Histotropism In SPF Chickens Infected Experimentally Of Newcastle Disease Virus Isolated From Two Kinds Of Host

Newcastle disease virus (NDV) cause a highly contagious respiratory, neurological, or entericdisease in chickens. Geese are infected with NDV in most areas in China since 1997, especiallyepizoonosis in East and South China, cause severe economic losses. Infected geese showed highoccurrence and mortality, which caused a huge loss in economy. We compared with the differencein the histotropism of HLJCF04 and F₄₈E₉ in SPF chickens. These experiment produced evidencefor difference between NDV isolated from goose and chicken.NDV HLJCF04-1 isolated from goose was purified by plague and cell virus harvested frominfected CEF, it was named HIACF04. HLJCF04's MDT was 59.6h, and the amino acid sequenceof fusion protein cleavage site was "RRQKRF", suggesting that HLJCF04 is a velogenic strain. Thepathogenic model was established by infecting experimentally 15-day old SPF chickens with10³EID₅₀ HLJCF04, with F₄₈E₉ as positive control group and PBS as negative control grouptogether. Every 3 chickens were randomly selected by experiment on 48h, 96h, 120h postinoculation. We have observed on the symptoms, pathological changes and obtainned brain,Harderian gland, trachea, lung, cecal tonsils and bursa of Fabricius from these chickens. EID₅₀ andreal-time RT-PCR methods were applied for dynamically getting titers of NDV HLJCF04 andF₄₈E₉.By observing, chickens challenged with HLJCF04 and F₄₈E₉ there appeared clinical symptomsat 24h post inoculation. Chickens challenged with HLJCF04 and F₄₈E₉ resulted in 100ï¼…occurrenceand mortality, suggesting HLJCF04 possed high pathogenicity for SPF chickens, similar withF₄₈E₉.The mean dead time of F₄₈E₉ was shorter than HLJCF04's, indicating HLJCF04 pathogenititywas weaker than F₄₈E₉.Samples were inoculated in 10-day-old SPF chichen embro for virus islation that wereacquired from chickens challenged with both HLJCF04 and F₄₈E₉ at 48h, 96h post inoculation. Allsamples were isolated for virus except brain inoculated HLJCF04 after 48h..Samples were determined by EID₅₀ and Real-time RT-PCR. Real-time RT-PCR assay fordetection of samples that correlated with EID₅₀. It indicated that titers of both HLJCF04 and F₄₈E₉in samples were accumulating increasing with infected time, highest titers were recorded at 120hpost inoculation generally. The results of EID₅₀: HLJCF04/120h/samples were 10^6.0, 10^5.7, 10^8.4, 10^9.3, 10^10.7, 10^7.2EID₅₀/0.1g and F₄₈E₉/120h/samples were 10^5.9, 10^5.3, 10^6.3, 10^7.5, 10^8.4,10^7.7EID₅₀/0.1g respectively. The results of Real-time RT-PCR: HLJCF04/120h/samples were1.18E+05, 3.00E+04, 3.68E+08, 4.88E+08, 1.76E+09, 4.14E+05copies/0.1g andF₄₈E₉/120h/samples were 1.15E+05, 8.04E+03, 2.12E+05, 1.71E+08, 2.22E+08,6.36E+06copies/0.1g.Overall, titers of HLJCF04 in trachea, lung, cecal tonsils and bursa of Fabricius were higherthan F₄₈E₉'s, in brain, but Harderian gland were less than F₄₈E₉'s. Accordingly titers differencedbetween HLJCF04 and F₄₈E₉, thus it is likely that HLJCF04 caused a neural syndrome that was aviscerotropic velogenic while F₄₈E₉ was a neurotropic velogenic.The pathogenic model was established by infecting 18-day old SPF ducks with 10³EID₅₀HLJCF04, resulted in 0 occurrence and mortality, obtainned brain, trachea, lung, cecal tonsils fromthese ducks. Real-time RT-PCR method was applied for dynamically getting titers of NDVHLJCF04 suggesting HLJCF04 is insensive with SPF ducks.