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Veterinary Immunology and Immunopathology 143 (2011) 243– 245

Contents lists available at ScienceDirect

Veterinary Immunology and Immunopathology

j ourna l ho me pag e: www.elsev ier .com/ locate /vet imm

ini review

review of feline leukemia virus and feline immunodeficiency viruseroprevalence in cats in Canada

usan Little ∗

ytown Cat Hospital, 422 McArthur Ave., Ottawa, Ontario K1K 1G6, Canada

r t i c l e i n f o

eywords:elineeLV seroprevalenceIV seroprevalence

a b s t r a c t

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are common andimportant infectious diseases of cats in Canada. Prevalence data are necessary to define pro-phylactic, management, and therapeutic measures for stray, feral and owned cats. Recently,comprehensive data on the seroprevalence of retrovirus infections of cats in Canada have

become available and are reviewed. Further investigation into geographic variations inretrovirus seroprevalence within Canada is warranted, and may provide information toimprove recommendations for testing and prevention. As well, more information is neededon FIV subtypes in Canada to improve diagnostics and vaccines, as well as to provideinformation on disease outcomes.

. Introduction

Feline leukemia virus (FeLV) and feline immunodefi-iency virus (FIV) are retroviruses causing two of the mostommon and important infectious diseases of cats. Dis-ases associated with FeLV and FIV may affect any organ,nd include lymphoma, blood dyscrasias, central nervousystem and ocular disease, gingivostomatitis, and sec-ndary and opportunistic infections. Organizations suchs the American Association of Feline Practitioners (Levyt al., 2008) and the European Advisory Board on Cat Dis-ases (Hosie et al., 2009; Lutz et al., 2009) have publisheduidelines for prevention and management of FeLV and FIVnfections. Prevalence data are necessary to define prophy-actic, management, and therapeutic measures for stray,eral and owned cats. Recently, comprehensive data on theeroprevalence of retrovirus infections of cats in Canadaave become available.

∗ Tel.: +1 613 741 2460; fax: +1 613 741 8463.E-mail address: catvet@vin.com

165-2427/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.vetimm.2011.06.018

© 2011 Elsevier B.V. All rights reserved.

2. Seroprevalence of FeLV and FIV in Canada

The seroprevalence of FeLV and FIV infection in a vari-ety of North American cat populations has been describedin several publications, but until recently the available dataapplied predominantly to the United States. Presented hereis a summary of FeLV and FIV seroprevalence for Canadiancats (Table 1). Yamamoto et al. (1989) evaluated the epi-demiologic features of FIV infection, and categorized catsas high risk (n = 2254) or healthy with low or unknown risk(n = 511). In the high risk group, 14% were FIV seroposi-tive compared to 1.2% in the healthy group. Further, in thehigh risk group, FIV seropositivity was more likely in malesthan females, in cats over 6 years of age than younger cats,and in free-roaming cats than confined cats. In the highrisk group, FeLV seroprevalence among 1609 cats was 13%;42 cats were reported to be from Canada, but no specificlocation was given. FIV seroprevalence was 19% among theCanadian cats. Within the healthy, low or unknown riskgroup of cats, 352 were reported to be from Canada, but nospecific location was indicated. FIV seroprevalence for the

healthy group as a whole was 1.2%, with no breakdown fororigin from Canada versus the United States.

More recently Levy et al. (2006), evaluated seropreva-lence of FeLV and FIV among North American cats as well as

244 S. Little / Veterinary Immunology and Immunopathology 143 (2011) 243– 245

Table 1Summary of FeLV and FIV seroprevalence studies in Canada.

Study Population Tested FIV FeLV

Yamamoto et al. (1989) Provinces not givenHigh risk (n = 42) 19% n/aLow risk (n = 352) 1.2% n/a

Hitt et al. (1992) Atlantic Canada(90.5% PEI)

7.6% n/a

Gibson et al. (2002)a PEIAdult feral males(n = 65)

13.8% 7.7%

Adult feral females(n = 74)

2.7% 5.4%

Little (2005)a OttawaUrban strays (n = 74) 23% 6.7%Owned cats (n = 152) 5.9% 2.6%

Levy et al. (2006)a AB, BC, NF, NS, ON,QC, SK (n = 325)

3.1% 2.5%

Little et al. (2009)a,b All Canadianprovinces(n = 11,144)

4.3% 3.4%

Berghuis (2009)a NF shelter cats(n = 591)

2.5% 6.1%

Ravi et al. (2010)a SK, MB, AB (n = 1205) 5.5% 3.5%

XX Labo, IDEXX

a Testing performed with SNAP Combo FeLV antigen/FIV antibody, IDEb Testing performed with PetChek FIV antibody and FeLV antigen ELISA

risk factors for seropositivity in a large prospective cross-sectional survey. In this study, 18,038 cats were tested at345 veterinary clinics (n = 9970) and 145 animal shelters(n = 8068). In this population of cats, seroprevalence of FeLVwas 2.3% and seroprevalence of FIV was 2.5%, while 0.3% ofcats were co-infected. The risk of seropositivity for eithervirus was higher in adult cats (>6 months) than juveniles,and in males than females. Other risk factors were access tooutdoors and concurrent illness. The highest risk for retro-virus infection was associated with being sick and feral,followed by being sick with access to outdoors. The studyincluded data on 325 cats from 7 Canadian provinces (AB,BC, NF, NS, ON, QC, SK), with 2.5% FeLV- and 3.1% FIV-seropositivity among them.

Little et al. (2009) conducted the first Canadian studyof FeLV and FIV seroprevalence and risk factors. Signal-ment, lifestyle factors, and test results for FeLV antigen andFIV antibody were analyzed for 11,144 cats from the 10Canadian provinces. More cats were tested at veterinaryclinics (n = 9588) than at animal shelters/rescue organiza-tions (n = 1556). Results showed seroprevalence for FeLVantigen was 3.4% and seroprevalence for FIV antibody was4.3%. Fifty-eight cats (0.5%) were seropositive for bothviruses. Significant risk factors for infection were age (>6months), presence of current illness, and access to out-doors. FeLV seropositivity was highest in intact females(7.3%) and intact males (7.1%) and FIV seropositivity washighest in intact males (7.4%). An inactivated dual-subtypevaccine against FIV became available in Canada in 2003;however, FIV vaccination status was not recorded or knownfor cats in this study. It was assumed that veterinarianswould be unlikely to test cats for FIV if they were known

to be vaccinated, and that the population of cats tested byshelters and rescue groups is unlikely to have a high rate ofFIV vaccination. Therefore, it seems likely that bias of FIV

ratories, Westbrook, Maine, USA. Laboratories, Westbrook, Maine, USA.

prevalence estimates caused by vaccination in this studywould be minimal.

Other studies have evaluated seroprevalence of FeLVand FIV in specific populations of Canadian cats. Hitt et al.(1992) evaluated sera (n = 671) submitted to a diagnos-tic laboratory in Atlantic Canada, with 90.5% of samplesfrom Prince Edward Island. FIV seroprevalence was 7.6%,and higher rates correlated with increased age and intactmale status. FeLV seroprevalence was not reported. Ofcats trapped in a neuter and release program in PrinceEdward Island (n = 185), Gibson et al. (2002) found 6.5%and 7.6% were seropositive for FeLV antigen and FIV anti-body, respectively. All kittens (n = 46) were negative forboth viruses, and seroprevalence of FeLV was higher inadult males than adult females. Three male cats (1.6%) wereseropositive for both FeLV and FIV.

Little (2005) evaluated seroprevalence in 246 cats fromthree demographic populations in Ottawa, Ontario. Sero-prevalence of FIV was highest in urban stray cats (23%)and lower in client-owned cats (5.9%) and in a feral catcolony (5%). The same groups of cats had 6.7, 2.6 and 0%seroprevalence of FeLV, respectively. Two male cats (0.8%)were seropositive for both FeLV and FIV infection.

In a study of Newfoundland cats predominantly fromshelters (n = 591), Berghuis (2009) found seroprevalenceof 6.1% and 2.5% for FeLV and FIV, respectively. Co-infection was uncommon (0.1%). The majority of retroviruspositive cats were unneutered males with access tooutdoors and signs of ill health. In a retrospectivestudy of 1205 samples from Saskatchewan, Manitobaand Alberta, Ravi et al. (2010) found seroprevalenceof FeLV and FIV was 3.5% and 5.5%, respectively. Co-

infection was uncommon (0.66%), and males had higherrates of seroprevalence than females. FIV infection wasalso significantly associated with illness (bite wounds,

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S. Little / Veterinary Immunology a

ethargy, and inflammatory oral disease) and increasingge.

Scant data exist on the prevalent FIV subtypes in Canada. study of 35 FIV isolates from Ontario by Reggeti andienzle (2004) identified subtype A as the most common23/35), even though subtype B was most common in theastern and central United States. Also, 7 cats with sub-ype B, 1 cat with subtype C, and 4 cats with A/B or A/Cnter-subtype recombinants were identified in the Cana-ian study.

. Conclusion

Retrovirus infections across Canada appear to be slightlyore common than in the United States. FIV infection isore frequent than FeLV infection, co-infection is relatively

ncommon, and factors such as sample origin, cat sex andutdoor access appear to influence infection rates. Furthernvestigation into geographic variations in retrovirus sero-revalence within Canada is warranted, and may provide

nformation to improve recommendations for testing andrevention. As well, further investigation of FIV subtypes

n Canada is necessary not only for developing molecularssays, but also for possible vaccine design and under-tanding of subtype association with disease outcomes.lthough testing for FeLV and FIV has been readily avail-ble in Canada for many years and vaccines against FeLVave been in widespread use for at least 15 years, felineetroviral infections remain common in Canada. Increasedwareness of seroprevalence data and available guidelinesor feline retrovirus testing and management among vet-rinarians, shelters, and pet owners may help improveesting and vaccination rates.

onflict of interest

All authors declare that there is no conflict of interest.

nopathology 143 (2011) 243– 245 245

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Berghuis, L., 2009. The prevalence of feline immunodeficiency virus (FIV)and feline leukemia virus (FeLV) in shelter cats of Newfoundland. B.Sc.(Honors) Thesis, Memorial University of Newfoundland.

Gibson, K., Keizer, K., Golding, C., 2002. A trap, neuter, and releaseprogram for feral cats on Prince Edward Island. Can. Vet. J. 43,695–698.

Hitt, M., Spangler, L., McCarville, C., 1992. Prevalence of feline immunode-ficiency virus in submissions of feline serum to a diagnostic laboratoryin Atlantic Canada. Can. Vet. J. 33, 723–726.

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