Christine Gibbs.

A pioneer of veterinary radiology, she was a born teacher and a role model.

Influence of living in a multicat household on health and behaviour in a cohort of cats from the United Kingdom.

BACKGROUND: Living in a multicat household has been implicated as a risk factor for various feline issues, but evidence is often anecdotal or based on retrospective studies. METHODS: Data from the Bristol Cats Study, a UK longitudinal study of pet cats, were used. Cats were included if they had remained in either a single cat or multicat household between questionnaires 1 (two months old to four months old) and 5 (two-and-a-half years old). Univariable and multivariable logistic regression models were used to analyse associations between single cat/multicat households and measures of health and behaviour (overweight/obesity, abscesses/cat bites, negative interactions with owner and periuria). Multicat households were also subcategorised according to whether owners had reported agonistic behaviour between household cats. RESULTS: There was no evidence of association between household type and the likelihood of obesity, abscesses or periuria. The likelihood of negative interactions with the owner (eg, growling or hissing) was influenced by the cats' relationships; cats in non-agonistic multicat households had decreased odds of negative interactions with the owner, compared with single and agonistic multicat households (P<0.001). CONCLUSION: Living in a multicat households per se was not a risk factor for the health and behaviour issues investigated, but the intercat relationship is important.

Feline thyroid carcinoma: diagnosis and response to high-dose radioactive iodine treatment.

This study reports the scintigraphy, histopathology, sole treatment with high-dose radioactive iodine and outcome of eight cases of feline thyroid carcinoma. Scintigraphic findings were variable and in 7/8 cases scintigraphic features could not reliably distinguish whether the thyroid tissue was malignant. Histopathology revealed typical criteria of malignancy in all cases, with mitotic activity described most frequently (7/8 cases), followed by infiltration of local tissues (4/8 cases). Cellular pleomorphism was infrequently observed. Single high-dose (1100MBq I(131)) radioiodine therapy was successful in 6/8 cases, with complete resolution of hyperthyroidism, and was associated with prolonged survival times (181-2381 days). Sole treatment with high-dose radioiodine is a safe and effective treatment for functional thyroid carcinoma. The prognosis for feline thyroid carcinoma successfully treated with radioiodine is good, with extended survival times commonly achieved.

Feline panleukopenia. ABCD guidelines on prevention and management.

OVERVIEW: Feline panleukopenia virus (FPV) infects all felids as well as raccoons, mink and foxes. This pathogen may survive in the environment for several months and is highly resistant to some disinfectants. INFECTION: Transmission occurs via the faecal-oral route. Indirect contact is the most common route of infection, and FPV may be carried by fomites (shoes, clothing), which means indoor cats are also at risk. Intrauterine virus transmission and infection of neonates can occur. DISEASE SIGNS: Cats of all ages may be affected by FPV, but kittens are most susceptible. Mortality rates are high - over 90% in kittens. Signs of disease include diarrhoea, lymphopenia and neutropenia, followed by thrombocytopenia and anaemia, immunosuppression (transient in adult cats), cerebellar ataxia (in kittens only) and abortion. DIAGNOSIS: Feline panleukopenia virus antigen is detected in faeces using commercially available test kits. Specialised laboratories carry out PCR testing on whole blood or faeces. Serological tests are not recommended, as they do not distinguish between infection and vaccination. DISEASE MANAGEMENT: Supportive therapy and good nursing significantly decrease mortality rates. In cases of enteritis, parenteral administration of a broad-spectrum antibiotic is recommended. Disinfectants containing sodium hypochlorite (bleach), peracetic acid, formaldehyde or sodium hydroxide are effective. VACCINATION RECOMMENDATIONS: All cats - including indoor cats - should be vaccinated. Two injections, at 8-9 weeks of age and 3-4 weeks later, are recommended, and a first booster 1 year later. A third vaccination at 16-20 weeks of age is recommended for kittens from environments with a high infection pressure (cat shelters) or from queens with high vaccine-induced antibody levels (breeding catteries). Subsequent booster vaccinations should be administered at intervals of 3 years or more. Modified-live virus vaccines should not be used in pregnant queens or in kittens less than 4 weeks of age.

Feline herpesvirus infection. ABCD guidelines on prevention and management.

OVERVIEW: Feline viral rhinotracheitis, caused by feline herpesvirus (FHV), is an upper respiratory tract disease that is often associated with feline calicivirus and bacteria. In most cats, FHV remains latent after recovery, and they become lifelong virus carriers. Stress or corticosteroid treatment may lead to virus reactivation and shedding in oronasal and conjunctival secretions. INFECTION: Sick cats shed FHV in oral, nasal and conjunctival secretions; shedding may last for 3 weeks. Infection requires direct contact with a shedding cat. DISEASE SIGNS: Feline herpesvirus infections cause acute rhinitis and conjunctivitis, usually accompanied by fever, depression and anorexia. Affected cats may also develop typical ulcerative, dendritic keratitis. DIAGNOSIS: Samples consist of conjunctival, corneal or oropharyngeal swabs, corneal scrapings or biopsies. It is not recommended that cats recently vaccinated with a modified-live virus vaccine are sampled. Positive PCR results should be interpreted with caution, as they may be produced by low-level shedding or viral latency. DISEASE MANAGEMENT: 'Tender loving care' from the owner, supportive therapy and good nursing are essential. Anorexic cats should be fed blended, highly palatable food - warmed up if required. Mucolytic drugs (eg, bromhexine) or nebulisation with saline may offer relief. Broad-spectrum antibiotics should be given to prevent secondary bacterial infections. Topical antiviral drugs may be used for the treatment of acute FHV ocular disease. The virus is labile and susceptible to most disinfectants, antiseptics and detergents. VACCINATION RECOMMENDATIONS: Two injections, at 9 and 12 weeks of age, are recommended, with a first booster 1 year later. Boosters should be given annually to at-risk cats. For cats in low-risk situations (eg, indoor-only cats), 3-yearly intervals suffice. Cats that have recovered from FHV-associated disease are usually not protected for life against further disease episodes; vaccination of recovered cats is therefore recommended.

Feline calicivirus infection. ABCD guidelines on prevention and management.

OVERVIEW: Feline calicivirus (FCV) is a highly variable virus. More severe, systemic forms of FCV infection have been observed recently. INFECTION: Sick, acutely infected or carrier cats shed FCV in oronasal and conjunctival secretions. Infection occurs mainly through direct contact. DISEASE SIGNS: The main clinical signs are oral ulcers, upper respiratory signs and a high fever. Feline calicivirus may be isolated from nearly all cats with chronic stomatitis or gingivitis. Cats with 'virulent systemic FCV disease' variably show pyrexia, cutaneous oedema, ulcerative lesions on the head and limbs, and jaundice. Mortality is high and the disease is more severe in adult cats. DIAGNOSIS: Diagnosis of FCV can be achieved by virus isolation or reverse-transcriptase PCR. Viral RNA can be detected in conjunctival and oral swabs, blood, skin scrapings or lung tissue using PCR. Positive PCR results should be interpreted with caution, as these may be a consequence of low-level shedding by persistently infected carriers. The diagnosis of virulent systemic FCV disease relies on clinical signs and isolation of the same strain from the blood of several diseased cats. DISEASE MANAGEMENT: Supportive therapy (including fluid therapy) and good nursing care are essential. Anorexic cats should be fed highly palatable, blended or warmed food. Mucolytic drugs (eg, bromhexine) or nebulisation with saline may offer relief. Broad-spectrum antibiotics may be administered to prevent secondary bacterial infections. Feline calicivirus can persist in the environment for about 1 month and is resistant to many common disinfectants. VACCINATION RECOMMENDATIONS: Two injections, at 9 and 12 weeks of age, are recommended, followed by a first booster 1 year later. In high-risk situations, a third vaccination at 16 weeks is recommended. Boosters should be given every 3 years. However, cats in high-risk situations should be revaccinated annually. Cats that have recovered from caliciviral disease are probably not protected for life, particularly if infected with different strains. Vaccination of these cats is still recommended.

Feline leukaemia. ABCD guidelines on prevention and management.

OVERVIEW: Feline leukaemia virus (FeLV) is a retrovirus that may induce depression of the immune system, anaemia and/or lymphoma. Over the past 25 years, the prevalence of FeLV infection has decreased considerably, thanks both to reliable tests for the identification of viraemic carriers and to effective vaccines. INFECTION: Transmission between cats occurs mainly through friendly contacts, but also through biting. In large groups of non-vaccinated cats, around 30-40% will develop persistent viraemia, 30-40% show transient viraemia and 20-30% seroconvert. Young kittens are especially susceptible to FeLV infection. DISEASE SIGNS: The most common signs of persistent FeLV viraemia are immune suppression, anaemia and lymphoma. Less common signs are immune-mediated disease, chronic enteritis, reproductive disorders and peripheral neuropathies. Most persistently viraemic cats die within 2-3 years. DIAGNOSIS: In low-prevalence areas there may be a risk of false-positive results; a doubtful positive test result in a healthy cat should therefore be confirmed, preferably by PCR for provirus. Asymptomatic FeLV-positive cats should be retested. DISEASE MANAGEMENT: Supportive therapy and good nursing care are required. Secondary infections should be treated promptly. Cats infected with FeLV should remain indoors. Vaccination against common pathogens should be maintained. Inactivated vaccines are recommended. The virus does not survive for long outside the host. VACCINATION RECOMMENDATIONS: All cats with an uncertain FeLV status should be tested prior to vaccination. All healthy cats at potential risk of exposure should be vaccinated against FeLV. Kittens should be vaccinated at 8-9 weeks of age, with a second vaccination at 12 weeks, followed by a booster 1 year later. The ABCD suggests that, in cats older than 3-4 years of age, a booster every 2-3 years suffices, in view of the significantly lower susceptibility of older cats.

Feline rabies. ABCD guidelines on prevention and management.

OVERVIEW: Rabies virus belongs to the genus Lyssavirus, together with European bat lyssaviruses 1 and 2. In clinical practice, rabies virus is easily inactivated by detergent-based disinfectants. INFECTION: Rabid animals are the only source of infection. Virus is shed in the saliva some days before the onset of clinical signs and transmitted through a bite or a scratch to the skin or mucous membranes. The average incubation period in cats is 2 months, but may vary from 2 weeks to several months, or even years. DISEASE SIGNS: Any unexplained aggressive behaviour or sudden behavioural change in cats must be considered suspicious. Two disease manifestations have been identified in cats: the furious and the dumb form. Death occurs after a clinical course of 1-10 days. DIAGNOSIS: A definitive rabies diagnosis is obtained by post-mortem laboratory investigation. However, serological tests are used for post-vaccinal control, especially in the context of international movements. DISEASE MANAGEMENT: Post-exposure vaccination of cats depends on the national public health regulations, and is forbidden in many countries. VACCINATION RECOMMENDATIONS: A single rabies vaccination induces a long-lasting immunity. Kittens should be vaccinated at 12-16 weeks of age to avoid interference from maternally derived antibodies and revaccinated 1 year later. Although some vaccines protect against virulent rabies virus challenge for 3 years or more, national or local legislation may call for annual boosters.

Feline immunodeficiency. ABCD guidelines on prevention and management.

OVERVIEW: Feline immunodeficiency virus (FIV) is a retrovirus closely related to human immunodeficiency virus. Most felids are susceptible to FIV, but humans are not. Feline immunodeficiency virus is endemic in domestic cat populations worldwide. The virus loses infectivity quickly outside the host and is susceptible to all disinfectants. INFECTION: Feline immunodeficiency virus is transmitted via bites. The risk of transmission is low in households with socially well-adapted cats. Transmission from mother to kittens may occur, especially if the queen is undergoing an acute infection. Cats with FIV are persistently infected in spite of their ability to mount antibody and cell-mediated immune responses. DISEASE SIGNS: Infected cats generally remain free of clinical signs for several years, and some cats never develop disease, depending on the infecting isolate. Most clinical signs are the consequence of immunodeficiency and secondary infection. Typical manifestations are chronic gingivostomatitis, chronic rhinitis, lymphadenopathy, weight loss and immune-mediated glomerulonephritis. DIAGNOSIS: Positive in-practice ELISA results obtained in a low-prevalence or low-risk population should always be confirmed by a laboratory. Western blot is the 'gold standard' laboratory test for FIV serology. PCR-based assays vary in performance. DISEASE MANAGEMENT: Cats should never be euthanased solely on the basis of an FIV-positive test result. Cats infected with FIV may live as long as uninfected cats, with appropriate management. Asymptomatic FIV-infected cats should be neutered to avoid fighting and virus transmission. Infected cats should receive regular veterinary health checks. They can be housed in the same ward as other patients, but should be kept in individual cages. VACCINATION RECOMMENDATIONS: At present, there is no FIV vaccine commercially available in Europe. Potential benefits and risks of vaccinating FIV-infected cats should be assessed on an individual cat basis. Needles and surgical instruments used on FIV-positive cats may transmit the virus to other cats, so strict hygiene is essential.

Chlamydophila felis infection. ABCD guidelines on prevention and management.

OVERVIEW: Chlamydophila felis is a Gram-negative bacterium and its primary target is the conjunctiva. The bacterium does not survive outside the host. INFECTION: Transmission requires close contact between cats; ocular secretions are probably the most important body fluid for infection. Most cases occur in cats under 1 year of age. Chlamydophila felis is the infectious organism most frequently associated with conjunctivitis. DISEASE SIGNS: Unilateral ocular disease generally progresses to become bilateral. There can be intense conjunctivitis with extreme hyperaemia of the nictitating membrane, blepharospasm and ocular discomfort. Transient fever, inappetence and weight loss may occur shortly after infection, although most cats remain well and continue to eat. DIAGNOSIS: PCR techniques are now preferred for diagnosing C felis infection. Ocular swabs are generally used. In unvaccinated cats, antibody detection can be used to indicate infection. DISEASE MANAGEMENT: Tetracyclines are generally regarded as the antibiotics of choice. Doxycycline has the advantage of requiring only single daily administration and is given at a dose of 10 mg/kg orally. Vaccination should be considered if there is a history of confirmed chlamydial disease in a shelter. Single housing and routine hygiene measures should suffice to avoid cross-infection. Cats maintained together for longer terms should be vaccinated regularly. In breeding catteries where C felis infection is endemic, the first step should be to treat all cats with doxycycline for at least 4 weeks. Once clinical signs have been controlled, the cats should be vaccinated. VACCINATION RECOMMENDATIONS: Vaccination should be considered for cats at risk of exposure to infection. Vaccination generally begins at 8-10 weeks of age, with a second injection 3-4 weeks later. Annual boosters are recommended for cats at continued risk of exposure.

Bordetella bronchiseptica infection in cats. ABCD guidelines on prevention and management.

OVERVIEW: Bordetella bronchiseptica is a Gram-negative bacterium that colonises the respiratory tract of mammals and is considered to be a primary pathogen of domestic cats. It is sensible to consider B bronchiseptica as a rare cause of zoonotic infections. The bacterium is susceptible to common disinfectants. INFECTION: The bacterium is shed in oral and nasal secretions of infected cats. Dogs with respiratory disease are an infection risk for cats. The microorganism colonises the ciliated epithelium of the respiratory tract of the host, establishing chronic infections. DISEASE SIGNS: A wide range of respiratory signs has been associated with B bronchiseptica infection, from a mild illness with fever, coughing, sneezing, ocular discharge and lymphadenopathy to severe pneumonia with dyspnoea, cyanosis and death. DIAGNOSIS: Bacterial culture and PCR lack sensitivity. Samples for isolation can be obtained from the oropharynx (swabs) or via transtracheal wash/ bronchoalveolar lavage. DISEASE MANAGEMENT: Antibacterial therapy is indicated, even if the signs are mild. Where sensitivity data are unavailable, tetracyclines are recommended. Doxycycline is the antimicrobial of choice. Cats with severe B bronchiseptica infection require supportive therapy and intensive nursing care. VACCINATION RECOMMENDATIONS: In some European countries an intranasal modified-live virus vaccine is available. The modified-live product is licensed for use as a single vaccination with annual boosters. Cats should not be routinely vaccinated against B bronchiseptica (non-core), since the infection generally causes only a mild disease.

Feline infectious peritonitis. ABCD guidelines on prevention and management.

OVERVIEW: Feline coronavirus infection is ubiquitous in domestic cats, and is particularly common where conditions are crowded. While most FCoV-infected cats are healthy or display only a mild enteritis, some go on to develop feline infectious peritonitis, a disease that is especially common in young cats and multi-cat environments. Up to 12% of FCoV-infected cats may succumb to FIP, with stress predisposing to the development of disease. DISEASE SIGNS: The 'wet' or effusive form, characterised by polyserositis (abdominal and/or thoracic effusion) and vasculitis, and the 'dry' or non-effusive form (pyogranulomatous lesions in organs) reflect clinical extremes of a continuum. The clinical picture of FIP is highly variable, depending on the distribution of the vasculitis and pyogranulomatous lesions. Fever refractory to antibiotics, lethargy, anorexia and weight loss are common non-specific signs. Ascites is the most obvious manifestation of the effusive form. DIAGNOSIS: The aetiological diagnosis of FIP ante-mortem may be difficult, if not impossible. The background of the cat, its history, the clinical signs, laboratory changes, antibody titres and effusion analysis should all be used to help in decision-making about further diagnostic procedures. At the time of writing, there is no non-invasive confirmatory test available for cats without effusion. DISEASE MANAGEMENT: In most cases FIP is fatal. Supportive treatment is aimed at suppressing the inflammatory and detrimental immune response. However, there are no controlled studies to prove any beneficial effect of corticosteroids. VACCINATION RECOMMENDATIONS: At present, only one (intranasal) FIP vaccine is available, which is considered as being non-core. Kittens may profit from vaccination when they have not been exposed to FCoV (eg, in an early-weaning programme), particularly if they enter a FCoV-endemic environment.

H5N1 avian influenza in cats. ABCD guidelines on prevention and management.

OVERVIEW: Avian influenza is a disease of birds, caused by a type A influenza virus. The subtype H5N1 avian influenza occurs primarily in birds and infection varies from mild disease with little or no mortality to a highly fatal, rapidly spreading epidemic (highly pathogenic avian influenza). It is extremely rare for cats to be infected and there are only very few confirmed reports of the disease in cats in Europe. INFECTION: Cats can be infected via the respiratory and oral routes (eg, by eating infected birds). The key precondition for infection is that the cat lives in an area where H5N1 virus infection has been confirmed in birds. Additionally, the cat should have had outdoor access to an environment where waterfowl is present, or contact with poultry or uncooked poultry meat, or close contact with an H5N1-infected, sick cat during the first week of infection. CLINICAL SUSPICION: Clinical signs in cats may include fever, lethargy, dyspnoea, conjunctivitis and rapid death. Neurological signs (circling, ataxia) have also been recorded. DIAGNOSIS: The veterinary authorities should be notified. Oropharyngeal, nasal and/or rectal swabs or faecal samples of suspected cases should be submitted for PCR and/or virus isolation. Post-mortem samples of lung and mediastinal lymph nodes should be obtained. Particular care should be taken when handling the cat and/or samples. DISEASE MANAGEMENT: The virus is sensitive to all standard medical disinfectants. Cats with suspected H5N1 infection should be kept in strict isolation. Owners should be advised to confine the cat to a separate room prior to bringing it to the veterinary clinic. VACCINATION AND DISEASE PREVENTION: No H5N1 vaccines are commercially available for cats. In the event of confirmed cases of H5N1 avian influenza in birds in the area, owners should keep their cats indoors until further information is available, and follow official regulations.

Exploring early life events including diet in cats presenting for gastrointestinal signs in later life.

Our study aimed to determine if certain early life events were more prevalent in cats presenting to veterinary practices specifically for gastrointestinal signs on at least two occasions between six months and 30 months of age. Data from an owner-completed questionnaire for 1212 cats before 16 weeks of age and subsequent questionnaires for the same cats between six months and 30 months of age were reviewed. Of the 1212 cats included, 30 visited a veterinary practice for gastrointestinal signs on two or more occasions. Of the early life events recorded, cats reported with vomiting, diarrhoea or both, and/or those not exclusively fed commercial diet(s) that meets the World Small Animal Veterinary Association (WSAVA) Global Nutrition Committee (GNC) guidelines before 16 weeks of age were more likely to visit veterinary practices specifically for gastrointestinal signs on at least two occasions between six months and 30 months of age (P<0.001, odds ratio (OR)=2.64, 95 per cent confidence interval (CI)=1.66-4.22 and P=0.030, OR=1.51, 95 per cent CI=1.04-2.22, respectively). Ensuring cats exclusively consume commercial diet(s) that meets the WSAVA GNC guidelines and further studies identifying specific aetiologies for vomiting and diarrhoea before 16 weeks of age to enable prevention may reduce the number of cats subsequently presenting to primary care veterinary practices for repeated gastrointestinal signs.

Adaptation of IFN-gamma ELISA and ELISPOT tests for feline tuberculosis.

There are currently no reliable immunodiagnostic tests for feline tuberculosis. Infection of domestic cats in the UK is thought to occur via their contact with the relevant reservoir of infection, e.g. cattle and badgers for Mycobacterium bovis, and rodents for M. microti. In the African National Parks, where M. bovis infection of Bovidae is an increasing problem, transmission to big cats is occurring via their ingestion of infected carcasses. We have adapted feline ELISA and ELISPOT assays to potentially provide the first cell-based diagnostic test for the detection of tuberculosis in cats. We tested peripheral blood mononuclear cell antigen-specific IFN-gamma responses of 18 cats suspected of mycobacterial infection for which biopsy material was co-submitted to the Veterinary Laboratories Agency for mycobacterial culture and identification. Seventeen cats were tested by ELISA while seven cats were tested by ELISPOT (six cats were tested by both ELISA and ELISPOT). Six healthy control cats provided baseline data for these tests. Responses to bovine and avian tuberculins (PPDB and PPDA) and a protein cocktail of ESAT6 and CFP10 were measured, together with positive mitogen (PMA and calcium ionophore) and negative (medium) controls. Overall, both ELISPOT and ELISA tests were found to be suitable for generating rapid results (2 and 4 days, respectively), which provided good predictive information for M. bovis and M. microti infections, but were unable to reliably discern M. avium infection.

Assessing the impact of a regional UK feline neutering campaign.

Neutering is key to feline population control. Neutering campaigns provide education and/or financial assistance to encourage neutering. This study assessed the impact of the Cats Protection East Midlands Neutering Campaign (CPEMNC) on the proportion and ages of cats neutered. The CPEMNC, comprising of an outreach programme and voucher-based subsidised neutering scheme, began in June 2014. A convenience sample of owners who had attended 12 regional veterinary practices to complete a cat vaccination course in June/July 2014, or to have their cat neutered in October 2014 (CAMPAIGN) were compared with an equivalent control period in 2013 (CONTROL). Data collected by postal questionnaire revealed that the proportion of cats neutered by six months of age was significantly higher and the age at neutering significantly lower in the CAMPAIGN (n=134) versus the CONTROL groups (n=100). Results of multivariable logistic regression indicated cats were significantly more likely to be neutered by six months of age if they were in the CAMPAIGN group (OR 2.44) and male (OR 2.17), compared with in the CONTROL group and female. Further work is needed to evaluate factors important for campaign success and to explore the effectiveness of campaigns within the wider community and across the UK.

Molecular characterisation of 12 Chlamydophila felis polymorphic membrane protein genes.

A group of genes thought to encode members of the unique chlamydial polymorphic membrane protein (pmp) family were recently described in the Chlamydophila felis genome. This study aimed to commence characterisation of a subset of 12 of these putative pmp genes by developing and using gene-specific real-time (Q)PCR assays to confirm their presence in a wide range of C. felis field isolates and laboratory strains, and to look for pmp mRNA expression during in vitro infection. Sequencing of 525-698 base pair regions of pmp genes 7, 9-11, 13-20 for two laboratory strains of C. felis and alignment with the published Fe/C-56 sequence found only a single nucleotide polymorphism present in pmp9. Following the development of gene-specific (Q)PCR assays, analysis of genomic DNA extracted from 40 C. felis field isolates and 4 laboratory strains found that all 12 pmp genes were represented in all cases. Reverse transcription (RT)-QPCR analysis of RNA extracted from cell cultures at 24 and 48 h post inoculation with 1 of 5 different strains of C. felis detected transcripts for all 12 pmp genes at both time points. Analysis of the relative levels of pmp gene transcription suggested that down-regulation of the expression of multiple C. felis pmp genes occurs between 24 and 48 h post inoculation. This study provides the first evidence that 12 of the putative pmp C. felis genes are transcribed during in vitro infection, and shows that these genes are present in a large range of C. felis field isolates and multiple passage laboratory-grown strains.

Altered tryptophan metabolism in FIV-positive cats.

BACKGROUND: Feline immunodeficiency virus (FIV) is analogous to human immunodeficiency virus, the causative agent of human acquired immunodeficiency syndrome (AIDS). In AIDS patients, a progressive reduction in serum tryptophan concentration occurs because of activation of an inducible tryptophan degradation pathway mediated by elevated lamda-interferon production. HYPOTHESIS: Cats infected with FIV have increased tryptophan catabolism evidenced by reduced circulating concentrations of tryptophan and increased concentrations of the tryptophan catabolite kynurenine. ANIMALS: Convenience sample of 235 cats submitted for diagnostic FIV serology (115 FIV-negative and 120 FIV-positive cats). METHODS: Retrospective, cross-sectional study. Serum was assayed for tryptophan and kynurenine using a high performance liquid chromatography assay with fluorescence and ultraviolet detection, respectively. RESULTS: Tryptophan and kynurenine concentrations were log-normally distributed. Geometric mean concentrations were: tryptophan: FIV-positive 30.6 microM (95% CI: 26.8 34.8 microM), FIV-negative 48.9 [microM (95% CI: 43.6-54.9 microM) (P < .001); kynurenine: FIV-positive 22.7 microM (95% CI: 25.5-10.9 microM), FIV-negative 9.9 microM (95% CI: 20.3-9.03 microM) (P < .001). The ratio of kynurenine to tryptophan was: FIV-positive 4.93 (95% CI: 5.62-4.32), FIV-negative 1.34 (95% CI: 1.53 1.17) (P < .0001). CONCLUSIONS AND CLINICAL IMPORTANCE: Serum tryptophan concentration was significantly lower and serum kynurenine concentration was significantly higher in FIV-positive cats. The kynurenine: tryptophan ratio was >3-fold higher in FIV-positive animals, indicating increased tryptophan catabolism in this group. Dietary or pharmacologic intervention to support serum tryptophan concentrations has been shown to be clinically useful in humans with AIDS and might be applicable to cats with FIV infection.

Diagnosis of feline leukaemia virus infection by semi-quantitative real-time polymerase chain reaction.

In this paper the design and use of a semi-quantitative real-time polymerase chain reaction assay (RT-PCR) for feline leukaemia virus (FeLV) provirus is described. Its performance is evaluated against established methods of FeLV diagnosis, including virus isolation and enzyme-linked immunoassay (ELISA) in a population of naturally infected cats. The RT-PCR assay is found to have both a high sensitivity (0.92) and specificity (0.99) when examined by expectation maximisation methods and is also able to detect a large number of cats with low FeLV proviral loads that were negative by other conventional test methods.

An update on FIV and FeLV test performance using a Bayesian statistical approach.

BACKGROUND: Screening tests for feline retroviruses are thought to have high sensitivity and specificity, although previous studies that evaluated these tests have limitations. Novel statistical approaches have been developed that allow the estimation of sensitivity and specificity in situations where the true state of the disease in individual animals cannot be assured. OBJECTIVE: The purpose of this study was to evaluate the sensitivity and specificity of a variety of retrovirus tests, including some screening tests, in a population of cats potentially infected with either feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV) by using a Bayesian statistical approach. METHODS: Four hundred and ninety blood samples from cats being evaluated for FIV infection were tested by 2 rapid immunomigration tests (Witness single [WS], Witness combi [WC]) and a plate-based ELISA (Petcheck) for FIV antibody, and by a newly designed real-time polymerase chain reaction (PCR) assay for FIV provirus. Four hundred and ninety-five blood samples from cats being evaluated for FeLV infection were tested by 2 rapid immunomigration tests (WS, WC) and a plate-based ELISA (Petcheck) for FeLV antigen, and by a FeLV virus isolation technique. Results were then analyzed by using a Bayesian statistical method. RESULTS: For FIV tests, median sensitivity estimates were 0.98 for WS, 0.97 for WC, 0.98 for ELISA, and 0.92 for PCR. Median specificity estimates were 0.96 for WS, 0.96 for WC, 0.93 for ELISA, and 0.99 for PCR. For FeLV tests, median sensitivity estimates were 0.97 for WS, 0.97 for WC, 0.98 for ELISA, and 0.91 for virus isolation. Median specificity estimates were 0.96 for WS, 0.96 for WC, 0.98 for ELISA, and 0.99 for virus isolation. CONCLUSIONS: The use of Bayesian statistical methods overcomes a variety of methodologic problems associated with diagnostic test evaluations, including the lack of a definitive reference test. The sensitivity and the specificity of all 6 evaluated screening tests was high: however, specificity estimates were slightly lower than those reported by most recent studies.