Karen P. Coyne

Lethal outbreak of disease associated with feline calicivirus infection in cats

Recently, in the USA, virulent mutants of feline calicivirus (FCV) have been identified as the cause of a severe and acute virulent systemic disease, characterised by jaundice, oedema and high mortality in groups of cats. This severe manifestation of FCV disease has so far only been reported in the USA. However, in 2003, an outbreak of disease affected a household of four adult cats and an adult cat from a neighbouring household in the UK. Three of the adult cats in the household and the neighbouring cat developed clinical signs including pyrexia (39·5 to 40·5°C), lameness, voice loss, inappetence and jaundice. One cat was euthanased in extremis, two died and one recovered. A postmortem examination of one of the cats revealed focal cellulitis around the right hock and right elbow joints. The principal finding of histopathological examinations of selected organs from two of the cats was disseminated hepatocellular necrosis with mild inflammatory infiltration. Immunohistology identified FCV antigen in parenchymal and Kupffer cells in the liver of both animals and in alveolar macrophages of one of them. In addition, calicivirus-like particles were observed by electron microscopy within the hepatocytes of one cat. FCV was isolated from two of the dead cats and from the two surviving cats. Sequence analysis showed that they were all infected with the same strain of virus, but that it was different from strains of FCV associated with the virulent systemic disease in cats in the USA. The outbreak was successfully controlled by quarantine in the owner’s house.

Family Pet Ownership during Childhood: Findings from a UK Birth Cohort and Implications for Public Health Research

In developed nations, approximately half of household environments contain pets. Studies of Human-Animal Interaction (HAI) have proposed that there are health benefits and risks associated with pet ownership. However, accurately demonstrating and understanding these relationships first requires a better knowledge of factors associated with ownership of different pet types. A UK birth cohort, the Avon Longitudinal Study of Parents and Children (ALSPAC), were used to collect pet ownership data from the mothers, from gestation to child age 10 years old. 14,663 children were included in the study, of which mothers of 13,557 reported pet information at gestation, and 7,800 by age 10. Pet types recorded include cat, dog, rabbit, rodent, bird, fish and tortoise/turtle. The dataset also contains a number of demographic, socioeconomic and behavioural variables relevant to human health behaviour. Logistic regression was used to build multivariable models for ownership of each pet type at age 7 years. Family pet ownership increased during childhood, in particular rabbits, rodents and fish. A number of socioeconomic and demographic factors were associated with ownership of different pet types and the effects differed depending on the pet type studied. Variables which require consideration by researchers include gender, presence of older siblings, ethnicity, maternal and paternal education, maternal and paternal social class, maternal age, number of people in the household, house type, and concurrent ownership of other pets. Whether the mother had pets during her childhood was a strong predictor of pet ownership in all models. In HAI studies, care should be taken to control for confounding factors, and to treat each pet type individually. ALSPAC and other similar birth cohorts can be considered a potential resource for research into the effects of pet ownership during childhood.

Evolutionary Mechanisms of Persistence and Diversification of a Calicivirus within Endemically Infected Natural Host Populations

ABSTRACT In order to understand the evolutionary mechanisms of persistence and diversification within the Caliciviridae, we have been exploiting endemic infection of feline calicivirus within five geographically distinct household groups of cats. By sequencing immunodominant and variable regions of the capsid gene, we identified the relative contribution of the different evolutionary processes employed by the virus to ensure its long-term survival in the host population. Such strategies included progressive evolution of a given variant of a strain through mutation accumulation within an individual, sequential reinfection with either a variant of the same strain or with a different strain, and mixed infection. Recombination between different strains in this study has been reported in detail elsewhere (K. P. Coyne et al., J. Gen. Virol. 87:921-926, 2006). Here, we provide evidence to suggest that true long-term persistent infection in individuals is relatively rare, with the majority of apparent viral carriers undergoing a combination of progressive evolution and cyclical reinfection. Progressive evolution at the individual level and variant reinfection at both the individual and population levels were associated with positive selection. Two measures of evolution rate were determined; for a virus progressively evolving within an individual (1.32 × 10−2 to 2.64 × 10−2 substitutions per nucleotide per year, i.e., no transmission) and for a strain circulating within a population (3.84 × 10−2 to 4.56 × 10−2 substitutions per nucleotide per year, i.e., including transmission). Reiteration of both progressive evolution and variant reinfection appeared to lead to a gradual increase in the diversity of a given strain of virus, both in the individual and in the population, until eventually new strains emerged.

Long-term analysis of feline calicivirus prevalence and viral shedding patterns in naturally infected colonies of domestic cats.

Abstract Feline calicivirus (FCV) is a highly infectious respiratory pathogen of domestic cats. The prevalence of FCV in the general cat population is high, particularly in multi-cat households, largely because many clinically recovered cats remain persistently infected carriers. In order to assess how FCV circulates in such groups and to assess the contribution that each individual animal makes to the epidemiology of the disease, we have carried out the first detailed analysis of long-term shedding patterns of FCV in individual cats within naturally infected colonies. The prevalence of FCV in each of the groups on individual sampling occasions ranged from 0% to 91%, with averages for the individual colonies ranging from 6% to 75%. Within each of the colonies, one to three distinct strains of FCV were identified. Individual cats showed a spectrum of FCV shedding patterns over the sampling period which broadly grouped into three categories: those that shed virus relatively consistently, those that shed virus intermittently, and those that appeared never to shed virus. This is the first report identifying non-shedder cats that appear resistant to FCV infection over long periods of time, despite being continually exposed to virus. Such resistance appeared to be age related, which may have been immune-mediated, although by analogy with other caliciviruses, factors such as host genetic resistance may play a role. Given that a proportion of the population appears to be resistant to infection, clearly the cohort of cats that consistently shed virus are likely to provide an important mechanism whereby infection can be maintained in small populations.

Antibacterial prescribing patterns in small animal veterinary practice identified via SAVSNET: the small animal veterinary surveillance network.

In this study, data from veterinary clinical records were collected via the small animal veterinary surveillance network (SAVSNET). Over a three-month period, data were obtained from 22,859 consultations at 16 small animal practices in England and Wales: 69 per cent from dogs, 24 per cent from cats, 3 per cent from rabbits and 4 per cent from miscellaneous species. The proportion of consults where prescribing of antibacterials was identified was 35.1 per cent for dogs, 48.5 per cent for cats and 36.6 per cent for rabbits. Within this population, 76 per cent of antibacterials prescribed were β-lactams, including the most common group of clavulanic acid-potentiated amoxicillin making up 36 per cent of the antibacterials prescribed. Other classes included lincosamides (9 per cent), fluoroquinolones and quinolones (6 per cent) and nitroimidazoles (4 per cent). Vancomycin and teicoplanin (glycopeptide class), and imipenem and meropenem (β-lactam class) prescribing was not identified. Prescribing behaviour varied between practices. For dogs and cats, the proportion of consults associated with the prescription of antibacterials ranged from 0.26 to 0.55 and 0.41 to 0.73, respectively.

High Genetic Diversity of the Immunodominant Region of the Feline Calicivirus Capsid Gene in Endemically Infected Cat Colonies

Feline calicivirus (FCV) is an important pathogen of domestic cats. In this study, we have determined the genetic diversity of FCV within four geographically separate colonies of endemically infected cats by sequencing the immunodominant and variable region E of the capsid gene. Comparison of isolates between colonies and between unrelated published sequences gave nucleotide distance values of 26–35% and 22–40%, respectively and suggested each colony was infected with a distinct virus strain. Comparison of isolates within individual endemically infected colonies showed nucleotide distance variability of 0–16%. This was greater than distances previously reported for epidemiologically related isolates from cases of acute disease (0–5%) and was consistent with the evolution of FCV from a single distinct ancestor sequence in each colony. The pattern of nucleotide substitutions generating the observed intra-colony diversity was associated with strong evidence for positive selection acting on immunodominant regions of the FCV capsid protein. We suggest that endemically infected colonies of cats may be important generators of genetic diversity for FCV and that this may ultimately lead to the generation of new strains.

Molecular Epidemiology and Phylogeny Reveal Complex Spatial Dynamics in Areas Where Canine Parvovirus Is Endemic

ABSTRACT Canine parvovirus type 2 (CPV-2) is a severe enteric pathogen of dogs, causing high mortality in unvaccinated dogs. After emerging, CPV-2 spread rapidly worldwide. However, there is now some evidence to suggest that international transmission appears to be more restricted. In order to investigate the transmission and evolution of CPV-2 both nationally and in relation to the global situation, we have used a long-range PCR to amplify and sequence the full VP2 gene of 150 canine parvoviruses obtained from a large cross-sectional sample of dogs presenting with severe diarrhea to veterinarians in the United Kingdom, over a 2-year period. Among these 150 strains, 50 different DNA sequence types (S) were identified, and apart from one case, all appeared unique to the United Kingdom. Phylogenetic analysis provided clear evidence for spatial clustering at the international level and for the first time also at the national level, with the geographical range of some sequence types appearing to be highly restricted within the United Kingdom. Evolution of the VP2 gene in this data set was associated with a lack of positive selection. In addition, the majority of predicted amino acid sequences were identical to those found elsewhere in the world, suggesting that CPV VP2 has evolved a highly fit conformation. Based on typing systems using key amino acid mutations, 43% of viruses were CPV-2a, and 57% CPV-2b, with no type 2 or 2c found. However, phylogenetic analysis suggested complex antigenic evolution of this virus, with both type 2a and 2b viruses appearing polyphyletic. As such, typing based on specific amino acid mutations may not reflect the true epidemiology of this virus. The geographical restriction that we observed both within the United Kingdom and between the United Kingdom and other countries, together with the lack of CPV-2c in this population, strongly suggests the spread of CPV within its population may be heterogeneously subject to limiting factors. This cross-sectional study of national and global CPV phylogeographic segregation reveals a substantially more complex epidemic structure than previously described.

Canine parvovirus in asymptomatic feline carriers

Canine parvovirus (CPV) and feline panleukopaenia virus (FPLV) are two closely related viruses, which are known to cause severe disease in younger unvaccinated animals. As well as causing disease in their respective hosts, CPV has recently acquired the feline host range, allowing it to infect both cats and dogs. As well as causing disease in dogs, there is evidence that under some circumstances CPV may also cause disease in cats. This study has investigated the prevalence of parvoviruses in the faeces of clinically healthy cats and dogs in two rescue shelters. Canine parvovirus was demonstrated in 32.5% (13/50) of faecal samples in a cross sectional study of 50 cats from a feline only shelter, and 33.9% (61/180) of faecal samples in a longitudinal study of 74 cats at a mixed canine and feline shelter. Virus was isolated in cell cultures of both canine and feline origin from all PCR-positive samples suggesting they contained viable, infectious virus. In contrast to the high CPV prevalence in cats, no FPLV was found, and none of 122 faecal samples from dogs, or 160 samples collected from the kennel environment, tested positive for parvovirus by PCR. Sequence analysis of major capsid VP2 gene from all positive samples, as well as the non-structural gene from 18 randomly selected positive samples, showed that all positive cats were shedding CPV2a or 2b, rather than FPLV. Longitudinally sampling in one shelter showed that all cats appeared to shed the same virus sequence type at each date they were positive (up to six weeks), despite a lack of clinical signs. Fifty percent of the sequences obtained here were shown to be similar to those recently obtained in a study of sick dogs in the UK (Clegg et al., 2011). These results suggest that in some circumstances, clinically normal cats may be able to shed CPV for prolonged periods of time, and raises the possibility that such cats may be important reservoirs for the maintenance of infection in both the cat and the dog population.

Cross-sectional survey of antimicrobial prescribing patterns in UK small animal veterinary practice

The increase in the prevalence of antimicrobial resistance has resulted in both human and veterinary antimicrobial use coming under increased scrutiny. The aim of this study was to characterise antimicrobial prescribing patterns in small-animal veterinary practices in the UK. A cross-sectional survey of UK small animal veterinarians was undertaken. A postal questionnaire to evaluate antimicrobial prescribing habits was sent to 900 clinicians. Data were collected on the clinicians, their practices and their sources of information regarding antimicrobials and their use. Respondents were asked if they would prescribe antimicrobials to animals described in four clinical scenarios, and, if so, to provide details of the prescription(s). Questionnaires were completed by 51% of the veterinarians. Only 3.5% of clinicians reported that their practice had an antimicrobial use policy. Penicillins were most commonly prescribed in three clinical scenarios, and 1st generation cephalosporins were most commonly prescribed in a scenario about canine pyoderma. In one scenario, fluoroquinolones and 3rd generation cephalosporins accounted for 10% and 13% of prescriptions respectively. Five percent of all prescriptions were under the recommended dose and 20% were over the recommended dose. Overall, 2.3% of prescriptions were not licensed for use in dogs or cats in the UK. Associations between the use of various antimicrobial drugs and independent variables were analysed using multivariable logistic regression models. Off-license prescriptions and inaccurate dosing of antimicrobials by small-animal clinicians in the UK appears to occur. Antimicrobial use guidelines are rare in small animal practice. The introduction of such guidelines has been shown to lead to more appropriate use of antimicrobials and is therefore recommended.

Large-Scale Spatial and Temporal Genetic Diversity of Feline Calicivirus

ABSTRACT Feline calicivirus (FCV) is an important pathogen of domestic cats and a frequently used model of human caliciviruses. Here we use an epidemiologically rigorous sampling framework to describe for the first time the phylodynamics of a calicivirus at regional and national scales. A large number of FCV strains cocirculated in the United Kingdom at the national and community levels, with no strain comprising more than 5% and 14% of these populations, respectively. The majority of strains exhibited a relatively restricted geographical range, with only two strains (one field virus and one vaccine virus) spreading further than 100 km. None of the field strains were identified outside the United Kingdom. Temporally, while some strains persisted locally for the majority of the study, others may have become locally extinct. Evolutionary analysis revealed a radial phylogeny with little bootstrap support for nodes above the strain level. In most cases, spatially and temporally diverse strains intermingled in the phylogeny. Together, these data suggest that current FCV evolution is not associated with selective competition among strains. Rather, the genetic and antigenic landscape in each geographical location is highly complex, with many strains cocirculating. These variants likely exist at the community level by a combination of de novo evolution and occasional gene flow from the wider national population. This complexity provides a benchmark, for the first time, against which vaccine cross-protection at both local and national levels can be judged.