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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

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.

Canine herpesvirus 47 kD and mutated 41 kD glycoproteins are responsible for hemagglutination

Monoclonal antibodies (MoAbs) were used to identify the hemagglutinin of canine herpesvirus (CHV). The inhibition of viral hemagglutination (HA) activity was observed with MoAbs against 41 kD glycoprotein, while no hemagglutination-inhibition (HI) activity was observed with those against 145/112 kD and 80 kD glycoproteins, suggesting that the 41 kD glycoprotein is the hemagglutinin of plaque-selected virus of CHV YP11 strain used as immunogen for MoAb production. All of the HI MoAbs also showed HI activities against HA antigens which were prepared from cells infected with other CHV strains, namely, F-205 V and Glasgow CHV2 reference strains, eight Japanese isolates, and the original YP11 strain. However, on immunoblotting analysis, a 47 kD protein band was detected in these strains by the HI MoAbs. These data suggest that the 47 kD glycoprotein is the common molecule of the hemagglutinin among CHV strains and the plaque-selected virus of YP11 strain appears to be a mutant whose molecular weight of the hemagglutinin changed into 41 kD.

Serological, bacteriological and clinical observations on an outbreak of canine infectious tracheobronchitis in Norway

During the autumn of 1988 an outbreak of canine infectious tracheobronchitis, which seemed to be more infectious than usual, occurred throughout Scandinavia. Paired serum samples and bacterial swabs were collected from 52 dogs with clinical signs of infectious tracheobronchitis in three districts of Norway. The results revealed a fourfold or greater rise in the titre of antibodies against canine parainfluenza virus in 79 per cent of the cases, strongly suggesting that the virus was of aetiological importance in the outbreak. Bordetella bronchiseptica was not isolated from the diseased dogs, and they showed no rise in the titres of antibodies against influenza virus, reovirus or adenovirus.

Serodiagnosis of canine herpesvirus infection--development of an enzyme-linked immunosorbent assay and its comparison with two improved methods of serum neutralization test

An enzyme-linked immunosorbent assay (ELISA) for the diagnosis of canine herpesvirus (CHV) infection using antigen prepared by solubilizing infected cells was developed. The ELISA and two improved methods of serum neutralization test, the microplate serum neutralization test (MSNT) with complement and the 50% plaque reduction (PR) assay with complement, were compared for the results of antibody detection from a total of 557 field canine sera. Of 529 sample sera that were negative in the MSNT with complement, 119 were ELISA positive, and this result together with time course of serum antibody detection in a dog experimentally infected with CHV strongly suggested that the MSNT with complement is less sensitive for the detection of antibody in CHV infected dogs, especially those in early stages of infection. A correlation was found between the titers measured by the ELISA and 50% PR assay with complement, however, for field use, the ELISA is recommended as a highly sensitive test method of serodiagnosis of CHV infection adequate for dealing with a large number of samples with less demand on time and effort.

Experimental ocular herpesvirus infection in the cat. Sites of virus replication, clinical features and effects of corticosteroid administration

Experimentally induced ocular feline herpesvirus 1 (FHV-1) infection was studied in 30 specific pathogen-free cats. In ten cats, the ability of five field isolates of FHV-1 to replicate in the epithelium and substantia propria of cornea and conjunctiva was demonstrated by histochemical techniques. Feline herpesvirus 1 was found to preferentially infect and induce necrosis of conjunctival epithelium. Although significant histologic lesions were not induced, all FHV-1 strains were observed to replicate in corneal epithelium; minimal viral antigen was detected in the corneal stroma. The course and clinical features of ocular FHV-1 infection were then studied over a period of 60 days in two groups of ten cats: in one group, infection was preceded by administration of subconjunctival betamethasone. In each of these groups, a distinct clinical syndrome developed. In cats not receiving corticosteroids, a course of epithelial keratitis, characterized by the formation of punctate and dendritic epithelial lesions, persisted for up to 24 days postinfection. In the corticosteroid treated group, a chronic (greater than 60 days) stromal keratitis developed, characterized by geographic epithelial ulceration, interstitial edema and deep vascularization. Other complications observed in corticosteroid-treated animals included decreased tear production, calcific-band keratopathy and a unique stromal disorder of cats termed corneal sequestration. The results of this study indicate that while epithelial keratitis may occur during primary infection, stromal keratitis does not, unless immune responsiveness to FHV-1 is concomitantly suppressed. This feature is similar to naturally occurring HSV-1 keratitis of humans, but contrasts to other animal model systems in which stromal keratitis predictably occurs during primary infection. Study of this animal model, therefore, may allow unique insights into the events preceding the establishment of stromal keratitis.

Viral respiratory diseases

An overview of the more commonly encountered viral diseases of the dog and cat is presented. The reader is acquainted with the principles of antiviral therapy and the drugs that have been studied for use in animal viral respiratory diseases. An update on vaccination principles and guidelines is provided.

Experimental transplacental transmission of canine herpesvirus in pregnant bitches during the second trimester of gestation

The effects of canine herpesvirus (CHV) on fetuses were studied after IV inoculation of pregnant bitches in the 2nd trimester of gestation. Cesarean sections were performed on 2 bitches that were inoculated with CHV on the estimated 30th day of gestation. Bitch M-1 had 2 mummified fetuses and bitch M-2 had 4 mummified and 2 dead fetuses and 3 live-born pups. Infection by CHV was confirmed histopathologically by the presence of focal areas of necrosis associated with intranuclear inclusion bodies in heart muscle sections of 1 dead fetus; CHV was not recovered from other organs. Abortion occurred between the 2nd and 3rd week after inoculation of another pregnant bitch inoculated with CHV on the estimated 30th day of gestation. Two bitches inoculated with CHV on the estimated 40th day of gestation gave birth prematurely to 10 pups. The detection of characteristic herpesviral lesions in various organs and the reisolation of CHV from the liver, spleen, kidneys, and lungs of premature pups indicated CHV infection. Transplacental infection of fetal pups by CHV resulted in their death and subsequent mummification. It appears that abortion and premature birth also may occur in pregnant bitches infected during the 2nd trimester of gestation.

Experimental transplacental infection of pregnant dogs with canine herpesvirus

Fetal infection was established in 28 of 33 pups obtained from 7 pregnant dogs (47th to 53rd day of gestation) inoculated IV with canine herpesvirus (CHV). The pathogenesis of transplacental CHV infection was investigated by using pathologic examination, immunofluorescence microscopy, and viral assay. Infection with the virus was recognized in 13 of 18 neonatal pups obtained from 4 bitches by spontaneous delivery at full term. Eleven pups died within a week of birth and all had characteristic lesions of CHV infection. Thirteen live-born and 2 stillborn pups derived from 3 bitches by cesarean section died within 9 days of birth. Characteristic lesions of CHV infection were observed in various organs, such as liver, spleen, kidney, and lung. Fourteen of the fetal placentas had variable degree of necrotizing lesions. The lesions were characterized by degenerative changes and focal necrosis in the placental labyrinth. Lesions were present in the walls of allantoic blood vessels. Intranuclear inclusions were evident in degenerating trophoblast cells and in the cells of maternal and fetal blood vessels. Infective virus and viral antigen were detected in the various organs of pups and in the trophoblastic cells of junctional zone. Virus also was found in the walls of maternal and fetal blood vessels of the placental tissues. The results strongly indicated that transplacental transmission of CHV may occur in pregnant dogs at a late stage of gestation.