Effects of long duration, low dose bronopol exposure on the control of Ichthyophthirius multifiliis (Ciliophora), parasitising rainbow trout (Oncorhynchus mykiss Walbaum)

Ichthyophthirius multifiliis Fouquet, 1876 infections on intensively reared fish stocks can increase rapidly, which if left unmanaged, can result in the heavy loss of stock. The present study explores the efficacy of long duration, low dose (1, 2 and 5 mg L(-1)) treatments of bronopol (marketed as Pyceze?, Novartis Ltd.) in reducing the number of trophonts establishing on juvenile Oncorhynchus mykiss held under small scale culture conditions. The effect of bronopol on the colonisation success of infective theronts was also investigated by adding 2 mg L(-1) bronopol to the water prior and during the infection process. The number of parasites surviving on fish treated this way was compared to groups of fish that only received treatment after infection had occurred. The effect of bronopol on exiting trophonts throughout their external development to the point of theront release was also assessed through the delivery of 1 mg L(-1), 2 mg L(-1) and 5 mg L(-1) bronopol for up to 27 days consecutively (days 9-36 post-infection). The trial showed that a nominal dose of 2 mg L(-1) bronopol administered prior to infection significantly reduced the number of theronts surviving in the water column at the time of the initial challenge by 35-40% (P<0.05). Similarly, doses of 2 and 5 mg L(-1) bronopol administered as the first wave of mature I. multifiliis trophonts exited fish (i.e. day 11 onwards) to develop externally, reduced the number of trophonts establishing on fish as the second cycle of infection by 52-83%. Continuous application of 2 and 5 mg L(-1) bronopol throughout the second and third cycles of I. multifiliis infection gave further reductions of between 90 and 98%. The number of trophonts on the fish in the control tanks and those treated with 1 mg L(-1) and the 2 mg L(-1) dose at the time of initial infection, by comparison, were observed to increase with successive cycles of infection. From these small scale tank trials, this study demonstrates that the strategic, long duration, low dose delivery of drugs like bronopol can significantly reduce the number of trophonts establishing on fish suggesting the potential of this drug at managing I. multifiliis infections.     

Enhanced susceptibility of channel catfish to the bacterium Edwardsiella ictaluri after parasitism by Ichthyophthirius multifiliis

Bacterium Edwardsiella ictaluri and parasite Ichthyophthirius multifiliis (Ich) are two common pathogens of cultured fish. The objective of this study was to evaluate the susceptibility of channel catfish Ictalurus punctatus to E. ictaluri and determine bacterial loads in different fish organs after parasitism by Ich. Fish received the following treatments: (1) infected by I. multifiliis at 5000 theronts/fish and exposed to E. ictaluri; (2) infected by I. multifiliis alone; (3) exposed to E. ictaluri alone; and (4) non-infected control. E. ictaluri in fish organs were quantified by quantitative real-time polymerase chain reaction and reported as genome equivalents per mg of tissue (GEs/mg). The results demonstrated that the Ich-parasitized catfish showed significantly (P<0.05) higher mortality (91.7%) when exposed to E. ictaluri than non-parasitized fish (10%). The bacterial loads in fish infected by 5000 theronts/fish ranged from 6497 to 163,898 GEs/mg which was between 40 and 2000 fold higher than non-parasitized fish (49-141 GEs/mg). Ich infection enhanced the susceptibility of channel catfish to bacterial invasion and increased fish mortality.     

Immunosuppression of carp (Cyprinus carpio L.) to ichthyophthiriasis using the corticosteroid triamcinolone acetonide

The immune response of juvenile mirror carp (Cyprinus carpio L.) has been investigated in relation to protective immunity and immunosuppression to the disease ichthyophthiriasis. Protective immunity was induced by exposing juvenile carp to approximately 2,000 theronts per fish for 3 hours at a concentration of approximately 80 theronts cm-3 in dechlorinated water pH 7.0-7.2, 20 +/- 2 degrees C in the dark, on three separate occasions of 14 day intervals. Following each exposure, re-infection was prevented by transferring fish to clean aquaria twice daily from day 5-10. Fish were challenged 4 weeks following exposure to the third immunising infection with a potentially lethal dose of approximately 8,000 theronts per fish for 3 hours at a concentration of approximately 320 theronts cm-3. All immunised fish survived although 19% showed initial signs of invasion, the parasites in these instances being confined to periphery of fins. Mortalities of 100% were recorded in non-immunised controls, first deaths occurring 5 days after challenge. Fourteen days following challenge, immune fish received one of the following treatments; intraperitoneal injection of the corticosteroid triamcinolone acetonide at a dose of 200 micrograms g-1 body weight, intraperitoneal injection of 0.85% saline or left untreated; non-immunised fish were subjected to similar procedures. On challenge 6 days later, all fish developed heavy infection with up to 100% mortalities with the exception of immunised fish administered saline or left untreated. Repeat experiments gave comparable results. The results indicate that immunosuppression can be induced by administration of high levels of synthetic corticosteroid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antiparasitic effects of peracetic acid (PAA) against infective stages (theronts) of white spot disease, Ichthyophthirius multifiliis in vitro

White spot disease, caused by the protozoan parasite Ichthyophthirius multifiliis (I. multifiliis), invades nearly all fresh water fish species and causes huge economic losses. In Germany no protocide substance is legal for the treatment of I. multifilis. As an alternative substance the peracetic acid (PAA) was tested to treat the free invasive stage (theront) of the parasite. PAA concentrations of 0.3 ppm were able to kill all theronts in 120 min in our investigations. As a result of these investigations we recommend an interval-application of 0.3 to 0.5 ppm PAA for 30 to 150 min. This application should be prolonged for two life cycles of the parasite. Biotic parameters as e. g. fish species, and age as well as abiotic parameters as e. g. temperature, pH and organic load of the water could possibly influence the efficiency of the PAA application and should therefore be taken into account while picking the dosage and length of the PAA exposure.     

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.     

Pharmacokinetics and bioavailability of spectinomycin after i.v., i.m., s.c. and oral administration in broiler chickens

A pharmacokinetic and bioavailability study of spectinomycin was conducted in healthy broiler chickens following administration of a single (50 mg/kg bw) intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) dose and oral doses of 50 and 100 mg/kg bw. Following i.v. administration, the elimination half-life (t1/2beta), mean residence time (MRT), volume of distribution at steady-state (Vd(ss)), volume of distribution based on the terminal phase (Vd(z)) and total body clearance (ClB) were 1.46+/-1.10 h, 1.61+/-1.05 h, 0.26+/-0.009 L/kg, 0.34 (0.30-0.38) L/kg and 2.68+/-0.017 mL/min/kg respectively. After i.m. and s.c. dosing, the Cmax was 152.76+/-1.08 and 99.77+/-1.04 microg/mL, achieved at 0.25 (0.25-0.50) and 0.25 (0.25-1.00) h, the t1/2beta was 1.65+/-1.07 and 2.03+/-1.06 h and the absolute bioavailability (F) was 136.1% and 128.8% respectively. A significant difference in Cmax (5.13+/-0.10, 14.26+/-1.12 microg/mL), t1/2beta (3.74+/-1.07, 8.93+/-1.13 h) and ClB/F (22.69+/-0.018, 10.14+/-0.018 mL/min/kg) were found between the two oral doses (50 and 100 mg/kg bw respectively), but there were no differences in the tmax [2.00 (2.00-4.00), 2.00 (2.00-2.00) h] and Vd(z)/F [6.95 (6.34-9.06), 7.98 (4.75-10.62) L/kg). The absolute bioavailability (F) of spectinomycin was 11.8% and 26.4% after oral administration of 50 and 100 mg/kg bw respectively.     

Application of peracetic acid for the treatment of juvenile sander (Sander lucioperca) during Ichthyophthirius multifiliis infestation

White spot disease caused by the ciliate protozoan parasite Ichthyophthirius multifiliis (I. m.), is one of the most dangerous diseases in aquaculture and ornamental fish breeding worldwide. The parasite is characterized by three developmental stages: a reproductive tomont, an infective theront and a parasitic trophont. In sander (Sander lucioperca) breeding I. m. causes serious economic losses. After banning of the traditional therapeutic agent malachite green we have to face a state of emergency for the treatment of the ichthyophthiriasis in Germany. The peracetic acid (PAA), characterized by positive therapeutical properties, might close this gap. The purpose of our investigations was the determination of the toxicity of PES to juvenile sander as well as the evaluation of the therapeutic effectiveness of the substance to combat I. m. For juvenile sander (length 3 cm) we determined a 24-h-LC50 of 1.14 (0.97; 1.3) ppm PES. In two investigations PAA was applied in daily intervals of 0.5; 1, 3, 5 and 24 h and concentrations of 0.5; 1; 1.5 and 2 ppm to treat I.-m.-infection in sander. In test I all sander (length 9 cm) died as a result of the I.-m.-infection. However, the PAA exposed fish survived longer than the PES-free controls! This might be due to a disinfection of other pathogens by PAA. In test II, the fish (length 12 cm) were less infected than fish in test I. Four of six fish died in the group exposed with 2 ppm PAA for 24 hours. The abundance of I.-m.-trophonts was determined in mucus, fin and gill tissues of all fish. Significant differences could not be observed between test I and test II because of dissimilar: 1. exposure in time and concentration, 2. age and condition of the fish and 3. homogenity of the variances. Therefore, no therapy strategy was successful while fighting the parasitic trophonts protected by the overlaying fish tissues. We speculate that a successful therapy of I. m. with PAA is, as known e.g. for malachite green, only possible while fighting the free living stages theronts and tomonts. This will be part of our subsequent investigations.     

Importance of Treatment Duration for Praziquantel Used against Larval Digenetic Trematodes in Sunshine Bass

Abstract

The effectiveness of praziquantel (Droncit) against yellow grubs Clinostomum complanatum and unidentified, encysted, larval trematodes was tested in infected sunshine bass Morone chrysops female × M. saxatilis male. Praziquantel treatments significantly reduced the total number of live grubs in the fish in most treatment regimes tested. Treatment at 0.25 mg/L for 24 h was as effective as one at 8 mg/L for 8 h. Mature dead and dying metacercaria may have released toxins that killed host fish in some treatments.     

Efficacy of Copper Sulfate for the Treatment of Ichthyophthiriasis in Channel Catfish

Abstract

Ichthyophthirius multifiliis is a protozoan that may infest and significantly damage cultured fish species. The purpose of this study was to measure the efficacy of copper sulfate in treating ichthyophthiriasis. Fingerling channel catfish Ictalurus punctatus exposed to at least 2,000 theronts of I. multifiliis per liter of water developed consistent infestations of I. multifiliis (20 or more trophonts on the dorsal surface of the head of the fish). Infestation was observed in untreated controls at day 5 after exposure and mortality occurred after day 10. Coexposure studies with theronts and different concentrations of copper sulfate revealed that all theronts were killed at concentrations greater than 0.05 mg/L. To determine the effect of copper sulfate in the treatment of ichthyophthiriasis, fish were exposed to the parasite until trophonts were observed (day 5), and they were subsequently treated with copper sulfate. The lowest effective concentration of copper sulfate for treatment of ichthyophthiriasis (i.e., after infestation was observed in the fish) was 0.4 mg/L. To assess the effects of various water quality conditions on copper treatment, total suspended solids (TSS) and pH were varied during treatment of ichthyophthiriasis. Concentration of TSS was inversely correlated to the efficacy of copper sulfate for I. multifiliis infestations, whereas no relationship was observed between pH and efficacy of a single copper sulfate dose. The results indicated that copper sulfate can be used to treat ichthyophthiriasis at concentrations of 0.4 mg/L for at least 5 d under the specific water conditions used in this study (pH, 7.45 ± 0.27; temperature, 20.5 ± 0.7°C; alkalinity, 176.6 ± 28.1 mg/L as CaCO₃) and that efficacy of copper sulfate was affected more by TSS concentration than by pH.     

Effects of formalin, chloramine-T, and low salinity dip on the behavior and hemolymph biochemistry of the American lobster.

The purpose of this research was to investigate the salinity and formalin sensitivity of a ciliate parasite (Anophryoides haemophila) of the American lobster (Homarus americanus), and to examine the target-animal (lobster) safety of chemical-bath treatments involving low salinity, formalin, or chloramine-T that could be used to control this parasite in lobster pounds. "Bumper car" disease, caused by An. haemophila, is an important concern to lobster pound operators in eastern North America, because of the implicated lobster mortality rate and the general lack of preventive and therapeutic intervention regimes. We determined, using an in vitro method, that formalin at 50 mg/L, or low salinity at 8.0 parts per thousand (ppt) for 1 hour killed 100% of the parasites. When healthy lobsters were exposed to formalin at 200 mg/L, there were no negative behavioral responses and no significant differences in a panel of hemolymph biochemical indices. Similar results occurred when lobsters were exposed to chloramine-T, a common finfish therapeutic agent for topical bacteria and protozoa, at 10 mg/L for 1 hour. The low salinity treatment (8.0 ppt) resulted in significant adverse changes in lobster behavior and biochemical indices; however, these changes did not persist for more than 1 week after treatment ended. Although these treatments are unlikely to kill parasites that have already invaded the lobster carapace, they should be effective in reducing parasite loads on the gill and carapace surface of the lobster and in the environment of the impoundment housing.     

Efficacy of a substituted methyl benzimidazole carbamate against developing and adult helminth parasites

The efficacy of a substituted methyl benzimidazole carbamate, methyl 5(6)-[4-N-(2-pyridyl)] piperazino carbamoyl benzimidazole-2-carbamate, was assessed against larval and adult forms of Ancylostoma ceylanicum (hookworm), Nippostrongylus brasiliensis (trichostrongylid), Hymenolepis nana (tapeworm) and Brugia malayi (filariid) in experimentally-infected animals. The compound was found to have high efficacy against the developing stages (L3, L4, L5) of A. ceylanicum in hamsters at a single dose of 12.5 mg kg-1, against larvae of N. brasiliensis at 17.5 mg kg-1 and against cysticercoids of Hymenolepis nana at 100 mg kg-1 daily for 3 days given per os (p.o.) or intraperitoneally (i.p.). All the stages of B. malayi in Mastomys were killed when the compound was given i.p. at a dose of 6.25 mg kg-1 for 5 consecutive days. A dose of 6.25 mg kg-1 eliminated all adult A. ceylanicum from infected hamsters, 100 mg kg-1 resulted in complete removal of Syphacia obvelata adults from 63.6% of infected mice, 25 mg kg-1 X 5 dose eliminated 100% of adult B. malayi from infected Mastomys and a single 50 mg kg-1 dose expelled all H. nana adults from infected rats.     

Larvicidal activity of two Algerian Verbenaceae essential oils against Culex pipiens

The purpose of this study was to evaluate the bioactivity of essential oils extracted from the leaves of Verbena officinalis and Lantana camara L. for the control of Culex pipiens. Triplicate bioassays were performed with fourth larval instars of C. pipiens (n=25 per replicate) with solutions at 1, 5, 10, 50, 100 and 500 μL/L of V. officinalis and L. camara L. extracts. Cumulative mortalities were determined 3, 6, 12 and 24h after treatment. Results showed cumulative mortalities, at three (3) hours to be 30.0 ± 2.9% and 14.8 ± 1.5% and achieve 43.3 ± 1.9% and 44.4 ± 3.1% after 24h exposure time, at 100mg/L of essential oil from L. camara and V. officinalis, respectively.     

Effect of Common Aquaculture Chemicals against Edwardsiella ictaluri and E. tarda

Abstract

Edwardsiellosis is an important bacterial infection of freshwater and marine fishes. Edwardsiella ictaluri causes enteric septicemia of catfish, and E. tarda causes emphysematous putrefactive disease of catfish and fish gangrene in various species; these diseases have considerable economic effects on the aquaculture industry. In addition, E. tarda is an important zoonotic pathogen. Thus, the reduction or elimination of these pathogens from an aquarium or aquaculture facility is imperative. This study examined a variety of commercially available chemicals for their ability to reduce or eliminate E. ictaluri and E. tarda from the aquatic environment. The various concentrations of chemicals were tested in vitro in microcentrifuge tubes with a known concentration of bacteria at room temperature. In this study, ethyl alcohol (30, 50, or 70%), benzyl-4-chlorophenol/phenylphenol (1%), sodium hypochlorite (50, 100, 200, or 50,000 mg/L), n-alkyl dimethyl benzyl ammonium chloride (1:256), povidone iodine (50 or 100 mg/L), glutaraldehyde (2%), and potassium peroxymonosulfate/sodium chloride (1%) were effective disinfectants, as each reduced or eliminated the number of detectable organisms within 1 min of contact time. However, neither Chloramine-T (15 mg/L) nor formalin (250 mg/L) substantially reduced bacterial counts even after 60 min of contact time.     

Pharmacokinetic and pharmacodynamic properties of metomidate in turbot (Scophthalmus maximus) and halibut (Hippoglossus hippoglossus)

Metomidate was administered to halibut (Hippoglossus hippoglossus) and turbot (Scophthalmus maximus) intravenously at a dose of 3 mg/kg bodyweight, as a bath treatment at a dose of 9 mg/L water for 5 min to study the disposition of metomidate, and as bath treatment (9 mg/L) for 10 min to study the absorption and effect of metomidate on respiration and balance/motor control. Additionally, turbot were given metomidate orally at a dose of 7 mg/kg. The studies were performed in seawater at a temperature of 10.3 +/- 0.4 degrees C (halibut) and 18.0 +/- 0.3 degrees C (turbot). Pharmacokinetic modeling of the data showed that metomidate had shorter elimination half-life and higher plasma concentrations in turbot compared with halibut, both species displaying a rapid uptake, distribution and excretion. Following intravenous administration, the volumes of distribution at steady state (Vd(ss)) were 0.21 L/kg (halibut) and 0.44 L/kg (turbot). Plasma clearances (Cl) were 0.099 L/h.kg in halibut and 0.26 L/h.kg in turbot and the elimination half-lives (t(1/2)lambdaz) were calculated to be 5.8 h and 2.2 h in halibut and turbot, respectively. Mean residence times (MRT) were 2.2 h in halibut and 1.7 h in turbot. Following oral administration, the t(1/2)lambdaz was 3.5 h in turbot. The maximum plasma concentration (Cmax) was 7.8 mg/L in turbot 1 h after administration. The oral bioavailability (F) was calculated to 100% in turbot. Following 5 min bath the maximum plasma concentrations (Cmax), which were observed immediately after end of the bath, were 9.5 mg/L and 13.3 mg/L in halibut and turbot, respectively. Metomidate rapidly immobilized the fish, with respiratory depression, reduced heart rate, and loss of balance/motor control within 1 min (mean). Recovery was slow, with resumed balance/motor control after 26.4 min. Opercular respiration movements were resumed more rapidly with a recorded mean of 1.7 min. Oral administration was demonstrated to be a way of immobilizing fish, for example in large aquariums, without exposing them to unwanted stress.     

毒死蜱对家蚕的急性毒性研究

在室内不同条件下进行了桑园杀虫剂毒死蜱对家蚕的急性毒性试验,结果表明:毒死蜱对2~5龄家蚕幼虫的摄入LC50值(48 h,25℃)分别为1.11、1.73、3.48与4.12 mg/L;在20、25、30、35℃下,毒死蜱对3龄家蚕的LC50值(48 h)分别为1.70、1.80、0.49与0.40 mg/L;桑叶浸药时间为1 s、10 s、1 m in、10 m in与1 h时,毒死蜱对4龄家蚕幼虫的LC50值(48 h,25℃)分别为5.55、3.64、3.15、2.12与1.54 mg/L;家蚕幼虫在毒死蜱药膜上爬行1、10、30与60 m in后,毒死蜱对3龄家蚕的接触LD50值(48 h,25℃)分别为3.59、0.28、0.20、0.12μg/cm2。     

Osthol and isopimpinellin from Fructus cnidii for the control of Dactylogyrus intermedius in Carassius auratus

The efficacy of two active compounds, isolated from the fruit of Fructus cnidii, was determined against Dactylogyrus intermedius in goldfish (Carassius auratus). The chemical structure of the two compounds was identified by spectral analysis. Designated Compounds I and II, they were isolated by successive silica gel column chromatography and used, in combination, in an in vivo anthelmintic efficacy assay. At dose rates of 1.6 and 9.5 mg l(-1), respectively, the two compounds were 100% effective against D. intermedius compared to mebendazole (positive control), used at a concentration of 1.5 mg l(-1), which is 100% efficacious. Compounds I and II were shown to be safe for goldfish at dose rates of up to 6.4 and 12.5 mg l(-1), respectively. The median effective dose (ED(50)) of Compounds I and II for D. intermedius-infested goldfish after 48 h exposure was 0.807 and 8.050 mg l(-1), respectively. If the median lethal dose (LD(50)) values for goldfish of the two compounds are 6.749 and 12.759 mg l(-1), respectively, the ED(50) values for D. intermedius yielded a therapeutic index of 8.14 and 1.52 for Compounds I and II, respectively, at 48 h. Compounds I and II were identified as osthol and isopimpinellin by physico-chemical detection.     

Persistent efficacy of a long acting injectable formulation of moxidectin against natural infestations of the sheep nasal bot (Oestrus ovis) in Spain

Cydectin(?) 2% LA Solution for Injection for Sheep (Pfizer Animal Health) is a long-acting (LA) formulation of moxidectin for the treatment and prevention of mixed infections of gastro-intestinal nematodes, respiratory nematodes and certain arthropod parasites in sheep. To evaluate the duration of persistent efficacy against nasal bots (Oestrus ovis), a natural exposure study was conducted in Spain during the summer of 2011. One hundred and twenty nasal bot-free, Rasa Aragonesa sheep were randomly allocated to eight groups of 15 animals each. On Day 0, four groups were treated at the recommended dose rate of 1 mg moxidectin/kg bodyweight. Four groups remained untreated as negative controls. All animals were held in nasal bot-proof housing except for exposure to natural challenge when one group of treated sheep and one of group of control animals were transferred to a local pasture at either 0-20, 20-40, 40-60, or 60-80 days after treatment. Following challenge, sheep were scored for clinical signs of bot infestation, necropsied and the heads sectioned for larval recovery. Nasal bot larvae were retrieved from 7 to 11 control sheep following each exposure period indicating that adult bots were active throughout the study. In the first challenge up to 20 days after treatment, when sheep were slaughtered immediately after exposure, the majority of larvae were first instar (L1) and only 3 of the 15 control sheep were infested with second instars (L2). There was 100% efficacy against L2 and 38.1% reduction in the number of live L1 in the treated sheep but mean counts were not significantly different between treatment and control groups (P ≥ 0.05). For the subsequent exposure periods 20-80 days after treatment (necropsies 7-9 days after challenge), 6-10 sheep were infested with L1 and 9-11 control sheep were infested with L2 and third instars (L3). There was negligible efficacy against L1, but treatment with moxidectin resulted in 100% control of L2 and L3. These results are consistent with the biology of nasal bots and control with a systemic agent, as the slower growing L1 have limited feeding and are therefore less susceptible to systemic parasiticides. The study demonstrated that the persistent efficacy of this long-acting injectable formulation of moxidectin protects against the development of active O. ovis infestations for at least 80 days after treatment.     

Efficacy of thiophanate and albendazole against natural infections of Dicrocoelium dentriticum, Fasciola hepatica, and gastrointestinal nematodes and cestodes in sheep

The anthelmintic efficacy of thiophanate and albendazole was compared in sheep with heavy infestations of Dicrocoelium dentriticum. The effectiveness of each drug was determined by counting the numbers of D. dentriticum in animals killed 21 days after treatment. In one group, the dose of thiophanate recommended for use against gastrointestinal (GI) nematodes (50 mg kg-1 live weight) was found to be 74.4% effective against D. dentriticum. Two tablets (each containing 76 mg of active ingredient) of albendazole per 30 kg live weight were given to a second group and the dose repeated after 1 week. Under this regime, albendazole was found to be 12.7% effective against D. dentriticum. The effect of each drug on other parasites was as follows; thiophanate had no effect against Fasciola hepatica or cestodes, while albendazole was 71.5% effective against F. hepatica and 100% effective against cestodes. Both drugs were highly effective against GI nematodes.     

Effect of common aquaculture chemicals against Edwardsiella ictaluri and E. tarda

Edwardsiellosis is an important bacterial infection of freshwater and marine fishes. Edwardsiella ictaluri causes enteric septicemia of catfish, and E. tarda causes emphysematous putrefactive disease of catfish and fish gangrene in various species; these diseases have considerable economic effects on the aquaculture industry. In addition, E. tarda is an important zoonotic pathogen. Thus, the reduction or elimination of these pathogens from an aquarium or aquaculture facility is imperative. This study examined a variety of commercially available chemicals for their ability to reduce or eliminate E. ictaluri and E. tarda from the aquatic environment. The various concentrations of chemicals were tested in vitro in microcentrifuge tubes with a known concentration of bacteria at room temperature. In this study, ethyl alcohol (30, 50, or 70%), benzyl-4-chlorophenol/phenylphenol (1%), sodium hypochlorite (50, 100, 200, or 50,000 mg/L), n-alkyl dimethyl benzyl ammonium chloride (1:256), povidone iodine (50 or 100 mg/L), glutaraldehyde (2%), and potassium peroxymonosulfate/sodium chloride (1%) were effective disinfectants, as each reduced or eliminated the number of detectable organisms within 1 min of contact time. However, neither Chloramine-T (15 mg/L) nor formalin (250 mg/L) substantially reduced bacterial counts even after 60 min of contact time.     

Quantitative analysis of the effect of probenecid on pharmacokinetics of 99mTc-mercaptoacetyltriglycine in dogs

Effect of probenecid on pharmacokinetics of 99mTc-mercaptoacetylytriglycine (99mTc-MAG3) in dogs was investigated before (control), and after 15 min and 24 h of i.v. injection of probenecid (20 mg/kg). Plasma concentration-time profiles of 99mTc-MAG3 were described with a two-compartment open model. Plasma 99mTc-MAG3 clearances (Clp, ml/min/kg) were 7.9 +/- 0.5, 3.3 +/- 0.5 and 4.8 +/- 1.3 in control, 15 min and 24 h after probenecid administration respectively. Similarly, the biological half-lives at elimination phase (t(1/2), h) were 0.61 +/- 0.09, 0.79 +/- 0.11 and 0.74 +/- 0.12, and volumes of distribution at steady state (Vdss, L/kg) were 0.29 +/- 0.04, 0.20 +/- 0.05 and 0.25 +/- 0.06 respectively. The prolonged biological half-life and decreased Vdss decreased Clp significantly. Clp was a function of plasma probenecid concentration based on Michaelis-Menten kinetics. The maximum Clp inhibition (Imax) by probenecid and the plasma probenecid concentration that induced 50% of Imax (I50) were estimated to be 72 +/- 12% and 13 +/- 8 microg/ml respectively. This means that the rest (about 28%) of the Clp is not blocked by probenecid alone, suggesting the possibility of another route(s) of elimination or renal transporters which are independent from probenecid. Moreover, inter-species correlation between Clp of 99mTc-MAG3 and body weight are discussed.