| Classical swine fever (CSF) is a highly contagious viral disease of pigs caused by Classical swine fever virus (CSFV), and the mortality rate is often very high. Now, brood sow usually take CSFV which become infective agent for long, this is a significant reason that CSF always happen in scale swine field.How to select the brood sow taking CSFV in time that is significance for controlling and eliminating CSF in scale swine field.However, for controlling and preventing piglet away from CSFV,we should take well arranged measure and get effective the immunity program.thus, In order to search for eradication measure of CSF in breeding swine herd and boost antibody level of piglet herd,the study carry out following work.1. Establishment and clinical application of RT-nested PCR detection for classical swine fever virusUtilizing VectorNTI8 to contrast and analyze the E2 sequence of 29 wild CSFV strains , 6 vaccine strains and BVDV published by Different country and area, Devised two couple primer,Amplification target size of outer and inner primer is 806bp and 512bp. Test result indicate that the Sensitivity of RT-nested PCR and real-time RT-PCR is corresponding and raise 100 time contrasting general RT-PCR , the result of detecting 25 standard samples indicate the RT-nested PCR is specificity for amplificating CSFV sequence.And applied the RT-nested PCR to search for rule that brood sow's tonsils take vaccine virus after immunization,the result show that when brood sow immunize 750RID of cell cultures vaccine , brood sow's tonsils taking vaccine virus could last 25d.Thus,maybe we can say the RT-nested PCR can distinguish wild virus infection when brood sow immunize 750RID of cell cultures vaccine 30d later.Accomplished above studies later, we engaged in eradication measure of CSF in 4 breeding swine fields with the RT-nested PCR.and detect 1498 brood sow's tonsils,the result show that wild virus positive number is 66, positive rate is 4.43%.moreover,PCR product of positive sample and vaccine strains coming from a scale swine field during 2008 were carried out nucleotide sequencing,the result indicated that it just exist a wild virus strains in the field. And other nucleotide sequencing of positive sample show that the RT-nested PCR is just applied to amplificate wild CSFV strains.All clinical trial indicated that the RT-nested PCR refer to detect wild CSFV strains existing persistently in brood sow herd at scale swine field. Development of RT-nested PCR detection for classical swine fever virus that offered technology support to control and eliminate CSF of brood sow herd. 2.Survey of Classical Swine Fever Immunization level in Large-scale Pig Farms and Optimization of Piglets' ImmunizationIn order to investigate immunization schedules of classical swine fever(CSF) in large-scale pig farms, and to evaluate the immune effects, seven large-scale pig farms in Hubei province were studied. Swine herds were divided into the sows, the boars, the prepubertal gilts, the breast-feeding piglets (about 0～30 days), the nursing piglets (about 31-60 days old) and the growing pigs (above 61 days old). In each swine herd, 5%～8% of pigs' blood were collected and antibody titers were tested; Results showed that the passing rate of all swine herds' CSF Immunization are 99.55%,96.43%,99.22%,89.88%,81.68% or 78.64%,and different immunization schedule induced different immune effects. Overall, the nursing piglets and the growing pigs is the weakest in all pig groups .Therefore, piglet's CSF maternal antibody retrogression rule and first Immunity time of Piglet was studied based on the antibody investigation.In the study, CSF maternal antibody subsided following day-age of Piglets and these of 70% is under protection line.Results indicated that 28 days after birth was the best time of first immunization.This study has certain reference value to the pig farm's formulation of reasonable CSF immunity schedule. |
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