trung la co sd khoa hoc cho viec nghien ciiu che tao vacxin phdng benh cau trung cho ga-
4 .2 . V a c x in p h d n g ben h cau tr u n g ga
Theo Chapman (1996), hien nay viec nghien ciiu che tao va sir dung vacxin cau triing theo hai hudng chu ye'u:
- Nghien cuu che tao va sir dung vacxin cau trung sdng:
Thanh ph£n vacxin la cac O ocyst cau triing da duoc xir ly theo yeu cau cdng nghe. Nhung loai vacxin song da duoc sir dung rong rai d Viet Nam nhu: Coccivac - B (My), Paracox (Canada).... Co che' quan trong la khi dua vacxin vao co the ga, O ocyst c<iu triing trong vacxin khong gay benh cho ga, ma su tdn tai cua chung se kfch thfch co the ga san sinh khang the chdng lai su xam nhap cua cau trimg gay benh tu nhien. Tuy nhien, mien dich nay khdng ben viing. Khi cau triing vacxin khong cdn trong co th i ga, chi sau mot thdi gian ngan, ga khdng con sue mien dich va lai cd kha nang cam nhilm cau triing gay benh tu nhien.
- Nghien ciiu che' tao va sir dung vacxin che't (vacxin vd hoat)
Vacxin loai nay chi chiia mot thanh phan cua O ocyst, dai dien tfnh khang nguyen cua c£u triing. Dd la mot protein duoc chiet xua't ra tir O ocyst c£u triing loai Eimeria maxima d giai doan san sinh bao tir, duoc che dudi dang nhu hoa. Vacxin duoc sir dung bang cach tiem cho ga bd me giai doan hau bi trudc khi de, nham tao ra khang the dac hieu d mure cao. Co the ga san sinh khang the chong lai cac loai c^u triing E. tenella, E. m axim a, E. acervulina. Vacxin nay cung cd kha nang tao ra mien dich thu dong cho ga con sinh ra tir ga me duoc tiem phong vacxin.
Pham Van Chuc va cs (1991) da nghien ciiu va san xua't vacxin phong benh cau triing ga bang phuong phap chieu xa gama, budc dau cd ket qua tot. Shirley va cs (1995)
da nghien curu che tao vacxin phong benh c£u triing cho ga, ket qua thay ga co mien dich voi cau trung, tuy nhien thoi gian mien dich khong dai.
Theo Phan Luc va cs (1999), sir dung vacxin Coccivax phong benh cau triing cho ga tir 6 ngay tuoi co tac dung bao ho den 54 ngay tuoi. Bach Manh Dieu va cs (2000, 2004) da che' vacxin nhugc doc bang phuong phap chieu xa Oocyst c£u triing, sir dung cho ga tir 6 ngay tudi cho kha nang bao ho den 36 ngay sau sir dung.
Nhung ket qua nghien curu che' tao va sir dung vacxin phong benh cau triing cho ga da mo ra trien vong cho nhirng nghien ciru tiep theo trong tuong lai, nham tien toi khong che' benh cau triing 6 ga.
Cac loai vacxin phong benh cau triing dirge tong hgp trong bang sau:
Bang 7. Cdc loai vac xin phdng benh cau trung cho ga r
Ten vicxin Ndi san xuat Khang nguyen Cach dung Tudi ga su1 dung (ngay)
Thdi gian ra ddi Coccivax Sterwin lab.
(My)
Hon hop Oocyst
cac loai cudng doc
Pha ni/dc
uong 4 - 14 1952
Immucox Vetech lab.
(Canada)
Hon hdp cac loai cifdng doc: E. tenella E. maxima E. acervulina E. necatrix Pha nude uong 4 - 7 1985 VAC. M Elanco products Company (My)
Oocyst cirdng doc
loai E. maxima Pha nUdc
udng - 1989
Paracox
Mallinkrodt veterinary Ltd. (Anh)
Cac dong tien noan nang cua:
E tenellaE maxima E maxima E. acervulina E. mitis E. brunetti E praecox Pha nude uong 5 - 9 1992 Livacox X. D (Dung cho ga nuoi long) Bio Pharm research Institute (cong hoa Sec)
Oocyst nhudc doc cua cac loai: E. tenella E. acervulina Pha nude uong 7 - 10 1992 Livacox T. (Dung cho ga nuoi nen co chat don chuong)
Bio Pharm research Institute (cong hoa Sec)
Oocyst nhUdc doc cua cac loai:
E. acervulinaE maxima E maxima E. tenella
Pha nude
5. P H O N G T R I B E N H C A U T R U N G C H O G A
Co 4 bien phap chmh trong phong chdng benh cdu trung cho ga:
5.1 . V e sinh th u y
V6 sinh thu y la cong viec lam thudng xuyen nhung dong vai tro he't stic quan trong trong chan nuoi va phong dich benh. Hien nay, d nhung nude tien tien, ngudi ta da tem ra't tot cong tac ve sinh phong benh (ve sinh chuong trai, thurc an, nude udng, dung cu chan nudi) nen da han che' dugc viec dung thud'c va vacxin trong chan nudi ga.
6 nude ta, chan nuoi gia cam da co nhieu tie'n bd: viec thuc hien quy trinh chan nudi nghiem ngat hom, rieng va'n dd ve sinh thu y cung t<5t hem ra't nhidu so vdi c£ch day mdt vai thap ky. Tuy nhien, vdi dac diem thdi tiet khf hau cua nude ta, vdi tinh trang khang thudc cua ky sinh trung noi chung va c5u triing noi rieng thi kha nang bie'n ddi va thfch nghi cua chung ra't ldn. Mat khac, va'n de ve sinh thu y chua ddng bo d ta't ca cac co sd tap the va tu nhan chan nudi gia c£m. Do chfnh la nguyen nhan lam cho benh cau triing ga van la mot trong nhumg benh gay thiet hai ldn nhat cho chan nudi ga, dac biet la ga nudi cdng nghiep va ga mdi nhap noi.
5.2. P h o n g t r i ben h b an g hoa dugc
Phong tri benh cau trung bang hoa dugc la phuong phap kinh dien va hieu qua. Trong nhumg nam gan day, cd nhieu loai thud'c mdi ra ddi, cd tac dung phdng tri ciu
trung tot. Tuy nhien, nhumg thudc cu da dugc dung trong nhieu thap ky, nhung cd hieu luc cao van dugc tiep tuc su dung. Viec phdng chdng cau trung phai dua tren nguyen tac: khdng ndn dung mot luc nhieu loai thud'c, cung khdng nen chi dung mot loai thudc keo dai nhieu nam trong mot co sd chan nudi ga.
Nhirng hoa dugc da va dang dugc su dung phdng tri cdu trung gom:
5.2.1. Cdc Sulfam id
Sulfamid dugc su dung pho bien la: Sulfadimedine, Sulfadimethoxin, Sulfachlozine, Sulfachlopyridazine, Sulfathiazole.... Co che tac dung cua Sulfamid la uc che su phat trien cua vi sinh vat noi chung va cau trung noi rieng bang cach canh tranh vdi PABA (Para - Amino Benzoic - Axit), ngan can su tong hgp axit folic, can thiet cho su sinh trudng va phat trien cua cau trung.
Hien nay, nhom Sulfamid van dugc dung kha pho bien, song cung co quan diem cho rang, neu dung dom le Sulfamid thi khdng tot cho gia cam, nha't la ga de va ngudi sir dung san pham.
5.2.2. N hom hod duac lam tang cuang hieu luc cua Sulfam id
Cac chat co tac dung lam tang cudng hieu lire cua Sulfamid nhu: Diavedrine,
Trudc het, Sulfamid canh tranh vdi PABA, lam cho cau trung khong tdng hop duoc axit folic. Sau do, cac hoa duoc tren phat huy tac dung, lam tac dung cua Sulfamid tang cudng va keo dai hon.
Tac dung cua Sulfamid va chat tang cudng la tac dung hiep dong, co gia tri ddi vdi cac vi sinh vat da quen va khang thudc. Ngoai ra, chat tang cudng con lam cho sir khuech tan cua thudc vao cau trung nhanh hon, dua lai tac dung tot hon. Chat tang cudng khi dung phdi h(^> vdi Sulfamid co the cho phep giam lidu Sulfamid xudng 10 lan so vdi chi dung Sulfamid don le.
Sau day la mot sd loai thudc ma trong thanh phan cd sir phdi hop Sulfamid va chat tang cudng: