Department of Agriculture, Food and the MarineTeagascDeposited by bulk impor

Costello, Eamon

Finn, M.

Flanagan, Pat

Flynn, Orla

Griffin, John M.

O'Grady, D.

Quigley, Frances

O\u27Grady, D.

Irish Universities

A study of within-herd transmission of Mycobacterium bovis infection from newly purchased infected cattle, using dna fingerprinting techniques

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Title A study of within-herd transmission of Mycobacterium bovis infection from newly purchased infected cattle, using dna fingerprinting techniquesAuthors(s) Flanagan, Pat, Finn, M., Flynn, Orla, Costello, Eamon, O'Grady, D., Quigley, Frances, Griffin, John M.Publication date 1999-09Publication information Flanagan, Pat, M. Finn, Orla Flynn, Eamon Costello, D. O’Grady, Frances Quigley, and John M. Griffin. A Study of within-Herd Transmission of Mycobacterium Bovis Infection from Newly Purchased Infected Cattle, Using Dna Fingerprinting Techniques. Edited by John D. Collins and Robert F. Hammond. University College Dublin. Centre for Veterinary Epidemiology and Risk Analysis, September, 1999.Series Selected Papers, 1998Publisher University College Dublin. Centre for Veterinary Epidemiology and Risk AnalysisItem record/more informationhttp://hdl.handle.net/10197/8827Downloaded 2023-11-01T04:02:15ZThe UCD community has made this article openly available. Please share how this accessbenefits you. Your story matters! (@ucd_oa)© Some rights reserved. For more informationA Study of Within-Herd Transmission of Mycobacterium bovis from newly Purchased Infected Cattle, using DNA Fingerprinting Techniques P. Flanagan,1 M. Finn2, 0. Flynn, E. Costello, D.O'Grady, F. Quigley3 and J.M. Griffin Introduction In the Republic of Ire land, cattl e moveme nt has been cited as one on the main reasons for the failure to eradicate tubercu losis in cattle despite a comprehensive erad ication programme (O'Connor, 1986). On the other hand, when breakdowns in vo lving purchased animals were stud ied. it was concluded that the level o f tran ·miss ion of tuberculosis from the purchased animal was likely to be low (Griffi n, 1993). When a newly introduced animal is identified as a reactor in a purchasi ng herd (dest ina tion herd) it is sometimes d ifficu lt to establish whether the animal was infected before its arrival or afterwards. The use of desoxyri bonuc leic acid (DNA) fi nge rprinting techn ique, namely Restricti on Fragment Length Polymorphism (RFLP) typing, allows different strains of Mycobacterium hovis to be identified. The stra in of M. hovis present in an infec ted animal introduced into a destination herd in a new geographical area, may be different from the local strain , thus providing an opportunity to de termine the level of transmission of the former train from such an animal to in-contact animals in the destination herd. This study was undertaken j ointl y by the Central Veterinary Research Laboratory (CVRL), Abbotstown, the Laois and Offal y District Veterinary Offices (DVO) and the Tubercu losis In vestigation Unit (TI U), Univers ity College Dubli n. The study area was defined as County Laois and County Offaly. Objectives The objecti ves of the s tudy were as follows: I. To determine the proport ion of purchased M. hovis infected cattle that transmit infect ion to other cattle in the desti nation herd. 2. To compare the results of DNA fingerprinting with the findings of routine (field) epidemiological investigations, using the ER76 format. 3. To determine the leve l of transmission in the dest ination herd where the source of the breakdown is considered to be a newly introduced animal. 4. To create a profil e of the M. hovis RFLP types in the locality and to compare these with the RFLP types identified in other pa11s of lreland. A .. source herd". was defined as any herd in which a purchased animal had been in since its last tubercul in test. 1 Di strict Veteri nary Office. Port. Laoise. Co. Offa ly ~ Di stric t Veteri nary Office . Tullamore. Co. Offaly 3 Central Veteri nary Research Laboratory. Ahhotstown. Co.Dublin ERADffEAGASC 51 Tuberculosis In vestigation Un it, UCO A "destination herd" was defined as the herd in whic h the purchased animal/s were identified as reactors. Materials and Methods The study popu lation was compri sed of all new breakdowns in 1998 in the study area, where one or more of the reactor an ima ls was/were purchased si nee the previous tubercu Ii n test on the herd . When a tuberculin test has bee n carried out on a herd, a report of the findings is submitted to the DVO. At the interpretatio n by a Veterinary Inspector (VI) of a report on a tuberculin test at which reactors have been di sclosed, the breakdown is analysed for suitability in the strain typing study. When a breakdown qualifies for inclusion in the study, the following actions ensue: I. T he herdfile is labelled, so that tissue samples may be obtained from additional reactors, di sc losed in subsequent tests, with a view to RFLP typing of isolates. 2. The herdfile of the herd of origin is also labe lled so that, if reactors are di sclosed there at the next test, t issue samples may be obtai ned for RFLP typing of isolates . Where the herd-of-ori gin is outside the study area, the re levant DVO is notified. 3. The meat plant at which the reactor(s) are scheduled to be slaughtered is notified of the require me nt to have lymph nodes collected and submitted to CVRL for culture and subsequent RFLP typing. ERAD/TEAGASC 52 4. Nodes are collected from a ll purchased reactors and from a representati ve sample of non-purchased reactors. 5. Where M. hovis is cu ltured from one or more newly-introduced reactors in a breakdown, an ER76 epidemiological carried out. investigati on is This allows the Veterinary Inspector to give a we ighting from 1-5 to each of the poss ible sources of infection and allows a conclusion drawn as to likely or probable sources of infection, as described by O'Keeffe and O ' Driscoll (1997). 6. Data is entered in a Microsoft Access® database file , for anal ys is. RFLP typing is performed by digesting M. hovis DNA into fragments with an enzyme. Fragments are analysed for the presence of the repetiti ve DNA sequences PGRS and DR and the insertion sequence IS6 J I 0. Different strains will show vari ation in the number and size of fragments carrying these repetiti ve DNA sequences. Approximately 1,000 isolates from cattle badgers and deer have been typed at the CVRL. Over one hundred different RFLP types have been identified. To date, the most prevalent RFLP type was identified in approximately 20% of the isolates, recovered from animals in all areas of the country, and from all three an imal species. Other RFLP types have been assoc iated with geographical areas consisting of groups of adjoining counties and have been identified in cattl e, badge rs and deer in each area (Costello et al. , 1999). Tuberculosis Investigation Unit, UCD Results In the study area, 274 herds experienced a tuberculosis herd breakdown during 1998. Table 1 indicates the number of breakdowns in which lymph nodes were collected and sent to the CVRL. Nodes taken from cattle in 42 of the 68 herds which had breakdowns were subjected to mycobiological examination. Table 1. The number of herd breakdowns in Laois and Offaly in 1998, the number suitable for the strain typing project and the number from which lymph nodes were collected and sent to the Central Veterinary Research Laboratory. Laois Offaly Total number of tuberculosis herd breakdowns in 1998 150 124 Number of breakdowns with purchased reactors 47 21 Numbe r of breakdowns with purchased reactors where glands 40 12 were collected and sent to CVRL for cu lture and RFLP analysis* * This 1;ump ol herds will be refe rred to as specimen herds in the remainder o{the paper. The numbers of breakdowns at which an M. bovis strain was identified in one or more bought-in reactors are summarised in Table 2. Table 2. The number of specimen herds, the number of such herds in which a strain of M. bovis was identified and the number of herds in which a strain was identified in a purchased reactor. Laois Offal y Total Number of specimen herds 40 12 Nu mber of specimen herds where Strain was identified at the 2 1 9 CVRL Number of specimen herds where Strain was identified in one or 2 1 9 more purchased reactor(sr:''~ **These herds will he referred to as strain henls in the remainder o{ the paper. To date, M. bovis has not been recovered in the herd of origin of any of the bought-in animals. The number of strain herds in which the bought-in animal was considered the probable or most likely cause of breakdown 1s summarised in Table 3 Table 3. Relationship between the results of RFLP analysis and ER 76 based epidemiological investigations in attributing herd breakdowns to purchased animals. Laoi s Offalv Total number of strain herds 2 1 9 Number where epidemiological invest igation (ER76) deemed "bought- 12 6 in" as a like ly or probable cause of the breakdown ERAD/TEAGASC 53 Tuberculosis Investigation Unit, UCO The numbers of reactors disclosed in all breakdowns m 1998 and the number disclosed in the herds with bought-in animals among the reactors are outlined in Table 4. Of the 30 "strain herds" in the study, fourteen (47%) disclosed a single reactor on ly. Table 4. The number of reactors disclosed in herd breakdowns that had bought-in animals among the reactors. Total no. of Breakdowns breakdowns with bought-in 1998 in animal/s among reactors No. of 274 68 breakdowns No. of 87 1 158 reactors d isclosed in breakdowns Mean no. of 3.2 2.3 reactors per breakdown A total of 12 different strains were identified in the 2 1 Laois breakdowns while five strains were recovered from the nine Offaly breakdowns (Tab le 5). The frequency with which each strain occurred is outlined in Table 5. Strains A IAlA and DlH31 were common to both counties (Table 5). Only one herd had more than one strain identified in the reactors. A total of 57 herds of origin were identified in 16 counties. The distribution of these herds and their tuberculin test hi story before the departure of the purchased animal and immediately afterwards (i.e. post sale test) is outlined in Table 6. Discussion DNA fingerprinti ng is likely to prove to be to be a useful epidemiological tool in establishing whether a bought-ERAD/TEAGASC Breakdowns Breakdowns Breakdowns with bought- in which with one in ani mals strain was bought-in where strain identified reactor where was and where the bought-in identified only one of animal was 30 70 2.3 54 the reactors considered a was bought- likely or Ill probable source 17 8 29 12 1.7 1.5 in animal was likely to have been infected before, or after, purchase, and in determining if o nward transmission of M. bovis occurred in the destination herd. This can best be achieved if the strain type identified in the purchased animal/s is compared with strain types identified in other M. bovis infected animals in the herd of origin and in the destination herd. However, even though all reactor animals in a breakdown reveal the same strain type, the possibi lity that the bought-in animal/s and their in-contacts were infected from different sources with a prevalent strain cannot be ruled out. To date, because of practical difficulties it has not been possible to obtain samples from reactors in all of the herds of origin of purchased animals that were disclosed as reactors Tuberculosis Investigation Unit, UCD when tested in a "destination herd". In previous studies where the effect of the bought-in an imal on the purchasing herd was examined, the bought-in an imal was presumed to have been infected at the time of purchase if ev idence of tuberculosis was established in the herd of origin before or immediately after sale of the animal (0' Keeffe and O' Drisco ll , 1996; Flanagan and Kelly , 1996). All herd breakdowns in the present study, with the exception of one, disclosed only one strain type among the reactors (i.e. the purchased animal/s and the non-purchased animal/s yie lded the same strain type). Samples from a number of breakdowns in each county in the Republic of Ireland were previously strain-typed (Coste I lo et al., 1999). However, due to the relatively small numbers involved, it is unsafe to assume that strains that were not previously identified in the study area do not naturally occur there. Currently, herd breakdowns due to tuberculosis are routinely investigated to establ ish a probable or li kely cause. It is eas ier to establish the level of transmission from a bought-in an imal to in-contact animal/s where onl y one such bought-in animal had been introduced into the herd. ln the present study the mean number of reactors in breakdowns, in wh ich onl y one of the reactors was bought-in, was considerably lower than that for all breakdowns in 1998 (Table 4). Other studies have concluded that the level of onward transmission of tuberculosis from purchased animals, presumed in fected at the time of introduction into the destination herd, was likely to be low (Griffin , 1993; Wilesmith and Williams, 1986). In the present study, almost half of the breakdowns had only a single reactor identified, namely ERADffEAGASC 55 the bought-in animal , indicating the absence of within herd transmission in these cases. In some of the other breakdowns (i.e. wi th more than one reactor), two or more of the reactors had been bought-in. For instance, one herd breakdown disclosed 3 reactors, all of which had been purchased from the same herd. It is likely that these an imals were infected before their arri val into the destination herd, yet there was no evidence that any of the three an imals transmitted in fection to other animals in the "destinastion herd." ln another herd which had a large feedlot enterpri se, DNA fingerprint ing revealed different strains of M. hovis during the breakdown; in this case it was concluded, followi ng the epidemiological investigation, that there was little onward transmission of tuberculosis. When a bought-in reactor is traced to its herd of origin, the result of the first herd test post sale of the animal is as important as the history of the herd pre-sale in determining the likelihood that the animal was infected prior to the sale (Flanagan and Kell y, 1996). In the present study the number of herds of origin that had a hi tory of tuberculosis prior to the sale of the animal was ide ntical to the number of herds which had a reactor disclosed at the post-sale test (Table 6). Not all of the objecti ves of the present study were ful ly achieved at the time of writing this interim report. For instance the comparison of strains with the Strain Type Map of Ireland, now in preparation, wi ll be more meaningful when more information is added to that map. Equal ly, wi th the pass ing of time further strains will be identified in herds of origin which can be compared with the strains identified in the study herds. Tuberculosis Investigation Unit, UCO Table 5. The number of M. bovis strain types that were recovered in the study herds. Strain Type Co. Laois Co. Offaly IS6 100 PGRS DR Al A l A I I I A l AS A I 0 A l B l D I {) A l E2 A I 0 A2 Al B 0 I A3 Al G I 0 A4 A l H I 0 82 A l K 2 0 C l HI J 4 0 C l H9 J I 0 C2 14 E 3 0 D I H3 I 2 4 G I HS p 0 2 HS II E 0 1 R2 A l A I {) Table 6. The distribution of herds of origin by county, the number. with a tuberculosis history pre, and/or, post sale. Councy No. of herds of No. with a history of No. with reactors at first test . . tubercu losis before sale post-sale on gm Clare 6 Cork 7 Donegal I Galway 5 Kerry ..., .) Ki lke nny I Laoi s 6 Le itrim I Limerick I Louth I Mayo I Offaly 9 Roscommon 5 Sligo I Tipperary 8 W icklow I TOTAL 57 Conclusion It was concluded from this study that when herd breakdowns due to tuberculosis attributed to bought-in animal/s were investigated, the level of ERADffEAGASC 56 3 I 2 I 0 0 I 0 0 0 I I I I 0 0 I I 0 0 0 0 0 I 0 0 0 0 0 2 0 I 9 9 onward transmission to in-contact animals ranged from none to low. Tuberculosis Investigation Unit, UCO Acknowledgements The authors wish to thank the DVO veterinary staff who supplied data for the study, the meat plant veterinary staff who forwarded specimens to the laboratory and Professor J.D.Collins, UCO for his help in preparing the paper. The authors thank Messrs A. Gogarty & J. McGuirk, CVRL for the culture of samples. References Costello, E. , O'Grady, D. , Flynn , 0., O'Brien,R. , Rogers, M. , Quigley, F., Egan, J., and Griffin, J. ( 1999). Study of restriction fragment length polymorphism analysis and spoligotyping for epidemiological investigation of Mycobacterium bovis infection. Journal of Clinical Microbiology 37:3217-3222. ERADffEAGASC 57 Flanagan, P.A. and Kell y,G. ( 1996). A study of tuberculosis breakdowns in herds in wh ich some purchased animals were identified as reactors. · Iri sh Veterinary Journal 49: 704-706. Griffin , J. ( 1993). The role of bought-in cattle in herd breakdowns in part of County Cavan during 1989. Irish Veterinary Journal 46: 143- 148. O'Keeffe, J.J. and O ' Driscoll , H. ( 1997). Anal ysis of epidemiology reports on selected herds submitted during 1996-1997. In: Selected Papers ( 1996) Tuberculosis Investigation Unit, Uni versity College Dublin , 1-5 Wilesmith, J.W. and Williams, D.R. ( J 986). Tuberculous lesions in reactor cattle. Veterinary Record 119:51. Tuberc ulosis Investigation Unit, UCD 

A study of within-herd transmission of Mycobacterium bovis infection from newly purchased infected cattle, using dna fingerprinting techniques

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