Outbreak of ocular disease associated with naturally-acquired canine herpesvirus-1 infection in a closed domestic dog colony

Manifestations of systemic disease in the retina and fundus of cats and dogs

The fundus is unique in that it is the only part of the body that allows for a noninvasive and uninterrupted view of vasculature and nervous tissue. Utilization of this can be a powerful tool in uncovering salient incidental findings which point to underlying systemic diseases, and for monitoring response to therapy. Retinal venules and arterioles allow the clinician to assess changes in vascular color, diameter, outline, and tortuosity. The retina and optic nerve may exhibit changes associated with increased or decreased thickness, inflammatory infiltrates, hemorrhages, and detachments. While some retinal manifestations of systemic disease may be nonspecific, others are pathognomonic, and may be the presenting sign for a systemic illness. The examination of the fundus is an essential part of the comprehensive physical examination. Systemic diseases which may present with retinal abnormalities include a variety of disease classifications, as represented by the DAMNIT-V acronym, for Degenerative/Developmental, Anomalous, Metabolic, Neoplastic, Nutritional, Inflammatory (Infectious/Immune-mediated/ischemic), Toxic, Traumatic and Vascular. This review details systemic illnesses or syndromes that have been reported to manifest in the fundus of companion animals and discusses key aspects in differentiating their underlying cause. Normal variations in retinal anatomy and morphology are also considered.

Case Reports for Topical Treatment of Corneal Ulcers with a New Matrix Therapy Agent or RGTA® in Dogs

Superficial corneal ulcers that fail to heal within a normal time period and are refractory to conventional therapy in dogs are common in veterinary practice. Different etiologies can lead to this result, including spontaneous chronic corneal epithelial defects (SCCEDs) and ulcerative keratitis associated with bullous keratopathy. Thus, there is an urgent need to find new therapeutic approaches such as matrix therapy replacement. To determine the efficacy of a new ophthalmic treatment (Clerapliq^®) for SCCEDs and ulcerative keratitis associated with bullous keratopathy, a total of 11 dogs referred to the clinic because of nonhealing erosive ulcers after a classic primary treatment were enrolled to get this new treatment. Dogs underwent ophthalmic exams and 7 dogs (10 eyes) were diagnosed with superficial ulceration and 4 dogs (5 eyes) with bullous keratopathy due to endothelial dystrophy/degeneration. They received eye drops of Clerapliq^® every 3 days until recovery. The results showed that the corneas with recurrences of the ulcers were resolved predominantly by using Clerapliq^® every 3 days in 83.3% of the cases during a period of treatment ranging between 6 to 35 days. Therefore, this new approach using matrix therapy regenerating technology in treating superficial ulcers and bullous keratopathy in dogs can be successfully considered as an adjunctive therapy.

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.

New Paradigms for the Study of Ocular Alphaherpesvirus Infections: Insights into the Use of Non-Traditional Host Model Systems

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.

Keratitis in six dogs after topical treatment with carbonic anhydrase inhibitors for glaucoma

CASE DESCRIPTION

6 dogs (10 eyes) with keratitis following long-term topical treatment with a carbonic anhydrase inhibitor (CAI) were evaluated. In 4 dogs (6 eyes), CAI treatment was discontinued. Three dogs (4 eyes) underwent enucleation because of end-stage corneal disease. One dog was treated differently in each eye and thus was represented in both aforementioned groups.

CLINICAL FINDINGS

Following initiation of treatment with a CAI (ie, brinzolamide or dorzolamide), the median time to development of severe ocular signs was 266 days (range, 133 to 679 days). Clinically severe ocular signs included ulcerative and nonulcerative perilimbal keratitis or severe diffuse keratitis with marked vascularization. The keratitis was refractory to treatment with anti-inflammatory medications. Histologic and immunohistochemical examination of enucleated globes was performed in 3 affected dogs and in 1 dog with keratitis that recovered. Corneal lesions included 2 distinct inflammatory infiltrates with plasma cells predominating in the anterior stroma and both T cells and neutrophils in the epithelium. Stromal plasma cells and overlying epithelium exhibited strong positive immunoreactivity for IgG.

TREATMENT AND OUTCOME

Topical CAI treatment was discontinued in 4 dogs after a median of 209 days (range, 44 to 433 days), and in these dogs, clinical improvement was evident within 2 to 4 days of CAI treatment cessation. Signs of keratitis resolved in 12 to 25 days in these 4 dogs, and median follow-up time after CAI discontinuation was 25.5 months (range, 6 to 42 months), during which time signs of corneal disease did not recur.

CLINICAL RELEVANCE

On the basis of this small series, presumed topical CAI-associated keratitis in dogs appeared to be an uncommon immune-mediated disease that was not responsive to corticosteroid treatment. Affected patients improved rapidly, but only after discontinuation of CAI treatment. In dogs with glaucoma, clinicians should consider the development of punctate keratopathy and severe diffuse keratitis as potential adverse effects related to topical administration of CAIs, even after previously uneventful long-term use.

Multi-drug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex infection outbreak in dogs and cats in a veterinary hospital

BACKGROUND

Members of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex cause severe outbreaks in humans, and are increasingly reported in animals.

OBJECTIVE AND METHODS

A retrospective study, describing a severe outbreak in dogs and cats caused by a multidrug resistant member of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex in a veterinary hospital, between July 2010 and November 2012.

RESULTS

The study included 19 dogs and 4 cats. Acinetobacter calcoaceticus-Acinetobacter baumannii complex bacteria were isolated from urine (9 animals), respiratory tract (11), tissues (3) and blood (1). The most common infection-associated findings included fever, purulent discharge from endotracheal tubes, hypotension, and neutropaenia. Infections led to pneumonia, urinary tract infection, cellulitis and sepsis. Infection was transmitted in the intensive care unit, where 22 of 23 animals were initially hospitalised. The mortality rate was 70% (16 of 23 animals), and was higher in cases of respiratory infection compared to other infections. Aggressive environmental cleaning and disinfection, with staff education for personal hygiene and antisepsis, sharply decreased the infection incidence.

CLINICAL SIGNIFICANCE

Health care-associated outbreaks with multidrug resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex in dogs and cats are potentially highly fatal and difficult to eradicate, warranting monitoring, antiseptic techniques and judicious antibiotic use.

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

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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.

Effects of cyclophosphamide myelosuppression in adult dogs with latent canine herpesvirus-1 infection

Latent canine herpesvirus-1 (CHV-1) infection is common in domestic dogs, but triggers for viral reactivation and recrudescent CHV-1 disease are poorly understood. Cyclophosphamide is a potent immunosuppressive and myelosuppressive agent used for the therapy of a variety of neoplastic and immune-mediated canine disorders. Cyclophosphamide (200mg/m(2)) was administered to mature dogs latently infected with CHV-1 to determine its potential to induce recurrent CHV-1 disease and viral shedding. Non-infected dogs and dogs recovered from experimental primary ocular CHV-1 infection with experimentally confirmed latent CHV-1 infection were divided into groups and administered cyclophosphamide or placebo. Dogs were monitored for myelosuppression and viral reactivation for 28days using clinical and virological outcome measures. Clinical ophthalmic and in vivo ocular confocal microscopic examinations were performed at intervals. Samples were collected for CHV-1 polymerase chain reaction (PCR), CHV-1 virus neutralizing (VN) antibody, and hemogram assays. Myelosuppression (i.e., decreased total leukocyte, segmented neutrophil, and erythrocyte counts) was detected on study day 7 in dogs administered cyclophosphamide, but not dogs administered placebo. There were no abnormalities suggestive of recurrent CHV-1 ocular disease during clinical ophthalmic or in vivo confocal microscopic examination in any dogs during the study. Ocular CHV-1 shedding was not detected by PCR and CHV-1 VN titers remained stable in all dogs. Following study conclusion, the presence of reactivatable latency was reconfirmed in the infected dogs by administering systemic prednisolone. Myelosuppression elicited by a single dose of cyclophosphamide does not result in detectable recurrent ocular CHV-1 infection in adult dogs with experimentally induced latent CHV-1 infection.

Canine reproductive, respiratory, and ocular diseases due to canine herpesvirus

This review documents how clinical inquiry expands as our knowledge base about canine herpesvirus (CHV) increases. We must understand the various forms of CHV infection that may occur in the dog population. This has prompted the veterinary community to develop more sensitive diagnostic assays. CHV is more common than we considered a decade ago. Up to 70% of some high-risk dog populations have been infected with and are latent carriers of CHV. Recognition of the various forms of CHV-induced disease, availability of diagnostic assays with increased sensitivity, and the formation of reliable biosecurity measures will allow for better control steps.

Acute primary canine herpesvirus-1 dendritic ulcerative keratitis in an adult dog

We present a report of dendritic ulcerative keratitis in a 4-year old locally immunosuppressed dog suspected to result from acute primary canine herpesvirus-1 (CHV-1) infection. The dog was presented for evaluation of mild blepharospasm and conjunctival hyperemia in the right eye (OD) shortly after attending a public boarding facility. For approximately 3 months, the dog had been receiving topical prednisolone acetate 1.0% and tacrolimus 0.02% in both eyes (OU) q12h for treatment of follicular conjunctivitis. Ophthalmic examination revealed three regions of corneal fluorescein retention OD. The lesions had a dendritic pattern, were approximately 2-3 mm in length, and were located at the dorsomedial, lateral, and ventromedial aspects of the cornea. No additional abnormalities were noted on complete ophthalmic and physical examinations. CHV-1 was identified in conjunctival samples OD by polymerase chain reaction, and paired CHV-1 serum virus neutralization antibody titers were positive and consistent with acute infection. Topical prednisolone acetate and tacrolimus were discontinued. The dog was treated with cidofovir 0.5% OU q12h for a period of 4 weeks, with resolution of corneal disease noted within 1 week of treatment. In conjunction with previous studies, this case report supports a central role for alterations in host immune status in the pathogenesis and clinical manifestations of CHV-1 ocular disease in dogs.

Development and validation of a real-time PCR assay for specific and sensitive detection of canid herpesvirus 1

A TaqMan-based real-time PCR assay targeting the glycoprotein B-encoding gene was developed for diagnosis of canid herpesvirus 1 (CHV-1) infection. The established assay was highly specific, since no cross-reactions were observed with other canine DNA viruses, including canine parvovirus type 2, canine minute virus, or canine adenovirus types 1 and 2. The detection limit was 10¹ and 1.20 × 10¹ DNA copies per 10 μl⁻¹ of template for standard DNA and a CHV-1-positive kidney sample, respectively: about 1-log higher than a gel-based PCR assay targeting the thymidine kinase gene. The assay was also reproducible, as shown by satisfactory low intra-assay and inter-assay coefficients of variation. CHV-1 isolates of different geographical origins were recognised by the TaqMan assay. Tissues and clinical samples collected from three pups which died of CHV-1 neonatal infection were also tested, displaying a wide distribution of CHV-l DNA in their organs. Unlike other CHV-1-specific diagnostic methods, this quantitative assay permits simultaneous detection and quantitation of CHV-1 DNA in a wide range of canine tissues and body fluids, thus providing a useful tool for confirmation of a clinical diagnosis, for the study of viral pathogenesis and for evaluation of the efficacy of vaccines and antiviral drugs.

The effect of topical ocular corticosteroid administration in dogs with experimentally induced latent canine herpesvirus-1 infection

Recurrent herpes simplex virus-1 (HSV-1) ocular infection is a frequent cause of morbidity and blindness. Factors that trigger viral reactivation are poorly understood and the role of topical ocular corticosteroid administration in the development of recurrent HSV-1 ocular disease is not clear. Clinical reports and epidemiological studies suggested topical corticosteroids may reactivate latent HSV-1 and result in recrudescent ocular disease; however, experimental studies to establish this causal relationship produced inconsistent results. The previous experimental studies were performed by infecting unnatural host species with HSV-1 and aspects of viral behavior and reactivation within these animals may differ from the host for which the virus is adapted. The purpose of the study reported here was to determine if topical ocular corticosteroid administration results in viral reactivation and recrudescent ocular disease in a host-adapted pathogen animal model of HSV-1 recurrent ocular disease. Canine herpesvirus-1 (CHV-1) is a corticosteroid-sensitive alphaherpesvirus that is biologically related to HSV-1 and induces similar ocular lesions in canids during recurrent infection. A randomized, masked, placebo-controlled, crossover study was performed. Primary ocular CHV-1 infection was experimentally induced in mature specific pathogen-free beagles by topical ocular inoculation and the presence of reactivatable latency was later confirmed by administration of an immunosuppressive dosage of systemic corticosteroid to the dogs. Twelve months following experimental CHV-1 reactivation, dogs were administered either topical ocular prednisolone acetate (1.0% ophthalmic suspension, one drop in both eyes, four times daily) or placebo (artificial tear solution, one drop in both eyes, four times daily) for 28 days. After a 14 day washout period, the treatment groups were reversed and study agents administered for an additional 28 days. Ophthalmic examinations, in vivo ocular confocal microscopy, real-time quantitative CHV-1 polymerase chain reaction assays, and CHV-1 serum neutralization antibody titers were performed at regular intervals throughout the study. Viral reactivation was not detected in dogs administered topical ocular prednisolone or placebo as determined by clinical ocular disease recrudescence, in vivo ocular confocal microscopic findings, ocular viral shedding, and serologic response. Similar to other animal models of recurrent HSV-1 ocular infection, the behavior of latent CHV-1 in dogs may differ from HSV-1 in humans; however, results of the present study suggest administration of topical ocular prednisolone at the evaluated drug concentration, dosing frequency, and treatment duration is not likely to result in detectable reactivation of latent CHV-1 in experimentally infected dogs. This may be attributed to insufficient systemic absorption of locally administered corticosteroid to reactivate latent virus and produce recurrent disease. Crystalline corneal opacities that were apparently not associated with viral reactivation were detected by clinical examination and in vivo confocal microscopy in two dogs during topical ocular prednisolone administration. The crystalline keratopathy may have resulted from corneal degeneration associated with metaherpetic disease, corticosteroid administration, or a combination of both factors.

Nosocomial outbreak of serious canine infectious tracheobronchitis (kennel cough) caused by canine herpesvirus infection

Canine herpesvirus (CHV; Canid herpesvirus 1) is principally a perinatal pathogen of pregnant bitches and newborn pups and secondarily a respiratory tract pathogen of older pups and dogs. Infectious disease of the canine respiratory tract frequently occurs among dogs in groups, in which it is called " infectious tracheobronchitis" (ITB). Mortality from ITB is generally negligible, and the clinical importance of CHV as an ITB pathogen is considered to be low. The present report describes a novel ITB outbreak accompanied by death among aged dogs in an animal medical center. Most inpatient dogs had received medications that could induce immunosuppression. CHV was the only pathogen identified, and several CHV isolates were recovered in cell culture. No other viral pathogens or significant bacterial pathogens were found. Molecular and serological analyses revealed that the causative CHV isolates were from a single source but that none was a peculiar strain when the strains were compared with previous CHV strains. The virus had presumably spread among the dogs predisposed to infection in the center. The present results serve as a warning to canine clinics that, under the specific set of circumstances described, such serious CHV outbreaks may be expected wherever canine ITB occurs.