-Feline calicivirus (FCV) is an important and highly prevalent pathogen of cats. It belongs to the family Caliciviridae which includes other significant pathogens of man and animals. As an RNA virus, high polymerase error rates convey upon FCV a high genome plasticity, and allow the virus to respond rapidly to environmental selection pressures. This makes the virus very adaptable and has important implications for clinical disease and its control. Being genetically diverse, FCV is associated with a range of clinical syndromes from inapparent infections to relatively mild oral and upper respiratory tract disease with or without acute lameness. More recently, highly virulent forms of the virus have emerged associated with a systemic infection that is frequently fatal. A proportion of FCV infected cats that recover from acute disease, remain persistently infected. In such cats, virus evolution is believed to help the virus to evade the host immune response. Such longterm carriers may only represent a minority of the feline population but are likely to be crucial to the epidemiology of the virus. Vaccination against FCV has been available for many years and has effectively reduced the incidence of clinical disease. However, the vaccines do not prevent infection and vaccinated cats can still become persistently infected. In addition, FCV strain variability means that not all strains are protected against equally. Much progress has been made in understanding the biology and pathogenesis of this important feline virus. Challenges for the future will necessarily focus on how to control the variability of this virus particularly in relation to emerging virulent strains and vaccination.
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 degrees 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.
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.The Caliciviridae are an important group of human and animal RNA pathogens, causing a wide range of diseases, including acute outbreaks of gastroenteritis in humans (noroviruses and sapoviruses) and vesicular and other diseases in animals (vesiviruses and lagoviruses) (19). The Caliciviridae are a highly variable family of small positive-strand RNA viruses, demonstrating considerable antigenic and genetic diversity both between and within genera. Such variability has been associated with the emergence of highly transmissible globally dominant strains of human caliciviruses (36) and hypervirulent animal caliciviruses that are frequently lethal (9,33,39). Despite the obvious significance of such variation, the origins of this diversity and the evolutionary mechanisms by which new, and possibly more virulent strains evolve remain unclear.Feline calicivirus (FCV) belongs to the genus Vesivirus and is a highly infectious oral and respiratory pathogen of domestic cats (18). Following acute infection, some cats remain persistently infected with the virus (11,40,48,59). Such carriers appear to be relatively common in the general population, with prevalences ranging from 15 to 91%, and they play an important role in the epidemiolog...
Following the COVID‐19 pandemic, psychological therapies rapidly moved online in mid‐2020. The Association for Family Therapy and Systemic Practice in the UK (AFT) surveyed the attitudes and practices of systemic therapists in the UK in early October 2020, exploring members’ views and gathered information about ongoing needs. A sample of 312 people were included in a mixed methods analysis. In total, 65% of respondents felt their overall experience of using online video technology professionally was positive, further reflected in responses to two open‐ended questions. Detailed thematic analysis revealed that many positive comments were related to the practical advantages of online working, whilst many negative comments were related to technique and the therapeutic relationship. Possible respondent biases are discussed, and the implications of this change in practice are explored. It remains to be seen if this marks the beginning of a more permanent shift in our field as we explore the potential of new technologies. Practitioner Points The vast majority of UK systemic therapists felt that their experience of online video technology was positive. They noted many practical advantages but also identified many challenges regarding therapeutic techniques and the therapeutic relationship. Therapists developed a range of creative solutions to maximise the therapeutic opportunities of online video.
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