Canine Herpesvirus Infection Research Articles

Prevalence of canine herpesvirus 1 and associated risk factors among bitches in Iranian breeding kennels and farms.

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.

Fatalities in a litter of French bulldogs puppies due canine herpesvirus 1

This case report describes the occurrence of canine herpesvirus 1 in a litter of French bulldogs. In addition, the literature dealing with CHV-1 in puppies is summarized. Two puppies were presented due to dyspnea. During the night, one of them developed diarrhea as well as a highly disturbed general condition and was subsequently euthanized the following day. The second puppy was euthanized 6 hours later with a highly disturbed general condition. Necropsy revealed evidence of canine herpesvirus infection. This was confirmed by a virological examination. The presented case report shows that canine herpesvirus infection must also be considered as a cause of death in newborn puppies in Germany.

Pathology of canine herpesvirus infection

Pseća je herpesviroza globalno prisutna virusna zarazna bolest prouzročena psećim herpesvirusom 1 (Canid alphaherpesvirus-1; CHV). Infekcija ovim virusom ima dvije faze: litičku i latentnu. Sam ishod infekcije uvelike ovisi o dobi i razvijenosti imunološkog sustava psa. Najznačajnija patološka posljedica pseće herpesviroze je liza endotelnih stanica i epitelnih stanica više organskih sustava koja se pojavljuje u imunodeficijentnih štenaca. Zbog pantropizma CHV-a, posljedica infekcije je nekrohemoragična upala mnogobrojnih organa zbog koje štenci nerijetko i ugibaju. U imunokompetentnih starijih pasa, iako često asimptomatska, litička infekcija može biti i smrtonosna. Klinički simptomi uključuju infekcije dišnog i spolnog sustava i očiju. Najčešće prisutna lezija očiju je konjunktivitis, ali mogu se pojaviti i ulceracije, petehijalna krvarenja i eksudativni blefaritis s krustama i alopecijom. Utjecaj CHV-a na respiratorni sustav rezultira blagim rinitisom, faringitisom i traheobronhitisom, iznimno pneumonijom. CHV se često povezuje i sa zaraznim traheobronhitisom u pasa, tzv. ‘’kašaljem štenare’’. Infekcija spolnog sustava ograničena je na hiperemiju vagine ili prepucija s hiperplastičnim limfoidnim folikulima te papulovezikularnim lezijama, ali se smatra najvažnijim izvorom infekcije za štenad pri porođaju. Prestankom kliničkih simptoma CHV prelazi u fazu latencije u živčanim ganglijima te se na taj način trajno zadržava u domaćinu. Prilikom stresa i imunosupresije latentni se CHV virus može reaktivirati i uspostaviti litičku fazu. Time se virus ponovno počinje replicirati i izlučivati, a oboljeli pas se mora isključiti iz uzgoja jer predstavlja izvor daljnjeg širenja virusa. Ipak, primjenom cjepiva u gravidnih kuja moguće je zaštititi novorođenu štenad te spriječiti teške posljedice herpesviroze u pasa.

Review on important diseases of Dogs: At glance

Dogs are one of the most accepted pet animals in every household. Increasing urbanization and modernization of human life has created a space where people are living in nuclear family or alone. This has created peoples’ perception and acceptance of having pet for companionship. Human- dog interaction and close livelihood confinement emerge as crucial threat of outbreaks of zoonotic disease even a dog’s diseases. To prevent and control diseases of dogs, it requires proper knowledge of vaccination, education of pet health management and pets’ diseases. Therefore, the current review is on describing dog diseases like, Rabies, Canine Parvoviral gastroenteritis, Canine Distemper, Canine Coronaviral infection, Canine Rotavirus infection, Canine Herpesvirus infection, Canine Leptospirosis, Canine Brucellosis, Transmissible venereal tumors (TVT), Kennel cough, Pyoderma at glance which provides concise information regarding the causative agents and other relevant details.

Intensive ocular sampling for the detection of subclinical canine herpesvirus-1 shedding in dogs with experimentally-induced latent infection

Latent canine herpesvirus-1 (CaHV-1) infections are common in domestic dogs, but viral shedding patterns in dogs are poorly understood. Previous research failed to detect spontaneous subclinical ocular CaHV-1 shedding in dogs following ocular infection, a situation that is fundamentally distinct from many of the alphaherpesviruses closely related to CaHV-1. One possible explanation for this finding is that the sampling interval in the prior studies evaluating ocular shedding patterns was too infrequent to detect rapidly cleared, brief ocular viral shedding episodes. To evaluate for this potential viral shedding scenario, 10 laboratory beagles recovered from experimental primary ocular CaHV-1 infection and with latent CaHV-1infection were intensively monitored for viral reactivation and shedding for 28 days. Clinical ophthalmic examinations were performed daily. Ocular swab samples were collected for CaHV-1 polymerase chain reaction 3 times daily and CaHV-1 virus neutralizing antibody assays were evaluated at 2-week intervals. No abnormalities suggestive of recurrent CaHV-1 ocular disease were observed during clinical ophthalmic examination in the dogs during the study. Ocular CaHV-1 shedding was not detected by polymerase chain reaction and CaHV-1 virus neutralizing antibody titers remained stable in all dogs for the study duration. In the present study utilizing frequent multiple daily sample collections, no evidence of subclinical ocular CaHV-1 shedding was detected in mature dogs with experimentally-induced latent CaHV-1 infection.

Local immune and microbiological responses to mucosal administration of a Liposome-TLR agonist immunotherapeutic in dogs

BackgroundNon-specific immunotherapeutics have been evaluated previously in dogs, primarily for cancer treatment. However, there remains a need for a more broadly targeted, general purpose immunotherapeutic capable of activating innate immune defenses for non-specific protection or early treatment of viral and bacterial infections. To address need, our group has developed a liposomal immune stimulant (liposome-TLR complexes, LTC) containing TLR 3 and 9 agonists specifically designed to activate mucosal immune defenses in sites such as nasal cavity and oropharynx, following topical delivery. In this study, we evaluated the local immune stimulatory properties of LTC in vitro and in healthy purpose-bred dogs, including activation of cellular recruitment and cytokine production. The ability of LTC treatment to elicit effective antiviral immunity was assessed in dogs following a canine herpesvirus outbreak, and the impact of LTC treatment on the local microbiome of the oropharynx was also investigated.ResultsThese studies revealed that LTC potently activated innate immune responses in vitro and triggered significant recruitment of inflammatory monocytes and T cells into the nasal cavity and oropharynx of healthy dogs. Administration of LTC to dogs shortly after an outbreak of canine herpesvirus infection resulted in significant reduction in clinical signs of infection. Interestingly, administration of LTC to healthy dogs did not disrupt the microbiome in the oropharynx, suggesting resiliency of the microflora to transient immune activation.ConclusionsTaken together, these results indicate that LTC administration mucosally to dogs can trigger local innate immune activation and activation of antiviral immunity, without significantly disrupting the composition of the local microbiome. Thus, the LTC immune stimulant has potential for use as a non-specific immunotherapy for prevention or early treatment of viral and bacterial infections in dogs.

Transcriptomic analysis of differential gene expression reveals an increase in COX2 levels during in vitro canine herpesvirus infection

ABSTRACT: Canine herpesvirus (CaHV-1) affects canids worldwide, causing death in neonates and immunosuppressed hosts. Acute infection by CaHV-1 can cause reproductive, respiratory, and neurological problems in adult animals. Viral pathogenesis and host genes expressions during of CaHV-1infection are not clearly understood. In the present study, the transcriptome of canine kidney cell Mardin-Darby (MDCK) infected in vitro with canine herpesvirus was explored. For this, RNA sequencing (RNA-seq) of the samples in different moments during infection was carried out. Subsequently, the transcriptomic analysis genes related to cell activities and process involved to viral cycle infection were evaluated until 32h post-inoculation (pi). Among evaluated genes, was verified a significant and gradative increase of the prostaglandin-endoperoxide synthase 2 (PTGS2) or cyclooxygenase 2 (COX2) gene expression, throughout of infection, though differential gene expression analysis and validated by quantitative reverse transcription PCR (RT-qPCR). High COX2 expression is usually induced in response to inflammation, pathogens or activation of the immune system but can be a viral mechanism to favor viral replication. Thus, COX2 level increase can be a favorable factor for viral infection with Cahv-1 virus and the use of selective COX2 inhibitors may be beneficial for limiting the infection or clinical signs by causing interruption of the viral replication cycle during active infection. Additionally, the regulation genes expression differential verified in this study can contribute to determining important targets for inhibiting canine herpesvirus infection either by cellular or viral mechanisms.

Evaluation of topical ophthalmic ganciclovir gel for the treatment of dogs with experimentally induced ocular canine herpesvirus-1 infection.

OBJECTIVE To determine the in vitro half maximal effective concentration (EC50) of ganciclovir for canine herpesvirus-1 (CHV-1) and to evaluate the efficacy of ganciclovir ophthalmic gel in dogs with experimentally induced ocular CHV-1 infection. ANIMALS 10 specific pathogen-free adult Beagles. PROCEDURES Cytotoxicity and EC50 of ganciclovir for CHV-1 were determined during in vitro experiments. During an in vivo experiment, dogs with experimentally induced ocular CHV-1 infections received 1 drop of 0.15% ganciclovir (ganciclovir group; n = 5) or artificial tear (control group; 5) ophthalmic gel in both eyes 5 times daily for 7 days, then 3 times daily for 7 days. For each dog, ophthalmic and confocal microscopic examinations were performed at predetermined times to determine severity of ocular disease and inflammation. Conjunctival swab specimens were collected at predetermined times for PCR assay analysis to determine CHV-1 shedding. RESULTS No in vitro cytotoxic effects were observed for ganciclovir concentrations ≤ 500μM. The EC50 of ganciclovir for CHV-1 was 37.7μM. No adverse effects associated with ganciclovir were observed during the in vivo experiment. Mean ocular disease and inflammation scores for the ganciclovir group were significantly lower than those for the control group. Mean duration of CHV-1 shedding for the ganciclovir group (0.4 days) was significantly shorter than that for the control group (6.2 days). CONCLUSIONS AND CLINICAL RELEVANCE Topical administration of 0.15% ganciclovir ophthalmic gel was well tolerated and effective in decreasing clinical disease scores, ocular tissue inflammation, and duration of viral shedding in dogs with experimentally induced ocular CHV-1 infection.

Detection of Canine Herpesvirus Infection on Dogs

Detection of Canine Herpesvirus Infection on Dogs

Clinical and immunological assessment of therapeutic immunization with a subunit vaccine for recurrent ocular canine herpesvirus-1 infection in dogs

Latent canine herpesvirus-1 (CHV-1) infections are common in domestic dogs and reactivation of latent virus may be associated with recurrent ocular disease. The objectives of the present study were to evaluate the ability of a subunit CHV-1 vaccine to stimulate peripheral CHV-1 specific immunity and prevent recurrent CHV-1 ocular disease and viral shedding. Mature dogs with experimentally-induced latent CHV-1 infection received a 2-dose CHV-1 vaccine series. Recurrent ocular CHV-1 infection was induced by corticosteroid administration in the prevaccinal, short-term postvaccinal (2 weeks post-vaccination), and long-term postvacccinal (34 weeks post-vaccination) periods. Immunological, virological, and clinical parameters were evaluated during each study period. Quantitative assessment of peripheral immunity included lymphocyte immunophenotyping, proliferation response, and interferon-γ production; and CHV-1 virus neutralizing antibody production. In the present study, vaccination did not prevent development of ocular disease and viral shedding; however, there was a significant decrease in clinical ocular disease scores in the short-term postvaccinal period. Significant alterations in peripheral immunity detected in the dogs during the short-term and long-term postvaccinal periods included increased T and B lymphocyte subpopulation percentage distributions, increased lymphocyte expression of major histocompatibility complex class I and II, increased CHV-1 virus neutralizing antibody titers, decreased lymphocyte proliferation, and decreased interferon-γ production. Vaccination of latently infected mature dogs with the selected subunit CHV-1 vaccine was not effective in preventing recurrent ocular CHV-1 infection and viral shedding induced by corticosteroid administration. The vaccine did induce long-term CHV-1 specific immunity and may decrease the severity of clinical ocular disease in the immediate postvaccinal period.

Effects of topical ocular application of 1% trifluridine ophthalmic solution in dogs with experimentally induced recurrent ocular canine herpesvirus-1 infection.

OBJECTIVE To determine the effects of topical ocular application of 1% trifluridine ophthalmic solution in dogs with experimentally induced recurrent ocular canine herpesvirus-1 (CHV-1) infection. ANIMALS 10 specific pathogen-free Beagles. PROCEDURES 12 months prior to the beginning of the randomized, masked, placebo-controlled 30-day trial, latent ocular CHV-1 infection was experimentally induced in each dog by topical ocular inoculation of both eyes with a field strain of CHV-1. Recurrent ocular CHV-1 infection was induced by oral administration of prednisolone for 7 days (starting day 1). Starting on the fourth day of prednisolone administration, each dog received 1% trifluridine solution or artificial tears (placebo) topically in both eyes 6 times daily for 2 days and then 4 times daily for 12 days. Ophthalmic examinations were performed every 2 days, and ocular disease scores were calculated. Ocular samples for CHV-1 PCR assays and blood samples for clinicopathologic analyses and assessment of CHV-1 serum neutralization antibody titers were collected at predetermined intervals. RESULTS Conjunctivitis was clinically detected in all dogs by day 4. Compared with dogs receiving placebo, mean and total clinical ocular disease scores were significantly lower and median CHV-1 shedding duration was significantly shorter for the trifluridine-treated dogs. Both groups had increasing CHV-1 serum neutralization antibody titers over time, but no significant differences between groups were detected. Clinicopathologic findings were unremarkable throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE Topical ocular application of 1% trifluridine ophthalmic solution was well tolerated and effective at reducing disease scores and viral shedding duration in dogs with experimentally induced ocular CHV-1 infection, but may require frequent administration.

Serological and biomolecular survey on canine herpesvirus-1 infection in a dog breeding kennel.

Canine herpesvirus-1 (CaHV-1) is a globally distributed pathogen causing reproductive, respiratory, ocular and neurological disorders in adult dogs and neonatal death in puppies. This pathogen is considered poorly immunogenic, and neutralizing antibodies are found for only a short time following exposure. Further, seroprevalence can be affected by several epidemiological factors. A virological survey was conducted in a high-density population breeding kennel in Central Italy. There were several factors predisposing animals to CaHV-1 infection, such as age, number of pregnancies, experience with mating and dog shows, cases of abortion, management and environmental hygiene. Serum neutralization (SN) and nested PCR assays were used to estimate prevalence of CaHV-1. None of the submitted samples tested positive for nested PCR, and none of the sera tested CaHV-1 positive. No association was observed between antibody titers and risk factors, and no sign of viral reactivation was detected in either males or females. These results suggest that CaHV-1 is not circulating within this kennel and that further studies are needed in order to better understand the distribution of the virus within Italy.

In Vitro and In Vivo Evaluation of Cidofovir as a Topical Ophthalmic Antiviral for Ocular Canine Herpesvirus-1 Infections in Dogs.

The effects of cidofovir were investigated against canine herpesvirus-1 (CHV-1) in vitro and in dogs with experimentally induced recurrent ocular CHV-1 infection, a host-adapted pathogen animal model of ocular herpes simplex virus-1 (HSV-1) infection. The cidofovir EC50 was determined for CHV-1 and HSV-1. A randomized, masked vehicle-controlled trial was performed using beagles with experimentally induced recurrent ocular CHV-1 infection. Dogs received 1 drop of 0.5% cidofovir solution or 0.9% sodium chloride solution (vehicle) in both eyes 2 times daily for 14 days. Dogs were monitored at intervals for 30 days by a clinical ophthalmic examination, in vivo confocal microscopy of the cornea and conjunctiva, ocular sample CHV-1 polymerase chain reaction assay, hemogram, and serum biochemistry panel. Clinical ocular disease scores were calculated and infiltrating leukocytes detected by in vivo confocal microscopy quantified. Cidofovir displayed similar in vitro antiviral activity against CHV-1 and HSV-1. Clinical ocular disease scores were significantly higher in the cidofovir group compared to the vehicle group. Marked conjunctival pigmentation and blepharitis were also detected in the cidofovir group, but not the vehicle group. Conjunctival and corneal leukocyte infiltration scores determined by in vivo confocal microscopy were significantly higher in the cidofovir group. Dogs administered cidofovir had significantly reduced durations of ocular viral shedding compared to the vehicle group. Hemogram and serum biochemistry panel values were unremarkable. Twice-daily application of topical 0.5% cidofovir ophthalmic solution reduced the duration of ocular viral shedding in dogs with experimentally induced recurrent ocular CHV-1 infection, but was associated with local ocular toxicity.

Effects of ocular surface strontium-90 beta radiotherapy in dogs latently infected with canine herpesvirus-1

Latent canine herpesvirus-1 (CHV-1) infections are common in domestic dogs, but stimuli causing viral reactivation and recrudescent disease are poorly understood. Immunosuppressive pharmaceuticals are currently the only experimentally established triggers for recurrent ocular CHV-1 infection in dogs; however, ocular CHV-1 shedding has been reported clinically following strontium-90 beta radiotherapy of the ocular surface and it has been speculated that radiotherapy can directly induce viral reactivation. Strontium-90 is used as a beta radiation source for the treatment of a variety of neoplastic and immune-mediated canine ocular surface diseases. In the present study, the effects of ocular surface strontium-90 beta radiotherapy in dogs latently infected with CHV-1 were evaluated. Ten mature dogs with experimentally induced latent CHV-1 infections were randomly divided into two groups: one group received a single fraction 50Gy radiation dose in one application from a strontium-90 ophthalmic applicator and the second group received sham radiotherapy. Dogs were then monitored for 45 days for recurrent ocular CHV-1 infection using clinical and virological outcome measures. Clinical ophthalmic examinations, ocular sample CHV-1 PCR assays, and serum CHV-1 virus neutralizing antibody assays were performed at specified intervals. No abnormalities suggestive of recurrent CHV-1 ocular disease were observed on clinical examination in any dog during the study. Ocular viral shedding was not detected and CHV-1 virus neutralizing titers remained stable in all dogs. A single fraction 50Gy radiation dose administered to the ocular surface by strontium-90 beta radiotherapy did not result in detectable recurrent ocular CHV-1 infection in mature dogs with experimentally induced latent infection.

Effects of cold stress as a pathogenic factor on fatal disease progression of canine herpesvirusinfection

Canine herpesvirus (CHV) is a member of the alphaherpesvirus subfamily, which can cause severe hemorrhagic diseases in neonatal pups as well as mild or subclinical respiratory infections in adult dogs. We examined the effects of cold stress on disease progression of CHV, an alphaherpesvirus, in neonatal puppies. Eight puppies were challenged intranasally with CHV suspension and divided into a cold stress treatment group and a hyperthermal group. Four pups were left uninoculated as controls and divided into cold and hyperthermal groups. In the challenged cold treatment group, all pups showed CHV-related disease within 5 days; pathological changes were observed in organs of puppies showing clinical symptoms. Grossly, numerous petechial red foci were scattered throughout lungs, kidneys, livers, and intestines of all CHV-infected puppies exposed to cold stress. Most puppies showed typical clinical signs and macroscopic lesions, and CHV infection was confirmed by isolation of the virus. However, in the challenged hyperthermal group, only one of the pups showed mild symptoms of CHV-induced disease. None of the puppies in the uninoculated group showed abnormal signs, although they were exposed to cold stress. These findings indicate that cold stress can cause rapid disease progression of CHV, an alphaherpesvirus.

A serological study of canine herpesvirus-1 infection in a population of breeding bitches in Norway

BackgroundCanine 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.ResultsAltogether, 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.ConclusionsThis 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.

Canine herpesvirus-1 ocular diseases of mature dogs

Canine herpesvirus-1 (CHV-1) is an alphaherpesvirus with a host range restricted to canids. Latent CHV-1 infection is endemic in domestic dog populations worldwide. The role of CHV-1 in severe systemic neonatal infections and as an aetiology of infectious infertility and abortion has been appreciated for decades; however, ocular diseases of mature dogs conclusively associated with CHV-1 infection were only recently described. Clinically, CHV-1 infection may produce a diverse range of adnexal and ocular surface lesions in mature dogs, including blepharitis, conjunctivitis, ulcerative keratitis, and nonulcerative keratitis. These conditions can develop during primary or recurrent ocular CHV-1 infection. Recurrent CHV-1 infections associated with reactivation of latent virus may be observed during a variety of situations and in association with numerous different viral reactivation stimuli, including the administration of immunosuppressive pharmaceuticals. The understanding of CHV-1 pathophysiology and ocular infections in mature dogs has expanded rapidly during the past few years, but much remains to be elucidated. As the number of dogs living with chronic immunomodulatory systemic diseases and receiving immunosuppressive therapeutics continues to grow, the clinical importance of CHV-1 ocular infections is also likely to increase.

Canine Herpesvirus During Pregnancy and Non‐Pregnant Luteal Phase

Canine herpesvirus (CHV) is a widespread infection among dogs that typically get latently infected after exposure and can reactivate the infection after stress. The aim of the present study was to study the effects of latent CHV infection during pregnancy on pregnancy outcome, and to study if there are signs of genital viral reactivation during pregnancy or during non-pregnant luteal phase. Twelve mated bitches and eight control bitches were followed and sampled regularly during pregnancy or non-pregnant luteal phase. Blood samples were taken for antibody analysis and vaginal swabs for real-time PCR analysis. Three of the pregnant bitches were vaccinated against CHV during pregnancy. All bitches had antibodies to CHV. Two pregnant bitches that were not vaccinated had a twofold or larger increase in CHV titre, with no negative effects detected on pregnancy. Higher titres were not associated with smaller litters or with vaccination. There was no consistent variation in antibody titres due to pregnancy or non-pregnant luteal phase. Vaginal excretion of CHV was not detected from any of the bitches.

Frequency of spontaneous canine herpesvirus-1 reactivation and ocular viral shedding in latently infected dogs and canine herpesvirus-1 reactivation and ocular viral shedding induced by topical administration of cyclosporine and systemic administration of corticosteroids

To determine the frequency of spontaneous canine herpesvirus-1 (CHV-1) reactivation and ocular viral shedding in latently infected dogs and the effect of topical ocular administration of cyclosporine. 8 mature Beagles with experimentally induced latent CHV-1 infection. Following induction of primary ocular CHV-1 infection, the presence of reactivatable CHV-1 latency was confirmed by systemically administering prednisolone to the dogs. Dogs were then monitored for 36 weeks via clinical examination and conjunctival sample CHV-1 PCR assay performed at 4-day intervals and CHV-1 virus neutralization antibody assay performed at 2-week intervals. During weeks 16 to 32, dogs were administered 0.2% cyclosporine ointment in both eyes twice daily and blood cyclosporine concentrations were monitored. During weeks 33 to 36, the presence of reactivatable CHV-1 latency was reconfirmed via systemic administration of prednisolone. Reactivation of latent CHV-1 was not detected via clinical examination or viral shedding during the initial 32 weeks, including before and during topical ocular administration of cyclosporine, and there were no significant differences in CHV-1 virus neutralization titer increases between the study periods. Blood cyclosporine concentrations were less than assay detection limits in all dogs on the sampling days. Systemic administration of corticosteroids repeatedly resulted in ocular disease and viral shedding. Spontaneous CHV-1 reactivation did not occur frequently in latently infected mature dogs, and this was not altered by topical ocular administration of cyclosporine. This characteristic may be a factor contributing to the lower frequency of recurrent herpetic ocular disease in dogs relative to other host species and their associated alphaherpesviruses.

A serologic study of canine herpes virus-1 infection in the Norwegian adult dog population

Canine herpes virus-1 (CHV1) causes a fatal hemorrhagic disease in neonatal puppies and is associated with reproductive problems in female dogs. This serologic study was conducted to assess the seroprevalence of CHV1 infection in Norway. Blood samples were collected from clinically healthy dogs (n = 436) one yr of age and older of both genders, supplied by four small animal clinics (A, B, C and D) in different parts of the country. The immunoperoxidase monolayer assay was used for testing of CHV1 antibodies. Serum titers were recorded as the reciprocal value of the highest dilution producing specific cell staining. Titers equal to or above 80 were considered positive for exposure to CHV1. In total, 80.0% of the dogs had titers ≥80 and were classified as positive. Mean age for seronegative dogs was 4.7 yrs (95% CI 4.1–5.4) and for seropositive dogs 5.0 yrs (95% CI 4.7–5.4). Of the dogs, 32.8% displayed a weakly positive titer of 80, whereas 41.5 and 5.7% fell into the moderately (titer 160 and 320) and strongly (titer ≥640) positive categories, respectively. No association was demonstrated when comparing CHV1 antibody titers to gender or reproductive parameters like previous matings, pregnancies, births or number of puppies born. Age, visit in foreign countries and clinic explained together 78% of the variation in antibody titer categories. The percentage of positive samples differed significantly between the four clinics (A 98%, B 58.5%, C 74.6%, D 89.5%). A reasonable explanation for this finding has not been established. No information about an ongoing outbreak of CHV1 infection was available. In conclusion, this study strongly indicates that CHV1 infection is endemic in the dog population of Norway. There are significant differences in seroprevalence between geographic regions in the country.