A Survey On The Prevalence And Genetic Relationship Of Sarcocystis In Pork And Beef From Guangxi And Yunnan Market

Objective:To describe the morphological characteristic of Sarcocystis from Guangxi province. To understand the prevalence of Sarcocystis in pork and beef from markets of Heng county, Rongshui county, Sanjiang county of Guangxi province and Kunming city, Dali city of Yunnan province. To search for the genetic relationship between the sarcocyst isolates from Guangxi and Yunnan.Methods:All samples were collected using random sampling. Pork and beef were collected from 7 towns of 3 counties in Guangxi and 7 farm product markets of 2 cities in Yunnan. The length and breadth of sarcocyst from Sanjiang county were measured and repeat frozen was done for positive samples and its morphological characteristic was recorded before and after frozen. All samples were examined using microscope and sarcocysts were collected from positive samples. The genomic DNA was extracted from sarcocysts.18S rRNA was selected as the DNA marker to amplify the target gene using PCR and the amplicon was sequenced with double sequencing method or A-T clone sequencing method; The sequences were aligned to sequences of closely sarcocyst isolates retrieved from Genbank, using the program CLUSTAL X. The analysis was carried out by Megalign application to evaluate their similarity, the distance matrixes were estimated by Kimura double parameter method and the phylogenic trees were built by minimum evolution (ME), neighbor joining (NJ), maximum parsimony (MP) methods with Mega 3.1, the bootstrap replicates were set to 1000.Results:The average size of 260 Sarcocystis suinominis is 917×84μm and that of 30 Sarcocyst hirsute is 1628×100μm. There is no significantly change of Sarcocyst with hairlike processus after 3 times frozen. The infection rates of suinominis and S.miesherian in the pork were 20.5% and 6.41%, respectively. The infection rates of S.hirsuta and sarcocyst crouzi in the beef were 44.44% and 33.33%, respectively. The average infection rate of Sarcocyst in pork and beef from Guangxi and Yunnan were 22.99% and 30.14%, respectively.The similarity and distance matrix of S.suinominis isolate between Bajiang, Linxi and Taixing, Dudong. Gongdong and Taixing, Luancheng and Taixing, Liangzhai and Taixing are 100 and 0.000,99.8 and 0.020,98.1 and 0.020,83.8 and 0.148,respectively. The similarity and distance matrix of S.hirsuta isolate between Liangzhai and Kunming are 93.8 and 0.067, respectively.Clearly, the similarity of these isolates is high and its distance matrix is small. These isolates have a very closely genetic relationship. In the phylogenetic trees, 10 isolates were separated into two branches.8 S.suinominis isolates in one branch, which can also be separated into two sub-branches, one for Liangzhai isolate and 7 for other, and 2 S.hirsuta isolates in another. Conclusion:The identification of Sarcocystis is not impacted by repeat frozen; The prevalence of Sarcocyst in pork and beef from Guangxi and Yunnan market were higher. There is a risk for local population to be infected by Sarcocyst. The Sarcocystis isolates from Guangxi and Yunnan were highly homologous and should belong to the same isolate.