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Introduction
Recently, vaccination of cats has received scientific and public attentionlinked to the supposition that a range of rare adverse effects can arisefollowing vaccination. in cats, the most serious of these adverse conse-quences is the occurrence of invasive sarcomas (mostly fibrosarcomas),so-called ‘feline injection-site sarcomas’ (FiSSs), that can develop with-in the skin at sites of previous vaccination. despite extensive researchon the pathogenesis of these sarcomas, there is no definitive causal relationship that explains their occurrence and the direct link to vaccination. The most accepted hypothesis suggests that a chronicinflammatory reaction at the site of injection provides a trigger for subsequent malignant transformation.
Epidemiology and characterisation
in 1991, an increased incidence of tumours in cats that developed atinjection sites was first reported in the United States.1 This observationwas connected to an increased use of rabies and feline leukaemia virus(FeLV) vaccinations.2,3 As a consequence, these tumours were firstcalled feline ‘vaccine-associated sarcomas’. However, the subsequentfinding that other, non-vaccinal injectables can also cause this type oftumour has led to reclassification of these neoplasms as ‘feline injec-tion-site sarcomas’ (FiSSs). These tumours seem to be unique to cats,4
although comparable tumours have been reported in ferrets5 and veryoccasionally in dogs.6
FiSSs occur at sites typically used for vaccination and injections, suchas the interscapular region (Figure 1), the lateral thoracic or abdominalwall, the lumbar region, and the area of the semimembranosus andsemitendinosus muscles. FiSSs are most commonly located in the sub-cutis, but also can occur intramuscularly.7,8
FiSSs can occur as early as 4 months and up to 3 years after an injec-tion. They are characterised by invasive local growth in the subcutis,often with spread along fascial planes.9 Most FiSSs are fibro sarcomas,10
but other malignancies, such as osteosarcomas,11 chondrosarcomas,7
Journal of Feline Medicine and Surgery (2015) 17, 606–613
S P E C I A L ART I C L E
Overview: In cats, the most serious of adverseeffects following vaccination is the occurrence of invasive sarcomas (mostly fibrosarcomas): so-called ‘feline injection-site sarcomas’ (FISSs).These develop at sites of previous vaccination orinjection. They have characteristics that are distinctfrom those of fibrosarcomas in other areas andbehave more aggressively. The rate of metastasisranges from 10–28%.Pathogenesis: The pathogenesis of thesesarcomas is not yet definitively explained. However,chronic inflammatory reactions are considered thetrigger for subsequent malignant transformation.Injections of long-acting drugs (such asglucocorticoids, and others) have been associatedwith sarcoma formation. Adjuvanted vaccines induceintense local inflammation and seem therefore to be particularly linked to the development of FISS. The risk is lower for modified-live and recombinantvaccines, but no vaccine is risk-free.Treatment and prevention: Aggressive, radicalexcision is required to avoid tumour recurrence. The prognosis improves if additional radiotherapyand/or immunotherapy (such as recombinant felineIL-2) are used. For prevention, administration of anyirritating substance should be avoided. Vaccinationshould be performed as often as necessary, but as infrequently as possible. Non-adjuvanted,modified-live or recombinant vaccines should be selected in preference to adjuvanted vaccines.Injections should be given at sites at which surgery would likely lead to a complete cure; theinterscapular region should generally be avoided.Post-vaccination monitoring should be performed.
feline injection-site sarcoma
ABCD guidelines on prevention andmanagement
606 JFMS CLINICAL PRACTICE
European Advisory Board on Cat Diseaseswww.abcdcatsvets.org
www.abcd-vets.orgCorresponding author: Katrin Hartmann
Katrin Hartmann, Michael J Day*, Etienne Thiry, Albert Lloret, Tadeusz Frymus,Diane Addie, Corine Boucraut-Baralon, Herman Egberink, Tim Gruffydd-Jones,Marian C Horzinek, Margaret J Hosie, Hans Lutz, Fulvio Marsilio, Maria Grazia Pennisi, Alan D Radford, Uwe Truyen and Karin Möstl
*The ABCD is grateful to Professor Michael Day, of the School of Veterinary Sciences, University of Bristol, UK, who, though not a member of the Board, contributed to this article.
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rhabdomyosarcomas,7 malignant fibroushistio cytomas,7,11 and myofibroblastic sarco-mas8 have also been described.
FiSSs have histological characteristics thatare distinct from those of fibrosarcomas inother areas. Typically there is perivascularinfiltration of lymphocytes and macrophagesat the tumour periphery, a central area ofnecrosis, inflammation and local infiltration oftumour cells (Figure 2).10,12 FiSSs behave moreaggressively than sarcomas at other sites.13
The rate of metastasis ranges from 10–28%.14,15
The lung is the most common site of metasta-sis, followed by regional lymph nodes andabdominal organs, such as the kidney, spleen,intestine and liver.16,17
in the past 20 years, an epidemiological asso-ciation has been demonstrated between vaccina-tion and the later development of FiSS.3,13,18–21
The incidence of FiSS has been estimated at 1–4in every 10,000 vaccinated cats in the USA,22,23
and the ratio of injection-site to non-injection-site sarcomas increased from 0.5 in1989 to 4.3 in 1994.10 in one studyin the USA, reported rates of reac-tion were 0.3 FiSSs per 10,000 vaccinations and 11.8 postvaccinalinflammatory reactions per 10,000vaccinations in cats.22 if inflamma-tory reactions are a necessary prel-ude to FiSS, then these ratessuggest that 1 in 35–40 inflamma-tory reactions develop into FiSS. in the UK, the incidence of FiSSsseems to be relatively low (inci-dence risk of FiSS per year wasestimated to be 1 per 16,000–50,000cats registered by practices, 1 per10,000–20,000 cat consultations,and 1 per 5000–12,500 vaccinationvisits).24 one reason for the lowrate might be that rabies vaccina-tion is not a routine procedure forcats in the UK. one study inCanada investigated the annualprevalence of feline postvaccinalsarcomas among 11,609 feline skinmass submissions from 1992 to2010 and revealed no decrease indisease prevalence or increase inage of affected cats in response tochange in vaccination formulationor recommended changes in felinevaccination protocols.25
Pathogenesis
despite extensive research, thereis no definitive proof of thepathogenesis of FiSS. The mostwidely accepted hypothesis sug-gests that a chronic inflammatory
SPEC IAL ar t icle / Feline injection-site sarcoma
reaction at the site of an injection acts as a trig-ger for subsequent malignant transformation.Adjuvanted vaccines seem to be particularlylinked to the development of FiSS due to themore intense local inflammation associatedwith such products. This idea is supported byfrequent identification of adjuvants in histo-logical or ultrastructural investigations ofthese sarcomas.12,18
Many data suggest an association betweenvaccination and FiSS in cats. Aluminium, a vac-cine adjuvant, has been found in biopsy sam-ples of FiSS.26 in most inactivated vaccines, anadjuvant is added to enhance the inflammationat the site of injection, which is intended andnecessary when applying a killed agent inorder to trigger the necessary immuneresponse. However, this inflammation mightpotentially lead to malignant transformation.Traces of adjuvants can be seen in the inflam-matory reaction, specifically accumulatedwithin macrophages or multi nucleate giant
cells, and later in histological sections of FiSS in the trans-formed fibroblast.18 intracellularcrystalline particulate materialwas found in an ultrastructuralstudy in 5 of 20 FiSSs investigat-ed, and in one of the five caseswas identified as aluminium-based.12 Although no specific vaccine or adjuvant has beenincriminated,27 local irritationfrom adjuvant is thought to stim-ulate mainly fibroblasts to thepoint that malignant transforma-tion occurs.
At first, only rabies and FeLVvaccines were identified as riskfactors,3,13,23 but subsequentlyother vaccines, including vac-cines against feline panleuko -penia virus (FPV), felineherpesvirus-1 (FHV-1) and felinecalicivirus (FCV), were alsofound to be involved in thedevelopment of FiSS in somecases.13,23,28–30 in addition to vac-cines, injections such as long-act-ing glucocorticoids, penicillin,lufen uron,27,31,32 cisplatin33 andmeloxicam34 have been associat-ed with sarcoma formation. onestudy found that the frequencyof administration of long-actingglucocorticoid injections (dexa -methasone, methyl prednisoloneand triam cinolone) was signifi-cantly higher in cats with FiSS inthe interscapular region than incontrol cats.35 Fibrosarcomaswere also reported at the site of
a
b
c
FISSs areusually firm,indolent,
seemingly well-circumscribed,subcutaneousmasses that areoften not freelymoveable.
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angiogenesis. overexpression of growth fac-tors and oncogene activation have beendemonstrated in cats with FiSS and are sus-pected to play a role in tumour develop-ment.40–42
As vaccination against FeLV is associatedwith a higher risk of FiSS, some studieslooked at a possible role of FeLV and itsmutant feline sarcoma virus (FeSV) in thedevelopment of FiSS, but could not detecteither FeLV or FeSV in the tumours.43
Furthermore, no other viruses, includingfeline immunodeficiency virus, feline foamyvirus, polyomaviruses or papillomaviruseswere detected in tumour tissues.44–47 No evi-dence has been found to implicate replicationor expression of endogenous retroviruses inFiSS formation.45,46
The observation that not all cats developFiSS after vaccination suggests that theremight be a genetic predisposition. it has beensuggested that there is a higher incidence ofFiSS in siblings of affected cats, and that somecats tend to develop more than one FiSS.Alterations with unknown relevance such ashyperploidy,48 translocations49 and triploidy50
of oncogene and tumour suppressor loci have been found on extra chromosomes andmonosomic chromosomes in affected cats.Mutations have been identified in the tumour suppressor gene p53, which is implicated in cancer initiation and progres-sion in sarcoma tissue of cats with FiSS.51–55
A case-control study (50 domestic shorthaircats with a confirmed diagnosis of FiSS and100 disease-free matched controls) investigat-ing a possible association between polymor-phisms in the genomic sequence of the felinep53 gene and a predisposition to FiSS, found astrong association between FiSS and the presence of specific nucleotides at two of thepolymorphic sites.56 However, another study,conducted in Munich, Germany, could notreproduce these findings and observed noassociation with the polymorphismsdescribed.57
a deep, non-absorbable suture in one cat;36
around a surgical swab in the abdomen of onecat;37 adjacent to the site of microchip implan-tation in two cats;38,39 and associated with asubcutaneous fluid port device.38,39 This suggests that all inflammatory reactions, theoretically, have the potential to lead to thedevelopment of FiSS by triggering uncon-trolled proliferation of fibroblasts and myo -fibroblasts, which, in some cases, results inmalignant transformation.
Although many causes of inflammation areassociated with FiSS development, the riskseems to be higher for vaccines comparedwith other injections; among vaccines, the riskseems to be higher when adjuvanted vaccinesare used. Srivastav et al35 compared associa-tions between vaccine types and otherinjectable drugs with the development of FiSSin a case-control study of 181 cats with soft tis-sue sarcomas (cases), 96 cats with tumours atnon-vaccine regions (control group 1), and 159cats with basal cell tumours (control group 2).There was a significant association betweenthe administration of various types of vac-cines and other injectable products (eg, long-acting corticosteroids) and FiSS development.of 192 cats with sarcoma, 101 had vaccina-tions at the site of tumour development dur-ing the preceding 3 years, and 23 had receivedother injections.35 This study also showed thatadjuvanted inactivated vaccines were signifi-cantly more commonly associated with FiSSdevelopment than other vaccines; of 35 vacci-nated cats with sarcoma on the hindlimb, 25cats had received adjuvanted vaccines, sevencats had received modified-live virus (MLV)vaccines (FPV, FHV-1 and FCV), and only onecat had received a recombinant vaccine. Thesefindings also indicated that no vaccines arerisk-free.35
The mechanism by which the inflammatoryreaction causes tumour formation is not fullyunderstood. Growth factors promote prolifer-ation, can induce malignant transformation,and also can be involved in the regulation of
Figure 2 Histological sections of a 2 cm diameter mass removedfrom the lateral thorax of a 13-year-old domestic shorthaircat. A similar interscapular masshad been removed from this cat 2 months previously. (a) A focusof lymphoplasmacyticinflammation is contained within the surrounding sarcoma. (b) Higher magnification of the neoplastic tissue reveals a pleomorphic population ofneoplastic spindle cells withoccasional giant nuclei andirregular mitotic activity (arrow).Haematoxylin and eosin stain.Courtesy of Michael Day, School of Veterinary Sciences, University of Bristol, UK
European Advisory Boardon Cat Diseases
The European AdvisoryBoard on Cat Diseases(ABCD) is a body of expertsin immunology, vaccinologyand clinical feline medicine that issues guidelines onprevention and managementof feline infectious diseases inEurope, for the benefit of thehealth and welfare of cats.The guidelines are based oncurrent scientific knowledgeof the diseases and availablevaccines concerned.
The latest version of theguidance provided in thisarticle is available at
www.abcdcatsvets.org and www.abcd-vets.org
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Appropriate treatment should first includestaging and careful planning of the surgery,because aggressive, radical excision is crucial to avoid tumour recurrence. The prognosisimproves if, in addition to radical surgery,adjunctive treatments such as radiotherapy orimmunotherapy are used. Preoperatively, (con-trast-enhanced) computed tomography (CT) ormagnetic resonance imaging (MRi) should beobtained for staging, and to determine theextent of the tumour and the size of the radia-tion field required to maximise the chance of asuccessful outcome.58 it was shown that theactual size of tumours determined by CT couldbe twice that estimated at physical examina-tion.59,60 Surgeons should attempt to achievecomplete, en bloc, surgical tumour resectionwith at least 3 cm (ideally, 5 cm) margins61
[EBM grade iii] and the removal of one fascialplane underlying the tumour, because incom-plete resection can result in recurrence as earlyas 2 weeks after surgery [EBM grade iii].28,62
Treatment using surgical excision alone has arecurrence rate of up to 70%, with tumourregrowth usually occurring in the first 6 months after surgery [EBM grade iii].13
Tumour-free margins are very important for alonger disease-free interval, which was 700days when complete tumour excision wasaccomplished, but only 112 days for incompleteresection [EBM grade iii].63 However, evenwith clean surgical margins, the recurrence ratecan be as high as 50% [EBM grade iii].64
Preoperative or postoperative radiationtherapy significantly decreases recurrencerates and prolongs remission times,16,63,65
while the benefit of chemotherapy is notproven as large prospective randomised con-trolled trials are lacking. one non-randomisedstudy found no significant difference betweencontrol cats (surgery alone) and cats treatedwith surgery and doxorubicin [EBM gradeiii],66 while a recent study demonstratedchemotherapy benefits compared with histor-ical controls using a combination of neoadju-vant and adjuvant chemotherapy (threeepirubicin doses before and after surgery)[EBM grade iii].67 Chemotherapy mainlyremains an option for palliative treatment incats with non-resectable FiSS, when radiationtherapy is not available.
Additional immunotherapy appears to bepromising.68–70 Results of prospective ran-domised controlled studies of cytokine genetransfer techniques for adjuvant-immunologi-cal treatment of FiSS showed reduced recur-rence rates. in cats receiving gene therapy bythe peritumoural administration of histo-incompatible Vero cells expressing humaninterleukin-2 (hiL-2) in addition to surgery and
radiation therapy, only 5/16 (31%) had FiSSrecurrence, while 11/16 control cats (69%) thathad surgery and radiation therapy, but noimmunotherapy, had FiSS recurrence within 16months [EBM grade i].71 Use of neoadjuvantgene therapy using a non-viral vector thatexpresses feline granulocyte-macrophagecolony-stimulating factor (GM-CSF) or a com-bination of the feline genes GM-CSF, inter-leukin (iL)-2 and interferon-γ (iFN-γ) was welltolerated by cats [EBM grade i]68,69 and showedpromising results. Recombinant feline iL-2 isnow commercially available in Europe for the treatment of FiSS in combination with surgical excision and radiation therapy. in arandomised controlled clinical trial, adminis-tration of a recombinant canarypox virusexpressing feline iL-2 was well tolerated andresulted in a significantly longer median timeto relapse and a significant reduction in the riskof relapse at 1 year and 2 years [EBM grade i].70
Prevention
Prevention consists of three general consider-ations:
Choice of injection sitein general, injecting distally in a leg aids,where necessary, in the subsequent treatmentof sarcoma by amputation of the leg (becausethese tumours are very difficult to excise completely and often recur after resection).20
Administration of vaccines (or other injec-tions) between the scapulae is generally contraindicated because tumour resection isalmost impossible in this location.
To assess the acceptance of the recommen-dations of the Vaccine-Associated FelineSarcoma Task Force (VAFSTF), published in1996, a study involving 392 cats with FiSSscompared the anatomical locations oftumours between cases with FiSS diagnosedbefore and after publication of these recom-mendations.72 The proportions of FiSS signifi-cantly decreased in the interscapular (53% to40%) and right and left thoracic (10% to 4%and 9% to 1%, respectively) regions, whereas
EBM gradesThe ranking systemfor grading the levelof evidence ofvarious statementswithin themanagement andprevention sectionsof this article isdescribed on page 574 of thisSpecial Issue.
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Key considerations in the prevention of FISS< Injections in cats should always be given at sites at which surgery (such
as amputation of a limb or excision of lateral abdominal skin) would likelylead to a complete cure with the least complicated surgical procedure
< General recommendations to reduce the inflammatory reaction atinjection sites should be followed, such as avoiding the administration of irritating substances
< It is advised to vaccinate only as often as necessary and as infrequentlyas possible (eg, according to the principles of current vaccinationguidelines, avoiding FeLV vaccination in FeLV antigen-positive, FeLV PCR-positive or FeLV antibody-positive cats)
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the proportions of FiSS significantly increasedin the right thoracic limb (1% to 10%) and thecombined regions of the right pelvic limb withthe right lateral aspect of the abdomen (13% to25%) and the left pelvic limb with the left lateral aspect of the abdomen (11% to 14%).Thus, while veterinarians are complying withvaccination recommendations to some extent, a high proportion of tumours still developed in the interscapular region. There was also anincrease in lateral abdominal FiSSs, whichcould be attributable to aberrant placement ofinjections intended for the pelvic limbs. itremains the case that only administration ofvaccines as distally as possible on a limb allowsfor complete surgical margins if limb amputa-tion is required [EBM grade iii].73 Current datain Europe shows a similar situation. in a studyexamining the location of FiSSs in cats present-ed to the oncology service at the Universityteaching hospital in Munich, most still occurredbetween the scapulae (40%), followed by theright (19%) and left thoracic walls (13%).74
Unfortunately, there is still insufficient clini-cal information to enable evidence-based vaccine site recommendations. The majority ofsafety and efficacy data comes from licensingstudies in which vaccines are administeredsubcutaneously in the interscapular region(which should not be used for any injection inthe clinical setting). Current research indicatesthat radical surgical resection of injection-sitesarcomas including margins of at least 3 cm,but preferably 5 cm [EBM grade iii],61 is associ-ated with the highest response rate and long-term survival [EBM grade iii].15 With this inmind, the Feline Vaccination Advisory Panel ofthe American Association of Feline Practi -tioners (AAFP) conducted an informal surveyof veterinarians whose practices focused onradiation (12), surgical (36), and medical (44)oncology for opinions on what the preferredvaccination sites should be.62 These expertsagreed that distal to the stifle, followed by distal to the elbow, were their preferred sites.Nearly as popular was the tail. Res pondentsfrequently commented that vaccines should be administered as low on the leg as possible.They added that vaccination of cats resting in acrouched position often resulted in inadvertentinjection of the skin fold of the flank, leading totumours that were difficult to resect.62 This isreflected in a recent paper that found anincrease in lateral abdominal injection-site sar-comas since the publication of the VAFSTF’svaccination recommendations in 1996.61
Based on these expert opinions, the AAFPnow recommends in its new guidelines,62 con-sistent with the earlier (2006) guidelines,75 thatvaccines against FPV, FHV-1 and FCV shouldbe administered below the right elbow; FeLVvaccines should be administered below the
left stifle; and rabies vaccines should beadministered below the right stifle.62 So far,vaccination in the tail has not been considereda practical option. However, a recent pilotstudy demonstrated that vaccination in thetail was well tolerated and that tail-vaccinatedcats developed an antibody response compa-rable to that observed following injection ofthe vaccine distally in the leg [EBM grade ii].76
Further studies are warranted to confirmwhether this would be an alternative optionleading to equal protection rates.
Alternative recommendations are made bythe Vaccination Guidelines Group (VGG) ofthe World Small Animal Veterinary Asso -ciation, which recognises the practical difficul-ties often faced by veterinarians attemptingvaccination into limbs or the tail. The adviceof the VGG is that a preferred site for vaccinedelivery (and surgical resection of a FiSS thatmight arise) is the skin over the lateralabdomen. This is a procedure that appearswell tolerated in the majority of cats.
As a general recommendation, recording thesites of injections in the patient’s medical recordsis important. in addition, post-vaccination monitoring plays a vital role (see box).
Recommendations for reducinginflammatory reactionsin terms of preventing inflammatory reactionsat injection sites, there are a few recommenda-tions to follow. Cats should receive as few subcutaneous injections as possible. intra -muscular injections in cats should be avoidedbecause intramuscular tumours develop witha similar frequency, but are more difficult todetect early. Whenever feasible, cats shouldreceive drugs orally or intravenously. The subcutaneous injection of long-acting irritatingsubstances (such as long-acting glucocorti-coids) should be avoided.
one study examined potential risk factorswhen administering vaccines27 and few factors
Veterinarians should instruct theirclients to monitor vaccination (andother injection) sites for swelling orlumps in order todetect potential sarco-mas early and at a timewhen they still can beremoved successfully.Practitioners and
owners should followthe ‘3-2-1’ rule.Incisional wedge biopsies or totalremoval and histological examinationof any mass is warranted if the mass
is still present 3 months after vacci-nation, if the mass becomes largerthan 2 cm in diameter, or is increas-
ing in size 1 monthafter vaccination.In general, a diag-
nostic work-up is war-ranted when anycutaneous mass isnoted in a cat. FISSsare usually firm, indo-
lent, seemingly well-circumscribed,subcutaneous masses that are oftennot freely moveable.
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JFMS CLINICAL PRACTICE 611
< Vaccination of cats provides essential protection and should not be stopped because of the risk of feline injection-site sarcoma (FISS).
< Vaccines are not the only injectable medical products associated with FISS.
< An individual vaccination schedule is important. Cats should be vaccinated no more than necessary, in accordance with current guidelines.
< Appropriate sites for injection should be selected. The interscapular region shouldgenerally be avoided. Vaccines should be injected at a site from which a mass can easily be surgically removed, such as distally on a leg or in the skin of the lateral abdomen.
< Vaccines should be brought to room temperature prior to administration, but should not be kept unrefrigerated for hours.
< Whenever possible, subcutaneous, rather than intramuscular, injection should be performed.
< The preference is for: non-adjuvanted vaccines over those containing adjuvant; modified-live vaccines or recombinant vaccines over inactivated vaccines; and vaccines with a longduration of immunity.
< Post-vaccination monitoring should be performed. Any lump at the site of injection that is still present 3 months after vaccination, that is larger than 2 cm in diameter, or that it isincreasing in size 1 month after vaccination should be surgically removed.
KEY points
were associated with the development of FiSS.it was observed that the size of the needle andthe syringe, the velocity of injection, andwhether manual pressure was applied afterinjection or not, played no role. in contrast, thetemperature of the vaccine made a significantdifference, with cold vaccines being associatedwith a higher risk of FiSS development thanvaccines at room temperature.27 Thus, vaccinesshould be taken out of the refrigerator about15 minutes before injection, but not muchlonger, to avoid reduction in vaccinal efficacy.
if available, intranasal or oral vaccines wouldbe preferable over injectable vaccines in cats.However, in most countries only injectable vac-cines are available. Therefore, vaccines are preferred that cause the least subcutaneousinflammatory reaction. Vaccines without adju-vants should be used rather than adjuvant-containing vaccines, which means that MLV orrecombinant vaccines (eg, canarypox-vectoredvaccine) without adjuvant are preferred overinactivated vaccines with adjuvants.
it has been shown that recombinant canary-pox-vectored vaccines cause less inflamma-tion at the injection site. This wasdemonstrated in rats,77 and in a study in cats,in which the typical granulomatous inflam-mation did not develop at the injection sitewhen using these particular vaccines.78 Anextensive study investigating the subcuta-neous tissue response following administra-tion of a single dose of multi-componentvaccines confirmed these findings.79 Threegroups of 15 cats were injected with one ofthree vaccines or saline as a negative control;cats in group A received a non-adjuvantedrecombinant canarypox-vectored FeLV vac-
cine; cats in group B received an FeLV vaccinewith a lipid-based adjuvant; and cats in groupC were vaccinated with an FeLV vaccine adju-vanted with an alum-Quil A mixture. on days7, 21 and 62 post-vaccination, significantlyless inflammation was associated with admin-istration of the non-adjuvanted recombinantcanarypox-vectored vaccine. The inflamma-tion was most severe in the cats receiving thealuminium-based adjuvant. Cats receivingadjuvanted vaccines had evidence of residualadjuvant material accumulated withinmacrophages even at 62 days post-vaccina-tion.79 in a case-control study investigatingassociations between vaccine types and devel-opment of FiSS, adjuvanted inactivated vac-cines were significantly more commonlyassociated with sarcoma development thanother vaccines; of 35 vaccinated cats with sar-coma on the hindlimb, 25 cats had receivedadjuvanted vaccines, seven cats had receivedMLV vaccines (FPV, FHV-1 and FCV), whileonly one cat had received a recombinantcanarypox-vectored vaccine [EBM grade iii].35
Vaccination schedulesFinally, to prevent development of FiSS, catsshould be vaccinated no more than necessary.Therefore, long vaccination intervals shouldbe applied in adult animals; vaccines (such asrabies vaccines and FPV vaccines) that arelicensed for 3 year or even 4 year boostersshould be preferred; no FeLV or rabies vacci-nations should be administered to indoor-only cats; and immune cats should not bevaccinated (eg, if antibodies are detected).This confirms the necessity of individual vaccination schedules.
Funding
The authors receivedno specific grant fromany funding agency inthe public, commercialor not-for-profit sectorsfor the preparation ofthis article. The ABCdis supported by Merial,but is a scientificallyindependent body andits members receive nostipends from Merial.
Conflict of interest
The authors do nothave any potentialconflicts of interest to declare.
Recording the sites ofinjections
in the patient’smedicalrecords isimportant.
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