Epidemiological Investigation On IBR,BPI3 And BRS Of Calves In Intensive Cattle Farms In Xinjiang

Bovine respiratory disease complex(BRDC)is the main cause of bovine respiratory disease and death all over the world.Cattle infected with BRDC will have symptoms such as fever,shortness of breath,repeated cough,runny nose or tears,diarrhea,dehydration and loss of appetite,which will cause great damage to the health and daily production of cattle and seriously hinder the sustainable development of cattle industry.Infectious bovine rhinotracheitis virus(IBRV),bovine parainfluenza virus type 3(BPIV3)and bovine respiratory syncytial virus(BRSV)are three major viral pathogens causing BRDC.At present,there are few relevant research reports on IBRV,BPIV3 and BRSV in Xinjiang,especially in calves.Therefore,relevant research on IBRV,BPIV3 and BRSV of calves in intensive cattle farms in Xinjiang is carried out to provide scientific basis for the prevention and control of the disease.In this study,407 calf nose swab samples collected from 14 intensive cattle farms in Shihezi,Tacheng,Urumqi,Karamay,Bazhou,Aksu and Ili of Xinjiang were detected by nested PCR and RT-PCR,and the positive samples of BRSV F gene were genotyped by G.M gene and G gene were used for homology comparison and genetic evolution analysis of BPIV3 and BRSV.The results showed that the average positive rates of IBRV,BPIV3 and BRSV in Xinjiang cattle farms were 10.57%(43/407),6.14%(25/407)and 4.18%(17/407),respectively.Among them,the highest positive rate of IBRV in Urumqi a farm was80.00%(20/25),the highest positive rate of BPIV3 in Shihezi farm was 22.73%(5/22),and the highest positive rate of BRSV in Shihezi J farm was 51.90%(14/27).After homology comparison,the homology of7 sequences of SHZ001 ～ 007 with Australian Q5592 reference strain of genotype B(EU277658.1)was88.8%～91.1%,the homology of 18 sequences of TC001,TC002 and SHZ008 ～ 023 with Ningxia NX49 reference strain of genotype C(KT071671.1)was 92.6%～97.5%,and the homology of 17 sequences of YL001,YL002 and SHZ001 ～ 015 with BRSV III subgroup reference strain USII/S1(KU159366.1)from the United States was 91.6%～94.4%.Genetic evolution analysis showed that BPIV3 positive samples had two genotypes B and C,and BRSV positive samples were subgroup III.380 calf serum samples from 13 intensive farms in Shihezi,Tacheng,Urumqi,Karamay,Bazhou and Aksu of Xinjiang were detected by Enzyme-linked immunosorbent assay(ELISA).The results showed that the average positive rates of calf IBRV and BRSV antibodies were 70.26%(267/380)and 80.79%(307/380)respectively,and the average positive rate of double positive antibody was 62.11%(236/380).The positive rate of antibody in six regions of IBRV was 35.59% ～ 100.00%,among which Bazhou and Karamay had the highest positive rate of 100.00%,and Aksu had the lowest positive rate of 35.59%;The positive rate of antibody in six regions of BRSV is 70.00% ～ 100.00%,of which Karamay has the highest positive rate of100.00% and Shihezi has the lowest positive rate of 70.00%.Twenty BPIV3 positive samples were isolated by MDBK cells.After 72 hours of culture,9 samples showed obvious cytopathic changes.They were identified as BPIV3 by RT-PCR amplification and sequencing.The IFA test of XJ21032-1 and XJ20055-3 isolates showed that they could react with BPIV3 polyclonal antiserum to produce specific green fluorescence.The morphological observation of XJ21032-1and XJ20055-3 isolates showed that they were similar to paramyxovirus.Genome sequencing using high-throughput sequencing technology.Through homology comparison,it was found that the homology between XJ21032-1 isolate and Australian reference strain Q5592 was 93.4%,and that between XJ20055-3isolate and Ningxia reference strain NX49 was 99.6%.Genetic phylogenetic tree analysis showed that XJ21032-1 isolate was B genotype and XJ20055-3 isolate was C genotype.The infection of IBRV,BPIV3 and BRSV is common in the calves of intensive cattle farms in Xinjiang,and there is a phenomenon of mixed infection.BRSV is mainly subgroup III,while BPIV3 has two genotypes of B and C,mainly type C.This is also the first report of BPIV3 B genotype strain in China,which proves the existence of B genotype in China.This study provides data support for the prevention and control of IBRV,BPIV3 and BRSV and subsequent vaccine research and development.