Efficacy of injectable and oral paste formulations of ivermectin against gastrointestinal parasites in ponies

A controlled test was used in ponies to compare the antiparasitic efficacy of ivermectin (22,23-dihydro-avermectin B1) in an injectable micelle solution administered IM with the efficacy of the same drug in an oral paste formulation. Parasite infections were naturally acquired in southern Louisiana. The drug was tested in both formulations at a dosage level of 0.2 mg/kg of body weight. Ivermectin in both formulations tested had an efficacy greater than 98% against Gasterophilus intestinalis and G nasalis larvae. Trichostrongylus axei, Habronema spp, Strongylus vulgaris, S. edentatus, and species of small strongyles present. Efficacy of ivermectin against Oxyuris equi larvae was 100% in the paste formulation and 93% in the injectable formulation. The ponies were less uniformly infected with S equinus, Draschia megastoma, Parascaris equorum, O equi adults, Anoplocephala perfoliata, and A magna. However, observations indicated that the drug in either formulation was also effective against these parasites, except Anoplocephala spp.

Studies on chemotherapy of parasitic helminths (VI) effects of various neuropharmacological agents on the motility of Dipylidium caninum

Effects of various neuropharmacological agents on the motility of Dipylidium caninum was studied. 5-HT stimulated the motility of D. caninum, while other drugs such as GABA, adrenaline, phenylephrine, isoproterenol, dibenamine, and propranolol showed little effect. The stimulatory action of 5-HT was antagonized by tryptophol. Stibnal caused paralysis which was blocked by the pretreatment with 5-HT. Paralytic effects were caused by eserine, dichlorovos, ACh, carbachol and DMPP, but not by pilocarpine and McN-A-343. d-Tubocurarine, hexamethonium, and atropine all showed little effect on the motility and on the paralytic action of eserine. Though guanidine showed little effect, strychnine remarkably stimulated the motility. The action of strychnine was stimulated by 5-HT but partially inhibited by tryptophol. Morphine and picrate slightly stimulated the motility, but showed little influence on the paralytic action of eserine. These two agents stimulated the paralyzed preparation by tryptophol transiently and sustainedly, respectively. These results on the cholinergic and serotonergic drugs basically showed good agreement with those reported in trematodes such as Schistosoma mansoni and Fasciola hepatica.

[Studies on chemotherapy of parasitic helminths (IV). Effects of alkaloids from Sophora flavescens on the motility of parasitic helminths and isolated host tissues (author's transl)]

Effects of N-methylcytisine (N-MC) and matrine (Mat), alkaloids from Sophora flavescens on the motility of parasitic helminths and isolated frog rectus and mouse ileum were studied. 1) The motility of Angiostrongylus cantonensis was affected spastically by N-MC (1.2 X 10(-6) approximately 1.2 X 10(-4) M), but paralytically by Mat (10(-5) approximately 10(-4) M). 2) The motility of Dipylidium caninum and Fasciola hepatica was affected paralytically by N-MC (1.2 X 10(-4) approximately 1.2 X 10(-3) M), but spastically by Mat (10(-4) approximately 10(-3) M). 3) Treatment with N-MC (10(-3) M) and Mat (8 X 10(-4) M) had little effect on the motility of Schistosoma japonicum. 4) Both N-MC (1.2 X 10(-5) approximately 2.4 X 10(-5) M) and Mat (10(-4) M) stimulated the twitch response induced by guanidine (2.5 X 10(-5) M) in the frog isolated rectus preparation. 5) The motility of the mouse isolated ileum preparation was affected paralytically by N-MC (1.2 X 10(-5) approximately 1.2 X 10(-4) M), but spastically by Mat (10(-4) approximately 10(-3) M). Thus, N-MC and Mat acted antagonistically on all the preparations with the exception of the frog rectus preparation. From the results on interactions between these alkaloids and known neuropharmacological agents, it is suggested that the effects of both alkaloids are elicited through a neuropharmacological mechanism in parasitic helminths and host tissues.

[Studies on chemotherapy of parasitic helminths (III). Effects of tuberostemonine from Stemona japonica on the motility of parasitic helminths and isolated host tissues (author's transl)]

Effects of tuberostemonine (TS), an alkaloid from Stemona japonica, on the motility of parasitic helminths and isolated frog rectus and mouse ileum were studied. 1) TS (6.7 X 10(-6) approximately 2 X 10(-5) M) paralyzed the motility of Angiostrongylus cantonensis. 2) TS (6.7 X 10(-5) M) showed contractive effects on the motility of Dipylidium caninum and Fasciola hepatica. 3) Treatment with TS (6.7 X 10(-5) approximately 4.8 X 10(-4) M) had little effect on the motility of Schistosoma japonicum. 4) TS (6.7 X 10(-5) M) paralyzed the motility of the mouse isolated ileum preparation. 5) TS (6.7 X 10(-7) 6.7 X 10(-6) M) stimulated the twitch response induced by guanidine (2.5 X 10(-3) M) in the frog isolated rectus preparation. 6) Eserine and TS acted antagonistically on all preparations with the the exception of S. japonicum. 7) TS and strychnine were antagonistic in isolated host tissues, whereas these compounds acted similarly on parasitic helminths. Thus, it is suggested that some of the experiential effects of the crude extracts of Stemona such as the anthelmintic effects are caused through the action of TS on parasitic helminths and host tissues.

Evaluation of granulated fenbendazole as a treatment for helminth infections in dogs

A granulated formulation of fenbendazole was tested in 95 dogs harbouring naturally occurring infections of Toxocara canis, Ancylostoma caninum, Trichuris vulpis, Dipylidium caninum, and Taenia spp and in 19 laboratory-reared Beagle pups experimentally infected with Toxascaris leonina. The drug was administered in moistened dry dog food or in canned dog food. In dosage titration and confirmational studies, using worm counts in naturally infected dogs, the drug was 98%-100% effective at a dosage of 50 mg/kg of body weight/day for 3 days against the commonly occurring nematodes of dogs (ascarids, hookworms, and whipworms) and against Taenia tapeworms. A dosage of 20 mg/kg for 5 days was equally effective against nematodes, but only 73% of the dogs were cleared of Taenia tapeworms. There was no activity at either dosage against Dipylidium tapeworms. Dosages of 100 or 150 mg/kg for a single treatment and 5 or 25 mg/kg daily for 3 days were unsatisfactory with respect to nematodes and tapeworms. Induced infections of T leonina were eliminated from all treated dogs at the dosage and dosing period tested (50 mg/kg/day for 3 days). Fourteen untreated controls expelled 13% of T leonina burdens. It was concluded that granulated fenbendazole is effective in dogs against natural infections of T canis, A caninum, T vulpis, Taenia spp, and experimentally induced infections of T leonina at a dosage of 50 mg/kg of body weight/day for 3 days.

The effects of selective immunosuppression on resistance to Mesocestoides corti in strains of mice showing high and low initial susceptibility

Previous work has shown that C57BL/6 mice had the lowest initial susceptibility to Mesocestoides corti of six strains of mice examined. Parasite burdens in this strain and in CBA/H mice, a strain showing a higher initial susceptibility to M. corti, were compared following selective immunosuppressive treatments. Irradiation, splenectomy and the administration of cyclophosphamide and methyl prednisolone all resulted in higher parasite burdens in C57BL/6 mice. In contrast these treatments had a minimal effect on parasite burdens in CBA/H mice. In the light of these results the role of antibody in controlling parasite proliferation is discussed.

The enhancement of tetrathyridial proliferation of Mesocestoides corti in mice by B.C.G

The effects of different doses of B.C.G. given at various periods before infection, on the development of tetrathyridia of Mesocestoides corti was studied. B.C.G. administration was found to exert a complex influence upon M. corti infection in mice. Either enhancement or inhibition of parasite proliferation may occur, depending upon dosage level and the time interval between B.C.G. administration and parasite challenge.

The effect of mebendazole on different developmental stages of Hymenolepis diminuta cysticercoids

Tribolium confusum beetles infected with Hymenolepis diminuta were fed continuously from day 1, 3, 5, 6, or 7 to day 10 post infection (p.i.) on a mixture composed of two parts Telmin (containing 16.67% of mebendazole) and one part flour. The drug inhibited the worm development and this effect decreased as the age of larvae at the time of the first exposure increased. Lowered incidence of infection, decreased population size, and retarded development were apparent when the beetles were given drug from day 3 p.i. or earlier. Retarded development was also observed in cysticercoids from beetles given drug from day 5 p.i. When given from day 6 or later, it had no effect on worm development. However, when compared with larvae from beetles fed only flour, cysticercoids exposed to the drug from day 6 or later showed reduced infectivity and a decrease in their ability to excyst in vitro. Fully developed infective cysticercoids exposed to the drug from day 10 p.i. or later were not affected by it.

The response of nematodes in vivo and in vitro to some anthelmintics

Dietary feeding of drugs for 5 days to mice infected with Nematospiroides dubius and Hymenolepis nana detected all modern anthelmintics examined except stilbazium. A simple test using eggs of Nematodirus spathiger and adult Nippostrongylus brasillensis to detect anthelmintics in vitro is reported.

The effect of cortisone acetate on the metabolism of Hymenolepis microstoma (cestoda:cyclophyllidea)

Hymenolepis microstoma grown in mice, treated with 1.25 mg cortisone acetate every second day, are heavier and have a significantly higher glycogen content than those in control mice. The dry/wet weight ratio and protein content however are unaffected. It is suggested that the increase in glycogen reserve and weight in H. microstoma from cortisone-treated mice is due to an immunosuppressive effect and better nutritional environment rather than hormonal action. Inclusion of 0.1 mg of cortisone per 100 ml of culture medium produces no change in worm weight in vitro. Single worm infections result in 100% recovery, but 30 worm infections provoke a rejection process which can be suppressed partially by administration of cortisone acetate.

A field trial with a new anthelmintic oxfendazole in naturally infected calves

In a field trial on a series of 10 farms involving 116 calves the activity of oxfendazole at a dose rate of 2.5 mg/kg against gastro-intestinal helminths was assessed. On the basis of egg counts and larval differentiation before and after treatment it was shown that the compound had excellent activity against the most common nematodes. Although not proven in this trial, there were indications of some activity against inhibited stages of Ostertagia. Activity against Strongyloides was lower, while for Trichuris and Moniezia the infection rates before treatment were too low to draw any definitie conclusions about the activity of oxfendazole against these parasites.

The in vitro effects of farnesol and derivatives on Hymenolepis diminuta

Employing an in vitro maintenance system, in which 8-day-old Hymenolepis diminuta survives for 24 hr (Fioravanti and MacInnis, 1976), it was found that farnesol or farnesal supplementation of the medium had no beneficial effects on maintenance and these substances induced necrosis at higher concentrations. Similar experiments utilizing Schiller's (1965) culture system demonstrated that neither farnesol, farnesal, nor farnesyl methyl ether exhibited growth promoting effects and were toxic to the worms at higher concentrations. In addition, neither the 2-cis, 6-trans nor the 2-trans, 6-trans-isomers of farnesol promoted growth in the Schiller system and at higher concentrations resulted in severe necrosis within 24 hr.

The effect of mebendazole on the development of Hymenolepis diminuta in Tribolium confusum

Tribolium confusum parasitized by Hymenolepis diminuta were allowed to feed on mixtures composed of 0.005 to 20 g of mebendazole (Telmin: methyl-5-benzoyl benzimidazole-2-carbamate) in 10 g of flour from day 1 (24 h) to day 9 post infection. Retarded cysticercoid development, lowered incidence of infection, and reductions in the number of cysticercoids recovered per beetle were produced by drug levels of 0.1, 1.0, and 10 g respectively. None of the drug concentrations tested produced 100% mortality, and developing cysticercoids varied considerably in their tolerance of mebendazole.

Azo- and nitro-reductases of the cestode Moniezia expansa. Substrate specificity, reaction products and the effects of flavins and other compounds

1. The effects of various inhibitors and activators on the azo- and nitro-reductases of Moniezia expansa have been studied. Both reductions were partially inhibited by FAD, FMN, riboflavin, allopurinol, dicoumarol, 5-nitro-2-furaldehyde, azide and cyanide at 1 mM. Both reactions were stimulated by hypoxanthine. Menadione, nitrofurantoin, SKF 525-A (2-diethylaminoethyl 2,2-diphenylvalerate) and fluoride were without effect. 2. Xanthine- and aldehyde-oxidase activities were not detected in the enzyme preparation. 3. The substrate specificity of the azo- and nitro-reductases were determined. Azobenzene, 4-dimethylamino-azobenzene and 1,2-dimethyl-4-(4-carboxyphenylazo)-5-hydroxybenzene, nitrobenzene, 4-nitrohippuric acid and the isomers of nitrophenol, nitroanisole, nitrobenzoic acid, nitrobenzaldehyde and nitrobenzyl alcohol were reduced. Nitrobenzaldehyde isomers were not reduced to the alcohols and the coumaric acids were not reduced to the phenylpropionic acids. 4. The products of azo- and nitro-reduction were the corresponding amines; hydroxylamino- and hydrazo-compounds were not detected. 5. The pH optima and cofactor requirements were the same for both azo- and nitro-reduction. Neither reaction was inhibited by oxygen.

Studies on Hymenolepis microstoma in vitro. I. Effect of heme compounds on growth and reproduction

The effect of various heme compounds on growth and maturation of Hymenolepis microstoma in vitro has been determined. At 4 days p.i., worms were collected and cultured in vitro for 6 days in a medium containing various concentrations of haemoglobin, hemin, and bilirubin. Addition of haemoglobin to a medium resulted in significant increases in length, wet weight, number of immature and mature proglottids as compared to the control medium. Supplements of hemin did not seem to affect worm length; however, they caused a significant weight increase, and the numbers of immature and mature proglottids were also more than those in control medium. Bilirubin supplements failed to show any effect on growth and maturation of H. microstoma, and the experimental and control worms were found similar in all respects. In the light of the success with haemoglobin and hemin as growth promoting substances, the role of blood ingredients was also considered. For strobilization and maturation of H. microstoma in vitro, the presence of some kind of heme protein seems essential.

[Study of the cumulation, desorption and mechanism of action of organochlorine pesticides on fish cestodes]

The distribution of residues of DDT and its metabolites (DDD and DDE) in tissues of Triaenophorus nodulosus and its host was studied. It has been noted that cestodes can accumulate chlororganic substances in great quantity. The ability of Bothriocephalus gowkongensis has been established to dechlorate pp-DDT and to excrete pp-, op- and mp-DDD from the organism. Pp-DDT decreases the glycogene content and causes the rise of amylolytic activity in the above cestodes in acute tests. The effect of pp-DDT on the locomotor activity of cestodes is of two-phase character. The first one is associated with the muscular influence, the second one-- with neurotrophic effect. A high toxicity of mp-DDD )0.1 mg/l) for the locomotor activity of cestodes as compared with the effect of pp- and op-DDD was revealed.