Studies On The Characteristics And Inducement Of Resistant Srain For Precocious Strain Of Eimeria Tenella In Chickens

In order to improve the immune level of precocious strain of Eimeria tenella in chickens,we use vaccine to prevent coccidiosis ,but some anticoccidial drugs which are also antibiotic are forbidden to use for interfering the vaccine immune.there maybe cause other infectious deseases,so we adopt a mathod to increase continuously drugs'concentration,to induce these drugs'resistant strain that can be used to immune coccidiosis and to use these drugs to control other deseases.In the experiment of the studies on the immune characteristics for precocious strain;.according to the relative body weight mortality percentage, lesion score, oocyst output after challenge.the pathologencity of the precocious strain was found to have weakened markedly,its perfect immune dose was first time 1500 and second time 2000,we also found its protective time .first immunity can protect 1 month,but second time can protect over 3 months.In addition,the results of immunological study of precocious line through Dot-ELISA showed that both the first immunity and the second immunity can induce the protective immunity ,and the effects two times immunity were stronger and longer than that of only one time immunity.Resistance to 1600mg/kg oxtetracycline and 2000mg/kg sulfadiazine appeared after 6 and 8 passages respectively.Initial concentrations of dings were 800mg/kg oxtetracycline and 500mg/kg sulfadiazine.Through the test of the cross resistance between oxtetracycline and sulfadiazine.we induced cross resistant strain for precocious line of E.tenella after 5 passages.To compare the precocious strain(P₁₅) resistant strain(R) and parental strain(P₀) of E.tenella,for immunity characteristic,P₁₅ and R keep good immunity,both have lower moratality ,the ID₅₀ of P₁₅ R and P₀ separetely were 12 x l0⁴ 11 X 10⁴and 0.99X10⁴,the LD₅₀ of P₁₅ R and P₀ separetely were 27.64xl0⁴ 25.2x10⁴ and 7.52x10⁴.The ACI of P₁₅, and R,were higher than P₀,and ACI will get lower if the oocyst increased.The lesion score of P₁₅ and R were lower than P₀,so we can use resistant strain of E.tenella to immune coccidiosis,at the same time ,we can also use some bacteriophage to control other infectious deseases,improving vaccine's immune level,it can be used in practice.