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PubMed2006

Anthelmintic action of eprinomectin in lactating Anglo-Nubian goats in Brazil.

Eprinomectin is the only avermectin approved for use to control gastrointestinal nematodes in lactating cows. Some studies in the USA and Europe have also demonstrated that this drug is highly effective in small ruminants. The aim of the present work was to evaluate the anthelmintic efficacy of pour-on eprinomectin in Anglo-Nubian goats at the end of lactation. Twenty-four goats were used, naturally infected with gastrointestinal nematodes, and divided into two groups: control and treated with eprinomectin (Eprinex, Merial, pour-on 0.5%) at a dose of 850 microg/kg. Counts were made of the eggs per gram (EPG) of feces, along with coprocultures, on days -7, 0, 4, 8, 11, 15, 18, 22, 25 and 29. The milk production of each group was recorded throughout the experiment. The coprocultures detected 98% Haemonchus contortus and 2% Oesophagostomum. There was no statistically significant difference (P > 0.05) in daily milk output between the two groups. Eprinomectin at the tested dosage was not effective (P > 0.05) in reducing the EPG. Positive results would serve as basis for use of an avermectin without residues in dairy goats, providing a scientific basis for greater food safety.

Animals↗
PubMed2000

In vivo activities of the new anthelmintic depsipeptide PF 1022A.

PF 1022A is a member of a new class of cyclic depsipeptides with antiparasitic activity. Following in vitro and laboratory animal studies it was tested for its anthelmintic efficacy in companion and livestock animals against a wide spectrum of intestinal nematodes and lungworms. Studies were carried out in rats, dogs, horses, sheep, and cattle. Animals were either naturally or experimentally infested. The efficacy of PF 1022A was investigated against the following parasite species: Strongyloides ratti and Nippostrongylus brasiliensis in rats, Ancylostoma caninum in dogs, small strongyles (cyathostomes) in horses, Trichostrongylus colubriformis and Haemonchus contortus in sheep, and Dictyocaulus viviparus in cattle. Doses varied from 1 to 10 mg/kg body weight for oral, subcutaneous or intravenous application in companion and livestock animals. High degrees of efficacy were found in all the above-cited examinations, and no clinical signs of intolerability were observed.

Animals↗
PubMed1996

Characterization of subtypes of gamma-aminobutyric acid receptors in an Ascaris muscle preparation by binding assay and binding of PF1022A, a new anthelmintic, on the receptors.

We examined the effect of PF1022A, one of the gabergic anthelmintics newly developed in Japan, on gamma-aminobutyric acid (GABA) receptors using a radioligand binding technique in isolated membrane preparations of the nematode Ascaris suum. Membrane protein was prepared from the homogenate of somatic muscle cells after ultracentrifugation. In addition to the basic binding of [2,3-3H-(N)]-GABA, the radioligand [methyl-3H]-bicuculline is used to identify the GABAA receptor, whereas [butyl-4-3H]-baclofen is employed for GABAB receptor sites. The dissociation constants (Kd values) and the maximal numbers of binding sites (Bmax values) from Scatchard plotting for GABA receptors are close to those obtained in mammalian brain. PF1022A displaced in a concentration-dependent way the binding of [2,3-3H(N)]-GABA and [methyl-3H]-bicuculline as did other specific gabergic agents. In addition, PF1022A decreased the binding of [butyl-4-3H]-baclofen at a higher concentration, although this binding did not represent GABAB sites. In a comparison of the inhibition constants (Ki values) of PF1022A with those of other agents, it is conclusive that PF1022A bound with GABA receptors. A direct effect of PF1022A on GABA receptors can thus be postulated.

Animals↗
PubMed2006

A field study on the effect of some anthelmintics on cyathostomins of horses in sweden.

The objective of the study was to investigate different aspects on the efficacy of three anthelmintics on cyathostomin nematodes of Swedish horses. A faecal egg count reduction (FECR) test was performed on 26 farms. Horses were treated orally with recommended doses of ivermectin, pyrantel pamoate or fenbendazole. Faecal samples were collected on the day of deworming and 7, 14 and 21 days later. No resistance was shown against ivermectin; the FECR was constantly >99%. The effect of pyrantel was assessed as equivocal in 6 farms 14 days after treatment; the mean FECR was 99%. As many as 72% of the fenbendazole-treated groups met the criteria for resistance; the mean FECR was 86%, ranging from 56% to 100%. A re-investigation of two farms where pyrantel resistance had been suspected clearly revealed unsatisfactory efficacy of pyrantel on one of these farms; the FECR varied from 72% to 89%. Twenty-six of the horses previously dosed with pyrantel or fenbendazole, and which still excreted >/=150 eggs per gram of faeces 14 days after treatment, were dewormed with ivermectin and fenbendazole or pyrantel in order to eliminate the remaining cyathostomins. A total of 13 cyathostomin species were identified from horses that initially received fenbendazole and seven species were identified from pyrantel-treated individuals. The egg reappearance period (ERP) following treatment with ivermectin and pyrantel was investigated on two farms. The shortest ERP after ivermectin treatment was 8 weeks and after pyrantel was 5 weeks. We conclude that no substantial reversion to benzimidazole susceptibility had taken place, although these drugs have scarcely been used (<5%) in horses for the last 10 years. Pyrantel-resistant populations of cyathostomins are present on Swedish horse farms, but the overall efficacy of pyrantel is still acceptable.

Animals↗
PubMed1982

Inhibition of acetylcholinesterase secretion from Nippostrongylus brasiliensis by benzimidazole anthelmintics.

Treatment of rats infected with Nippostrongylus brasiliensis with a single, oral therapeutic dose of the anthelmintic benzimidazole carbamates oxfendazole or mebendazole resulted, 24 hr later, in a marked reduction (60-90%) in the secretion of a low molecular weight acetylcholinesterase from the parasites when they were incubated in vitro. This effect coincided with the expulsion of parasites from the host as a result of the therapy. When parasites were incubated in vitro with 0.1 mM oxfendazole, mebendazole, flubendazole, parbendazole, cambendazole or thiabendazole a similar effect was observed; with oxfendazole and mebendazole the effect was apparent within 1 hr and lasted for at least 4 hr after removal to fresh, drug-free medium. Whether treated in the host or in vitro the reduction in secretion was balanced by an equivalent rise in acetylcholinesterase activity within the parasites. It is suggested that the inhibition of protein secretion may be a specific manifestation of a general effect of these compounds on microtubule function.

Acetylcholinesterase↗
PubMed1991

Specific interaction of benzimidazole anthelmintics with tubulin from developing stages of thiabendazole-susceptible and -resistant Haemonchus contortus.

The low- and high-affinity binding of tritiated benzimidazole anthelmintics (mebendazole and oxibendazole) to tubulin-containing supernatants derived from unembryonated eggs, third stage larvae or adult worms of thiabendazole-susceptible and -resistant strains of Haemonchus contortus were examined and compared. The displacement of these radioligands by unlabelled benzimidazoles (mebendazole, fenbendazole, thiabendazole and oxibendazole) also was examined. The binding affinity, K alpha, and maximum binding, Bmax, for the high-affinity binding were calculated by non-linear least-square iterative curve fitting using a computer programme (LIGAND) based on the exact mathematical model of ligand-receptor interactions. The K alpha was of the same order of magnitude (x 10(7) M-1) for the susceptible and resistant eggs, larvae and worms. Resistance was associated with a loss of high-affinity binding. There was a 2- to 5-fold loss of Bmax by the resistant strain. The eggs showed greater high-affinity binding per milligram of protein than the larvae which, in turn, showed greater high-affinity binding than the adult worms. It was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis that the tubulin content per milligram of protein decreased from egg, through larvae to adult worm. Cross-displacement studies indicated that different benzimidazole drugs interacted with the same receptor (tubulin) and that a rank order of affinity of the benzimidazole drugs could be inferred.

Animals↗
PubMed1992

Binding of [3H]benzimidazole carbamates to mammalian brain tubulin and the mechanism of selective toxicity of the benzimidazole anthelmintics.

The binding of tritiated benzimidazole carbamates ([3H]BZCs) to mammalian brain tubulin was examined to investigate the kinetics of the BZC-tubulin interaction and to establish the mechanism of the selective toxicity of the BZC based anthelmintics. [3H]BZC binding to tubulin was markedly greater at 4 degrees than at 37 degrees for all ligands. The association constant (Ka) and maximum amount of [3H]BZC bound (Bmax) were temperature dependent for [3H]mebendazole ([3H]MBZ), [3H]oxibendazole ([3H]-OBZ) and [3H]oxfendazole ([3H]OFZ). The Ka and Bmax values obtained for [3H]MBZ, [3H]OBZ and [3H]OFZ, and the comparatively weak binding of [3H]carbendazim, reflected the known in vitro potency of these compounds as microtubule inhibitors. Dissociation of the [3H]MBZ-tubulin complex was also temperature dependent, the first order dissociation rate constant being reduced by two orders of magnitude at 4 degrees compared with that observed for 37 degrees. These results indicate that the binding of BZCs to mammalian brain tubulin is temperature dependent and suggest that temperature induced conformational changes in the tubulin dimer influence the ability of the BZCs to form a stable BZC-tubulin complex. The temperature dependence of BZC binding and the affinity of the BZCs for mammalian tubulin are therefore unlike the BZC-tubulin interaction observed for parasitic nematodes, where optimum BZC binding occurs at 37 degrees and results in the formation of a pseudo-irreversible complex.

Animals↗
PubMed1979

Enhancement of in vitro binding and some of the pharmacological properties of diazepam by a novel anthelmintic agent, Avermectin B1a.

A novel macrocyclic lactone disaccharide anthelmintic agent, Avermectin B1a (AVM) has been found to cause a concentration-dependent increase in the in vitro binding of 3H-diazepam to rat and mouse brain membranes. The increase in binding is manifested as both an increase in the affinity and number of bindings sites for 3H-diazepam. Preliminary in vivo studies demonstrate that AVM can also enhance some of the pharmacological actions of diazepam.

Animals↗
PubMed1984

Heligmosomoides polygyrus: time of anthelmintic treatment and infection parameters in mice exposed to increasing doses of larvae.

Mice were multiply infected with increasing doses of Heligmosomoides polygyrus larvae. On Day 9 or on Day 30 after the beginning of infections, an anthelmintic treatment was administered and its effect on reinfections and egg production was studied. The time of treatment was found to be an important factor, since early treatment produced marked resistance to subsequent infection, whereas a similar effect was not observed for the late treatment. Most immunity appeared after a lag time of about 3 weeks following treatment. Mice placed in direct contact with high doses of larvae had massive infections, and large quantities of worm eggs were recovered in the faeces. After larval doses were no longer given, there was a decrease of the worm burden in both treated and untreated animals. Studies of egg laying showed that the increased resistance induced by the treatment was also responsible for a reduced egg production. The relationship between fertility of H. polygyrus females and the size of young parasite populations was positive, but was negative for older populations. The slope of the regression line of this relationship was steeper in treated than in untreated mice. Egg production by a female worm was depressed to a certain extent by the resistance reactions of the host, but did not decrease below a threshold value of 100 eggs per female per day.

Animals↗
PubMed1992

Characterization of Ca(2+)-ATPase of Setaria cervi (Nematoda: Filarioidea): effect of phenothiazines and anthelmintics.

1. A Mg2+ independent, Ca(2+)-ATPase requiring high concentrations of Ca2+ (5 mM) for the activation, equally distributed in cuticle-muscular-hypodermis, genital organs and gastrointestinal tissues and mainly localized in 10,000 g pellet fraction, was identified in Setaria cervi, a bovine filarial parasite. 2. Filarial enzyme showed Km value of 3.33 mM for ATP as computed from the double reciprocal Lineweaver-Burk plot. 3. The enzyme could be completely solubilized by sonication with about 4-fold increase in specific activity of the enzyme. 4. The enzyme showed about 2-fold activation by the calmodulin fractions isolated from S. cervi and rat brain homogenates. 5. The enzyme was highly sensitive to inhibition with some phenothiazine derivatives. Trifluoperazine was observed to be the most potent inhibitor followed by promethazine and chlorpromazine. 6. Some anthelmintics viz. diethycarbamazine and centperazine were found to be highly potent inhibitors of the enzyme, significant inhibition of filarial Ca(2+)-ATPase was also observed with levamisole and suramine. 7. Studies indicate Ca(2+)-ATPase of S. cervi as a potential chemotherapeutic target.

Animals↗
PubMed1989

Anthelmintic resistance and the control of ovine ostertagiasis: a drug action model for genetic selection.

A site-specific genetic prediction model is presented, which examines the influences of different anthelmintic treatment regimens on selecting for drug resistance within a sheep management system. The model exploits the power of modern microcomputers to integrate factors such as parasite strain, geographic location, management practice and genetic fitness to identify effective control regimens which do not lead to resistant Ostertagia circumcincta strains over a 30-year horizon. The potential use of the model as a farm level management-support tool is discussed.

Animals↗
PubMed1991

Response of pre-adult and adult stages of Trichuris muris to common anthelmintics in mice.

The common anthelmintics, oxantel, mebendazole, albendazole and pyrantel were assessed for their comparative activity against Trichuris muris in mice. Mice were infected with T. muris and the infection was maintained by a brief cortisone administration during the second week of infection. Mice carrying the infection with different life cycle stages, viz. fourth stage larvae (L4), pre-adult and adult stages were dosed with anthelminitics. The worm burdens in control infection groups varied although infection dose and other conditions were uniformly followed. With various dose regimens tested, oxantel was highly potent; it eliminated completely pre-adult and adult stages, respectively at 25 and 12.5 mg kg-1 dose levels with significant activity also against adult worms at a 1.56 mg kg-1 dose level and against pre-adults at a 6.25 mg kg-1 level. Pre-adults required twice the dose given to that of adults for complete (100%) activity. Mebendazole was the next most active; a dosage of 37.5 mg kg-1 was completely active against pre-adults whereas a dosage of 2 x 50 mg kg-1 was required for complete elimination of adult worms. In addition, about 90% of the worms were eliminated with a single dose of 150 mg kg-1. However, a significant activity was seen against adults at a 25 mg kg-1 level and pre-adults at 37.5 mg kg-1, the lowest level tested. In comparison, albendazole did not induce complete clearance of pre-adult and adult stages even when tested at dose levels as high as 150 and 2 x 75 mg kg-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Albendazole↗
PubMed1993

An outbreak of haemonchosis associated with anthelmintic resistance in sheep.

An outbreak of haemonchosis associated with anthelmintic resistance was recorded in a flock of 150 crossbred lambs. Closantel and ivermectin were 100% effective against Haemonchus contortus while fenbendazole and morantel reduced faecal egg counts by 87 and 29%, respectively. Levamisole showed an efficacy of 95%. At double the recommended dose (10 mg kg-1), fenbendazole had an efficacy of 99% against H. contortus infection. This appears to be the first report of an outbreak of haemonchosis associated with fenbendazole and morantel resistance in a strain of H. contortus in sheep.

Animals↗
PubMed1977

Mutagenicity tests on anthelmintics: microsomal activation of viprynium embonate to a mutagen.

Eight anthelmintic preparations readily available in Australia were tested for mutagenicity in the Salmonella typhimurium test system. A slightly modified version of the procedure recommended by Ames et al. [2] was adopted, in that the test samples were placed in "wells" cut out of the agar of a plate previously seeded with the appropriate tester strain. Addition of a mixture of rat liver microsomal enzymes and appropriate co-factors ("S-9 mix") to one of the two wells on a single plate allowed a possible requirement for metabolic activation to be recognised. Using this procedure, viprynium embonate was found to be non-mutagenic. It was however, activated by the rat liver microsome preparation to a mutagen capable of causing both base-pair substitution (detected with strain TA100) and frameshift (detected with strain TA98) mutations. The other seven compounds tested all gave negative results in this system.

Animals↗
PubMed1978

Studies with Brugia pahangi. 20. An investigation of 23 anthelmintics using different screening techniques.

23 anthelmintics were tested against Brugia pahangi microfilariae and infective larvae in vitro and in Aedes aegypti infected with B. pahagi and jirds (Meriones unguiculatus) infected with a B. pahangi/patei hybrid. There was little correlation between the results obtained in vitro and in infected insects and the results obtained in these tests gave no indication of the activity in jirds. Three of the compounds were macrofilaricidal in jirds and these were tested in cats infected with B. pahangi. One of these--5-benzamido-2(4-thiazolyl)-benzimidazole--was macrofilaricidal in cats and it is suggest that it should be tested in other filarial systems. It is concluded that the insect and in vitro tests are not good primary screens for filaricidal activity.

Aedes↗
PubMed1979

The anthelmintic effects of flubendazole on Brugia pahangi.

The anthelmintic effects of flubendazole (methyl [5-(4-fluorobenzoyl)-1-H-benzimidazol-2-yl] carbamate) (Janssen Pharmaceutica) were evaluated in jirds (Meriones unguiculatus) and cats (Felis cattus) infected with Brugia pahangi. Flubendazole was macrofilaricidal at 5 x 2.5 mg/kg and 1 x 25 mg/kg in jirds and 1 x 100 mg/kg in cats when administered by subcutaneous injection. It also killed developing larvae in jirds. It was not microfilaricidal.

Animals↗
PubMed1983

The anthelmintic effects of flubendazole on Trichuris trichiura and Ascaris lumbricoides.

Flubendazole is an effective anthelmintic against both Trichuris trichiura and Ascaris lumbricoides. Single doses of 200 mg, 500 mg and 600 mg flubendazole, or two doses of 300 mg flubendazole on two consecutive days, effectively reduced egg output of both helminths by over 90%. Cure rates of 90.0 to 97.0% were obtained in Ascaris infections but only 17.3 to 65.1% of Trichuris infections were completely cured with the various single-dose or two-dose regimes. Flubendazole did not cause erratic migration of Ascaris in mixed infections at any of the dosages used.

Anthelmintics↗
PubMed1985

Resistance of dogs to reinfection with Ancylostoma ceylanicum following anthelmintic therapy.

A model of human hookworm infection has been developed which shows that dogs with chronic hookworm infection are considerably resistant to reinfection one month after the termination of the primary infection with anthelmintics. Challenge and control dogs were infected with 1,800 larvae and the infection was followed for six weeks. When compared with control dogs, faecal egg excretion and intestinal adult worm burdens in challenge dogs were reduced by 85% and 77%, respectively. Infection had no significant effect on haemoglobin concentrations, total white cell counts, platelet levels or spontaneous and phytohaemagglutinin-induced lymphocyte transformations in both control and previously infected dogs. Both groups of dogs developed an eosinophilia and lymphocytes responded transiently to stimulation with both larval and adult worm antigens, although there were no significant differences between the two groups of animals. Specific IgM antibodies were transient in both groups of animals following infection. Specific IgG antibodies were present at high levels before infection in challenge dogs when compared with control dogs, and fell transiently after challenge; three weeks after infection, IgG antibodies appeared in the control animals and titres continued to rise during the period of observation. Challenge dogs also developed specific IgA antibodies three weeks after infection, and these remained at high levels, but these antibodies were not detected in control dogs. Thus, dogs infected with this strain of the hookworm, Ancylostoma ceylanicum, which has been shown to infect man, develop functional protective immunity. These findings improve prospects for vaccine development.

Ancylostomiasis↗