- Xam nhap qua ducmg bao thai: hien nay, ngudi ta da chumg minh duoc rang, nhi£u vat ky sinh cd kha nang cam nhiem qua dudng bao thai Fromann (1963) da xac dinh
2. VAN DE KHANG THUOC CHONG KY SINH TRUNG
2.1. Mot so tien bp cua hoa trj lieu va hoa dir phong nhiem ky sinh trung
2.1.1. Cac thudc hien dung tri ky sinh triing
Thuoc tri ky sinh trung rat khac nhau giua cac nuac. Nhung thuoc chong ky sinh trung d cac loai vat nu6i hien co gom:
- Trau, bo nuoi thit: Abamectine, Albendazole, Fenbendazole, Febantel,
Doramectine, Moxidectine, Ivermectine, Levamisole, Oxfendazole, Netobimin,
Trichlorfon, Tartrate va Citrate morantel.
- Trau, bo nuoi lay sua: Tartrate morantel, Trichlorfon.
Ciru: Albendazole, Fenbendazole, Febantel, Ivermectine, Levamisole,
Mebendazole, Netobimin, Oxfendazole.
De: Albendazole, Fenbendazole, Febantel, Doramectine, Ivermectine,
Mebendazole, Netobimin, Oxfendazole.
- Ngua: Febantel, Fenbendazole, Ivermectine, Mebendazole, Oxibendazole, Embonate pyrantel, Trichlorfon.
- Lpn: Mebendazole, Albendazole, Levamisole, Praziquantel, Fenbendazole, Ivermectine, Oxfendazole.
- Cho: Embonate pyrantel, Oxfendazole, Praziquantel, Flubendazole, Nitroscanate, Mebendazole, Fenbendazole, Levamisole, Niclosamide.
- Meo: Enbonate pyratel, Praziquantel, Flubendazole, Mebendazole, Fenbendazole. Nhu vay, doi vai m6i loai vat nuoi co nhieu thuoc chong ky sinh trung co the su dung dupe. Tuy nhien, su lua chon loai thuoc phu hop va co tac dung tot phai dua tren cac tieu chuan: co hieu qua cao, an toan vPi vat nuoi, gia thanh hop ly; dong thoi cung dua vao dac diem dich t<§ hoc cua benh ky sinh triing va xem xet tinh khang thuoc cua ky sinh trung.
2.1.2. M ot so dang mai cua thuoc chong ky sinh triing
De dS su dung va tang hieu qua dung thuoc, mot so san pham cu (vi du: Benzimidazole) dupe che duoi dang cac he thong giai phong lien tuc hoac gian doan. Cac he thong nay dupe phat trien nham lam giam thao tac lap lai tren con vat.
Mot so dang moi cua thuoc chong ky sinh trung gom:
- Tang da liem co chua Prebendazole dung cho gia sue hem de phong va tri giun san. Thai gian cho Hem thay doi tuy con vat.
- Vien thuoc Ion (bolus) giai phong lien tuc morantel de phong tri giun san cho bo. Co hai dang:
+ Paratec bolus: he thong bang kim loai tac dong tu 60 den 90 ngay.
+ Paratec flex: la ba manh bang nhua. La trung tam co chua Morantel. Sau khi dua thuoc vao, cac la ma ra, giai phong thuoc taiy giun tron trong khoang 90 ngay.
He thong "bolus" giai phong lien tuc Albendazole dung cho ciru. Ben trong he thong nay co mot lo xo lam cho vien thuoc tay giun san tiep xuc vdi dich da co va tan ra d£u dan trong 90 ngay (captex bolus).
H6 thong "bolus" giai phong lien tuc Fenbendazole: tac ddng ddu dan trong 130 ngay.
He thong "bolus" giai phong lien tuc Ivermectine: tac dong lien tuc trong 135 ngay. He thong "bolus" giai phong lien tuc Oxfendazole: 5 vien nen Oxfendazole duoc phfin bo trong cac bu6ng ke tiep xung quanh true bang Megie. Sir bao mon true nay cur 21 ngay giai phong 1 vien nen.
2.1.3. Cac lactone dai phan tu vdng
Nhieu loai thuoc chong ky sinh trimg co ca'u true ciia lactone dai phan tu vong. Chung tac dong theo co che tac dong lam md, theo cach khdng phan h6i vao cac k6nh Chlore ciia mang nguyen sinh chat te bao co ciia ky sinh trimg (giun, san).
Mot sd thudc co ca'u true lactone dai phan tir vong gom: - Ivermectine
Ivermectine la dan xua't ciia Avermectine BI va Avermectine duoc tao ra bdi vi khuan Streptomyces avermectilis.
- Abamectine. - Moxidectine.
- Milbemycine Oxime. - Doramectine.
2.1.4. Cac phan tu thuoc m&i co tac dung trong tuang lai
Trong tuong lai, viec nghien cuu cac phan tir thudc mdi co y nghla quan trong trong viec khac phuc tfnh khang thudc ciia ky sinh triing.
* Paraherquamide
Phan tir nay duoc tao ra tir nhieu loai nam khac nhau thuoc chiing Penicillium va to ra co hieu qua ddi vdi hau het cac giun ky sinh d da day, ruot va phoi. Tuy nhien, phan tir nay co hieu qua thap va doc ddi vdi cho. Cac nghien cuu thuc nghiem cho thay,
Paraherquamide duoc sir dung chong Haemonchus contortus, Oesophagostonnim
circumcincta, Trichostrongylus colubriformis co hieu qua.
Phan tu Paraherquamide duoc quan tam vi hien nay cac loai giun san phat trien rat nhanh, kha nang khang mot sd thudc khac va co che tac dong ciia no cung khac vdi Avermectine va Milbemycine. Viec sir dung phan tir nay nham pha vd sure khang thudc ciia ky sinh triing vdi Avermectine trong tuong lai.
* PF 1022A
Nhung so lieu nghien cuu ban dau cho thay, phan tu nay co hieu qua chong
Ascaridia galli d ga, Toxocara canis va T. cati d cho va meo, H. contortus va Ostertagia ostertagia d trau, bo, de, cuu. Phan tu nay rat ft doc tfnh.
* Dioxapyrromomycine
Phan tu nay cung duac tao ra bai nam Streptomyces sp., co pho hoat luc hep. Tac dung cua phan tu nay duac nghien cuu nhieu nhat a H. contortus. Dioxapyrromomycine tac dong tren nhung chung giun san khang vai Benzimidazole, Avermectine va Levamisole, nhung khong tac dung tren nhung chung khang vai Closantel.
* Clonostachyol
Phan tu nay duac tao ra tir nam Clonostachys cylindrospora. Cac nghien curu ban dau cho thay, thudc tac dung tren Haemonchus contortus.