| Avian leucosis(AL)is an avian neoplastic disease caused by the avian leucosis virus(ALV)/Aviansarcomavirus(Aviansarcomavirus,ASV)group.In addition to causing tumors in poultry,it can also cause immune suppression..Pullorum disease(Pullorum disease)is a bacterial infectious disease caused by Salmonella pullorum(S.pullorum)in chickens.Pullorum disease seriously affects the performance of breeders and brings serious economic losses to chicken farms.The environmental pollution is also great.In chicken farms that are heavily polluted by Salmonella pullorum,the egg production rate,fertilization rate and hatching rate of the chicken flocks are at a low level,and the mortality rate of the chicken flocks is also significantly higher than that of the normal flocks.Avian leukemia and pullorum are two important chicken diseases mainly transmitted vertically.Up to now,the most effective prevention and control measures for the two diseases are pathogen detection,elimination of positive chickens,and population purification.This study mainly investigated the prevalence of different breeds of avian leukemia and pullorum in Huishui County,and provided relevant scientific evidence for the prevention and control of avian leukemia and pullorum in Huishui County.1.Epidemiological investigation of avian leukemia in Huishui CountyRandomly select 1-2 chicken farms in each town(street)from 11 towns(sub-districts)in Huishui County to investigate the breeding conditions and understand the past medical history;a total of 637 chicken serum samples from 17 chicken farms were collected The ELISA method was used to detect the p27 antigen of avian leukemia;the positive samples of ELISA were selected,and the nucleic acid was extracted for ALV subtype(A,B,J,K subtype)identification,and the prevalence of avian leukemia in Huishui County was explored.(1)The results of the ALV-p27 ELISA antigen test showed that the average positive rate of ALV-p27 antigen was18.21%(116/637)in the collected serum samples of 7 chicken breeds from 17 chicken farms in 11 towns(streets)in Huishui County.,The positive rates of ALV-p27 antigen of the 7 varieties were 50.00%(21/42)of Yaoshan chicken,23.58%(25/106)of Hailan gray,20.70%(59/285)of Roman,and 8.00%(4 /50),local native chicken7.50%(6/80),green shell layer 3.33%(1/30),K9 is 0(0/44);9 towns(streets)out of11 towns(streets)There is ALV infection,the highest positive rate is in Mengjiang Sub-district,with a positive rate of 51.79%(29/56);while the amount of poultry breeding in Mengjiang Sub-district has always been the largest,and it is located at the junction of our county and Guiyang,the risk of infection Is the biggest.(2)A total of39 positive samples were randomly selected from each of the 14 chicken farms that tested positive for ALV-p27,and a total of 39 positive samples were analyzed for ALV A/B/J/K subtypes.PCR and sequencing results showed that 14 of them were tested.ALV-K subtype was detected in 3 farms out of the chicken farms,the detection rate was 21.43%(3/14);the ALV-J subtype was detected in 1 farm,the detection rate was7.14%(1 /14);39 samples,13 of ALV-K subtype were detected,the detection rate was33.33%(13/39);ALV-J subtype was detected 2 samples,the detection rate was 5.13%(2/39);The two samples of the ALV-J subtype were all from the same field,and the ALV-K subtype was also detected in the two samples at the same time,indicating that there was a mixed ALV-J/K subtype infection in this field.;Among 11 towns(streets),3 towns(streets)were detected with ALV-K subtype,the detection rate was 27.30%(3/11),and 1 town(street)was detected with ALV-J subtype.The out rate was 9.00%(1/11).2.Epidemiological investigation of pullorum disease in Huishui CountyRandomly select 1-2 chicken farms in each town(sub-district)from 11 towns(sub-districts)in Huishui County to conduct an investigation of breeding conditions and past medical history.A total of 677 chicken serum samples from 17 chicken farms were randomly selected sample.Serum samples are tested for pullorum by plate agglutination test,and cotton swabs corresponding to samples with positive plate agglutination are subjected to bacterial isolation,culture,purification,biochemical test,PCR,sequencing analysis,and drug resistance analysis to grasp the prevalence of pullorum in Huishui County The situation has laid a solid foundation for the follow-up scientific prevention,control and purification of pullorum.The results showed:(1)The average positive rate of pullorum in chicken serum samples from 17 chicken farms in 11 towns(sub-districts)in Huishui County was 16.84%(114/677);the positive rates of pullorum in the 7 varieties were respectively Yaoshan chicken24.00%(12/50),K9 20.00%(10/50),local native chicken 17.28%(14/81),Roman17.04%(53/311),Hailan ash 16.19%(17/105)),green shell layer 10.00%(3/30),golden powder number 10.00%(5/50).(2)Microscopic examination of gram staining shows that the isolates are red microbacteria,indicating that the isolates are Gram-negative bacteria,arranged singly or in pairs,mostly rod-shaped with slightly rounded ends,small in shape,no spores,and no spores.Capsule and bacterial characteristics are consistent with those of Salmonella pullorum;the results of biochemical tests are negative for the isolated strain indigo substrate,urease,and potassium cyanide,and the results of biochemical tests for lysine decarboxylase,mannitol,sorbitol,ONPG It was positive,and the biochemical test results showed that the isolated strain conformed to the characteristics of Salmonella.(3)The 16 sr RNA PCR result showed a 1400 bp band consistent with the expected size.The 16 sr RNA PCR product sequence analysis and comparison results showed that the isolated strain was more than 90% similar to Salmonella.Comprehensive Gram staining microscopic examination,biochemical test,PCR and sequencing results showed that the isolated bacteria were all Salmonella.The results of drug susceptibility tests showed that the three isolates were sensitive to amoxicillin,cefaclor,compound trimethoprim and ampicillin,and were resistant to doxycycline.The test results provide a scientific basis for the scientific prevention and control of pullorum in Huishui County. |
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