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PubMed2003

World Association for the Advancement of Veterinary Parasitology (WAAVP) guidelines for evaluating the effectiveness of anthelmintics in chickens and turkeys.

These guidelines have been prepared to assist in the planning, operation and interpretation of studies designed to assess the effectiveness of drugs against helminth parasites of chickens and turkeys. They are the first to be compiled under the auspices of the World Association for the Advancement of Veterinary Parasitology (WAAVP) for these parasites. The advantages and disadvantages of the widely used critical and controlled tests are discussed. Information is provided on the selection of animals for experiments, animal housing, feed, dose determination studies, confirmatory and field trials, record keeping and necropsy procedures. This document should help investigators and those involved in product approval and registration in conducting and evaluating studies concerned with determining the effectiveness and safety of anthelmintic drugs.

Animal Husbandry↗
PubMed1997

Faecal egg count reduction percentage calculations to detect anthelmintic resistance in Oesophagostomum spp. in pigs.

The results of four alternative methods of mean faecal egg count reduction percentage (FECR%) calculations were evaluated and compared using data obtained for Oesophagostomum spp. from ten sow herds. The estimates of FECR% and 95% confidence limits obtained using the four methods were different. However, there were few discrepancies in the final decision as to whether a given herd carried drug resistant isolates or not. The methods that used geometric means were more appropriate than those that used the arithmetic mean as the measure of central tendency for eggs per gram of faeces (EPG) values. The use of geometric mean EPG values in calculations has been criticized from several viewpoints, one of which is that its use reduces the comparability of reports between laboratories. If the geometric mean is to be used as we suggest in FECR% calculations, the appropriate references, number of animals in each group, minimum and maximum EPG values and the factor added to zero EPG counts should be reported in order to improve the comparability. The difficulty in obtaining groups with similar pre-treatment EPG values in field situations suggested the inclusion of pre-treatment EPG values in the calculations as an adjustment procedure. The importance of including a non-treated control group in calculations was demonstrated during this study. Therefore, we suggest the use of geometric mean EPG values, to include pre-treatment EPG values and to include the egg counts from the control group in FECR% calculations. The interpretation of the resulting FECR estimate may be different according to the purpose for which the testing procedure is carried out, e.g. survey in detecting anthelmintic resistance, control field tests, etc.

Animals↗
PubMed1997

Anthelmintic resistance of trichostrongylids in sheep in the highveld of Zimbabwe.

A survey was conducted on the occurrence of anthelmintic resistance of trichostrongylids on commercial sheep farms in the highveld of Zimbabwe. On ten farms the efficacy of fenbendazole, levamisole and rafoxanide was tested by a faecal egg count reduction test. Benzimidazole resistance was additionally examined using an egg hatch assay with thiabendazole. Results of the faecal egg count reduction tests and larval differentiations showed fenbendazole resistance of Haemonchus sp. on all investigated farms. Resistance of Haemonchus sp. against rafoxanide was demonstrated on all farms with reliable egg counts. Levamisole resistance of Haemonchus sp. was found on most farms but 2 farms showed an efficacy of 100%.

Animals↗
PubMed1997

Ecotoxicology and residues of anthelmintic compounds.

Anthelmintics and endectocides used for the treatment and prophylaxis of Ostertagia sp. in ruminants include benzimidazoles, levamisole, morantel and the avermectins and milbemycins. Most of these agents are excreted to some extent in the faeces of treated animals and it has been demonstrated that members of the avermectin/milbemycin group may have deleterious effects on non-target organisms utilising the faeces. The environmental impact of antiparasitic chemotherapy depends on the deleterious effect which the agent or its metabolites have on organisms in the locus of the excreta, the amount of active agent excreted, the temporal nature of the excretion and the stability of the ecotoxic residues. These have to be considered in the context of the overall proportion of excreted faeces from a herd which is contaminated and thus the availability of non-contaminated faeces which may act as refugia for dung utilising organisms. The contribution which weathering, faunal inhabitants, trampling by cattle and disturbance by birds have on the rate of dung degradation must also be considered. The greatest ecotoxicological risk is associated with sustained release delivery devices, delivering endectocides with potent activity against dipteran flies and coleopteran beetles. The relatively large proportion of most cattle herds excreting faeces with no endectocidal contamination is likely to reduce the impact that such treatment or prophylactic strategies have on non-target organisms.

Animals↗
PubMed1998

A questionnaire survey on nematode control practices on horse farms in Denmark and the existence of risk factors for the development of anthelmintic resistance.

A questionnaire survey to obtain information on endoparasite control practices and management on 68 Danish horse farms was undertaken in 1995. The study revealed that foals, young horses and adults were on average, annually treated 4.3, 4.0 and 3.7 times, respectively. The most commonly used drug from 1993-1995 was ivermectin. On average 2.4 different drugs were used annually. The most used method of weight estimation was eye measure: for foals by 78%, for youngsters by 81% and adults by 82% of the herd owners. The most commonly used weight in the dosing of anthelmintics was individual weights of the horse: 72% of the herd owners dosed their foals this way. 76% their youngsters and 75% their adults. Sixty two percent of the herd owners treated at turn out, 47% at housing, 57% treated when buying new horses, 26% treated when stabling visiting horses, 78% applied pasture change and 18% performed alternate/mixed grazing. Sixty one percent of the herds had experienced problems with diarrhoea and in 18% of the cases the suspected cause was considered to be endoparasites. 33% of the farms performed disease registration and on 25% Faecal Egg Count Reduction tests had been performed before entering this study. The herd owners obtained their formation about endoparasite control from veterinarians, meetings and papers in that order of importance.

Animal Husbandry↗
PubMed1999

Anthelmintic resistance in sheep and goat farms on Peninsular Malaysia.

The faecal egg count reduction test (FECRT) was conducted on 39 sheep farms and 9 goat farms located in Peninsular Malaysia. The anthelmintic groups used in these tests were the benzimidazoles, levamisole, the benzimidazole/levamisole combination, macrocyclic lactones and closantel. Results indicated that the prevalence of resistance to the benzimidazole group was high, with approximately 50% of the sheep farms and 75% of the goat farms having resistant nematode parasite populations present. Resistance to levamisole, closantel and ivermectin was also detected. Differentiation of the infective larvae derived from faecal cultures indicated that by far the most predominant parasite species was Haemonchus contortus.

Animal Husbandry↗
PubMed1999

A comparison of in vitro tests and a faecal egg count reduction test in detecting anthelmintic resistance in horse strongyles.

This study reports a comparison between faecal egg count reduction test (FECRT), egg hatch assay (EHA) and larval development assay (LDA) for detecting anthelmintic resistance in equine strongyles. Resistance to benzimidazoles was demonstrated in 33 of 42 (79%) farms tested by FECRT and in 32 (62%) of the 52 farms tested by EHA. As the reference strain used was not fully susceptible to benzimidazoles it was not possible to determine the level of resistance by LDA. Pyrantel resistance was indicated on three of 15 farms by faecal egg count reduction. Resistance was also indicated by LDA for one of these farms. In addition resistance was indicated by LDA on two more farms that were not tested by FECRT. Further testing is needed to confirm if these findings are truly indicative of resistance. Generally, correlations between the tests were poor and it was not possible to use the outcome of one test to predict the outcome of another.

Animals↗
PubMed2000

Multiple anthelmintic resistance in a goat herd.

Anthelmintic resistance was monitored over a 30 month period within a goat herd in eastern Virginia, USA. Resistance to ivermectin, levamisole and benzimidazole drugs was detected in Haemonchus contortus using the fecal egg count reduction test (FECRT). When levamisole use was discontinued for 1 year, susceptibility to levamisole appeared to return. Although a single treatment with fenbendazole was able to reduce fecal egg counts by only 50%, two doses administered in a 12 h interval increased efficacy to 92%, however, confidence intervals indicated that resistance was still present. When fecal egg counts were determined the following year after several treatment using this protocol, the efficacy of fenbendazole had fallen again to 57% reduction in fecal egg counts. The predominant genus present in cultured composite fecal samples was Haemonchus. Trichostrongylus, Cooperia and Teladorsagia were also present in smaller numbers.

Administration, Oral↗
PubMed2000

Anthelmintic actions on homomer-forming nicotinic acetylcholine receptor subunits: chicken alpha7 and ACR-16 from the nematode Caenorhabditis elegans.

Two homomer-forming nicotinic acetylcholine receptor subunits with 47% identity in their amino acid sequences were employed to compare the actions of cholinergic anthelmintics and ivermectin on expressed vertebrate and nematode nicotinic receptors of known molecular composition. Voltage-clamp electrophysiology was used to study recombinant nicotinic receptors expressed in Xenopus laevis oocytes following nuclear injection of cDNA encoding either chicken alpha7 or Caenorhabditis elegans ACR-16 (Ce21) subunits. Butamisole, morantel and metyridine were without agonist actions on either alpha7 or ACR-16 nicotinic receptors in the range 10nM-1mM. However, butamisole (pIC(50)=4.9 for both alpha7 and ACR-16) and morantel (pIC(50)=5.6 for alpha7 and 5.7 for ACR-16) antagonized responses of both alpha7 and ACR-16 receptors to acetylcholine. Metyridine (1mM) did not affect responses to acetylcholine of either receptor. Oxantel was without agonist actions on ACR-16, but was an acetylcholine antagonist (pIC(50)=5.4). In contrast, it was found to have low efficacy agonist action (pEC(50)=4.4) on alpha7 at concentrations in the range 10-300microM. In agreement with a previous study, ivermectin (30microM), an agonist of L-glutamate-gated chloride channels, enhanced the amplitude of responses to acetylcholine of alpha7 nicotinic receptors. However, this same concentration of ivermectin (30microM) did not potentiate the acetylcholine-induced responses of ACR-16, but rather resulted in a slight attenuation. We conclude that oxantel and ivermectin have identified new pharmacological differences between the chicken alpha7 nicotinic receptor and its C. elegans homologue ACR-16.

Acetylcholine↗
PubMed2001

Anthelmintic activity of crude aqueous extract of Nauclea latifolia stem bark against ovine nematodes.

The anthelmintic efficacy of Nauclea latifolia stem bark aqueous extract was studied in sheep with natural acute/sub-acute parasitic gastro-enteritis due primarily to mixed nematode species. Graded doses of the extract (400, 800 and 1600 mg/kg, p.o for 5 consecutive days) significantly reduced faecal egg counts in infected animals. The percentage reduction (93.8%) by 1600 mg/kg of the extract was comparable to that of 5 mg/kg of albendazole (94.1%). The administration of the extract resulted in improved haemoglobin and leucocytosis values in worm-infected sheep.

Animals↗
PubMed2002

Anthelmintic activity of preparations derived from Myrsine africana and Rapanea melanophloeos against the nematode parasite, Haemonchus contortus, of sheep.

Myrsine africana L. and Rapanea melanophloeos L. belong to the plant family Myrsinaceae. Various rural communities in Kenya, such as smallholder farmers and pastoralists, use them to treat their livestock. The anthelmintic effects/activities of leaves and fruits of M. africana and fruits of R. melanophloeos were tested in sheep experimentally infected with the nematode parasite Haemonchus contortus. Male lambs were infected with 3000-5000 third stage larvae of H. contortus and treated 28 days after inoculation with concoctions made from leaves or fruits of the plants. No significant reduction in faecal nematode egg counts was observed with any of the concoctions at any of the doses tested. Packed red cell volume decreased and live weight increased at similar rates in treated and control groups, thus there was no significant effect of treatment. The results showed that the tested extracts of the M. africana and R. melanophloeos were not efficacious against H. contortus in sheep.

Animals↗
PubMed2003

Synthesis and anthelmintic activity of cyclohexadepsipeptides with (S,S,S,R,S,R)-configuration.

The (S,S,S,R,S,R)-configurated cyclohexadepsipeptides (CHDPs) represent novel enniatin derivatives with strong in vivo activity against the parasitic nematode Haemonchus contortus Rudolphi in sheep. 2D NMR spectroscopic analysis revealed for the major conformation the asymmetric conformer, containing a cis-amide bond between C(alpha) protons of neighbouring 2-hydroxy-(S)-carboxylic acid and N-methyl-(S)-amino acid. The absolute configuration of the novel CHDPs was determined by X-ray crystallography. A correlation between the major conformer and its anthelmintic activity was found. Here, we report on a simple total synthetic pathway for this particular type of CHDPs.

Animals↗
PubMed1998

Anthelmintic beta-hydroxyketoamides (BKAs).

We have prepared several anthelmintic coumarins based on the beta-hydroxyketoamide (BKA) template and have shown that this template remains valid over a wide range of changes to the coumarin moiety allowing for the inclusion of carbocyclic, bicyclic, and heterocyclic rings.

Animals↗
PubMed2002

Marine pharmacology in 1999: compounds with antibacterial, anticoagulant, antifungal, anthelmintic, anti-inflammatory, antiplatelet, antiprotozoal and antiviral activities affecting the cardiovascular, endocrine, immune and nervous systems, and other miscellaneous mechanisms of action.

This review, a sequel to the 1998 review, classifies 63 peer-reviewed articles on the basis of the reported preclinical pharmacological properties of marine chemicals derived from a diverse group of marine animals, algae, fungi and bacteria. In all, 21 marine chemicals demonstrated anthelmintic, antibacterial, anticoagulant, antifungal, antimalarial, antiplatelet, antituberculosis or antiviral activities. An additional 23 compounds had significant effects on the cardiovascular, sympathomimetic or the nervous system, as well as possessed anti-inflammatory, immunosuppressant or fibrinolytic effects. Finally, 22 marine compounds were reported to act on a variety of molecular targets, and thus could potentially contribute to several pharmacological classes. Thus, during 1999 pharmacological research with marine chemicals continued to contribute potentially novel chemical leads in the ongoing global search for therapeutic agents for the treatment of multiple disease categories.

Animals↗
PubMed1985

Anthelmintic effects of bithionol, paromomycin sulphate, flubendazole and mebendazole on mature and immature Hymenolepis nana in mice.

The anthelmintic effects of anti-tapeworm drugs, bithionol, paromomycin sulphate, flubendazole and mebendazole on immature and mature Hymenolepis nana in mice were compared. Immature worms were not affected by paromomycin sulphate or flubendazole administered for 12 consecutive days (days one to 12 after infection) at 100 mg/kg/day but 48% and 100% of H. nana were eliminated from mice by bithionol and mebendazole respectively, at the same dosage regimen. Bithionol, paromomycin sulphate, flubendazole and mebendazole given at 100 mg/kg/day for five consecutive days (days 12 to 16 after infection) eliminated 32%, 29%, 36% and 100% of mature worms respectively. 10 and 20 mg of mebendazole/kg/day for five consecutive days (days 12 to 16 after infection) had little effect on mature worms whereas 50 and 100 mg/kg/day for the same period eliminated 99% and 100% of mature worms, respectively. ED50 of mebendazole in the elimination of mature H. nana was 14 or 15 mg/kg/day for five days from the reduction in dry weight or in number of worms recovered respectively. The effects of mebendazole given 2 to 4 days, 8 to 10 days or 13 to 15 days after infection at 100 mg/kg/day were compared. Very low, if any, activity of the drug given 2 to 4 days after infection was seen, whereas the drug given 8 to 10 days or 13 to 15 days after infection eliminated 84% and 86% of H. nana respectively.

Animals↗