The Study Of Molecular Epidemicology Of Newcastle Disease Virus Isolated In China And The Protective Effect Of Lasota Vaccine Protect Chichens From Genotype â…¦ NDV

Newcastle disease (ND) is a highly fatal and contagious avian disease caused by Newcastle disease virus (NDV). It is also one of the List A animal infectious disease which cause sever avian epidemic worldwide every year. More and more vaccine was used to prevent poultry from ND. It is important to study ND molecular epidemicology because of a negative-sense single-stranded RNA virus and higher variability of NDV.There are three researching methods have been used to study the molecular epidemicological technology of NDV: monoclonal antibody, restriction endonuclease, amplification of the special segment of F gene and drawing the phylogenetic tree. In this paper the special function region of the F gene of 65 NDVs were amplified by one step RT-PCR. The results of the deduced Amino-acid sequence and the characteristic of the gene showed that 47 strains of them are belongs to NDV genotype VII, 6 strains of them are belongs to NDV genotype III, 6 strains of them are belongs to NDV genotype VI and 6 strains of them are belongs to NDV genotype II. NDV026 is belongs to the velogenic strain by the analysis of amino-acid sequence, but it belongs to genotype II by genotype analysis. The amino-acid sequence of NDV026 is almost the same as that of Lasota strain except the position 1 12, 115, 117 of amino-acid. It is suggested that it would be the result of hybrided or intragenic mutated. Generally, NDV genotype VII has being dominated in China although there are some old genotypes such as NDV genotype II, NDV genotypeIII, NDV genotype VI and so on. The result also showed that the status of prevalence of ND in China is complex because NDV were isolated not only in domestic poultry but also in free birds.Some biological characteristics, such as mean death time (MDT) and 50% egg-infectious dose (ELD₅₀/ml), of A NDV strain isolated from one farm in Shandong province were measured. The special function region of the NDV named NDV042 were amplified by one step RT-PCR. The result of deduced animo-acid sequence showed that the cleavage site of the peptide was 112R-R-Q-K-R-F117 and has the characteristic of NDV genotype VII, that is K 101 and V 121. The results,accompanied by the MDT and ELD₅₀/ml, showed that the isolated NDV042 was velogenic and belongs to genotype VII which prevailing in China.40 SPF chickens were divided into two groups. Experimental group was vaccinated with La Sota vaccine, and the vaccinated 40-days old chickens were challenged with isolated NDV042 strain through eye and nose. Two experimental chickens were killed everyday after challenged. The NDV were isolated from selected organs including heart, liver, spleen, lung, kidney, brain, muscle, glandular stomach, faeces, and the antibody titer was measured by HI. The results showed that all the chickens of controlled group were died and all the chickens of experimental group were excellent at the 5th days post challenged. It is implied that La Sota vaccine could prevent chickens from the challenge of NDV genotype VII which prevailing in China. The velogenic and avirulent isolation result showed that velogenic NDV could be isolated in the glandular stomach at the third days post challenged, in the brain, grandular stomach and muscle at the seventh days post challenged, in the brain at the ninth and eleventh days post challenged.