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Substituted imidazo[2,3-alpha]pyridine-2-carbamate anthelmintics.

Anthelmintic efficacies of a series of 6-substituted methyl imidazo[1,2-alpha]pyridine-2-carbamates were compared to similarly substituted benzimidazole-2-carbamates. With only one exception, methyl 6-benzoylimidazo[1,2-alpha]pyridine-2-carbamate, both classes of compounds exhibited similar activity vs. Nematospiroides dubius in mice. Preliminary screening indicated methyl 6-(1,2,2-trichloroethenyl)imidazo[1,2-alpha]pyridine-2-carbamate to be the most potent derivative in the series. However, evaluation in sheep indicated that its anthelmintic spectrum was inferior to methyl 6-(phenylsulfinyl)imidazo[1,2-alpha]pyridine-2-carbamate.

Animals↗

Methyl 6-(phenylsulfinyl)imidazo[1,2-a]pyridine-2-carbamate, a potent, new anthelmintic.

A series of methyl imidazo-[11,2-a]pyridine-2-carbamates was synthesized for anthelmintic testing. The preparation of this class of compounds was simplified by utilization of a novel one-step condensation of the appropriately substituted 2-aminopyridine and methyl chloroacetylcarbamate. The most potent compound, methyl 6-(phenylsulfinyl)-imidazo[1,2-a]pyridine-2-carbamate, was orally effective against a broad range of helminths in sheep and cattle, at a dosage of 2.5 mg/kg. Limited trials in swine and dogs demonstrated anthelmintic activity at higher dosages. Limited observations in sheep and cattle indicated that, in both species, a single oral dose of 200 mg/kg was well tolerated.

Animals↗

Synthesis of 1- and 2-substituted indazoles as anthelmintic agents.

Selective synthesis of 1- and 2-acyl-, alkoxycarbonyl-, and carbamoylindazoles are described. Spectroscopic data which were the basis for structural assignments are presented. These compounds, particularly methyl 2H-indazole-2-carboxylate and N-heptyl-N-methyl-2H-indazole-2-carboxamide, lack the spectrum of anthelmintic activity of the benzimidazole and benzotriazole anthelmintics to which they are structurally related.

Animals↗

Novel phosphate anthelmintics. 3. Alkyl and aryl 1-methyleneallyl phosphates, phosphonates, and phosphinates.

A series of new highly chlorinated 1-methyleneallyl ("butadienyl") dialkyl phosphates and related phosphonates and phosphinates has been synthesized and assessed for anthelmintic activity in mice against the tapeworm Hymenolepis nana and the pinworm Syphacia obvelata. Highest activity was observed with diethyl 2,3,3-trichloro-1-dichloromethyleneallyl ("perchlorobutadienyl") phosphate (14), while replacement of both ethoxy groups by methoxy and larger alkoxy or phenyl groups gave less efficacious compounds. In general, chlorine depletion of the 1,3-butadien-2-yl moiety or saturation of one double bond reduced anthelmintic responses.

Animals↗

Total anthelmintic failure to control nematode parasites of small ruminants on government breeding farms in Sabah, East Malaysia.

Government-owned small-ruminant breeding farms in Malaysia provide the source of sheep and goats to smallholder farmers in the country. In the eastern Malaysian state of Sabah, high-level stock losses have been recorded on these farms for several years, frequently accompanied by clinical signs indicating pathogenic levels of infections with the nematode parasite Haemonchus contortus. This suggests that their dependence on chemotherapy to control parasite infections had failed. Accordingly, tests for anthelmintic efficacy using the faecal egg count reduction test (FECRT) on the range of drugs used to control nematode parasites were carried out on the five government small-ruminant breeding farms in Sabah. These tests showed a total failure of the benzimidazole, imidothiazole, macrocyclic lactone and salicylanilide groups of anthelmintics to control H. contortus infections of sheep and goats on all farms. Drastic changes in animal management need to be made in an attempt to deal with this situation, for which suggestions are made.

Animal Husbandry↗

[Equine strongyles. I. Development of anthelmintic resistance].

Small strongyles (cyathostomes) that are resistant against anthelmintics have become a major problem in equine medicine in the recent years. In many European countries benzimidazole-resistant cyathostomes are widespread and are now present in well over 50% of equine populations investigated. In contrast, resistance against ivermectin has not been reported despite its widespread use in the recent years. Optimising the frequency of treatments based on quantitative faecal monitoring is of great importance to preserve remaining anthelmintic efficacy.

Animals↗

Para-position derivatives of fungal anthelmintic cyclodepsipeptides engineered with Streptomyces venezuelae antibiotic biosynthetic genes.

PF1022A, a cyclooctadepsipeptide possessing strong anthelmintic properties and produced by the filamentous fungus Rosellinia sp. PF1022, consists of four alternating residues of N-methyl-L-leucine and four residues of D-lactate or D-phenyllactate. PF1022A derivatives obtained through modification of their benzene ring at the para-position with nitro or amino groups act as valuable starting materials for the synthesis of compounds with improved anthelmintic activities. Here we describe the production of such derivatives by fermentation through metabolic engineering of the PF1022A biosynthetic pathway in Rosellinia sp. PF1022. Three genes cloned from Streptomyces venezuelae, and required for the biosynthesis of p-aminophenylpyruvate from chorismate in the chloramphenicol biosynthetic pathway, were expressed in a chorismate mutase-deficient strain derived from Rosellinia sp. PF1022. Liquid chromatography-mass spectrometry and NMR analyses confirmed that this approach facilitated the production of PF1022A derivatives specifically modified at the para-position. This fermentation method is environmentally safe and can be used for the industrial scale production of PF1022A derivatives.

Animals↗

Anthelmintic resistance in human helminths: a review.

We briefly review reports on drug resistance in human helminths and compare the factors which contribute to the development of anthelmintic resistance in livestock and man, i.e. high treatment frequency, single-drug regimens, targeting and timing of mass treatments and underdosing. Conclusions are drawn from the mistakes in the treatment and control of livestock helminths. The advantages and inconveniences of current methods for the detection of drug resistance in helminths of livestock are discussed and some suggestions are put forward to standardize the tests for the detection of resistance in human helminths. Finally, based on veterinary experience, some recommendations are made to reduce the risks of development of drug resistance in human helminths. The dramatic and rapid spread of resistance to all major classes of veterinary anthelmintics should be a warning against too strong a reliance on drugs in helminth control programmes.

Animals↗

Community perception of school-based delivery of anthelmintics in Ghana and Tanzania.

This paper presents the results of an evaluation of community perception of two large-scale, government-run, school-based health programmes delivering anthelmintic drugs to primary school children, in Ghana (80 442 children in 577 schools) and Tanzania (110 000 children in 352 schools). Most teachers (96% in Ghana and 98% in Tanzania) were positive about their role in the programme, including administration of anthelmintic drugs, and parents and children fully accepted their taking on this role. The benefits of the programme were apparent to teachers, parents and children in terms of improved health and well-being of the children. Over 90% of parents in both Ghana and Tanzania indicated a willingness to pay for the continuation of drug treatment. The evaluation also highlighted areas that are critical to programme effectiveness, such as communication between schools and parents, the issue of collaboration between the health and education sectors, parents' perception of the importance of helminth infection as a serious and chronic health problem (compared with more acute and life threatening illnesses such as malaria), and who should pay for treatment of side-effects.

Adult↗

Improving bioavailability and anthelmintic activity of albendazole by preparing albendazole-cyclodextrin complexes.

The bioavailability and anthelmintic activity of albendazole-cyclodextrin complexes (ABZ-CDC) compared to albendazole suspensions in carboxymethylcellulose (ABZ-CMC) was assessed in a mouse model for Trichinella infections. Swiss CD-1 mice experimentally infected with T. spiralis were treated with both formulations against enteral (adult worms) and parenteral (migrating and encysted larvae). Oral bioavailability was assessed in age matched mice treated with 50 mg/kg of both formulations. The anthelmintic effects and plasma concentration of the active metabolite albendazole-sulphoxide (ABZSO) enantiomer (-) were significantly increased following administration of ABZ-CDC in relation to ABZ-CMC.

2-Hydroxypropyl-beta-cyclodextrin↗

Poor efficacy of the most commonly used anthelmintics in sport horse nematodes in Morocco in relation to resistance.

Sport and leisure horses in Morocco are treated with several anthelmintics, organophosphates (dichlorvos), benzimidazoles (mostly thiabendazole) or tetrahydropyrimidines (mostly pyrantel pamoate) against nematodes. We studied three horse stables in Rabat, one in Meknes and one in Bouznika. Two of the Rabat and Bouznika stables had introduced a large number of horses from countries (Argentina or Europe) where resistance to benzimidazoles is frequent, whereas the Meknes stud farm remained without foreign introduction. The number of treatments was not very frequent (twice a year in adult horses) but the same anthelmintics were used repeatedly. No resistance to dichlorvos was detected whereas benzimidazole and pyrantel pamoate resistances were detected for the first time in African horses, outside South Africa.

Animals↗

Genotoxical, teratological and biochemical effects of anthelmintic drug oxfendazole Maximum Residue Limit (MRL) in male and female mice.

Oxfendazole, methyl-5 (6)-phenylsulfinyl-2-benzimidazole carbamate, is a member of the benzimidazole family of anthelmintics. Anthelmintic benzimidazoles are widely used in meat producing animals (cattle, sheep and pigs) for control of endoparasites. The extensive use of veterinary drugs in food-producing animals can cause the presence of small quantities of the drug residues in food. Maximum residue limit or "MRL" means the maximum concentration of residue resulting from the use of a veterinary medicinal product which may be legally permitted recognized as acceptable in food. The FAO/WHO Expert Committee on Food Additives (1999) evaluations of toxicological and residue data, reported that oxfendazole (MRL) has toxicological hazards on human health. The toxicity of oxfendazole (MRL) was tested in male and female mice and their fetuses. Chromosomal aberrations, teratological examination and biochemical analysis were the parameters used in this study. The results show that oxfendazole MRL induced a mutagenic effect in all tested cell types. Also, oxfendazole exhibit embryotoxicity including teratogenicity. The biochemical results show that oxfendazole induced a disturbance in the different biochemical contents of all tested tissues. So, we must increase the attention paid to the potential risk of oxfendazole residues in human beings and should stress the need for careful control to ensure adherence to the prescribed withdrawal time of this drug.

Animals↗

Use of anthelmintics in herbivores and evaluation of risks for the non target fauna of pastures.

The overall purpose ofthis paperwas to review the major and most recent literature relating the effects of anthelmintics on dung breeding invertebrates and dung degradation. Faecal residues or metabolites of drugs belonging to the benzimidazole and levamisole/morantel groups are relatively harmless to dung fauna, on the contrary to other anthelmintics such as coumaphos, dichlorvos, phenothiazine, piperazine, synthetic pyrethroids, and most macrocyclic lactones which have been shown to be highly toxic for dung beetles (abamectin, ivermectin, eprinomectin, doramectin), among which moxidectin was the less toxic for dung beetles. To date, the detrimental impact upon non-target organisms has been considered acceptable in eradicating the parasites because of their economic importance to commercial livestock production. The consequences of routine treatments are discussed with consideration of the long-term consequences for cow pat fauna and sustainable pastureland ecology.

Animals↗

An anthelmintic compound, nafuredin, shows selective inhibition of complex I in helminth mitochondria.

Infections with parasitic helminths are important causes of morbidity and mortality worldwide. New drugs that are parasite specific and minimally toxic to the host are needed to counter these infections effectively. Here we report the finding of a previously unidentified compound, nafuredin, from Aspergillus niger. Nafuredin inhibits NADH-fumarate reductase (complexes I + II) activity, a unique anaerobic electron transport system in helminth mitochondria, at nM order. It competes for the quinone-binding site in complex I and shows high selective toxicity to the helminth enzyme. Moreover, nafuredin exerts anthelmintic activity against Haemonchus contortus in in vivo trials with sheep. Thus, our study indicates that mitochondrial complex I is a promising target for chemotherapy, and nafuredin is a potential lead compound as an anthelmintic isolated from microorganisms.

Administration, Oral↗

In vivo anthelmintic activity of Dorycnium rectum and grape seed extract against Ostertagia (Teladorsagia) circumcincta and Trichostrongylus colubriformis in sheep.

AIM: To assess the in vivo anthelmintic activity of condensed tannins (CT) in the forage species Dorycnium rectum and Medicago sativa, and in an extract from grape (Vitus vinifera) seeds (GSE), against two species of parasite, Teladorsagia (Ostertagia) circumcincta and Trichostrongylus colubriformis, at different stages of their life cycle, in sheep that were parasite-naïve or previously exposed to nematodes. METHODS: In Trial 1, a factorial treatment structure was used to compare faecal nematode egg counts (FEC) and worm burdens in 40 weaned Romney lambs fed either the CT-containing forage D. rectum (12% dry matter; DM) or M. sativa (lucerne; 0.2% DM). Twenty naïve and 20 previously-exposed lambs were drenched free of parasites then reinfected with known species and numbers of parasites, and housed in pens indoors on a diet of lucerne pellets and chaffed hay. Groups of lambs (n=5 lambs per group) were fed one of the forages over one of two time periods within the parasite's life cycle. Six to nine days after the last feeding of fresh forages, faecal samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. In Trial 2, 12 Suffolk x Romney lambs were surgically implanted with an abomasal cannula and then housed indoors in metabolism crates. After infection with parasites, six lambs were infused continuously over a 14-day period with a commercially available CT GSE (96% DM, made up to 34 g/L in water); the remaining lambs were infused with water. During infusion, samples were collected for egg hatch and larval development assays. After infusion, samples were collected for FEC, and all lambs were slaughtered and worm counts conducted. RESULTS: In Trial 1, there was a significant (p<0.001) difference in burdens of O. circumcincta between naïve lambs and those previously exposed to parasites, but no other differences were recorded. In Trial 2, lambs infused with GSE had significantly (p<0.05) fewer T. colubriformis at slaughter and significantly (p<0.001) fewer eggs hatched in the egg hatch assay (EHA) than for lambs infused with water. Overall, the differences attributable to GSE were small in magnitude, being an 11% drop in egg hatch, and an 18% drop in numbers of adult T. colubriformis after 14 days of continuous infusion. No other differences were recorded. CONCLUSION: The results indicate that the in vivo anthelmintic activity of these CT sources is, at best, modest and is unlikely to be of any practical value. Further, these data emphasise that in vitro activity is an unreliable indicator of in vivo efficacy for CT-containing forages and extracts.

Animals↗

Helminthic infection and anthropometric indicators in children from a tropical slum: Ascaris reinfection after anthelmintic treatment.

We evaluated helminthic infection and anthropometric indicators of nutritional status in a group of school-age children from a slum area of Caracas, Venezuela. The proportions of children at or below the 10th percentiles for height/age and weight/age were significantly higher in those presenting helminthiasis than in those uninfected. Although this could partially reflect a codependence of both helminthic infection and undernutrition or poverty, when the children were administered regular anthelmintic treatment for a year their anthropometric values improved significantly. When they were re-evaluated 8 months after the end of anthelmintic administration, the degree of reinfection by the most common helminth, Ascaris lumbricoides, was significantly higher in the growth-retarded children. These results confirm the relationship between helminthic infection and decreased growth rates in underprivileged populations, and indicate that children at nutritional risk are more susceptible to such infections, even after a prolonged parasite-free period.

Anthelmintics↗

Evaluation of anthelmintics, antiprotozoal drugs and ectoparasiticides for racing pigeons (Columba livia var. domestica) available in The Netherlands.

Anthelmintics, antiprotozoal drugs and ectoparasiticides specially marketed for use in racing pigeons (Columba livia var. domestica) were evaluated by comparing dosages and indications given by the producers with data obtained from efficacy studies or empirical data. Of a total of 63 products, 59% were in accordance with the literature. Fifty-nine percent of the dosages and indications of anthelmintics were in accordance with scientifically obtained data, while for trichomonacides, coccidiostats and ectoparasiticides the figures were 47%, 59% and 100% respectively. Public health aspects of the consumption of medicated pigeons are discussed.

Animals↗