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The dose response of several benzimidazole anthelmintics against resistant strains of Haemonchus contortus and Trichostrongylus colubriformis selected with thiabendazole.

Dose response lines for eight benzimidazole anthelmintics and thiophanate were determined, using standardised strains of thiabendazole selected and resistant Haemonchus contortus and Trichostrongylus colubriformis. Against H contortus, thiophanate, thiabendazole, parbendazole and oxibendazole were inactive. Mebendazole was inactive at dose rates of 6.26 and 12.5 mg/kg, although significant activity occurred at 25 mg/kg. Fenbendazole, cambendazole, oxfendazole and albendazole demonstrated significant activity at dose rates equal to or greater than the recommended therapeutic level. Thiophanate was inactive against resistant T colubriformis. The remaining compounds only showed significant activity when used at dose rates in excess of the recommended therapeutic level. These results show that a side resistance exists among the benzimidazole anthelmintics and suggests that changes in dose response lines could be expected to occur if resistant strains are selected with benzimidazoles other than thiabendazole.

Animals↗

Methyl 5(6)-4-2-pyridyl piperazino carbamoyl benzimidazole-2-carbamate--a new broad spectrum anthelmintic.

Methyl 5(6)-4-2-pyridyl piperazino carbamoyl benzimidazole-2-carbamate (CDRI Comp. 81-470) was tested against various nematode and cestode infections in different experimental and domestic animals. The compound showed 100% effectivity against adult of Ancylostoma ceylanicum (hookworm) in hamsters (6.25 mg/kg p.o. X 1), Nippostrongylus brasiliensis (trichostrongylid) in rats (100 mg/kg p.o. X 3), Hymenolepis nana (cestode) in rats (25 mg/kg p.o. X 1) and Syphacia obvelata (oxyurid) in mice (12.5 mg/kg p.o. X 3). It was also found highly effective against artificial and natural helminth parasites of higher animals. The compound removed all, A. caninum and A. ceylanicum (hookworms) and Toxocara sp. (ascarid) from dogs at a dose of 10 mg/kg p.o. X 3; A. tubaeformis (hookworm) and Toxocara sp. at 25 mg/kg p.o. X 3 and 2.5 mg/kg p.o. X 3 respectively from cats and Ascaridia galli (ascarid) at 10 mg/kg p.o. X 3 from fowl. The compound in doses of 1500 mg/kg by oral route and 1000 mg/kg by i.p. route did not cause any mortality or produce adverse effect in mice. The expanded anthelmintic action and large therapeutic index indicate compound's great anthelmintic potentiality.

Animals↗

Anthelmintic treatment of prepatent stephanuriasis with flubendazole, levamisole and disophenol and the effects on liver-specific serum enzymes.

Haematological parameters and liver specific serum enzymes were examined in pigs during the first 12 weeks of liver migration of larvae following experimental infection with 1000 infective Stephanurus dentatus larvae. No significant changes in total red blood cell counts, packed cell volume, or haemoglobin content were observed. Total white blood cell counts and circulating eosinophils rose rapidly from days 5 and 19 after infection, respectively. Treatment with a mixture of levamisole (LEV) at 10 mg/kg and flubendazole (FLU) at 50 mg/kg in feed four weeks after infection halted the leucocyte response and returned values to normal in two weeks. Disophenol (DIP) at 15 mg/kg subcutaneously restricted the leucocyte response but it was only terminated following FLU treatment alone on day 61. No effects of S dentatus or either anthelmintic treatments on liver specific serum enzymes glutamate dehydrogenase, sorbitol dehydrogenase or gamma-glutamyl transpeptidase were found. Animals killed seven, 26 and 54 days after treatment showed significant resolution of fibrotic liver lesions after LEV + FLU but not after DIP. We conclude that LEV + FLU is an effective treatment for prepatent stephanuriasis but that liver damage is insufficiently traumatic to release sufficient enzymes into serum to be pathognomonic or to assess anthelmintic efficacy.

Animals↗

Anthelmintic coumarin from Ethulia conyzoides var. gracilis Asch. & Schweinf.

The alcoholic extract of aerial parts of Ethulia conyzoides var. gracilis Asch. & Schweinf. exhibits a significant anthelmintic activity when tested in vitro against Ascaris lumbricoides using santonin as a reference. Four coumarins were isolated and identified; ethuliacoumarin A was found to be responsible for the anthelmintic activity.

Animals↗

[Resistance to nematodes to anthelmintics].

Resistance of nematodes to anthelmintics is being increasingly observed throughout the world in recent years. Benzimidazole-resistance of Haemonchus contortus is also observed in the Netherlands. There are a number of methods to detect resistance to anthelmintics of which only the in vitro techniques can be used to detect resistance in the field. Factors such as dosage, frequency of treatment and the time of treatment may affect resistance.

Animals↗

Anthelmintic activities of ivermectin against gastrointestinal nematodes of cattle.

The anthelmintic efficacy of ivermectin, a combined solution of the B1a and B1b fractions of avermectin, was assessed in a controlled trial. Twenty-four yearling calves experiencing naturally acquired, clinical gastrointestinal helminthiasis were evenly divided on the basis of weight into two 12-animal groups. The medicated group was given (subcutaneously) ivermectin at the dose rate of 200 microgram/kg of body weight. The control animals were given the vehicle alone, at an equivalent rate. All animals were killed 14 days later. At necropsy of the calves, gastrointestinal helminth arithmetic means were 178,626 and 575 for the control and the treated groups, respectively, an overall reduction of 99.7%. Nematodes which were present at substantial levels were Ostertagia ostertagi, O lyrata, Trichostrongylus axei, Cooperia punctate, C oncophora, C mcmasteri, and Oesophagostomum radiatum. Anthelmintic activity of ivermectin was excellent regardless of nematode species, sex, or stage of development.

Animals↗

Investigations for anthelmintic resistance in gastrointestinal nematodes from goats.

Field results from a commercial goat herd, based on egg counts and larval differentiation, suggested that anthelmintic resistance was present to albendazole, fenbendazole, levamisole, morantel, naphthalophos and phenothiazine. When the isolate was tested in sheep, using levamisole or oxfendazole, a possible resistance was shown for Trichostrongylus sp but no resistance was demonstrated in Haemonchus or Ostertagia spp. Ivermectin at a dose rate of 100 micrograms/kg was more than 98 per cent efficient in removing the adults of each of the three species of nematode. The phenomenon relating to the influence of the host on anthelmintic resistance is discussed.

Animals↗

Controlled release of anthelmintic drugs: a new concept for prevention of helminthosis in sheep.

Anthelmintic effects of oxfendazole continuously released at 0:17, 0.28 and 0.47 mg/kg/day from intraruminal capsules were assessed in groups of sheep artificially infected with Ostertagia circumcincta. Removal of worms was directly related to both release rate and plasma concentrations of drug. At the highest level, worm burdens were removed within seven days of administration and anthelmintic efficiency was 99.9 +/- 0.04, 99.3 +/- 0.5 and 98.9 +/- 0.7 per cent against adult worms, developing fourth stage and early fourth stage larvae respectively. In a field experiment, comparisons were made of the parasitological and animal production differences between groups of weaned lambs which were given no treatment, a single oral dose of 5 mg/kg oxfendazole and capsules releasing either 0.24 or 0.48 mg/kg oxfendazole daily. By four days after administration of capsules worm egg counts were reduced and remained below detectable levels for up to 86 days. Worm counts from 'tracer' and flock sheep showed a reduction in worm numbers, especially for Trichostrongylus spp. Compared with untreated controls, live weight gain and fleece weight of sheep given capsules releasing 0.48 mg/kg oxfendazole daily was increased.

Animals↗

Anthelmintic activity of closantel against Ancylostoma caninum in dogs.

The efficacy and minimum therapeutic dose of closantel, an injectable salicylanilide anthelmintic, was evaluated on adult Ancylostoma caninum. Doses of 7.5 and 10 mg/kg had a marked anthelmintic effect on adult stages, removing 99 and 98%, respectively. A second experiment tested the efficacy of closantel against hypobiotic larval stages of A. caninum. A dose of 20 mg/kg did not affect the abundance of arrested hookworm larvae or prevent their subsequent development, but it may have inhibited their full maturation as adult worms so that patent, intestinal infections did not occur. Small numbers of adults were recovered from treated dogs at 29, 43, and 57 days post-treatment, but no eggs were passed in their feces. These studies bear on the practical problem of control of hookworms in dogs.

Ancylostoma↗

Influence of plasma A esterase on anthelmintic action of haloxon in sheep.

Controlled trials were conducted to evaluate the anthelmintic action of haloxon in 2 phenotypes of lambs, 1 having an A esterase in plasma which rapidly hydrolyzes di-(2-chloroethyl)aryl phosphates and the other without this enzyme. A total of 116 lambs, 57 with and 59 without the plasma A esterase, 6 to 9 months old, harboring naturally acquired nematode infections were used in 3 trials. Haloxon was administered orally at 20, 25, and 35 mg/kg of body weight. Nematodes against which haloxon was evaluated in the abomasum were Ostertagia circumcincta and Trichostrongylus axei and in the small intestine were T vitrinus, T colubriformis, Nematodirus spathiger, and N filicollis. The anthelmintic efficiency of haloxon did not differ in the 2 phenotypes of sheep.

Animals↗

Relationship among particle size distribution, dissolution profile, plasma values, and anthelmintic efficacy of oxfendazole.

Three mean particle sizes of oxfendazole raw material (1.65 micron, lot A; 3.2 micron, 10t B; 12.0 micron, lot C) were prepared and identically formulated as corresponding (A, B, and C) suspensions at 2.26% (W/V) concentration. Studies involving microscopic examination, scanning electron microscope analysis, particle size distribution, and surface area measurement were carried out on raw materials. In vitro dissolution profiles were obtained for the suspensions. A comparative bioavailability study of these 3 suspensions was performed in 12 sheep with each sheep given each formulation in a Latin square crossover study design; oxfendazole was dosed at rate of 5 mg/kg of body weight. Plasma-value measurements were made followed by an analysis of various bioavailability studies. Plasma area values indicated that suspension C (dw = 12.0 micron) was significantly (P less than 0.05) less bioavailable than was suspension A (dw = 1.65 micron); there was no difference between suspension A and suspension B. Significant differences were not seen in biological half-life and maximum plasma concentrations. The term dw refers to that particle diameter (determined by Coulter counting) at which 50% of the oxfendazole mass was in the form of particles having a lesser diameter and 50% was in the form of particles having a greater diameter. In a separate study involving 20 Merino weaner sheep infected with benzimidazole-resistant Haemonchus contortus larvae, oxfendazole's anthelmintic efficacy was demonstrated in the 2.26% suspension dosage form (90% particles less than 10 micron) at a dosing rate of 5 mg/kg. A correlation was found between its anthelmintic activity and plasma area values when compared in individual sheep. Data demonstrated that substantial differences in particle size distribution of oxfendazole could influence its dissolution rate, plasma concentrations, and absorption characteristics, thus indicating that oxfendazole's absorption could be dissolution-rate limited.

Administration, Oral↗

Efficacy of common broad spectrum anthelmintics against hook worm, Ascaris and Trichiuris in Hat Yai district, Songkhla Province, Thailand.

1. The third therapeutic scheme should be used in the hospital. 2. The second and third therapeutic scheme may be used in mass treatment. 3. The 4th-6th therapeutic scheme is to be considered, reviewed, and evaluated. 4. Model and technology of permanent worms control is to be studied. 5. The treatment and control of Ascaris were simple. Cure with low reinfection rate and long reinfection period was remarkable. 6. The prevalence rate and reinfection rate of Trichiuris was high, and not so sensitive to any antelmintics. 7. The reinfection rate in the second group was not superior to the first group and the third group. This revealed no effectiveness of ovicidal and larvicidal on the helminthiasis. 8. Reinfection rate in the third therapeutic scheme was the least group. 9. Toxicity and side effect were not found in any anthelmintics. 10. Broad Spectrum Anthelmintics are necessary in mass treatment or blind treatment.

Albendazole↗

[In vitro study of anthelmintic influence on activities of digestive enzymes in extracts from the gut of Ascaris suum and pig's pancreas].

The effect of eight anthelmintics (Rintal, Fenbesan, Telmin, Banminth, Pyrantel, Nilverm, Levamisol and Bioscardina) on the alpha- and gamma-amylases, trypsin, and lipase from pig's pancreas and gut of Ascaris suum was determined. In extracts from A. suum gut also the maltase, trehalase and saccharose activities were examined. All drugs tested did not influence on the host's alpha-amylase. Telmin and Bioscardina were inhibitors of gamma-amylase, Rintal and Telmin--of trypsin, Fenbesan and Bioscardina--of lipase from pig's pancreas. Among the parasite's enzymes the lipase was the most sensitive. Its activity was decreased (35-60%) by Telmin, Nilverm and both pyrantel derivatives. The activity of maltase and trehalase was reduced by Levamisole and Banminth, that of saccharose by Levamisole. It is concluded that the anthelmintics Levamisole and Banminth seemed the most efficient among the tested drugs because they did not alter the activity of host's enzymes and, showed the inhibitory effect on three of parasite's enzymes.

Animals↗

[Anthelmintic control of multiresistant nematodes in the gastrointestinal tract of imported goats].

Multiple resistant strains of Ostertagia and Trichostrongylus were detected in a flock of cashmere and angora goats imported from New Zealand. The ED50 values detected by in vitro EHA test were from 0.27 to 0.36 micrograms/ml (while the reference value of sensitivity is 0.10 microgram/ml TBZ). Multiple resistance to all the types of currently used anthelmintics was confirmed by in vivo FECRT, when the efficacy of recommended doses was lower than 90% (albendazole 74%, levamisole 86%, ivermectin 83%). Two control schemes were investigated. In the simultaneous application of anthelmintics in the double or triple of recommended doses (0.4 mg/kg ivermectin s.c., 30 mg/kg levamisole and 20 mg/kg albendazole p.o.) was effective. Examination of goats 7 and 8 months after treatment revealed the repeated presence of multiple resistant gastrointestinal nematodes. It is the first published case of intercontinental transfer of resistant strains of nematodes when importing small ruminants.

Animals↗

Overberg research projects. XV. The efficacy of different anthelmintics against field strains of nematode parasites of sheep in the southern Cape Province.

Controlled anthelmintic tests and faecal egg count reduction tests were carried out on natural infections of nematode parasites in sheep on 4 farms in the southern Cape Province. Albendazole, fenbendazole, ivermectin, levamisole, morantel citrate and a combination of albendazole and closantel sodium were tested. Every farm harboured anthelmintic resistant nematode parasites. Adult as well as immature Teladorsagia spp. were resistant to albendazole and fenbendazole, immature Teladorsagia spp. to albendazole/closantel, adult and immature Nematodirus spp. to albendazole/closantel and adult Nematodirus spp. to fenbendazole.

Animals↗

Anthelmintic activity of pyrazinothiadiazine dioxide derivatives.

In a search for new anthelmintic compounds, some pyrazinothiadiazine dioxide derivatives were synthesized. Their anthelmintic activity was tested against larva and preadult stages of Trichinella spiralis. The mode of action and acute toxicity of these compounds were investigated. Structure-activity relationships are discussed.

Animals↗

Infectivity of Hymenolepis diminuta for the jird, Meriones unguiculatus, and utility of this model for anthelmintic studies.

The jird (Meriones unguiculatus) has been shown to be a useful model host for the cestodes Taenia crassiceps and Echinococcus multilocularis. This report outlines a novel model in which hydrocortisone-treated jirds (0.02% in the feed) are infected with another cestode, Hymenolepis diminuta. Jirds were inoculated with 5 freshly harvested cysticercoids of H. diminuta prior to (day 0, -1, or -5) or after (day 1 or 5) switching to medicated feed; in some cases, jirds were never medicated. On days 7, 14, 21, or 28 postinoculation (PI), jirds were killed by CO2 inhalation and their small intestines were examined for tapeworms. Hymenolepis diminuta established, grew, and developed to the gravid adult state in jirds. They persisted longer in medicated (21 days) than in nonmedicated (7 days) animals, and generally higher levels of infection were obtained when jirds were inoculated immediately prior to switching to medicated feed. Treatment of infected jirds on day 4 or days 4, 5, and 6 PI with selected anthelmintics followed by necropsy on day 7 PI discriminated drugs with known activity against tapeworms from those with little or no activity. This rodent in vivo model should provide a useful adjunct for anthelmintic studies.

Animals↗

Anthelmintic activity of 6,7-diaryl-pteridines.

In a search for new anthelmintic compounds, some 6,7-diaryl-pteridines were synthesized from the corresponding diaminopyrimidines and aromatic aldehydes. Their anthelmintic activity was tested in vitro against Caenorhabditis elegans and Heligmosomoides polygyrus and in vivo against Trichinella spiralis. Structure-activity relationships are discussed.

Animals↗