192 Journal of Swine Health and Production — July and August, 2004

SFA, JLS: Department of Veterinary Clinical Sciences, Purdue University, Lafayette, Indiana.

CAM: Indiana State Board of Animal Health, Indianapolis, Indiana.

SAS: Foreign Animal Disease Diagnostic Laboratory, USDA, APHIS, VS, NVSL, Greenport, NewYork.

GWS, MEW: Animal Disease Diagnostic Laboratory, Purdue University, Lafayette, Indiana.

Corresponding author: Dr Sandra F. Amass, Purdue University, VCS/Lynn, 625 Harrison St, WestLafayette, IN 47907-2026; Tel: 765-494-8052; Fax: 765-496-2608; E-mail: amasss@purdue.edu.

This article is available online at http://www.aasv.org/shap.html.

Amass SF, Schneider JL, Miller CA, et al. Idiopathic vesicular disease in a swine herd in Indiana. J Swine Health Prod. 2004;12(4):192–196.

Case report Peer reviewed

Idiopathic vesicular disease in a swine herd in IndianaSandra F. Amass, DVM, PhD, Diplomate ABVP; Jessica L. Schneider, RVT; Cheryl A. Miller, DVM; Samia A. Shawky, DVM, PhD;Gregory W. Stevenson, DVM, PhD, Diplomate ACVP; Mary E. Woodruff, MS

SummaryIdiopathic vesicular disease was reported inpigs of all ages during a 7-month period onan 1840-sow, three-site farrow-to-finishswine herd in Indiana. In 8- to 10-week-old growing pigs recently moved from thenursery (Site 3) to Sites 1 and 2, erosionsoccurred primarily on the coronary band,causing coronary separation and lameness.Some growing pigs also had lesions on thesnout and in the oral cavity. A few gestat-ing sows in Sites 1 and 2 were affected pri-

marily with snout lesions, and some littersof piglets were febrile and had coronaryband lesions that resolved by 16 days ofage. Pigs in Site 3 were not affected. Clini-cal signs were indistinguishable from exoticvesicular diseases such as foot-and-mouthdisease. A foreign animal disease investiga-tion ruled out an exotic disease as the cause.An etiologic agent was not identified; how-ever, porcine enterovirus was isolated fromtissue samples of growing pigs. Porcine en-teroviruses are ubiquitous, and the isolate

was considered a contaminant in this case.Practitioners are encouraged to be vigilantobservers and reporters of clinical signsconsistent with exotic diseases.

Keywords: swine, idiopathic vesicular dis-ease, enterovirus

Received: October 24, 2003Accepted: February 12, 2004

Lameness, coronary band separation,vesicular lesions, or combinations ofall three were observed in approxi-

mately 800 of 1000 growing pigs (8 to 10weeks old) during a routine February herdvisit on an 1840-sow farrow-to-finish swineherd in Indiana. The clinician and veterinarytechnologist immediately considered theexotic animal disease differentials for ve-sicular diseases and telephoned the StateBoard of Animal Health from outside thebuilding housing the affected pigs. A For-eign Animal Disease Diagnostician (FADD)arrived at the farm within 1.5 hours.

Initial outbreak of vesiculardiseaseCase descriptionThe main farm consists of two sites (Sites 1and 2) approximately 0.8 kilometers apart,that house breeding, gestating, farrowing,and overflow finishing pigs. At 9- to 16-

days of age, all pigs are weaned from thesesites to an offsite nursery (Site 3) locatedapproximately 3.2 kilometers away. Eachsite has separate animal caretakers. Periodi-cally, groups of 500 to a thousand 6- to 8-week-old pigs are moved from Site 3 toSites 1 and 2 for finishing. The affectedpigs had been moved from Site 3 (curtainand mechanically ventilated wean-to-finishbuilding with concrete slatted flooring anddeep pit) to Site 2 (curtain-sided finisherwith concrete slatted flooring and deep pit)1 week before the outbreak. Pigs from thesame group that had not been moved fromSite 3 remained clinically healthy and freeof lesions.

Affected pigs were lethargic; however, man-agers did not report a decrease in feed intakeor an increase in mortality. A single dyspneicpig died within minutes of first observationof clinical signs. Cursory examination ofthis pig revealed 1-mm to 1-cm rupturedvesicles on the tongue and oral and gingival

mucosa. The differential diagnoses includedfoot-and-mouth disease (FMD), vesicularstomatitis (VS), swine vesicular disease(SVD), vesicular exanthema of swine(VES), parvovirus, mycotoxicosis, and idio-pathic vesicular disease. The lesion patternwas not consistent with a chemical burn orother contact irritation.

Lesions and sample collectionFurther examination revealed that approxi-mately 80% of growing pigs in this grouphad coronary band lesions on at least onefoot, and approximately 20% of pigs hadsnout lesions consisting of well-circumscribederosions or ruptured vesicles. The dead pighad bronchopneumonia, but no other in-ternal lesions were noted. One growing pigwith coronary band lesions was humanelyeuthanized. This pig had two 2- to 3-mmlesions on the tongue, interpreted as rupturedvesicles or erosions; a 4-mm lesion on thelip; and a 3-mm lesion on the oral mucosa.Ruptured vesicles were observed on thesnouts or in the nares of eight gestatingsows at Site 2, and fluid-filled vesicles wereobserved on the snouts of two other sowsin the same barn. No other abnormalitieswere noted.

Fresh and fixed samples of tongue, snout,gingival mucosa, feet, and heart were col-lected from the two dead growing pigs.Blood was collected from four additionalgrowing pigs and two sows with intactvesicles, and vesicular fluid was collected

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from these sows. Samples were shippeddirectly to Foreign Animal Disease Diag-nostic Laboratory (FADDL), USDA,APHIS, VS, NVSL, Plum Island, NewYork.

Quarantine proceduresThe farm was quarantined by the state vet-erinarian. The owner was notified verballyand in writing that all movement of swinefrom the premises was prohibited until thequarantine was released. A brief overviewof vesicular diseases was discussed withfarm personnel. Care of affected pigs waslimited to personnel who had already beenexposed, and other employees were prohib-ited access to affected pigs. Pig movementwas minimized to the extent possible, andwhen not possible, was restricted to move-ment within affected sites. Movement wasnot further restricted because it was likelythat the entire site was already contami-nated: if an exotic disease was diagnosed,animals would be culled on the basis of siterather than building or room. Employeesowning animals susceptible to vesiculardiseases were instructed not to contact sus-ceptible animals and to find designatedcaretakers for these animals until quarantinewas released.

Diagnostic testing and resultsSerum samples from infected and contactpigs were negative for antibodies to FMD(virus infection associated antigen assay)and VES (indirect immunofluorescent an-tibody assay). Antigen to or nucleic acid ofFMD, SVD, and VS viruses were not de-tected in the affected feet, snout, oral mucosa,or tongue, as determined by antigen-captureELISA, antigen complement fixation, andpolymerase chain reaction (PCR) assays.The following evening, 24 hours after thesamples had been submitted, the quarantineimposed by the state veterinarian was re-moved from the herd on the basis of thenegative presumptive diagnosis, while virusisolation tests were still pending at FADDL.Later, virus isolation tests at FADDL de-tected a group 1 porcine enterovirus incoronary band lesions.

The farm owner consented to the herdveterinarian’s request for continued volun-tary quarantine of the herd, despite removalof the state quarantine, until a diagnosiswas made. Two days after the initial incident,the original veterinarian and veterinarytechnologist returned to the infected site

with a pathologist to collect additionalsamples of blood, tissue, and feed. At thattime, in 8-to 10-week-old growing pigs,lesions on the coronary band were mostprevalent (Figure 1), and few snout or orallesions were noted (Figure 2). Snout lesions

were noted in gestating sows (Figures 3, 4,and 5). Ten growing pigs in the affectedgroup were identified by ear tag, and serialblood samples were collected from thesepigs at the time of identification and 2 and4 weeks later. Fresh and formalinized tissue

Figure 2: Oral erosions and ulcers in an 8- to 10-week-old pig, representative ofthose observed in an estimated 20% of growing pigs in groups affected withvesicular lesions found primarily on the coronary band.

Figure 1: Coronary band lesion in a growing pig. In groups of 500 to 1000 pigs8 to 10 weeks old, up to 80% were affected with similar lesions on at least onefoot.

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and 11 through 13.1 Microscopic evaluationof coronary band skin revealed epithelialinfarcts with acanthomatous hyperplasiaand orthokeratotic hyperkeratosis. Mycotoxinscreens of feed samples for aflatoxin, anddeoxynivalenol, ochratoxin, zearalenone,T-2 toxin, and diacetoxyscirpenol, werenegative.

Second outbreak of vesiculardiseaseCase descriptionA second group of 500 growing pigs wastransported from Site 3 to Site 1 one weekafter the initial outbreak. One week later, 2weeks after the initial outbreak, approxi-mately 40% of transported pigs had coronaryband lesions and three pigs had snout lesions.One pig was febrile (rectal temperature40.7˚C). Additionally, five sows at Site 1had erosions on their snouts, interpreted asruptured vesicles, and three litters of 7-day-old piglets at Site 1 had coronary band le-sions. Piglets were afebrile and sows wereotherwise asymptomatic. Previously affectedSite 2 growing pigs were active. Epithelialproliferation around the coronary band wasnoted in 10 to 15% of pigs, and one deadpig had oral and gingival lesions 2 cm indiameter. Approximately 5% of sows atSite 2 had erosions on snouts suggestive ofruptured vesicles.

Quarantine and diagnostic testresultsThe herd was again quarantined by thestate veterinarian. Tissue and blood samplescollected from an 8-week-old pig and a 7-day-old piglet from Site 1 were split, withhalf of each sample submitted to FADDLto rule out an exotic disease by repeatingthe tests listed previously. The other half ofeach sample was frozen at -80˚C. AfterFADDL results had eliminated exotic dis-eases from the differential, these sampleswere submitted to PUADDL to rule outother known pathogens and to attempt toisolate previously undetected bacteria orviruses. Results of bacterial culture, virusisolation, fluorescent antibody testing, andmicroscopic examination were unremarkable.

Subsequent outbreaks ofvesicular diseaseOne month after the initial outbreak, lesionsin sows and growing pigs were resolved atSites 1 and 2. A few growing pigs hadsloughed a hoof. However, approximately

Figure 3: Putative ruptured vesicle in the nostril of a gestating sow in a farrow-to-finish herd in which approximately 5% of sows at one site had similarlesions.

Figure 4: Recently ruptured vesicle on the snout of a gestating sow.

samples and blood samples were submittedto FADDL at Plum Island Animal DiseaseCenter and to Purdue University AnimalDisease Diagnostic Laboratory (PUADDL).All samples remained negative for exoticvesicular diseases. One of the ten pigsseroconverted to parvovirus. Bacteriological

results were unremarkable. Enterovirus wasisolated at FADDL from skin, oral mucosa,spleen, and lymph node. Enterovirus wasisolated from brain at PUADDL and sub-mitted to FADDL, where PCR was used toidentify the isolate as porcine enterovirusgroup 1, including serotypes 1 through 7

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150 four- to 11-day-old piglets were lethar-gic and lame and had coronary band lesions.Piglets of this age group continued to beaffected for approximately another month,commonly in small numbers (eg, 10 to 15pigs), but infrequently in larger numbers(eg, 150 pigs). Affected piglets were fromsows of all parities, and were housed ondifferent types of flooring (plastic or roundbar). Rectal temperatures of affected pigletsranged from 39.8˚C to 41.2˚C, suggestingan infectious etiology. Lesions resolved by16 days of age. Each time affected groupsof piglets were observed, fresh and fixedtissues and blood were collected and sub-mitted first to FADDL then to PUADDLto repeat the previously listed tests, butresults remained unremarkable. Enterovirushas not been isolated from piglet samples.Pigs at Site 3 were never affected.

The herd was quarantined voluntarily or bythe state veterinarian intermittently forapproximately 7 months. The problem re-solved and all quarantines have been lifted.Animals introduced to the farm have notbecome clinically affected. A definitive di-agnosis was never made. As no records forperformance of affected pigs were kept, thecost of the outbreak could not becalculated.

DiscussionThe cause of the vesicular lesions in thisoutbreak remains unknown. New stock

had not been introduced to the herd forover 1 year. There was no history of inter-national travel by caretakers. Exotic vesiculardiseases were ruled out by FADDL. Com-monalities among infected pigs were notapparent. Growing pigs appeared to exhibitlesions after transport from Site 3; however,affected sows had not been transported.The stress of transport in the growing pigsmight have predisposed the pigs to infection.Pigs on Sites 1 and 2 had separate caretakers.Feed mixing errors that might have causeddietary imbalances were ruled out becausesows and growing pigs were fed differentdiets. Moreover, affected neonatal pigs werenursing sows or eating a commercial creepfeed. A common corn source was used toprepare sow and pig rations. Feed samplesfrom affected pens were negative for T-2toxin. Although T-2 toxin is rare in NorthAmerica, it has been reported to cause oraland dermal irritation in growing pigs.2

Other less common causes of vesicular dis-ease, such as consumption of celery orparsnips, or exposure to sea lions infectedwith calicivirus, were ruled out due to lackof exposure.3

Parvovirus has been associated with idio-pathic vesicular lesions and erosions in 1-to 4-week-old pigs.4,5 Parvovirus was notisolated from the pigs in the current caseand only one of ten affected pigs testedseroconverted to parvovirus during theoutbreak.

Porcine enterovirus group 1 was isolatedfrom affected growing pigs, but not fromsows or piglets described in this report.Swine vesicular disease virus, in the En-terovirus genus, causes vesicular lesions inswine; however, the pigs on this farm didnot seroconvert to SVD virus, nor wasSVD virus isolated from these pigs. Tentativedata exists suggesting that porcine enterovi-rus group 3 might be associated with ve-sicular disease.6 In 1979, vesicular diseasewas reported in ten finishing pigs in aFlorida herd. Exotic viruses were not isolated.Porcine enterovirus types 3 and 8 were iso-lated from nasal and rectal swabs of affectedand unaffected pigs in the same group.However, porcine enterovirus was not con-sidered the causal agent and the etiologyremains unknown.7

Porcine enteroviruses are ubiquitous inconventional swine herds,7,8 and have beenisolated from the tonsils of clinically healthypigs at slaughter,9 manure of healthy pigs,10

and slurry from a pig farm.11 Porcine en-terovirus was likely an incidental finding inthis case, caused by contamination of tissuessamples with manure (containing enterovi-rus) during collection in the swine barn.However, future animal inoculation studieswith the isolate from this herd are plannedas the initial step to attempt either to repli-cate the clinical syndrome or to definitivelyrule out the isolate as the etiologic agent.

Veterinarians are trained in the recognitionof exotic diseases and subsequent reportingprocedures. However, we do not expect toobserve such diseases on routine herd visitsin the United States. Thus, despite ourtraining, we are not mentally prepared eitherto observe large numbers of swine withvesicular lesions, nor to deal with the emo-tions of herd owners and personnel, as wellas our own, in the face of a potential foreignanimal disease outbreak. Nevertheless, theimportance of correctly handling such anoutbreak cannot be overstated, due to thedevastating implications of an exotic diseasefor agriculture and the economy of theUnited States.

Practitioners are encouraged to be vigilantobservers and reporters of clinical signsconsistent with exotic diseases. Veterinariansshould periodically review classic clinicalsigns and aberrant presentations of exoticdiseases as part of their ongoing continuingeducation. Moreover, emerging diseasesshould be considered among the differential

Figure 5: Subacute lesion on the snout of a gestating sow.

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diagnoses when unusual clinical signspresent. Practically, veterinarians shouldmaintain in their vehicles and wallets a listof emergency phone numbers, includingthose of their state veterinarian and nearbyFADDs, for immediate accessibility(memorized phone numbers may be for-gotten during emergency situations). Veteri-narians should also have a practice protocolin place for cases in which the veterinarianand practice vehicle must be decontami-nated or quarantined for a period of time.Finally, veterinarians should work withtheir clients to establish farm and person-nel procedures for instances of short- andlong-term quarantine or mandatory de-population for disease eradication.

Implications• Practitioners are encouraged to be

vigilant observers and reporters ofclinical signs consistent with exoticdiseases.

• Differential diagnoses for vesiculardisease includes foot-and-mouthdisease, vesicular stomatitis, swinevesicular disease, vesicular exanthemaof swine, calicivirus, parvovirus,mycotoxicosis, idiopathic vesiculardisease, chemical burn, contactirritation, and consumption of celeryor parsnips.

• Definitive determination of the causeof vesicular disease might be prolonged,but exotic diseases are usually ruledout within 48 hours by FADDL.

• Veterinarians should maintain in theirvehicles and wallets a list of emergencyphone numbers, including those oftheir state veterinarian and nearbyFADDs, for immediate accessibility.

• Veterinarians should have a practiceprotocol in place for cases in whichthe veterinarian and practice vehiclemust be decontaminated or quaran-tined for a period of time.

• Producers should establish farm andpersonnel procedures for instances ofshort- and long-term quarantine ormandatory depopulation for diseaseeradication.

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2. Osweiler GD. Mycotoxins. In: Straw BE,D’Allaire S, Mengeling WL, Taylor DJ, eds. Diseasesof Swine. Ames, Iowa: Iowa State University Press;1999:731–742.

3. Montgomery JF, Oliver RE, Poole WSH. Avesiculo-bullous disease in pigs resembling foot andmouth disease 1. Field cases. NZ Vet J. 1986;35:21–26.

4. Lager KM, Mengeling WL. Porcine parvovirusassociated with cutaneous lesions in piglets. J VetDiagn Invest. 1994;6:357–359.

5. Kresse JI, Taylor WD, Stewart WW, Eernisse KA.Parvovirus infection in pigs with necrotic andvesicle-like lesions. Vet Microbiol. 1985;10:525–531.

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7. Gibbs EPJ, Stoddard HL, Yedloutchnig RJ, LeggeM. A vesicular disease of pigs in Florida of unknownetiology. Florida Vet J. 1983;12:25–27.

8. Derbyshire JB. Enterovirus. In: Straw BE,D’Allaire S, Mengeling WL, Taylor DJ, eds. Diseasesof Swine. Ames,Iowa: Iowa State University Press;1999:145–150.

9. Betts AO. Studies on enteroviruses of the pig–I.The recovery in tissue culture of two related strainsof a swine polioencephalomyelitis virus from thetonsils of ‘normal’ pigs. Res Vet Sci. 1960;1:57–64.

10. Forman AJ, Pass DA, Connaughton ID. Thecharacterization and pathogenicity of porcine en-teroviruses isolated in Victoria. Aust Vet J.1982;58:136–142.

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