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

Outbreaks of nosocomial feline calicivirus-associated virulent systemic disease in Korea

IMPORTANCE

Feline calicivirus (FCV)-associated viral systemic disease (VSD) is a severe systemic disease caused by virulent FCV strains and has a very poor prognosis.

OBJECTIVE

To evaluate the clinical characteristics of a nosocomial FCV-VSD outbreak involving 18 cats in Korea.

METHODS

Medical records of cats diagnosed with FCV-VSD from March to September 2018 at a referral veterinary hospital were reviewed. The patient's signalment, history, clinical features, diagnosis, treatment, and prognosis were evaluated.

RESULTS

Two outbreaks involving 18 cats diagnosed with FCV-VSD occurred over a 6-month period at a referral hospital in Korea. Anorexia, lethargy, fever, and limb edema were the most commonly observed clinical symptoms. Lymphopenia and macrothrombocytopenia were the most common hematological findings, and hyperbilirubinemia and increased levels of aspartate aminotransferase, creatine kinase, and serum amyloid A were the most frequent results of serum biochemistry. FCV was detected by reverse transcription polymerase chain reaction in 11 patients and the remaining 7 were suspected with FCV-VSD. The overall mortality rate was 72.2%. The hospital was closed and disinfected twice, and no additional outbreaks have occurred since the last patient.

CONCLUSIONS AND RELEVANCE

The clinical and diagnostic characteristics and outcomes of FCV-VSD described in this study can be used to recognize and contain infectious diseases through quick action. To the best of the authors' knowledge, this is the first report of a nosocomial outbreak of FCV-VSD in Asia.

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.

Genetic Evolution and Biological Characteristics of Feline Caliciviruses Isolated from Dogs

Feline calicivirus (FCV) is a highly contagious pathogen associated with oral and upper respiratory tract diseases (URTD), and it is also possibly considered as an enteric pathogen. Some studies found FCV-like viruses in the enteric tract of dogs, but there was a lack of understanding regarding the epidemiology and biological properties of FCVs in dogs. In this study, 252 fecal/feces samples were collected from dogs, with or without diarrhea, from 2020 to 2021. There were 6 FCV-positive samples (2.41%, 6/252), from which only two FCVs were successfully isolated and the complete genome sequences obtained. Phylogenetic analysis showed that the two canine-origin FCV isolates belonged to genogroup I and formed a monophyletic cluster with previous FCV strains, sharing a common ancestor. However, there was genetic diversity when the nt identity of the VP1 proteins between the two canine-origin FCV isolates (77.4% nt identity) was compared. In particular, the genomic sequence of the canine/GXHC01-21 isolate showed evidence of recombination at the 3ʹ end of the ORF1 gene with sequence identity very similar to the FCV strain, GX2019, previously isolated from cats in Guangxi in 2019. A comparison of their replication properties indicated that the two isolates could not replicate efficiently in MDCK cells. This was also seen in the enteric FCV isolate, GXNN04-20. However, both displayed similar plaque phenotypes to the respiratory FCV isolate, GX01-13. In addition, it was found that sera from vaccinated cats had low cross-reactivity in a neutralizing antibody test against the two canine-origin FCV isolates. Moreover, high neutralizing antibody titers (≥1 : 128) against canine-origin FCV viruses were observed in the two canine serum samples. This confirmed that interspecies transmission had occurred between cats and dogs. Our results provided an in-depth understanding of the genetic evolution and characteristics of FCVs circulating in dogs.

Molecular Characterization and Phylogenetic Analysis of Feline Calicivirus Isolated in Guangdong Province, China from 2018 to 2022

Feline calicivirus (FCV) is a common feline infectious pathogen that mainly causes upper respiratory tract disease. To investigate the prevalence of FCV in Guangdong Province in China, a total of 152 nasal and throat swabs from cats suspected of FCV infection were collected in veterinary clinics or shelters from 2018 to 2022. The positive detection rate of FCV was 28.9% (44/152) by RT-PCR. In addition, twenty FCV isolates were successfully isolated and purified. Eleven out of twenty isolates were selected for further phylogenetic analyses based on the capsid protein VP1; our results revealed that seven isolates were in genogroup I, and four were in genogroup II. Notably, according to the whole genome phylogenetic tree, FCV-SCAU-11 was in the same branch as Korean isolates, and recombination analysis revealed that the FCV-SCAU-11 isolate showed potential recombinant events between the FCV-SH isolate and FCV-GXNN03-20 isolate. Furthermore, the virus replication kinetics indicated that FCV-SCAU-10, with clinically severe symptoms in patient cats, performed a more efficient replication in vitro. In conclusion, this study revealed the genetic diversity of FCVs in Guangdong Province, providing a reference for novel vaccine candidate strains and the development of effective strategies for preventing FCV infection in cats.

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.

Equine immunoglobulin F(ab')2 fragments protect cats against feline calicivirus infection

Feline calicivirus (FCV) causes upper respiratory tract infections in felines and threatens the health of wild and domestic felines. Clinically, specific drugs to treat FCV have not yet been developed. Here, IgG was extracted from inactivated FCV-immunized horse sera. Equine F(ab')₂ fragments were obtained from pepsin-digested IgG and then purified by protein-G column chromatography. In our study, equine immunoglobulin F(ab')₂ fragments showed efficient neutralizing activity in vitro against FCV and had therapeutic and prophylactic effects in FCV-infected cats. The anti-FCV-specific F(ab')₂ fragment can significantly alleviate the clinical symptoms of FCV-infected cats and reduce the viral loads of the trachea, lung and spleen. These results indicate that the F(ab')₂ fragment prepared from inactivated FCV-immunized horses may be used as a prophylactic and therapeutic agent for diseases caused by FCV.

•

High-purity anti-FCV F(ab')₂ fragments were prepared from equine IgG.

•

F(ab')₂ fragments can bind to FCV both in vivo and in vitro.

•

F(ab')₂ fragments can reduce the clinical symptoms in kittens infected with FCV.

•

Passive transfer of equine immune antibodies significantly reduced virus titers in the lungs and trachea of kittens.