Yersinia pseudotuberculosis infection: study of an epizootic in squirrel monkeys

0095-1137/81/030519-07$02.00/0

Yersinia

pseudotuberculosis

Infection:

Study of

an

Epizootic

in Squirrel Monkeys

W. C. BUHLES, JR.," 2t J. E. VANDERLIP,1* S. W. RUSSELL,'t AND N. L. ALEXANDER'

Office ofAnimal Resources' andDepartment of Pathology,2 School of Medicine, University ofCaliforniaat

San

Diego,

LaJolla,

California

92093

Anepizootic ofanacutely fatal enteric diseaseinacolonyof squirrel monkeys

(Saimiri sciureus) was attributedto infectionby Yersiniapseudotuberculosis

serotypeIII.Ofatotaladultpopulation of 96 animalsatrisk, thereweresixfatal

casesofyersiniosis. Serological evaluation of the colony just after the outbreak

endedrevealed that 22 of 60 monkeys tested (37%) had significant antibodytoY.

pseudotuberculosis (microagglutination titer of 21:80) but didnothave clinical

disease. Theoutstandingpathological lesions noted in dying monkeyswereacute,

purulent, necrotic and focal enteritisprimarilyaffecting the jejunum and ileum

andfocalhepatic necrosis and abscessation. Y.pseudotuberculosis wasisolated

fromtheorgansoftwoofthe dying monkeys. Using cold enrichmenttechniques,

Yersinia was also isolated from the feces oftwo apparently healthy monkeys

(both seropositive), from the spleen ofamonkey dying of othercauses,and from

the coloncontentsofastillbornsquirrel monkey baby.All isolates had thesame

biotype and serotype. Anepisode of abortions wasassociated both temporally

andspatially with the fatal casesofyersiniosis, and Y.pseudotuberculosis was

cultured from the uterusoftwoof thedying monkeys, suggesting thatyersinia

infectionmay be associated with abortion, as well as with enteric infection, in

theseanimals.

Yersinia

pseudotuberculosis

is one member ofagenerictriadofpathogenicbacteria within the family Enterobacteriaceae, which also in-cludesYersinia enterocoliticaand Yersiniapes-tis.Infection withY.pseudotuberculosisis zoon-otic, as the disease affects wild and domestic animals, nonhuman

primates,

and humans

(16,

22).Infact, infectionhasbeen describedinmore than75

species

ofbirds andmammals

(8,

9,

14).

The

geographical

distribution ofthe organism includes northern

Asia, Europe,

North and South

America,

andAfrica.

Many

infected ani-mals

develop

abdominaldisease whichincludes

enteritis, typhlitis,

mesenteric

lymphadenitis,

and abscessation ofliver and

spleen. However,

birds, rats,

mice,

and other small rodents may

become infected and not

develop

disease, but

instead become chronic carriers of Y.

pseudo-tuberculosis

withfecal

shedding

of the

organism.

These animalsarebelievedtoserve asthe

pri-maryreservoir of infection

(14, 16).

Outbreaks of disease dueto Y.

pseudotuber-culosisin

captive

nonhuman

primates

havebeen reportedinboth the United StatesandEurope

(5, 16). Two separate epizootics ofyersiniosis,

tPresentaddress: SyntexResearch, Mountain View, CA 94043.

tPresentaddress:DepartmentofPathology, Universityof NorthCarolina,Chapel Hill, NC27514.

both due to Y. enterocolitica, have also been

reported in colonies of nonhuman primates in the United States, withlesions similaror

iden-tical to

those

caused by Y.

pseudotuberculosis

(1, 15). These outbreaks involved considerable

mortality and in several cases affected a large number of monkeys.

In the spring of 1977, an outbreak of

yersi-niosis occurred in a colony of squirrel monkeys

(Saimiri

sciureus) housed atthe

University

of Californiaat San Diego. This report describes the epidemiological investigation of that out-break, which allowed sequential study of both theserological and bacteriologicalstatusofthe affectedanimals.

MATERLALS

AND METHODS

Description of the colony. In December 1975, the

School of Medicine, University of Californiaat San

Diego, established a colony of squirrel monkeys at its

Elliott field stationfacilitylocated on 30 acres of brush

land15milesnortheast of downtown San Diego. The

colony was initiatedwith39adult males and 68adult

females.Approximately 18of themonkeys(six males

andtwelvefemales)wereof the Romantype (Iquitos,

Peru) and wereoriginally obtainedfromPrimate

Im-ports, Inc. (Port Washington, N.Y.). The remainder

were of theGuyanesetype (Georgetown, Guyana) and

were obtained from South American Primates, Inc.

(Miami, Fla.). All adult monkeyshad beentrappedas

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adults in the wild. Theanimals were housed since the inception of the colony in sixrectangularwire cages (6by 20by8ftinheight [ca. 1.83by6.10by2.44m])

with concrete slab floors. Each cage had

approxi-mately 40% of its total area out ofdoors, and the

remaining 60% was inside of a large building with

permanent openventilationtothe outside.Cageswere

adjacenttooneanother withno morethan 18 in.(ca.

46 cm) between them andwerenumberedonethrough

six from east to west. All monkeys received Purina

high proteinmonkeychowandwateradlibitum,fresh

fruit twice weekly, and a fruit drink supplemented

with vitaminsdaily.

Tissue,collection andprocessing. Animalswere

necropsied, and tissues were fixed in 10% buffered

Formalin.Tissues were embedded inparaffin byusmg

standard techniques, sectioned at 4 to 6 ,um, and

stainedwithhemotoxylinand eosin and in some cases

withGiemsaorBrown-Brennstain.

Microbiology. Initially, specimens collectedat

ne-cropsy werecultured on bloodagar plates,on

Mac-Conkeyagar, and inthioglycolate broth. Toidentify

organismsweutilized standard tubed media andthe

API 20E identification system (Analytab Products,

Plainview, N.Y.). Cold enrichment for Y.

pseudotu-berculosis (6, 7, 18) employed Mg2+- and Ca2+-free

phosphate-buffered saline (PBS) (GIBCO

Laborato-ries, Grand Island, N.Y.).Pieces of tissue and rectal

swabsor cecum contentsobtainedwithsterilecotton

swabs wereplacedinto2to 5ml ofPBSandheldat

4°C.Atapproximately 14and28days,asterile swab

was introduced into the PBS and plated onto

Mac-Conkeyagar, which wasincubated at37°C for48h.

Pinpoint, translucent colonieswithYersinia

morphol-ogy were tested fortheoxidase reaction and for urease

production, andoxidase-negative, urease-positive

or-ganismswereidentifiedbyusingthe API 20ESystem.

Isolatesweresent totheMicrobial Diseases

Labora-tory, California State Department of Public Health,

Berkeley, forconfirmation ofidentity, determination

ofbiochemical reactions by using techniques

previ-ously described (3), and serotyping bytube

aggluti-nation(12).

Serology.Serum antibodiesto Y.

pseudotubercu-losisweredetermined byusingamicroagglutination

test. One ofthe original isolates from the monkey

colony wasmaintained on blood agar plates

subcul-turedevery1 to2months andheldat room

tempera-ture.Theorganismwasgrownonbloodagarfor48h at 20or37°C,andaliveantigen suspensionwasmade inPBS whichwasadjustedtoaconstantcelldensity of 80% transmissionat640nm,usingaColeman Junior

spectrophotometer. Serumwhich had been stored at

-20°Cwasthawed and diluted to 1:5 withPBS,and

serial twofold dilutionsweremadeto 1:1,280 in PBS.

Onedrop (0.025ml)ofserumdilutionwasmixed with

onedropofantigen suspension on aglass microscope

slide and mixed withawoodenapplicatorstick. The mixture was incubated at room temperature for 30 min;aglasscoverslip(18 by18mm) wasplacedover the mixture to reduce drying, and the mixture was incubated foranadditional 30min. Slideswere read atX100andX400, andmicroagglutinationwasscored as1+to 4+.The titerwasthehighestdilutiongiving

1+ agglutination. This degree ofagglutination was

compared with the reaction of negative and positive

controls run simultaneouslywith each test. Control

seraconsistedof a known positive rabbit antiserum to

our isolate of Y. pseudotuberculosis, serum from a

healthy squirrel monkey with a titer of 1:320, and

serum from a squirrel monkey with a titer of <1:10. Rabbit antiserum to Y.pseudotuberculosis was

pre-pared by injectinganadultNewZealand rabbit

intra-venously with 0.5 ml of aFormalin-inactivated

prep-arationof the organism. Injections were made on days 0, 3, 5, 7, 9, and 12, and on day 19 the rabbit was exsanguinated under pentobarbitalanesthesia, and the serumwas stored at -20°C. This serum had a

microag-glutinationtiterof 1:1,280.

Trapping and examination of wild mice.

Be-tweenSeptember1977and June 1978 (5 to 14 months after the start of the epizootic), we trapped and ex-amined 83 wild mice near themonkey colony. A total

of56Musmusculus and 27 Peromyscusmaniculatus

weretrapped live, inside or within 50 m of the colony.

Themice wereeuthanized,andthe spleen and cecum contentswerecultured by cold enrichment. Blood was

collectedfrom some mice for serologicalevaluation.

RESULTS

Clinical findings.A diagnosisofyersiniosis

wasmadepostmorteminsixadult squirrel

mon-keys. The diagnosis was made on the basis of

pathological lesions (monkeys 612, 58, and 33),

pathological lesions and culture of Y.

pseudotu-berculosis (monkeys47and 53), and

pathologi-cal lesions and ahigh serum antibody titer (1:

1,280;monkey 24).Clinical signs associated with

disease are shown inTable 1. The duration of

illness varied from2to 7days,but inmost cases

lasted only 2 to 3 days. Three of the five female

monkeys were pregnant at the time ofdeathor

had evidence of a recently terminated

preg-nancy, and one of these females died during

dystocia. Several ofthe monkeys were treated

withfluids and antibiotics. Threeof the six were

euthanized whileseverely ill.

Pathological findings. Distribution of

le-sions is shown in Table 1. The outstanding

le-sions inall sixmonkeys wereintestinal,

charac-terizedgrosslyasraised,reddened, elliptical

nod-ules, orraised, annular, tan nodules on the

se-rosal,antimesentericsurfaceof thejejunumand

ileum.On the mucosalsurface, there were

ellip-ticalfoci characterizedbyared-brownperimeter

and agreycenter. In onemonkeythe cecum was

involved, with a red-black discoloration and a

thickenedwall.Microscopically, therewas acute

tochronic-active, multiple,focal,ulcerative

en-teritis. Lesions often eroded into and through

the submucosa, and several were transmural.

Lesions were often associated with a Peyer's

patch. One monkey had acute, hemorrhagic,

chronic-activetyphlitis with ulceration.In some

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Y. PSEUDOTUBERCULOSIS INFECTION 521

TABLE 1. Summary of clinical and pathological findingsinsquirrel

monkeys

dying of Y.

pseudotuberculosis infection

Histologicallesions Monkeyno.a Cageno. Clinicalsigns Small

intes-tine Liver Spleen Uterus

612(M) 1 Unknown(euthanized) + + +

58 (F) 6 Dystocia, found dead + - -

-47 (F) 6 Pregnant, comatose + - - +c

33 (F) 5 Weakness, depression, diarrhea + + - NEd

53 (F) 6 Vaginal hemorrhage, weakness, abortion? + +c - +c

24(F) 4 Depression,dehydration, diarrhea + + - NE

a Sex of monkey is given within

parentheses.

b Significant microscopic lesions noted to be present (+) or absent (-).

cIndicates that Y.

pseudotuberculosis

was cultured fromthis organ.

dNE, Not examined

microscopically.

monkeys,mesentericlymphnodes weregrossly

reddened and microscopicallyshowedhypermia and reactivehyperplasiabutnolymphadenitis.

Liverlesions,whenmacroscopic, consistedof

multiple,punctate, 0.5-to2-mm-diameterfoci of white-grey discoloration. Microscopically, liver lesions variedfrom small foci of acute hepatic necrosis to larger microabscesses. Rod-shaped bacteriawereseeninsomeliver lesions andwere gramnegative.

Splenitisin onemonkeywascharacterizedby fociof abscessation. Uterine lesions were char-acterized by acute, erosive endometritis, with

areasof focalnecrosis, hemorrhage,andvariable

myometritis.

Microbiological findings.

Y.

pseudotuber-culosiswasrecoveredfrom

monkeys

47and53, using routine

microbiological techniques (Table

1).Monkeys612, 33,and58 were notcultured at

necropsy. Cultures from monkey 24 yielded

Klebsiella

pneumoniae,

Enterobacter cloacae, anda

Streptobacillus

from the

liver,

mesenteric lymph nodes, and

spleen,

but no Yersiniawas isolatedevenby cold enrichment ofanumberof tissues.Inadditionto

Yersinia,

Escherichiacoli

wasisolatedfrom thekidney, mesenteric nodes,

intestines,liver, and peritoneum, andagroup D

streptococcal

organism was isolated from the

uterus,

intestines,

and liver ofmonkey47.

Y.pseudotuberculosis isolates were initially identified in our laboratory as gram-negative

rods which were oxidase negative, growing as

pinpoint-size to 1-mm translucent colonies on MacConkey agar. They were urease-,

o-nitro-phenyl-/-D-galactopyranoside-,

nitrate-, and es-culin-positiveandfermentedglucose, mannitol,

rhamnose, and arabinose. Isolateswere sentto

the Microbial Diseases Laboratory and

con-firmed to beY.

pseudotuberculosis,

with

bio-chemical reactions aslisted in Table2. All

iso-lates had thesamebiotype,all were serotypeIII,

and none of theisolates fermented melibiose (an

unusual characteristic for Y. pseudotubercu-losis).

Epizootiology of the outbreak. The tem-poral characteristics of the Y. pseudotubercu-losisepizooticin thecolonyareshown inFig.1. Between December 1975 when the colony was

started and March 1977, there had been three

deaths in adult monkeys (monthly death rate,

2.1 per 1,000). From April to July 1977, there

were eight adult deaths, six due to Y.

pseudo-tuberculosis (monthlydeath rate, 22 per 1,000). Coincidingwith the adult deaths was anunusual

occurrence ofabortions(seven in 1 month).

Be-tweenJuly 1977andJuly1978,theadult death

ratewas 4.9 per1,000 per month,and the

breed-ing season of 1978 was not characterized by a

highincidence ofabortions(three in 1978 versus

eightin1977).

Thespatialcharacteristics oftheepizooticare

shown in Table 3. The adult deaths attributed

to Yersinia, aswell asthe abortions and infant

deathsfor the period from April to December

1977, were clustered at the west end of the

facility,and thehighest incidenceofdeaths due

toall causesoccurredincage 6. In cage 6during

the 1977breedingseason,eightof the nine

preg-nanciesendedinabortionorinfantdeaths.

InAugust 1977, weinitiatedasurveyofcages

1, 4, 5,and6 todeterminetheserologicalstatus

of squirrel monkeys to Y.

pseudotuberculosis

and to detectlatent carriers of theorganism by

fecal culture.BetweenAugust and October1977,

4 to 6 months after the start of the epizootic,

monkeysinthesecages were bled for serum, and

a fecal culture for Y.

pseudotuberculosis

was

performed by

using

cold enrichment (Table 3).

Of the monkeys sampled, 37% (22 of 60) had

serumantibody titers 21:80, with titers ranging

to1:1,280. Geometric mean titers were similarin

ail

four cages. Only 2 of 59 monkeys (3%)

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TABLE 2. Biochemicalcharacteristics of Y. pseudotuberculosis isolates

Test Resulta Test Resulta

Oxidase 0 Glucose A

Catalase + Lactose

Motility +(25°C) Maltose A

Gelatin 0 Sucrose

Citrate 0 Mannitol A

Urease + Raffinose

Indole 0 Adonitol

Nitrate + Xylose A

Voges-Proskauer 0 Dulcitol

Malonate 0 Inositol

Triplesugariron Alkaline/acid/- Sorbitol

Esculin + Salicin A

Sodiumacetate vb Trehalose A

Phenolpyruvate 0 Cellibiose

BO-galactosidase + Rhamnose A

Lysinedecarboxylase 0 Melibiose

Argininedihydrolase 0 Arabinose A

Ornithinedecarboxylase 0

a(+)Positivereaction; (0)negative reaction; (A) fermentation; (-)nofermentation.

Ail

incubationwasdone

at35°C unless otherwise noted.

bVariable reaction noted.

AAAA

ASORTIONS A AAA A A AA

ST1LLRTHS s s* s s

INFANT OEATS I N I I /l

96n nn

1978

J F M A M J J AS O N O J F M A M J J A S O N D J F M A M J J

1976 1977 1978

FIG. 1. Temporaldistributionof adult and infant

deaths andreproductive failuresin thesquirrel

mon-keycolonyduringaY.pseudotuberculosisoutbreak.

Eachrectanglerepresents oneadult death; shaded

rectangles aredeaths attributedto Y.

pseudotuber-culosis; andopenrectanglesaredeathsduetoother

causes.Symbols:(A) abortion; (S)stillbirth;(I) infant

death; (*) Y.pseudotuberculosis was isolatedfrom

monkeyatnecropsy.

tured for fecal shedding of Y.

pseudotubercu-losis were found to be positive. Both of these

monkeys(36and43)hadserumantibodytiters

of1:160andwereclinically healthy. When

sam-pled45days later,bothmonkeyswerestill

clin-ically healthy, and Y. pseudotuberculosis was

notrecoveredby fecal cultureatthistime.

Se-rum antibody titers in both monkeys declined

thereafter.

InDecemberandJanuaryandagaininApril

1978, 1 yearafter the start of the epizootic, all

seropositive monkeysincages4, 5, and 6again

weresampled.Nonewerefoundtobeshedding

Yersinia.Changesinserumantibody titers with

time are shown in Fig. 2. Of the 17 monkeys

followed sequentially, 10 showed a twofold or

lesschange in titer between August and

Septem-ber1977andApril 1978, and 7 showed a greater

than twofold decline in titer. Geometric mean

antibody titersfor the 17 monkeys were 1:181 in the period from August to September, 1:83 in theperiodfrom December to January,and 1:77 inApril.

Between August and October 1977, Y. pseu-dotuberculosis was cultured two more times

from monkeys in the colony. Astillbornmonkey

delivered in August was found to have a pure culture of Y.

pseudotuberculosis

in the colon butnolesionsassociated with thisinfection. In October, a male monkey from cage 1 died of pneumonia, pleuritis,and alungabscessdue to Streptococcus pneumoniae. Y. pseudotubercu-losiswasisolatedfrom thespleen of this monkey by cold enrichment, but againno lesions were

associated with this infection, andno antibody

was detected by microagglutination. Ail mon-keys, including neonates, infants, and some

aborted fetuses, which diedbetween July 1977

andJanuary1979werecultured for Yersiniaby usingcold enrichment. Other than the instances

described above, no Yersinia was isolated.

There have been no additional deaths with

le-sionsresembling those caused by Y.

pseudotu-berculosis.

Findings in wildmice. Ofthe 83wild mice

trapped in or near the monkey colony, 3 were

foundtobeinfected with Y.pseudotuberculosis.

Yersinia was isolated from the cecumcontents

butnotthespleens of the three mice.

Ail

three

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TABLE 3. Mortality, serological, and culture data (from April to December 1977) by cage for the squirrel

monkey colony during aY.pseudotuberculosis outbreak

Total No. ofdeaths by: No.of No. of No.of in- No.sero- Geomet- Fecal

Cageno. adultsat

No.tof

No fant positive ric mean Fecal

risk Yersiniosis Other abortion stillbirths deaths (%)a titerb shedding

1 (East) 22 1 1 NAd NA NA 4/19(21) 190 0/16

2 il 0 0 0 0 0 NEe NE NE

3 15 0 1 1 1 0 NE NE 0/3

4 16 1 0 0 0 0 4/16 (25) 190 0/15

5 16 1 1 1 1 0 9/14(64) 201 2/14

6(West) 16 3 1 6 0 2 5/11 (45) 183 0/11

aNumber

seropositive

per numbertested(sampled

from

AugusttoOctober1977).

bReciprocal geometricmeantiterof

seropositive

monkeys.

cNumber of monkeysshedding Y.

pseudotuberculosis

inthe

feces

per numbercultured.

dNA, Notapplicable

since

cage1containedall male

animals.

eNE, Notexamined.

CE 1280

F->C 640

o

m

320

z

,X 160

o

CL 80

a: <80

TIME PERIOD (Months After Start

ofOutbreak)

FIG. 2. Reciprocal antibodytiterstoY.

pseudotu-berculosisasdeterminedbymicroagglutination in17

squirrel monkeys sampledat5,9,and12 monthsafter

thestartoftheoutbreak. Each circlerepresentsthe

tierofasingle animal. Titersoflessthan80were

notconsideredsignificant.

mice were Mus musculus and were trapped

within the first 2 months ofthesurvey

(Septem-ber and Octo(Septem-ber1977). The biotype andserotype

ofall three isolateswereidenticalto those

iso-lates recovered frominfectedmonkeys.The only

lesion notedat necropsy ofthese infected wild

micewasenlargement of the mesentericlymph

nodes. These threemice and14culture-negative

mice trapped during the same period had no

detectable antibody to Y. pseudotuberculosis

(titer <1:40).

DISCUSSION

Infections causedby Y. pseudotuberculosisor

Y. enterocolitica in nonhuman primates have

beenreportedassporadic, isolatedcasesaswell

asfull-blown epizootics. Poelmaetal. (19) have

reviewed and described some of the isolated

cases reported in the literature occurring

pri-marily in Europe, and there have been three

case reports of multiple animal involvement

from regional primate centers in the United

States(1, 5, 15). Theclinical disease and

patho-logical lesions in monkeysaresimilar for both of

these Yersinia species. Poelma et al. (19)

re-ported on 10 fatal cases of Y. enterocolitica

infection in nine species of monkeys, the primary pathological findings being abscesses in liver and spleen, ulceration and necrosis of the jejunum,

ileum, andcolon, and hyperplasia of mesenteric

lymph nodes. McClureetal. (15) reported three

casesof Y. enterocolitica intwovervetmonkeys

(Cercopithecus aethiops) and one mangabey

(Cercocebus torquatus), with lesions including

smalltolargecaseousabscessesof the liver and

multiple, focal areas of enteritis with necrosis

and ulceration, involving in one case Peyer's

patches of the ileum. Baggsetal. (1) reported

fatal Y. enterocolitica infection in 29 owl

mon-keys (Aotus trivirgatus).Animals had purulent

andnecrotizing enteritis, hepatitis, andsplenitis.

These authorssucceeded in reproducing the

dis-ease experimentally in owl monkeys by oralor

intravenous inoculation. Bronson etal. (5)

re-portedanepizootic of Y.pseudotuberculosis in

29monkeys of four different species. The

char-acteristic lesionswereagain multiple, focal

hep-atitiswithnecrosis, multiple, focalsplenitis,and

areasofmucosal necrosis with inflammation in

the intestine, often underlying lymphoid

folli-cles. Lesions described in these four previous

reportsaresimilaroridenticaltothose observed

byus. Of the fiveoutbreaks, the organism was

identifiedserologicallytospecies levelinthree,

and in the other two instances, the organisms

appeared to have definitive biochemical

char-acteristics. Thus, yersiniosis in nonhuman

pri-mates, whether caused by Y. enterocolitica or

Y. pseudotuberculosis, appears to be a single

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524

pathologicaldiseaseentityaffectinganumberof

primate species and which can result in

signifi-cantmortality.

Ourfinding ofacommonbiotypeand serotype

among isolates from the dying monkeys, fecal

carriers, thelatently infected monkeys,and the

wild mice suggests that there was a common

source of contamination. The fact that these

isolates did not ferment melibiose (an

unu-sual characteristic for Y. pseudotuberculosis)

strengthens this suggestion. We commonly ob-served ferai mice and ground squirrels running within or near the squirrel monkey cages and occasionally found evidence that the monkeys

sometimescaught and ate wild mice within their

cages.Also, monkeyscommonlyatebiscuitsthat

had fallentothe cage floor and become moist-ened.Wepostulate that the epizootic began by contamination offoodby feces of ferai miceor by the eating of an infected mouse and then spread through the colony by fecal-oral trans-mission (14, 16). Since disease, as well as the number ofseroconversions,appearedtobe con-centratedatoneend of the

colony

(cages4to6), the original episode of infection may have oc-curred there, although the

finding

of the first adult case in the opposite end of the colony

suggeststhat theremay have been several

point-sourcesof infection.

Other investigators have

suggested,

or pre-sented evidence, that Yersinia outbreaks may be associated withferai rodents. Mair (14) re-ported that after an outbreak of Y. pseudotu-berculosis in birds at the Bristol

Zoo,

6 of 14 micetrappednearthe bird housewerefoundto becarryingtheorganism. Duringanoutbreak of Y.

pseudotuberculosis

atthe National

Zoologi-calParkin

Washington, D.C.,

Baskin etal.

(2)

isolated theorganism from wildratsandpigeons

trapped

inthe

vicinity

oftheaffected

zoological

species.

Kapperud

(10)

reported

that 10% of small wild rodents

trapped

in Denmark were carriers ofY.enterocolitica and isolated Y.pseu-dotuberculosis from small rodentsas

well,

sug-gestingasignificant

potential

reservoir of

yersi-nia infection in this population. As laboratory

mice have been shownto excreteY.

enterocolit-icain the feces for upto 135daysafter

experi-mental infection withoutshowing signsof illness

(20), it is not difficult to accept theprobablerole

ofwildmice in outbreaks ofyersiniosis in

ani-mals.

The fmdings of thisstudy, as well as those of

others on yersinia outbreaks, suggest that Y.

pseudotuberculosis

and Y. enterocolitica both

canbe consideredprimarilyasentericpathogens

innonhumanprimates.Certainlyinthesquirrel

monkeycasesdescribed here, enteritiswasthe

outstanding and most severe lesion, severe

enough to havecaused the death of the animal.

Obwolo (17) foundthat in guinea pigs

experi-mentally infected with Y.pseudotuberculosis by

the oral route thatanimalsdyingwithin thefirst

10 days hadpredominantly gastrointestinal

le-sions, primarily multiple foci of necrosis in the ileum and cecum. Guinea pigs which died

be-tween 10and 20 dayshad fewer but larger

intes-tinal lesions and more visceral involvement, with abscesses in the liver and spleen. The early intestinal lesions seen in the experimentally in-fectedguinea pigs werehistologically similarto

those found innaturally infected monkeys.This

suggeststhatmostmonkeys infected with

Yer-sinia probably died acutely and thuspresented primarilyintestinallesions rather than the large,

sometimescaseous, visceral abscesses often

as-sociated with pseudotuberculosis.

Our serologicaldatastronglysuggest that

dur-ing the epizootic described herein the colony

attack rate exceeded 40%. Monkeys were

ob-served carefully several times daily by

experi-enced workersduring the period of the epizootic,

andclinical illness (with the exception of abor-tion) was limited to those animals which

ulti-mately died, suggesting that primatesmay

be-comeinfected withYersinia without developing

disease. Ourfindingof onlytwofecal carriers of theorganismamongmorethan20monkeyswith significant titers also suggests that some squirrel

monkeys may serve ashealthycarriers and shed

Y.

pseudotuberculosis,

albeit for an unknown duration, and that mostmonkeysovercome or donotdeveloptheintestinal carrierstatewhile remaining seropositive. It is also possible that the number oforganisms shed from some car-riers may be so low as to preclude detection. Further,serumantibodyresponses inthecolony

suggest that whereas in some monkeys titers

dropbelow significantlevels fairly rapidly, some

animals maintain titers foratleast 1yearafter infection. It has been previously assumed that antibody levels to Y.

pseudotuberculosis,

at leastinhumans,areshortlived(4).

The association of Y.pseudotuberculosis

in-fection with abortion is based on the following

observations made by us in squirrel monkeys:

(i) the occurrence ofabortions coincided both

temporally and spatially with disease due to

Yersinia,

(ii)

Y.

pseudotuberculosis

wasisolated

from the uterus of two of themonkeys,(iii)there

wasendometritisassociatedwiththisinfection,

and (iv) Yersinia was isolated in pure culture

from thecolon contents of a stillborn squirrel

monkey, indicating possible infection of the

am-nioticfluid. Bronson et al. (5) isolated Y.

pseu-dotuberculosisfrom the amniotic fluid ofa cy-J.

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VOL.13, 1981

nomolgus monkey dying ofyersiniosis, but did

not report any uterine lesions associated with

this infection or the relation to any abortions.

Yersinia has been associated previously with

abortion or fetal infection in bovines (11, 13) and

ovines (21). The importance of Yersinia as a

possibleabortifacient inanimals and humans is unknown, but considering the epidemiology of theorganismand its worldwidedistribution,this

aspect ofyersiniosisdeservesinvestigation.

Cer-tainly, Yersiniamay posea

potential

threatto

colonies established for thecaptive breeding of

nonhumanprimates.

ACKNOWLEDGMENTS

This work was supported in part by a grant from the County of SanDiego.

We aregrateful for the assistance provided by Marjorie Bissett inevaluating Yersiniaisolates,the technical assistance of CariCousino and David Denton,and the advice of Don Hunsaker.

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Pseudotuber-cu10ais (Yersinia enterocolitica) in the owl monkey

(Aotustrivirgatus). Lab. Anim. Sci.26:1079-1083. 2. Baskin,G.B.,R. J.Montali,M.Bush,T. J.Quan,and

E.Smith. 1977.Yersiniosis in captive exotic mammals. J. Am. Vet. Med. Assoc. 171:908-912.

3. Bissett, M. L.1976.Yersinia enterocolitica isolatesfrom humans inCalifornia, 1968-1975.J.Clin. Microbiol.4: 137-144.

4. Bottone, E. J.1977.Yersinia enterocolitica:apanoramic view of a charismaticmicroorganism. Crit. Rev. Micro-biol. 5:211-241.

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11. Langford, E. V. 1969. Pasteurellapseudotuberculosis associated with abortion andpneumonia in the bovine. Can. Vet. J. 10:208-211.

12. Mair, N. S., H. J. Mair, E. M. Stirk,and J. G. Corson. 1960. Three cases of acute mesenteric lymphadenitis due to Pasteurellapseudotuberculosis.J. Clin. Pathol. 13:432-439.

13.Mair, N.S., and J. F. Harbourne. 1963. The isolation of Pasteurellapseudotuberculosis from a bovine fetus. Vet. Rec. 75:559-561.

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1971.Pseudotuberculosis innonhuman primates: infec-tion with organisms of the Yersinia enterocolitica group. Lab. Anim. Sci. 21:376-382.

16. Obwolo, M. J. 1976. A reviewof yersiniosis (Yersinia pseudotuberculosis) infection. Vet. Bull. 46:167-171. 17.Obwolo, M.J. 1977. The pathology ofexperimental

yer-siniosis inguinea pigs. J. Comp. Pathol. 87:213-221. 18.Paterson, J.S., and R. Cook. 1963. A method for the

recovery ofPasteurellapseudotuberculosis from faeces. J.Pathol. Bacteriol. 85:241-242.

19. Poelma, F.G., G. H. A. Borst, and P. Zwart. 1977. Yersinia enterocolitica infections in non-human pri-mates. ActaZool. Pathol. Antverp.69:3-9.

20. Ricciardi, I. D., A.D.Pearson, W. G.Suckling, and G. Klein.1978. Long-term fecal excretion and resist-anceinducedin miceinfectedwithYersinia enteroco-litica. Infect. Immun. 21:342-344.

21. Watson, W. A., andD.Hunter.1960.Theisolation of Pasteurellapseudotuberculosisfrom an ovine fetus. Vet. Rec.72:770-772.

22. Wetzler, T. E., andW. T.Hubbert.1968.Pasteurella pseudotuberculosisinNorth America.Symp.Ser.

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