Investigation On The Current Status And The Infection Rate Of Pleroceroid Of Snake Farming Industry In Guizhou Province

Objective: To discuss the current status and development strategy of snake farming industry,and to investigate the epidemic risk of pleroceroid in Guizhou province.Methods:(1)18 snake farms were selected with stratified cluster sampling method as the object of investigation.The field and questionnaire survey were carried out on the basic situation(distribution,size,investment,quality of personnel),breeding situation(culture technology,snake sort,amount,and source),sales situation and awareness rate of snake pleroceroid disease of the 18 farms.(2)The investigation were carried out on the pleroceroid infection rate in artificial breeding snakes,and the pathological damage of the pleroceroid to the snake tissue was observed.(3)Plerocercoids were isolated from the artificial breeding snakes.The mitochondrial cyclooxy-genase 1(cox1)gene of the plerocercoids were amplified by PCR,and the sequences were measuted.Comparing 4 sequences with KJ418421,(a Guizhou wild strain)by Clustalx1.81,the molecular identification of isolated pleroceroid strains were made.Results:(1)There are about 70 breeding snake farms in Guizhou province,which are distributed in 3 states,and 6 cities.A results of 18 farms showed that farms had the characteristics of small scale,insufficient funds,backward management,low staff quality,weak scientific research,and small market share and so on.(2)The survey found that workers’ awareness of pleroceroid disease was generally low.Of the 8 problems,5 were less than 20%.The formation rates of 6 unhealthy lifestyles and dietary habits,2 were over 20%.(3)Among 50 snakes examined,44%(22/50)were infected with pleroceroids in the rang of 2-25 worms per affected snake.The positive snakes were bought form wild field for breeding snakes.(4)The pleroceroids settled down mainly subcutaneous tissue(46.1%,212/460),muscle tissue(38.0%,175/460)and body cavity(15.9%,73/460).The pathological status of pleroceroids found in snakes were calssified as free,encapsulated and degenerative stages.The reaction of snake muscular tissue infected by free stages was quite mild revling only simple compression of surrounding tissue and a few neutrophile leucocyte infiltration.The some worms were encapsulated by thin and delicate fibrous tissue.The cyst wall contained a few acute inflammatory cells and the worms in cyst were activity.The cyst size of degenerative stage was usually smaller than that of encapsulated stage.Microscopically the degenerative stage had a thick fibrous wall with mainly lymphocytes,the pleroceroids in degenerative cyst were replaced gradually by necrotic tissue of structureless worms and amorphous materials with infective time extending.(5)The cox1 gene sequences of 4 pleroceroid strains were identified.Compared with KJ418421,the similarity of sequences was 95.66%-97.96%,while the two isolates were compared with each other,the homology was over 97%.Conclusion: The development of the artificial breeding snake industry in Guizhou is at the initial stage.Breeding snakes have occurred pleroceroid infection,so there is a security risk.After molecular identification,the isolated strains from breeding snakes were pleroceroids of S.erinacei.