Interntionl Journl of Poultry Science 9 (4): 395-400, 2010 ISSN 1682-8356 Asin Network for Scientific Informtion, 2010 Epidemiologicl Studies on Infectious Bursl Disese in Broiler Chickens in Hryn, Indi Sunil K. Mor, G. Nrng, N. Jindl, N.K. Mhjn, P.C. Shrm nd N.K. Rkh Deprtment of Veterinry Pulic Helth nd Epidemiology, College of Veterinry Sciences, CCS Hryn Agriculturl University, Hisr, 125004, Indi Astrct: The epidemiologicl dt of Infectious Bursl Disese (IBD) in 483 roiler chicken flocks were nlyzed from July, 2005 to June, 2008. Overll moridity, cumultive mortlity nd cse ftlity rte due to the disese were recorded s 4.54, 2.34 nd 51.69%, respectively. Of the totl IBD-ffected flocks, 192, 211, nd 80 flocks were ffected during the yers 2005-06, 2006-07 nd 2007-08, respectively. Dullness, depression, norexi, ruffled fethers nd inility to move were evident in lmost ll the IBD-ffected flocks. The ffected irds hd yellowish white or greenish yellow dirrhoe. At necropsy, the gross lesions were oserved minly in urs of Fricius followed y chnges in thigh nd rest muscles. The disese ws recorded throughout the yer. Mximum cses (52.80%) were oserved in irds of 21-30 dys of ge followed y 33.13% in the ge group of 31-40 dys. Although the disese ws oserved in oth IBDvccinted (334) nd unvccinted (149) flocks, percent moridity nd cumultive mortlity were higher in unvccinted flocks thn in the vccinted flocks. Fctors like improper vccintion, poor iosecurity mesures nd existence of very virulent strins of IBD virus could e the resons for disese in the vccinted flocks. Continuous surveillnce my help in etter understnding of the epidemiology of infectious ursl disese virus in roiler chickens in this region. Key words: Infectious ursl disese, epidemiology, roiler chickens, Hryn INTRODUCTION Infectious Bursl Disese (IBD) is n cute, highly contgious nd immunosuppressive virl disese of poultry cused y irn virus. After its first outrek in poultry in Southern Delwre in the United Sttes in 1962 (Cosgrove, 1962), the disese hs een recorded from ll over the world (Muller et l., 2003). Before 1987, the IBD ws essentilly su-clinicl in most prts of the world nd ws stisfctorily controlled y vccintion using ttenuted strins. Therefter, the vccintion filures hve een reported from different prts of the world. In the United Sttes, new IBD strins cused slight increse in mortlity; wheres, in Europe nd Asi, new virulent strins cused incresed mortlity in lyers nd roiler chickens (Chettle et l., 1989; Vn Den Berg et l., 1991). In Indi, the disese ws first reported y Mohnty et l. (1971). It ws oserved in its clssicl form until erly 1990's with mortlity upto 30%. Unvccinted chicken flocks experiencing hevy mortlity in Gurgon region of Hryn mnifested pprecily high ELISA ntiody titres for Infectious Bursl Disese Virus (IBDV) on seromonitoring (Asrni et l., 1993). Considerly high mortlity upto the tune of 70% due to IBD ws recorded in lte 1990 s with the emergence of Very Virulent (vv) strins of IBDV tht resulted in hevy economic losses to the poultry industry in the country (Sh et l., 1995). According to OIE nnul niml disese sttus, 281, 185, 167, 247, 260 nd 177 outreks of IBD were recorded during the yers 2002, 2003, 2004, 2005, 2006 nd 2007, respectively in Indi (http://www.oie.int/whis/ pulic.php). Such dt provide useful informtion out the prevlence of disese in n re/country which my help in understnding the epidemiology of the disese in etter wy. During pst two decdes, the stte of Hryn, north-western stte of Indi, hs mde rpid strides in poultry frming resulting in phenomenl growth of poultry industry in the stte with mny smll nd mrginl frmers opting for commercil roiler chicken frming for their livelihood. According to th 18 livestock census of 2007, totl poultry irds in the stte were 2,98,69,402 out of which only 3,54,490 were ckyrd poultry irds nd the remining 2,95,14,912 were domestic poultry (http://pshudhnhryn.gov. in/html/dist_livestock_census.htm). In this pper, we present epidemiologicl dt pertining to IBD in commercil roiler chicken flocks from July, 2005 to June, 2008 in prts of Hryn. This work is in continution to our previous report on epidemiologicl investigtion of IBD in commercil chicken in this stte (Jindl et l., 2004). MATERIALS AND METHODS Collection of dt: The epidemiologicl dt pertining to IBD in commercil roiler chickens from July 2005 to June 2008 were collected from Hisr, Jind, Bhiwni, Corresponding Author: Sunil K. Mor, Deprtment of Veterinry Pulic Helth nd Epidemiology, College of Veterinry Sciences, CCS Hryn Agriculturl University, Hisr, 125004, Indi 395
Sirs nd Ftehd districts of Hryn stte. The Deprtment of Veterinry Pulic Helth nd Epidemiology provides dignostic fcilities to the livestock nd poultry frmers of the stte through network of disese investigtion lortories (DI Ls). Live nd/or ded irds re rought y the poultry frmers to these lortories for disese investigtion on routine sis. Detiled informtion such s totl irds in flock, numer of irds ffected, numer of irds died, ge of the ffected irds, month of occurrence of the disese, vccintion sttus nd type of IBD vccines used ws otined from the ffected flocks. Clinicl findings nd gross pthologicl chnges in the IBD-ffected irds from ech flock were lso recorded. In order to study the temporl distriution of the disese, the yer ws divided into four qurters viz. July- Septemer (A), Octoer-Decemer (B), Jnury- Mrch (C) nd April-June (D). Qurters B nd C comprised of the winter seson; D, the summer seson nd A, the riny seson. The dt so collected were nlyzed sttisticlly using Z test to drw the inferences following the procedure of Snedecor nd Cochrn (1980). Confirmtion y reverse trnscription-polymerse chin rection (RT-PCR): In most cses, the disese ws dignosed on the sis of history, clinicl findings nd post-mortem chnges. Burs smples of three to four irds from flock were collected in 50% uffered glycerine. Such smples were collected from 40 IBDffected flocks. The smples were tested for the presence of IBDV nucleic cid y RT-PCR. The methodology used for the detection of IBDV ws essentilly the sme s descried y Mittl et l. (2005). Briefly, totl RNA ws extrcted from the smples using TRIzol method nd the extrcted RNA ws sujected to RT-PCR using VP2 gene specific primers. The mplified PCR products were gel electrophoresed nd nd of 643 p ws oserved in positive cses. RESULTS Occurrence of the disese: A totl of 483 flocks were ffected with IBD in the five districts of Hryn during the specified period of three yers. During the yer 2005-06, 8.75% of the totl flocks which were rought to the DI Ls hd IBD. These figures were 6.29 nd 2.27% for the yers 2006-07 nd 2007-08, respectively. Anlysis of the dt reveled tht 192, 211 nd 80 flocks were ffected during the yers 2005-06, 2006-07 nd 2007-08, respectively. A totl of 1,10,278 irds (4.5%) were ffected during three yer period with cumultive mortlity of 56,998 (2.3%) irds. Percent moridity vried from 4.1-4.9% while percent cumultive mortlity vried etween 2.0-2.5% during the period under study. Cse Ftlity Rte (CFR) due to the disese ws 51.7% (41.3-59.7% rnge) (Tle 1). The CFR ws significntly higher during 2006-07 s compred to tht in 2005-06. Though the CFR during 2006-07 ws higher thn tht in 2007-08, the difference ws not sttisticlly significnt (Tle 1). Temporl distriution: The disese ws recorded in ll qurters with mximum numer of IBD-ffected flocks (n = 145) in qurter A followed y qurters D (n = 137), B (n = 101) nd C (n = 100) (Tle 2). Percent moridity vried from 3.3-5.6%. It ws significntly higher in qurter B thn tht in qurter C. Though percent moridity in qurter B ws higher thn tht in qurters A nd D; the difference ws not sttisticlly significnt. Cumultive mortlity in ll the four qurters vried from 1.7-2.9%; it ws comprle in qurters A, B nd D (2.2-2.9%) nd the lowest in qurter C (1.7%). Though the CFR in qurter A ws higher thn tht in other qurters, however, the difference ws significnt only in comprison to qurter B (Tle 2). Effect of ge: The detils of IBD in different ge groups of roiler chicks re presented in Tle 3. The disese ws not recorded in chicks of less thn 10 dys of ge. Of the totl IBD-ffected flocks, 255 (52.8%) flocks hd irds of 21-30 dys of ge nd 160 (33.1%) hd irds of 31-40 dys of ge. Remining flocks hd irds of other ge groups (less thn 20 dys of ge nd more thn 40 dys of ge). Though percent moridity due to the disese ws higher in roiler chicks of 31-40 dys of ge thn the other ge groups, however, the difference ws significnt when compred to tht in irds of 41-50 dys of ge. Cumultive mortlity vried from 1.8-2.7% in ll ge groups. Though the cumultive mortlity ws higher in irds of 21-30 nd 31-40 dys of ge s compred to other ge groups; the difference ws not sttisticlly significnt. The CFR ws mximum (68.0%) in irds of 41-50 dys of ge while it vried from 46.5-56.4% in irds of other ge groups. The CFR in irds of 41-50 dys of ge ws significntly higher thn tht in irds of 11-20 nd 31-40 dys of ge (Tle 3). Effect of vccintion: Of the 483 IBD-ffected flocks, 334 flocks were vccinted ginst IBD while the remining 149 were not vccinted ginst IBD (Tle 4). Moridity nd cumultive mortlity were reltively higher in the unvccinted flocks (5.8 nd 2.6%, respectively) thn in the vccinted flocks (4.1 nd 2.3%, respectively). However, CFR ws comprtively higher in the vccinted flocks (55.1%) thn in the unvccinted flocks (44.2%); the difference ws not sttisticlly significnt (Tle 4). Of the 334 IBD vccinted flocks, the exct informtion regrding the type of vccine used ws provided y the owners of 267 flocks only; Intermedite (I), intermedite + plus (I ), Georgi (G) or MB strins were the commonly used vccines in roiler flocks in this region. The vccintion ws generlly crried out t 12-16 dys of ge vi drinking wter. 396
Tle 1: Yer wise distriution of infectious ursl disese in roiler flocks during July 2005-June 2008 Yer No. of flocks Flock size Moridity (%) Mortlity (%) CFR* (%) 2005-06 192 8,24,680 40,449 (4.9 ) 16,701 (2.0 ) 41.3 2006-07 211 11,27,510 46,318 (4.1 ) 27,634 (2.4 ) 59.7 2007-08 80 4,78,800 23,511 (4.9 ) 12,013 (2.5 ) 51.1 Totl 483 24,30,990 1,10,278 (4.5) 56,998 (2.3) 51.7 *Cse ftlity rte. Different superscripts within column indicte significnt difference t 5% level of proility Tle 2: Temporl distriution of infectious ursl disese in roiler flocks during July 2005-June 2008 Qurter No. of flocks Flock size Moridity (%) Mortlity (%) CFR* (%) July-Septemer (A) 145 6,68,830 23,609 (3.5 ) 14,582 (2.2 ) 61.8 Octoer-Decemer (B) 101 5,51,450 31,180 (5.6 ) 12,317 (2.2 ) 39.5 Jnury-Mrch (C) 100 4,39,650 14,568 (3.3 ) 7,549 (1.7 ) 51.8 April-June (D) 137 7,71,060 40,921 (5.3 ) 22,500 (2.9 ) 55.0 Totl 483 24,30,990 1,10,278 (4.5) 56,998 (2.3) 51.7 *Cse ftlity rte. Different superscripts within column indicte significnt difference t 5% level of proility Tle 3: Distriution of infectious ursl disese in different ge groups of roiler flocks during July 2005-June 2008 Age group (dys) No. of flocks (%) Flock size Moridity (%) Mortlity (%) CFR* (%) 11-20 49 (10.2) 2,71,800 10,444 (3.8 ) 4,870 (1.8 ) 46.6 21-30 255 (52.8) 12,89,340 52,305 (4.1 ) 29,496 (2.3 ) 56.4 31-40 160 (33.1) 7,89,350 45,014 (5.7 ) 20,921 (2.7 ) 46.5 41-50 19 (3.9) 80,500 2,515 (3.1 ) 1,711 (2.1 ) 68.0 Totl 483 24,30,990 1,10,278 (4.5) 56,998 (2.3) 51.7 *Cse ftlity rte. Different superscripts within column indicte significnt difference t 5% level of proility Tle 4: Vccintion sttus in infectious ursl disese ffected roiler flocks during July 2005-June 2008 Vccintion sttus No. of flocks (%) Flock size Moridity (%) Cumultive mortlity (%) CFR (%) Vccinted 334 (69.2) 18,29,040 75,480 (4.1 ) 41,618 (2.3 ) 55.1 Unvccinted 149 (30.8) 6,01,950 34,798 (5.8 ) 15,380 (2.6 ) 44.2 Totl 483 24,30,990 1,10,278 56,998 *Cse ftlity rte. Different superscripts within column indicte significnt difference t 5% level of proility Clinicl findings: In lmost ll IBD-ffected flocks, the symptoms of dullness, depression, norexi, ruffled fethers nd inility to move were oserved. There ws drstic decrese in feed nd wter intkes of the ffected irds. The ffected irds hd yellowish white or greenish yellow dirrhoe. The mortlity incresed with the progression of the disese, peked t third nd fourth dy nd then strted declining. The severity of the clinicl disese incresed s the disese progressed. Flock to flock vrition in severity of the disese ws, however, oserved. Post mortem findings: Gross pthologicl lesions in lmost ll IBD-ffected irds were recorded in urs of Fricius. The chnges included: edemtous nd turgid urs, presence of geltinous exudte round urs nd ursl hemorrhges. In ddition, hemorrhges on thigh nd pectorl muscles were lso oserved. These chnges were oserved only in cute form of the disese. However, in chronic form, the ursl chnges comprised of trophy nd/or presence of cheesy core inside the urs. The hemorrhges on thigh nd pectorl muscles were of milder degree in sucute form nd were mild or sent in chronic form. Of the 483 IBD-ffected flocks, 176 flocks hd hemorrhges t the junction of proventriculus nd gizzrd. Swollen kidneys nd enlrgement of liver were lso noticed in some cses; however, these findings were not consistent. RT-PCR: Of the ursl smples from 40 flocks, 38 were positive for IBDV y RT-PCR. In positive cses, nd of 643 p ws oserved. DISCUSSION The present study ws crried out to nlyze three yers retrospective dt in respect of IBD in roiler chickens. The dt nlysis my help us to understnd the epidemiology of the disese etter in the given geogrphicl re which would ultimtely e helpful in designing suitle prevention nd control strtegies t the frm level. This study is sed on dt otined from DI Ls for the pst three yers (2005-2008). During this period, 5.32% roiler chicken flocks were found ffected with IBD. Since ll the IBD-ffected flocks were not rought to the DI Ls for disese investigtion, the ctul numer of flocks ffected with IBD is not known, ut my e higher. The IBD hs een reported in roiler chicks from different countries (Anjum et l., 1993; Khurshid et l., 1993; Bekhit, 1997; Qureshi, 1999; Frooq et l., 2000; Trn et l., 2002; Anku, 2003). In this study, overll cumultive mortlity ws lower s compred to lredy pulished reports from Indi nd 397
rod (Anjum et l., 1993; Smi nd Bruh, 1997; ws lso higher in hot nd humid seson. High mortlity Trn et l., 2002; Anku, 2003; Jisnkr et l., 2003). in summer seson is expected ecuse of het s dy o Such vrition could e due to the fct tht the collection temperture shoots up to 46-47 C during the months of of dt ws done t one time point only without followup. As such, the mortlity (%) in this study my not reflect mortlity would e ovious due to comined effects of My nd June. At such high tempertures, higher ctul mortlity due to the IBD nd s mtter of fct it het nd IBDV. Likewise, immeditely fter rins, there could e on higher side. Follow up studies re therefore, is high humidity in the environment which my lso needed to determine the exct moridity nd/or mortlity sustntilly increse the mortlity rte. However, more rtes. Higher CFR (51.7%) in this study my e due to comprehensive dt re required for sustntiting cute form of the disese. The results of the present sesonl occurrence of the disese nd/or mortlity. study re consistent with the previous study in the Contrry to our oservtions, Frooq et l. (2003) in Hryn stte y Jindl et l. (2004) in which totl of Kshmir re of Pkistn reported higher losses in 8.89% flocks were ffected with IBD during nine yer winter thn in spring. Jisnkr et l. (2003) found period with moridity, cumultive mortlity nd cse mximum incidence in winter (43.93%) followed y ftlity rte of 5.9, 3.6 nd 61.43%, respectively. summer (39.74%) nd monsoon (16.74%). The clinicl findings nd post-mortem lesions oserved The occurrence of the disese ws more in the irds of in this study re consistent with those reported y erlier 21-40 dys of ge indicting tht irds in this ge group workers (Cosgrove, 1962; Mohnty et l., 1971; re more susceptile to IBD. Bekhit (1997) nd Anku Rjeswr nd Mohn, 1992; Sh et l., 1995; Qureshi, (2003) lso reported tht irds of 3-6 weeks of ge re 1999; Trn et l., 2002; Zeleke et l., 2005). We more susceptile to the disese. Khurshid et l. (1993) oserved differences in severity of the disese sed on oserved tht incidence of IBD in roiler chicks ws the clinicl nd necropsy findings nd CFR. Such mximum t 4th week of ge followed y 5th, 3rd nd 6th weeks. Similr oservtions with regrds to occurrence differences could e ttriuted to numer of fctors of disese were mde y Smi nd Bruh (1997), such s type of virus involved, ge of the irds, Jisnkr et l. (2003), Jindl et l. (2004) nd Zeleke et vccintion sttus, concurrent infections, helth sttus of l. (2005). The occurrence of the disese in older irds irds, nutritionl sttus, seson etc. We oserved tht in my e correlted well with mternl ntiody titers nd some of the ffected flocks there ws history of IBD in vccintion sttus of irds. Sufficient mternl previous flock. It seems tht mjority of the poultry ntiodies my protect irds from the disese for first frmers re smll nd mrginl nd re not fully wre two weeks. If irds receive pproprite vccintion of the role of iosecurity in disese prevention nd during this period, chnces of outreks during growing control. Improper clening of the sheds, keeping used period would e reduced. However, improper litter ner frms nd frequent movement of personnel vccintion would mke irds susceptile to IBD t might hve helped in spred of the disese from flock to lter stge. flock nd frm to frm. To study the impct of vccintion on disese Though the disese ws recorded throughout the yer, occurrence, we nlyzed the dt with regrds to however, the occurrence ws more in winter seson disese nd vccintion in flocks. Of the totl IBDffected flocks, out 70% flocks were those in which followed y riny nd summer seson. These findings hve the support of Qureshi (1999) who on the sis of prophylctic IBD vccintion ws crried out nd the four yer dt reported higher occurrence of disese in remining 30% were unvccinted flocks. The IBD prts of Pkistn during winter months compred to outreks in vccinted flocks hve lso een recorded summer months. Though the occurrence of disese in y Anku (2003) in Southern Ghn. Previously in this study ws found on higher side in winter seson, yet Hryn, Jindl et l. (2004) reported tht out 59% of moridity nd cumultive mortlity were comprtively the flocks were vccinted in which IBD ws recorded. higher in summer months. The exct reson for higher Gupt et l. (2006) hve lso reported outreks in occurrence in winter seson is not fully understood. vccinted flocks in Punj nd Hryn sttes. However, it my e due to doption of indequte Moridity nd cumultive mortlity due to IBD in this iosecurity mesures including the indequte nd study were comprtively higher in unvccinted flocks improper disinfection of poultry sheds due to hrsh cold thn in the vccinted ones. Anjum et l. (1993) nd conditions during winter seson nd keeping of sheds Frooq et l. (2000) lso reported tht the severity of ir tight so s to mintin the temperture s most of the disese ws more in unvccinted roiler flocks. commercil roiler frms in this region re not Intermedite or intermedite plus vccines (oth live environmentlly controlled. This could result in erosol vccines) of different mnufcturers re generlly used genertion of IBDV due to close contct therey leding for vccintion ginst IBD in roiler chicks in this to mintennce of lrge mount of the virus t the frm region. The vccintion is generlly crried out t 12-16 premises. In the present study, the cumultive mortlity dys of ge vi drinking wter. These vccines though 398
elicit protection ginst IBD ut pper mildly Asrni, R.K., D. Krishnswmy, G. Nrng, M.U. Khrole immunosuppressive prticulrly the intermedite plus nd S. Krishnswmy, 1993. Investigtion on vccine. A numer of predisposing fctors such s prevlence nd immunologicl spects of overcrowding, poorly constructed rooder house nd poor ventiltion in the frm my e responsile for disese to occur in the vccinted flocks. Poor vccintion prctices, improper hndling of the vccine, rek in cold chin during trnsport nd t the frm, use of chlorinted wter during vccintion, exposing vccine virus to outside environment for longer durtion, concurrent infection(s) nd no or low mternl ntiody levels in chicks re other potent fctors tht my contriute to the occurrence of disese in the vccinted flocks. Most of the poultry frmers in this region re not fully wre out proper hndling of vccines. More importntly, the role of Very Virulent (vv) strins of IBDV in cusing the disese inspite of vccintion cnnot e ruled out. The vv strins emerged during the yer 1992 in Indi were cple of reking the mternl ntiodies rrier. In such sitution, the disese cn e oserved even in flock tht hs een vccinted using good vccintion prctices. The vv strins of IBD hve een reported from mny countries including Indi th infectious ursl disese. In: Proc. of X World Veterinry Poultry Assocition Congress, Sydney (Austrli), pp: 159. Bekhit, A.B.A., 1997. Highly virulent form of infectious ursl disese in Egypt: Some epidemiologicl oservtions. Indin J. Anim. Sci., 67: 363-366. Chettle, N., J.C. Sturt nd P.J. Wyeth, 1989. Outrek of virulent infectious ursl disese in Est Angli. Vet. Rec.,125: 271-272. Cosgrove, A.S., 1962. An pprently new disese of chicken vin nephrosis. Avin Dis., 9: 385-389. Frooq, M., F.R. Durrni, N. Imrn nd Z. Durrni, 2003. Prevlence nd economic losses due to infectious ursl disese in roilers in Mirpur nd Koti districts of Kshmir. Int. J. Poult. Sci., 2: 267-270. Frooq, M., F.R. Durrni, S. Fisl, A. Asghr nd A. Khurshid, 2000. Incidence of infectious ursl disese mong irds sumitted to dignostic lortory in NWFP, Pkistn. Pk. Vet. J., 20: 77-80. (Rmdss et l., 2003; Shmsr et l., 2006; Mrtin et Fernndes, M.J., I.C. Simoni, M.G. Vogel, R. Hrkv, l., 2007; Sreedevi nd Jckwood, 2007; Junej et l., E.B. Rivs, M.B. Oliveir, A.M. Knshiro, E.N. 2008; Fernndes et l., 2009). We hve previously Tessri, N.M. Gm nd C.W. Arns, 2009. Moleculr reported the existence of vv strins of IBD in commercil chrcteriztion of Brzilin infectious ursl roiler chickens in Hryn tht were distinct from disese virus isolted from 1997-2005. Avin Dis., vvibdvs from other prts of Indi sed on VP2 gene 53: 449-454. phylogeny (Mittl et l., 2006). Recently, we hve lso Gupt, A., P.C. Shrm nd M.S. Oeroi, 2006. chrcterized some more IBDVs nd found them to e Pthogenicity study of infectious ursl disese. very virulent in nture (Mor, unpulished dt). Indin J. Vet. Res., 15: 38-41. Prevlence of v v strins of IBDV in this region lso Jisnkr, S., A.M. Dinkrn nd K. Krunkrn, 2003. wrrnts the need for strict iosecurity mesures t the Retrospective studies on the pttern of virl frm level. diseses in poultry in Nmkkl. Indin J. Poult. Thus, it cn e concluded from this study tht infectious Sci., 38: 142-144. ursl disese is prevlent throughout the yer in Jindl, N., N.K. Mhjn, D. Mittl, S.L. Gupt nd R.S. commercil roiler chicken flocks in the stte of Hryn Khokhr, 2004. Some epidemiologicl studies on oth in unvccinted s well s vccinted flocks infectious ursl disese in roiler chickens in resulting in huge economic losses to the frmers. There prts of Hryn, Indi. Int. J. Poult. Sci., 3: 478-482. is need to educte frmers to dopt strict iosecurity mesures nd vccinte their roiler chicken flocks Junej, S.S., Rmneek, D. Dek, M.S. Oeroi nd A. regulrly nd properly ginst this disese to minimize Singh, 2008. Moleculr chrcteriztion of field the losses. Further, regulr surveillnce nd isoltes nd vccine strins of infectious ursl chrcteriztion of field strins would help in chlking disese virus. Comp. Immunol. Microiol. Infect. out nd re-evluting control strtegies from time to Dis., 31: 11-23. time. Khurshid, A., A. Njm, R.S. Monem, K. Ahmd, N. Arshd nd S.M. Rijvi, 1993. Incidence of infectious REFERENCES Anjum, A.D., S. Hsrn nd G.S. Ari, 1993. Infectious ursl disese in chickens in Pkistn. Pk. Vet. J., 13: 54-58. Anku, G.G., 2003. Gumoro hmpers efforts to improve nutrition of Ghn s growing popultion. Poult. Int., ursl disese (Gumoro) in roilers. Proc. Pkistn Cong. Zool., 13: 501-504. Mrtin, A.M., F. Fllcr, I. Brieri, G. Tosi, G. Rivlln, N. Eterrdossi, R. Ceruti nd P. Cordioli, 2007. Genetic nd ntigenic chrcteriztion of infectious ursl disese viruses isolted in Itly during the 42: 32-35. period 2002-2005. Avin Dis., 51: 863-872. 399
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