Development Of Inactivated Vaccine Against Porcine Edema Disease

Edema disease of swine (ED) is an enterotoxemia caused mainly by Shiga toxin E.coli (STEC) which can prod cutaneous dropsy at face, conjunctive tunic, dental caries, eyelid, submaxilla, gasyric wall of piglets and nerval symptom. This disease which display the feature of endemic epidemic usually attack weaned piglets. Although the incidence rate is less than10%-30%, the mortality rate reaches to80%-100%. It’s one of the most important infectious disease which impacts the development of the swine industry. With the enlargment of the cultivation field and the increase of piglets breeding density, Ederma disease gradually becomes a significant communicable disease causing death of post-weaning pigs. The preventive and therapeutic measures to the disease depend on strengthening breeding administration and relieving the symptoms at present, but the recovery rate is low. Consequently, vaccine immunifaction has become one of the most economic and effective pathway to control this disease.The Bacterium coli which causing Edema disease is called Shiga toxin E.coli (STEC). It produces two virulence facts:adhesin and Shiga toxin (Stx). Adhesin includes fimbria, OMP, intimin and so on. Fimbria F18is an important virulence fact which helps to ecesis and reproduce in cellula epithelialis of mucous membrane. Stx is a protein cytotoxin produced by Shiga toxin E.coli. It has many kinds of serotype. The frequent serotype is0139, K82,0138, K81,0141, K85,045, and08and so on. Recently, there were many papers that reported on isolation and identification of piglet enteropathogenic E.coli, but the developments of the vaccine were not satisfactory simultaneously. There is not safe and effective commercialization vaccine which obtained the nation license nowadays. In this study, three different serotype bacterial strains (C83905:O138、C83684:O139、 C83527:O141) of E.coli were introduced from China Institute of Veterinary Drugs Control to develop the high performance inactivated vaccines against Porcine Edema disease. According to the applying requirement of the new veterinary drugs, the purity, cultural character, biochemistry character, serotype, virulence, immunity of the strains have been detected separately and yet the stability tests have been executed.The results showed that the three strains were Gram-negative bacteria, and the serotypes of C83905, C83527, and C83684were0138,0141, and0139respectively. The strains’minimum lethal dose for mice were3.6×108CFU(C83905),3.0×108CFU (C83527),2.0×108CFU (C83684). The MLD of the toxinum of the three bacteria were all0.1mL per mouse, while the toxinum mixture of the three bacteria for mice was0.2mL per mouse, and for14d-18d old piglets, the MLD was30mL,40mL,40mL respectively. And the MLD of toxinum mixture was30mL per pig. When receiving the inactivated vaccine prepared respectively with the three strains, the mice and the piglets which were injected0.05mL and2mL respectively could counteract the challenge with the fatal dose of the strains and the toxinum, and showed80%-100%protection rates. All the results showed that the three strains corresponded completely with the requirement of vaccine preparation as we expected.On the basis of the laboratory process, the culture medium, inactivated condition and adjuvant were optimized under industry producing conditions. In consideration of (the stability of bacterial stain and the cost of production, the improved LB medium was selected as the optimal one. The optimal concentration of formaldehyde was0.4%and the inactivating condition was48hours at37℃. Finally, Trivalent (O138、O139、0141) inactivated vaccine against piglet edema disease was developed successfully. According to the experimental results, the initial manufacture and test regulations and the quality standards of this vaccine were carried out.Then, six batches of the laboratory processing vaccine had been prepared, and the tests of safety, efficacy, min-immunizing-dose, immunity and keeping time were tested. All the results showed that the products which could induce pronounced immune response were safe and effective. The min-immunizing-dose which could obtain100%protection is0.05mL for mouse and2mL for piglet. The immune period could last for three months at least, and the storage period could be twenty-four months at2-8℃.In addition, the correlation about the immunizing dose of strains and vaccines for mice and piglets were detected during the virulence, safety and protection test. It showed that piglets could be replaced by mice for tests in practical production.Six batches semi-works products were tested according the regulation and the standard severely. The protection rate of six batches semi-works products was higher than95%in two field experiments. The production were used for more than100,000pigs in Shenyang, Dalian, Anshan, Jinzhou, Tieling, Liaoyang of China and so on, and showed better safety and excellent effect.The trivalent(O138、O139、0141) inactivated vaccine against piglet edema disease had been registered and it had been awarded the second-class certificate of national new veterinary drugs in Aug,2006.