| Mycoplasmal pneumonia of swine(MPS)is a kind of chronic respiratory tract infectious disease aroused by Mycoplasma hyopneumoniae(Mhp),which can cause cough,wheezing and growth retardation and brings huge losses to the pig industry.The disease is so difficult to prevent and control that cause high economic loss MPS becomes a global problem.The current study shows that the best way to control the clinical morbidity is to carry out vaccine immunization.In order to investigate the epidemic pattern of MPS,the field investigation,clinical samples collection,laboratory test and data analysis of Ningbo region were used to evaluate the severity of Mhp infection.The Mhp control method by vaccine immunity was successfully established in this study and the main contents were as follows:1,The epidemiological survey of MPS:the pig lung samples with typical pneumonia lesions were 52.5%by clinical observation;the Mhp positive rate of clinical samples by PCR detection reached 26.7%.Meanwhile,the positive rate of serum antibody of the non-vaccinated herds was 42.7%by ELISA.According to the results of the above analysis,the infection of Mhp on the farms in Ningbo is severe.2,The serological survey of MPS:The serum antibody positive rate of sows by random sampling was 100%,which indicating that the antibody levels of sow herd was high;the positive rate of maternal antibody of non-immune piglets at the age of two weeks reached 68.7%,while the lowest level is 16%in the six-week age group,which indicating that the maternal antibody gradually increased with the growth of the pig age at first,then decreased,then increased again to 71%by 13-weeks age.The data showed that the infection of Mhp was significantly correlated with the age of swine.It provided evidence for the selection of the best pig age for immunization.3,The evaluation of vaccine immunization efficiency:the experimental subjects were the negative pig groups of Ningbo area by above analysis.They were divided into four groups for immunization,group I with inactivated vaccine 1,group II with another inactivated vaccine II,group III with live vaccine and group IV without immunization.The serum samples were collected at the 14th,28th,42th and 56th day after immunization and then subjected to antibody levels test.The clinical symptoms,coughs and pulmonary lesions were also observed.The results showed that:(1)The positive rates of serum antibodies of Mhp were 0 and no significant differences were observed in the four groups when they were 14 days old;the positive rate of group I and II with inactivated vaccine continue to increase from 28 to 56 day old.The seropositive rate of group III with live vaccine was always 0,while the positive rate of seropositive antibody in group IV was 10%,which was suspected to be caused by wild strains infection.It showed that inactivated vaccine induced better immune response and produced higher serum antibody than live vaccine.(2)The incidence of Mhp was observed by clinical observation of cough.The incidence of Mhp in pigs of all groups was 0 at day 14;the incidence rates of gruop I and II were lower than those in control group IV but higher than group III,which indicated that the effects of live vaccine is better than inactivated vaccines in controlling Mhp clinical symptom.(3)The observation of lung lesions:One pig of each group was randomly selected for the observation of lung lesions.The results showed that the MPS lesion of treatment groups were significantly higher than those of the control group of group IV,and pigs in group I and II showed a few lesions,but the difference was not significant,while there was no obvious lesion in group III.This indicated that the live vaccine was better than the inactivated vaccine in lung protection.It also proved that the choice of appropriate vaccine for immunization is the best way for effective control of MPS. |
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