Quality of different in-clinic test systems for feline immunodeficiency virus and feline leukaemia virus infection

Immunocytochemistry of bone marrow aspirates: a tool in the diagnosis of feline leukemia virus infection in cats

Feline leukemia virus (FeLV) is a highly debilitating cat pathogen due to its ability to cause many pathological changes. Therefore, identifying the virus directly in bone marrow can be a highly relevant diagnostic tool even in the absence of viraemia. The aim of this study was to compare the diagnostic efficiency of immunocytochemistry (ICC) of bone marrow aspirates with enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR). Blood samples were collected from 188 cats and separated into aliquots of whole blood for nested PCR using the U3 LTR region and the gag gene of FeLV-A as reference and serum for detection of the p27 antigen by ELISA. Bone marrow samples from these cats were placed on silanized slides for anti-FeLV ICC using gp70 as primary antibody. A total of 28.2% of the cats tested for FeLV were positive in at least one of the tests, with 26.6% positive by PCR, 18.1% by ICC and 11.2% by ELISA. Cohen's kappa agreement test revealed moderate agreement between ELISA and PCR results and substantial agreement between ICC and ELISA and between ICC and PCR. The results indicated that ICC of bone marrow is an efficient novel diagnostic test for FeLV infection.

Evaluation of leukocyte ratios as survival prognostic markers in feline retrovirus infections

The utility of neutrophil-lymphocyte ratio (NLR), monocyte-lymphocyte ratio (MLR), and platelet-lymphocyte ratio (PLR) as prognostic markers in Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) infections has not yet been investigated. The aim of this study was to investigate these leukocyte ratios in retrovirus-positive cats and to evaluate their prognostic value for survival. This retrospective case-control study included 142 cats, 75 FIV-Antibodies (Ab)-positive, 52 FeLV-Antigen (Ag)-positive, and 15 FIV-Ab+FeLV-Ag-positive, and a control population of 142 retrovirus-negative age-, sex-, and lifestyle-matched cats. Signalment, complete blood count at the time of serological testing, and outcome were recorded. Leukocyte ratios were compared within the same case-control population, among the three retrovirus-seropositive populations, and were related to survival time. No significant difference was found in NLR, MLR, or PLR between FIV-Ab-positive and FIV-Ab+FeLV-Ag-positive cats and their cross-matched controls. In the FeLV-Ag-positive population, MLR was significantly lower than in the control population (0.05 and 0.14, respectively, P=0.0008). No ratio discriminated among the three infectious states. No ratio was significantly different between survivors and non-survivors in the population of FIV-Ab-positive cats. MLR at diagnosis was significantly higher in FeLV-Ag-positive cats that died 1-3 years after diagnosis than in FeLV-Ag-positive cats still alive at 3 years (P=0.0284). None of the three ratios could predict retroviruses-positive cats that would survive to the end of the study. Overall the results indicate that NLR, MLR, and PLR are not significantly different among retrovirus statuses evaluated and had a very limited prognostic value for the survival time in retrovirus-positive cats.

Molecular Detection and Genetic Characterization of Feline Immunodeficiency Virus (FIV) in Seropositive Cats in Northern Italy

Feline immunodeficiency virus (FIV) is responsible for immunodeficiency syndrome in cats. Several viral subtypes have been identified, each with a variable geographical distribution. To date, the subtype B is known to be the genotype spread in Italy. In this study, the genetic diversity of FIV in northern Italy was assessed by detecting proviral DNA in the blood samples of 50 cats determined to be positive through an anti-FIV antibodies test. These cats were tested using six different PCR assays, and the identified viruses were sequenced and analyzed. Forty-eight cats were confirmed positive, and several FIV subtypes were characterized. As expected, the subtype B was the most commonly observed, and the subtype A was reported for the first time in Italy. Moreover, a new taxon possibly representing an additional FIV subtype was detected, and one virus belonging to subtype B potentially had a recombinant origin. The genetic variability between the FIV viruses that emerged in this study may lead to the potential diagnostic failure of single molecular tests. Therefore, a new diagnostic strategy, which adopts different molecular tests and sequencing, is recommended to monitor the evolution and spread of FIV.

Epidemiology of Pathogenic Retroviruses and Domestic Cat Hepadnavirus in Community and Client-Owned Cats in Hong Kong

Understanding the local epidemiology of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) in Hong Kong will inform retrovirus prevention strategies. Domestic cat hepadnavirus (DCH), a novel hepatitis-B-like virus, is commonly detected among client-owned cats in Hong Kong, but community cats have not been studied. The aims of this study were to investigate the frequency and potential risk factors for (i) FeLV and FIV among community and client-owned cats and (ii) perform molecular detection of DCH among community cats in Hong Kong. Blood samples from 713 cats were obtained from client-owned (n = 415, residual diagnostic) and community cats (n = 298, at trap-neuter-return). Point-of-care (POC) testing for FeLV antigen and feline immunodeficiency virus (FIV) anti-p15 and p24 antibodies was performed. FeLV-positive samples were progressed to p27 sandwich enzyme-linked immunosorbent assay. Whole blood DNA was tested with qPCRs for FeLV U3 and gag, and nested PCRs where additional information was required. DCH qPCR was performed on a subset of community cats (n = 193). A single, regressive, FeLV infection was detected in a client-owned cat (1/415 FeLV U3 qPCR positive, 0.2%, 95% CI 0.0-1.3%). Five/415 client-owned cats tested presumably false FeLV-antigen positive (qPCR negative). No markers of FeLV infection were detected in community cats (0/298; 0%). FIV seroprevalence was much higher in community cats (46/298, 15.4%) than in client-owned cats (13/415, 3.1%) (p < 0.001). Mixed breed was a risk factor for FIV infection in client-owned cats. Neither sex nor age were associated with FIV infection. DCH DNA was detected in 34/193 (17.6%) community cats (median viral load 6.32 × 103 copies/reaction). FeLV infection is rare in Hong Kong, negatively impacting the positive predictive value of diagnostic tests. FeLV-antigen testing remains the screening test of choice, but confirmation of a positive result using FeLV qPCR is essential. FIV infection is common in community cats and the absence of a sex predisposition, seen previously in cats managed similarly, raises questions about virus-transmission dynamics in these groups. DCH infection is very common in Hong Kong, both in client-owned and community cats, highlighting the importance of understanding the pathogenic potential of this virus for cats.

Prevalence of feline leukemia virus and feline immunodeficiency virus in cats from southern Italy: a 10-year cross-sectional study

Introduction

Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are well-known retroviruses causing important infections in domestic cats worldwide. The goal of this study was to determine the prevalence of FeLV and FIV infections in cat living indoor and outdoor in southern Italy.

Methods

The survey was conducted on 1322 stray and owned cats from the regions of Campania, Basilicata, and Calabria. It was carried out over a 10-year period to obtain a more realistic picture of the prevalence of these retroviral diseases in the country. FIV and FeLV status was determined by enzyme-linked immunosorbent assay (ELISA) using a commercial kit (SNAP Combo Plus FeLV/FIV, IDEXX). Risk factors were analysed by logistic regression.

Results and Discussion

The results showed that 101/1322 (7.64%) cats were positive for FeLV antigen and 110/1322 (8.32%) cats were positive for FIV antibody. Twenty-six of the 1322 cats (1.97%) were positive for both FIV and FeLV infection. Our results are similar to those published in recent studies in Europe. A statistically significant association (p < 0.05) was found between year, province, region, lifestyle and risk of FeLV infection. FIV positivity was instead statistically associated only with year and lifestyle.

Serological Survey of Retrovirus and Coronavirus Infections, including SARS-CoV-2, in Rural Stray Cats in The Netherlands, 2020-2022

Stray cats can host (zoonotic) viral pathogens and act as a source of infection for domestic cats or humans. In this cross-sectional (sero)prevalence study, sera from 580 stray cats living in 56 different cat groups in rural areas in The Netherlands were collected from October 2020 to July 2022. These were used to investigate the prevalence of the cat-specific feline leukemia virus (FeLV, n = 580), the seroprevalence of the cat-specific feline viruses feline immunodeficiency virus (FIV, n = 580) and feline coronavirus (FCoV, n = 407), and the zoonotic virus severe acute respiratory coronavirus-2 (SARS-CoV-2, n = 407) using enzyme-linked immunosorbent assays (ELISAs). ELISA-positive results were confirmed using Western blot (FIV) or pseudovirus neutralization test (SARS-CoV-2). The FIV seroprevalence was 5.0% (95% CI (Confidence Interval) 3.4-7.1) and ranged from 0-19.0% among groups. FIV-specific antibodies were more often detected in male cats, cats ≥ 3 years and cats with reported health problems. No FeLV-positive cats were found (95% CI 0.0-0.6). The FCoV seroprevalence was 33.7% (95% CI 29.1-38.5) and ranged from 4.7-85.7% among groups. FCoV-specific antibodies were more often detected in cats ≥ 3 years, cats with reported health problems and cats living in industrial areas or countryside residences compared to cats living at holiday parks or campsites. SARS-CoV-2 antibodies against the subunit 1 (S1) and receptor binding domain (RBD) protein were detected in 2.7% (95% CI 1.4-4.8) of stray cats, but sera were negative in the pseudovirus neutralization test and therefore were considered SARS-CoV-2 suspected. Our findings suggest that rural stray cats in The Netherlands can be a source of FIV and FCoV, indicating a potential risk for transmission to other cats, while the risk for FeLV is low. However, suspected SARS-CoV-2 infections in these cats were uncommon. We found no evidence of SARS-CoV-2 cat-to-cat spread in the studied stray cat groups and consider the likelihood of spillover to humans as low.

Progressive and regressive infection with feline leukemia virus (FeLV) in cats in southern Brazil: Prevalence, risk factors associated, clinical and hematologic alterations

Enzyme-linked immunosorbent assay (ELISA) for viral antigen is commonly used for the diagnosis of progressive feline leukemia virus (FeLV) infection but is not able to determine the true prevalence of infection when used as the sole test. Additional testing to detect proviral DNA will identify regressive (antigen negative) FeLV infections as well as progressive infections. Therefore, this study aimed to determine the prevalence of progressive and regressive FeLV infection, outcome-associated factors, and hematologic changes. A cross-sectional study was performed on 384 cats selected from routine hospital care. Blood samples were subjected to complete blood count, ELISA for FeLV antigen and FIV antibody, and nested PCR amplifying the U3- LTR region and gag gene, which are conserved in most exogenous FeLV. The prevalence of FeLV infection was 45.6% (CI_95% 40.6-50.6%). The prevalence of progressive infection (FeLV⁺P) was 34.4% (CI_95% 29.6-39.1%), that of regressive infection (FeLV+R) was 10.4% (CI_95% 7.4-13.4%), for discordant but positive results 0.8% (CI_95% 0.75-0.84%), for FeLV⁺P coinfected with FIV 2.6% (CI_95% 1.2-4.0%), and FeLV⁺R coinfected with FIV 1.5% (CI_95% 0.3-2.7%). Male cats were three times more likely to be in the FeLV⁺P group. Cats coinfected with FIV were 4.8 times more likely to belong to the FeLV⁺R group. In the FeLV⁺P group, the main clinical changes were lymphoma (38.5%), anemia (24.4%), leukemia (17.9%), concomitant infections (15.4%), and feline chronic gingivostomatitis - FCGS (3.8%). In the FeLV⁺R group, the main clinical signs were anemia (45.4%), leukemia (18.2%), concomitant infections (18.2%), lymphoma (9.1%), and FCGS (9.1%). Cats in the FeLV⁺P and FeLV⁺R groups showed mainly thrombocytopenia (56.6% and 38.2%), non-regenerative anemia (32.8% and 23.5%), and lymphopenia (33.6% and 20.6%). Hemoglobin concentration, packed cell volume (PCV), platelet count, lymphocytes, and eosinophils in the FeLV⁺P and FeLV⁺R groups had lower medians than the control group (FeLV/FIV-uninfected, healthy). Erythrocyte and eosinophil counts were statistically different among the three groups, with the medians of the FeLV⁺P and FeLV⁺R groups being lower than those of the control group. In addition, the median PCV and band neutrophil counts were higher in FeLV⁺P than in FeLV⁺R. Our results show a high prevalence of FeLV, different factors associated with the course of infection, and more frequent and severe hematologic changes in progressive infections compared with regressive infections.

Disease threats to tigers and their prey

The contraction of the global tiger population over the last 100 years into small, often isolated subpopulations has made them increasingly vulnerable to the impact of disease. Despite this, the health of wild tigers continues to be insufficiently funded and explored. For example, canine distemper virus (CDV), has been associated with localized declines and increased risk of extinction, and yet has received little research attention in most tiger range countries. The emergence of new pathogenic threats has posed fresh challenges, including African swine fever virus (ASFV), which has the potential to devastate wild boar populations, and severe acute respiratory syndrome coronavirus (SARS-CoV2) with implications for tiger conservation that remain unknown. The objective of this review is to synthesize current research on the health of tigers and their prey that impacts the conservation of tigers in the wild. Published sources are interpreted based on three mechanisms through which disease can affect the viability of tiger populations: (1) by reducing the survival of adult tigers, (2) by reducing breeding productivity, and (3) by reducing the carrying capacity of tiger habitat through decreased prey abundance. Examples of CDV, SARS-CoV2, carnivore protoparvovirus 1 and ASFV are used to illustrate these processes and inform discussion of research and mitigation priorities.

Field Performance of a Rapid Test to Detect Progressive, Regressive, and Abortive Feline Leukemia Virus Infections in Domestic Cats in Australia and Germany

Different feline leukemia virus (FeLV) infection outcomes are possible in cats following natural exposure, such as progressive infections (persistent viremia), regressive infections (transient or no viremia followed by proviral persistence) and abortive infections (presence of only antibodies). Laboratory-based testing is currently required for categorization of infection outcomes in cats. The aim of this study was to evaluate the field performance of a novel, rapid, combination point-of-care (PoC) test kit commercially available in Europe (v-RetroFel^®Ag/Ab; 2020-2021 version) to determine different FeLV infection outcomes by concurrent detection of FeLV antigen (p27) and antibodies against FeLV transmembrane envelope protein (p15E). A secondary aim was to evaluate the performance of the same test kit (v-RetroFel^®FIV) to determine positive/negative feline immunodeficiency virus (FIV) infection status by the detection of antibodies to FIV capsid protein (p24) and transmembrane glycoprotein (gp40). Two cohorts of domestic cats were recruited and tested with v-RetroFel^® using plasma or serum, including cats in Australia (n = 200) and cats in Germany (n = 170). Results from p27 antigen PoC testing, proviral DNA PCR, and neutralizing antibody testing or testing for antibodies against non-glycosylated surface unit envelope protein (p45) were used to assign cats to groups according to different FeLV infection outcomes. Testing with a laboratory-based FeLV p15E antibody ELISA was also performed for comparison. In the first cohort, v-RetroFel^®Ag/Ab correctly identified 89% (109/122) FeLV-unexposed cats and 91% (21/23) progressive infections, but no regressive (0/23) or abortive (0/32) infections. In the second cohort, v-RetroFel^®Ag/Ab correctly identified 94% (148/158) FeLV-unexposed cats and 100% (4/4) progressive infections, but no regressive (0/2) and only 17% (1/6) abortive infections. There was test agreement between v-RetroFel^®Ab and the p15E laboratory ELISA in 58.9% of samples. As a secondary outcome of this study, the sensitivity and specificity of v-RetroFel^®FIV testing in cohort 1 were 94.7% (18/19) and 98.3% (178/181), and in cohort 2, 30.0% (3/10) and 100.0% (160/160), respectively. Prior history of FIV vaccination did not produce any false-positive FIV results. In conclusion, v-RetroFel^®Ag/Ab (2020-2021 version) was unable to accurately determine different FeLV infection outcomes in the field. Improvements of the test prior to application to field samples are required.

Occurrence and risk factors of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) in cats of Lebanon

A cross-sectional study was carried out between April 2020 and August 2021. Blood samples were collected from 260 household cats recruited in different clinics in North and Mount Lebanon, with the aim of determining the seroprevalence of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV). The seroprevalence reported reached 18.84% (95% CI 0.14-0.24) and 13.84% (95% CI 0.09-0.18) for FIV and FeLV, respectively. FIV seropositivity was associated with a younger age, health and neuter status, lymphoma, lethargy, and vomiting. Furthermore, male sex, neuter status, lymphoma, anaemia, lethargy, and vomiting were significantly associated with FeLV seropositivity. This first data from Lebanon emphasizes the need for implementing preventive programmes to cope with FIV- and FeLV-associated morbidity and mortality among cats.

Evaluation of a Point-of-Care Feline Immunodeficiency Virus (FIV) Test Kit (RapidSTATUS™ FIV) to Determine the FIV Status of FIV-Vaccinated and FIV-Unvaccinated Pet Cats in Australia

Simple Summary

This study evaluated a commercial point-of-care (PoC) feline immunodeficiency virus (FIV) test kit (RapidSTATUS™ FIV) for its accuracy in determining the FIV status of FIV-vaccinated and FIV-unvaccinated pet cats in Australia. In countries where FIV vaccination is used, veterinarians need a PoC kit that will produce a negative result for a FIV-uninfected cat, even if the cat is FIV-vaccinated or the FIV vaccination history is unknown, since incorrect diagnoses can impact negatively on the welfare of cats. FIV PoC kits also need to produce positive results in FIV-infected cats to help with appropriate management and to enable strategies to be implemented to prevent other cats from becoming FIV-infected. Results presented here show RapidSTATUS™ FIV to be highly accurate (98.8−100%) in a range of FIV-vaccinated and FIV-unvaccinated scenarios. Therefore, Australian veterinarians can reliably use RapidSTATUS™ FIV to rapidly and accurately determine the FIV status of all cats.

Abstract

Feline immunodeficiency virus (FIV) is a retrovirus that can cause immunosuppression, co-morbidities, and neoplasia in infected cats, and is commonly tested for in veterinary clinics and animal shelters in Australia. FIV diagnosis using point-of-care (PoC) kits to detect FIV antibodies in Australia is complicated by the commercial availability of an inactivated whole-FIV vaccine. The aim of this study was to determine the accuracy of the RapidSTATUS™ FIV antibody test kit in FIV-vaccinated and FIV-unvaccinated cats in Australia. Plasma from pet cats of known FIV vaccination and FIV infection statuses (n = 361), comprised of 57 FIV-uninfected cats annually vaccinated against FIV, 10 FIV-uninfected cats with lapsed FIV vaccination histories, 259 FIV-unvaccinated/FIV-uninfected cats, and 35 FIV-infected cats, was tested. RapidSTATUS™ FIV testing had sensitivity of 97.1% (34/35) and specificity of 100% (326/326), with an overall accuracy of 99.7% (360/361). Additional testing was undertaken using plasma from FIV-uninfected cats recently administered a primary FIV vaccination course (n = 12) or an annual booster FIV vaccination (n = 10). RapidSTATUS™ FIV was 98.8% (81/82) accurate and 100% (32/32) accurate in cats recently administered primary or annual FIV vaccinations, respectively. The high level of accuracy of RapidSTATUS™ FIV (98.8–100%) therefore establishes this PoC kit as a DIVA (differentiating infected from vaccinated animals) test. RapidSTATUS™ FIV is recommended to aid animal shelters, veterinarians, and researchers in Australia to accurately determine FIV infection status, irrespective of FIV vaccination history.

Hemogram Findings in Cats from an Area Endemic for Leishmania infantum and Feline Immunodeficiency Virus Infections

Simple Summary

Some cats positive for Leishmania infantum (Li) show clinical signs and clinicopathological changes, including hemogram abnormalities. However, co-infections or co-morbidities are often detected in cats with leishmaniosis, and they can have a role in the clinical abnormalities observed. In feline Leishmania infantum infections and in clinical cases of feline leishmaniosis, a significant association with feline immunodeficiency virus (FIV) has been detected, but the role of this co-infection is controversial. The aims of this study were to retrospectively evaluate hemogram changes in cats from areas endemic for Leishmania infantum and feline immunodeficiency virus infections (Sicily and Calabria regions, Southern Italy) and to analyze the role of both pathogens in the abnormalities detected. A retrospective cross-sectional study was carried out on 496 cats. Hematological changes in cats positive for Leishmania infantum were found, particularly abnormalities compatible with chronic inflammation including moderate anemia, monocytosis, and morphologically activated monocytes. Moreover, some abnormalities, such as thrombocytosis, seem to arise when cats are co-infected with FIV. Feline leishmaniosis should be considered when some hemogram abnormalities compatible with chronic inflammation are detected.

Abstract

In feline Leishmania infantum (Li) infection and in clinical cases of feline leishmaniosis, co-infection with feline immunodeficiency virus (FIV) has been reported. However, the role of the retroviral co-infection in the impairment of feline clinical health is still controversial. The aim of this study was to evaluate hemogram changes in cats from regions endemic for both Li and FIV infection. Four hundred and ninety-six cats tested for Li (EDTA blood polymerase chain reaction and immunofluorescence antibody test) and for FIV infection (enzyme-linked immune assay) were retrospectively evaluated. Hemogram results including blood smear morphological evaluation were statistically compared considering four infection patterns: Li+FIV+, Li+FIV−, Li−FIV+, and Li−FIV−. Significantly lower values of erythrocytes (Li+FIV−: p = 0.0248; Li−FIV+: p = 0.0392) and hemoglobin (Li+FIV: p = 0.0086; Li−FIV+: p = 0.0249) were found in both infections when compared to Li−FIV− cats, and severity of anemia was more frequently moderate in Li-positive cats (p = 0.0206) and severe in FIV infection (p = 0.024). Li infection was associated with monocytosis (p = 0.0013) and morphologically activated monocytes (p = 0.0209). Moreover, FIV infection was associated with the presence of inflammatory leukogram (p = 0.023), and an association between thrombocytosis and the co-infection was found (p = 0.0347). Li infection in cats induces hematological changes compatible with chronic inflammation, some of which are due to co-infection with FIV.

[Feline leukemia virus infection - a guide to diagnosis]

Feline leukemia virus (FeLV) infection affects cats worldwide. The course of FeLV infection can change and vary over time. The complex pathogenesis, the availability of many different testing methods, and the interpretation of test results are often challenging for veterinarians. Cats with progressive infection (persistently p27 antigen-positive) shed FeLV mainly through saliva and are therefore considered a source of infection for uninfected cats. Diagnosing regressive infection is often challenging, since it usually cannot be detected by commonly used point of care-tests (p27 antigen test) and thus, it often remains undetected. Nevertheless, cats with regressive infection are FeLV carriers (provirus-positive) and when the immune system is suppressed, reactivation of the infection and FeLV-associated clinical signs can occur. Abortively infected cats are never viraemic, do not shed virus, and do not develop clinical signs. Abortive infection can solely be diagnosed via antibodies detection in blood. A new point-of-care test for the identification of antibodies against FeLV p15E antigen has recently been introduced on the European market and is currently being evaluated.

Association between feline immunodeficiency virus and Leishmania infantum infections in cats: a retrospective matched case-control study

BACKGROUND

Feline leishmaniosis caused by Leishmania infantum is often associated with feline immunodeficiency virus (FIV) infection; however, the role and clinical significance of this coinfection remain unknown. This study aimed to assess whether FIV is associated with L. infantum infection in cats from canine leishmaniosis endemic areas and to report the clinical signs and hematological alterations associated with coinfection.

METHODS

A retrospective matched case-control study (ratio 1:2) was conducted. Data of clinical examination and complete blood count (CBC) were selected from a cohort of 705 cats examined for epidemiological studies on feline leishmaniosis conducted between 2012 and 2019. Ninety-one FIV seropositive cases and 182 FIV seronegative control cats were selected. Matching was done according to age, sex, lifestyle and geographic provenience of case cats. Rapid ELISA devices were mainly used to detect anti-FIV antibodies. Anti-Leishmania IgG antibodies were detected by indirect-immunofluorescence test (IFAT). Leishmania DNA was searched in blood, oral and conjunctival swabs by quantitative real-time PCR.

RESULTS

Feline immunodeficiency virus seropositive cats had no hematological abnormalities suggestive of an advanced stage of FIV infection and were statistically more frequently IFAT positive, and their risk of being L. infantum antibody positive was 2.8 greater than in the FIV seronegatives. The association of FIV seropositivity with L. infantum antibody positivity was confirmed in the univariable model of logistic regression. A multivariate model found FIV infection and L. infantum PCR positivity as predictors of a positive L. infantum IFAT result. Male outdoor cats from rural or suburban areas were at risk for FIV and L. infantum antibody positivity. Clinical signs more frequently associated with the coinfection were oral lesions, pale mucous membranes and low body condition score (BCS).

CONCLUSIONS

This study documents that FIV seropositive cats with no hematological abnormalities suggestive of an advanced stage of FIV infection are more prone to be L. infantum seroreactive by IFAT in endemic areas. Therefore, FIV seropositive cats should be tested for L. infantum antibodies and treated for preventing sand fly bites. Pale mucous membranes, low BCS and oral lesions but no CBC abnormalities were significantly associated with the coinfection.

Serum Samples from Co-Infected and Domestic Cat Field Isolates Nonspecifically Bind FIV and Other Antigens in Enzyme-Linked Immunosorbent Assays

We evaluated enzyme-linked immunosorbent assay (ELISA) specificity for measuring seroantibody responses to two types of retroviral infections in domestic cats: feline immunodeficiency virus (FIV) and feline foamy virus (FFV). We compared the seroreactivity of specific pathogen-free (SPF) cat sera, sera from SPF cats inoculated with either FIV or FFV, and field isolates (e.g., shelter or privately owned cats). Sera from SPF cats experimentally infected with the cognate virus had significantly lower background in both FIV and FFV ELISAs compared to sera from negative field isolates. ELISA values for SPF cats exposed to either FIV or FFV tended to have higher OD values on the opposite ELISA antigen plate. FIV nonspecific background absorbance was greater than that of FFV, and 10 of 15 sera samples from FIV seronegative field samples were measured in the indeterminant range. These findings highlight that exposure to off-target pathogens elicit antibodies that may nonspecifically bind to antigens used in binding assays; therefore, validation using sera from SPF animals exposed during controlled infection results in the setting of a cutoff value that may be inappropriately low when applied to field samples. Our work also suggests that infection of domestic cats with pathogens other than FIV results in antibodies that cross-react with the FIV Gag antigen.

Antibody Responses in Cats Following Primary and Annual Vaccination against Feline Immunodeficiency Virus (FIV) with an Inactivated Whole-Virus Vaccine (Fel-O-Vax® FIV)

Although the antibody response induced by primary vaccination with Fel-O-Vax® FIV (three doses, 2-4 weeks apart) is well described, the antibody response induced by annual vaccination with Fel-O-Vax® FIV (single dose every 12 months after primary vaccination) and how it compares to the primary antibody response has not been studied. Residual blood samples from a primary FIV vaccination study (n = 11), and blood samples from cats given an annual FIV vaccination (n = 10), were utilized. Samples from all 21 cats were tested with a commercially available PCR assay (FIV RealPCRTM), an anti-p24 microsphere immunoassay (MIA), an anti-FIV transmembrane (TM; gp40) peptide ELISA, and a range of commercially available point-of-care (PoC) FIV antibody kits. PCR testing confirmed all 21 cats to be FIV-uninfected for the duration of this study. Results from MIA and ELISA testing showed that both vaccination regimes induced significant antibody responses against p24 and gp40, and both anti-p24 and anti-gp40 antibodies were variably present 12 months after FIV vaccination. The magnitude of the antibody response against both p24 and gp40 was significantly higher in the primary FIV vaccination group than in the annual FIV vaccination group. The differences in prime versus recall post-vaccinal antibody levels correlated with FIV PoC kit performance. Two FIV PoC kits that detect antibodies against gp40, namely Witness® and Anigen Rapid®, showed 100% specificity in cats recently administered an annual FIV vaccination, demonstrating that they can be used to accurately distinguish vaccination and infection in annually vaccinated cats. A third FIV PoC kit, SNAP® Combo, had 0% specificity in annually FIV-vaccinated cats, and should not be used in any cat with a possible history of FIV vaccination. This study outlines the antibody response to inactivated Fel-O-Vax® FIV whole-virus vaccine, and demonstrates how best to diagnose FIV infection in jurisdictions where FIV vaccination is practiced.

Molecular detection of feline leukemia virus in clinically ill cats in Klang Valley, Malaysia

Background and Aim

Feline leukemia virus (FeLV) is classified as Retroviridae gammaretrovirus. FeLV occurs worldwide, including Malaysia. Thus far, only one decade-old study on molecular characterization of Malaysian FeLV isolates exists, which resulted in a scarcity of updated information of current FeLV isolates circulating in Malaysia. This study was conducted to determine the status of FeLV in clinically ill cats and to study the molecular characterization and phylogenetic relatedness of the current isolates.

Materials and Methods

Convenience sampling was performed in 20 cats from the Gasing Veterinary Hospital in Selangor. Plasma and saliva samples were collected from 15 clinically ill cats and 5 healthy cats subjected to one-step reverse transcription-polymerase chain reaction with primers targeting a highly conserved gene of U3-LTR-gag.

Results

Two clinically ill cats' plasma and saliva samples tested positive for FeLV RNA. Partial nucleotide sequencing and phylogenetic analysis revealed that the current isolates were 94-99% homologous to the previous Malaysian and Japanese FeLV isolates.

Conclusion

Current FeLV isolates from this study displayed higher similarity with the previous Malaysian isolates, signifying that a similar FeLV strain circulated among the cat population in Selangor.

Feline leukaemia virus infection: A practical approach to diagnosis

PRACTICAL RELEVANCE

Feline leukaemia virus (FeLV) is a retrovirus of domestic cats worldwide. Cats lacking strong FeLV-specific immunity and undergoing progressive infection commonly develop fatal FeLV-associated disease. Many aspects of FeLV infection pathogenesis have been elucidated, some during more recent years using molecular techniques. It is recommended that the FeLV status of every cat is known, since FeLV infection can influence the prognosis and clinical management of every sick cat. Moreover, knowledge of a cat's FeLV status is of epidemiological importance to prevent further spread of the infection.

CLINICAL CHALLENGES

Diagnosing FeLV infection remains challenging due to different outcomes of infection, which can vary over time depending on the balance between the virus and the host's immune system. Furthermore, testing for FeLV infection has become more refined over the years and now includes diagnostic assays for different viral and immunological parameters. Knowledge of FeLV infection pathogenesis, as well as the particulars of FeLV detection methods, is an important prerequisite for correct interpretation of any test results and accurate determination of a cat's FeLV status.

AIMS

The current review presents recent knowledge on FeLV pathogenesis, key features to be determined in FeLV infection, and frequently used FeLV detection methods, and their characteristics and interpretation. An algorithm for the diagnosis of FeLV infection in a single cat, developed by the European Advisory Board on Cat Diseases, is included, and FeLV testing in specific situations is addressed. As well as increasing awareness of this deadly infection in domestic cats, the aim is to contribute diagnostic expertise to allow veterinarians in practice to improve their recognition, and further reduce the prevalence, of FeLV infection.

2020 AAFP Feline Retrovirus Testing and Management Guidelines

CLINICAL IMPORTANCE

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) infections are found in cats worldwide. Both infections are associated with a variety of clinical signs and can impact quality of life and longevity.

SCOPE

This document is an update of the 2008 American Association of Feline Practitioners' feline retrovirus management guidelines and represents current knowledge on pathogenesis, diagnosis, prevention and treatment of retrovirus infections in cats.

TESTING AND INTERPRETATION

Although vaccines are available for FeLV in many countries and for FIV in some countries, identification of infected cats remains an important factor for preventing new infections. The retrovirus status of every cat at risk of infection should be known. Cats should be tested as soon as possible after they are acquired, following exposure to an infected cat or a cat of unknown infection status, prior to vaccination against FeLV or FIV, and whenever clinical illness occurs. It might not be possible to determine a cat's infection status based on testing at a single point in time; repeat testing using different methods could be required. Although FeLV and FIV infections can be associated with clinical disease, some infected cats, especially those infected with FIV, can live for many years with good quality of life.

MANAGEMENT OF INFECTED CATS

There is a paucity of data evaluating treatments for infected cats, especially antiretroviral and immunomodulatory drugs. Management of infected cats is focused on effective preventive healthcare strategies, and prompt identification and treatment of illness, as well as limiting the spread of infection.

Decreased Sensitivity of the Serological Detection of Feline Immunodeficiency Virus Infection Potentially Due to Imported Genetic Variants

Feline immunodeficiency virus (FIV) is a lentivirus of domestic cats worldwide. Diagnosis usually relies on antibody screening by point-of-care tests (POCT), e.g., by enzyme-linked immunosorbent assays (ELISA), and confirmation using Western blot (WB). We increasingly observed ELISA-negative, WB-positive samples and aimed to substantiate these observations using 1194 serum/plasma samples collected from 1998 to 2019 primarily from FIV-suspect cats. While 441 samples tested positive and 375 tested negative by ELISA and WB, 81 samples had discordant results: 70 were false ELISA-negative (WB-positive) and 11 were false ELISA-positive (WB-negative); 297 ambiguous results were not analyzed further. The diagnostic sensitivity and specificity of the ELISA (82% and 91%, respectively) were lower than those reported in 1995 (98% and 97%, respectively). The diagnostic efficiency was reduced from 97% to 86%. False ELISA-negative samples originated mainly (54%) from Switzerland (1995: 0%). Sixty-four false ELISA-negative samples were available for POCT (SNAP^TM/WITNESS^R): five were POCT-positive. FIV RT-PCR was positive for two of these samples and was weakly positive for two ELISA- and POCT-negative samples. Low viral loads prohibited sequencing. Our results suggest that FIV diagnosis has become more challenging, probably due to increasing travel by cats and the introduction of new FIV isolates not recognized by screening assays.

First autochthonous case of clinical Hepatozoon felis infection in a domestic cat in Central Europe

Three different Hepatozoon (Apicomplexa, Hepatozoidae) species have been described infecting domestic cats in Europe (i.e. H. felis, H. canis and H. silvestris), however, reports on clinical hepatozoonosis are uncommon and treatment protocols are not clearly defined.

A six-year-old male European short-hair cat from Austria presented poor general condition, lethargy, anorexia, icterus, a painful abdomen, fever, ruffled hair and a tick infestation, and it had never left Austria. Laboratory tests revealed leukopenia, thrombocytopenia and increased serum levels of symmetric dimethylarginine (SDMA) and bilirubin. In May Grünwald-Giemsa-stained blood smears, structures resembling Hepatozoon gamonts were observed inside neutrophil granulocytes. A PCR targeting a fragment of the 18S rRNA gene of Hepatozoon spp. and DNA sequencing allowed the diagnosis of H. felis-DNA in blood samples. The cat was treated with imidocarb dipropionate (6 mg/kg body weight, repeated after 14 days) and doxycycline monohydrate (5 mg/kg body weight twice a day, p.o., for four weeks) and recovered completely. A broad haematological and biochemical laboratory control after six months showed all evaluated parameters under normal ranges. Coinfection with other feline pathogens (i.e. feline leukaemia virus, feline immunodeficiency virus, feline Coronavirus, Leishmania and Dirofilaria immitis) could not be detected.

This study reveals the presence of H. felis in Austria and provides more evidence on the geographical distribution and pathogenicity of this parasite for domestic cats. To the authors' knowledge, this is the first autochthonous case of feline hepatozoonosis in Central Europe.

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Clinical Hepatozoon felis infection in a domestic cat was diagnosed in Austria.

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The diagnosis was achieved by microscopy of blood smears, PCR and DNA-sequencing.

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Possible coinfections with other feline pathogens were ruled-out.

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The cat recovered completely after treatment with imidocarb and doxycycline.

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This represents the first autochthonous case of feline hepatozoonosis in Central Europe.

Prevalence of and factors associated with feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) in cats of the state of Santa Catarina, Brazil

A cross-sectional study was conducted in 274 cats for determination of FeLV antigenemia and FIV seropositivity and factors associated with those infections in cats presented at the Veterinary Hospital of the Santa Catarina State University - UDESC (Brazil). Apparent prevalence for sick cats at the hospital population was 28.41% (95%CI 21.88-34.94%) for FeLV, 7.65% (95%CI 3.71-11.50%) for FIV and 2.18% (95%CI 0.56-5.47%) for both viruses. For healthy cats, the apparent prevalence was 9.89% (95%CI 3.75-16.02%) for FeLV, 2.20% (95%CI 0.34-7.75%) for FIV by immunoassay (ELISA). Average age for FeLV- and FIV-positive individuals was 38.32 and 64.25 months, respectively. Behavior such as aggressiveness and sex (male) were both associated with increased odds of result positivity test for FeLV and FIV; older animals were also associated with FIV test results. A very small proportion of the animals were vaccinated against FeLV and none against FIV. Most of the animals were adopted from shelters or rescued from streets, living with multiple cats that had access to outdoors. The high prevalence of FeLV suggests a need for better control strategies against this disease.

Diagnostic performances of two rapid tests for detection of feline leukemia virus antigen in sera of experimentally feline leukemia virus-infected cats

Objectives

The objective of this study was to compare the diagnostic sensitivities and specificities of WITNESS FeLV-FIV (Zoetis) and SNAP FIV/FeLV Combo Test (IDEXX) for the detection of FeLV p27 antigen in the sera of experimentally feline leukemia virus (FeLV)-infected cats.

Methods

Diagnostic sensitivities of WITNESS and SNAP were determined through testing of 47 serum samples collected from cats day 56 post-experimental infection with a virulent FeLV Rickard strain. Successful experimental infection was confirmed based on observation of FeLV antigen and proviral DNA in anti-coagulated (EDTA) whole-blood samples by immunofluorescent antibody (IFA) test and PCR, respectively. Diagnostic specificities of both tests were determined through testing of sera of 92 laboratory-housed, non-FeLV-exposed specific pathogen-free (SPF) cats.

Results

Forty-one of 47 blood samples were IFA positive, whereas all 47 samples were PCR positive. All 92 non-FeLV-infected SPF cats were IFA and PCR negative. In comparison to IFA as the reference method, both WITNESS and SNAP tests yielded equivalent sensitivities and specificities of 100% and 97.8%, respectively. In comparison to PCR as the reference method, both WITNESS and SNAP tests likewise performed equivalently, with sensitivities and specificities of 91.5% and 100%, respectively.

Conclusions and relevance

Sensitivity and specificity of WITNESS FeLV-FIV for identifying FeLV p27 antigen in the sera of these experimentally FeLV-infected and non-FeLV-exposed SPF cats equaled those of the SNAP FIV/FeLV Combo Test. However, all positive results, regardless of the point-of-care test used, should be confirmed before making clinical decisions such as segregation from other cats or euthanasia.

Hematological findings and factors associated with feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) positivity in cats from southern Brazil

ABSTRACT: Using a retrospective study, 493 cats tested for FeLV and FIV were selected for analysis of the association between hematologic findings and positivity at immunoassay test. Individual and hematologic variables were assessed considering the influence of results using univariate and multivariate logistic regression analysis. Out 153 of the 493 cats were positive for FeLV (31%), 50 were positive for FIV (10.1%) and 22 were positive for both FIV and FeLV (4.4%). Multivariate analysis detected significant associations between FeLV infection and age below 1 year (p=0.01), age from 1 to 10 years (p=0.03), and crossbreed (p=0.04). Male cats were more likely to be FIV-positive (p=0.002). Regarding hematological changes, FeLV-positive cats have higher odds to anemia, leukopenia and lymphopenia than FeLV-negative cats. FIV-positive cats are more likely to have anemia than negative. Identification of associated factors related to animal status and correlation of hematological disorders with infection by retroviruses in cats could be useful for detecting these retroviral diseases in cats.

Epidemiology and clinical outcomes of feline immunodeficiency virus and feline leukaemia virus in client-owned cats in New Zealand

Objectives

The objectives were to collect baseline data on the occurrence, testing and vaccination practices, and clinical outcomes of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) in New Zealand

Methods

A cross-sectional survey of 423 veterinary practices in New Zealand was performed to collect data on FeLV and FIV testing and vaccination during the 2015 calendar year. Clinical records from 572 cats tested using a point-of-care ELISA at a first-opinion veterinary practice between 7 April 2010 and 23 June 2016 were also obtained and multivariable logistic regression models were constructed to identify risk factors for test positivity. Survival times were estimated using Kaplan–Meier methods.

Results

The survey was completed by 112 clinics (26.4%) of which 72 performed in-house testing. Of the 2125 tests performed, 56 (2.6%) were positive for FeLV and 393 (18.5%) were positive for FIV. Fewer than 1% of cats were vaccinated for FeLV, with veterinarians citing low perceived prevalence as the primary reason for not vaccinating. Being male compared with being female and having clinical evidence of immunosuppression were significant risk factors for both FeLV and FIV test positivity. The median survival times of FeLV and FIV test-positive cats were 10 days (95% confidence interval [CI] 0–16) and 650 days (95% CI 431–993), respectively.

Conclusions and relevance

Testing and vaccination for FeLV and FIV in New Zealand appears targeted towards high-risk animals, which may bias prevalence estimates. Baseline data should be monitored for changes in FeLV epidemiology now commercial vaccines are no longer available.

Prevalence of and risk factors for FIV and FeLV infection in two shelters in the United Kingdom (2011-2012)

The aims of this study were to determine the prevalence of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) infections in cats presented to two RSPCA (Royal Society for the Prevention of Cruelty to Animals) animal rehoming centres and to identify risk factors for infection. All cats presented at each centre between August 2011 and August 2012 were subjected to a patient-side test for FeLV/FIV on entry. Kittens under three months and cats euthanased within a short time of presentation were excluded from the study. Univariable and multivariable logistic regression were used to separately determine risk factors for FeLV and FIV infections. At shelter A, the prevalence of FIV infection was 11.4 per cent (54/474) and FeLV infection was 3 per cent (14/473), with two FIV/FeLV coinfections identified. At shelter B, the prevalence of FIV infection was 3 per cent (4/135) and FeLV infection was 0 per cent (0/135). Cats at shelter A were significantly more likely than those at shelter B to test positive for FIV (p=0.0024) and FeLV (p=0.048). Male cats were more likely to be infected with FIV (odds ratio 27.1, p=0.001), and thin body condition and musculoskeletal disease were associated with risk of FeLV. Overall, FIV-positive and FeLV-positive cats were significantly older (median ages 5.1 and 4.75 years, respectively) than the uninfected populations (median ages 3.4 and 3.5 years, respectively). This study shows that the prevalence of these diseases varies between shelter populations. Local knowledge combined with the risk factors identified may be useful in focusing resources for population testing strategies.

Prevalence and risk factors for cats testing positive for feline immunodeficiency virus and feline leukaemia virus infection in cats entering an animal shelter in New Zealand

AIMS To estimate the prevalence of cats testing positive for antibodies to feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) antigens in domestic cats entering a New Zealand animal shelter, based on a commercial point-of-care ELISA, to identify risk factors associated with cats testing positive, and to compare the results obtained from the ELISA with those obtained using PCR-based testing. METHOD A cross-sectional study was performed on 388 cats entering the Royal New Zealand Society for the Prevention of Cruelty to Animals animal shelter in Auckland, New Zealand between 7 February 2014 and 30 May 2014. Whole blood samples were collected from each cat and tested for FIV antibody and FeLV antigen using a commercial point-of-care ELISA. Information on the signalment and health status of the cat at the time of entry was also recorded. Blood and saliva samples from a subset of cats were tested for FIV and FeLV proviral DNA using a real-time PCR assay. RESULTS Of the 388 cats in the study sample, 146 (37.6%) had been relinquished by owners, 237 (62.4%) were strays, and 5 (1.3%) were of unknown origin. Overall, 53/388 (13.7%) cats tested positive for FIV antibodies and 4/388 (1.0%) were positive for FeLV antigen. Stray cats had a higher FIV seroprevalence than relinquished cats (42/237 (17.8%) vs. 11/146 (7.5%); p=0.008). Of 53 cats that were FIV-seropositive, 51 (96%) tested positive for FIV proviral DNA using PCR testing of blood. Of these 51 cats, 28 (55%) were positive by PCR testing of saliva. Of the four cats that were FeLV antigen-positive by ELISA, two (50%) were positive for FeLV proviral DNA by PCR testing of blood. The odds of a cat being seropositive for FIV were greater for intact compared to desexed cats (OR=3.3; 95% CI=1.6-7.4) and for male compared to female cats (OR=6.5; 95% CI=3.2-14.0). CONCLUSIONS AND CLINICAL RELEVANCE The seroprevalence for FIV was 14% among cats entering an animal shelter in Auckland, whereas the prevalence of FeLV antigen-positive cats was only 1%. These findings suggest differences in the transmission dynamics of each virus in free-roaming cat populations in New Zealand. Our study also highlights the potential role of desexing cats in reducing transmission of FIV. However, further data from first-opinion veterinary practices are required to confirm that these findings may be generalised to the wider domestic cat population in New Zealand.

Analytical validation of a reference laboratory ELISA for the detection of feline leukemia virus p27 antigen

Feline leukemia virus (FeLV) is an oncogenic retrovirus of cats. Immunoassays for the p27 core protein of FeLV aid in the detection of FeLV infections. Commercial microtiter-plate ELISAs have rapid protocols and visual result interpretation, limiting their usefulness in high-throughput situations. The purpose of our study was to validate the PetChek FeLV 15 ELISA, which is designed for the reference laboratory, and incorporates sequential, orthogonal screening and confirmatory protocols. A cutoff for the screening assay was established with 100% accuracy using 309 feline samples (244 negative, 65 positive) defined by the combined results of FeLV PCR and an independent reference p27 antigen ELISA. Precision of the screening assay was measured using a panel of 3 samples (negative, low-positive, and high-positive). The intra-assay coefficient of variation (CV) was 3.9–7.9%; the inter-assay CV was 6.0–8.6%. For the confirmatory assay, the intra-assay CV was 3.0–4.7%, and the inter-assay CV was 7.4–9.7%. The analytical sensitivity for p27 antigen was 3.7 ng/mL for inactivated whole FeLV and 1.2 ng/mL for purified recombinant FeLV p27. Analytical specificity was demonstrated based on the absence of cross-reactivity to related retroviruses. No interference was observed for samples containing added bilirubin, hemoglobin, or lipids. Based on these results, the new high-throughput design of the PetChek FeLV 15 ELISA makes it suitable for use in reference laboratory settings and maintains overall analytical performance.

Feline immunodeficiency virus (FIV), feline leukaemia virus (FeLV) and Leishmania sp. in domestic cats in the Midwest of Brazil

ABSTRACT: This search aimed to investigate FIV and FeLV infections in domestic cats, analysing the epidemiological profile of the disease as well as additional infection with Leishmania sp. We evaluated 88 domestic cats for the presence of FIV, FeLV and Leishmania sp. infection. Eleven (12.5%) cats were positive for FIV infection, four (4.5%) were positive for FeLV, and two were co-infected. However, none was infected with Leishmania sp. The prevalence for FIV infection was higher than FeLV, and those observed in other regions, but no factor was associated with the infection by FIV and FeLV in this study.

Performance of 4 Point-of-Care Screening Tests for Feline Leukemia Virus and Feline Immunodeficiency Virus

Background

More than 3 million cats in the United States are infected with FeLV or FIV. The cornerstone of control is identification and segregation of infected cats.

Hypothesis/Objectives

To compare test performance with well‐characterized clinical samples of currently available FeLV antigen/FIV antibody combination test kits.

Animals

Surplus serum and plasma from diagnostic samples submitted by animal shelters, diagnostic laboratories, veterinary clinics, and cat research colonies. None of the cats had been vaccinated against FIV. The final sample set included 146 FeLV+, 154 FeLV−, 94 FIV+, and 97 FIV− samples.

Methods

Prospective, blind comparison to a gold standard: Samples were evaluated in 4 different point‐of‐care tests by ELISA antigen plate tests (FeLV) and virus isolation (FIV) as the reference standards. All test results were visually read by 2 blinded observers.

Results

Sensitivity and specificity, respectively, for FeLV were SNAP^® (100%/100%), WITNESS^® (89.0%/95.5%), Anigen^® (91.8%/95.5%), and VetScan^® (85.6%/85.7%). Sensitivity and specificity for FIV were SNAP^® (97.9%/99.0%), WITNESS^® (94.7%/100%), Anigen^® (96.8%/99.0%), and VetScan^® (91.5%/99.0%).

Conclusions and Clinical Importance

The SNAP^® test had the best performance for FeLV, but there were no significant differences for FIV. In typical cat populations with seroprevalence of 1–5%, a majority of positive results reported by most point‐of‐care test devices would be false‐positives. This could result in unnecessary segregation or even euthanasia.

Evaluation of rapid diagnostic test kits for feline leukemia virus infection using samples from naturally infected cats

Objectives

Feline leukemia virus (FeLV) is a potentially life-threatening oncogenic retrovirus. The p27 viral core protein is produced by the virus in infected feline cells, is found in the cytoplasm in several blood cells and can be free in the serum and plasma. ELISA or particle-based immunoassay are commonly used to detect the presence of the p27 core protein in samples obtained from blood. The objective of this study was to compare the performance of several in-clinic tests: the SNAP Feline Triple Test (IDEXX Laboratories), the WITNESS FeLV-FIV Test (Zoetis) and the VetScan Feline FeLV/FIV Rapid Test (Abaxis).

Methods

The sample population (100 positive, 105 negative samples) consisted of serum and plasma samples submitted to IDEXX’s worldwide reference laboratory for feline retrovirus testing. Virus isolation and reverse transcriptase PCR results were not available and so samples were judged to be positive or negative based on the results of the ViraCHEK FeLV (Zoetis) microtiter plate assay.

Results

The percentage of samples positive and negative for FeLV p27 antigen using the three in-clinic tests compared with the ViraCHEK method were as follows: IDEXX Feline Triple (positive 98.0%, negative 100%); Zoetis WITNESS (positive 79.0%, negative 97.1%); Abaxis VetScan (positive 73.0%, negative 97.1%).

Conclusions and relevance

The SNAP Feline Triple Test demonstrated a high level of agreement for FeLV-positive and FeLV-negative samples when assessed in this model. Results of FeLV assays can vary among tests.

Phylogenetic characterisation of feline immunodeficiency virus in naturally infected cats in Croatia indicates additional heterogeneity of subtype B in Europe

This study was performed on 29 domestic cats with a variety of clinical signs, possibly related to FIV infection. Blood samples were tested by a rapid immunochromatographic (ICA) procedure for detection of FIV antibodies. Subsequently, polymerase chain reaction (PCR) was performed to amplify a portion of the proviral gag gene. All 11 positive PCR products were sequenced and compared with previously reported FIV sequences. Croatian proviral isolates that could be amplified were clustered within subtype B, and additional heterogeneity was confirmed by the formation of three separate clusters. Phylogenetic analysis of circulating strains in Croatia and in southeast Europe is necessary to improve diagnostic methods and selection of the appropriate vaccinal strains.

Risk factors and effect of selective removal on retroviral infections prevalence in Belgian stray cats

The aim of this study was to evaluate the effect of several risk/protective factors and predictors on the prevalence of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) infections in 302 stray cats captured during a trap-neuter-release programme in a mixed urban-rural area from Belgium, from 2010 to 2012. The impact of selective removal of FIV-positive cats on the apparent prevalence in the remaining population over this three-year period was also assessed. The seroprevalences over three years were 18.8 per cent for FIV and 0.7 per cent for FeLV. For FIV, the seroprevalence decreased significantly from the first year of the programme (2010; 30.5 per cent) to the last (2012; 13.1 per cent). Sex (male) and age (adult and old cats) were risk factors, while the year of sampling (years 2011 and 2012) was a protective factor. Age, sex and location were the most relevant predictors of FIV status. The data presented in this study revealed a very high FIV seroprevalence in Belgian stray cats, while FeLV was almost absent. The selective removal of positive cats had a drastic effect on the FIV seroprevalence in the remaining cat population.

Seroprevalence of feline immunodeficiency virus and feline leukaemia virus in Australia: risk factors for infection and geographical influences (2011-2013)

OBJECTIVES

Our aim was to: (i) determine the current seroprevalence of feline immunodeficiency virus (FIV) and feline leukaemia virus (FeLV) in three large cohorts of cats from Australia; and (ii) investigate potential risk factors for retroviral infection.

METHODS

Cohort 1 (n = 2151 for FIV, n = 2241 for FeLV) consisted of cats surrendered to a shelter on the west coast of Australia (Perth, Western Australia [WA]). Cohort 2 (n = 2083 for FIV, n = 2032 for FeLV) consisted of client-owned cats with outdoor access recruited from around Australia through participating veterinary clinics. Cohort 3 (n = 169 for FIV, n = 166 for FeLV) consisted of cats presenting to Murdoch University Veterinary Hospital for a variety of reasons. Fresh whole blood was collected and tested using a commercially available point-of-care lateral flow ELISA kit that detects p27 FeLV antigen and antibodies to FIV antigens (p15 and p24) (cohorts 1 and 2), or one of two lateral flow immunochromatography kits that detect p27 antigen and antibodies to FIV antigen (p24 and/or gp40) (cohort 3). Data recorded for cats in cohort 2 included signalment, presenting complaint and postcode, allowing investigation of risk factors for FIV or FeLV infection, as well as potential geographical 'hot spots' for infection.

RESULTS

The seroprevalence of FIV was 6% (cohort 1), 15% (cohort 2) and 14% (cohort 3), while the seroprevalence of FeLV was 1%, 2% and 4% in the same respective cohorts. Risk factors for FIV infection among cats in cohort 2 included age (>3 years), sex (male), neutering status (entire males) and location (WA had a significantly higher FIV seroprevalence compared with the Australian Capital Territory, New South Wales and Victoria). Risk factors for FeLV infection among cats in cohort 2 included health status ('sick') and location (WA cats were approximately three times more likely to be FeLV-infected compared with the rest of Australia). No geographical hot spots of FIV infection were identified.

CONCLUSIONS AND RELEVANCE

Both FIV and FeLV remain important infections among Australian cats. WA has a higher seroprevalence of both feline retroviruses compared with the rest of Australia, which has been noted in previous studies. A lower neutering rate for client-owned male cats is likely responsible for the higher seroprevalence of FIV infection in WA cats, while the reason for the higher seroprevalence of FeLV in WA cats is currently unknown.

Vitamin D status in cats with feline immunodeficiency virus

Feline immunodeficiency virus (FIV) is a lentivirus that can lead to a syndrome of acquired immune dysfunction. Infected cats often remain asymptomatic for several years before immune dysfunction leads to an increased risk for the development of systemic diseases, neoplasia and opportunistic infections. FIV is structurally related to human immunodeficiency virus (HIV) and the pathogenesis of FIV‐related disease is similar to that seen in HIV‐infected patients. Observational studies have documented an association between low plasma vitamin D and HIV infection. Vitamin D status has been shown to be associated with HIV‐related disease progression, morbidity and mortality. The objective of this study was to examine the hypothesis that vitamin D status, as assessed by serum 25‐hydroxyvitamin D [25(OH)D] concentrations, are lower in cats with FIV infection compared to healthy control cats. Serum 25(OH)D concentrations were measured in 20 healthy cats, 39 hospitalized ill cats and 59 cats infected with FIV. Cats which were FIV infected had significantly lower 25(OH)D concentrations compared to healthy control cats. Serum 25(OH)D concentrations were not significantly different between FIV‐infected cats and hospitalized ill cats. Further investigations are warranted to determine whether vitamin D status influences the prognosis of cats infected with FIV.

Determining the feline immunodeficiency virus (FIV) status of FIV-vaccinated cats using point-of-care antibody kits

This study challenges the commonly held view that the feline immunodeficiency virus (FIV) infection status of FIV-vaccinated cats cannot be determined using point-of-care antibody test kits due to indistinguishable antibody production in FIV-vaccinated and naturally FIV-infected cats. The performance of three commercially available point-of-care antibody test kits was compared in a mixed population of FIV-vaccinated (n=119) and FIV-unvaccinated (n=239) cats in Australia. FIV infection status was assigned by considering the results of all antibody kits in concert with results from a commercially available PCR assay (FIV RealPCR™). Two lateral flow immunochromatography test kits (Witness FeLV/FIV; Anigen Rapid FIV/FeLV) had excellent overall sensitivity (100%; 100%) and specificity (98%; 100%) and could discern the true FIV infection status of cats, irrespective of FIV vaccination history. The lateral flow ELISA test kit (SNAP FIV/FeLV Combo) could not determine if antibodies detected were due to previous FIV vaccination, natural FIV infection, or both. The sensitivity and specificity of FIV RealPCR™ for detection of viral and proviral nucleic acid was 92% and 99%, respectively. These results will potentially change the way veterinary practitioners screen for FIV in jurisdictions where FIV vaccination is practiced, especially in shelter scenarios where the feasibility of mass screening is impacted by the cost of testing.

A survey of feline leukaemia virus antigenaemia among cats in eastern Austria: a retrospective analysis of serum samples routinely tested between 1996 and 2011

Objectives

The aim of this retrospective analysis was to determine the seroprevalence of feline leukaemia virus (FeLV) antigenaemia among owned cats in Vienna and the surrounding area.

Methods

Samples were tested between 1996 and 2011 by the Department of Clinical Virology at the University of Veterinary Medicine, Vienna, Austria. All samples were sent to the university as part of routine diagnostic procedures, either to determine infection in clinically symptomatic individuals or to rule out infection prior to vaccination. To allow for statistical comparison, samples analysed between 2008 and 2011 were pooled into one population (n = 444) and evaluated against samples tested in 1996 (n = 840). Furthermore, analyses of subgroups were undertaken to determine the effect of sex and age on the prevalence of FeLV antigenaemia.

Results

With respect to the samples tested at the University of Veterinary Medicine in Vienna, it was determined that the level of FeLV antigenaemia in eastern Austria between 1996 and 2011 was 5.6%. The proportion of FeLV antigenaemic cats was highly variable and has not fallen significantly over this period, despite advances in vaccination, and the education of pet owners and animal welfare charities.

Conclusions and relevance

This study confirms the importance of continued and regular vaccination against FeLV among Austrian cats, particularly those allowed access to the outdoors. Within the remit of this retrospective study, it was not possible to follow-up results of repeat testing or of other assays (PCR) of individual cats. As a result of this, no conclusions can be drawn as to the possibility of transient antigenaemic cats or false-positive enzyme-linked immunosorbent assay results.

Molecular detection, phylogenetic analysis, and identification of transcription motifs in feline leukemia virus from naturally infected cats in malaysia

A nested PCR assay was used to determine the viral RNA and proviral DNA status of naturally infected cats. Selected samples that were FeLV-positive by PCR were subjected to sequencing, phylogenetic analysis, and motifs search. Of the 39 samples that were positive for FeLV p27 antigen, 87.2% (34/39) were confirmed positive with nested PCR. FeLV proviral DNA was detected in 38 (97.3%) of p27-antigen negative samples. Malaysian FeLV isolates are found to be highly similar with a homology of 91% to 100%. Phylogenetic analysis revealed that Malaysian FeLV isolates divided into two clusters, with a majority (86.2%) sharing similarity with FeLV-K01803 and fewer isolates (13.8%) with FeLV-GM1 strain. Different enhancer motifs including NF-GMa, Krox-20/WT1I-del2, BAF1, AP-2, TBP, TFIIF-beta, TRF, and TFIID are found to occur either in single, duplicate, triplicate, or sets of 5 in different positions within the U3-LTR-gag region. The present result confirms the occurrence of FeLV viral RNA and provirus DNA in naturally infected cats. Malaysian FeLV isolates are highly similar, and a majority of them are closely related to a UK isolate. This study provides the first molecular based information on FeLV in Malaysia. Additionally, different enhancer motifs likely associated with FeLV related pathogenesis have been identified.

Primary immune-mediated thrombocytopenia and immune-mediated neutropenia suspected in a 21-week-old Maine Coon cat

CASE REPORT

A 21-week-old Maine Coon cat presented with an acute-onset coagulopathy. Severe concurrent thrombocytopenia and neutropenia were identified on peripheral blood smears and bone marrow cytology supported a peripheral consumptive process. Other than mild superficial haemorrhage, the cat was clinically well and screening for retroviral diseases, abdominal ultrasound examination, thoracic radiography, haematology and biochemistry panels did not identify an underlying disease. There was no historical pharmaceutical or toxicological trigger noted and the cat was from an area without endemic Ehrlichia spp. There was a rapid resolution of both cytopenias following treatment with immunosuppressive doses of prednisolone, though a mild relapse occurred during gradual prednisolone withdrawal and was responsive to a dose increase.

CONCLUSIONS

This report describes this combination of diseases for the first time in a cat and presents a younger patient than previously described with feline primary immune-mediated haematological disease.

Transmission of feline immunodeficiency virus (FIV) among cohabiting cats in two cat rescue shelters

Conflicting accounts have been published in the veterinary literature regarding transmission of feline immunodeficiency virus (FIV) between cohabiting cats in mixed households, and the mechanics of possible casual transmission, if it occurs, are poorly understood. Similarly, there are conflicting reports of vertical transmission of FIV. The aim of the present study was to document the FIV serological status of cats taken into two rescue shelters. At rescue shelter 1 (Rescue 1), cats cohabited in a multi-cat household of FIV-negative and naturally-infected, FIV-positive cats. A study was performed that combined a retrospective review of records of FIV serological status at intake (Test 1) and prospective FIV serological testing (Tests 2 and 3). Retrospective records were analyzed at rescue shelter 2 (Rescue 2), where FIV-positive queens with litters of nursing kittens were taken into the shelter, before being rehomed. FIV serology was performed on all kittens after weaning. Initial test results (Test 1) for 138 cohabiting cats from Rescue 1 showed that there were 130 FIV-negative cats and eight FIV-positive cats (six male neutered and two female spayed). A second test (Test 2), performed in 45 of the FIV-negative and five of the FIV-positive cats at median 28 months after Test 1 (range, 1 month to 8.8 years) showed that results were unchanged. Similarly, a third test (Test 3), performed in four of the original FeLV-negative cats and one remaining FIV-positive cat at median 38 months after Test 1 (range, 4 months to 4 years), also showed that results were unchanged. These results show a lack of evidence of FIV transmission, despite years of exposure to naturally-infected, FIV-positive cats in a mixed household. At Rescue 2, records were available from five FIV-positive queens with 19 kittens. All 19 kittens tested FIV-negative, suggesting that vertical transmission had not occurred.

Development and clinical evaluation of a rapid diagnostic kit for feline leukemia virus infection

Feline leukemia virus (FeLV) causes a range of neoplastic and degenerative diseases in cats. To obtain a more sensitive and convenient diagnosis of the disease, we prepared monoclonal antibodies specific for the FeLV p27 to develop a rapid diagnostic test with enhanced sensitivity and specificity. Among these antibodies, we identified two clones (hybridomas 8F8B5 and 8G7D1) that specifically bound to FeLV and were very suitable for a diagnostic kit. The affinity constants for 8F8B5 and 8G7D1 were 0.35 × 10⁹ and 0.86 × 10⁹, respectively. To investigate the diagnostic abilities of the rapid kit using these antibodies, we performed several clinical studies. Assessment of analytical sensitivity revealed that the detection threshold of the rapid diagnostic test was 2 ng/mL for recombinant p27 and 12.5 × 10⁴ IU/mL for FeLV. When evaluating 252 cat sera samples, the kit was found to have a kappa value of 0.88 compared to polymerase chain reaction (PCR), indicating a significant correlation between data from the rapid diagnostic test and PCR. Sensitivity and specificity of the kit were 95.2% (20/21) and 98.5% (257/261), respectively. Our results demonstrated that the rapid diagnostic test would be a suitable diagnostic tool for the rapid detection of FeLV infection in cats.

Virus-host interaction in feline immunodeficiency virus (FIV) infection

Feline immunodeficiency virus (FIV) infection has been the focus of several studies because this virus exhibits genetic and pathogenic characteristics that are similar to those of the human immunodeficiency virus (HIV). FIV causes acquired immunodeficiency syndrome (AIDS) in cats, nevertheless, a large fraction of infected cats remain asymptomatic throughout life despite of persistent chronic infection. This slow disease progression may be due to the presence of factors that are involved in the natural resistance to infection and the immune response that is mounted by the animals, as well as due to the adaptation of the virus to the host. Therefore, the study of virus-host interaction is essential to the understanding of the different patterns of disease course and the virus persistence in the host, and to help with the development of effective vaccines and perhaps the cure of FIV and HIV infections.

Clinical findings and survival in cats naturally infected with feline immunodeficiency virus

BACKGROUND

The clinical course and outcome of natural feline immunodeficiency virus (FIV) infection are variable and incompletely understood. Assigning clinical relevance to FIV infection in individual cats represents a considerable clinical challenge.

OBJECTIVE

To compare signalment, hematologic and biochemical data, major clinical problem, and survival among client-owned, FIV-infected, and uninfected domestic cats.

ANIMALS

Client-owned, domestic cats tested for FIV (n = 520).

METHODS

Retrospective, case control study. Logistic regression analyses were conducted to identify risk factors for FIV infection and to compare hematologic and biochemical data between cases and controls, after adjusting for potential confounders. Survival times were compared using Kaplan-Meier curves.

RESULTS

The prevalence of FIV infection was 14.6%. Mixed breed, male sex, and older age were risk factors for FIV infection. Hematologic abnormalities, biochemical abnormalities or both were common in both FIV-infected and uninfected cats. Lymphoid malignancies were slightly more common in FIV-infected than uninfected cats. Survival of FIV-infected cats was not significantly different from that of uninfected cats.

CONCLUSIONS AND CLINICAL IMPORTANCE

Multiple hematologic and biochemical abnormalities are common in old, sick cats regardless of their FIV status. Their presence should not be assumed to indicate clinical progression of FIV infection. A negative effect of FIV on survival was not apparent in this study.