Đánh Giá Hiệu Lực Của Vacxin Amervac PRRS Đối Với Chủng Virus PRRS Gây Bệnh Động Lực Cao ở Việt Nam

KHOA HOC KY THUAT T H O Y TAP XXI SO 1 - 2014

i0Sl)iln cifu fefipa toe DANH GlA HIEU llfC CUA UACXIN AMERVAC PRRS

001 VOll CHUNG VIRUS PRRS GAY RENH DONG llfC CAO A VIET NAM To Long Thanh', Nguyen Hoang Bang', Tdng HS-u Hien',

Bach Qudc Thdng', Daniel Torrent^

TOM TAT Dung vacxin AMERVAC PRRS khdo nghiem tren Ion k6t qua cho thiy nhu sau: Vacxin nhu^c

doc AMERVAC PRRS do hSng Laboratorios HIPRA, S.A san xuit dam bao an toan khi su dung. Vims vacxin khong truyen ngang tir 16 thi nghiem sang 16 doi chung va c6 tac dung kich thich sinh dap ung mien dich khi Ion bi nhiem virus cuong doc va cho dap iing mien dich se manh hon. Dap ung mien dich do vacxin tao ra co tac dung lam giam muc dp tram trpng ciia benh khi cong voi 2 chung virus PRRS cuong doc ciia Viet Nam thong qua kiem tra benh tich dai the va vi the tren cac ca quan npi tang, dac biet la a phoi. Lo diing vacxin ciing tang trpng hon so voi 16 khong dimg vacxin khi cong cudng dpe. Dap ung mien dich co dupc nha vacxin da loai bo hoan toan virus trong ca the Ipn v^o khoang 2-3 tuan sau khi bi nhiem.

Tir khoa: Lan, PRRS, vacxin PRRS, khao nghiem, cong cuong dpe

Evaluation of efficiency of Amervac PRRS vaccine for the High virulent, pathologenic virus strain in Viet Nam

To Long Thanh, Nguyen Hoang Dang, Tong Huu Hien, Bach Quoc Thang, Daniel Torrents

SUMI\/IARY Live AMERVAC PRRS vaccine produced by HIPRA Laboratory, SA (Spain) was used for

testing on pigs raising in Viet Nam The tested result indicated that this vaccine was safe in use. Vaccine virus did not transmit horizontally from experimental pigs to control pigs and had the effect in inducing immune response at higher level when the pig was Infected with challenge virus. Immune response induced by vaccine had the effect in reducing the serious level of disease when challenge with 2 virus strains of Viet Nam. This result showed clearly when testing the gross and histobiological lesions in internal organs (particularly is lung). The vaccinated pigs also increased higher body weight compared to the control pigs when applying challenge test. Immune response induced by vaccinating AMERVAC PRRS vaccine had removed the entire of virus In pigs in 2-3 weeks after pigs were infected with PRRS.

Key words: Pig, PRRS, PRRS vaccine, Testing, Challenge test

' Trung tam chan doan thii y Trung uong ' Cong ly thii y xanh ^ Cong ty Hipra S.A, Amer Tay Ban Nha

KHOA HOC KY THUAT THU Y TAP XXI SO 1 - 2014

I. DAT VAN DE Hpi chung roi loan sinh san va ho hap ciia

Ign (PRRS) th8 doc luc cao do virus PRRS (PRRSV) thuoc genotype II gay ra. The benh nay xuat hien tai Viet Nam nam 2007 va da gay nen nhung t6n thSt kinh t6 nang ne cho nhirng nguai chan nuoi lan trong nhiing nam sau do.

Ve lich sir, PRRSV genotype 1 xuat hien lan dSu tien tai Ha Lan nam 1986, gay nen PRRS the kinh din hay con gpi la PRRS the doc luc thap da tham nhap vao Viet Nam tir cuoi nam 1996 dau nam 1997. Nhirng nam sau do, mpt s6 loai vacxin, trong do c6 vacxin AMERVAC PRRS da dupc dang ky sir dung tai Viet Nam. Vacxin AMERVAC PRRS la vacxin genotype I da duac su dung ke tir khi dang ky tu nam 2005 cho den nay.

Viec sir dung rpng rai vacxin AMERVAC PRRS (genotype I) d phong ch6ng PRRS thd doc luc cao (genotype II) tai cac dia phuang doi hoi viec danh gia kha nang bao hp ciia loai vacxin nay vai chung PRRSV the doc luc cao dang liru hanh tai Viet Nam. Day cung chinh la muc dich cua bai bao nay.

IL NGUYEN LIEU VA PHU'CTNG PHAP NGHIEN ClTU 2.1. Nguyfin v3t lieu

- Dpng vat thi nghiem: Chpn 16 lan con 4 tuan tuoi, khoe manh va am tinh vdi virus PRRS, khong hem bdt ky mot loai vacxin phong PRRS nao. Lan duac nuoi va tien hanh thuc nghiem tai Trung tam chan doan thii y TW.

- Vacxin nhupc doc AMERVAC PRRS do hang Laboratorios HIPRA, S.A san xuat, dung cho lan 3 tuan tuoi tro len.

Virus cuong doc gom 2 chung: Chiing virus PRRS so 21 do cong ty HIPRA cung cap CO ngu6n goe tir Viet Nam nam 2008 va chiing vims PRRS ky hieu VN07196 cua Trung tam chan doan thii y TW.

- Kit ELlSAphat hien khang thi PRRS

- Kit chiet tach Qiagen RNeasy, kit nhan gen Invitrogen SSIII One-step qRT-PCR system (Cat 11732-020).

- Cac hoa chat va nguyen lieu can thiet khac.

2.2. Phucmg ph^p nghien ciru - Bo tri thi nghiem:

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KHOA HQC K? THUAT THO Y TAP XXI S6 1 - 2014

Theo d5i Ipn sau khi tidm vacxin d^ danh gia tinh an toan, bieu hi?n iam sang \k bi^n ddi than nhi?t tir ngay diij 32 dgn 46. Can Ipn, theo d5i trpng lupng vao cac ngay thir 0, 32, 39, 36 va 55. LSy mau vao cac ngay thu 29,35, 39,42,46 va 55 d6 xet nghi?m ham lupng virus huy6t. Xet nghi?m khang th6 khang virus PRRS vao cac ngay thu 0, 29 va 55. M6 kham kigm tra benh tich, cham diem phoi tit ca Ipn vao ngay thijr 55.

2.3. Cdc phinmg phdp xit nghl|in - Diing phuang phdp ELISA va IPMA d6

kiim tra khang thS.

- Dimg phuang phap Real-time RT-PCR d8 kiem tra virus.

- Dung phuang phap m6 kham va lam tiSu bdn vi thi de kiem tra b8nh tich dai th8 va vi thi.

- Phuang phdp ddnh gia an toan ciia vacxin: Theo doi mpt tudn sau khi tiem vacxin, nlu khong CO phdn irng bat thuong nhu: mSt moi, chdn ho^c b6 dn, tdng than nhi?t vd cdc dau hieu b?nh 1^ khdc Id an toan.

- Phuang phdp ddnh gid hi$u luc ciia vacxin: Hi^n tai, Vi?t Nam chua c6 chting virus PRRS c6 khd ndng gay chit 100% Ipn man cam nen vi^c ddnh gid hi?u qua cua vacxin PRRS can phai kit hpp giiJa chi d6u bao hp sau khi cong

cuong dpe voi cdc chi tieu khac bao g6m: Bilu hien lam sang, tang than nhiet, benh dch dai the, vi the a ph6i, tinh trang nhilm virus mau va kiem tra dap irng mien dich bdng phucmg phdp huylt thanh hoc.

I I I . K E T Q U A VA T H A O L U A N 3.1 Ket qua theo doi an tokn sau khi tiSm vacxin

Theo doi mot tuan sau khi tiem vacxin 8 Ipn khdng thay co bat ky cac phan img bdt thudng nhu: met moi, chdn hoac bo an, tang than nhiet va cac dau hieu benh Iy. Nhu vay, cho thdy vacxin AMERVAC PRRS la an toan.

3.2 Ket qud theo doi sau khi cong c u ^ g d$c 3.2.1. Bieu hien lam sang va thdn nhi^t sau khi cong cir&ng dpe

Lpn sau khi cong bang 2 loai virus PRRS vao ngay 32. Tir ngay 33 d6n ngay 46 theo doi nhiet d6 vd cac bieu hien Iam sang va cham diem. K6t qud theo doi Iam sang dupe the hien trenbiludo lava lb. Nhan xet ve lam sang: * Cong c u ^ g d$c v6i virus PRRS 21

- , c

2,0

1 1.5

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^ 1

/ X \ / ^^ *^ ^ *\ / ,y^^^ \ "\'"

J y* \ ^

- ^ V ) t 1 --DC-1

^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ .^ ^ .^

Bieu do la. Bieu hi^n tam sdng cua Iqn dirpv cong virus PRRS 21


- Sau khi nhilm virus PRRS 21, lpn 16 1 (VX-1) va 16 2 (DC-1) bit ddu co nhimg bilu hien ddu tien sau 1-2 ngay. Trieu chirag thudng thdy Id lpn giam nhanh nhen, an it hon miic binh thudng, lpn ddi chung an it han lpn tiem vacxin.

- Trieu chung tien triln nhanh va nang han d nhung Ion ddi chiing. Tir 4-8 ngay sau khi nhilm virus Id giai doan b?nh n$ng nhat. cham chap, it van ddng va gidm dn. Mdt s6 cd trieu chung thd nang nhpc hoac tim tdi d tai. Co 1 lpn (s6 11) d Id ddi chung cd bieu hien benh nang han cac con cdn lai trong id, the trang rat met mdi, thd ddc "kieu chd ngdi" vd co hien tupng

tim tai. Ddi vdi nhung lpn Id vacxin, cac tri?u chung tren khdng bieu hien ro va thudng chi keo dai 1-2 ngdy, khdng lau nhu Ion ddi chumg.

- Tir ngay 8-10 sau khi cdng (ngay thu 40 ttd di) cac trieu chiing bSnh giam ddn, Ion nhanh nhen ban, an khde. Nhdm Ipn vacxin den ngdy thu 42 da khdng con the hien trieu chiing. Nhom lpn ddi chumg phuc hdi cham hon 3-4 ngdy. Rieng Ion sd 11 thudc 16 ddi chumg bieu hien benh ngay mdt nang va chet vdo ngdy thii 44 (ngdy 12 sau cdng). * Cong cudng doc vdi virus PRRS VN07196

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Nhdn xet ve thdn nhiet:

-vx-2 -DC-2

-^ 4- -^ ^ -"' J ^ ^ ^ ; ^ ^ , ^ ^ ^ .^ .^ .^ .^ ^ ^ .

[3- I? ftp- li^ ^. ^ ^ ^ .^.

Bieu dd 2a. Diin bien than nhiet cua lan du^ giy nhi$m virus PRRS 21

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1 ' 40.0 c

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- . - V X - 1 - . - B C - 1

Bleu do 2b. Dien biin thSn nhi$t ciia /pn {fut>v giy nhiem virus PRRS VN07196

Bieu do 2a vd 2b d tr8n th6 hi8n dien bien thdn nhi?t cua lpn sau khi nhiem 2 loai virus PRRS.

- Than nhiet trung binh bat ddu tang hi ngdy thii 33 (virus PRRS 21) bic la sau khi cdng cudng dpe 1 ngdy.

- Lpn s6t cao nhdt vdo giai doan ngay thii 35-41 vdi than nhi$t trung binh co liic len tdi

tren 41''C, ddc biet la cdc Ion d 2 Id ddi chumg. Tren bieu dd cho thdy virus PRRS 21 gay sdt vdi thdi gian nhanh hon (sau 3 ngdy, than nhiet trung binh tren 40C); tuy nhien virus VN07196 lai gay sdt dai han (den ngay thii 44).

- Qud trinh sdt gidm ddn tir ngdy thii 41-42 vd lpn lai trd ve miic than nhiet binh thudng. Rieng lpn sd 11 (Id 2) va lpn sd 8 (16 4) cd hien tupng giam than nhiet xudng dudi 38''C va chet.


3.2.2. Trang thdi virus huyit (Xem bdng 1)

Bang 1. Mipc do virus huyet tren Ion (tinh trung binh) L6

VX-1 BC-1 VX-2 DC-2

Ngay 29 40,00 40,00 40,00 40,00

Ngay 35 29,61 26,69 27,95 26,01

Ngay 39 27,15 24,29 26,93 24,32

Ngay 42 29,98 26,55 28,76 26,20

Ngiy 46 34,99 32,39 33,16 33,75

NgjiySS 37,72 37,23 36,63 33,65

(Ghi chit: Cl la ngudng vong cUa phdn img Realtime RT-PCR, ddnh gia luong virus cao hay thdp, Cl cang thdp luang virus cdng nhieu va nguac lai. Thong thudng phdn iing RRTPCR co Ct < 35 la duong tinh Coi kit qud dm tinh virus huyet co gid tri Ct = 40)

Bieu do 3. Mux: do virus huyet

- Trudc khi cdng cudng doc (ngdy thir 29), khdng phdt hien thdy virus PRRS trong huylt thanh tdt cd lpn d cac 16.

- C6ng cudng dpe d thdi dilm ngdy thii 32. Sau dd lay mdu vao cdc ngdy thii 35, 39,42, 46 va 55 de kiem tra mire dp virus huylt. Kit qud the hien tren bang va bieu do cho thay virus xudt hien trong huyet thanh lpn dat cao nhdt vdo giai doan ngay thu 35-42 (tiic la ngay 3-10 sau khi

gdy nhilm) va giam dan d nhung ngay tiep theo. - Tai ciing thdi dilm, lupng virus huyet cr

Ion thudc cdc Id ddi chiing cao han Ipn d cdc 16 vacxin tli 4-8 ldn (chenh lech 2-3 Ct).

- Den ngdy thii 55 khi ket thiic thi nghi?m, vdn cdn 1 lupng nhd virus phat hien dupc trong huyet thanh Ign ddi chiing duac c6ng virus VN07196. Cac nhom khdc khdng cdn virus trong huyet thanh.

KHOA HOC KY THUAT THU Y TAP XXI S6 1 - 2014

3.2.3. Ddp umg miSn djch (Xem bdng 2 vd 3)

Bang 2. Ket qua kiem tra hieu gia khang the blng phu'tyng phap ELISA

Lo

2

4

Virus CCD

PRRS 21

PRRS VN 07196

S6tai

2 4 5 13 9 10 11 12 1 3 18 19 8 14 15

Ngay 0 S/P

0,041943 0,335541 0,311258 0,280353 0,19426

0,328918 0,00662 0,015453 0,07064 0,00662 0,01987 0,011038 0,03532 0,04636 0,02649 0,00662

KQ Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg

Ngay 29 S/P

2,27807 0,0241 3,20321 3,59626 0,0214

0 0,03476 0,00802 2,63636 0,0187

2,29412 2,10695 0,03476 0,0053

0,04278

0,05348

KQ Pos Neg Pos Pos Neg Neg Neg Neg Pos Neg Pos Pos Neg Neg Neg Neg

Ngay 55 S/P

2,3246 2,09607

2,538574 2,11936 1,41048

1,918486

KQ Pos Pos Pos Pos Pos Pos

LON C H T

1,606987 2,010189 1,416303 2,525473 1,570597

Pos Pos Pos Pos Pos

LON C H E T

1,770015 1,390102

1,528384

Pos Pos Pos

Bdng 3. Ket qua kiem tra hieu gia khang the bang phuxyng phap IPMA

Lo

1

4

Vims cong

PRRS 21

PRI^S VN 07196

So tai 2 4 5 13 9 10 11 12 1 3 18 19 8 14 15 16

NgayO Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg Neg

Ngay 29 640 Neg

1/2560 1/5120

Neg Neg Neg Neg

1/1280 Neg

>1/640 1/640 Neg Neg Neg Neg

Ngay 55 1/1280 1/640 1/1280 1/640 1/320 1/640

LON C H E T

1/640 1/640 1/320 1/1280 1/320

LgN CH^T 1/640 1/320 1/320


Nhdn xet: - Trudc khi tiem vacxin vdo ngay 0, tat cd 16

Ion ciia 4 Id deu dm tinh vai khang the khang virus PRRS (ca 2 phuang phdp xet nghiem ELISA va IPMA)

- Sau khi tiem vacxin Amervac cho 2 Id dupc 29 ngdy thay rang cd 6/8 con cd khang thi khdng virus PRRS. Ty le S/P trung binh vd hieu gia khang the trung binh 16 1 cao hon 16 3. Khdng phdt hien dupc khang the khang virus PRRS tren Ion cua 2 Id khdng tiem vacxin { am tinh). Dieu nay chung td vacxin khong truyln ngang tir 16 thi nghiem sang 16 doi chirng.

- Sau khi c6ng cudng doc 23 ngay (tire la

ngay thir 55) cd 4 16 deu cd khang the d 14 lpn sdng sdt (mdi 16 d6i chiing chet 1/4 lpn). Ty 1^ S/P trung binh vd hi$u gia khang the trung binh d 2 Id tiem vacxin cao hon 2 Id ddi chiing Co the nhdn thdy su chuyen biSn ddp iing miln dich tao khdng the thdng qua cac ket qua ciia phuang phdp ELISA va IPMA sau khi tiem vacxin va sau khi cdng cudng ddc.

Dilu nay chung to vi|c sir dung vacxin da kich thich hinh thdnh dap ung miln dich ddc hiu. Ddp iing miln dich dupc thiic day va ham lupng khdng the tdng cao 6 lpn dupc tiem vacxin nhd phdn iing hdi lic sau khi lpn dupc cdng cudng doc.

3.2.4, Tdng trong (Xem bdng 4).

Bang 4. Theo doi trong lyvng trung binh cua \tyt\ 4 Id thi nghiem

L6

Lo 1 (VX) Lo 2 (DC) L6 3 (VX) Lo 4 (DC)

Ttieo doi trijng lu'o'ng TB (Itg) NgayO

6,1 5,9 6,3 6,2

Ngay 32 (CCB) 14,4 14,3 14,5 14,6

Ngay 39 16,5 14,8 16,9 15,2

Ngay 46 19,2 16,1 19,8 16,6

Ngiy 55 22,8 19,0 23,5 19,6

- O giai doan sau khi tiem vacxin (ngay 0 den ngdy 32), miic do tang trpng Ipm la tuong duong nhau giira cdc 16. Dieu nay cho thdy vacxin kh6ng dnh hudng tdi qua trinh tang trpng d nhiing lpn dupc tiem.

- Sau khi cdng cudng ddc (ngay thii 32 trd dl), miic dp tang trpng giam hon so vdi tnrdc . Sau 23 ngay cdng virus PRRS 21, Id 1 tang 8,4 kg, 16 2 tang 4,7 kg, nhu vay 16 dung vacxin tang trpng cao ban Id ddi chimg la 3,7 kg.

- Sau 23 ngdy cong virus PRRS VN 07196 16 3 tang 9 kg, cdn Id 4 tang 4,9 kg, nhu v?y 16 dung vacxin tang trpng cao hon 16 d6i chimg la 4,1 kg.

L6 dung vacxin AMERVAC PRRS tSng trong tdt h

KHOA HOC KY THUAT THU Y T A P XXI SO 1 - 2014

3.2.5. Bfnh tich dtfi the vd vi thi &ph6i

Virus PRRS 21

Virus VN07196

3ang 5. Cham di^m b^nh tich phoi khi

Ld 1 - vacxin So 2 3+

864 3+

So 5 I t

So 13 3*

Diem trung binii io = 2,50 Lo 3 - vacxin

S61 2+

So 3 2+

So 18 2+

So 19 1 +

Diem trung binii io = 1,75

mo Itham

Lo 2 - doi chijng So 9 3->

So 10 2+

s6ii 3+

S6l2 2+

Diem tnjng binh io = 2,50 Lo 4 - d6i clii>ng

S6 8 2+

S6 l4 1 +

S6l5 3+

S6l6 2+

Diem trung binh 16 = 2,00

Nhdn xet benh tich dai the:

Sau khi cong cudng doc, Ion ciia tdt cd cdc 16 thi nghiem va ddi chiing deu cd cac benh tich d?i the viem d phdi. B6nh tich chu yeu Id hien tupng viem ke, xuat huyet va khi thung, xay ra d tat ca cac thiiy ph6i. Mpt sd Ion ddi

chung cd hien tupng teo thiiy phdi (nhdt Id thiiy tim). Cac hach khi phe qudn bj viem, sung vd xudt huyet, xudt hien ca d Id vacxin va Id ddi chiing. Benh tich dai th o phdi ciia Ign Id tiem vacxin cd bieu hien viem nhg hon so v ^ Ign cua Id doi chirng.

Ld 2 - Doi chLPng cong PRRS 21

PhSl viem ke, xuit huyil Hach khi phe quan sung, xuit huySt

Lo 1 -Vacxin cong PRRS 21

1 Phdi xuk huyet nh? Hach mitig treo ruQt binh thucmg

KHOA HOC KY THUAT THO Y TAP XXI SO 1 - 2014

L6 4 - Ooi chirng cong VN 07196

Phoi viem ke, xuat huyet Hach khi phe quan sung, phii

Lo 3 - Vacxin cong VN 07196

I"*

Qj Hach mang treo rudt binh thuung

Nhdn xet benh tich vi the: - Benh tich vi the cac 16 doi chiing: Ld 2

(c6ng vims PRRS 21) vd Id 4 (cdng vims PRRS VN 07196) cd benh tich nang phii ne mang phdi, vdch ngan gian rpng, Idng phe quan chiia dich ri viem va tl bdo viem, hinh thanh huyet khdi, viem mach tang sinh, vach phi nang day tang sinh te bao phi nang loai 2. Lo 2 cd bieu hien benh tich ndng ne hem 16 4.

- Benh tich vi the cdc 16 vx: L6 1 (cdng virus PRRS 21) va 16 3 (cdng virus PRRS - VN 07196)

cdu tnic phdi cac diiiy vdn cdn nguyen ven, mang phdi, vach ngan ro rdng, vdch phe nang mong, cau tnic tiii khi rd rang.

Nhu vdy, khi cdng virus cudng doc PRRS, 16 dupc tiem phong vacxin Amervac cd tac dung bao ve phdi va cac ca quan khdc nhu lach, h?ch, amidan khdng bi virus tdn cdng, con Id khong tiem phdng, phoi vd cdc ca quan ndi tang deu co biln ddi benh tich vi thi ndng do su xdm nhap cua virus PRRS.


Mpt so hinh anh benh tich vi thg;

Lo 2 B/C (cdng virus PRRS 21)

: ~ ' - i 5 . ^ V

KHOA HOC KT THUAT THI? Y TAP XXI S6 1 - 2014

L6 3 VX (cong virus PRRS -VN 07196)

Phoi: Binh thuxyng

IV. KET LUAN

Dua vao cac ket qua thuc nghiem neu tren, CO the riit ra cdc ket luan nhu sau :

- Vacxin nhuac doc AMERVAC PRRS do hang Laboratorios HIPRA, S.A san xuat dam bao an todn khi sir dung tiem phdng cho lan.

- Virus vacxin khdng truyen ngang tir 16 thi nghiem sang Id ddi chimg va cd tdc dung kich thich sinh dap ung mien dich khi Ian bi nhiem virus cudng ddc (hodc c6ng cudng doc) dap ung mien dich se manh ban.

- Dap ling mien dich do vacxin tao ra cd tac dung 1dm giam miic dp tram trpng cua benh thdng qua kiem tra benh tich dai the vd vi the tren cac ca quan npi tang, dac biet la ph6i cua lpn sau khi bi nhiem virus cudng doc PRRS.

- Lo diing vacxin AMERVAC PRRS tang trpng ban so vdi Id khdng dimg vacxin khi cdng virus PRRS cuong ddc.

- Dap ling mien dich co dupc nhd vacxin da loai bd hoan todn virus trong ca the Ipn vao khodng 2-3 tudn sau khi bi nhilm. Lpn dugc tiem vacxin, khi bi nhiem virut cudng doc se khdng dao thai virus cudng ddc ra mdi tnidng xung quanh.

TAI LIEU T H A M K H A O 1. Tian et al. 2007. PloS ONE 2: e526. 2. Li et al. 2007. Vet J. 174: 577-584.

3. Nam et al. 2009. Arch Viroi 154: 629-638. 4. Amonsinetal. 2009. f77-o/y. 16: 143. 5. RocaM. etal. 2012. Vet J. 193: 92-96

Nhan ngay 3.10.2013 Phdn bien 3.11.2013

Documents

Đánh Giá Hiệu Lực Của Vacxin Amervac PRRS Đối Với Chủng Virus PRRS Gây Bệnh Động Lực Cao ở Việt Nam