| Carassius auratus gibelio is one of the main freshwater aquaculture fishes in east China and central China,the fry demand is large,and it has become the main production of many fish seedlings.In recent years,Thelohanellus wuhanensis caused many cysts on surface of fry of crucian carp is found in midle May every year,the disease has a wide popularity,high infection rate and cumulative mortality rates.the disease once occurs in the incubation pool,The difficulty in selling the fish and the large number of deaths of the fish have caused great economic losses.The disease was divided into four periods of occurrence,development,fade and disappearance according to whether there were immature spores and the degree of degenerated mature spores or not.To clear that four periods of Thelohanellus wuhanensis disease,and relevant measures for prevention and control of the disease and certain scientific basis,for the infection disease symptoms and fish cysts form,histopathology,nucleic acid detection and drug prevention and control of molecular biology experiment research.This study by naked eye and use a stered microscope of allogynogenetic crucian carp Thelohanellus wuhanensis infection after fish body formed by the occurrence and development of cysts,in the period of occurrence,diseased fish were no obvious abnormality in the behavior.Formed cysts were small and little uplift.The cysts on which there were no or few melanocytes were milk white in colour.In the period of development,number and size of cysts increased,The maximum diameter can reach at4 mm,The cysts were gray black in the colour due to the increase of melanocytes,The number of visible cysts is also increasing,the number of spores with high infection intensity of each fish is about 40,the cysts makes the scales that cover it appear to be erect or curved to varying degrees,Sometimes the cysts can make fish deformation,A large number of cysts will also absorb the nutrients of the diseased fish,which can make the fry slim down and swim hard,the serious disease fish will cause a large number of deaths.In the period of fade,cysts were shrinkage gradually in diseased fish,The atropal cysts reduce the space of melanocytes and make them darker and compacter,the cyst is relatively dark,diseased fish that can enter this period aregenerally no longer dead,feeding and growth of the fry is gradually restored.In the period of disappearance,cyst uplift was not obvious in diseased fish,the macroscopic view is almost flat deep black,the melanocyte gradually decreases and the original part of the cyst is light black to almost the normal color of the fish tissue,However,the lesion was identified by the naked eye,In late October,the lesion was completely disappeared and the diseased fish recovered fully.The pathology of Thelohanellus wuhanensis Results showed that in the period of occurrence,The cysts on which there were no or few melanocytes were milk white in colour.Trophozoites increased by profilication and no mature spores appeared in the cysts.In the period of development,mature spores appeared in the cysts.Number and size of cysts increased.The cysts were gray black in the colour duo to the increase of melanocytes.When all of immature spores became mature spores,the size of cysts reached maximum.Diseased fish with higher infection would be death or deformity.In the period of fade,mature spores reduced by flowing out into water through the ruptured gap of cysts or by degenerating gradually until all of them degenerated.At the same time,cysts shrunk and melanocytes were more dense gradually.In the period of disappearance,no mature spores and only degenerated materials were left in the flattened cysts.Melanocytes reduced gradually.Finally,the original part of cysts were replaced by connective tissue.This study not only for the first time to Thelohanellus wuhanensis by using the method of histopathological unipolar trypanosomiasis disease process is divided into four period of occurrence,development,fade and disappear,and reveals the Thelohanellus wuhanensis worm parts in four characteristics of the pathological changes of disease period,defined two ways of the disease fade and disappearance.One way was flow out of mature spores from ruptured cysts into water and another way discovered for the first time was degeneration of mature spores in the cysts.By using the analysis method of nested PCR,semi quantitative detection of the genetic material of acid in different stages of the whole disease process was carried out.Results showed that the 1584 bp and 853 bp in the first and second runs of nested PCR were respectively obtained in all of four periods of disease.However,in the late stage of the period of disappearance only 853 bp in the second run of nested PCR was obtained which illustrated that its quantity reduced.No bands were obtained after late October.Stage in the disease development and fading can detect the Thelohanelluswuhanensis insect DNA genetic material,and after the phase into the disappearance of the disease,with the passage of time,the remaining DNA genetic material gradually absorbed by the body to digest and content gradually reduce,especially the late disappearing stage,to detect the DNA genetic material,Especially in the later stages of the disease disappearing stage cysts in histopathological observation under the condition of less than spore residue,through the analysis of residual nested PCR nucleic acid substances,to further explore the parasite whether there is another life history approach has important significance.Gram bead and naphthenic acid copper and chlorobenzene guanidine hydrochloride is a drug with high character and broad-spectrum resistance in livestock production especially widely used in poultry breeding production,mainly because of the fish sticks spores in aquaculture disease prevention and control of,it is not seen in the different breeding silver on Thelohanellus wuhanensis insect disease prevention and control of relevant reports.In this study,a total of 28 days of laboratory prevention and control were carried out by 9 experimental drug groups of the three drugs.the results showed that The same disease period,nine diseased parts fish infected with drug experimental phenomenon of cysts size has shrunk,its surface black,known as a normal change phenomenon that lightens dark fading sick fish energetic is according to the group,in early August,nine drugs patients survived the original sick fish surface sporocyst basic fade,original sporocyst residual position only a small amount of melanin and lesions,while the control group of time also is in the midst of the peak,through early October,9 experimental drug group of fish have been restored to health,the body is no traces cysts,and there was no difference in the normal fish tissue,Compared with the control group,the control group had a certain control effect compared with the control group,the bead to g in the concentration of 0.9 ug/ml,1.8ug/ml and 2.7 ug/ml medicated bath for 7 days after drug withdrawal,to 28 days sick fish are the three drug test group to survive,survival rate is higher than the control group 70%,with good control effect,According to mix bait fish weight oral 7 days in a row,feeding respectively in ug/g 2 grams per day bead group and 0.08 ug/g chlorobenzene guanidine hydrochloride group and the control effect of the concentration is lower than 0.9 ug/ml,1.8 ug/ml and 2.7 ug/ml the bead of the dipping test,sick fish survival rates were higher than 20% in the control group,has the certain control effect;0.8ug /ml copper naphthenate and 1.2 ug/ml were better than 10% in thecontrol group.In addition,the survival rates of the dike beads and 0.16ug/g chlorobenguanide group of 4ug/g were lower than 10% and 65% respectively in the control group,indicating that the two experimental drug groups had no control effect on the disease. |
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