Feline Herpesvirus Infection of Snow Leopard

Feline herpesvirus type 1 (FHV-1) is a common causative agent of domestic cats rhinotracheitis and gradually threatens the wild felid worldwide. The endangered snow leopard belongs to the family Felidae and is also the top predator on the Tibetan Plateau. Herein, FHV-1 was identified and isolated from three dead snow leopards with symptom of sneezing and rhinorrhea. To explore the relationship between FHV-1 and their death, histopathology and molecular biology was performed. The organs and nasal swabs were collected for examinations of histopathology, the nucleic acid of the pathogen, viral isolation, and sequence analysis. The results reveal that all three snow leopards were infected with FHV-1. The first case primarily died of old cerebral infarction and secondary non-suppurative meningoencephalitis probably caused by FHV-1. The second case mainly died of renal failure accompanied by interstitial pneumonia caused by FHV-1. The third case was doubted to be related to the reactivation of latency of FHV-1. The gD and gE gene sequence alignment of the FHV-1 isolate strain revealed that the isolated strain originated from a domestic cat. Therefore, FHV-1 infection can cause different lesions of snow leopards and shows a high risk for the wild felid. We should focus more on protecting felid against threatening of FHV-1 infection originating from domestic cats.

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.

Development and application of a triplex TaqMan RT-PCR assay for simultaneous detection of Feline calicivirus, Feline Herpesvirus 1 and Feline parvovirus

The feline calicivirus (FCV), feline herspesvirus 1 (FHV-1) and feline panleukemia virus (FPV) are heavily threaten the health of cats. In this study, a triplex TaqMan real-time polymerase chain reaction (RT-PCR) assay (triplex assay) was developed to detect these viruses. The optimized concentration of primers was 0.5 µM of each, probes concentration was 0.1 µM for FCV and FHV-1, 0.05 µM for FPV. The annealing temperature was set at 54 ℃. The triplex RT-PCR assay was carefully validated. The detection limit for FPV, FCV, and FHV-1 was 5×101 copies/µL, which showed a 10-100-fold increase in the sensitivity compared with the conventional PCR. The coefficients of variation (CV) of the intra-assay variability of the test were < 1.86%, and that of inter-assay was < 3.19%, indicating excellent repeatability and reproducibility of the triplex assay. Additionally, the assay has perfect specificity. In a pilot study, samples from 48 cats were analyzed using the triplex RT-PCR method and the commercial kits, and further confirmed by sequencing. The positive rates for the samples analyzed with these two methods were 70.83% and 62.5%, respectively, which demonstrated that the developed method was more accurate than the commercial kits in clinical diagnosis.

Effects of dietary nucleotides and cationic peptides on vaccination response in cats

Modulation of the immune system through nutrition is the aim of many studies. As the induction of a rapid onset of immunity in cats is often critical, the objective of this study was to evaluate the effects of orally administered dietary nucleotides and cationic peptides, on the vaccination response in cats. The cats were allocated to two groups: Group A (n = 8) was fed a diet with dietary nucleotides and cationic peptides for ninety-two days, and Group C (n = 8) was fed a diet without the nucleotides and cationic peptides. The cats were vaccinated against feline herpesvirus 1 (FHV-1), feline calicivirus (FCV) and feline panleukopenia virus (FPV). The proliferation activity of lymphocytes and antibody response after vaccination were evaluated using ELISA kits. Comparing the two groups, a significant increase in the proliferation activity of the lymphocytes (P &lt; 0.01) was observed in Group A, as well as a significant increase in the antibody titres after vaccination against feline herpesvirus (P &lt; 0.05; P &lt; 0.001), feline calicivirus (P &lt; 0.01; P &lt; 0.001) and feline panleukopenia virus (P &lt; 0.01; P &lt; 0.001). Protective levels of the antibodies were reached significantly earlier in Group A than in Group C. In conclusion, dietary nucleotides and cationic peptides have a positive effect on the lymphocyte proliferation and antibody production after vaccination against FHV-1, FCV and FPV in cats. Therefore, we assume that they can be used as a suitable immunostimulatory substance in feline practice.

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.

Experimental Infection of Domestic Cats with Feline Herpesvirus-1 Strain CH-B Isolated from British Shorthair Cat

Background: Feline herpesvirus-1 (FHV-1) is a most common virus that cause viral rhinotracheitis and ocular diseases in domestic cats and wild felids. As other alpha-herpesviruses, acute FHV-1 infection is responsible for severe upper respiratory tract and ocular disease, followed by lifelong latency that persist the limited virus in sensory neuronal cells. While latency reactivation can result in recrudescence, leading sever ocular lesions. Hence, FHV-1 infection in cats can be considered as a good natural host model to study alpha-herpesvirus pathogenesis. Results: In this study, the FHV-1 CH-B was isolated from nasal discharge collected from a British shorthair cat in China, and was further identified via transmission electron microscopy (TEM) observation, indirect immunofluorescence assay (IFA) and genome analysis. Experimental infection of domestic cats with different dose of isolate CH-B, ranging from 104 to 107 TCID50, showed that cats inoculated with 105 TCID50 not only showed typical upper respiratory track and ocular symptoms, but also could copy the progress of disease development. Therefore, the FHV-1 infection model was established by intranasally inoculated with 105 TCID50 of FHV-1 isolate CH-B. Infected cats began to show clinical signs at days 5 post inoculated (dpi), developed severe upper respiratory tract and ocular symptoms at 10-15 dpi, began to recover at 20 dpi, and recovered almost completely by 25 dpi. During acute infection period, virus mainly replicates in turbinate, conjunctiva, cornea and sensory neuronal cells, while virus only persists in trigeminal ganglia (TG) at lifelong latency. Viremia and viral infections in lungs do not appear in FHV-1 CH-B infected cats, with only one exception. We also demonstrate that FHV-1 CH-B infection can induce severe inflammatory responses and lung, trachea, and tonsils tissues damage in cats. In addition, we found that FHV-1 infected cats can shed virus via nasal and ocular discharge, resulting FHV-1 infection in in-contact cats. Conclusions: This natural host model of FHV-1 infection will be valuable for the screen and assessment of antiviral drugs and vaccines, as well as the studies of the pathogenesis of alpha-herpesvirus infection in animals and humans.