Study On The Susceptibility Of Different Breeds Of Chickens And Turkeys To Histomonas Meleagridis Isolate

Histomoniasis(Histomoniasis)is caused by Histomonas meleagridis(H.meleagridis)of the genus trichomonas of gallinaceous birds,which is characterized by liver necrosis,cecal enlargement and sulfur-like feces.Turkeys,chickens,quails and peacocks are susceptible,with the highest morbidity and mortality in turkeys.Due to the food safety and public health concerns,most of the effective chemical drugs for the prevention and control have been banned,also there is no effective vaccine exsited,which leading to the epidemic of the disease more and more serious.With the continuous development of poultry industry in China,the disease has occurred to various degrees in many areas,and the mortality rate of chickens has reached 20-30%,which has caused great harm to the poultry industry.In this study,H.meleagridis was detected in the organs of clinical suspected cases,and the pathogenicity of two strains of H.meleagridis was compared.Four different breeds of chicken(Luhua chicken,Leghorn chicken,yellow feather broiler,Hy-Line Brown Hens)and turkey were infected with JSYZ-F strain through cloacal route,the differences of pathogenesis and cytokines of different breeds and turkeys were analyzed and compared.The main contents are as following:1.Detection and organ distribution of H.meleagridis in suspected clinical casesIn order to find out the distribution law of H.meleagridis in clinical diseased chickens,321 tissues and organs of 21 suspected diseased chickens were collected from Animal Hospital of yangzhou University.Using 18SRNA gene as target gene,PCR technique was used to detect the DNA of H.meleagridis in these samples.The results showed that the positive rates of liver and cecum in tissues and organs were 57.1%and 52.4%respectively,followed by ileum,spleen,kidney,myogastric,pancreas and brain.,with positive rates were 43.8%,40.0%,40.0%,37.5%,35.7%and 33.3%,respectively.The detection rates of heart,lung,bursa of Fabricius and other intestinal tissues were lower,no parasite was detected from gallbladder.In clinical samples,H.meleagridis mainly infected the target organs liver and cecum,followed by ileum,spleen,kidney,myogastric,pancreas and brain,and the distribution of H.meleagridis in other organs was less.2.Comparison of the virulence of JSYZ-F and JSYZ-G strains of H.meleagridisIn order to compare their pathogenicity,two H.meleagridis strains preserved in the laboratory(JSYZ-F,JSYZ-G)were used to infect the chicken.Hy-Line Brown Hens at 15 days of age were randomly divided into three groups.Two groups were infected with JSYZ-F and JSYZ-G,respectively.One group serves as unchallenged control.The infection dose was 2×105 cells per chicken.On 15 day post challenge,chickens were culled and weighed.The morbidity,mortality,body weight gain and lesion scores of liver and cecum were recorded and used to evaluated the virulence of the two H.meleagridis strains.The results showed that H.meleagridis JSYZ-F cause more typical signs than H.meleagridis JSYZ-G,and the relative weight gain rates of the two strains were 71.7%and 77.9%respectively,the average liver lesion score was 0.6 and 0.3,and the average cecal lesion score was 2.5 and 1.8 respectively.Altough no significant difference was founded between JSYZ-F and JSYZ-G strain,the JSYZ-F strain has a stronger virulence.3.Comparison of susceptibility of different breeds of chickens and turkey to H.meleagridisH.meleagridis JSYZ-F strain was used to infect different breeds of chickens and turkey through cloaca and culled regularly every 5 days(5,10,15,20,25 days).The morbidity and mortality,average weight,gross pathological changes,lesion scores of liver and cecum,histopatho logical changes of liver and cecum,dynamic distribution of H.meleagridis in vivo and cytokines levels were observed.The susceptibility of Luhua chicken,Leghorn chicken,yellow-feathered broiler,Hy-Line Brown Hens and turkey to H.meleagridis was compared and analyzed.The results showed that the morbidity and mortality from high to low were turkey,Leghorn chicken,Luhua chicken,Hy-Line Brown Hens and yellow feather broiler,in which the incidence rate of turkey was as high as 100%,and the mortality rate was 90%.On the 5th day post infection,the effect on the weight of turkeys was the greatest,which was significantly different from that of the control group(p<0.05).There was no significant difference in other groups,but there was a significant or very significant difference in the weight of different breeds of chickens and turkey compared with the control group at other time points post infection.The lesion scores of liver and cecum increased at first and then decreased in 5-25 days,and reached the highest in 10-15 days.The lesion scores from high to low of each group were turkey,Leghorn chicken,Luhua chicken,Hy-Line Brown Hens and yellow feathered broiler.The main histopathological changes of the liver were degeneration and necrosis of hepatocytes,disorder of hepatic cord,nuclear lysis or atrophy,infiltration of a large number of macrophages,lymphocytes and heterophils,and a large number of parasites in the liver tissue.The main histopathological changes of cecum were necrosis and exfoliation of cecal epithelial cells,presence of a large number of homogeneously red-stained H.meleagridis in the lamina propria,hyperemia of muscle layer and infiltration of inflammatory cells in different degrees.The severity of histopathological changes in liver and cecum at each time point was highly consistent with the morbidity and mortality of different breeds of chickens and turkey.The results of the distribution of detection rate in various organs showed that at different time points post infection,the detection rate of liver and cecum was the highest,followed by intestinal tissue,spleen,kidney,lung and heart.The detection rate of pancreas,thymus,bursa of Fabricius and reproductive organs was lower,and the detection rate of organs at each time point was consistent with the morbidity and mortality of different breeds of chickens and turkey.The results of cytokine detection showed that the level of IFN-γ in turkey was significantly higher than that in other breeds at 5-10 days after infection,and decreased significantly after 15 days,while that in other breeds increased from 5 to 20 days post infection and began to decrease at 25 days,which had no significant correlation with morbidity and mortality,while the levels of IL-2 and IL-4 had no significant correlation with breeds.The levels of IL-10 in all breeds and turkey were basically the same,and there was no significant increase or decrease.To sum up,the susceptibility of different breeds of chickens and turkey to H.meleagridis from high to low is turkey,Leghorn chicken,Reed chicken,Hy-Line Brown Hens and yellow feather broiler.The above studies further explore the pathogenesis of the disease,provide some reference for the selection of animal models for the development of drugs and vaccines for Histomoniasis,and provide new ideas for the prevention and control of Histomonasis.