EPIZOOTIOLOGY AND MANAGEMENT OF FELINE LEUKEMIA VIRUS IN THE FLORIDA PUMA

EPIZOOTIOLOGY AND MANAGEMENT OF FELINE LEUKEMIA VIRUS

IN THE FLORIDA PUMA

Mark W. Cunningham,1,10 Meredith A. Brown,2 David B. Shindle,1,3 Scott P. Terrell,4

Kathleen A. Hayes,5 Bambi C. Ferree,1 R. T. McBride,6 Emmett L. Blankenship,7

Deborah Jansen,7 Scott B. Citino,8 Melody E. Roelke,9 Richard A. Kiltie,1 Jennifer L. Troyer,9

and Stephen J. O’Brien2

1 Florida Fish and Wildlife Conservation Commission, 1105 SW Williston Road, Gainesville, Florida 32601, USA2 Laboratory of Genomic Diversity, National Cancer Institute-Frederick, Frederick, Maryland 21702, USA3 Current address: Conservancy of Southwest Florida, 1450 Merrihue Drive, Naples, Florida 34102, USA4 Disney’s Animal Kingdom, 1200 North Savannah Circle, Bay Lake, Florida 32830, USA5 Center for Retrovirus Research, The Ohio State University, 1925 Coffey Road, Columbus, Ohio 43210, USA6 Rancher’s Supply Inc., PO Box 725, Alpine, Texas 79830, USA7 Big Cypress National Preserve, National Park Service, Ochopee, Florida 34141, USA8 White Oak Conservation Center, Animal Science Building, 581705 White Oak Road, Yulee, Florida 32097, USA9 Laboratory of Genomic Diversity, SAIC-Frederick, Frederick, Maryland 21702, USA10 Corresponding author (email: [email protected])

ABSTRACT: Feline leukemia virus (FeLV) was not detected in Florida pumas (Puma concolorcoryi) in almost 20 yr of surveillance; however, the finding of two FeLV antigen-positive pumasduring the 2002–2003 capture season led to an investigation of FeLV in the population. BetweenJanuary 1990 and April 2007, the proportion of pumas testing FeLV antibody positive increased,with antibody-positive pumas concentrated in the northern portion of puma range. Five of 131(4%) pumas sampled between July 2000 and April 2007 were viremic, with all cases clustered inOkaloacoochee Slough (OKS). Clinical signs and clinical pathology at capture were absent orincluded lymphadenopathy, moderate-to-severe anemia, and lymphopenia. All viremic pumasdied; causes of death were septicemia (n52), intraspecific aggression (n52), and anemia/dehydration (n51). Outcome after FeLV exposure in pumas was similar to that in domestic cats,with evidence of regressive, latent, and persistent infections. Management of the epizooticincluded vaccination, and as of April 2007, 52 free-ranging pumas had received one or moreinoculations. Vaccinations were concentrated in OKS and in a band between OKS and theremainder of the puma population. There have been no new cases since July 2004; however, thepotential for reintroduction of the virus remains.

Key words: Feline leukemia virus, Florida panther, infectious disease, Puma concolor coryi,retrovirus, vaccination.

INTRODUCTION

The Florida puma (Puma concolorcoryi) is an endangered subspecies whoserange was contiguous with other pumapopulations (Young and Goldman, 1946).By the late 20th century, however, habitatdestruction, exploitation, and human pop-ulation growth had reduced the Floridapuma population to an isolated remnantnumbering an estimated 20 to 30 individ-uals (Nowak and McBride, 1974). Withprotection and management, including thetranslocation of eight pumas (Puma con-color couguar) from Texas in 1995 as partof a genetic restoration program (Seal,1994), the population rebounded to atleast 87 by 2003 (McBride, 2003). Conse-

quently, this greater density may haveincreased both exposure to domesticanimals and the risks of infectious diseasetransmission. Herein, we describe anepizootic of feline leukemia virus (FeLV)and its management in the free-rangingFlorida puma population.

Feline leukemia virus is a retrovirus ofdomestic cats (Felis silvestris catus). InFlorida, the prevalence of antigenemiaamong feral cats is ,4% (Lee et al., 2002).Transmission is usually by direct contact,and outcome after exposure depends onseveral host and viral factors. Most infec-tions are self-limiting in domestic cats,being eliminated shortly after exposure(regressive infection) or progressing tolatent infections before containment (Har-

Journal of Wildlife Diseases, 44(3), 2008, pp. 537–552# Wildlife Disease Association 2008

537

dy, 1980; Torres et al., 2005). Althoughdomestic cats developing regressive orlatent infections may be transiently vire-mic postexposure, they are not consideredimportant to the maintenance of thedisease in domestic cats. In approximatelyone third of exposed cats, viremia ispersistent and eventually results in clinicalsyndromes of immunosuppression, ane-mia, neoplasia, or a combination. Mortal-ity among persistently infected domesticcats is approximately fivefold that ofuninfected cats, and 83% die within3.5 yr (McClelland et al., 1980).

Feline leukemia virus in nondomesticfelids is rare. Reported infections incaptive nondomestic felids include aleopard cat (Felis bengalensis) (Rasheedand Gardner, 1981), puma (Meric, 1984),clouded leopard (Neofelis nebulosa) (Ci-tino, 1986), bobcat (Lynx rufus) (Sleemanet al., 2001), and several cheetahs (Acino-nyx jubatus) (Briggs and Ott, 1986;Marker et al., 2003). Despite extensivetesting for FeLV in free-ranging felidpopulations, published reports of FeLVinfections in the wild have been limited tothree pumas (P. concolor) (Rickard andForeyt, 1992; Jessup et al., 1993) and asand cat (Felis margarita) (Ostrowski etal., 2003). Ten to 24% of Europeanwildcats (Felis silvestris silvestris) alsowere FeLV antigen positive (Daniels etal., 1999; Fromont et al., 2000), althoughinterbreeding with domestic cats occurs inthis subspecies frequently (French et al.,1988). Most infections in nondomesticfelids were self-limiting. In a survey ofNorth American zoos, seven of 11 (64%)nondomestic felids that tested FeLVpositive initially were negative whenretested. The remaining four felids werenot retested, and they did not developclinical signs of FeLV (Kennedy-Stoskopf,1999). Persistent infections were seen in afree-ranging and a captive puma, a bobcat,and cheetahs, and clinical pathology andnecropsy findings included anemia, lym-phopenia, other cytopenias, lymphadenop-athy, septicemia, opportunistic infections,

and lymphoma (Meric, 1984; Briggs andOtt, 1986; Jessup et al., 1993; Sleeman etal., 2001).

Management of FeLV in domestic catpopulations includes vaccination, test-re-moval, or both. Inactivated whole-virusvaccines require an initial (prime) inocu-lation followed by booster in 3–6 wk. Inchallenge studies, whole-virus vaccinessuch as Fel-O-Vax LvkH and FevaxynFeLVH provided from 86 to 100% protec-tion (reviewed by Sparkes, 1997; Torres etal., 2005); however, protection after asingle inoculation is likely low. Fewstudies have examined duration of immu-nity beyond 1 yr, although a recombinantFeLV vaccine was shown to be protectiveover 3 yr (Hofmann-Lehmann et al.,1995). Vaccination has been used toprevent FeLV in captive nondomesticfelids; however, to our knowledge FeLVvaccination of free-ranging nondomesticfelids has not been reported.

In Florida pumas, routine FeLV enzyme-linked immunosorbent assay (ELISA) anti-gen testing was negative between 1978 andNovember 2002 (Roelke et al., 1993;Florida Fish and Wildlife ConservationCommission [FWC], unpubl. data); how-ever, during the 2002–2003 capture season,two pumas tested antigen positive. Thesefindings led to an investigation of FeLV inthe puma population and efforts to managethe epizootic.

MATERIALS AND METHODS

Florida puma capture, handling, and necropsy

Free-ranging pumas were captured by theFWC and National Park Service (NPS)between 1 July 2000 and 1 April 2007 insouthern peninsular Florida (south of 28uN) asdescribed by McCown et al. (1990) andMcBride and McBride (2007). Pumas wereimmobilized with ketamine HCl (CongareeVeterinary Pharmacy, Cayce, South Carolina,USA) combined with a-2 agonists tiletamineHCl/zolazepam HCl (TelazolH, Fort DodgeAnimal Health [FDAH], Fort Dodge, Iowa,USA), midazolam HCl (Abbott Laboratories,North Chicago, Illinois, USA), or both. Allanimals underwent physical examination. Ap-

538 JOURNAL OF WILDLIFE DISEASES, VOL. 44, NO. 3, JULY 2008

proximately 70–140 ml of blood was collectedin serum separator, ethylenediaminetetraace-tic acid (EDTA), Na-heparin, and ACD bloodtubes (BD Biosciences, Franklin Lakes, NewJersey, USA). Blood smears were made fromwhole blood at capture or with EDTA wholeblood approximately 6–24 hr after collection.Puma ages were either known (handled asneonates), or they were estimated from toothwear and gum line recession. Neonates werehandled as described by Land et al. (1998).

Pumas .4 mo old were vaccinated subcu-taneously against feline viral rhinotracheitis,feline calicivirus, feline panleukopenia virus(Fel-O-Vax PCT [FDAH], 1 ml, lower leftleg), and rabies (RabvacTM 3 [FDAH], 1 ml,lower right leg). Beginning June 2003, captiveand free-ranging pumas also were vaccinatedagainst FeLV (Fel-O-Vax Lv-K [FDAH] orFevaxyn FeLV, Schering-Plough AnimalHealth Corporation, Omaha, Nebraska, USA,2 ml, lower left leg). Between November 2003and April 2004, higher risk pumas (males,pumas in or near Okaloacoochee Slough[OKS]) were boosted (2 ml) intramuscularly(IM) by dart 3–16 wk after initial inoculation.Thereafter, pumas were boosted at recapture.Captured adult and juvenile pumas were fittedwith a very high frequency (VHF) or VHF/global positioning system radiocollar andlocated three times weekly.

Pumas were necropsied at the University ofFlorida College of Veterinary Medicine (UF-CVM, Gainesville, Florida, USA), Disney’sAnimal Kingdom (Celebration, Florida,USA), or the Wildlife Research Laboratory(FWC, Gainesville, Florida, USA). Organtissues and fluids (blood, urine, and aqueoushumor) were collected at necropsy. Blood wascentrifuged at 2,000 rpm for 10 min, and thesupernatant was decanted. Representativetissues were placed in 10% neutral bufferedformalin. Fixed tissues were embedded inparaffin, sectioned at 5–6 mm, and stainedwith hematoxylin and eosin. All tissues notanalyzed immediately were archived at 220 or270 C.

Diagnostics

Feline leukemia virus ELISA antibodyoptical densities (ODs) were performed atHansen Veterinary Immunology (Dixon, Cali-fornia, USA) using techniques described byLutz et al. (1980); ODs of ,0.25 wereconsidered negative, 0.25 to ,0.35 were lowpositive, 0.35 to ,0.5 were medium positive,and $0.500 were high positive. For statisticalanalyses, ODs $0.25 were considered positive.Antigen ELISAs (ViraCHEKH FeLV, Synbi-

otics Animal Health, San Diego, California,USA) were performed at the New York StateDiagnostic Laboratory (Cornell University,Ithaca, New York, USA). Adsorbing reagentswere used to remove heterophile antibody.Beginning November 2003, EDTA wholeblood from captured pumas was tested in thefield using a rapid immunochromatic assay(SNAP Combo, IDEXX Laboratories, West-brook, Maine, USA). The SNAP Combo alsowas used to test fluids collected from necrop-sied pumas, including blood collected from thethoracic cavity, heart, vessels, and marrowcavity, and aqueous humor. Blood smearsfrom ELISA antigen-positive pumas were alsotested by immunofluorescence assay (IFA) atthe National Veterinary Laboratory (FranklinLakes, New Jersey, USA) using techniquesdescribed by Hardy et al. (1973).

Conventional polymerase chain reaction(PCR) to detect provirus was performed atthe Laboratory of Genomic Diversity (Nation-al Cancer Institute [NCI], Frederick, Mary-land, USA) on tissues collected from pumas atcapture and necropsy. Methods and results aredescribed by Brown et al. (2008). Viralisolation and subgroup analysis were per-formed at the Center for Retrovirus Research(The Ohio State University, Columbus, Ohio,USA). Plasma from Florida Puma (FP) 109and FP115 was inoculated directly ontoHT1080 (human fibroblastoid), H927 (felinefibroblastoid), FEA (feline fibroblastoid), andprimary feline peripheral blood mononuclearcells (PBMCs) and tested by ELISA SNAP at2 and 4 wk. Peripheral blood mononuclearcells from FP123 and FP122 were cultured inlymphocyte medium (RPMI 1640 mediumwith 10% fetal bovine serum, 1 mM L-glutamine, and antibiotics) with 7 mg/ml con-canavalin A and 20 U/ml interleukin-2. Theinoculated cells then were cocultured with3201 (feline lymphoblastoid), Molt 4 (humanlymphoblastoid), and domestic cat PBMCs.Cultures were tested weekly for FeLV p27 byELISA.

Pumas were tested for feline immunodefi-ciency virus (FIV) antibodies by Western blotusing Petaluma antigen (New York StateDiagnostic Laboratory), a three-antigen (fca,pco, and ple) chemiluminescence methoddescribed by Troyer et al. (2005), or both.

Criteria for defining outcomes after exposure

Possible outcomes after exposure to FeLVin pumas were classified as regressive, latent,or persistent infections based on test results,duration of antigenemia, and presence ofclinical disease. Pumas with previous regres-

CUNNINGHAM ET AL.—FELINE LEUKEMIA VIRUS IN FLORIDA PUMAS 539

sive infections had a positive ELISA antibodyOD, but they were PCR and ELISA antigennegative. Latently infected pumas retainedprovirus in leukocytes at a level sufficient to bedetectable by conventional PCR, but theywere ELISA antigen negative. Persistentlyinfected pumas were ELISA antigen positiveand were IFA positive, were antigenemic for$16 wk, and/or developed FeLV-related dis-eases.

Statistics

Proportion of pumas positive for FeLVantibodies was calculated as the percentagewith ELISA ODs .0.25. Three binary cate-gorical predictors were considered: gender,FIV status, and location (north or south ofInterstate highway 75 [ca. 28.05uN]) (Fig. 1).Two predictors were treated as continuousvariables: age (in months/12) and sample date(in days/365.25 since 1 January 1960). Logis-tic regression using EgretH software (CytelSoftware Corporation, Cambridge, Massachu-setts, USA) was performed to investigateELISA antibody status as a binary responsevariable. Odds ratios and their 95% confi-dence limits were calculated for one state ofthe binary predictors in comparison with theother state. For the continuous predictors, theodds ratios represented the change in odds ofpositive FeLV per unit change in the predic-tor. Significant (P,0.05) difference from 1.0was determined for the odds ratios by theWald test. To account for correlation amongreplicate outcomes from individuals withmultiple test results, puma identity wasmodeled as a random effect within the logisticregression model and evaluated by a likelihoodratio test. Significant predictors emerging fromunivariate analyses (location and date) showedno significant interaction. Odds ratios arepresented from a bivariate logistic model, withlocation and date as additive predictors.

Vaccine trial

While in captivity at White Oak Conserva-tion Center (WOCC, Yulee, Florida, USA),three Florida pumas and three Texas pumaswere vaccinated against FeLV, monitored foradverse reactions, and sampled for antibodyresponse. Texas pumas were females approx-imately 10 yr old, and they were removedfrom the wild after completion of a geneticrestoration project. Florida pumas were incaptivity after being orphaned (FP113 andFP114 were siblings). Kittens (one male, twofemales) were 1 to 1.25 yr old when vaccinat-ed. Pumas were chemically immobilized,examined, sampled, and primed with Fel-O-

Vax LvK (2 ml IM); the procedure wasrepeated 3–6 wk later. FeLV ELISA antibodyODs were determined for serum collected atinitial inoculation (all pumas), booster (allpumas), and 15 days after the first booster(Texas pumas). Pumas were not challengedwith live FeLV. Two adult pumas weresimilarly primed and boosted with Fevaxyn-FeLV while in captivity recovering frominjuries. These pumas were monitored foradverse reactions, but FeLV antibody ODswere not determined. The vaccine trial wasapproved by the WOCC Institutional AnimalCare and Use Committee.

RESULTS

Diagnostics

Results of FeLV diagnostics and puta-tive classification of FeLV infections inFlorida pumas are presented in Table 1.ELISA antibody ODs were determinedfor 143 pumas (not vaccinated previously)sampled on 270 occasions between Janu-ary 1990 and April 2007; 24 (9%) totalsamples from 23 (16%) individuals werepositive. The proportion of positive anti-body ODs increased significantly withtime (odds ratio51.26, 95% confidenceinterval [CI]51.1121.42, P,0.001)(Fig. 2) and among pumas sampled northof Interstate highway 75 compared withsouth (odds ratio56.65, 95% CI52.072

21.4, P50.001). No positive ODs werefound in the extreme southern portion ofpuma range (Fig. 1). The probability ofhaving a positive antibody OD was notaffected significantly by age, gender, orFIV status for the complete data set orwhether analysis was limited to pumassampled north of Interstate highway 75and after the suspected onset of theepizootic (2001 and beyond). Of pumassampled on multiple occasions, six hadpositive ODs initially, but they werenegative when resampled 9 mo to 3 yrlater (Table 1).

Before July 2000, all pumas sampled(117 individuals sampled on 256 occa-sions) were ELISA antigen negative basedon published (Roelke et al., 1993) andunpublished data (FWC) and retrospec-


tive testing. During the study period, 142pumas were tested on 225 occasions forFeLV antigen by ELISA; the proportionof antigenemic (viremic) pumas $3 mo ofage, not vaccinated previously for FeLV,and sampled during the study period, was4% (5/131). All viremic pumas werecaptured in OKS, and they had overlap-ping home ranges. The proportion ofpumas with viremia in OKS (Fig. 1)

during the outbreak (approximately Janu-ary 2001 to June 2005) was 46% (5 of 11).Average age of viremic pumas (threemales, two females) was 4.85 yr (SD63.5, range 2.25–11 yr). FeLV antigenwas detected by SNAP test in thoracic,splenic, and venous blood, and aqueoushumor collected from viremic pumas atnecropsy, even in severely autolyzedcarcasses.

FIGURE 1. Distribution of free-ranging Florida pumas (Puma concolor coryi) sampled in South Floridabetween 1 July 2000 and 30 June 2005 not vaccinated previously against feline leukemia virus (FeLV).Putative classification of FeLV infections are based on enzyme-linked immunosorbent assay (ELISA)antibody, polymerase chain reaction (PCR; Brown et al., 2008), ELISA antigen, and immunofluorescenceassay results and clinical findings. Transient infections were positive only for FeLV antibodies, and latentinfections were PCR positive but antigen negative. OKS 5 Okaloacoochee Slough; CREW 5 CorkscrewRegional Ecosystem Watershed; FPNWR 5 Florida Panther National Wildlife Refuge; BCNP 5 Big CypressNational Preserve (N 5 north; C 5 central; S 5 south); SIR 5 Big Cypress Seminole Indian Reservation;PSSF 5 Picayune Strand State Forest; FSSP 5 Fakahatchee Strand State Forest.


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.CUNNINGHAM ET AL.—FELINE LEUKEMIA VIRUS IN FLORIDA PUMAS 543

Feline leukemia virus was cultured fromfour viremic pumas (FP132 was notcultured). Of the human and feline celllines inoculated, only primary domesticcat PBMCs, Molt 4 cells, and 3201 felinelymphoid cells became positive at 1–2 wkand remained positive for 4 wk. These celllines had continuous production of FeLVp27 as well as significant giant cellformation (Molt 4 cells) and cell death(3201 cells). Negative cultures were main-tained for up to 6 wk. Growth in felinecells was consistent with subgroup A virus.The ability of the sample from FP122 togrow in human cells (which would haveindicated the presence of subgroup B, C,or both in addition to subgroup A) may bean artifact due to prior coculture of thepuma cells with domestic cat PBMCs.

During the study period, 47% of pumastested were positive for FIV antibodies byWestern blot, ELISA, or both. Three offive (60%) FeLV antigen-positive pumasalso tested positive for FIV.

Clinical findings

Physical exam, selected complete bloodcount parameters, and significant necrop-sy findings for viremic pumas are listed in

Table 2. Suspected causes of death for thefive viremic pumas were septicemia(n52), intraspecific aggression (n52),and anemia/dehydration (n51). Timefrom first antigen-positive sample collec-tion to death averaged 9.25 wk (SD610.3, range 2–24.6 wk) in pumas viremicat capture (FP109, FP115, FP122, andFP123). Time from suspected exposure todeath for one puma (FP132) was 18 wk.The case-fatality rate for pumas withevidence of exposure to FeLV was 13%

(3/23 exposed [positive for FeLV antibod-ies]) to 22% (5/23) depending on theinclusion or exclusion respectively of twoviremic pumas dying from intraspecificaggression. This rate, however, may bealtered artificially because of false posi-tives or failure of some exposed pumas togenerate, or maintain, antibody levelssufficient to test positive by ELISA.

Vaccination

During the vaccine trial, no adversereactions were observed after initial inoc-ulation or booster, and most pumasdeveloped an antibody response. On 20August 2003, the three vaccine trialFlorida pumas were released into the

FIGURE 2. Percentage by year of free-ranging pumas sampled in Florida 1990 to 2007 testing positive forfeline leukemia virus antibodies by enzyme-linked immunosorbent assay.


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Florida Panther National Wildlife Refuge(FPNWR; FP113 and FP114) and privatelands east of Immokalee (FP116). Vacci-nation of free-ranging pumas began inNovember 2003, and as of 1 April 2007, 52free-ranging FeLV-negative pumas hadreceived at least one inoculation; of thesepumas, 26 were boosted. Distribution ofFeLV vaccinated pumas is presented inFig. 3. One puma (FP132) was primedapproximately 1–2 days after suspectedexposure to FeLV and boosted 4 wk later,but nevertheless it became persistentlyinfected. No other vaccinated pumas havebecome infected.

DISCUSSION

We investigated and managed an epi-zootic of FeLV in free-ranging Floridapumas. Diagnostic tests developed for usein domestic cats were used to diagnoseand help infer the pathogenesis of thedisease. Although diagnostic tests validat-ed for domestic animals but used onwildlife must be interpreted with caution(Hietala and Gardner, 1999), the testresults in this study were consistentbiologically and seemed to be suitable foruse in pumas.

The outcome in pumas after exposure toFeLV seems to be similar to that indomestic cats, with pumas showing evi-dence of regressive, latent, or persistentinfections (Table 1). These classificationsserve to simplify and categorize ourresults; in reality, FeLV exposure morelikely results in a continuum of possibleoutcomes from failure of viral replicationto persistent infection and death (Torreset al., 2005). Furthermore, prematuredeaths, severe autolysis, limitations ofdiagnostic tests, and limited ability toresample pumas while living precludedcomplete determination of disease pro-gression in all cases. Based on positiveELISA antibody ODs but antigen- andPCR-negative test results, many pumasexposed to the virus are able to clear theinfection. Assuming a similar pathogenesisT

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in domestic cats, pumas in this categorywould have cleared the infection withinweeks to months of exposure. The major-ity of domestic cats in this category areconsidered refractory to reinfection(Charreyre and Pedersen, 1991). PumaFP109 may have had a regressive infectionwhen captured in January 2003; at cap-ture, he was anemic, lymphopenic, andhad peripheral lymphadenopathy. Levy(1999) and Citino (1986) described similarsigns in domestic cats and a cloudedleopard, respectively, with transient vire-

mias. Puma FP109 also had a high ELISAantibody OD. Antibodies detectable byELISA occur shortly after infection indomestic cats (Lutz et al., 1980), and highantibody ODs in domestic cats are a goodprognostic indicator for recovery (Hof-mann-Lehmann et al., 2001). Poor carcassquality and an inconclusive FeLV IFAprecluded further assessment of FP109’sFeLV status.

Pumas classified as latently infectedpresumably failed to control viral replica-tion until later in the course of infection.

FIGURE 3. Distribution of free-ranging pumas receiving at least one inoculation against feline leukemiavirus in South Florida between August 2003 and April 2007. Darker shading depicts pumas that were dead asof April 2007. OKS 5 Okaloacoochee Slough; CREW 5 Corkscrew Regional Ecosystem Watershed; FPNWR5 Florida Panther National Wildlife Refuge; BCNP 5 Big Cypress National Preserve (N 5 north; C 5

central; S 5 south); SIR 5 Big Cypress Seminole Indian Reservation; PSSF 5 Picayune Strand State Forest;FSSP 5 Fakahatchee Strand State Forest.


Based on telemetry data (FWC, unpubl.data), at least one female (FP110) withevidence of a latent infection survivedexposure to at least two FeLV-positivemales without developing persistent vire-mia. This female continues to survive,reproduce, and remain nonantigenemicalmost 5 yr after diagnosis. No latentlyinfected pumas are known to have pro-gressed to a persistent infection.

Persistent infections were diagnosed infour pumas of which three were thoughtto have had FeLV-related disease condi-tions. Persistently infected pumas hadrelatively low antibody ODs, suggesting amuted humoral response to infection. Indomestic cats, low ELISA antibody ODsare characteristic of persistent infections(Hofmann-Lehmann et al., 2001). Non-neoplastic diseases, including secondaryinfections and anemia, were most com-monly associated with FeLV infection indomestic cats (Reinacher, 1989). Septice-mia, resulting from opportunistic bacterialinfections, is thought to have killed twoFeLV-infected pumas (FP115 andFP132). Nonregenerative anemias wereseen in FP109 and FP122 when capturedand may have been the cause of death inFP122. Progression of clinical diseaseseemed to be rapid in persistently infectedpumas. Although 50% of viremic domesticcats die within 6 mo of diagnosis (Jarrett,1983), adult cats experience a longerinduction period and less severe diseasecompared with younger age groups (Hoo-ver et al., 1976). All viremic pumas wereadults, and although the time of infectionis unknown in most infected pumas, theaverage time from positive sample collec-tion to mortality was just over 9 wk. Lackof supportive care (as in captive ordomestic cats) and presumably increasedexposure to pathogens may play a role inthis apparently more rapid clinical course.

In domestic cats, the most significantfactor affecting outcome after exposure isthought to be host age (Hoover et al.,1976), although genotype, immunocompe-tence, coinfection with FIV, route of

exposure, virus burden, and strain of virusalso may be important (Hoover et al.,1980; Grindem et al., 1989; Hoover andMullins, 1991; Rojko and Kociba, 1991).Nevertheless, the factors affecting theoutcome after exposure to FeLV indomestic cats remain largely unknown(Hofmann-Lehmann et al., 2001). Withthe average age of viremic pumas ap-proaching 5 yr, maturity did not seem toprotect against infection. In addition,genetic variation (based on expectedheterozygosity [He] at selected microsat-ellite DNA loci; Roelke, unpubl. data)within the puma population did not seemto influence significantly the outcomeafter exposure. Although some infectedpumas had very low genetic variation(likely the result of inbreeding and geneticdrift), at least two had He values muchgreater than the average for the popula-tion. Similarly, ancestral admixture did notseem to play a role because both inter-grade and canonical Florida pumas devel-oped FeLV and clinical disease (Brown etal., 2008; Johnson, unpubl. data). Bothretroviruses (FIV and FeLV) have over-lapping host cell tropism. In domestic cats,coinfection with FIV results in synergismof immunosuppression and severe clinicaldisease (Pedersen et al., 1990). The effectof pre-existing FIV infection in Floridapumas is unknown; however, some FIV-infected pumas were capable of resistingpersistent infection after FeLV exposure.Conversely, persistent FeLV infectionsoccurred in the absence of FIV infection.Finally, the pathogenicity of the FeLVstrain infecting pumas may play a role inthe apparent greater impact of FeLV onpumas. Based on genotyping, the strainisolated from pumas seems to be related toa virulent domestic cat strain (Brown etal., 2008).

The source of infection in pumas isunknown; however, in reports of FeLVinfection in nondomestic felids, the au-thors speculated or provided direct evi-dence that infected domestic cats were thesource. Kennedy-Stoskopf (1999) specu-


lated that consumption of FeLV-infecteddomestic cats by nondomestic felids wouldbe an effective way to transmit the virus,and domestic cat remains have been foundin the stomachs of necropsied pumas fromCalifornia (Jessup et al., 1993) and in twoFlorida pumas. Exposure of Florida pu-mas to domestic cats may be increasing asgrowing puma and human populationsexpand the urban-wildland interface. Thetransmission of FeLV from a domestic catto a puma is probably a rare event, butonce the species barrier was crossed, thevirus was likely spread puma to puma. Indomestic cats, prolonged exposure usuallyis necessary for transmission; however, wesuspect that FP132 was infected after anaggressive encounter with a viremic puma(FP123). Although FP132 was FeLVantigen negative when handled 1–2 daysafter the suspected encounter, he devel-oped persistent FeLV infection and diedwithin 5 mo. It is also possible that FP132was infected after capture or was exposedbefore the encounter with FP123 but wasnot yet viremic. Although FeLV is presentin the semen of domestic cats, venerealtransmission is not considered important(Hoover and Mullins, 1991). Nevertheless,the presence of infection in female pumassuggests that transmission also may occurduring courtship and mating. Higherpuma densities may facilitate puma-to-puma transmission. The population hasmore than tripled since the early 1990s(McBride, unpubl. data), whereas pumahabitat has been reduced.

Based on ELISA antibodies, PCRresults, and viral sequencing (Brown etal., 2008), the FeLV epizootic may havebegun on the FPNWR in early 2001. Onlyone of five pumas sampled in FPNWR inearly 2001 was positive for FeLV antibod-ies; however, all four pumas capturedthere in late 2001 were antibody positive.Based on telemetry data, three of thesesubadult pumas formed a loosely associat-ed group between August and December2001, possibly facilitating exposure if anywere viremic at the time. Indeed, one of

these pumas (FP96) had a latent infectionat necropsy in early 2002 (death due tointrapecific aggression). Although no pu-mas from FPNWR tested antigen positiveat capture or necropsy, we speculate thatone or more unknown viremic pumas mayhave spread the infection to other regions,including OKS. The finding by Brown etal. (2008) that all persistently and latentlyinfected pumas were infected with thesame strain of virus supports this hypoth-esis. Alternatively, there may have beenseparate introductions of the same virus.Regardless of the source, FeLV was likelyintroduced into OKS in 2002 resulting inpersistent infections in at least fourpumas. Since July 2004, however, noneof 84 pumas examined tested FeLVantigen positive, indicating that the epizo-otic may be over. Several factors may havecontributed to this finding: 1) the rapidprogression of disease may have limitedthe number of exposure events, 2) pumasare solitary generally, 3) some individualsare refractory to infection, 4) the Floridapuma population is small and thus lesslikely to sustain an FeLV epizootic (Fro-mont et al., 1998), and 5) some pumaswere vaccinated against FeLV.

Because of the unprecedented nature ofthis epizootic and serologic evidence ofsignificant exposure without persistentinfection, management of FeLV in thepuma population was conservative initial-ly. Few reported adverse effects in FeLV-vaccinated captive nondomestic felidscombined with the results of the vaccinetrial indicated FeLV vaccination was safefor free-ranging pumas; however, theefficacy of vaccination in free-rangingnondomestic felids is unknown. In domes-tic cats, inactivated whole-virus FeLVvaccines can be highly effective, althoughthe need for boosters limits their useful-ness in free-ranging populations. Manage-ment of FeLV in free-ranging pumasbegan in August 2003 with the release ofthree vaccinated subadults used in thevaccine trial. Thereafter, free-ranging pu-mas were primed at capture, and depend-


ing on FeLV risk, some were boosted bydart or at recapture. Assuming a minimumpopulation size of 87 (McBride, 2003), thelargest percentage of the living populationreceiving at least one inoculation duringthe epizootic was 23% (from 9 April to 28July 2004); the largest percentage primedand boosted was 13% (same time period).Using computer models, Lubkin et al.(1996) estimated that from 23% to 72% ofa closed domestic cat population with aFeLV prevalence of 10% must be vacci-nated effectively each year to eliminateinfection. Because vaccination efforts tar-geted the northern portion of puma range,the percentage vaccinated in these areaswas likely much greater (Fig. 3). Haydonet al. (2006) used modeling to demon-strate that the impact of infectious diseaseoutbreaks on endangered populations canbe curtailed by concentrating vaccinationsin habitat corridors. This targeted vacci-nation can be enhanced by concurrentlyvaccinating the core population. A similarstrategy was used for pumas; vaccinationswere concentrated initially in a bandbetween OKS and the remainder of thepopulation, followed by vaccinationthroughout their range. Test-removal ofinfected individuals, although proven tobe beneficial in closed domestic catpopulations, initially was not part of FeLVmanagement in pumas because of per-ceived risks for social structure disruptionand increased intraspecific aggression.Nevertheless, test-removal is now includ-ed in the Florida puma FeLV manage-ment plan.

Historically, the lack of antigen-positiveanimals and absence of clustered FeLVcases suggested that FeLV was not main-tained in free-ranging nondomestic felidpopulations (Kennedy-Stoskopf, 1999).The finding, however, of five viremicpumas over 2 yr suggests that the virushad, at least temporarily, become estab-lished in the puma population. Floridapumas consist of a single small population;thus, they are at greater risk for extinctionresulting from a catastrophic disease

epizootic (Beier et al., 2003). Therefore,Florida pumas should continue to bemonitored for and vaccinated againstFeLV, and new epizootics should bemanaged aggressively. Managers of otherfree-ranging nondomestic felid popula-tions similarly should monitor for FeLVantigen and consider vaccination, test-removal, or both should FeLV be intro-duced.

ACKNOWLEDGMENTS

We are deeply indebted to FWC, NPS, andUS Fish and Wildlife Service biologists andveterinarians who assisted in fieldwork andcollected samples over the past 30 yr. Facultyat UF-CVM provided diagnostic and editorialsupport and included D. Forrester, J. Levy, M.Sunquist, R. Alleman, C. Crawford, C. Buer-gelt, and B. Homer. We very much appreciatethe diagnostic support of S. Hansen and W.Hardy, Jr., and the technical assistance of W.Johnson and A. Roca. This project was fundedin part by FWC through the Federal Endan-gered Species Project E-1 and the FloridaPanther Research and Management TrustFund and with federal funds from the NCI,National Institutes of Health (NIH), undercontract N01-CO-12400. This Research wassupported in part by the Intramural ResearchProgram of the NIH, NCI, Center for CancerResearch. Funding was also provided by theSeaWorld and Busch Gardens ConservationFund. The content of this publication does notnecessarily reflect the views or policies of theDepartment of Health and Human Services,nor does mention of trade names, commercialproducts, or organizations imply endorsementby the US Government.

LITERATURE CITED

BEIER, P., M. R. VAUGHAN, M. J. CONROY, AND H.QUIGLEY. 2003. An analysis of scientific literaturerelated to the Florida panther. Final report.Florida Fish and Wildlife Conservation Com-mission, Tallahassee, Florida, 202 pp.

BRIGGS, M. B., AND R. L. OTT. 1986. Feline leukemiavirus infection in a captive cheetah and theclinical and antibody response of six captivecheetahs to vaccination with a subunit felineleukemia virus vaccine. Journal of the AmericanVeterinary Medical Association 189: 1197–1199.

BROWN, M., M. CUNNINGHAM, A. L. ROCA, J. TROYER,W. JOHNSON, AND S. J. O’BRIEN. 2008. Geneticcharacterization of feline leukemia virus (FeLV)in the free-ranging Florida panther population.Emerging Infectious Diseases 14: 252–259.


CHARREYRE, C., AND N. C. PEDERSEN. 1991. Study offeline leukemia virus immunity. Journal of theAmerican Veterinary Medical Association 199:1316–1324.

CITINO, S. B. 1986. Transient FeLV viremia in aclouded leopard. Journal of Zoo and WildlifeMedicine 17: 5–7.

DANIELS, M. J., M. C. GOLDER, O. JARRETT, AND D. W.MACDONALD. 1999. Feline viruses in wildcats inScotland. Journal of Wildlife Diseases 35: 121–124.

DUNBAR, M. R., P. NOL, AND S. B. LINDA. 1997.Hematologic and serum biochemical referenceintervals for Florida panthers. Journal of WildlifeDiseases 33: 783–789.

FRENCH, D. D., L. K. CORBETT, AND N. EASTERBEE.1988. Morphological discriminants of Scottishwildcats (Felis sylvestris), domestic cats (F catus)and their hybrids. Journal of Zoology 214: 235–259.

FROMONT, E., D. PONTIER, AND M. LANGLAIS. 1998.Dynamics of a feline retrovirus (FeLV) in hostpopulations with variable spatial structure.Proceedings of the Royal Society of London B265: 1097–1104.

———, A. SAGER, F. LEGER, F. BOURGUEMEISTER, E.JOUQUELET, P. STAHL, D. PONTIER, AND M.ARTOIS. 2000. Prevalence and pathogenicity ofretroviruses in wildcats in France. VeterinaryRecord 146: 317–319.

GRINDEM, C. B., W. T. CORBETT, B. E. AMMERMAN,AND M. T. TOMKINS. 1989. Seroepidemiologicsurvey of feline immunodeficiency virus infec-tion in cats of Wake County, North Carolina.Journal of the American Veterinary MedicalAssociation 194: 226–228.

HARDY, W. D. 1980. The virology, immunology andepidemiology of the feline leukemia virus. InFeline leukemia virus, W. D. Hardy, Jr., M.Essex and A. Mcclelland (eds.). Elsevier/North-Holland, New York, New York, pp. 33–78.

———, JR., L. J. OLD, P. W. HESS, M. ESSEX, AND S.M. COTTER. 1973. Horizontal transmission offeline leukemia virus. Nature 244: 266–269.

HAYDON, D. T., D. A. RANDALL, L. MATTHEWS, D. L.KNOBEL, L. A. TALLENTS, M. B. GRAVENOR, S. D.WILLIAMS, J. P. POLLINGER, S. CLEAVELAND, M. E.J. WOOLHOUSE, C. SILLERO-ZUBIRI, J. MARINO, D.W. MACDONALD, AND M. K. LAURENSON. 2006.Low-coverage vaccination strategies for theconservation of endangered species. Nature443: 692–695.

HIETALA, S. K., AND I. A. GARDNER. 1999. Validity ofusing diagnostic tests that are approved for usein domestic animals for nondomestic species. InZoo and wild animal medicine, M. E. Fowlerand R. E. Miller (eds.). W. B. Saunders,Philadelphia, Pennsylvania, pp. 55–58.

HOFMANN-LEHMANN, R., E. HOLZNAGEL, P. OSSENT,M. REINACHER, AND H. LUTZ. 1995. Recombinant

FeLV vaccine: long-term protection and effecton course and outcome of FIV infection.Veterinary Immunology and Immunopathology46: 127–137.

———, J. B. HUDER, S. GRUBER, F. BORETTI, B.SIGRIST, AND H. LUTZ. 2001. Feline leukemiaprovirus load during the course of experimentalinfection and in naturally infected cats. Journalof General Virology 82: 1589–1596.

HOOVER, E. A., AND J. I. MULLINS. 1991. Felineleukemia virus infection and disease. Journal ofAmerican Veterinary Medical Association 199:1287–1297.

———, R. G. OLSEN, W. D. HARDY, JR., J. P.SCHALLER, AND L. E. MATHES. 1976. Felineleukemia virus infection: age-related variationin response of cats to experimental infection.Journal of the National Cancer Institute 57: 365–369.

———, J. L. ROJKO, AND R. G. OLSEN. 1980. Factorsinfluencing host resistance to feline leukemiavirus. In Feline leukemia, R. G. Olsen (ed.).CRC Press, Boca Raton, Florida, pp. 69–76.

JARRETT, O. 1983. Recent advances in the epidemi-ology of feline leukaemia virus. VeterinaryAnnual 23: 287–293.

JESSUP, D. A., C. PETTAN, L. J. LOWENSTINE, AND N. C.PEDERSON. 1993. Feline leukemia virus infectionand renal spirochetosis in a free-ranging cougar(Felis concolor). Journal of Zoo and WildlifeMedicine 24: 73–79.

KENNEDY-STOSKOPF, S. 1999. Emerging viral infec-tions in large cats. In Zoo and wild animalmedicine, M. E. Fowler and R. E. Miller (eds.).W. B. Saunders, Philadelphia, Pennsylvania,pp. 401–410.

LAND, E. D., D. R. GARMAN, AND G. A. HOLT. 1998.Monitoring female Florida panthers via cellulartelephone. Wildlife Society Bulletin 26: 29–31.

LEE, I. T., J. K. LEVY, S. P GORMAN, P. C. CRAWFORD,AND M. R. SLATER. 2002. Prevalence of felineleukemia virus infection and serum antibodiesagainst feline immunodeficiency virus in un-owned free-roaming cats. Journal of the Amer-ican Veterinary Medical Association 220: 620–622.

LEVY, J. K. 1999. FeLV and non-neoplastic FeLV-related disease. In Textbook of veterinaryinternal medicine. 5th Edition. S. J. Ettingerand E. C. Feldman (eds.). W. B. Saunders,Philadelphia, Pennsylvania, pp. 424–432.

LUBKIN, S. R., J. ROMATOWSKI, M. ZHU, P. M. KULESA,AND K. A. J. WHITE. 1996. Evaluation of felineleukemia virus control measures. Journal ofTheoretical Biology 178: 53–60.

LUTZ, H., N. PEDERSEN, J. HIGGINS, U. HUBSCHER, F.A. TROY, AND G. H. THEILEN. 1980. Humoralimmune reactivity to feline leukemia virus andassociated antigens in cats naturally infected


with feline leukemia virus. Cancer Research 40:3642–3651.

MARKER, L., L. MUNSON, P. A. BASSON, AND S.QUACKENBUSH. 2003. Multicentric T-cell lym-phoma associated with feline leukemia virusinfection in a captive Namibian cheetah (Acino-nyx jubatus). Journal of Wildlife Diseases 39:690–695.

MCBRIDE, R. T. 2003. The documented pantherpopulation (DPP) and its current distributionfrom July 1, 2002 to June 30, 2003. LivestockProtection Company, Alpine, Texas, 11 pp.

MCBRIDE, R. T., JR., AND R. T. MCBRIDE. 2007. Safeand selective capture technique for jaguars inthe Paraguayan Chaco. Southwestern Naturalist52: 570–577.

MCCLELLAND, A. J., W. D. HARDY, AND E. E.ZUCKERMAN. 1980. Prognosis of healthy felineleukemia virus infected cats. In Feline leukemiavirus, W. D. Hardy, M. Essex and A. J. McClel-land (eds.). Elsevier/North-Holland, New York,New York, pp. 121–126.

MCCOWN, J. W., D. S. MAEHR, AND J. ROBOSKI. 1990.A portable cushion as a wildlife capture aid.Wildlife Society Bulletin 18: 34–36.

MERIC, S. M. 1984. Suspected feline leukemia virusinfection and pancytopenia in a western cougar.Journal of the American Veterinary MedicalAssociation 185: 1390–1391.

NOWAK, R. M., AND R. MCBRIDE. 1974. Status surveyof the Florida panther. In World Wildlife FundYearbook 1973–1974. Danbury Press, Danbury,Connecticut, pp. 112–113.

OSTROWSKI, S., M. VAN VUUREN, D. M. LENAIN, AND A.DURAND. 2003. A serologic survey of wild felidsfrom central west Saudi Arabia. Journal ofWildlife Diseases 39: 696–701.

PEDERSEN, N. C., M. TORTEN, B. RIDEOUT, E.SPARGER, T. TONACHINI, P. A. LUCIW, C. ACKLEY,N. LEVY, AND J. YAMAMOTO. 1990. Felineleukemia virus infection as a potentiating cofac-tor for the primary and secondary stages ofexperimentally induced feline immunodeficien-cy virus infection. Journal of Virology 64: 598–606.

RASHEED, S., AND M. B. GARDNER. 1981. Isolation offeline leukemia virus from a leopard cat cell lineand search for retrovirus in wild Felidae. Journalof the National Cancer Institute 67: 929–933.

REINACHER, M. 1989. Diseases associated with

spontaneous feline leukemia virus (FeLV) infec-tion in cats. Veterinary Immunology and Immu-nopathology 21: 85–95.

RICKARD, L. G., AND W. J. FOREYT. 1992. Gastroin-testinal parasites of cougars (Felis concolor) inWashington and the first report of Ollulanustricuspis in a sylvatic felid from North America.Journal of Wildlife Diseases 28: 130–133.

ROELKE, M. E., D. J. FORRESTER, E. R. JACOBSON, G.V. KOLIAS, F. W. SCOTT, M. C. BARR, J. F.EVERMANN, AND E. C. PIRTLE. 1993. Seropreva-lence of infectious disease agents in free-rangingFlorida panthers (Felis concolor coryi). Journalof Wildlife Diseases 29: 36–49.

ROJKO, J. L., AND G. J. KOCIBA. 1991. Pathogenesis ofinfection by the feline leukemia virus. Journal ofthe American Veterinary Medical Association199: 1305–1310.

SEAL, U. S. 1994. A plan for genetic restoration andmanagement of the Florida panther (Felisconcolor coryi). Report to the Florida Gameand Fresh Water Fish Commission, Conserva-tion Breeding Specialist Group, SSC/IUCN.White Oak Conservation Center, Yulee, Florida,23 pp.

SLEEMAN, J. M., J. M. KEANE, J. S. JOHNSON, R. J.BROWN, AND S. V. WOUDE. 2001. Feline leukemiavirus in a captive bobcat. Journal of WildlifeDiseases 37: 194–200.

SPARKES, A. H. 1997. Feline leukaemia virus: Areview of immunity and vaccination. Journal ofSmall Animal Practice 38: 187–194.

TORRES, A. N., C. K. MATHIASON, AND E. A. HOOVER.2005. Re-examination of feline leukemia virus:Host relationships using real-time PCR. Virology332: 272–283.

TROYER, J. L., Y. J. PECON-SLATTERY, M. E. ROELKE,W. JOHNSON, S. VANDEWOUDE, N. VAZQUEZ-SALAT,M. BROWN, L. FRANK, R. WOODROFFE, C.WINTERBACH, H. WINTERBACH, G. HEMSON, M.BUSH, K. A. ALEXANDER, E. REVILLA, AND S. J.O’BRIEN. 2005. Seroprevalence and genomicdivergence of circulating strains of feline immu-nodeficiency virus among Felidae and Hyaeni-dae species. Journal of Virology 79: 8282–8294.

YOUNG, S. P., AND E. A. GOLDMAN. 1946. The puma,mysterious American cat. Dover Publications,Inc., New York, New York, 358 pp.

Received for publication 16 July 2007.


EPIZOOTIOLOGY AND MANAGEMENT OF FELINE LEUKEMIA VIRUS IN THE FLORIDA PUMA

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