Isolation of a feline picornavirus from cheetahs with conjunctivitis and glossitis

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.

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.

Development and validation of a TaqMan real-time reverse transcription-PCR for rapid detection of feline calicivirus

Feline calicivirus (FCV) is a common cause of upper respiratory tract disease in cats and is associated with interstitial pneumonia, oral ulceration and polyarthritis. Recently, outbreaks have involved a highly virulent FCV that leads to multisystemic signs. Virus isolation and conventional RT-PCR are the most common methods used for FCV diagnosis. However, real-time RT-PCR offers a rapid, sensitive, specific and easy tool for nucleic acid detection. The objective of this study was to design a TaqMan probe-based, real-time RT-PCR assay for detection of FCV. It was determined in our previous study that the first 120 nucleotides of the 5′ region of the genome are highly conserved among FCV isolates. Primers and a probe specific for this region were designed for a real-time RT-PCR assay to detect FCV. Initial validation was done using 15 genetically diverse isolates. Also, 122 samples were tested by the new assay and virus isolation. The real-time RT-PCR assay was as sensitive and specific as virus isolation and was far more rapid. This real-time RT-PCR assay targeting the conserved 5′ region of the genome is a fast, economical and accurate method for detection of FCV.

Seroprevalence of pathogens in domestic carnivores on the border of Madidi National Park, Bolivia

The importance of diseases of domestic animals in the conservation of wildlife is increasingly being recognised. Wild carnivores are susceptible to many of the pathogens carried by domestic dogs and cats and some of these pathogens have caused disease outbreaks and severe population declines in threatened species. The risk of disease spillover from domestic to wild carnivores in South America has not been extensively investigated. This study examined the disease exposure of domestic carnivores living near a protected area in Bolivia. Forty dogs and 14 cats living in three towns on the eastern border of Madidi National Park were sampled. High levels of exposure to canine distemper virus, canine parvovirus, Sarcoptes scabiei and Toxoplasma gondii were found among domestic dogs, with similarly high levels of exposure to feline parvovirus, feline calicivirus and T. gondii being found among domestic cats. If contact occurs between domestic and wild carnivores, disease spillover may represent an important risk for the persistence of wild carnivores in the region. Additional research is therefore necessary to determine if wild carnivores living in proximity to these domestic carnivore populations are being exposed to these pathogens.

Analysis of the capsid protein gene of a feline-like calicivirus isolated from a dog

The authors report the sequence analysis of the capsid protein-encoding gene (ORF2) of a calicivirus strain recently isolated in Italy from a pup with enteritis. Sequence comparison and phylogenetic analysis revealed that the isolate is highly similar to field and reference feline caliciviruses (FCVs). The isolation of a feline-like calicivirus and the results of recent serological investigations suggest that FCV infection frequently occurs in dogs, but the consequences of this interspecies infection in the canine host are still unknown.

Sequence variation within the capsid protein of Australian isolates of feline calicivirus

The capsid protein of Australian feline calicivirus (FCV) isolates is demonstrably different from the prototype strain F9. Five Australian isolates of FCV, dating from 1970 to 1989, were analysed by western blotting and immunoprecipitation. Varying reactivity to a panel of F9 specific monoclonal antibodies (MAbs) was observed. DNA sequencing of RT-PCR generated clones supported the observation of variation between capsid proteins. Predicted amino acid sequences varied by 11 to 17.5% across the whole capsid when compared to the published F9 sequence. Differences in amino acid sequence were most apparent in previously described hypervariable regions (C and E). Within hypervariable region E differences of 22 to 34% were observed compared to F9. The observed lack of reactivity to F9 MAbs correlated with amino acid changes within previously characterized binding sites within region E.

Viral zoonoses and food of animal origin: caliciviruses and human disease

Caliciviruses are important veterinary and human pathogens. The viruses gain their name from characteristic cup-shaped structures seen on the virion surface by negative stain electron microscopy. In humans caliciviruses are a major cause of diarrhoeal disease. There are two fundamentally different genome structures amongst human caliciviruses. The Norwalk-like or small round structured viruses (SRSVs) are viruses that have an amorphous structure when viewed by EM, they have a genome composed of 3 major open reading frames (ORFs). These viruses cause epidemic gastroenteritis amongst all age groups. In contrast, the 'classic' human caliciviruses (HuCVs) display the typical calicivirus surface structure and have their capsid ORF fused to and contiguous with the non structural proteins forming one giant polyprotein. HuCVs are predominantly associated with paediatric infections and are only a minor cause of disease in humans. Spread of disease for both SRSVs and HuCVs is usually by faecal oral transmission. SRSVs are a major cause of foodborne gastroenteritis especially linked to the consumption of sewage-contaminated shellfish. However, there is no evidence that these viruses replicate in shellfish or that they originate from an animal source.

Infectious disease surveillance in captive and free-living cheetahs: An integral part of the species survival plan

During the formulative stages of developing the Species Survival Plan (SSP) for the cheetah, the impact of infectious disease upon its survival in captivity was of prime consideration, together with genetics, nutrition, physiology, and behavior. This paper summarizes the results of an infectious disease surveillance program, initially designed to monitor the infectious agents associated with clinically normal and clinically ill cheetahs in captivity, but subsequently supplemented with data from free‐living cheetahs. The focus was on two viral infections, feline infectious peritonitis (FIP) and feline rhinotracheitis virus. Results indicated that between 1989 and 1991, there was an increase in the seroprevalence (number antibody‐positive animals) of cheetahs to feline coronavirus from 41% to 64% in captivity. During this same time period, there were only two documented cases of FIP in cheetahs in the United States. The results suggest that feline coronavirus (feline enteric coronavirus‐‐feline infectious peritonitis group) or a closely related coronavirus of cheetahs is becoming endemic in the captive cheetah population.

Further serologic results from 39 free‐living cheetahs demonstrated that there was a high seroprevalence (61%) to feline coronavirus, although serum antibody titers were considerably lower than those encountered in captive cheetahs. The observation of a high percentage of free‐living cheetahs, which were seropositive to feline herpesvirus (44%), was unexpected, since it has been generally regarded that this infection is primarily associated with cheetahs in captivity. © 1993 Wiley‐Liss, Inc.

Isolation and characterization of caliciviruses from dogs with vesicular genital disease

Two virus isolates, one from lesions of the vagina of a Bearded Collie and the other from the penis and prepuce of a Black Labrador, were partially characterized. The two viruses possessed the physicochemical properties, size and morphology of viruses belonging to the family Caliciviridae. The two isolates were shown by cross neutralization tests to be distinct from previously reported canine and feline caliciviruses. The viruses, isolated four years apart, are antigenically related. Additional studies are necessary to determine whether they are two distinct viruses or strains of another serotype belonging to the caliciviruses of the canine species.

Calcivirus (SMSV-5) infection in experimentally inoculated Opaleye fish (Girella nigricans)

At 15 degrees C, San Miguel sea lion virus infected fish (Girella nigricans), producing 10(7).6 TCID50 per gram of spleen, replicated in Vero cells (10(8) TCID50/gm) and retained viability after 14 days exposure to salt water (10(5) TCID50/ml dropped to 10(2).

Pathogenicity of a strain of feline calicivirus for domestic kittens

A strain of feline calicivirus, isolated from a cheetah exhibiting ulcerative glossitis and conjunctivitis, was administered by aerosol to 4 domestic cats and by contact to a fifth cat. Despite the limited number of animals available for the experiment, the pathogenicity of the virus strain for domestic cats was established. In aerosol-infected animals, clinical signs were referable to infection of both upper and lower respiratory tracts. The virus produced an interstitial pneumonia which, early in infection, was uncomplicated by secondary bronchopneumonia. The in-contact cat exhibited clinical signs referable to infection of the oral cavity only and no lesions were noted in the lower respiratory tract at autopsy. Ulcerative glossitis was a feature of the disease in aerosol-infected and in-contact cats. The virus was isolated from the pharynx of all cats for up to 21 days after infection and from the tonsils at autopsy. The tonsils were considered to be a probable site of multiplication of virus in "carrier" cats.

Replication of a strain of feline calicivirus in organ culture

The zwitterionic buffer HEPES was used successfully to maintain organ cultures of kitten tongue and trachea for 10--15 days in vitro. A strain of feline calicivirus grew to high titres in both tongue and tracheal explants but it was not possible to ascribe specific histological changes to virus infection in either tongue or tracheal organ cultures. Cells in tongue explants retained specific virus receptors for at least six days in vitro and virus grew to high levels in the cultures infected six days postinitiation of explants. These results suggest that at least some strains of feline caliciviruses have tropism for lingual epithelium as well as respiratory tract tissues.

Lesions produced by feline picornaviruses of different virulence in pathogen-free cats

Sixteen pathogen-free cats were exposed by aerosol to either of two feline picornavirus isolates. The isolates used were picornavirus-255 and kidney-cell-degenerating virus. These viruses were selected to represent picornavirus prototypes of high and low virulence, respectively. Picornavirus-255 consistently produced depression, anorexia, and pneumonia. There were no lesions in the upper respiratory tract or conjunctiva, nor were there clinical signs of upper respiratory disease. The pulmonary lesions began as multifocal exudative pneumonia that progressed rapidly to interstitial pneumonia characterized by marked adenomatoid proliferation of pneumocytes. Three weeks after exposure the pulmonary lesions were principally resolved. It also produced discrete lingual and palatine ulcers that were easily detected. Experimental infection with kidney-cell-degenerating virus resulted only in transient fever and tiny vesicles and ulcerations of the lingual and tonsillar mucosae that could easily escape detection. No significant respiratory lesions were induced by kidney cell degenerating virus.