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The response of turkey poults toexperimental infection with strainsof M. gallisepticum of differentvirulence and with M. gallinarumJudith Varley a & F.T.W. Jordan aa Sub‐Department of Avian Medicine , University ofLiverpool Veterinary Field Station , Neston, Wirral, L647TE, EnglandPublished online: 12 Nov 2007.

To cite this article: Judith Varley & F.T.W. Jordan (1978) The response of turkey poults toexperimental infection with strains of M. gallisepticum of different virulence and with M.gallinarum , Avian Pathology, 7:3, 383-395, DOI: 10.1080/03079457808418292

To link to this article: http://dx.doi.org/10.1080/03079457808418292

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Avian Pathology, 7: 383-395, 1978

THE RESPONSE OF TURKEY POULTS TO EXPERIMENTALINFECTION WITH STRAINS OF M. GALLISEPTICUM OFDIFFERENT VIRULENCE AND WITH M. GALLINARUM

JUDITH VARLEY and F.T.W. JORDAN

Sub-Department of Avian Medicine, University of LiverpoolVeterinary Field Station, Neston, Wirral, L64 7TE, England

SUMMARY

In turkey poults aged up to 28 days, a virulent S6 strain of Af. gallisepticumwas recovered more frequently from more tissues for a longer time thanwere other strains. The virulent strain caused nervous signs and gross brainlesions in poults, and was often isolated from the brain, suggesting itsneurotropism. All M. Gallisepticum strains were isolated from the synovialfluid of hocks, but swollen hocks and foot pads were seen only in poultsinfected with the A514 strain. It would seem, therefore, that although pro-clivity for joints was shown by all strains, only A514 produced grosslypathogenic effects in these young birds. All strains of Af. gallisepticumshowed some proclivity for respiratory tissues. Signs, gross lesions and re-coveries of mycoplasma frequently failed to correlate. Perosis was seen inonly two poults; these were infected with M. gallinarum with which thecondition may, or may not, be associated. Serological reactions to boththe rapid serum agglutination and haemagglutination inhibition tests dev-eloped in the 3rd and 4th weeks of life in all poults infected with Af. galli-septicum strains although false positives and negatives were recorded.

The main results of infection with the strains in turkey poults and in asimilar study in chicks are summarised.

INTRODUCTION

In a previous paper, Power and Jordan (1976) used three strains of M. gallisepticumand one strain of M. gallinarum and showed they differed in virulence as assessed bymortality in chicks and turkey poults. This present paper describes a sequel experimentin which the same four strains of mycoplasma were used to infect turkey poults undersimilar conditions in order to examine effects other than mortality. Clinical signs,gross lesions and the distribution and persistence of mycoplasma in a wide variety oftissues, together with serological results, were recorded in turkey poults at specifiedintervals after infection.

Received 7 December 1977Accepted 7 February 1978

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384 Judith Varley and F.T.W. Jordan

MATERIALS AND METHODS

Specific pathogen free (SPF) turkey poultsAn SPF turkey flock described previously (Power and Jordan, 1976) provided fertileturkey eggs which were hatched in isolation to provide day-old poults.

MediaBroth and agar media based on PPLO broth (Difco, Detroit, Michigan, U.S.A.) andincluding 15% swine serum were prepared as described previously (Power and Jordan,1976). Agar was dispensed into partitioned square petri dishes (Repliplates) (Sterilin,Teddington, England) using 1.5 ml/compartment.

MycoplasmaThese comprised M. gallisepticum strains, Mgl (an S6 strain recovered from SPF chicklung and cultured once on agar and once in both); Mg2 (the same S6 strain cultured154 times in artificial media); A514 and M. gallinarum (both cultured numerous timesin artificial media). Aliquots of these strains kept at -60°C were diluted to provideinocula of 106 colony forming units (cfu's)/poult for Mg2, A514 andM gallinarumand approximately 102 cfu's of Mgl, because larger doses of Mgl caused high mortal-ity. Viable counts on inocula and confirmation of mycoplasma species for inoculationand after recovery from tissues were undertaken as described by Power and Jordan(1976).

Experimental procedureHousing and infection of turkey poults. Poults were hatched in isolation, divided intofive separate groups, each of which was then housed in a separate isolation pen andinfected with mycoplasma within 24 hours of hatching. Infection was by injection of0.1 ml of appropriately diluted mycoplasma suspension (or 0.1 ml mycoplasma broth)into the abdomen near the umbilicus.

Clinical observation, sampling and serology. Three poults (usually) were taken at 2,3or 4-day intervals up to 28 days of life as indicated in the footnote to Table 1. Theywere taken at random unless showing nervous signs when such birds were deliberatelyselected. A blood sample was collected, clinical signs, ante-mortem and gross lesionsat post-mortem examination were recorded and tissues were cultured for mycoplasma.Tissues cultured were as indicated in Table 1. The range of tissues cultured were simi-lar to those described in a parallel study in the chick (Varley and Jordan, 1978) exceptthat during the 3rd and 4th weeks, the foot pads were cultured in addition. Serologicaltests were also similar except that a 0.75% saline suspension of washed turkey erythro-cytes collected 24 hours previously was used in the haemagglutination inhibition(HAI) test.

All experiments were terminated when turkey poults were 28 days of age.

RESULTS

Recovery of mycoplasmaRecoveries of mycoplasma between 0 and 28 days are shown in Table 1.

Mgl was isolated from 26 of the 34 poults (76%) in a proportion of all tissues exam-ined. Until day 11, mycoplasma were recovered from most tissues of most birds butin highest proportions from the abdominal air sacs and the brain (over 70% of eachof the tissues cultured). After day 12, there were three exceptional birds in whichmycoplasma were present in almost all tissues, but in many of the others, recoverieswere restricted to one or two tissues. Consequently, between 12 and 28 days, and

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Table 1. Mycoplasma recoveries from tissues of turkey poults aged 2-28 days infected within 24 hours of hatching withMgl*, Mg2b, A514C or M. gallinarumd.

Mycoplasma strain

Mgl.i% recovery

MB?.?.% recovery

A514C

% recovery

M. gallinarum'1

% recovery

Infr

a-or

bita

lsi

nus

10/36*

28

1/31

3

3/43

7

1/28

4

Tra

chea

13/36

36

3/31

10

5/43

12

1/28

4

Lef

t lu

ng

17/36

47

4/31

13

8/43

19

1/28

4L

eft

abdo

m-

inal

air

sac

18/36

50

2/31

6

2/43

5

1/27

4

Cla

vicu

lar

air s

ac

13/36

36

2/31

6

3/43

7

1/28

4

Per

icar

dium

10/36

28

1/31

3

2/25

8

0/28

-

Hea

rt b

lood

and

mus

cle

13/36

36

3/31

10

8/42

19

1/28

4

Clo

aca

3/36

8

1/31

3

1/43

2

0/28

Cae

cal

tons

il

10/36

28

1/31

3

1/43

2

2/28

7

Bur

sa

20/36

56

2/31

6

7/43

16

2/28

7

Spl

een

14/36

39

4/31

13

8/43

19

2/28

7

Liv

er

14/36

39

2/31

6

3/43

7

1/28

4

Gon

ad

14/36

39

3/31

10

5/41

12

2/28

7

Kid

ney

16/36

44

5/31

16

10/43

23

2/28

7

Yol

k

13/25

52

8/27

30

14/31

45

7/22

32

Rig

ht a

nd

left

hoc

ks

29/72

40

9/62

15

28/86

33

2/56

4

I!2 #2

1/22

5

0/28

-

17/36

47

0/24

Lef

t con-

junc

tiva

8/36.

22

1/31

3

1/43

2

0/28

-

Bra

in

13/31

42

0/20

-

2/26

8

0/28

-

Poults were killed and cultured as follows:Mgl on days 4(5); 6(6); 8(6); 11; 12(1); 14; 17; 20; 24; 28(2)Mg2 on days 2; 4; 6; 9; 11(2); 13; 15(2); 17; 20; 24; 27A514on days 3(2); 5; 7; 9; 12; 14; 16; 19; 21; 24; 27(11); 28(5)M. gallinarum on days 4(4); 7; 10(4); 13(4); 17; 19; 21; 283 poults were cultured each day unless indicated otherwiseFigures in parenthesis indicate the number cultured that daya Mgl = M. gallisepticum, S6 of low passage in artificial mediab Mg2 = Af. gallisepticum, S6 of high passage in artificial mediac A514 = M. gallisepticum, AS 14 of high passage in artificial mediad M. gallinarum =M. gallinarum of high passage in artificial mediae Foot pads only cultured between days 14 and 28 inclusivef No. of tissues from which mycoplasma isolated/No, of tissues cultured for mycoplasma

•Ioo

•a

I3

5'

I1

oo

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Table 2. Correlation of clinical signs and gross lesions with mycoplasma recoveries in turkey poults aged 2-28 days infectedwithin 24 hours of hatching with Mgla, Mg2b, A514C or M. gallinarumd.

ooON

Mycoplasmastrain

Mgla

Mg2b

A514C

M.gallinarurrf1

Week inwhichpoults

examined

12341234

1234

1234

No.examined

121365

8886

899

17

7893

Signs, lesions and recoveriesNervous

Signs

CN —

|

11

1

1 1

1 1

1 1

1 1 1

1

Brain

Grosslesions

—

CN

1

1

1 1

1 1

1 1

1 1

1 1

1 1

Mycoplasmarecovered

74

1

1 1

1 1

11

1 1

1 1

Respiratory

Signs

23

632

33

1 1

1 1

Grosslesions

56

34

112

- 1

1 1

Mycoplasma*recovered

10711

13

38

1

1

Locomotory

Swollenhocks

1 1

1

1

1

1 1

CN

OO

1 1

1 1

Mycoplasmarecoveredfrom hocksynovialfluid

9511

32

4659

11

a Mgl = M. gallisepticum, S6 of low passage in artificial mediab Mg2 = M. gallisepticum, S6 of high passage in artificial mediac A514 = M. gallisepticum, A514 of high passage in artificial mediad M. gallinarum = M. gallinarum of high passage in artificial mediae Mycoplasma recovered from one or more of the following tissues: trachea, lung, clavicular or abdominal air sacs.

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Mycoplasma infection in turkey poults 387

throughout the whole 4 weeks overall, most Mgl recoveries were from the bursa ofFabricius, yolk, abdominal air sacs and lungs, whilst fewest recoveries were from thecloaca and foot pad.

Mg2 was isolated from 13 of the 30 poults (43%) examined. Recoveries were madefrom a small proportion of all tissues except brains and foot pads. In only threepoults, cultured on days 6 and 9, were mycoplasma isolated from most tissues, butin other birds, before and after this time, recoveries were sporadic and equally infre-quently made from all tissues except yolk.

A514 was isolated from 31 of the 43 poults (72%) examined. Mycoplasma were re-covered from a small proportion of all tissues, and, until day 14, usually from severaltissues in each bird. After day 14, apart from two exceptional isolations (one in thegonad and the other in yolk), all recoveries were from either hocks or foot pads, andfrequently from both sites in an individual. Throughout the whole 4 weeks, A514was recovered most frequently from the foot pads, hocks and yolk.

M. gallinamm was isolated from nine of the 28 poults (32%) examined. In two ex-ceptional poults, cultured on days 4 and 10, mycoplasma were isolated from manytissues. There were occasional recoveries from yolk but, otherwise, mycoplasmawere not recovered from any tissues in any birds.

Profuse or confluent growth of colonies at initial isolation occurred only during thefirst 12 days in all tissues of Mgl infected poults and in yolk recoveries from allgroups. Otherwise, colony growth at initial isolation was usually sparse from alltissues.

Correlation of clinical signs and lesions with recovery of mycoplasmaThe correlation of clinical signs and lesions with recoveries of mycoplasma frombrains, respiratory tissues and the synovial fluid of hocks is shown in Table 2. Theincidence of swollen foot pads is not tabulated and this was the only other sign orlesion observed.

Mgl infected poultsNervous signs and lesions. During the first 2 weeks, on days 6 and 8, three poultsshowed nervous signs including rhythmical head flagging movements, the head beingheld to one side, walking in circles and loss of balance. Two of these birds, but notthe third, had single or multiple miliary gross lesions on one or both cerebral hemi-spheres. Similar gross cerebral lesions occurred in another poult examined on day 11,although in this bird nervous signs were absent. Mycoplasma were isolated from thebrains of all four poults and also from another seven, so, in total, mycoplasma wereisolated from 11 of the 25 brains cultured at this time. In the 3rd and 4th weeks,nervous signs and gross cerebral lesions were absent and mycoplasma were isolatedfrom only one brain.

Respiratory signs and lesions. In the first 2 weeks, five poults had slight dry rales andsneezing, and of these, three showed a degree of airsacculitis. Air sacculitis, character-ised by thickened air sac walls with diffused or discrete white lesions, was seen in atotal of five of 12 in the 1st week and in six of 13 in the 2nd week, whilst correspond-ing isolations of mycoplasma from the respiratory tract were ten in the 1 st and sevenin the 2nd week. Lesions were often, but not inevitably, associated with recoveriesand vice versa. In the 3rd and 4th weeks, respiratory signs and lesions were absent andmycoplasma were isolated from the respiratory tracts of only one bird in each week.

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388 Judith Varley and F.T.W. Jordan

Hock lesions. Throughout the 4 weeks, no swollen hocks were seen, although myco-plasma were isolated quite often. In the first 2 weeks, mycoplasma were isolatedfrom the synovial fluid of both hocks in 13, and from the synovial fluid of one hockin a 14th poult. In the 3rd week, isolations were confined to the synovial fluid of onehock in one bird and in the 4th week to that of both hocks of one bird.

Mg2 infected poultsNervous signs and lesions. Throughout the 4 weeks, neither nervous signs nor grosscerebral lesions were seen and no mycoplasma were recovered from brains.

Respiratory signs and lesions. In the 1st week, slight dry rales occurred in six of thenine poults examined, and, although three of these birds also had air sacculitis, myco-plasma were isolated from the respiratory tract of only one. In the 2nd week, dryrales were present in three poults, two of which had air sacculitis, as did another twopoults without rales; mycoplasma were isolated from the respiratory tracts of threebirds, one with rales, one with air sacculitis and the third with neither. In the 3rd week,dry rales occurred in two poults although no air sacculitis was seen and no mycoplasmawere isolated. In the 4th week, neither signs nor lesions occurred and, again, no myco-plasma were isolated.

Hock lesions. Throughout the 4 weeks, only one swollen hock was seen; this occurredin a poult examined on day 13 and no mycoplasma were isolated from the synovialfluid of either hock. In the 1st and 2nd weeks, however, and in the absence of lesions,mycoplasma were recovered from the synovial fluid of both hocks in five other birds,three in the 1st and two in the 2nd week, respectively.

A514 infected poultsNervous signs and lesions. Throughout the 4 weeks, neither nervous signs nor grosscerebral lesions were seen, although mycoplasma were isolated from the brains of twopoults, one on day 7 and the other on day 14.

Respiratory signs and lesions. In the 1st week, eight poults were examined. Dry raleswere present in three, but there was no air sacculitis in these or other birds, althougha fourth poult had oedematous congested lungs. Mycoplasma were cultured from therespiratory tracts of three poults, one bird with respiratory signs, one with lunglesions and the third with neither signs nor lesions. In the 2nd week, three of thenine birds had dry rales, and one of these had exudate in the clavicular air sac. Myco-plasma were isolated from the respiratory tract of this, one other bird with signs andfrom five birds with neither signs nor lesions. In the 3rd and 4th weeks, neither ralesnor air sacculitis occurred and, although five birds in the 3rd week had exudate in theclavicular air sac, there were no recoveries of mycoplasma from the respiratory tracts.

Hock lesions. In the first 2 weeks, no swollen hocks occurred although mycoplasmawere isolated from the synovial fluid of one or both hocks in four of eight poults inthe 1st, and six of nine poults in the 2nd week. In the 3rd week, two of nine poultsshowed slight swellings in both hocks, and mycoplasma were isolated from the syno-vial fluid of both hocks in one of these poults and also from the apparently normalhocks of four other poults. In the 4th week, 17 birds were examined, in eight ofwhich one or both hocks were swollen. At this time, many of the swellings seemedto be associated with excess clear viscous fluid between and around the articulatingsurfaces. Mycoplasma were isolated from birds with and without hock lesions; in twobirds isolations were made in the absence of lesions, in six birds isolations and lesionscorresponded and in two birds no mycoplasma were isolated although hocks wereslightly swollen.

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Mycoplasma infection in turkey poults 389

M. gallinarum infected poultsNervous signs and lesions. Throughout the 4 weeks, neither nervous signs nor grosscerebral lesions occurred and no mycoplasma were isolated from brains.

Respiratory signs and lesions. Throughout the period, there were no respiratory signs,although lung oedema occurred in one bird examined at 4 days. Mycoplasma were notrecovered from respiratory tissues in this bird, but were present in two others culturedon days 10 and 27.

Hock lesions. Perosis occurred in two birds examined at 28 days. In both birds thelesion was unilateral, with malformation of one condyle of the tibiotarsus and conse-quent slipping of the associated tendon. Mycoplasma were not isolated from the syno-vial fluid of either hock in these birds, but were isolated from one hock in each of twopoults cultured on days 4 and 10.

Foot pad lesionsFoot pads were cultured only in the 3rd and 4th weeks, when gross swellings of thetissues were observed in some A514 infected turkey poults. The foot pads of all poults,in all four groups, were cultured in these weeks, whether lesions were seen or not. Atthis time, seven of the 18 poults infected with A514 developed swollen foot pads,often unilaterally. In three poults where swellings were particularly marked, largevolumes of thin white exudate were released when foot pads were incised; mycoplasmawere isolated from both foot pads of these three birds and in total from 17 of the 36foot pads cultured (12 of the 18 birds examined). Mgl, Mg2 andM. gallinarum infec-ted poults did not develop swollen foot pads, and mycoplasma were isolated on onlyone occasion; mycoplasma recoveries relative to the numbers of foot pads culturedwere: Mgl poults, 1/22; Mg2 poults, 0/28;M gallinarum poults, 0/28, representing11, 14 and 12 birds in each infection group, respectively.

Correlation of mycoplasma recovery with serological resultsTable 3 summarises the results of recovery and serological examination in Mgl, Mg2and A514 infected turkey poults. Haemagglutination inhibition (HAI) titres greaterthan 1/40 were interpreted as positive as titres as high as this were obtained in controlsera from broth inoculated and uninfected poults of the same age tested simultaneous-ly-Mgl infected poults. In the 1st week, mycoplasma were recovered from all poults andin succeeding weeks from a proportion of poults. Only in the 4th week were positiveserological reactions seen when mycoplasma were isolated from three poults, two seraof which were RSA and two HAI positive, although only one serum was positive toboth tests. One poult from which mycoplasma were not isolated also showed an HAIpositive reaction.

Mg2 infected poults. Through the first 3 weeks, mycoplasma were recovered from adecreasing proportion of poults each week, and from none in the 4th week. Duringthe 3rd week, positive serological reactions were seen, and, of the two birds fromwhich mycoplasma were isolated, one serum was RSA and the other HAI positive,whilst in six poults from which mycoplasma were not isolated, one was RSA and fourHAI positive. In the 4th week, sera were negative to both tests.

A154 infected poults. In the first 2 weeks, mycoplasma were recovered from all andin weeks 3 and 4 from a proportion of poults. At the end of the 2nd week, one poultfrom which mycoplasma was recovered had an RSA positive serum. In the 3rd week,mycoplasma were isolated from seven poults, four of which had RSA positive sera

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390 Judith Varley and F.T.W. Jordan

Table 3. Correlation of the recovery o/M. gallisepticum with serologicalresults in turkey poults aged 2-28 days infected within 24 hoursof hatching with Mgla, Mg2b, or A514C.

Mycoplasmastrain

Mgla

Mgl totals

Mg2b

Mg2 totals

A514C

A514 totals

Examinationweek(days)

1(0-7 days)2(8-14 days)3(15-21 days)4(22-28 days)

1234

1234

Nos. of poultsfrom whichmycoplasmarecovered

12/127/84/93/5

26/345/86/82/8

L_ 0/613/30

5/55/57/9

14/1431/43

Serological results in poults fromwhich mycoplasma were

recoveredRSAd

0/12f

0/70/42/3

2/26

0/50/61/2

1/13

0/51/54/7

14/14

19/31

HAIe

0/120/70/42/3

2/260/50/61/2

1/13

0/50/52/7

14/14

16/31

not recoveredRSA

0/180/50/2

0/8

0/30/21/60/61/17

0/24/10

4/12

HAI

0/10/51/2

1/8

0/30/24/60/6

4/17

0/22/102/12

a Mgl = M. gallisepticum, S6 of low passage in artificial mediab Mg2 = M. gallisepticum, S6 of high passage in artificial mediac ASM = M. gallisepticum, AS 14 of high passage in artificial mediad RSA = Rapid serum agglutination teste HAI = Haemagglutination inhibition test

Burroughs Wellcome antigens were used for both testsf No. of serological positives/No, of cultural positivesg No. of serological positives/No, of cultural negatives

whilst two were HAI positive in addition. In the 4th week, mycoplasma were isolatedfrom 14 of the 24 poults examined and all 14 sera were both RSA and HAI positive.Of the ten poults from which mycoplasma were not isolated, four had RSA positivesera, two of which were HAI positive in addition.

M. gallinarum infected poults. Sera were collected and tested withM gallispeticumantigens but neither RSA nor HAI positive reactions were seen.

DISCUSSION

These experiments were undertaken in relatively few turkey poults, and conclusionsmust be qualified accordingly. The results show that the virulent Mgl strain was re-covered from tissues more frequently than were other strains. Mgl was isolated frommany tissues in most poults during the first 11 days, but thereafter, isolations wereoccasional and sometimes from only one tissue in an individual: usually a respiratorytissue or the bursa of Fabricius. A514 was recovered from a proportion of tissues inall poults up to day 14, but subsequently, although isolations still occurred in manybirds, they were localised to hock joints and foot pads. In contrast, Mg2 and

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Mycoplasma infection in tuikey poults 391

M. gallinarum were infrequently isolated from few tissues in most poults, althoughfrom rare individuals in both groups, recoveries were made from many tissues. Thereis no previous report in which as wide a range of tissues has been cultured in turkeysinfected with M. gallisepticum. However, Peters et al (1966) recovered the S6 strainfrom respiratory tissues for up to 30 days and from the brain and kidney for 21 days,indicating that mycoplasma persisted in a wider range of tissues and for longer thanoccurred in any group in the current experiments. These differences may be partlyexplained by the different criteria whereby mycoplasma were recognised in the twoexperiments. Alternatively, the period for which mycoplasma could be recoveredfrom tissues may have been prolonged by infections with a larger mycoplasma ino-culum (this was unspecified in terms of cfu s) perhaps of greater virulence, or bycontaminants present in the inoculum (E. coli, Micrococcus, and Streptococcus wererecorded) which may have exacerbated the mycoplasma infection, as may a priorinfection in the birds themselves (e.g. withAf. meleagridis). Furthermore, poultswere infected at different ages in the two experiments.

Many recoveries of all four strains were made from tissues in the absence of clinicalsigns and lesions, suggesting that these are not the best criteria for selecting tissuesto culture for diagnosis. Nervous signs and gross lesions on the cerebral hemisphereswere seen only in Mgl infected poults, where sometimes both features were presentin an individual, but either could also occur independently. Mycoplasma were recov-ered from the brains of Mgl infected poults and from the brains of only two others(these were infected with A514). No signs or lesions were seen, and neither weremycoplasma recovered from the brains of other poults in the A514 or other infectiongroups. These results confirm the neurotropism of the S6 strain in turkeys which waspreviously reported by Zander (1961) and by Thomas et al (1966). Both authors des-cribed nervous signs similar to those seen in the current experiments, but neither re-ported seeing gross brain lesions. Cordy and Adler (1957) recorded "obvious" brainlesions in one turkey infected with the S6 strain but the appearance and location ofthe lesions were not specified. We have seen no other reports of gross brain lesions re-sulting from the infection of turkeys with the S6 or other mycoplasma strains, andthose briefly described here will be published in full subsequently.

In all groups, respiratory signs were infrequent, and signs, gross lesions (mainly airsacculitis) and mycoplasma recoveries rarely coincided. However, all three M. galli-septicum strains were recovered frequently from the respiratory tract in the first 2weeks, so it appeared that they all showed some proclivity for respiratory tissues,correlating with previous reports of S6 by Zander (1961), Adler and Sadler (1965)and Nutor (1969) and with reports of A514 by Nutor (1969) and Wannop et al(1971).

With one exception, swollen hocks were restricted to poults infected with A514 inIke 3rd and 4th weeks. Mycoplasma were recovered from the synovial fluid of hocksof poults in all groups but mainly in the first 2 weeks in the case of Mgl, Mg2 andM. gallinarum, whereas they occurred throughout the 4 weeks with A514 and withgood correlation between mycoplasma isolations and swollen hocks by the 4th week.Also during the 3rd and 4th weeks, the foot pads of many A514 infected poults be-came swollen and mycoplasma were isolated from these and the foot pads of otherA514 infected poults at this time. In contrast, no poults in other groups developedswollen foot pads and only one isolation was made. It was concluded therefore thatthe A514 strain showed a particular proclivity for joints in turkeys; However, at notime was deformation of the tarso-metatarsus seen, nor were there any signs of

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392 Judith Varley and F.T.W. Jordan

perosis, features which characterise T.S.'65 (Working Party Reports 1965 and 1966)and which were described by Wannop et al (1971) in A514 infected poults and byWise and Fuller (1975) in poults infected with a field strain of M. gallisepticum.Wannop et al. (1971) used commercial poults and it is possible some intercurrent in-fection may have exacerbated the condition; Wise and Fuller (1975) used a strainother than the A514, and a greater weight of infection was present in the inoculum,and both or either of these factors might explain the different results. In the currentexperiments, perosis was seen in two poults infected with M. gallinarum, and as it didnot occur in other groups, the condition may be associated with the infection. Dierkset al. (1967) found thatM. gallinarum was not pathogenic in turkey poults and furtherexperiments would have to be undertaken in order to corroborate or refute the sug-gested association. In such experiments, it might be advantageous to culture the interiorof the hock bones.

Positive RSA and HAI sera occurred in some poults infected with all three strains ofM. gallisepticum from the 3rd week; although false positives and negatives occurredwith both tests, suggesting both to be unreliable in young turkey poults.

Infected turkey poults differ in several respects from correspondingly infected chicks(Varley and Jordan, 1978):

(1) On the whole, Mg2, A514 and M. gallinarum were less frequently recoveredfrom turkeys than from chicks infected with equivalent strains, suggesting turkeypoults were in general less susceptible to these strains than were chicks.

(2) This was not true of Mgl, however, since when 104 cfu s were used to infectboth chicks and poults, so many poults died so rapidly that their higher susceptibilitywas in no dount (Varley, unpublished).

(3) In chicks, there was a period in whichM. gallisepticum strains were very wide-spread, with recoveries made from most individuals and from most tissues; it occurredin Mgl, Mg2 and A514 infected chicks for 18, 14 and 12 days, respectively. A similaroccurrence was restricted to Mgl infected turkey poults, and then for only 11 days.

(4) Proclivity for brain tissue was shown by Mgl in both chicks and turkey poultsin which similar clinical signs and similar gross lesions on the cerebral hemispheresoccurred, and in both species, mycoplasma were recovered frequently from the brain.Although neither signs nor lesions were present in Mg2 infected chicks or poults, my-coplasma were recovered frequently from chick but not from poult brains. This mayindicate chicks are more susceptible than poults to the neurotropism of Mg2, or per-haps the strain is specifically neurotropic to the chick brain.

(5) Both Mgl and Mg2 showed proclivity for hock joints in chicks, and causedsome swellings, whereas neither strain showed similar proclivity for turkey hocks. Incontrast, A514 showed proclivity for turkey hocks and foot pads causing swellings atboth sites, whereas no similar proclivity was apparent for chick hocks.

(6) All three strains of M. gallisepticum could be isolated from respiratory tissuesin both chicks and turkey poults but more turkeys showed clinical signs and air saccu-litis was also more prevalent than in chicks. It is possible, therefore, that although allthree strains showed proclivity for respiratory tissues, turkey poults were more suscep-tible than chicks to the respiratory component of the disease.

(7) In both chicks and turkey poults, it was possible to isolate mycoplasma fromtissues in the absence of clinical signs and gross lesions, whilst conversely, mycoplasmawere not always isolated when signs and lesions were present.

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Mycoplasma infection in turkey poults 393

(8) In general, chicks were more immunologically responsive than were turkeypoults; this was shown by a greater proportion of both RSA and HAI positive seraand higher HAI titres in chicks. Similar observations were made by Jordan andKulasegaram (1968) in older chickens and turkey poults infected with M gallisepti-cum, and it seems likely (Aitken, unpublished results) that the turkey is generallyless responsive than the chicken to antigens of a wider range. Mgl induced a prematureHAI response in chicks; this may be peculiar to the strain and host since comparableresults were not recorded in turkey poults.

(9) M. gallinarum was not associated with clinical signs or lesionsin chicks, althoughit was recovered from the respiratory systems in a large proportion of adults whichhad been infected as embryos. In turkey poults, this organism might possibly be assoc-iated with certain types of lameness and this would have to be examined more tho-roughly in further experiments.

A cknowledgemen tsWe wish to thank the Agricultural Research Council for financial support and CarolHughes for cheerful and competent technical help.

REFERENCES

Adler, H.E. and Sadler, W.W. (1965). Response of the turkey to Mycoplasma gallisepticum infec-tion. Poultry Science, 44: 136-140.

Cordy, D.R. and Adler, H.E. (1957). The pathogenesis of the encephalitis in turkey poults pro-duced by a neurotropic pleuropneumonia-like organism. A vian Diseases, 1: 235-245.

Dierks, R.E., Newman, J.A. and Pomeroy, B.S. (1967). Characterisation of avian mycoplasma.Annals of the New York Academy of Sciences, 143: 170-189.

Jordan, F. T. W. and Kulasegaram, P. (1968). Serological tests for the detection of antibodies toMycoplasma gallisepticum in chickens and turkeys. Journal of Hygiene, Cambridge, 66:249-267.

Nutor, B.L. (1969). Studies on avian mycoplasma. M. V.Sc. thesis, University of LiverpoolPeters, R.L., Faber, J.E., Keenum, W.D. and de Volt, H.M. (1966). Distribution of Mycoplasma

gallisepticum in selected tissues and organs of artificially infected turkeys. Poultry Science,45: 913-923.

Power, J. and Jordan, F.T.W. (1976). A comparison of the virulence of three strains of Myco-plasma gallisepticum and one strain of Mycoplasma gallinarum in chicks, turkey poults,tracheal organ cultures and embryonated fowl eggs. Research in Veterinary Science, 21:41-46.

Thomas, L., Davidson, M. and McCluskey, R.T. (1966). Studies of PPLO infection. The produc-tion of cerebral polyartertis by Mycoplasma gallisepticum in turkeys; the neurotoxicproperty of the mycoplasma. Journal of Experimental Medicine, 123: 897-912.

Text of Working Party on New Syndrome in Turkey Poults (1965). Veterinary Record, 77: 1292.Text of Working Party on New Syndrome in Turkey Poults (1966). Veterinary Record, 79: 805-806.Varley, J. and Jordan, F. T. W. (19 78). The response of chickens to experimental infection with

strains of M. gallisepticum of different virulence and Af. gallinarum. Avian Pathology, 7:157-170.

Wannop, C.C., Butler, E.J. andPearson, A.W. (1971). Experimental reproduction of turkey syn-drome '65 by infection with Af. gallisepticum. Veterinary Record, 88: 30-33.

Wise, D.R. and Fuller, M.K. (1975). Experimental reproduction of turkey syndrome '65 withMycoplasma meleagridis and Af. gallisepticum and associated changes in serum proteincharacteristics. Research in Veterinary Science, 19: 201-203.

Zander, D. V. (1961). Origin of S6 strain mycoplasma. Avian Diseases, 5: 154-156.

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394 Judith Varlcy and F.T.W. Jordan

RESUME

Réponse de dindonneaux à l'infection expérimentaleprovoquée par des souches plus ou moins pathogènes de

M. gallisepticum et par M. gallinarum

Chez des dindonneaux jusqu'à l'âge de 28 jours, une souche pathogène S6 de M. galli-septicum a été isolée plus souvent, de tissus plus nombreux et pendant plus longtempsque d'autres souches.

Le neurotropisme de cette souche pathogène est suggéré par les signes nerveux et parles lésions macroscopiques cérébrales chez les dindonneaux, ainsi que par l'isolementfréquent à partir du cerveau.

Toutes les souches de M. gallisepticum ont été isolées à partir du liquide synovial desarticulations tibio-tarsiennes mais l'enflure de cette articulation et le gonflement plan-taire n'ont été observés que chez les dindonneaux infectés par la soucha A514.

Bien que toutes les souches aient montré une tendance à l'infection des articulations,il semblerait cependant que seule la souche A514 ait eu un effet pathogène marquéchez ces jeunes oiseaux.

Toutes les souches de M. gallisepticum ont montré un certain tropisme pour l'appareilrespiratoire. Il y a eu fréquemment absence de corrélation entre les symptômes, leslésions macroscopiques et l'isolement de mycoplasmes. Du pérosis a été observé seule-ment chez deux dindonneaux; ces oiseaux étaient infectés par M. gallinarum, ce quipeut être ou non en relation avec la lésion.

Des réactions sérologiques en séro-agglutination rapide et en inhibition de l'hémag-glutination apparaissent pendant la 3ème et la 4ème semaine de vie chez tous les din-donneaux infectés par les souches de M. gallisepticum; de fausses réactions positiveset négatives ont cependant été observées.

Les principaux résultats de l'infection par ces souches chez les dindonneaux et com-parativement chez les poussins sont résumés dans cet article.

ZUSAMMENFASSUNG

Die Reaktion von Putenküken gegenüber einer experimentellenInfektion mit M. gallisepticumstämmen von unterschiedlicher

Virulenz und mit M. gallinarum

Aus Putenküken im Alter von 28 Tagen wurde ein virulenter S6-Stamm von M. galli-septicum häufiger und aus mehr Geweben und während einer längeren Zeitperioderückisoliert als andere Stämme. Der virulente Stamm verursachte nervöse Symptome,pathologische Gehirnveränderungen bei Putchen und wurde besonders aus dem Ge-hirn isoliert, was für seinen Neurotropismus spricht. Alle M. gallisepticum-Stämmewurden aus der Synovialflüssigkeit der Sprunggelenke isoliert, aber geschwollene Ge-lenke und Fußsohlen wurden nur bei den Küken beobachte, die mit Stamm A514 in-fiziert worden waren. Anscheinend besitzen zwar alle Stämme eine Vorliebe fürGelenke, aber nur Stamm A514 hat tatsächlich eine pathogène Wirkung bei jungenTieren. Alle Stämme von M. gallisepticum zeigten eine Affinität zu respiratorischemGewebe. Aber Krankheitszeichen, pathologische Veränderungen und Mycoplasmen-rückisolierungsrate stimmten häufig nicht überein. Perosis konnte nur bei 2 Puten-küken festgestellt werden, diese waren mit M. gallisepticum infiziert. Es ist unsicher,ob die Veränderungen mit der Infektion irgend etwas zu tun haben. SerologischeReaktionen bei der Schnellserumagglutination und bei dem Haemagglutinationshem-mungstest traten in der 3. und 4. Lebenswoche bei allen Putchen auf, die mit

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Mycoplasma infection in turkey poults 395

M. gallisepticumstämmen infiziert worden waren. Es wurden auch falsche positive undfalsche negative Reaktionen beobachtet.

Die Hauptbefunde bei Infektionen von Putenküken und von Hühnerküken in einemähnlichen Versuch mit diesen Stämmen werden zusammengefaßt.

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