corneal examination was performed on the clinically diseased eyes of animals in the affected group and on both eyes of animals in the nonaffected group. Results by species were compared between groups.

RESULTS

In the affected group, all 6 dogs had unilateral ocular lesions (total, 6 eyes examined), whereas 7 cats had unilateral lesions and 3 cats had bilateral lesions (total, 13 eyes examined). For the nonaffected group, 20 cat eyes and 20 dog eyes were examined. Corneal epithelial morphological abnormalities were identified in all examined eyes of animals in the affected group and in no examined eyes of the nonaffected group. Hyperreflective punctate opacities and inflammatory cells were present in all epithelial layers in examined eyes of affected animals but were absent in nonaffected animals. Similarly, Langerhans cells and anterior stromal dendritic cells were identified in corneas of eyes examined for animals in the affected group but not in any eye of animals in the nonaffected group. Stromal changes were less consistent in the affected group, but absent in the nonaffected group.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that herpetic dendritic ulcerative keratitis in dogs and cats is associated with microanatomic corneal abnormalities that can be detected by IVCM.

Use of feline herpesvirus as a vaccine vector offers alternative applications for feline health

Herpesviruses are attractive vaccine vector candidates due to their large double stranded DNA genome and latency characteristics. Within the scope of veterinary vaccines, herpesvirus-vectored vaccines have been well studied and commercially available vectored vaccines are used to help prevent diseases in different animal species. Felid alphaherpesvirus 1 (FHV-1) has been characterised as a vector candidate to protect against a range of feline pathogens. In this review we highlight the methods used to construct FHV-1 based vaccines and their outcomes, while also proposing alternative uses for FHV-1 as a viral vector.

Icariin, Formononetin and Caffeic Acid Phenethyl Ester Inhibit Feline Calicivirus Replication In Vitro

Cats infected with feline calicivirus (FCV) often display oral ulcers and inflammation of the upper respiratory tract, which can lead to death in severe cases. Antiviral therapy is one of the most effective ways to control FCV infection. Natural compounds in Chinese herbal medicines and medicinal plants provide abundant resources for research on antiviral drugs. In this study, we found that icariin (ICA), formononetin (FMN) and caffeic acid phenethyl ester (CPAE) show low cytotoxicity towards F81 cells, that the three natural compounds have apparent antiviral effects on FCV in vitro, and that they can inhibit different FCV strains. Then, we found that ICA and FMN mainly function in the early stage of FCV infection, while CAPE can function in both the early and late stages of FCV infection. Finally, we found that ICA has an antagonistic effect on FMN and CAPE in FCV infection, and FMN has a synergistic effect with CAPE against FCV infection. Our results showed that ICA, FMN and CAPE may be potential drug candidates for FCV-induced diseases.

In vitro efficacy of ganciclovir against feline herpesvirus type 1 and assessment of ocular tolerability in healthy cats

OBJECTIVES

Feline herpesvirus-1 (FHV-1) is a prevalent cause of ocular disease in cats and limited topical options for treatment currently exist. The first objective of this study was to confirm the efficacy of ganciclovir against FHV-1 in vitro. The second objective was to assess the safety and ocular tolerability of topically applied ganciclovir eye gel (GEG) in healthy cats.

METHODS

FHV-1 was used to infect tissue culture wells covered in maximally confluent Crandall-Rees feline kidney cells prior to the addition of three molarities of ganciclovir (8.9 µM, 17.8 µM and 89 µM) before being incubated for 48 h. Ganciclovir efficacy in vitro was then assessed using standard plaque reduction assay. Commercially available GEG (0.15%) was applied q8h to one randomly chosen eye of four healthy cats for 7 days. Commercially available lubricating eye gel (LEG) was applied to the opposite eye q8h. Complete blood counts (CBCs), blood chemistry panels (CHEM) and urinalysis (UA) were performed on all cats before and after the study period. Ocular lesions were assessed daily using a standardized scheme.

RESULTS

Ganciclovir led to a significant reduction in FHV-1 plaque number, area and diameter at all tested molarities in vitro. The highest molarity assessed (89 µM) caused a 100% reduction in viral plaque number. There was no significant difference in ocular lesion scores between eyes receiving GEG and LEG. Animals remained healthy throughout the study period with CBC, CHEM and UA showing no clinically significant alterations.

CONCLUSIONS AND RELEVANCE

Based on the in vitro results, ganciclovir appears to be effective against FHV-1 in vitro. When applied q8h as a commercial 0.15% gel to a small group of cats with normal eyes, this medication was well tolerated. Taken together, these data suggest this medication warrants further investigation in cats with ocular disease caused by FHV-1.

The Effects of Frequency and Duration of Handling on the Development of Feline Upper Respiratory Infections in a Shelter Setting

Simple Summary

Stress in cats residing in a shelter environment is a significant contributor to the development of upper respiratory disease (URD). Previous studies have shown that positive interactions can reduce stress and enhance the immune system. However, little is known on how the frequency and duration of daily handling affects a cat’s likelihood of developing URD. The goal of this study was to record the daily frequency and duration of handling of clinically healthy cats that were relinquished at a closed admission shelter and determine if these parameters were associated with a statistically significant increased risk of developing URD. While no parameters were statistically significantly associated with an increased hazard of developing URD, we found that cats that did not develop URD were handled more frequently than cats that did develop URD. Our results suggest that increased frequency and duration of handling does not appear to increase the risk of URD signs and may reduce the incidence of URD development. These results are important for the shelter community in developing handling and hygiene protocols for shelter cats.

Abstract

Reducing stress is important to maintaining the health of shelter cats and decreasing the risk of upper respiratory disease (URD). The aim of this study was to determine if the frequency and/or duration of daily routine handling of shelter cats affects the likelihood of URD development. At a closed admission shelter, each cat free of URD on intake was given a cage card for recording handling data. These data included: date and times when the cat was handled, duration of handling, if and when the cat developed signs of URD, and the handler identity. Cox regression was used to determine the relationship between these factors and URD development. We found cats that did not develop URD were handled significantly more than cats that did (1.1 times per day vs. 0.7 times per day, p < 0.001). Increased frequency of handling had a borderline significant effect on the hazard of developing URD (HR 0.37; CI: 0.13–1.1; p = 0.066). No other parameters were significantly associated with the development of URD; however, small sample size may be responsible for this finding. A larger study is needed to elucidate the relationship between handling and URD development.

A retrospective study on the presence of selected infectious agents in lung samples of cats with pneumonia

The causative role of some infectious agents found in cases of feline pneumonia is under debate, because they are also part of the physiological microbiota of the respiratory tract of healthy animals. In this retrospective study, archived formalin-fixed and paraffin-wax-embedded lung samples of 69 severe and lethal cases of pneumonia in cats were examined by immunohistochemistry (IHC) for the detection of nine selected infectious agents: Pasteurella multocida, Bordetella bronchiseptica, Mycoplasma felis, M. gateae, Chlamydia felis, feline herpesvirus type 1, feline coronavirus, canine distemper virus, and Toxoplasma gondii. The intention was to elucidate their immediate involvement in pneumonia formation. Due to the cross-reactivity of the applied antibodies, a species-specific polymerase chain reaction (PCR) for both targeted Mycoplasma species was applied additionally. In the 42 cases (60.9%) positive for at least one pathogen, several agents were present in a high proportion of the samples (P. multocida - 34.8%, B. bronchiseptica - 29.0%), while others were present in a moderate (feline herpesvirus type 1 - 18.8%, M. gateae - 13.0%, M. felis - 10.1%) or low percentage (T. gondii - 1.4%). All samples were negative for C. felis, feline coronavirus and canine distemper virus. Mixed infections of up to four pathogens were more frequent than single infections. Mycoplasma preferably colonised lung tissue damaged by other pathogens because they never occurred as single infections. Pasteurella multocida, B. bronchiseptica, M. felis, feline herpesvirus type 1 and T. gondii showed abundant replication within lung lesions, thus suggesting a prominent role in pneumonia formation.

Detection and Genetic Characterization of Viruses Present in Free-Ranging Snow Leopards Using Next-Generation Sequencing

Snow leopards inhabit the cold, arid environments of the high mountains of South and Central Asia. These living conditions likely affect the abundance and composition of microbes with the capacity to infect these animals. It is important to investigate the microbes that snow leopards are exposed to detect infectious disease threats and define a baseline for future changes that may impact the health of this endangered felid. In this work, next-generation sequencing is used to investigate the fecal (and in a few cases serum) virome of seven snow leopards from the Tost Mountains of Mongolia. The viral species to which the greatest number of sequences reads showed high similarity was rotavirus. Excluding one animal with overall very few sequence reads, four of six animals (67%) displayed evidence of rotavirus infection. A serum sample of a male and a rectal swab of a female snow leopard produced sequence reads identical or closely similar to felid herpesvirus 1, providing the first evidence that this virus infects snow leopards. In addition, the rectal swab from the same female also displayed sequence reads most similar to feline papillomavirus 2, which is the first evidence for this virus infecting snow leopards. The rectal swabs from all animals also showed evidence for the presence of small circular DNA viruses, predominantly Circular Rep-Encoding Single-Stranded (CRESS) DNA viruses and in one case feline anellovirus. Several of the viruses implicated in the present study could affect the health of snow leopards. In animals which are under environmental stress, for example, young dispersing individuals and lactating females, health issues may be exacerbated by latent virus infections.

Methods of Assessment of the Welfare of Shelter Cats: A Review

At any moment, there are millions of cats housed in foster care facilities for abandoned and stray animals for various reasons worldwide. Care, management and regulation among these facilities differ. Moreover, shelters can never substitute the full comfort of a good home for the animal, and the welfare of cats in shelters is a subject of discussion in many respects. Cats are animals sensitive to changes; for most of them, placement in a shelter is a stressful experience because of changes in routine, environment and the presence of other animals. Stress is reflected in changes in behaviour, causes fluctuations in physiological values and disrupts the immune system, which is a predisposition to the development or reactivation of disease. Evaluation of the presence and intensity of negative impacts is possible through the use of evaluation tools based on indicators that help set the environment and management of keeping so as to disrupt the quality of life as little as possible. Although a comprehensive and valid welfare tool that would evaluate animal-based and at the same time resource-based (or management-based) indicators of cats in shelters is not currently available, it is possible to use partial evaluation of individual welfare indicators to assess welfare. This review aims to provide the readers with an insight into current options of assessment of the welfare of cats in shelters with an emphasis on behavioural, physiological and health indicators with an application in both practical and scientific contexts.

A Randomized, Placebo-Controlled Clinical Trial of Famciclovir in Shelter Cats with Naturally Occurring Upper Respiratory Tract Disease

Simple Summary

Upper respiratory tract disease (URTD) impacts the health and welfare of shelter cats. Mitigation strategies include stress reduction and population-level approaches; effective treatment plans focus on reducing the clinical signs in cats affected by URTD. This study evaluated the use of famciclovir, an antiviral therapy, in reducing clinical signs in shelter cats with URTD when administered at a target dose range of 40–90 mg/kg twice daily for up to 21 days. Cats were randomized into either a famciclovir treatment group (n = 11) or placebo group (n = 11). Testing for viral pathogen identification was performed at enrollment in the study, and clinical scoring was completed daily to evaluate the severity of signs. With each day of treatment, cats in both groups were less likely to experience worsening clinical scores; however, cats in the famciclovir treatment group had a significantly lower risk of worsening clinical signs with each day compared to the placebo group. Feline herpesvirus, a common pathogen causing URTD, was identified in 11/21 cats. The results of this small study justify the need for further research to determine the utility of famciclovir as part of treatment protocols for improving clinical signs and overall impacts of URTD in shelter cats.

Abstract

Upper respiratory tract disease (URTD) is a clinically relevant infectious disease in shelter cats, with individual and population-level welfare implications. The purpose of this study was to evaluate the effectiveness of famciclovir in reducing clinical signs of URTD in shelter cats during a therapeutic period of up to 21 days. Cats at two Northeastern United States animal shelters with URTD clinical signs were enrolled in a pragmatic, prospective, randomized, placebo-controlled clinical trial. Cats received either famciclovir (n = 11, target dose range 40–90 mg/kg) or placebo (n = 11), administered orally twice daily for up to 21 days with once-daily clinical scoring. At enrollment, conjunctival and oropharyngeal samples were collected for respiratory pathogen identification by RT-PCR. Zero-inflated Poisson regression was used to evaluate the treatment group effects and changes in clinical scoring over time. With each day of treatment, cats in both groups were less likely to experience worsening clinical scores; however, the risk of worsening scores with each day of treatment was significantly less in the famciclovir group compared to placebo (p = 0.006). Feline herpesvirus (FHV-1) DNA was detected in 11/21 cats. The findings justify further pragmatic studies to determine whether famciclovir treatment can contribute to a clinically relevant reduction in URTD morbidity in shelter cats.

Effects of famciclovir in cats with spontaneous acute upper respiratory tract disease

OBJECTIVES

The aim of this study was to assess the effects of famciclovir administration in cats with spontaneously acquired acute upper respiratory tract disease.

METHODS

Twenty-four kittens with clinical signs of acute upper respiratory tract disease were randomly allocated to receive doxycycline (5 mg/kg PO q12h) alone (group D; n = 12) or with famciclovir (90 mg/kg PO q12h; group DF; n = 12) for up to 3 weeks. Clinical disease severity was scored at study entry and daily thereafter. Oculo-oropharyngeal swabs collected at study entry and exit were assessed using quantitative PCR for nucleic acids of feline herpesvirus type 1 (FHV-1), feline calicivirus (FCV), Chlamydia felis, Bordetella bronchiseptica and Mycoplasma felis.

RESULTS

The median (range) age of cats was 1.5 (1-6) months in group D vs 1.6 (1-5) months in group DF (P = 0.54). Pathogens detected in oculo-oropharyngeal swabs at study entry included FCV (n = 13/24; 54%), M felis (n = 8/24; 33%), FHV-1 (n = 7/24; 29%), C felis (n = 7/24; 29%) and B bronchiseptica (n = 3/24; 12%). Median (range) duration of clinical signs was 11.5 (3-21) days in group DF and 11 (3-21) days in group D (P = 0.75). Median (range) total disease score at the end of the study did not differ between groups (group D 1 [1-1] vs group DF 1 [1-3]; P = 0.08).

CONCLUSIONS AND RELEVANCE

This study revealed no significant difference in response to therapy between cats treated with doxycycline alone or with famciclovir; cats improved rapidly in both groups. However, identification of FHV-1 DNA was relatively uncommon in this study and clinical trials focused on FHV-1-infected cats are warranted to better evaluate famciclovir efficacy.

Antibody response to feline herpesvirus-1 vaccination in healthy adult cats

OBJECTIVES

Vaccination against feline herpesvirus-1 (FHV-1) is recommended for all cats. However, it is unknown how adult healthy cats with different pre-vaccination antibodies respond to FHV-1 vaccination in the field. The aim of the study was to determine the prevalence of neutralising antibodies against FHV-1 in healthy adult cats and the response to FHV-1 vaccination within 28 days of vaccination.

METHODS

One hundred and ten cats (⩾1 year of age) that had not received a vaccination within the past 12 months were vaccinated with a combined FHV-1 vaccine. Antibodies against FHV-1 were determined before vaccination (day 0), on day 7 and day 28 by serum neutralisation test. Uni- and multivariate statistical analyses were used to determine factors associated with the presence of pre-vaccination antibodies and response to vaccination.

RESULTS

Pre-vaccination neutralising antibody titres (⩾10) were present in 40.9% of cats (45/110; 95% confidence interval [CI] 32.2-50.3); titres were generally low (range 10-640). Antibody response to vaccination (⩾four-fold titre increase) was observed in 8.3% (9/109; 95% CI 4.2-15.1). Cats ⩾2 years of age were more likely to have pre-vaccination neutralising antibodies than cats aged between 1 and 2 years (odds ratio [OR] 24.619; P = 0.005). Cats from breeders were more likely to have pre-vaccination neutralising antibodies than privately owned cats (OR 7.070; P = 0.007). Domestic shorthair cats were more likely to have an at least four-fold titre increase vs purebred cats (OR 11.22; P = 0.027).

CONCLUSIONS AND RELEVANCE

Many cats have no detectable neutralising antibodies against FHV-1 despite previous vaccinations and fail to develop a ⩾four-fold titre increase after vaccination. This is likely because older cats and cats with a higher FHV-1 exposure risk are more likely to get infected with FHV-1 and thus to have FHV-1 neutralizing antibodies. Purebred cats more often fail to develop a ⩾four-fold titre increase after vaccination.

Genomic analysis for virulence determinants in feline herpesvirus type-1 isolates

Feline herpesvirus type 1 (FHV-1) is a widespread cause of respiratory and ocular disease in domestic cats. A spectrum of disease severity is observed in host animals, but there has been limited prior investigation into viral genome factors which could be responsible. Stocks of FHV-1 were established from oropharyngeal swabs obtained from twenty-five cats with signs of infection housed in eight animal shelters around the USA. A standardized numerical host clinical disease severity scoring scheme was used for each cat from which an isolate was obtained. Illumina MiSeq was used to sequence the genome of each isolate. Genomic homogeneity among isolates was relatively high. A general linear model for fixed effects determined that only two synonymous single nucleotide polymorphisms across two genes (UL37/39) in the same isolate (from one host animal with a low disease severity score) were significantly associated (p ≤ 0.05) with assigned host respiratory and total disease severity score. No variants in any isolate were found to be significantly associated with assigned host ocular disease severity score. A concurrent analysis of missense mutations among the viral isolates identified three genes as being primarily involved in the observed genomic variation, but none were significantly associated with host disease severity scores. An ancestral state likelihood reconstruction was performed and determined that there was no evidence of a connection between host disease severity score and viral evolutionary state. We conclude from our results that the spectrum of host disease severity observed with FHV-1 is unlikely to be primarily related to viral genomic variations, and is instead due to host response and/or other factors.

Chronic Rhinitis in the Cat: An Update

The etiology of feline chronic rhinitis is incompletely understood and often is a diagnosis of exclusion. History, clinical signs, and investigations performed to reach this diagnosis are discussed. Several treatment options are provided, although cure of this frustrating disease is rarely achieved.

Quantitative real time polymerase chain reaction (qRT-PCR) and RNAscope in situ hybridization (RNA-ISH) as effective tools to diagnose feline herpesvirus-1-associated dermatitis

BACKGROUND

Felid herpesvirus type 1 (FHV-1)-associated dermatitis is characterized by facial and nasal involvement; clinical and histopathological manifestations may overlap with other dermatitides.

OBJECTIVE

To evaluate the realibility of qRT-PCR-2^{- ΔΔC q} and RNAscope in situ hybridization (RNA-ISH) methods to diagnose FHV-1-associated dermatitis, in formalin-fixed paraffin-embedded (FFPE) tissues.

ANIMALS

Sixteen FFPE samples from cats with facial dermatitis and four controls were studied.

METHODS AND MATERIALS

Based on histopathological features, cases were separated into: Group 1, samples with herpetic dermatitis (four); Group 2, samples with nonherpetic facial dermatitis (six); Group 3, samples with facial dermatitis of ambiguous nature (allergic or viral) (six); and Group 4, samples from healthy cats (four). A relative quantification using the 2^{- ΔΔC q} method was used to estimate the "upregulation" of each FHV-1 target viral gene copies (glycoprotein-B and thymidine-kinase) relative to reference gene. Detection of FHV-1 mRNA was performed using the RNAscope 2.5 detection kit.

RESULTS

By 2^{- ΔΔC q} analysis, upregulation of both FHV-1 genes was observed in all samples from Group 1 and two of six from Group 3. No upregulation was identified in samples from groups 2 and 4. Positive mRNA hybridization signal was observed in all cases from Group 1 and two cases of Group 3. No positivity was observed in samples from groups 2 and 4.

CONCLUSIONS AND CLINICAL IMPORTANCE

QRT-PCR 2^-ΔΔCq analysis and RNA-ISH can identify the FHV-1 genome as causative agent of the associated dermatitis, even where inclusion bodies are not detectable. Both techniques are functional in retrospective studies, have greater specificity than conventional PCR, and may be proposed for research and diagnostic purposes.

Risk of Feline Immunodeficiency Virus (FIV) Infection in Pet Cats in Australia is Higher in Areas of Lower Socioeconomic Status

Simple Summary

Some diseases are known to occur at a higher frequency in Australia in areas of social and economic disadvantage. Identification of these diseases is important for effective infection control strategies. We investigated whether an association existed between socioeconomic factors and three infectious diseases in cats (feline immunodeficiency virus, FIV; feline calicivirus, FCV; and feline herpesvirus-1, FHV-1) in Australia. Disease cases that were reported to a voluntary veterinary disease surveillance system (Disease WatchDog) between January 2010 and July 2017 were extracted and analysed. Postcodes of the owners of these cats were compared to four government-published indexes measuring socioeconomic disadvantage and advantage. An association between socioeconomic status and FIV infection, but not FCV and FHV-1 infection, was found. FIV infection was more commonly reported in areas of socioeconomic disadvantage according to all four indexes. Prevention strategies targeting lower socioeconomic communities may help to reduce the overall prevalence of FIV infection in Australia.

Abstract

Feline immunodeficiency virus (FIV), feline calicivirus (FCV), and feline herpesvirus (FHV-1) are common viral infections of domestic cats in Australia. A study was performed to investigate the possible effect of area-based socioeconomic factors on the occurrence of FIV, FCV, and FHV-1 infection in Australian client-owned cats. A total of 1044 cases, reported to a voluntary Australian online disease surveillance system between January 2010 and July 2017, were analysed with respect to their postcode-related socioeconomic factors using the Socio-Economic Indexes For Areas (SEIFA). SEIFA consists of four different indexes which describe different aspects of socioeconomic advantage and disadvantage. Signalment details including age, sex, neuter status, and breed were also considered. A significant correlation was observed between areas of lower socioeconomic status and a higher number of reported cases of FIV infection for all four SEIFA indexes (p ≤ 0.0002). Postcodes with SEIFA indexes below the Australian median (“disadvantaged” areas) were 1.6–2.3 times more likely to have reported cases of FIV infection than postcodes with SEIFA indexes above the median (“advantaged” areas). In contrast, no correlation was observed between the number of reported cases of FCV or FHV-1 infection and any of the four SEIFA indexes (p > 0.05). When signalment data were analysed for the three infections, FIV-infected cats were more likely to be older (p < 0.00001), male (p < 0.0001), neutered (p = 0.03), and non-pedigree (p < 0.0001) compared to FCV and FHV-1 infected cats. Results from this study suggest that area-based disease control strategies, particularly in areas of social disadvantage, might be effective in reducing the prevalence of FIV infection in pet cats in Australia.

Effects of orally administered raltegravir in cats with experimentally induced ocular and respiratory feline herpesvirus-1 infection

OBJECTIVE

To determine the effects of orally administered raltegravir in cats with experimentally induced ocular and respiratory feline herpesvirus-1 (FHV-1) infection.

ANIMALS

14 healthy 6-month-old unvaccinated specific pathogen-free cats.

PROCEDURES

On day 0, all cats were experimentally inoculated by topical application of 0.1 mL of a solution containing 10⁶ plaque-forming units of FHV-1 strain FH2CS to the inferior conjunctival fornix of each eye. Cats were randomly assigned to receive either raltegravir (80 mg; n = 7) or lactose (250 mg; vehicle; 7), PO, every 12 hours for 14 days beginning on day 1. Cats were assigned clinical ocular and respiratory disease scores every other day from days 0 to 30. Conjunctival swab specimens were collected for detection of FHV-1 by virus isolation and real-time PCR assay at 3-day intervals from days 0 to 30. Confocal microscopy was performed on days 0 and 10 to assess corneal epithelial leukocyte infiltration. The assessed variables and duration of FHV-1 shedding were compared between the 2 treatment groups.

RESULTS

Cats in both groups developed moderate to severe conjunctivitis and ulcerative keratitis characteristic of FHV-1 infection. Median duration of FHV-1 shedding was shorter and signs of ocular and respiratory disease were less severe for raltegravir-treated cats than for vehicle-treated cats. However, the mean conjunctival FHV-1 titer and corneal epithelial leukocyte count did not differ between the 2 groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested orally administered raltegravir might be effective for alleviation of ocular and respiratory signs of FHV-1 infection in cats. (Am J Vet Res 2019;80:490-497).

Widespread neonatal infection with phocid herpesvirus 1 in free-ranging and stranded grey seals Halichoerus grypus

Phocid herpesvirus 1 (PhHV-1) is known to infect grey seals Halichoerus grypus but little is known about its pathogenicity or true prevalence in this species. To investigate the prevalence of and risk factors associated with PHV-1 infection, nasal swabs were collected from grey seal pups and yearlings on the Isle of May, a well-studied grey seal breeding colony, and from stranded grey seal pups submitted to a rehabilitation centre. PhHV-1 nucleic acids were detected in nasal swabs from 58% (52/90) of live free-ranging grey seal pups, 62% (18/29) of live stranded grey seal pups and 28% (5/18) of live free-ranging yearlings, suggesting recrudescence in the latter. Location within the colony, pup body mass and stranding were determined to be risk factors for shedding PhHV-1 in live seal pups with a significantly higher prevalence of PhHV-1 in pups born on the tidal boulder beach when compared to other sites; a significantly positive correlation of PhHV-1 shedding and pup body mass and a higher prevalence in stranded grey seal pups compared to their free-ranging conspecifics. The prevalence of PhHV1 in dead pups on the Isle of May was 56% (27/48) with a positive PhHV-1 PCR status significantly associated with hepatic necrosis (p = 0.01), thymic atrophy (p < 0.001) and buccal ulceration (p = 0.027). Results indicate that PhHV1 was widespread in the pups in the Isle of May grey seal breeding colony.