Lights and shades on an historical vaccine canine distemper virus, the Rockborn strain.

Both egg- and cell-adapted canine distemper virus (CDV) vaccines are suspected to retain residual virulence, especially if administered to immuno-suppressed animals, very young pups or to highly susceptible animal species. In the early 1980s, post-vaccine encephalitis was reported in dogs from various parts of Britain after administration of a particular batch of combined CDV Rockborn strain/canine adenovirus type-1 vaccine, although incrimination of the Rockborn strain was subsequently retracted. Notwithstanding, this, and other reports, led to the view that the Rockborn strain is less attenuated and less safe than other CDV vaccines, and the Rockborn strain was officially withdrawn from the markets in the mid 1990s. By sequencing the H gene of the strain Rockborn from the 46th laboratory passage, and a commercial vaccine (Candur(®) SH+P, Hoechst Rousell Vet GmbH), the virus was found to differ from the commonly used vaccine strain, Onderstepoort (93.0% nt and 91.7% aa), and to resemble more closely (99.6% nt and 99.3% aa) a CDV strain detected in China from a Lesser Panda (Ailurus fulgens). An additional four CDV strains matching (>99% nt identity) the Rockborn virus were identified in the sequence databases. Also, Rockborn-like strains were identified in two vaccines currently in the market. These findings indicate that Rockborn-like viruses may be recovered from dogs or other carnivores with distemper, suggesting cases of residual virulence of vaccines, or circulation of vaccine-derived Rockborn-like viruses in the field.

Historical and ecological determinants of genetic structure in arctic canids.

Wolves (Canis lupus) and arctic foxes (Alopex lagopus) are the only canid species found throughout the mainland tundra and arctic islands of North America. Contrasting evolutionary histories, and the contemporary ecology of each species, have combined to produce their divergent population genetic characteristics. Arctic foxes are more variable than wolves, and both island and mainland fox populations possess similarly high microsatellite variation. These differences result from larger effective population sizes in arctic foxes, and the fact that, unlike wolves, foxes were not isolated in discrete refugia during the Pleistocene. Despite the large physical distances and distinct ecotypes represented, a single, panmictic population of arctic foxes was found which spans the Svalbard Archipelago and the North American range of the species. This pattern likely reflects both the absence of historical population bottlenecks and current, high levels of gene flow following frequent long-distance foraging movements. In contrast, genetic structure in wolves correlates strongly to transitions in habitat type, and is probably determined by natal habitat-biased dispersal. Nonrandom dispersal may be cued by relative levels of vegetation cover between tundra and forest habitats, but especially by wolf prey specialization on ungulate species of familiar type and behaviour (sedentary or migratory). Results presented here suggest that, through its influence on sea ice, vegetation, prey dynamics and distribution, continued arctic climate change may have effects as dramatic as those of the Pleistocene on the genetic structure of arctic canid species.

Heterogeneity within the hemagglutinin genes of canine distemper virus (CDV) strains detected in Italy.

Canine distemper virus (CDV) is a highly contagious viral pathogen causing lethal disease in dogs and other mammalians. A high degree of genetic variation is found between recent CDV strains and the old CDV isolates used in the vaccines and such genetic variation is regarded as a possible cause of the increasing number of CDV-related diseases in dogs. The H gene shows the greatest extent of genetic variation that allows for distinction of various lineages, according to a geographical pattern of distribution and irrespective of the species of identification. In the present study, hemagglutinin (H) genes obtained from field strains detected from clinical specimens of Italian dogs were analyzed genetically. Phylogenetic analysis revealed that a homogeneous group of CDV strains is widespread in Italian dogs, all which are included into the European lineage. Unexpectedly, strains 179/04 and 48/05 clustered along with CDVs of the Arctic lineage, the highest identity being to strain GR88 (98.0 and 98.4%aa, respectively). The full-length sequence of a red fox CDV strain, 207/00 was also determined and analyzed. The H protein of the fox CDV strain was unrelated to strains within the major European lineage. These results suggest that at least three different CDV lineages are present in Italy.

An annotated historical account of canine parvovirus.

A brief annotated history of canine parvovirus-type 2 (CPV-2) and its variants is summarized with emphasis on the most significant contributions of individuals involved in the initial recognition of CPV-2 and subsequent discoveries that have advanced our knowledge of the nature and evolution of this novel canine virus. Time has obscured the observations of many veterinary clinicians and researchers throughout the world who sensed the presence of a new disease when CPV-2 first made its appearance in 1978 and then, within 1-2 years, spread worldwide. Since 1979, nearly 600 articles, papers, numerous text chapters and monographs have been published on the subject of CPV-2. The early history is well known by veterinary infectious diseases specialists and noteworthy publications are recorded on the National Library of Medicine (USA) website, PubMed and in review articles. Because of the great number of publications, it is not practicable to cite them individually; however, reference is made to certain individuals, reviews and selected papers that I consider particularly relevant to the history of progress in the understanding of CPV-2 and the disease it causes. The clinical disease caused by CPV-2 and its variants, the immune response to infection or vaccines, host range and the development of practical diagnostic assays are noted in historical context. The basic biological properties and the physical, molecular and antigenic structure of CPV-2 and its variants are also discussed briefly. Finally, key players who have contributed to the antigenic and DNA sequence (evolutionary) relationships between CPV-2 and the other autonomous parvoviruses of carnivores are noted and hypotheses regarding the origin and evolution of CPV-2 and its variants are mentioned.

Safety and efficacy of a modified-live canine coronavirus vaccine in dogs.

The safety and the efficacy of a modified-live (ML) canine coronavirus (CCoV) vaccine strain 257/98-3c was evaluated in 14 dogs seronegative and virus negative for CCoV. For the safety test, four dogs were inoculated, two by intramuscular and two by oronasal route, with 10 times the vaccinal dose. During the observation period (28 days) all dogs did not display any local or systemic reaction. For the efficacy test, eight dogs were vaccinated by intramuscular (four dogs-group A) or by oronasal route (four dogs-group B). Two dogs were maintained as non-vaccinated controls. In the dogs of group A, vaccinal virus was not detected in faecal samples by virus isolation (VI) and by PCR assay, while in the dogs of group B, the virus was revealed for six median days only by PCR. Twenty-eight days later, the vaccinated and control dogs were challenged with a field CCoV strain. After the challenge, the vaccinated dogs did not display clinical signs and the dogs of group A shed virus for 5.5 median days, evaluated by VI, and for 10 median days evaluated by PCR. Virus shedding was not observed, both by VI and PCR assay, in the dogs of group B. The two control dogs displayed moderate clinical signs and the virus was detected by VI for 14.5 median days starting from day 3 post-challenge (dpc 3) and by PCR assay for 23 median days starting from dpc 1.

Modern veterinary vaccines and the Shaman's apprentice.

This paper is an overview and assessment of new, commercially available veterinary vaccines placed in a historical context. The authors critically evaluate the current state of the field of veterinary vaccines in both food and companion animals and the promises for future vaccine development. The authors maintain that there is considerable variability in safety and sustained efficacy among veterinary vaccines, especially those developed for companion animals. It is proposed that establishment of an international vaccine advisory committee be supported which would function to apprise the veterinary profession of the current status of vaccines and their use.

Severe enteric disease in an animal shelter associated with dual infections by canine adenovirus type 1 and canine coronavirus.

An outbreak of dual infection in dogs with canine adenovirus type 1 (CAV-1) and canine coronavirus (CCV) infection is reported in an animal shelter that comprised approximately 200 adults stray dogs and 30 puppies. Twenty puppies died 7-8 days after the onset of the clinical signs (severe enteritis, leucopoenia, respiratory distress and dehydration). Both CAV-1 and CCV were isolated from tissue or swab samples. Antibodies to CCV and, at high levels, to CAV-1 also were detected in several puppies. The principal histological findings were atrophy of small intestinal villi, lymphoid depletion, hepatitis and bronchopneumonia. The persistence of CCV in the faeces, observed by the polymerase chain reaction assay, was longer than previously reported. Results demonstrated the serious consequences which may occur with dual infections by CAV-1 and CCV in assembled groups of dogs that are housed in poorly managed kennels with inadequate vaccination programmes.

Canine parvovirus (CPV) vaccination: comparison of neutralizing antibody responses in pups after inoculation with CPV2 or CPV2b modified live virus vaccine.

Canine parvovirus type 2 (CPV2) emerged in 1978 as causative agent of a new disease of dogs. New antigenic variants (biotypes), designated CPV2a and CPV2b, became widespread during 1979 to 1980 and 1984, respectively. At the present time the original CPV2 has disappeared in the dog population and has been replaced by the two new viruses. In the present study the comparison of neutralizing antibody titers in two groups of pups (18 pups in each group) inoculated with CPV2 and CPV2b modified live virus vaccines is reported. Using the hemagglutination inhibition (HI) test, relevant differences between antibody titers, against either the homologous or the heterologous virus, were not constantly observed. Using the neutralization (Nt) test, however, the pups inoculated with CPV2 had antibody titers which were approximately 30 times higher to the homologous virus (mean, 4,732) than to the heterologous virus (CPV2b) (mean, 162). The results of these experiments support two conclusions: (i) the HI test may not always accurately evaluate the true immune status of dogs with respect to CPV, and (ii) dogs inoculated with CPV2 vaccine develop relatively low Nt antibody titers against the heterologous virus (CPV2b). These data may suggest an advantage for new vaccines, considering that most presently licensed vaccines are produced with CPV2, which no longer exists in the dog population.

Prey specialization may influence patterns of gene flow in wolves of the Canadian Northwest.

This study characterizes population genetic structure among grey wolves (Canis lupus) in northwestern Canada, and discusses potential physical and biological determinants of this structure. Four hundred and ninety-one grey wolves, from nine regions in the Yukon, Northwest Territories and British Columbia, were genotyped using nine microsatellite loci. Results indicate that wolf gene flow is reduced significantly across the Mackenzie River, most likely due to the north-south migration patterns of the barren-ground caribou herds that flank it. Furthermore, although Banks and Victoria Island wolves are genetically similar, they are distinct from mainland wolf populations across the Amundsen Gulf. However, low-level island-mainland wolf migration may occur in conjunction with the movements of the Dolphin-Union caribou herd. Whereas previous authors have examined isolation-by-distance in wolves, this study is the first to demonstrate correlations between genetic structure of wolf populations and the presence of topographical barriers between them. Perhaps most interesting is the possibility that these barriers reflect prey specialization by wolves in different regions.

A serological survey of minute virus of canines (MVC; canine parvovirus type-1) in dogs in the Tokai area of Japan.

A serological survey for antibodies to minute virus of canines (MVC) by use of a hemagglutination-inhibition (HI) test was performed on sera collected from dogs in the Tokai area of Japan. Forty-one of 266 (15.4%) sera had positive titers of 1:40 or higher against the MVC. Results suggest that MVC may have been present in dogs in Japan since, at least, 1990. From this serosurvey, MVC appears to be established in the dog population in Japan. MVC may have a role as a newly recognized viral pathogen of dogs in Japan.

Canine viral vaccines at a turning point--a personal perspective.

The most important canine viral infections are distemper and CPV-2. Problems of variable CD vaccine safety and efficacy persist, but CD vaccines have greatly reduced the prevalence of disease and cases in vaccinated dogs are now rare. Canine hepatitis (ICH, CAV-1 infection) also has been controlled well by vaccines for more than 35 years and it is now rare; the sporadic cases seen in the 1990s have usually occurred in unvaccinated dogs. CAV-2 vaccines should, therefore, continue to be given since they have proved to be safe and effective, and prevent hepatitis as well as adenoviral tracheobronchitis. Failure to vaccinate would likely result in increase in cases of ICH, a serious disease, but never as significant as distemper and CPV infection. "Are we vaccinating too often?" The question is complex, but the dominant opinion is "yes" (Smith, 1995). The question cannot be responded to unequivocally, however, since manufacturers employ different strains that vary in their immunizing capacity and, probably, duration of immunity. This question was frequent with distemper in the 1960s. At that time, many veterinarians tested batches of the vaccine they used by providing pre- and postvaccinal sera to competent diagnostic laboratories. That practice appeared to benefit veterinarians and dogs, as well as the quality of vaccines. Unfortunately, many owners and some veterinarians seem to hold the view that infectious diseases such as parvovirus infection can be controlled by frequent vaccination alone. The common practice of dog breeders of vaccinating their animals several times each year is senseless. Revaccination for distemper and parvovirus infection is suggested at 1 year of age, but recommendations regarding the frequency of most vaccinations given after that time are unclear. Since most distemper and CPV-2 vaccines probably provide immunity that endures several years, vaccination at 3- to 5-year intervals, after the first year, seems a reasonable practice until more data on duration of immunity become available. "Are too many kinds of vaccines being promoted for dogs?" Distemper and parvovirus vaccines are essential; canine adenovirus vaccines are recommended since the few cases brought to our attention in recent years have been in unvaccinated dogs. Vaccination against respiratory infections is recommended for most dogs, especially those in kennels, or if they are to be boarded. Need has not been clearly established for coronavirus vaccines; Lyme disease vaccines (see below) are useful in preventing illness in areas where the disease exists, but are unnecessary elsewhere since dogs respond rapidly to appropriate antibiotics; current Leptospira bacterins are without benefit since they contain serovars that fail to protect in most areas (noted below). Lyme disease (LD) was not considered here, but newer recombinant (OspA) vaccines are now available that appear to be safe and effective for at least 1 year and they have not caused vaccine-induced postvaccinal lameness, which has been documented with certain whole-cell Lyme disease bacterins. Lyme disease vaccines should be restricted to dogs in, or entering, endemic areas where infested ticks reside. More than 85% of LD cases occur in the mid-Atlantic and Northeastern States, about 10% in six Midwestern states (Michigan, Minnesota, and Wisconsin), and a smaller percentage in restricted areas of northern California and the Pacific Northwest. Leptospirosis also was not discussed here, but vaccines are commonly reported as a cause of anaphylaxis and current vaccines do not contain the serovars prevalent in most regions. The vast majority of cases diagnosed at the New York State Diagnostic Lab at Cornell are grippotyphosa and pomona serovars and there have been no recent cases caused by canicola or icterohemorrhagiae serovars. Because leptospirosis is an important disease of dogs, there is an urgent need for more research and the development of safer vaccines that contain the prevalent

Survey on viral pathogens in wild red foxes (Vulpes vulpes) in Germany with emphasis on parvoviruses and analysis of a DNA sequence from a red fox parvovirus.

The seroprevalence of canine parvovirus (CPV), canine distemper virus (CDV), canine adenovirus (CAV) and canine herpesvirus (CHV) infections in red foxes (Vulpes vulpes) was determined in fox sera collected between 1991 and 1995. A total of 500 sera were selected and the seroprevalences were estimated to be 13% (65 of 500 sera) for CPV, 4.4% (17 of 383 sera) for CDV, 35% (17 of 485 sera) for CAV, and 0.4% (2 of 485 sera) for CHV, respectively. No statistically significant differences were observed between the two (rural and suburban) areas under study. Parvovirus DNA sequences were amplified from tissues of free-ranging foxes and compared to those of prototype viruses from dogs and cats. We report here a parvovirus sequence indicative of a true intermediate between the feline panleukopenia virus-like viruses and the canine parvovirus-like viruses. The red fox parvoviral sequence, therefore, appears to represent a link between those viral groups. The DNA sequence together with a significant seroprevalence of parvovirus infections in foxes supports the hypothesis that the sudden emergence of canine parvovirus in the domestic dog population may have involved the interspecies transmission between wild and domestic carnivores.

Assessment of immunization response to canine distemper virus vaccination in puppies using a clinic-based enzyme-linked immunosorbant assay.

To study the response to vaccination, an enzyme-linked immunosorbant assay (ELISA) immunoblot method was developed and tested to assay canine distemper virus (CDV) IgG antibody in puppies and compared to a standard virus neutralization (VN) test (r2 = 0.748). Ten litters of four puppies each were used in a vaccination study. Seventy-six percent of vaccinated puppies immunized with a modified live vaccine were successfully protected against CDV at 6 weeks of age. One puppy remained seronegative after vaccination at 6 and 9 weeks of age. This is the first report of vaccination responses of puppies to CDV using an in-clinic test kit based on solid-phase immunoassay technology.

Assessment of maternal antibody decay and response to canine parvovirus vaccination using a clinic-based enzyme-linked immunosorbent assay.

Interference caused by maternal antibodies is considered a major cause of canine parvovirus (CPV) vaccination failure. In this study, an immunoblot clinic-based enzyme-linked immunosorbent assay (ELISA) method was used to detect CPV antibodies in sera of pregnant bitches and their offspring to study the response of pups to vaccination. With a easily accessible procedure for CPV antibody determination, the veterinarian should be able to gauge the response of pups after vaccination. The validity of the technique was tested in parallel against the standard hemagglutination inhibition (HI) test. Results of the ELISA were correlated with those of the standard HI method for quantification of CPV antibodies. With the ELISA, successfully immunized pups were identified, allowing for a more reliable and cost-effective program of vaccination. This simple clinic-based test could be used for the assessment of vaccination status of pups during the critical phase of 6 to about 16 weeks of age. This study is the first in which vaccination response to CPV in pups was followed, using a clinic-based ELISA for CPV antibody monitoring.

[The "other" parvovirus: first description of the minute virus of canines (Canine parvovirus type 1) in Germany]. / Das "andere" Parvovirus: Erstbeschreibung des Minute Virus of Canines (canines Parvovirus Typ 1) in Deutschland.

During an investigation of a late abortion in a Yorkshire terrier minute virus of canines (MVC) antigen could be demonstrated in fetal tissues by immunofluorescence. The bitch had a high specific anti-MVC serum titer when tested about four weeks after the abortion. Those results implicate an etiological role of MVC in this abortion and to our knowledge it presents the first described case of a MVC-associated abortion in Germany.

Canine brucellosis: a diagnostician's dilemma.

Salient features of brucellosis in dogs caused by Brucella canis are briefly reviewed, with emphasis on problems and pitfalls in the serodiagnosis of the disease. Procedures available to veterinarians for the diagnosis of canine brucellosis are discussed from the point of view of test sensitivity and specificity. The serodiagnosis of the disease poses a particular dilemma because several tests in current use by diagnostic laboratories have not been evaluated critically and may provide false-positive results. Blood cultures should be required of dogs who have not received antibiotics before a positive diagnosis is rendered. Expertise is required for the preparation of diagnostic antigens and in the interpretation of tests. Accurate diagnosis is essential because the diagnosis of brucellosis in a kennel often results in the depopulation of many or all dogs.

Minute virus of canines (MVC, canine parvovirus type-1): pathogenicity for pups and seroprevalence estimate.

Minute virus of canines (MVC, canine parvovirus type-1) caused inapparent to severe illness in neonatal specific-pathogen-free pups exposed by the oronasal route. The experimental disease was generally mild. Four of 21 infected pups had clinical signs of respiratory illness, but only 2 pups, not euthanized during the early postinoculation period, developed severe illness or died. Principal pathologic changes included bronchitis and interstitial pneumonia with various degrees of lymphadenitis. In contrast to the reported field cases, enteric signs were absent in the experimentally infected animals. Histopathologic changes in the small intestine were mild or absent. Bronchial, bronchiolar, and alveolar epithelial cells appeared to be the sites of initial and most extensive viral growth, reflecting the pattern of histopathologic changes. The disease caused by MVC was mild in comparison to that caused by canine parvovirus-type 2. MVC now appears to be established as a cause of illness in young pups and of transplacental infections with embryo resorption. The prevalence of MVC hemagglutination-inhibiting antibodies was high (approximately 50%) in adult dog sera from widely separated geographic areas of the United States.

Virus reactivation in bitches with a medical history of herpesvirus infection.

Virologic and pathologic investigations were done on prednisolone-treated bitches with a history of canine herpesvirus (CHV) infection. Reactivation of CHV was demonstrated in 5 Beagle bitches after daily administration of 600 mg of prednisolone for 5 days. The reactivation was confirmed in 4 of 5 bitches. Canine herpesvirus was recovered from nasal, oral, vaginal, and ocular secretions on the 5th to 21st days after initiation of treatment with prednisolone, and also from nasal mucosa and tonsil tissues. Results indicated that latent CHV infections develop and that the virus may be reactivated, without clinical signs, in dogs with a history of CHV infection.