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Ocular herpesviruses, most notably human alphaherpesvirus 1 (HSV-1), canid alphaherpesvirus 1 (CHV-1) and felid alphaherpesvirus 1 (FHV-1), infect and cause severe disease that may lead to blindness. CHV-1 and FHV-1 have a pathogenesis and induce clinical disease in their hosts that is similar to HSV-1 ocular infections in humans, suggesting that infection of dogs and cats with CHV-1 and FHV-1, respectively, can be used as a comparative natural host model of herpesvirus-induced ocular disease. In this review, we discuss both strengths and limitations of the various available model systems to study ocular herpesvirus infection, with a focus on the use of these non-traditional virus-natural host models. Recent work has demonstrated the robustness and reproducibility of experimental ocular herpesvirus infections in dogs and cats, and, therefore, these non-traditional models can provide additional insights into the pathogenesis of ocular herpesvirus infections.

Wildlife inhabiting human-dominated landscapes is at risk of pathogen spill-over from domestic species. With the aim of gaining knowledge in the dynamics of viral infections in Iberian wolves (Canis lupus) living in anthropized landscapes of northern Spain, we analysed between 2010 and 2013 the samples of 54 wolves by serology and polymerase chain reaction (PCR) for exposure to four pathogenic canine viruses: canine distemper virus (CDV), canine parvovirus-2 (CPV), canine adenovirus 1 and 2 (CAV-1 and CAV-2) and canine herpesvirus. Overall, 76% of the studied wolves presented evidence of exposure to CPV (96% by HI, 66% by PCR) and 75% to CAV (75% by virus neutralization (VN), 76% by PCR, of which 70% CAV-1 and 6% CAV-2). This represents the first detection of CAV-2 infection in a wild carnivore. CPV/CAV-1 co-infection occurred in 51% of the wolves. The probability of wolf exposure to CPV was positively and significantly correlated with farm density in a buffer zone around the place where the wolf was found, indicating that rural dogs might be the origin of CPV infecting wolves. CPV and CAV-1 appear to be enzootic in the Iberian wolf population, which is supported by the absence of seasonal and inter-annual variations in the proportion of positive samples detected. However, while CPV may depend on periodical introductions by dogs, CAV-1 may be maintained within the wolf population. All wolves were negative for exposure to CDV (by VN and PCR) and CHV (by PCR). The absence of acquired immunity against CDV in this population may predispose it to an elevated rate of mortality in the event of a distemper spill-over via dogs.

Canid alphaherpesvirus 1 (CHV-1) is a widespread pathogen of dogs with multiple associated clinical signs. There has been limited prior investigation into the genomics and phylogeny of this virus using whole viral genome analysis. Fifteen CHV-1 isolates were collected from animals with ocular disease based in the USA. Viral DNA was extracted for Illumina MiSeq full genome sequencing from each isolate. These data were combined with genomes of previously sequenced CHV-1 isolates obtained from hosts in the UK, Australia and Brazil. Genomic, recombinational and phylogenetic analysis were performed using multiple programs. Two isolates were separated into a clade apart from the remaining isolates and accounted for the majority of genomic distance (0.09%): one was obtained in 2019 from a USA-based host (ELAL-1) and the other in 2012 from a host in Brazil (BTU-1). ELAL-1 was found to contain variants previously reported in BTU-1 but also novel variants in the V57 gene region. Multiple non-synonymous variants were found in USA-based isolates in regions associated with antiviral resistance. Evidence of recombination was detected between ELAL-1 and BTU-1. Collectively, this represents evidence of trans-boundary transmission of a novel form of CHV-1, which highlights the importance of surveillance for this pathogen in domestic dog populations.

Canine herpesvirus‐1 (CHV‐1), as a member of the Varicellovirus, subfamily Alphaherpesvirinae and family Herpesviridae, is mainly transmitted at birth but can also spread venereally and transplacentally. In addition, CHV‐1 establishes a latent carrier state in the body and can reactivate due to stress or immunosuppression. CHV‐1 distribution varies worldwide but is believed to have a global distribution. CHV‐1 infection in adult canines can manifest as a spectrum of ocular from eyelid inflammation (blepharitis) and conjunctival inflammation (conjunctivitis) to more severe corneal conditions, including ulcerative and non‐ulcerative keratitis. Moreover, CHV‐1 in adult canines can lead to a range of reproductive effects, from submucosal vascular congestion and bleeding to foetal expulsion and preterm birth of live offspring. Subclinical or mildly symptomatic upper respiratory tract disease can manifest in juvenile and adult canines. Prophylactic topical antimicrobial therapy is recommended to prevent disease progression in dogs with CHV‐1 ocular disease. However, the environmental temperature increase for affected puppies fails to modify the disease progression. Environmental variables, including breeding facility size and animal population density, facilitate herpesvirus transmission and subsequent immune responses. There are various diagnostic techniques, but the most prevalent method is polymerase chain reaction (PCR) for viral DNA detection. Due to the global distribution of the virus and its effects, such as ocular and reproductive effects and subsequent financial losses, it is recommended that infected dogs be identified and treated promptly, as well as prevent its transmission. Taxonomy: Herpesviridae, Alphaherpesvirinae and Varicellovirus. Diagnosis: PCR for genetic detection. Transmission: Birth, venereal and transplacental. Pathogenesis: Ocular lesions; blepharitis, conjunctivitis and ulcerative and non‐ulcerative keratitis. Reproductive effects: submucosal vascular congestion and bleeding to foetal expulsion and preterm birth of live offspring. Subclinical or mildly symptomatic URTD. Latency and reactivation (stress/immunosuppression). Management: Prophylactic topical antimicrobial therapy in dogs with CHV‐1 ocular disease. Enhance breeding facility size and animal population density. Identify and treat infected dogs promptly in order to prevent its transmission. Antimicrobial therapy and antiviral agents.

The guanine and cytosine content (GC-content) of alpha-herpesvirus genes are highly variable despite similar genome structures. It is known that drug resistant HSV, which has the genome with a high GC-content (approximately 70%), commonly includes frameshift mutations in homopolymer stretches of guanine (G) and cytosine (C) within the thymidine kinase (TK) gene. However, whether such mutation hotspots exist in the TK gene of canine herpesvirus (CHV) which has a low GC-content was unknown. In this study, we investigated mutations in the TK gene of CHV. CHV was passaged in the presence of iodo-deoxyuridine (IDU), and IDU-resistant clones were isolated. In all IDU-resistant virus clones, mutations in the TK gene were observed. The majority of these mutations were frameshift mutations of an adenine (A) insertion or deletion within either of 2 stretches of eight A's in the TK gene. It was demonstrated that CHV TK mutations frequently occur at a limited number of hot spots within long homopolymer nucleotide stretches.

Canine herpesvirus 1 (CHV-1) is an important cause of death in newborn puppies and of fertility problems in adult dogs. Identification of risk factors may help to reduce infection rates and alleviate concerns for dog owners and breeders. This study was designed to screen for CHV-1 infection in bitches of breeding kennels and farms in Iran and relate this to possible risk factors. A total of 63 vaginal samples were collected from dogs in 5 breeding kennels (n = 47) and from 7 farms (n = 16). Real-time polymerase chain reaction was used to detect the CHV-1 specific glycoprotein B (gB) gene. Prevalence rates were evaluated in relation to various risk factors, including region, housing, vaccination, deworming, pregnancy, reproductive problems, number of dogs living together and hygiene conditions. In total, 21 (33.3%) of 63 vaginal samples were positive for CHV-1 DNA. The prevalence rate in farms (7/16; 43.7%) was higher than in kennels (14/47; 29.7%). No association was found between CHV-1 prevalence and potential risk factors. CHV-1 is highly prevalent in dogs in Iranian farms and kennels. Since the CHV1 vaccine is unlicensed in Iran, effective management strategies are essential to reduce the consequences of this pathogen.

Six bitches free of canine herpesvirus 1 (CHV-1) were vaccinated against the virus; a first injection was given 10 days after the presumed date of mating and a second six weeks later. Six similar bitches were left unvaccinated as controls, and all the pups were challenged oronasally with a virulent strain of cHv-1 at three days of age. All the vaccinated bitches seroconverted and had high antibody titres when the puppies were challenged, but the control bitches remained seronegative. In the control group, 62 per cent (18 of 29) of the pups died of cHv-1-induced disease; most of them showed typical clinical signs and macroscopic lesions, and CHv-i infection was confirmed by the isolation of the virus or by PCR. None of the puppies in the vaccinated group died of CHV-1 infection. The efficacy of the vaccine was confirmed in cHv-1-positive breeding units. The rate of pregnancy tended to be higher in vaccinated bitches and the mortality of pups before weaning was significantly reduced in the litters born to vaccinated bitches.

BACKGROUND: Canine herpesvirus-1 (CHV1) causes a fatal hemorrhagic disease in neonatal puppies and is associated with infertility in female dogs. This study was conducted to assess the status of CHV1 infection in bitches in proestrus or estrus and to investigate possible risk factors by a detailed questionnaire. Blood samples were collected from healthy bitches (n = 193) not vaccinated against CHV1, aged one year or older and admitted for estrus control to the Canine Reproductive Clinical Unit, Norwegian School of Veterinary Science. The serum samples were analysed by immunoperoxidase monolayer assay and serum titers were recorded as the reciprocal value of the highest dilution producing specific cell staining. RESULTS: Altogether, 85.5% of the dogs had CHV1 titers ≥ 80 and were classified as positive. Mean age for dogs included in the study was 4.2 years (95% CI 4.0-4.5), and there was no difference in age between seronegative dogs vs seropositive dogs. When grouping the seropositive dogs into three categories according to the magnitude of the titer, a total of 38.8% of the bitches displayed a weakly positive titer of 80, 44.8% had moderately positive titers of 160 or 320 and 16.4% of the dogs fell into the strongly positive category with titer of ≥640. No association was demonstrated when comparing CHV1 antibody titers to fertility parameters such as previous matings, pregnancies, whelpings, puppies born or condition of puppies. Further, there was no difference in seroprevalence between bitches that had been abroad for a period of time and dogs only living within a Norwegian environment. Samples from dogs collected in summer and fall displayed moderate to high antibody titers indicating recent infection with CHV1. Season, previous birth, and participation in competitions/shows explained 67-78% of the variation in antibody titer. CONCLUSIONS: This study demonstrates that CHV1 infection is common in breeding bitches in the eastern part of Norway. Associations with putative risk factors were not identified. However, season, previous whelping, and participation in competitions/shows explained 67-78% of the variation in antibody titer.

An epidemiological survey investigated the prevalence of canine herpes virus-1 antibodies in a population of 325 pet dogs in England. Sera were analysed for the presence of canine herpes virus-1 neutralising antibody by means of a serum neutralisation test and for virus-specific IgG and IgM by means of enzyme-linked immunosorbent assays. In contrast with published results from other parts of the world, canine herpes virus-1 infection was shown to be common among the domestic dog population of England.

Canine herpesvirus 1 (CaHV-1) infects dogs, causing neonatal death and ocular, neurological, respiratory, and reproductive problems in adults. Although CaHV-1 is widespread in canine populations, only four studies have focused on the CaHV-1 whole genome. In such context, two CaHV-1 strains from both the kidney and spleen of 20-day-old deceased French Bulldog puppies were recently isolated in Sardinia, Italy. The extracted viral DNA underwent whole-genome sequencing using the Illumina MiSeq platform. The Italian CaHV-1 genomes were nearly identical (>99%), shared the same tree branch, and clustered near the ELAL-1 (MW353125) and BTU-1 (KX828242) strains, enlarging the completely separated clade discussed by Lewin et al., in 2020. This study aims to provide new insights on the evolution of the CaHV-1, based on high-resolution whole-genome phylogenetic analysis, and on its clinicopathological characterization during a fatal outbreak in puppies.