- Esb3 (hang Novatis, Thuy Sy san xua't): thanh phan chfnh la Sulfachlozine sodium monohydrate (30%).
11. Ldp vo ngoai (Outer layer of Oocyst wall)
1.4. Tinh chuyen biet cua ciiu trung
Tmh chuyen biet cua d u trung la sir thfch nghi phuc tap va lau dai cua cau trung doi vdri co th6 ky chu hoac cu the hon ddi vdi cac co quan, cac md bao hay te bao nhat dinh phu hop cho su tdn tai, phat trien cua chung. (Kolapxki N.A. va cs, 1980, Le Van Nam, 2003).
+ Ddi vdi gidng Eimeria:
Tfnh chuyen biet cua cau trung Eimeria the hien rat nghiem ngat, chung chi co the gay benh cho ky chu ma chung thfch nghi trong qua trinh tien hoa.
Vf du: cac loai c£u trung ciru khdng the nhiem vao bo va cac gia sue khac. Cau triing tho chi cd the lay nhiem vao tho ma khdng the nhidm vao cac loai gia sue khac.
Theo Kolapxki N.A. va cs, (1980), nhung loai cau triing rieng biet ky sinh 6 cac loai gia sue khac nhau thudng khd phan biet vd mat hinh thai. Vf du: mot so loai cau triing ciru va de hoac ga va ga tay rat gidng nhau vd mat hinh thai. Tuy nhien, mot vai thf nghiem da cho tha'y, cdu triing ciru khdng nhidm vao de duoc.
Vi vay, cac nha khoa hoc da thong nhat lay ten chung cau triing va them ten ciia loai gia sue de’ goi ten benh nhu: cau triing ga, cau triing 1cm, cau triing th o ...
Dac tfnh chuyen biet nghiem ngat ciia cau triing giong Eimeria sp. bieu hien khdng chi ddi vdi ky chii ciia chung, ma mdi loai cau triing chi khu tru tai mot viing, mot co quan nao dd nhat dinh trong co the ky chii. Vf du: Eimeria tenella chi ky sinh va gay benh trong niem mac manh trang ga, trong khi dd Eimeria acervulina lai chi ky sinh trong niem mac ta trang. O Ion: chiing Eimeria debliecki cu tru d ta trang lam cho niem mac ruot bi viem rdi xuat huye't hoai tir.
Nhu vay, neu xem xet tfnh chuyen biet ciia cau triing thi gidng Eimeria bidu hien rat ro ret, tfnh chuyen biet dd da hinh thanh trong qua trinh thfch irng lau dai ciia ky sinh triing ddi vdi mot ky chii nha't dinh cung nhu ddi vdi timg co quan, timg md bao rieng biet. Theo dan lieu ciia Khayxin (1947), do la didu kien co ban giup cho nhieu loai cau triing ky sinh dong thdi tren ciing mot ky chu.
+ Ddi vdi gidng Isospora:
Cac nha nghien cuu cho bie't, dang tang trucmg va phat trien trong qua trinh sinh san ciia Isospora khdng cd tfnh chuyen biet, vi the san pham tang trucmg ciia Isospora
gondii hoac ciia I. bigemina la Toxoplasma cd the gay benh khdng chi cho chd, meo ma
cdn cd kha nang gay benh cho chuot, cu li, thd, ciru, linh ducmg, hoang, bo cau, chim se,vit, riia, ran va ke ca con ngudi.
1.5. Sure de khang cua can triing
Sire de khang ciia cau triing la kha nang chdng lai cac tac nhan ben ngoai tac ddng den sir sinh truong va phat trien binh thudng cua cau triing. Cac yeu td ngoai mdi trucmg nhu nhiet do, do am. cac chat hoa hoc,... ndi chung deu tac dong vao Oocyst, dieu nav
co y nghla ra't 1dm trong nghidn curu dich te hoc benh ciiu trung va phuong phap phong chong bdnh cdu trung trong chan nu6i.
* Anh hudng cua cac y£u td vat ly
+ Nhiet dd: mdi trucmg dm udt va nhiet dd 6n hoa Ik didu kien thuan l(?i nhat cho cdu trung phat trien. Nhiet dd 20°C - 23°C chi mat 1 6 - 1 8 gid de cau trung phat tridn thanh bao tir con.
Theo Luong Van Hua'n va cs (1997), Oocyst cua E. debliecki, E. scabra co the t6n tai trong mdi trudng ben ngoai 15 thang d nhiet dd tCr (- 4°Q - 40°C, Oocyst khdng cd bao tir tiep tuc tdn tai d nhiet dd (- 2°C) - (-7°C) ft nha't 26 ngay.
Le Van Nam (2003) cho biet, nhiet dd thich hop cho qua trinh phat trie’n bao tu nang ngoai co th£ la 15 - 35°C. Lanh -15°C va ndng tren 40°C bao tu nang se chet.
So sanh kha nang chiu dimg cua Oosyst trudc va sau khi sinh bao tu, Glullough N. (1952) thay rang: d nhiet do cao chung deu bi tieu diet d nhiet dd 40°C sau 96 gid, 45UC sau 3 gid va 50°C sau 30 phut. Khi nhiet do tuong ddi tha'p (12°C - 20°C ) Oocystda sinh bao ttr tdn tai duoc 14 ngay, nhung vdi Oocystchua sinh bao tu chi chiu duoc khdng qua 56 gid.
Long P.L va cs (1979) cho rang: Oocystcd the tdn tai qua mua ddng gia lanh, nhung khdng chiu duoc nhiet do cao.
Trong dieu kien nude ndng 80°C, Oocystchet ngay turc khac (Onop E.M., 1962).
j
+ Am do: am do cd vai trd quan trong trong giai doan cau trung sinh san bao tu ngoai mdi trudng va anh hudng de'n kha nang tdn tai cua Oocystcau trirng.
Theo Ellis C.C (1986), d nhiet do khdng thay doi Oocyst se bi chet khi am dd giam. Nhiet do tir 18°C - 40°C, am do 21% - 30% thi chung de bi chet sau 4 - 5 ngay.
Goodrich H.P (1994) da dua ra ket luan: ldp vo ngoai da giu cho Oocyst khdng bi tham chat long, nhung nd lai de nut trong dieu kien khd han.
+ Cac tia tu ngoai
. Theo Warner D.E (1933), Oocyst tdn tai 18 tuan trong da't ram mat mot phan, 21 tuan trong dat ram mat hoan toan.
Anh nang chieu true tiep tac dong gay hai den Oocyst, nhung cd dai da bao ve chung tranh tia X (Long P.L va cs, 1979).
Theo ket qua nghien cuu ciia Fish (1932) d phdng thf nghiem, cac Oocyst bi tieu diet khi chieu tia tir ngoai d cudng do vira phai.
Pham Van Chuc va cs (1989) cho rang, Oocyst khi bi xu ly buc xa d muc 20 - 35 Krad cho gia tri bao ho tot nhat (100%), dudi 10 Krad (80%), nhung neu lieu qua thap hoac qua cao thi khdng co hieu qua phdng benh. Oocyst chua sinh bao tir ft man cam doi vdi tia X hon Oocyst da sinh bao tir tdi 15 lan.
Su chiu dung dac biet vdi moi trudng bien doi do co sue dd khang voi mot so chat tdy trung Ia yeu 16 quan trong de’ duy tri su ton tai va lay truyen ciia cau trung. Oocyst
c<iu triing co sue dd khang cao vdi cac loai hoa chat va thuoc sat triing thong thudng. Perard (1925) cho biet, Oocyst co the sinh bao tir sau nhieu ngay tiep xuc vdi dung dich sat triing: KM n04 0,1%, Formol 5%, H2S 04 va HC1 10%.
Tuy vay, mot sd chat lai diet duac Oocyst nen da duac ap dung de lam chat tieu doc chuong trai nhu dung djch amoniac 10%, metyl bromid. William R.B (1977) da nghien curu tac dung cua dung dich amoniac 10% trong 12 gid lien tuc co the lam cho 100%
Oocyst khong sinh duac bao tir va co the dung tieu doc tot.
2. DAC DIEM DICH Tfc HOC CUA BENH CAU TRUNG LON
Lodi vat mac benh: tat ca cac gidng lan nha va lan rung ddu cd thd mac benh.
Dudng bai xua't mam benh: lan mdc benh bai xuat Oocyst cau triing qua phan ra
ngoai ngoai canh. Oocyst duac phat tan rong rai d ngoai tu nhien va qua trinh sinh san bao lu bat dau de tao thanh cac Oosyst co kha nang gay benh.
Dudng xam nhap vao co the: lan nhidm cau triing qua dudng mieng, do Ion tiep xuc
vdi thuc an, nude udng, ndn chudng, dung cu chan nuoi nhidm Oocyst cau triing cd sure gay benh.
Cau triing lay nhidm tir lan benh sang lgn khoe theo 2 cach:
- Lay nhidm true tiep: lgn benh thai Oocyst c£u triing qua phan, do dd Oocyst se dd dang dugc phat tan trdn khap nen chuong, mang an, mang udng va dung cu chan nuoi. Tap tinh ciia lgn la thudng hay sue sao, liem lap nen dd nuot phai Oocyst cd sue gay benh.
Xet nghidm tim Oocyst (noan nang) cau triing trong gan 600 mau can nen chuong, san chai va khu vuc quanh chudng, tai 13 xa thuoc tinh Thai Nguydn, Nguydn Thi Kim Lan va cs (2005) cho thay: thdi gian phat trien ciia Oocyst cau trimg tdi giai doan cam nhidm phu thuoc vao nhiet do va am do moi trudng ngoai canh: loai E. debliecki tir 101 - 141 gid, E. suis tir 96 - 136 gid, E. porci tir 102 - 130 gid, /. suis tir 69 - 98 gid.
- Lay nhidm gian tiep: dung cu chan nuoi, ngudi chan nuoi, giay, dep. ung, phuang tien van chuyen cung ddng vai trd quan trong trong viec mang Oocyst cau triing tir ngoai vao trong chudng nuoi gia sue hoac tir o chudng nay sang o chuong khac.
Mac dii chua cd dan lieu ve su lay nhidm cau triing lgn qua dung cu chan nuoi, nhung nhung nghien cuu ve su lay nhiem gian tiep cau trung ga da dugc ghi nhan. Bach Manh Didu (1995) da kiem tra 420 mau xe cai tien. quang thung thay ty le nhidm cau triing la 4,28%. Hoang Thach (1999) khao sat 250 mau tir ung diing trong khu chuong nuoi, ty le nhidm la 5.6% va khao sat 250 mau dung cu don ve sinh chuong nuoi, ty le nhidm la 1 1,2%.
Ngoai ra. cac loai con triing, dong vat nhu gian, ruoi. chuot... cung la tac nhan mang Oocyst cau triing tir ngoai vao hoac tir o chuong nay sang o chuong khac.
Theo Nguyen Thi Kim Lan va Le Minh (2006 - 2008), cdc loai dOng vat thucmg cd 6 chu6ng Ion va khu vuc xung quanh chu6ng co khd nang mang Oocyst cdu trung. Tr°ng do, kha nang mang va phat tan Oocyst cdu trung Ion cua kien la 27,27%, r6i ru6i la 22,22% va gian la 16,67%.
Hinh 136. Dan kien mang-Oocyst cau trung vd Oocyst mang
Hinh 137. Dan ruoi mang Oocyst cau triing Hinhl38. Dan gian mang Oocyst cau trung
va Oocyst mang vd Oocyst mang
Benh cau trung d Ion lien quan den mot so yeu to sau:
- Mua vu: benh cau trung lpn phan bo khdng deu theo cac thang trong nam. Benh thudng xuat hien va de bung phat vao cac thang co khf hau dm udt, mua phiin, nhiet dd 18°C - 35°C. Chfnh vi vay, mua He va mua Xuan cd ty le nhidm cau trung cao hon mua Ddng va mua Thu.
- Tuoi: theo Le Van Nam (2003), lpn con tir 1 - 3 thang tuoi rat dd bi nhidm can nguydn, dac biet lpn con tu 15 - 60 ngay rat dd nhidm benh va benh dd dang bung no d the’ cap tfnh va dudi cap tfnh. Lpn trdn 3 thang tuoi chi mang triing, ra't ft khi bi benh.
Chae C. (1998) nghidn curu va cho biet, lpn con trudc cai sua d cac trai Ion nhidm
Svanbaep X.K. (1967) cho ding, mtic d6 nhidm c£u trung cao nhat la d Ion con tir 30 - 60 ngay tudi.
Kid’m tra 3.698 mlu phan lan tir 4 - 50 ngay tuoi a cac trai chan nuoi lan cong nghiep 6 thanh pho Hd Chi Minh, Lam Thi Thu Huong (2004) cho biet: ty le nhidm
Isospora suis cao hon Eimeria sp. va Cryptosporidium. Lgn trong giai doan 8 - 1 4 ngay
tudi ty le nhidm 42,70%, cao hom cac 16a tuoi khac. Sau 21 ngay tuoi ty le nhidm co khuynh huomg giam din. Ty Id nhidm c£u trung d lgn nuoi trdn nen ximang cao hom rat nhieu so vdi lgn nu6i trdn nen san. Ty le nhidm Isospora suis a nen ximang la 52,65%, n£n san la 35,60%.
Theo Nguydn Thj Kim Lan va Tran Thu Nga (2005), ty le va cudng do nhidm cau triing giam dan theo tudi, nang nha't a lgn con dudi 2 thang tudi.
Nhu vay, dong vat non dang trong thoi ky sinh truang manh dd bi benh va benh phat trien nhanh hom, nang hom so voi dong vat truang thanh. Dong vat da trudng thanh va dong vat gia cac bieu hien lam sang benh cau triing ft. Song, chung lai la nhumg dong vat mang triing va la nguon benh nguy hiem nhat ddi vdi dong vat non.
- Dieu kien ve sinh thu y: tinh trang ve sinh thu y la mot trong nhumg yeu td anh hudng ra't ldn den kha nang nhidm ciu trimg cua lgn.
Theo Morgot A.A. (2000), nhumg co sd chan nuoi co dieu kien cham soc tot, ve sinh chudng trai nghidm ngat thi ty le nhidm cau triing la 5 - 10 %. Ngugc lai, d nhung ca sd chan nuoi co didu kien khong dam bao thi ty le nhidm cau triing chiem 30 - 69%.
Nguydn Thi Kim Lan va cs (2005) cho bie't, lgn nuoi d tinh trang ve sinh thu y kem nhidm cau triing cao, tir 55,45% - 66,30%. Ty le va mure do nhiem giam ro ret d tinh trang ve sinh tot hom.
Hinh 139. Dan Ion nuoi trong tinh trang ve sinh thu y kem bi nhiem cdu trimg ndng
- Cac yeu to stress: yeu td stress co hai nhu chuong trai chat choi, thuc an kem dinh dudng. thieu sua. nhiet do moi trudng thay ddi, lan con dang mac cac benh kv sinh trims khac hoac hen suven thi benh cau triing xav ra nang hon.
3. D A C D I ^ M B $ N H L t V A L A M S A N G B fe N H C A U T R U N G L O N3.1. D dc d ie m benh ly