Research In Histomonas Meleagridis Experimentally Infected Yellow-feather Broilers

Histomonas meleagridis (H. meleagridis) is a pleomorphic sizes of parasite causing histomoniasis, a common parasitic disease. Histomoniasis also called infectious cecum hepatitis or blackhead disease. This disease mostly occurs in turkeys and chickens, which also in popular in Guinea fowl, quail and peacock. Histomoniasis is characterized by ulceration, enlargement and embolism of the cecum, white or yellow green round necrotic lesions in the liver. The disease often leads to a higher incidence and mortality in turkeys, causes serious economic losses, does some harm in the chicken industry. For a long time, China has been lacked of systematic and detailed study of Histomoniasis. This study carried out the research of H. meleagridis experimental infection of yellow-feather broilers, discussed the pathogenesis of Histomoniasis, laid a foundation for the further research of new drugs development and histomoniasis prevent.1. Cloning and phylogenetic analysis of the beta-tubulin gene sequences of H. meleagridis in Jiangsu Province.To identify the taxonomic status and characteristic of H. meleagridis in Jiangsu Province. Eleven liver materials of chickens which diagnosed as H. meleagridis infection were collected, sequences of the H. meleagridis beta-tubulin gene were obtained by polymerase chain reaction, cloning and sequencing. The homology of beta-tubulin gene was analyzed and the phylogenetic tree was constructed. The beta-tubulin gene sequences of H. meleagridis in Jiangsu Province were conserved, with nucleotide sequence identity of 95.3%-100.0%. Further phylogenetic analysis revealed these sequences were clustered into two main groups and several secondary groups. The results showed that different genotypes of H. meleagridis were existed in Jiangsu Province, further researches on the molecular diagnosis and molecular epidemiology are needed.2. Comparison of the virulence of different H. meleagridis isolates.In order to compare their pathogenicity, two H. meleagridis strains preserved in the laboratory (JSYZ-A,JSYZ-B) were used to infect the chicken. Thirty yellow-feather broilers at 15 days of age were randomly divided into three groups. Two groups were infected with JSYZ-A and JSYZ-B, respectively. One group serves as unchallenged control. The infection dose was 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 a significant difference was founded between JSYZ-A and JSYZ-B strain and the JSYZ-A strain has a stonger virulence.3. The dynamic distribution of H. meleagridis in yellow-feather broilers.In order to research the dynamic distribution of H. meleagridis in yellow-feather broilers after infection.15 days old yellow-feather broilers were cloaca infected with JSYZ-A strains. At days 7-31 post-infection,5 chickens were slaughtered every third day and 12 different organs tissue were collected and detected by PCR and pathology analysis. The results showed that H. meleagridis was usually detected in the cecum and liver from the 7 days post infection and occasionally appeared in the heart, duodenum, jejunum, lung, spleen, bursa, proventriculus, rectum. However, it has not been found in the pancreas and brain tissue. The persisten infection was only detected in cecum and liver. The liver and cecum lesions reached the biggest value at 10-16 days and decreased after 19 days. The results of PCR were basically consistent with the results of pathological analysis. The results indicated that liver and cecum were the major target organs of H. meleagridis rather than the only organs. The route of infection remains to be further studied.4. Analysis of physiological and biochemical indicators in yellow-feather broilers infected with H. meleagridis.In order to further explore the mechanism of pathogenicity of H. meleagridis,15 days old yellow-feather broilers were cloaca infected with JSYZ-A strain and then set up a control group. At days 7-31 post-infection,5 chickens were slaughtered, weighed, analyzed bio-chemical of blood every third day. The result indicated that H. meleagridis would lead the chicken lose weight. H. meleagridis infection would lead to a series of related biochemical indicators of liver function disorder, such as ALT, AST, GGT, GLB, BUN, GLU, TG. In conclusion, the results of the present study provided a reference for subsequent research on the prevention and treatment of drug avian histomoniasis.