Attempts to control Ichthyophthirius multifiliis Fouquet (Ciliophora: Ophryoglenidae) by chemotherapy and electrotherapy

Abstract. New methods were studied for the control of Ichthyophthirius muttifiliis Fouquet, one of the most serious parasites of fish. Totals of 272 fish, 354 I. Multifiliis trophozoites and 562,500 tomites were used in the screening of amprolium, ronidizole, and silver nitrate for parasite control. In addition, 1,465 trophozoites and 600 tomites were subjected to pulsed DC electrotherapy trials. Silver nitrate at 0·67 ppm was 100% effective in eradicating tomites, while ronidizole at 750 ppm gave 100% and 97% control of trophozoites and tomites, respectively. Amprolium and electrotherapy were both ineffective against trophozoites and tomites. Silver nitrate has promise as a safe and effective alternative to chemicals currently used to control I. multifiliis .     

Apoptosis in Ichthyophthirius multifiliis is associated with expression of the Fas receptor of theronts

The expression of type I membrane Fas receptors on the surface of Ichthyophthirius multifiliis (Ich) theronts and the possible association between Fas expression and theront apoptosis induced by the immune antibody was examined. Fas receptors were detected on the theront surface using fluorescein isothiocyanate-conjugated mouse monoclonal antibody against Fas. Fas-positive theronts significantly increased with time during in vitro incubation and with increasing theront concentration. Furthermore, the immune cutaneous antibody induced theront apoptosis; however, Fas ligand did not. A highly significant correlation was noted between theront Fas expression and immune cutaneous antibody-induced theront apoptosis. Numbers of apoptotic theronts increased with increasing number of Fas-positive theronts. The data indicated that theront apoptosis induced by immune cutaneous antibody appears to be positively correlated with the expression of Fas on the surface of Ich theronts.     

Two in vitro methods for screening potential parasiticides against Ichthyophthirius multifiliis using Tetrahymena thermophila

Ichthyophthirius multifiliis (Ich) is a ciliate parasite that infects many species of freshwater fishes worldwide and causes heavy economic losses in aquaculture. Currently, parasiticides for controlling this parasite are limited, and few pond‐practical chemical therapies exist. Hence, the search for new parasiticides is urgently needed. One challenge confronting the screening of potential parasiticides is the difficulty in raising enough parasite for efficacy testing as Ich is an obligate parasite. This study used species of Tetrahymena, Ich‐related and cultivable ciliate protozoa, to evaluate two in vitro methods to test parasiticides. Plate counting and MTS assays (CellTiter 96^® AQ_ueous Non‐Radioactive Cell Proliferation Assay) were used to compare lethal concentrations or median lethal concentrations (LC₅₀) of copper sulphate, formalin and malachite green between T. thermophila and Ich theronts or between T. thermophila and Ich tomonts. The parasiticides that killed T. thermophila have been demonstrated to kill theronts or tomonts. These in vitro methods using T. thermophila can be used to screen novel parasiticides against Ich.     

刺激隐核虫与多子小瓜虫免疫学特性比较研究综述

刺激隐核虫(Cryptocaryon irritans)与多子小瓜虫(Ichthyophthirius multifiliis)是影响渔业生产重要寄生虫,本文主要阐述了刺激隐核虫与多子小瓜虫种内和种间的免疫学相似性和差异性,及其两种寄生虫抑动抗原的免疫学特性以及克隆表达研究。为免疫学方法预防两种寄生虫病提供理论依据。     

Ultraviolet light control of Ichthyophthirius multifiliis Fouquet in a closed fish culture recirculation system

Abstract. A closed fish culture recirculation system consisting of 36 20-gallon aquaria in series with a rotating plate biofilter, a diatomaceous earth filter, and an ultraviolet (UV) light sterilizer was evaluated for the effectiveness of UV light in preventing spread of Ichthyophthirius multifiliis . Water from the aquaria, the reservoir, and a valve 29 cm beyond the UV light source was analysed bacteriologically to assess its effectiveness. The spread of I multifiliis from one aquarium to another was controlled with 91 900 μW s/cm⁸ of UV light. No significant differences in the bacterial counts from the water of the reservoir or the aquaria could be demonstrated when the UV light was either on or off, although a significant difference could be demonstrated between the sterilizer effluent and the reservoir and aquaria.     

Ichthyophthirius multifiliis: standardization of the infection-response model in Ameca splendens (Miller & Fitzsimons)

Abstract. The goodeid fish Ameca splendens (Miller & Fitzsimons) was exposed to the parasite Ichthyophthirius multifiliis . Exposure levels were 2000,3000,6000 and 12000 theronts per fish. After 3 days, infection levels were determined and the body area of the fish was measured. A rise in the number of trophozoites per fish was observed, up to a level of 6000 theronts per fish. Standardization of infection and response by area, to theronts per square centimetre and trophozoites per square centimetre respectively, produced a significant linear relationship, up to an exposure of 2800 theronts per square centimetre, and also removed the between-tank within-dose variation. The measures of controlling exposure to 1. multifiliis and evaluating response in previous research are reviewed. Adoption of the technique described here will facilitate the collation of research on ichthyophthiriasis by permitting comparisons of different studies utilizing different sizes and species of fish.     

四氢异喹啉衍生物的合成及体外抗多子小瓜虫活性的研究

合成四氢异喹啉衍生物并进行杀多子小瓜虫(Ichthyophthirius multifiliis)药效评价。以1-甲基-1,2,3,4-四氢异喹啉为起始原料,在2位的胺基上引入与环己甲酰氯、苯甲酰氯、噻吩甲酰氯、乙酰氯以及氯乙酰氯等不同的酰基进而合成5种四氢异喹啉衍生物(化合物1~化合物5),研究其对小瓜虫掠食体和包囊的杀虫活性,并对杀虫活性物质进行安全性评价。结果显示,5种化合物均具有一定的杀虫活性,其中,化合物1 [(1-甲基-3,4-二氢异喹啉-2(1H)-基)-苯基-甲酮]的杀虫活性最强,其对多子小瓜虫掠食体4 h的100%杀灭浓度为24.0 mg/L,对包囊6 h的100%杀灭浓度为60.0 mg/L,对掠食体的半数致死浓度(LD₅₀)为16.4mg/L。急性毒性实验结果显示,化合物1对翘嘴红鲌(Erythroculter ilishaeformi)的48 h LD₅₀为234.3 mg/L,其安全浓度为64.1 mg/L。研究表明,化合物1[(1-甲基-3,4-二氢异喹啉-2(1H)-基)-苯基-甲酮]是一种具有较好开发前景的杀小瓜虫药物。     

四氢异喹啉衍生物的合成及体外 抗多子小瓜虫活性的研究

合成四氢异喹啉衍生物并进行杀多子小瓜虫(Ichthyophthirius multifiliis)药效评价。以1-甲基-1,2,3,4-四氢异喹啉为起始原料,在2位的胺基上引入与环己甲酰氯、苯甲酰氯、噻吩甲酰氯、乙酰氯以及氯乙酰氯等不同的酰基进而合成5种四氢异喹啉衍生物(化合物1~化合物5),研究其对小瓜虫掠食体和包囊的杀虫活性,并对杀虫活性物质进行安全性评价。结果显示,5种化合物均具有一定的杀虫活性,其中,化合物1 [(1-甲基-3,4-二氢异喹啉-2(1H)-基)-苯基-甲酮]的杀虫活性最强,其对多子小瓜虫掠食体4 h的100%杀灭浓度为24.0 mg/L,对包囊6 h的100%杀灭浓度为60.0 mg/L,对掠食体的半数致死浓度(LD50)为16.4 mg/L。急性毒性实验结果显示,化合物1对翘嘴红鲌(Erythroculter ilishaeformi)的48 h LD50为234.3 mg/L,其安全浓度为64.1 mg/L。研究表明,化合物1 [(1-甲基-3,4-二氢异喹啉-2(1H)-基)-苯基-甲酮]是一种具有较好开发前景的杀小瓜虫药物。     

Mechanical control of Ichthyophthirius multifiliis Fouquet, 1876 (Ciliophora) in a rainbow trout hatchery

Ichthyophthirius multifiliis, more commonly known as ‘white spot’ is recognised as one of the most pathogenic diseases of wild and cultured freshwater fish. In trout hatchery systems infections can quickly establish and result in high mortality if left unregulated. Current control centres around the use of regular bath treatments with formalin, however, treatments are not always effective and are labour intensive. Environmentally safe, non-chemical alternatives are required. This paper describes the performance of a mechanical system developed to remove cysts from commercial trout raceways. The system consists of two parts: a specially designed suction head connected to a pump that is used to vacuum the bottom of hatchery raceways, and a low-adhesion polymer raceway lining. Following tests on a series of potential linings, the most efficacious product in preventing settlement of cysts was used to line three raceways in a commercial rainbow trout (Oncorhynchus mykiss) hatchery. Over a period of three months, lined raceways were vacuumed on a daily basis. The three control raceways were maintained according to the farms normal husbandry procedures. Approximately thirty fish were sampled from each raceway at fortnightly intervals, and the abundance of the parasite in each raceway determined. The mechanical system led to a significant reduction in the abundance of the parasite in the test raceways, with a mean abundance of 361.88 ± 260.75 parasites per fish in control raceways compared with 1.64 ± 1.59 parasites per fish in the test raceways at the peak of the infection. Additionally fish survival was significantly higher in test raceways over control, with a mean of 84.5% of the stock surviving in the test raceways compared with only 70.6% in the controls by trial end.     

Mechanical control of Ichthyophthirius multifiliis Fouquet, 1876 (Ciliophora) in a rainbow trout hatchery

Ichthyophthirius multifiliis, more commonly known as ‘white spot’ is recognised as one of the most pathogenic diseases of wild and cultured freshwater fish. In trout hatchery systems infections can quickly establish and result in high mortality if left unregulated. Current control centres around the use of regular bath treatments with formalin, however, treatments are not always effective and are labour intensive. Environmentally safe, non-chemical alternatives are required. This paper describes the performance of a mechanical system developed to remove cysts from commercial trout raceways. The system consists of two parts: a specially designed suction head connected to a pump that is used to vacuum the bottom of hatchery raceways, and a low-adhesion polymer raceway lining. Following tests on a series of potential linings, the most efficacious product in preventing settlement of cysts was used to line three raceways in a commercial rainbow trout (Oncorhynchus mykiss) hatchery. Over a period of three months, lined raceways were vacuumed on a daily basis. The three control raceways were maintained according to the farms normal husbandry procedures. Approximately thirty fish were sampled from each raceway at fortnightly intervals, and the abundance of the parasite in each raceway determined. The mechanical system led to a significant reduction in the abundance of the parasite in the test raceways, with a mean abundance of 361.88 ± 260.75 parasites per fish in control raceways compared with 1.64 ± 1.59 parasites per fish in the test raceways at the peak of the infection. Additionally fish survival was significantly higher in test raceways over control, with a mean of 84.5% of the stock surviving in the test raceways compared with only 70.6% in the controls by trial end.     

20种中草药杀灭离体小瓜虫的药效研究

选用20种不同中草药,研究其不同浓度的水提物对多子小瓜虫(Ichthyophthirius multifiliis)成虫、包囊和幼虫的离体杀灭实验效果。结果显示:0.1 g/L槟榔和乌梅对各个阶段的虫体均有杀灭效果,0.1 g/L大黄和黄芩1 h内对幼虫有杀灭效果,1.0 g/L浓度能杀灭成虫和包囊,表明槟榔、乌梅、大黄、黄芩的杀虫效果相对较好;贯众、乌药、枳壳等13种中药浓度达到10 g/L、50 g/L或100 g/L才具有一定杀虫作用,但效果不很显著;熟地黄、茯苓和黄芪即使浓度达到100 g/L时,也不能杀灭虫体。     

Cutaneous antibodies in excised skin from channel catfish, Ictalurus punctatus Rafinesque, immune to Ichthyophthirius multifiliis

This study determined whether cutaneous antibodies were present in the excised skin of channel catfish, Ictalurus punctatus Rafinesque, immune to Ichthyophthirius multifiliis Fouquet (Ich). Theronts were immobilized on or near the excised skin from immune fish. The survival of immobilized theronts was significantly reduced after exposure for 8 h to the culture of excised skin from immune fish. Culture fluids from excised skin of immune fish immobilized theronts with a peak in the immobilization titre at 24 h post-exposure. Immobility of theronts in the culture fluid from immune skin was removed after immunoabsorption with theronts. Indirect immunofluorescent staining of theronts treated with culture fluid from excised skin of immune fish revealed strong and uniform fluorescence on the cilia and cell surface of theronts. Western blot analysis of the culture fluid from immune fish revealed a 70-kDa band which corresponded to the molecular weight of catfish immunoglobulin heavy chain. The results of this study show that cutaneous antibodies to Ich theronts were present in and released from the excised skin from fish immune to Ich. Immobilization and killing of the theronts are two characteristics of the antibody response that appear to prevent the successful invasion of theronts into excised skin.     

Induced cross-protection in channel catfish, Ictalurus punctatus (Rafinesque), against different immobilization serotypes of Ichthyophthirius multifiliis

Abstract Channel catfish, Ictalurus punctatus (Rafinesque), were immunized with Ichthyophthirius multifiliis (Ich) theronts and trophonts, and the immune response and host protection against both homologous and heterologous serotypes of Ich were evaluated. Immunizations were done with two immobilization serotypes (ARS4 and ARS6) of live theronts by bath immersion (trial I) and with sonicated trophonts by intraperitoneal (i.p.) injection (trial II). Cutaneous and serum antibody titres against Ich following immunization were measured and survival of catfish was determined after theront challenge. Theronts were immobilized by the antiserum from fish immunized with homologous theronts or trophonts, but not by the serum of fish immunized with the heterologous serotype. Serum from fish immunized by immersion with live theronts showed higher enzyme-linked immunosorbent assay titres against both homologous and heterologous serotypes than fish immunized by i.p. injection of trophonts. Channel catfish immunized by immersion with live theronts or by i.p. injection with sonicated trophonts developed an immune response against Ich and provided cross-protection against challenge from both serotypes (ARS4 and ARS6) of the parasite. Sonicated trophont antigens in aqueous solution by i.p. injection could stimulate an immune response in fish, but the immunity was of short duration.     

滇池金线鲃、西畴金线鲃及其杂交F1代抵抗小瓜虫与车轮虫能力的探究

用小瓜虫(Ichthyophthirius multifiliis)和车轮虫(Trichodina spp.)对滇池金线鲃(Sinocyclocheilus grahami)和西畴金线鲃(S.xichouensis)及其杂交F1代分别进行了两次人工感染实验。18月龄的杂交F1代、滇池金线鲃(Sinocyclocheilus grahami)和西畴金线鲃(S.xichouensis)感染小瓜虫后平均死亡率分别为(50.00±11)%、(56.70±23)%、(80.0±18)%。经方差检验杂交F1代死亡率显著低于父本西畴金线鲃。6月龄杂交F1代、滇池金线鲃、西畴金线鲃感染车轮虫后的平均死亡率分别为(40.56±13)%、(56.11±5)%、(42.78±13)%。经方差检验杂交F1代死亡率显著低于母本滇池金线鲃。在感染小瓜虫和车轮虫后,三种鱼的死亡量均呈现激增后又显著回落的趋势,死亡高峰在第4天至第7天。本次感染实验的小瓜虫和车轮虫主要分布于病鱼体表:躯干分布最多57%~79%,其次为鳍12%~28%,头部分布较少4%~15%。与本研究中车轮虫几乎于鳃丝无分布(0%~3%)不同,有大约10%~20%的小瓜虫分布于鳃丝上。     

Effects of Water pH and Hardness on Infection of Silver Catfish,Rhamdia quelen,Fingerlings by Ichthyophthirius multifiliis

The aim of this study is to determine the effect of (1) different pH levels (5, 6, 7, 8, and 9) with water hardness 20 mg/L CaCO₃ and (2) pH 5 and 7 with varying water hardnesses (20, 60, and 120 mg/L CaCO₃) on the intensity of infection by Ichthyophthirius multifiliis in fingerlings of the silver catfish, Rhamdia quelen. In Experiment 1, the lowest and highest mortality rates were observed in fingerlings exposed to pH 5 and 9, respectively; in Experiment 2, fish kept at pH 5 and 7 with hardness 20 mg/L CaCO₃ showed significantly lowest and highest cumulative mortality, respectively, than those maintained in other conditions. The lowest intensity of trophonts/fingerling was observed at pH 5 and hardness 20 mg/L CaCO₃ in both experiments. We conclude that infection by I. multifiliis is less severe in silver catfish maintained at pH 5 and hardness 20 mg/L CaCO₃. High water hardness led to an increased intensity of trophonts and decreased survival in silver catfish kept at pH 5, but decreased intensity of trophonts and improved survival when the fish were kept at pH 7.     

Immunization of channel catfish, Ictalurus punctatus Rafinesque, against Ichthyophthirius multifiliis (Fouquet): killed versus live vaccines

Abstract. Fish surviving infection with the pathogenic ciliated protozoan, Ichthyophthirius multifiliis (Fouquet, 1876), become resistant to subsequent infection by the parasite. The acquired immunity suggests that development of a vaccine against the parasite may be possible. Because of the advantages of immunoprophylaxis for treatment of the disease, an effort has been made to determine whether fish exposed to killed parasite preparations can resist subsequent lethal challenge. Both the route of administration and the effects of stage specific antigens have been examined. Channel catfish vaccinated by intraperitoneal (i.p.) injection or bath immersion with killed I multifiliis tomites show 100% mortality following a standard challenge protocol. Similarly, 100% mortality was observed in test groups injected with tomite cilia. In both cases, a consistent difference in days to death between control and test group animals was observed. Although complete mortality was seen with fish injected with tomite preparations, fish vaccinated with killed trophonts (the feeding stage of the parasite) had a much greater degree of protection with approximately 50% of fish surviving an otherwise lethal challenge. Finally, animals injected intraperitoneally with live tomites showed nearly complete immunity and were identical in their response to fish which survive natural infection. The response of fish vaccinated with live parasites indicates that animals injected intraperitoneally can develop surface immunity and that i.p. injection is a suitable route of administration for potential I. multifiliis vaccines.