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PubMed1988

Efficacy of various anthelmintics against third-stage larvae of Ancylostoma caninum in the brain of mice.

In an experimental larval infection of Ancylostoma caninum in mice, the efficacy of various anthelmintics against the larvae migrated and established in the brain is reported for the first time. Albendazole and flubendazole were the most effective drugs. Thiabendazole, benacil, phenacizole, oxfendazole and mebendazole showed significant larvicidal activity. Tetramisole, levamisole, fenbendazole, Sch 18099, pyrantel pamoate, morantel tartrate and oxantel pamoate did not show any significant activity even at relatively high dose levels.

Ancylostoma↗
PubMed1990

The anthelmintic activity of a novel organic arsenical, R7/45, upon Brugia pahangi in Meriones unguiculatus.

The new organic arsenical R7/45 is a rapidly acting and very potent anthelmintic against adult Brugia pahangi in jirds. Against adult worms implanted into the peritoneal cavity 5 subcutaneous (SC) injections at 2.5 mg/kg of R7/45 killed 100% of adult worms. A single dose SC of 20 mg/kg was 100% effective and 10 mg/kg 76% effective against adult worms. When jirds were autopsied at different times after treatment at 20 mg/kg SC 89% of worms were dead within three days. R7/45 was not active when given by stomach intubation. Pretreatment of jirds with R7/45 had no effect on adult worms subsequently implanted into jirds. R7/45 was highly active against third and fourth stage larvae of B. pahangi in jirds.

Animals↗
PubMed1995

Effects of the anthelmintics clorsulon, rafoxanide, mebendazole and arprinocid on Echinostoma caproni in ICR mice [corrected and reapublished in J Helminthol 1996 Mar;70(1):95-6].

Female ICR mice, 5 to 6 weeks old, were exposed by stomach tube to 25 metacercarial cysts of Echinostoma caproni per mouse. At 14 days post-exposure, mice were fed by stomach tube clorsulon (1000 mg/kg, 500 mg/kg and 100 mg/kg) or rafoxanide (50 mg/kg, 25 mg/kg and 5 mg/kg) dissolved in dimethylsulphoxide (DMSO) carrier and mebendazole (1000 mg/kg and 500 mg/kg) or arprinocid (100 mg/kg and 50 mg/kg) suspended in a 2:1 polyethylene glycol (PEG)/DMSO carrier. All drugs were obtained from Merck Inc. (Rahway, New Jersey, USA) and only single dose regimes were used. Experimentally infected mice that served as controls received either DMSO or 2:1 PEG/DMSO carriers or were not given the carrier. Mice were necropsied 15v, 16, 18 and 20 days postexposure to worms. Doses of 100 mg/kg of clorsulon and 50 mg/kg of rafoxanide were 100% effective in eliminating the echinostomes on day 1 post-administration of the anthelmintics. Mebendazole and arprinocid were ineffective in eliminating worms at 1 or 2 days post drug administration.

Adenine↗
PubMed1996

Effects of the anthelmintics clorsulon, rafoxanide, mebendazole and arprinocid on Echinostoma caproni in ICR mice.

Female ICR mice, 5 to 6 weeks old, were exposed by stomach tube to 25 metacercarial cysts of Echinostoma caproni per mouse. At 14 days post-exposure, mice were fed by stomach tube clorsulon (1000 mg/kg, 500 mg/kg and 100 mg/ kg) or rafoxanide (50 mg/kg, 25 mg/kg and 5 mg/kg) dissolved in dimethylsulphoxide (DMSO) carrier and mebendazole (1000 mg/kg and 500 mg/ kg) or arprinocid (100 mg/kg and 50 mg/kg) suspended in a 2:1 polyethylene glycol (PEG)/DMSO carrier. All drugs were obtained from Merck Inc. (Rahway, New Jersey, USA) and only single dose regimes were used. Experimentally infected mice that served as controls received either DMSO or 2:1 PEG/DMSO carriers or were not given the carrier. Mice were necropsied 15, 16, 18 and 20 days postexposure to worms. Doses of 100 mg/kg of clorsulon and 50 mg/kg of rafoxanide were 100% effective in eliminating the echinostomes on day 1 post-administration of the anthelmintics. Mebendazole and arprinocid were ineffective in eliminating worms at 1 or 2 days post drug administration.

Adenine↗
PubMed1985

The efficacy of some newer broad spectrum anthelmintics against third-stage larvae of Ancylostoma caninum in the mouse.

The efficacy of eight anthelmintics against Ancylostoma caninum larvae in the skeletal muscles of mice was evaluated. Levamisole (5 X 40 mg/kg), thiabendazole (5 X 400 mg/kg), oxfendazole (5 X 100 mg/kg), albendazole (5 X 100 mg/kg), flubendazole (5 X 200 mg/kg), benacil (5 X 200 mg/kg) and phenacizole (5 X 200 mg/kg) showed marked larvicidal activity (98 to 99%). Sch 18099 did not show larvicidal activity even at 5 X 400 mg/kg.

Albendazole↗
PubMed1986

Anthelmintic activity of triclabendazole.

Triclabendazole was tested in vitro and in vivo against a range of helminths. Although in vitro activity was found against Hymenolepis diminuta (0.5 microgram/ml), Fasciola hepatica (2.5 micrograms/ml), Taenia crassiceps and Schistosoma mansoni (50 micrograms/ml), in vivo activity was only found against F. hepatica, a single oral dose of 40 mg/kg killing 99% of adult flukes in the rat. This spectrum of activity suggests a mechanism of action unlike that of other benzimidazole anthelmintics.

Animals↗
PubMed1988

Effect of repeated anthelmintic treatment on ability to detect predisposition of mice to Heligmosomoides polygyrus and Aspiculuris tetraptera (Nematoda) infections.

Several recent studies have demonstrated predisposition of certain humans to heavy gastro-intestinal nematode infections. This finding has been used to support the concept of community control of nematodes based on selective treatment of the few heavily infected individuals in the community. A mouse model has been used in this study to determine whether those individuals found to be 'predisposed' to heavy infection continue to regain heavy nematode infections following repeated anthelmintic treatments. Re-infection was examined over 3 intervals of 8 weeks in 52 mice and individual worm burdens attained following drug-induced expulsion were analysed. In the case of Heligmosomoides polygyrus, parasite numbers obtained after first treatment were only significantly correlated with those obtained after the second treatment. Re-infection levels in mice during the second and third re-infection periods did not correlate with parasite loads at the beginning of the study. In the case of Aspiculuris tetraptera, correlations after each re-infection period remained significant, although the magnitude of the correlation coefficient decreased with successive re-infection intervals. The data suggest that a selective control programme based on repeated screening to identify heavily infected individuals prior to each treatment would reduce the number of H. polygyrus in the host population 17.6% more than a single screening at the beginning of the control programme, and would reduce the number of A. tetraptera by 14% more than a single screening. Re-infection rates for H. polygyrus were shown to decrease with increasing mouse age whereas re-infection rates for A. tetraptera increased with increasing mouse age.

Age Factors↗
PubMed1992

Effects of three anthelmintics on the tegument of Hymenolepis fraterna (Cestoda).

The in vivo effects of the anthelmintics taenifugin, VUFB 14170 and VUFB 15269 on the tegument of Hymenolepis fraterna have been examined by SEM, TEM and cytochemistry. The drugs were given to H. fraterna-infected mice on the 14th day post-infection in a single oral dose of 150, 200 and 200 mg/kg, respectively. By 72 h post-treatment, the drug-induced pathomorphological changes in the tegument indicated that all three drugs had a significant effect. Changes were most pronounced on the brush border and in the intercellular material. On the apical surface, there was blebbing as well as accumulation of membrane fragments over the microthrix tips and erosion of the brush border. The intercellular material was changed in structure, showing increased electron density in some areas and oedema of the intercellular spaces in other areas. There were also fractures of the tegument of variable depth, sometimes reaching to the parenchyma. These results suggest altered tegumental integrity and, occasionally, complete disruption of the selective permeability barrier created by the normal tegument. This suggestion is further supported by the penetration of ruthenium red into some tegumental areas and its distribution into the intercellular spaces, down to the parenchyma. The intrategumental lysosomes also appeared to be significantly activated. There was evidence of autophagy in both distal cytoplasm and tegumental cells. Mature and gravid proglottides were more susceptible to drug damage than those in the anterior strobila and neck.

Acid Phosphatase↗
PubMed2002

Effects of macrocyclic lactone anthelmintics on feeding and pharyngeal pumping in Trichostrongylus colubriformis in vitro.

The effects of macrocyclic lactone anthelmintics (MLs) on feeding by Trichostrongylus colubriformis nematodes in vitro were examined using inulin uptake as a measure of ingestion and electropharyngeograms as a record of the electrical events associated with pharyngeal pumping. Inulin uptake was inhibited by the 4 MLs tested (EC50s 0.045-4.57 nM), with an order of potency of eprinomectin (most potent), ivermectin, ivermectin monosaccharide, and ivermectin aglycone. The MLs caused both the frequency and amplitude of pharyngeal electrical events to decrease. In individual worms the inhibition of pump frequency preceded the inhibition of pump amplitude. The order of potency of the MLs as inhibitors of frequency was ivermectin aglycone, ivermectin, ivermectin monosaccharide and eprinomectin. The difference compared with the inulin assay results are probably due to the dynamics of drug uptake in the two systems. It was possible that the nematodes in the electrophysiology experiments were effectively orally ligated by enclosure of the worm's head in the recording pipette which contained no drug. Despite this difference in relative potencies, both the ingestion assays and the electrical events indicate that MLs are potent inhibitors of the pharynx in T. colubriformis in vitro. The sequence of effects on pharyngeal electrical activity suggests that ML action involves an initial inhibitory effect on the rate of pharyngeal contractions, followed by a decrease in the amplitude of the potentials associated with pharyngeal pumping events.

Animals↗
PubMed2003

The effect of the anthelmintic emodepside at the neuromuscular junction of the parasitic nematode Ascaris suum.

Here we report on the action of the novel cyclo-depsipeptide anthelmintic, emodepside, on the body wall muscle of the parasitic nematode, Ascaris suum. Emodepside caused (i) muscle relaxation, (ii) inhibition of muscle contraction elicited by either acetylcholine (ACh), or the neuropeptide, AF2 (KHEYLRFamide) and (iii) a rapid relaxation of muscle tonically contracted by ACh. The inhibitory action of emodepside on the response to ACh was not observed in a denervated muscle strip, indicating that it may exert this action through the nerve cord, and not directly on the muscle. Electrophysiological recordings showed emodepside elicited a Ca(++)-dependent hyperpolarization of muscle cells. Furthermore, the response to emodepside was dependent on extracellular K+, similar to the action of the inhibitory neuropeptides PF1 and PF2 (SDPNFLRFamide and SADPNFLRFamide). Thus emodepside may act at the neuromuscular junction to stimulate release of an inhibitory neurotransmitter or neuromodulator, with a similar action to the PF1/PF2 neuropeptides.

Acetylcholine↗
PubMed2005

Nematode neuropeptide receptors and their development as anthelmintic screens.

This review addresses the potential use of neuropeptide receptors for the discovery of anthelmintic agents, and particularly for the identification of non-peptide ligands. It outlines which nematode neuropeptides are known and have been characterized, the published information on drug discovery around these targets, information about existing high- and low-throughput screening systems and finally the likely safety of neuropeptide mimetics.

Animals↗
PubMed2006

In vitro and in vivo anthelmintic efficacy of plant cysteine proteinases against the rodent gastrointestinal nematode, Trichuris muris.

Extracts of plants, such as papaya, pineapple and fig, are known to be effective at killing intestinal nematodes that inhabit anterior sites in the small intestine, such as Heligmosomoides polygyrus. In this paper, we demonstrate that similar in vitro efficacy also occurs against a rodent nematode of the large intestine, Trichuris muris, and confirm that the cysteine proteinases present in the plant extracts are the active principles. The mechanism of action of these enzymes involved an attack on the structural proteins of the nematode cuticle, which was similar to that observed with H. polygyrus. However, not all plant cysteine proteinases were equally efficacious because actinidain, from the juice of kiwi fruit, had no detrimental effect on either the motility of the worms or the nematode cuticle. Papaya latex was also shown to significantly reduce both worm burden and egg output of mice infected with adult T. muris, demonstrating that enzyme activity survived passage to the caecum and was not completely inactivated by the acidity of the host's stomach or destroyed by the gastric or pancreatic proteinases. Thus, the cysteine proteinases from plants may be a much-needed alternative to currently available anthelmintic drugs due to their efficacy and novel mode of action against different gastrointestinal nematode species.

Actinidia↗
PubMed2000

Electrophysiological investigation of anthelmintic resistance.

It is pointed out that two of the three major groups of anthelmintic act by opening membrane ion-channels. It is appropriate, therefore, to use electrophysiological methods to study the properties of the sites of action of these drugs and the changes in the properties of these receptor sites associated with resistance. This paper describes the use of the patch-clamp technique to observe the currents that flow through the levamisole-activated channels as they open and close in levamisole-sensitive and levamisole-resistant isolates. It was found that, on average, the proportion of time the channels are open, is less in the resistant isolate. The patch-clamp technique also showed that the ion-channels are heterogeneous and that one of the subtypes is lost with the appearance of resistance. The use of the current clamp technique is illustrated to record a site of action of ivermectin in the pharyngeal muscle of Ascaris.

Animals↗
PubMed2000

The development of anthelmintic resistance in sheep nematodes.

Anthelmintic resistance now poses problems to sheep farmers throughout the world. In some Southern hemisphere countries multiple resistance has reached levels which make sheep farming non-sustainable. Evidence from studies in the UK and Europe suggests (a) that the selection process occurs over a longer time frame than in Southern tropical/temperate regions and (b) that for some of the key ovine species little or no reversion to susceptibility may occur for many years after the withdrawal of the selecting agent. The dynamics of the selection process are influenced by a number of host, parasite, drug, management and environment-dependent factors. Recent mechanistic studies on resistance against avermectins and milbemycins (AM) suggest that there may be a number of mechanisms associated with resistance at the different target sites for these drugs. Within Europe endectocides within the AM drug group have now become the crucial element in strategies aimed at controlling important diseases such as sheep scab and nematodoses. Given that there is little likelihood of a series of novel action compounds emerging in the immediate future to replace this family the conservation of efficacy of the AM group should be accorded the highest priority for research in this area.

Animal Husbandry↗
PubMed1991

Synthesis and biological activity of a series of diaryl-substituted alpha-cyano-beta-hydroxypropenamides, a new class of anthelmintic agents.

A series of alpha-cyano-beta-hydroxypropenamides was prepared and tested for anthelmintic activity. alpha-Cyano-beta-hydroxy-N-[4- (trifluoromethyl)phenyl]-3-[4-(trifluoromethyl)phenyl]propenamide (1) showed good activity against the nematode Nematospirodes dubius in a mixed parasite infection in mice; several of the analogues were also effective against the cestode Hymenolepis nana. In sheep trials, 1 caused 100% reduction of the hematophagous nematode Haemonchus contortus after a single dose of 20 mg/kg but did not show satisfactory control of Trichostrongylus colubriformis or Ostertagia circumcincta. Against the liver fluke Fasciola hepatica, 1 suppressed egg production but only temporarily, suggesting that the adult flukes were not eliminated. Mechanism of action studies on 1 using Ascaris mitochondria showed it to be an uncoupler of oxidative phosphorylation.

Amides↗
PubMed1981

Isomeric phenylthioimidazo[1,2-alpha]pyridines as anthelmintics.

A series of isomeric imidazo[1,2-alpha]pyridine-2-carbamates was prepared for testing as anthelmintics. The analogues were synthesized by reacting the appropriate 2-aminopyridine and methyl chloroacetylcarbamate. Steric hindrance in the 2,6-disubstituted derivative resulted in the formation of the isomeric 3-substituted analogue as the major product. Carbon-13 NMR proved useful in the structural assignments in this series. None of the analogues exhibited the potency of methyl 6-(phenylsulfinyl)imidazo[1,2-alpha]pyridine-2-carbamate when tested against Nematospiroides dubius in mice.

Animals↗
PubMed1986

Studies in potential filaricides. 18. Synthesis of 2,2'-disubstituted 5,5'-dibenzimidazolyl ketones and related compounds as potential anthelmintics.

A series of 2,2'-disubstituted 5,5'-dibenzimidazolyl ketones and related compounds have been synthesized of which 2,2'-bis(carbomethoxyamino)-5,5'-dibenzimidazolyl ketone exhibited a broad spectrum of anthelmintic activity in experimental animals. At doses of 10-50 mg/kg given intraperitoneally, 5 killed 100% of the adult worms of Litomosoides carinii, Dipetalonema viteae, and Brugia malayi. By the oral route the macrofilaricidal efficacy of 5 was 97-100% at 100-200 mg/kg X 5 days. The treated animals showed gradual disappearance of microfilariae and before autopsy they became amicrofilariaemic. Some of the compounds also showed 100% efficacy against the human hookworms and tapeworm, Ancylostoma ceylanicum in hamsters, and Hymenolepis nana in rats at a single oral dose of 50-250 mg/kg. Compound 5 was also effective against Syphacia obvelata in mice at a single oral dose of 100 mg/kg and was found to be well tolerated by mice up to an oral dose of 2500 mg/kg.

Animals↗