Comparison Of The Protective Effects Of The Tetravalent Anticoccidial Vaccine On Different Immune Pathways Shen Guocong

Coccidiosis is one of the most common and serious parasitic diseases in poultry production in C hina.The cost of treating chicken coccidiosis accounted for a quarter of the total medicine cost for common chicken diseases,which caused severe economic losses.The drug resistance of coccidia is widespread,and there is environmental pollution in veterinary drug production.An increasing attention is being paid to drug resistance and drug residues in chicken products.Additionally,drug treatment has become increasingly limited,which has made the choice of applying vaccines to prevent chicken coccidiosis mainstream.The immunological effect of vaccines in chickens depends on the number of oocysts that were digested.The uniformity of d ifferent immunization methods will lead to differences in clinical immunological effects.With the development of raising chickens in intensive,large-scale farming patterns,selecting a good immunization method for chicken coccidiosis has attracted the attention of chicken industry personnel.In the present studies,the immunological effects of vaccination at various ages of chickens were analysed.An experiment on inoculation via drinking was carried out on various days.Forty chickens with an age of one day were divided into two groups;one of the groups was negative,and the other group was called the drinking immunity group 1.Twenty chickens aged four days comprised the third group,which was called the drinking immunity group 2.Except for the negative group,all chickens were vaccinated for chicken coccidiosis using the tetravalent vaccine via drinking.The chickens were raised in a flame-sterilized henhouse,and oocysts were collected from the small intestinal faece and cecal faece.The average total oocysts from each chicken and weight gain were calculated in the three groups,and the situation of intestinal lesions and bloody stool was observed.Two immune groups had equal oocyst excretion.After the chickens were challenged with a large amount of oocysts,the difference in intestinal lesions between the drinking immunity group 1 and group 2 was not significant.The relative weight gain rate in the drinking immunity group 2 was 86.6%,which was slightly higher than that in the drinking immunity group 1,which was 85.1%.The bloody stool score was 0 in immunity groups 1 and 2.We concluded that there was no obvious difference in the immunological effect when the chickens were vaccinated at age 1 day or 4 day.An experiment regarding different doses of spray vaccination was performed.Sixty chickens that were one day old were divided into three groups.One of the groups received oral immunization,and the others were vaccinated with the chicken coccidiosis tetravalent vaccine by different doses of spray vaccination.The chickens that were vaccinated with spray vaccination were divided into the spray vaccination group 1(the dilution between vaccine and water was 1:9)and the spray vaccination group 2(the dilution between the vaccine and water was 1:19).All chickens were raised in a flame-sterilized henhouse,and the oocysts were collected from the small intestinal faece and cecal faece.We calculated the fecal oocyst OPG value using the method of Mike Mc Master and compared the differences in OPG values between every group.The relative proportion of the total oocysts in the spray vaccination group 2 was 3.5%,which was higher than that in the spray vaccination group 1,which was 2.4%.We concluded that spray vaccination,in which the dilution between the vaccine and water was 1:19,had a better immunological effect.210 chickens at an age of one day were divided into three groups and were vaccinated with the chicken coccidiosis tetravalent vaccine via drinking,spray vaccination and a mix of vaccine-treated forage.Seventy chickens were in the fourth group and were treated as negative controls.All chickens were raised in a flame-sterilized henhouse,and oocysts were collected from contaminated fecal samples from the small intestine and cecum.We calculated the fecal oocyst OPG value using the method of Mike Mc Master and compared the differences of OPG values between every group.We analyzed and compared the pathological scores of the intestinal tract of each group during the vaccine reaction.The results showed that the oocysts in the spray vaccination group were quite different.The oocysts of every chicken in the drinking immunity group and mix of vaccine-treated forage group had no obvious difference.In the three immune methods,the OPG of Eimeria maxima,E.tenella and E.necatrix had 2 peaks,and the first OPG peak occurred at the same time.The OPG peak of E.acervulina appeared at 14~16 days.The score for intestinal lesions in the drinking immunity group was the highest and the spray vaccination group was the second,and followed by the mix of vaccine-treated forage group.We concluded that the three different immune methods were safe for the chickens,but the spray vaccination method had poor uniformity.We randomly selected sixteen chickens at an age of twenty-one days in the negative group,and the chickens were divided into the negative control group and positive group.Eight chickens from each immune group were also selected randomly to carry out the challenge experiment.All chicke ns were killed after the six days of challenging.The chickens’ mental state,bloody stools,and intestinal lesions were observed,and the mortality rate and relative weight gain rate were calculated.The results showed that three immune methods in the experimental group could produce protective immunity,drinking immunity and the mix of vaccine-treated forage group had a better effect than the spray vaccination group.