Pan-European Study on the Prevalence of the Feline Leukaemia Virus Infection - Reported by the European Advisory Board on Cat Diseases (ABCD Europe)

Abstract

Feline leukaemia virus (FeLV) is a retrovirus associated with fatal disease in progressively infected cats. While testing/removal and vaccination led to a decreased prevalence of FeLV, recently, this decrease has reportedly stagnated in some countries. This study aimed to prospectively determine the prevalence of FeLV viraemia in cats taken to veterinary facilities in 32 European countries. FeLV viral RNA was semiquantitatively detected in saliva, using RT-qPCR as a measure of viraemia. Risk and protective factors were assessed using an online questionnaire to report geographic, demographic, husbandry, FeLV vaccination, and clinical data. The overall prevalence of FeLV viraemia in cats visiting a veterinary facility, of which 10.4% were shelter and rescue cats, was 2.3% (141/6005; 95% CI: 2.0%-2.8%) with the highest prevalences in Portugal, Hungary, and Italy/Malta (5.7%-8.8%). Using multivariate analysis, seven risk factors (Southern Europe, male intact, 1-6 years of age, indoor and outdoor or outdoor-only living, living in a group of ≥5 cats, illness), and three protective factors (Northern Europe, Western Europe, pedigree cats) were identified. Using classification and regression tree (CART) analysis, the origin of cats in Europe, pedigree, and access to outdoors were important predictors of FeLV status. FeLV-infected sick cats shed more viral RNA than FeLV-infected healthy cats, and they suffered more frequently from anaemia, anorexia, and gingivitis/stomatitis than uninfected sick cats. Most cats had never been FeLV-vaccinated; vaccination rates were indirectly associated with the gross domestic product (GDP) per capita. In conclusion, we identified countries where FeLV was undetectable, demonstrating that the infection can be eradicated and highlighting those regions where awareness and prevention should be increased.

Keywords: FeLV; RT-qPCR; gross domestic product at purchasing power parity per capita; prevalence; protective factors; retrovirus; risk factors; vaccination; veterinary sciences; virus shedding.

Figure A1

Schema of the pooling of the saliva samples: 96 samples (A1 to H12) were pooled to 20 pools. Each pool consisted of 200 µL; either 8 × 25 µL (horizontal pooling) or 12 × 16.7 µL (vertical pools). After pooling, each sample was present in two pools. Example: If a sample is FeLV-positive (black circle, B3), two pools resulted in positive RT-PCR results.

Figure 1

Origin and FeLV infection and vaccination status of the cats visiting veterinarians in the 30 European countries. (a) FeLV viraemia: black: all cats; red: FeLV-positive cats. (b) FeLV vaccination status: black: all cats; blue: FeLV vaccinated cats. The size of the circle represents the number of cats.

Figure 2

Age distribution of the cats: grey: FeLV-negative cats (left axis), black: FeLV-positive cats (right axis). Cats aged from one to six years were significantly more frequently FeLV-positive than younger or older cats (p_F < 0.0001; see also Table 3).

Figure 3

FeLV prevalence (on the left) and FeLV vaccination rates (on the right) in the different countries/country groups. In the FeLV vaccination rates, cats with unknown vaccination status were not included (~10% of the cats).

Figure 4

Relation between FeLV prevalence or FeLV vaccination rate and the gross domestic product (GDP) per capita purchasing power parity (PPP). (a) Relation between FeLV prevalence and GDP per capita using PPP in US dollars (USD); (b) Linear relation between FeLV vaccination rate and GDP per capita using PPP in USD (with the black points, the observed values; the line, the linear relation between the FeLV vaccination rate and the GDP per capita PPP and its 95% confidence interval, with the following equation: FeLV_vacc = −0.9698946 + (0.6052006 * GDP); (c) Density of the studentized residuals with the kernel density estimate and the normal density as reference. Kernel = epanechnikov, bandwidth = 0.4433.

Figure 5

Classification tree analysis for FeLV viraemia. Legend: Class: 0 = negative for FeLV; 1 = positive for FeLV. EU = Europe: N, North; W, West; E, East; S, South. Access: A, Indoor only; B, Indoor and outdoor; C, Outdoor only; D, Not sure. Pedigree: Y, Yes; N, No.

Figure 6

Distribution of salivary FeLV viral RNA loads in FeLV-positive healthy and sick cats. Loads are given as copies per PCR reaction conducted with 5 μL of total nucleic acid extracted from 100 μL of liquid from saliva swab samples.