Effects of Formalin and Chloramine-T Treatments on Oxygen Consumption of Juvenile Salmonids

Abstract

The effects of formalin and chloramine-T on oxygen consumption of juvenile brook trout Salvelinus fontinalis at low water temperature were studied with a flow-through respirometer. No changes were found in the oxygen consumption of these fish after exposure to formalin at 200 and 400 μL/L or to chloramine-T at 10 μL/L during 1-h flow-through treatments. Additionally, there was no evidence of chemical oxygen demand exerted by formalin at dose levels up to 1,600 μL/L or by chloramine-T at I0 μL/L. When juvenile rainbow trout Oncorhynchus mykiss were treated with formalin at 200 μL/L for 1 h in an aerated tank simulating a static bath treatment, sham-treated control tanks had a significantly greater maximum decline in dissolved oxygen than formal in-treated tanks. These studies suggest that posttreatment mortalities that occur after low-temperature bath treatments with these chemicals are not directly related to oxygen consumption.     

The Effect of High Concentrations of Iron on Impounded American Lobsters: A Case Study

Abstract

Iron precipitates are reported from American lobsters Homarus americanus held in cold saline water of high iron concentration (11.0 mg/L). Upon aeration, an insoluble ferric oxide precipitate or hydroxide precipitate (or both) formed and was deposited within the carapace matrix and the gills, occluding the respiratory lamellae. Clinical signs included a darkened carapace and lethargy.     

Safety of florfenicol in the adult lobster (Homarus americanus)

Aerococcus viridans, the causative agent of the disease gaffkemia, was a major cause of mortality in lobsters (Homarus americanus) held in tidal impoundments during the 1970s and 1980s. Despite reports of an increase in the mortality of lobsters during impoundment, and the widespread prophylactic use of oxytetracycline against A. viridans, this bacterium has not been detected in active disease surveillance of the Maine postcapture lobster population. However, Photobacterium indicum may be an emerging opportunistic pathogen of stressed lobsters. An acute toxicity trial was conducted as a rapid screening procedure for the potential future use of the antibiotic florfenicol. Based on the results of this experiment, florfenicol appears to be well tolerated in adult H. americanus by intrapericardial injection at the 10-100 mg/kg dose. Oxytetracycline dihydrate is contraindicated by intrapericardial injection at the 10-100 mg/kg dose.     

Host susceptibility hypothesis for shell disease in American lobsters

Epizootic shell disease (ESD) in American lobsters Homarus americanus is the bacterial degradation of the carapace resulting in extensive irregular, deep erosions. The disease is having a major impact on the health and mortality of some American lobster populations, and its effects are being transferred to the economics of the fishery. While the onset and progression of ESD in American lobsters is undoubtedly multifactorial, there is little understanding of the direct causality of this disease. The host susceptibility hypothesis developed here states that although numerous environmental and pathological factors may vary around a lobster, it is eventually the lobster's internal state that is permissive to or shields it from the final onset of the diseased state. To support the host susceptibility hypothesis, we conceptualized a model of shell disease onset and severity to allow further research on shell disease to progress from a structured model. The model states that shell disease onset will occur when the net cuticle degradation (bacterial degradation, decrease of host immune response to bacteria, natural wear, and resorption) is greater than the net deposition (growth, maintenance, and inflammatory response) of the shell. Furthermore, lesion severity depends on the extent to which cuticle degradation exceeds deposition. This model is consistent with natural observations of shell disease in American lobster.     

Treatment of ichthyophthiriasis in rainbow trout and common carp with common and alternative therapeutics

The goal of this laboratory study was to provide better knowledge about the treatment of ichthyophthiriasis (causative agent: Ichthyophthirius multifiliis, a ciliate bacteria) in rainbow trout Oncorhynchus mykiss and common carp Cyprinus carpio. The following questions were investigated: (1) the effectiveness of different chemicals (formalin, sodium chloride, hydrogen peroxide, Perotan, Virkon, Aquahumin, Baycox, and Ivomec) and at different concentrations and durations of application, (2) the number of treatments and the time intervals between treatments that were necessary to remove the parasite, and (3) how treatment effectiveness differed between the two species. The most effective treatment was a 37% stock solution of formalin at 110 microL/L of bath water for 1 h in rainbow trout and for 2 h in common carp. Aquahumin (150 microL/L for 2 h) was effective in slightly or moderately infected rainbow trout and at low water temperatures, but it was not effective for common carp. All other tested chemicals were ineffective. With formalin and Aquahumin, five treatments were necessary to remove I. multifiliis infestation. At 10 +/- 1 degrees C, the parasites were eradicated when the treatment was performed at 48-h intervals. At 18 +/- 1 degrees C the infestation was eliminated when treatment was performed at 24-h intervals but not at 48-h intervals. At 25 +/- 1 degrees C, treatment at 24-h intervals was ineffective; however, shorter intervals between treatments might improve treatment efficacy at this temperature. In contrast, the number of treatment repetitions played a minor role, and parasites were eliminated with five treatments in all experiments when the type of chemical and treatment interval were optimal.     

Treatment of Ichthyophthiriasis in Rainbow Trout and Common Carp with Common and Alternative Therapeutics

Abstract

The goal of this laboratory study was to provide better knowledge about the treatment of ichthyophthiriasis (causative agent: Ichthyophthirius multifiliis, a ciliate bacteria) in rainbow trout Oncorhynchus mykiss and common carp Cyprinus carpio. The following questions were investigated: (1) the effectiveness of different chemicals (formalin, sodium chloride, hydrogen peroxide, Perotan, Virkon, Aquahumin, Baycox, and Ivomec) and at different concentrations and durations of application, (2) the number of treatments and the time intervals between treatments that were necessary to remove the parasite, and (3) how treatment effectiveness differed between the two species. The most effective treatment was a 37% stock solution of formalin at 110 μL/L of bath water for 1 h in rainbow trout and for 2 h in common carp. Aquahumin (150 μL/L for 2 h) was effective in slightly or moderately infected rainbow trout and at low water temperatures, but it was not effective for common carp. All other tested chemicals were ineffective. With formalin and Aquahumin, five treatments were necessary to remove I. multifiliis infestation. At 10 ± 1°C, the parasites were eradicated when the treatment was performed at 48-h intervals. At 18 ± 1°C the infestation was eliminated when treatment was performed at 24-h intervals but not at 48-h intervals. At 25 ± 1°C, treatment at 24-h intervals was ineffective; however, shorter intervals between treatments might improve treatment efficacy at this temperature. In contrast, the number of treatment repetitions played a minor role, and parasites were eliminated with five treatments in all experiments when the type of chemical and treatment interval were optimal.     

Effects of pH, temperature, and salinity on persistence of avian influenza viruses in water

The combined effects of water temperature, salinity, and pH on persistence of avian influenza virus (AIV) were evaluated in a model distilled-water system using three isolates from ducks sampled in Cameron Parish, Louisiana. Variables were tested within the ranges normally associated with surface water. Differences were detected between temperature (17 C and 28 C), pH (6.2, 7.2, 8.2), and salinity (0 ppt and 20 ppt), with a strong interactive effect observed between pH and salinity. Estimated persistence of infectivity for 1 x 10(6) mean tissue-culture infective dose of A/mottled duck/LA/38M/87 (H6N2) was longest at 17 C/0 ppt/pH 8.2 (100 days) and shortest at 28 C/20 ppt/pH 8.2 (9 days). Differences in the response to these variables were apparent between viruses. The ability of AIV to persist in surface water was also evaluated using samples collected from varied waterfowl habitats in coastal Louisiana. Observations were consistent with the model system, with duration of infectivity decreasing with increased salinity and pH. This suggests that experimental results may have application to field conditions.     

National study of the gastrointestinal parasites of dogs and cats in Australia

The prevalence of gastrointestinal parasites in Australian pet dogs and cats was largely unknown prior to this study. Current recommendations for the prophylactic treatment of parasites in Australia are based on studies conducted 20-30 years ago. A total of 1400 canine and 1063 feline faecal samples were collected from veterinary clinics and refuges from across Australia. The overall prevalence of gastrointestinal parasites in dogs and cats was 23.9% (CI 21.7-26.1) and 18.4% (CI 16.1-20.7), respectively. Overall Giardia was the most prevalent parasite in dogs (9.3% CI 7.8-10.8) followed by hookworm (6.7% CI 5.4-8.0). Isospora felis was the most prevalent parasite in cats (5.6% CI 4.2-7.0), followed by Toxocara cati (3.2% CI 2.1-4.3). In conclusion the prevalence of intestinal helminths in Australian pet dogs and cats is low. Consequently, consideration should be given to the future use of anthelmintics and continued emphasis on pet owner education as means of preventing infection.     

Trials for the control of trichodinosis and gyrodactylosis in hatchery reared Oreochromis niloticus fries by using garlic

The present work was designed to study the prevalence of trichodinosis and gyrodactylosis in Oreochromis niloticus fries, and to test the therapeutic efficacy and preventive efficacy of garlic oil and crushed garlic cloves. Trichodinosis and gyrodactylosis are ectoparasitic diseases that affect most warm freshwater fish, especially fries and fingerlings. In a private O. niloticus fish hatchery, the prevalence of trichodinosis in 5-, 15- and 30-day-old-fries was 37%, 23% and 40.5%, respectively. The highest infection intensity was detected in 30-day-old-fries. The gyrodactylosis was reported only in combination with trichodinosis. In addition, we found that its prevalence in 5-, 15- and 30-day-old-fries was 17%, 19.5% and 29%, respectively. Mortality rate of fry in the first month of life was 53% as a result of injury to these two types of parasites. The garlic oil and crushed garlic cloves were tested in both in vitro and earthen ponds of the hatchery. Using 2-, 2.5- and 3-ppt (parts per thousand) garlic oil for 4h in vitro water bath treatment resulted in 100% recovery, while 1 and 1.5 ppt garlic oil, respectively, needed 24 and 16 h to treat the infected fries. The treatment by 3 ppt garlic oil as a water bath for 1h treated the two diseases in 55% in 7 days from application in the hatchery earthen pond. In the mean time, 300 mg L(-1) crushed garlic cloves as an indefinite bath in the hatchery earthen pond eliminated 68% of the diseases. The same protocol for preventing the two diseases resulted in obtaining 65% and 75% of parasite free fries, for garlic oil and crushed garlic cloves, respectively, compared to 53% of the control fries.     

In-vitro anthelminthic activity of crude aqueous extracts of Aloe ferox, Leonotis leonurus and Elephantorrhiza elephantina against Haemonchus contortus

Aloe ferox (Mill), Leonotis leonurus (L) R. BR; and Elephantorrhiza elephantina (Burch.) Skeels are plants frequently used by resource-limited farmers in the Eastern Cape Province to control gastrointestinal parasites in goats. A study was conducted to validate their anthelminthic activities in-vitro on the egg and larvae of the nematode parasite Haemonchus contortus. The crude aqueous extracts of leaves of A. ferox and L. leonurus; and roots of E. elephantina were used. Eggs and larvae of the parasite were incubated at 25°C in aqueous extracts at concentrations of 0.625–20 mg/ml for 48 h and 7 days for the egg hatch and larval development assays respectively. Albendazole and water were the positive and negative controls respectively. Inhibition of egg hatching and larval development increased significantly (P?<?0.05) with increasing concentrations of the extracts. E. elephantina and L. leonurus extracts had 100% egg hatch inhibition at concentration as low as 2.5 mg/ml and 1.25 mg/ml respectively, whereas A. ferox extracts had 100% inhibition at concentrations of 20 mg/ml. At the lowest concentration tested (0.625 mg/ml), E. elephantina inhibited egg hatching >96% and this was comparable to albendazole at the same concentration. E. elephantina and L. leonurus also totally inhibited larval development at concentrations of 1.25 mg/ml. The study provided evidence that A. ferox, E. elephantina and L. leonurus extracts possess anthelminthic activity, thus justifying their use in the treatment of GI helminthosis. There is however need to assess the safety of these plants in vivo and also to undertake in vivo efficacy studies.     

The anti-protozoal activity of bronopol on the key life-stages of Ichthyophthirius multifiliis Fouquet, 1876 (Ciliophora)

Pyceze? (Novartis Animal Vaccines Ltd.) is licensed as a veterinary medicine to treat fungal infections in salmon, trout and their eggs. The active ingredient is bronopol, which due to its broad-spectrum activity has the potential to be an effective treatment against other important aquatic pathogens. In this study the efficacy of bronopol against Ichthyophthirius multifiliis was tested both in vitro and in vivo. In vitro trials demonstrated a 30 min exposure to 100 mg L(-1) bronopol killed 51.7% of the infective theronts. In vitro exposure of the protomonts to bronopol (0, 20, 50 and 100 mg L(-1)) for 30 min was observed to kill 0%, 76.2%, 97.2% and 100% respectively. Protomonts surviving treatment, demonstrated delayed development with the time taken from protomont until the release of theronts ranging from 28.3h for 0 mg L(-1) exposure, to 70 h for parasites in 20 and 50 mg L(-1) exposure groups. These concentrations also caused asymmetric cell division of the encysted tomonts. Exposure of encysted tomonts (min. 8 cell stage) to 100 mg L(-1) bronopol for 30 min, killed 50% within this period, with the remainder dying within the subsequent 42 h post exposure. Lower doses of bronopol were less effective in killing encysted tomonts than the higher doses (3.3% of parasites were killed in 20 mg L(-1); 10% in 50 mg L(-1)), but they still delayed theront release significantly (25.7 h for 0 mg L(-1) to 46.2h for parasites exposed to 20-50 mg L(-1)). Long, low dose (1 mg L(-1)) exposure to bronopol was also efficacious against theronts. Survival after 12h was 29% (c.f. 100% in control parasites), and <1% after 24 h exposure (c.f. 74% in control parasites). Theronts surviving these exposures demonstrated reduced infection success compared to control theronts. The findings of this study demonstrate that bronopol (Pyceze?) affects the survival of all free-living stages of I. multifiliis (protomonts, tomont and theronts), thus suggesting that bronopol may serve a useful role in the control of I. multifiliis infections.     

Granulomatous nephritis in psittacines associated with parasitism by the trematode Paratanaisia spp

Trematodes belonging to the family Eucotylidae are parasites of the kidney and ureter, and affect several bird species. However, psittacines have not been identified as hosts of these parasites. Three birds, an adult female blue and gold macaw (Ara ararauna), an adult female blue-winged macaw (Propyrrhura maracana) and an adult male white-eared parakeet (Pyrrhura leucotis) were admitted at the Veterinary Hospital of the Funda??o Zoo-Botanica de Belo Horizonte, Brazil (FZB/BH). All three birds had severe dehydration and cachexia. The blue and gold macaw presented with dyspnea, apathy, and incoordination. Blood cell counts indicated discrete anemia and leucopenia. Blood biochemistry revealed significant increase in levels of uric acid (61 mg/dl) and blood urea nitrogen (22 mg/dl). The bird died within 24 h after admission. The other two birds were admitted with similar clinical signs, but died prior to a complete clinical examination. At the necropsy, in all the three birds, the kidneys were enlarged with brown-yellowish discoloration and irregular cortical surface. On the cut surface, there was a brown-yellowish material with few visible parasites flowing out of the parenchyma. When fragments of the kidneys were placed in 10% formalin, a large number of trematodes came out of the renal parenchyma. The parasites were identified as Paratanaisia robusta infecting all three birds, and P. bragai infecting the blue-winged macaw and the white-eared parakeet. Histologically, there was an interstitial, multifocal to coalescent, lymphoplasmacytic infiltrate with some epithelioid macrophages, and a few heterophils, characterizing a granulomatous nephritis. Adult worms and eggs were observed within dilated tubules and in the renal pelvis. In the blue and gold macaw, some parasite eggs were located interstitially associated with an intense adjacent granulomatous reaction.     

寄生虫蛋白酶体的研究进展

近年来,蛋白酶体的分子组成、亚基、生化机理、胞内功能等方面的研究受到广泛关注,发展迅速.蛋白酶体的主要生物学功能包括:降解细胞内蛋白质、调节细胞周期、促进细胞凋亡、调节转录因子、增加抗原提呈等.在寄生虫中,蛋白酶体不仅参与胞内寄生虫的生长发育调节,同时对宿主造成损伤,并可诱导宿主产生对其的免疫应答.对寄生虫蛋白酶体的研究有助于深入了解寄生虫的入侵机制,为寄生虫病的防治提供新思路.作者对蛋白酶体的结构、功能及寄生虫蛋白酶体的研究进展作一综述.     

LongRange™ (eprinomectin 5%) extended-release injection parasiticide and the utility of extended-activity antiparasitics in cattle

An extended-release injection, which is administered at a rate of 1 mg eprinomectin/kg body weight, has been developed to provide up to 150 days control of parasites of cattle. The product can facilitate the achievement of two of the fundamental aims of parasite control. The first is protection of the host against the negative impact of susceptible parasites in order to ensure control of disease and to enhance performance. The second is to reduce parasite transmission and hence the challenge to animals when grazing. In addition, farmers and veterinarians can benefit from high levels of convenience and hence compliance from a single administration, which also limits handling stress in the cattle. This introductory paper provides some perspective on the practical applications for this extended-release product under various husbandry systems and in different classes of cattle and discusses its role in sustainable parasite control.     

Effects of sevoflurane dose and mode of ventilation on cardiopulmonary function and blood biochemical variables in horses

OBJECTIVE: To quantitate effects of dose of sevoflurane and mode of ventilation on cardiovascular and respiratory function in horses and identify changes in serum biochemical values associated with sevoflurane anesthesia. ANIMALS: 6 healthy adult horses. PROCEDURE: Horses were anesthetized twice: first, to determine the minimum alveolar concentration (MAC) of sevoflurane and second, to characterize cardiopulmonary and serum biochemical responses of horses to 1.0, 1.5, and 1.75 MAC multiples of sevoflurane during controlled and spontaneous ventilation. Results-Mean (+/- SEM) MAC of sevoflurane was 2.84 +/- 0.16%. Cardiovascular performance during anesthesia decreased as sevoflurane increased; the magnitude of cardiovascular depression was more severe during mechanical ventilation, compared with spontaneous ventilation. Serum inorganic fluoride concentration increased to a peak of 50.8 +/- 7.1 micromol/L at the end of anesthesia. Serum creatinine concentration and sorbitol dehydrogenase activity reached their greatest values (2.0 +/- 0.8 mg/dL and 10.2 +/- 1.8 U/L, respectively) at 1 hour after anesthesia and then returned to baseline by 1 day after anesthesia. Serum creatine kinase, aspartate aminotransferase, and alkaline phosphatase activities reached peak values by the first (ie, creatine kinase) or second (ie, aspartate aminotransferase and alkaline phosphatase) day after anesthesia. CONCLUSIONS AND CLINICAL RELEVANCE: Sevoflurane causes dose-related cardiopulmonary depression, and mode of ventilation further impacts the magnitude of this depression. Except for serum inorganic fluoride concentration, quantitative alterations in serum biochemical indices of liver- and muscle-cell disruption and kidney function were considered clinically unremarkable and similar to results from comparable studies of other inhalation anesthetics.     

Polystoma umthakathi (Monogenea): establishment,mortality and reproduction of neotenic parasites in experimentally infected Natalobatrachus bonebergi tadpoles

The development of Polystoma umthakathi oncomiracidia were studied in experimentally infected Natalobatrachus bonebergi tadpoles to establish a normal reference of parasite performance in the natural host. The anteroventral body wall is transparent in these tadpoles and it was possible to follow the destiny of each parasite throughout its life span of neotenic development. Success of establishment was 27,9% and mean parasite intensity 2,1 at 48 h. After parasite larvae initially attached to the gills on the left side, they gradually migrated to the right side and mature parasites only occurred inside the right branchial chamber. Parasite mortality was high, prevalence had declined to 72,4% after 12 days and 48,3% after 20 days while mean parasite intensity had declined to 1,8 and 1,6 during the same period. Egg production was around 13 to 15 eggs/parasite/day for parasites in burdens of one and two but significantly lower (5,24) in the case of three-parasite burdens. Tadpoles harbouring two or more parasites became anaemic but recovered when most or all parasites were lost.     

Influence of capture method, habitat quality and individual traits on blood parameters of free-ranging lace monitors (Varanus varius)

OBJECTIVE The aims of this study were to determine baseline reference intervals for haematological and serum biochemical parameters in lace monitors, and to examine whether such values were influenced by capture method, expected differences in habitat food resource availability and a lizard's body size and body condition. METHODS Thirty-three wild Victorian lace monitors (Varanus varius) of unknown age and sex were captured by noose pole or aluminium box trap from Cape Conran in East Gippsland, Victoria, Australia. RESULTS No statistical differences between the two capture methods were noted for haematology. There was a significant difference in the serum glucose concentrations between the two methods of capture (higher concentration in box-trapped animals) because of a physiological response to capture stress. Habitat food quality did not appear to influence haematology or serum biochemistry. The packed cell volume (PCV) for the lace monitors was 0.29-0.43 L/L. Lymphocytes were identified as the most common leucocyte. The haemoprotozoan parasite, Haemogregarina varanicola, was found in all 33 blood samples. No correlation could be made between parasite burden and PCV, serum globulins or serum proteins, but animals in poor body condition were more likely to harbour large numbers of parasites. CONCLUSION The results of this study may be used as a basis for evaluating health in lace monitors.     

Species spectrum, diversity profile and infection indices of helminth parasite fauna of Chirruh snowtrout, Schizothorax esocinus (Heckel) in lake ecosystems of Kashmir Himalayas-Do similarity and host-parasite associations arise?

In order to assess the species richness and diversity profile of helminth parasite fauna in an endemic fish, an investigation was carried out in two urban and two rural lakes of Kashmir. Overall nine species of helminth parasites were observed in four lakes. Of these three were autogenic and six were allogenic. Heteroxenous parasite species were more in number than monoxenous species. Results showed significant differences in heteroxenous / monoxenous ratio between different lakes. Core species (Prevalence?>?20) were only found in hypertrophic lake (Anchar Lake). Overall, majority of helminth species were either secondary or satellite species. Prevalence of some helminth parasites showed significant differences in different lakes. In addition mean intensity showed significant differences between autogenic and allogenic parasites (P?<?0.05). Principle Component Analysis based on prevalence showed that Anchar Lake was strongly associated with most of helminth parasites. Diversity indices showed significant variation between different lakes. Maximum helminth species per host was in Anchar Lake. Finally we concluded that helminth parasite fauna showed significant differences in species richness and infection indices between different lakes. Diversity profile was higher in Anchar Lake in comparison to other three lakes. The results clearly show that environmental features of lake ecosystems have got an impact on distribution pattern of helminth parasites in S. esocinus. We suggest comparative parasitological study should be taken between different species of fish in order to have a clear picture regarding the species composition of helminth species in this region. Also we need to characterize the species spectrum of parasitic worms in fish of freshwater bodies of this region as well as other similar type of climatic zones because parasite fauna is an integral part of the inventory of biodiversity and as possible regulators of host populations in aquatic ecosystems.     

Longitudinal analysis of cytokine gene expression and parasite load in PBMC in Leishmania infantum experimentally infected dogs

Canine visceral leishmaniasis (CVL) is caused by Leishmania infantum, an intracellular protozoan parasite that causes a severe infectious disease. To evaluate the gene expression profile associated to CVL in vivo, we have measured monthly by real-time PCR over one year the IL-4, IL-10, IL-12, IL-13, IFN-gamma, TGF-beta and TNF-alpha mRNA levels in peripheral blood mononuclear cells in 6 experimentally infected dogs that exhibited different progressions of the illness. While in two dogs no parasite, or a very low number of parasites, was detected and the two dogs did not show any clinico-pathological abnormalities at the end of the study (L dogs), for the remaining dogs high parasite loads were detected and they developed clinical leishmaniasis (H dogs). The L dogs have null expression of both IL-4 and IL-13 for the first 4 months after the infection, whereas an early IL-4 and IL-13 expression occurs in this period of infection in most of the dogs that developed clinical leishmaniasis (H dogs). Furthermore, a higher IFN-gamma expression was associated with the increase of parasite load and clinical status in these dogs. Moreover, the high variability of expression at the pre-infection stage causes us to reject the possibility that the basal levels of these cytokines indicate the prognosis of the subsequent response against infection.     

In vitro growth requirements for the fish pathogen Philasterides dicentrarchi (Ciliophora,Scuticociliatida)

Philasterides dicentrarchi is a scuticociliate causing fatal disease in farmed turbot and sea bass. In view of its high virulence and endoparasitic location, this parasite cannot be effectively controlled by formalin baths, and no systemic chemotherapeutic treatments have yet proved effective; immunoprophylaxis may thus be an attractive alternative approach. Since vaccine development is greatly facilitated by axenic culture of the pathogen, we have developed a simple axenic culture system based on commercially available Leibovitz L-15 medium, supplemented with fetal bovine serum, lipids (lecithin and Tween 80), nucleosides and glucose. After 1 week's culture under optimal conditions (salinity 10 per thousand, pH 7.2, temperature between 18 and 23 degrees C), yields of 1-2 x 10(5)cells/ml were obtained. Even cultures with seeding densities as low as 20 cells/ml were found to produce a good yield of ciliates (about 6 x 10(4)cells/ml) after 11 days of incubation. The ciliates thus obtained were free of contamination by other microorganisms, enabling preparation of pure P. dicentrarchi antigens for vaccine development studies.