[2-(Guanidino)-anilides and related compounds. Synthesis and anthelmintic effect. 3. Anthelmintics]

Anilides bearing a guanidino, thioallophanato, isothioallophanato or amidino group in the ortho position were synthesised (6) for investigations of their anthelmintic effects, and tested against sheep trichostrongylides. The most active anilides are those containing a 5-alkylthio, 5-alkylsulphinyl (alkyl = C3H7, C4H9), 5-phenylthio, 5-phenylsulphinyl or 4-phenylsulphonyloxy group, and a guanidino group substituted at both nitrogen atoms by a methoxycarbonyl group. The most active anthelmintic anilides are the form-, propion-, butyr- and methoxy-acetanilides (e.g. 60, 61, 66, 95, 100, 110). Of the guanidines unsubstituted at N' and N", the 2-guanidino-5-phenylthio-2-methoxyacetanilide (123) and the 2-guanidino-5-phenylsulphinyl-2-methoxyacetanilide (152) were more active than parbendazole. From the class of bismethoxycarbonylguanidines (6 alpha), which are also the most interesting products in terms of stability, febantel (110, Rintal) has been introduced into veterinary practice for the treatment of nematode infections in horses, cattle, sheep and swine.

Persistent anthelmintic effect of ivermectin in cattle

The persistent anthelmintic effect of ivermectin given subcutaneously at 200 mcg/kg was evaluated against induced infections of Haemonchus placei, Ostertagia ostertagi, Cooperia spp. (C. pectinata and C. punctata), Bunostomum phlebotomum and Oesophagostomum radiatum in cattle. Forty-four Friesian bull calves raised under worm-free conditions were restrictively randomized to one untreated control group and 3 ivermectin treated groups of equal size according to mass. Animals in the different treated groups were treated either 9, 7 or 5 d before infestation, which was induced in all animals on the same day. The results are presented as percentage reduction and Non Parametric claims. Nine days after treatment the effect of ivermectin was virtually undiminished against O. ostertagi and B. phlebotomum and 7 d after treatment against Cooperia spp. Counts of all worms were reduced by 99% or more following the treatment given 5 d before infection. According to the Non Parametric Method, "A" claims (i.e. 80% effective in 80% of the treated animals) were achieved against all 5 worms up to 7 d after treatment and against O. ostertagi and B. phlebotomum up to 9 d after treatment.

Therapeutic and prophylactic efficacy of morantel when administered directly into the rumen of cattle on a continuous basis

The efficacy of morantel tartrate when administered on a continuous basis directly into the rumen/reticulum of cattle, either by a cannula or from a specially designed device, was evaluated against gastrointestinal parasites under laboratory conditions. In two experiments the continuous infusion of morantel at rates between 0.26 and 1.04 mg/kg body weight per day using a peristaltic pump was highly efficacious in both preventing the establishment of infections and removing established infections of the following species: Ostertagia ostertagi, Haemonchus contortus, Cooperia oncophora and Trichostrongylus colubriformis. The same dose rates also prevented establishment of Dictyocaulus viviparus infection but were ineffective against established infections of this parasite. In another two experiments the continuous release of morantel tartrate for at least 60 days (at rates between 0.65 and 1.11 mg/kg body weight per day) from a specially designed intraruminal sustained release bolus (secured at each end by a polyethylene impregnated semi-permeable membrane) was highly efficacious in both preventing the establishment of infections and removing established infections of the following species: O. ostertagi, T. axei, T. colubriformis and C. oncophora.

[Further observations on a focus of human trichostrongyliasis in the Viterbo resident]

Human cases of trichostrongyliasis recorded in Italy in Viterbo city were determined by T. axei, T. capricola, T. colubriformis and T. vitrinus. The authors refer the results of the treatment with piperazine hydrate and a benzimidazole derivative.

Observations on the fumarate reductase system in Haemonchus contortus and their relevance to anthelmintic resistance and to strain variations of energy metabolism

Fumarate reductase activity in a thiabendazole-resistant strain of Haemonchus contortus was found to be significantly lower than that from a susceptible strain. However, the fumarate reductase activity in a mebendazole-resistant strain did not differ from that in the susceptible strain, even though it was cross-resistant to thiabendazole. Published reports of fumarate reductase activity in strains of H. contortus susceptible or resistant to benzimidazoles were reassessed. A second, unrelated Australian thiabendazole-resistant strain also proved to have significantly diminished fumarate reductase activity, whereas two American strains, one resistant to thiabendazole and one to cambendazole, possess fumarate reductase activities indistinguishable from corresponding susceptible strains. It therefore appears that the phenomenon of benzimidazole resistance cannot be generally correlated with diminished fumarate reductase activity, although in the specific case of the Australian thiabendazole-resistant strains it may be a contributory factor.

Intestinal enzyme activity in lambs chronically infected with Trichostrongylus colubriformis: effect of anthelmintic treatment

After twenty weeks of continuous dosing with Trichostrongylus colubriformis larvae substantial, but declining, numbers of worms had persisted in most of the lambs examined, although there were wide inter-individual variations. Mucosal lesions were found in the proximal small intestines of all the infected animals, their severity being directly related to worm burden. Representative brush border enzyme activities analysed in intestinal mucosal extracts from the same lambs showed differing responses. Alkaline phosphatase and glycyl-L-leucine dipeptidase were significantly depleted, whereas maltase activity was only marginally reduced, and leucine aminopeptidase activity was normal. Mucosal acetylcholinesterase activity was significantly elevated in the parasitised animals and, interestingly in view of the postulated role of this enzyme in nematode pathogenicity, the level of activity was directly correlated with individual worm burdens. Intestinal trypsin and chymotrypsin activities were unaffected and the level of superoxide dismutase, an enzyme associated with the inflammatory response, was normal. There were also no consistent changes in the mucosal activities of several enzymes including lactic dehydrogenase, creatine phosphokinase, aldolase, and glutamic oxaloacetate transaminase, whose leakage from damaged or necrotic tissues has been well defined in terms of the concomitant increase in their activity in the circulation. Lambs treated orally with fenbendazole five and/or ten weeks before slaughter either in the presence or absence of continued larval intake, had negligible worm burdens, and showed little evidence of intestinal damage at post mortem. Brush border enzyme levels, with the exception of alkaline phosphatase and, in two cases dipeptidase, were normal in these animals. The activity of alkaline phosphatase was approximately double that in the continuously infected, untreated lambs, but remained markedly lower than in the uninfected controls. The activities of the other enzymes studied, including acetylcholinesterase, were within the control range. In summary, in chronic trichostrongylosis even relatively low nematode burdens were associated with marked pathological and biochemical damage in the intestine with both lesion severity and mucosal acetylcholinesterase activity being directly related to worm numbers. Although morphological integrity was completely restored after anthelmintic treatment, the persistent low activity of brush border alkaline phosphatase coupled with the enzymological findings in untreated, infected animals suggests that recovery of the full functional capability of the intestinal mucosa may take longer.

The role of absorbed drug in the efficacy of oxfendazole against gastrointestinal nematodes

Comparisons were made of the relative efficacy of ozfendazole (OFZ), administered to sheep at 5 mg/kg either as an oral drench, single intravenous injection or 12 and 24 divided intravenous injections over 24 and 48 hours, against benzimidazole-resistant Haemonchus contortus and Trichostrongylus colubriformis. A single intravenous injection was at least equally potent as the oral drench whilst the divided dose intravenous regimes significantly increased OFZ efficacy against both parasite species. These findings demonstrate that (i) absorbed drug is important for the efficacy of OFZ against nematodes in the abomasum and small intestine and may be more important than unabsorbed drug passing down the gastrointestinal tract, and (ii) the maintenance of plasma OFZ levels of approximately 2 micrograms/ml by divided dose regime increased efficacy compared with that achieved with the same total dose given as a single administration.

Anthelmintic activity of oxfendazole in pigs

Eighty-five pigs were artificially infected with Hyostrongylus rubidus, Oesophagostomum species and Ascaris suum. On days 2, 10, 20 or 51 after infection groups of six were treated with oxfendazole premix in food at various dose rates. Subsequently the pigs were slaughtered for comparative worm counts to be made in treated and control animals. The efficacy of treatment against hyostrongylus worms of increasing age was 68, 57, 99.8 and 100 per cent after a 3 mg per kg dose, 75, 75, 99.8 and 100 per cent after a 4.5 mg per kg dose and 81, 83, 99.8 and 100 per cent after a 6 mg per kg dose. In the case of Oesophagostomum species the corresponding figures were 78, 100, 100 and 100 per cent efficacy after a 3 mg dose, 93, 100, 100 and 100 per cent after a 4.5 mg per kg dose and 91, 99, 100 and 100 per cent after a 6 mg per kg dose. Ascaris infestation established too poorly for significant results to be obtained. It is concluded that a dose rate of 4.5 mg oxfendazole per kg body-weight should give practical control of Hyostrongylus and Oesophagostomum species in pigs.

Effect of oesophageal groove closure on the pharmacokinetic behaviour and efficacy of oxfendazole in sheep

Direct intraabomasal oxfendazole (OFZ) administration resulted in the peak plasma OFZ concentration occurring sooner and the area under the plasma OFZ concentration curve being reduced when compared with intraruminal administration. Glucose given directly into the abomasum of fistulated sheep caused a substantially greater elevation of plasma glucose levels than did direct administration into the rumen. This difference was subsequently used to indicate rumen bypass, by oesophageal groove closure, after oral dosing with an OFZ formulation to which glucose had been added. When 17 penned sheep were drenched with OFZ containing added glucose, elevated plasma glucose levels indicated substantial rumen bypass in six of them and was negatively correlated with time to peak plasma OFZ concentration, area under the plasma OFZ curve and efficacy against thiabendazole resistant Haemonchus contortus. Among 60 grazing sheep there were indications of some degree of oesophageal groove closure in 42 per cent of them following drenching with OFZ and in these animals there was a significant reduction in OFZ efficiency as measured by faecal worm egg counts.

Changes in the adenylate energy charge of Nematospiroides dubius and Trichostrongylus colubriformis paralysed by levamisole in vivo

The adenine nucleotide content and adenylate energy charge of Nematospiroides dubius from laboratory mice and of Trichostrongylus colubriformis from lambs has been measured. Administration of the anthelmintic, levamisole, to infected hosts resulted in only a slight fall in the adenylate energy charge of N. dubius over a 3-h period but there was a greater fall in the adenylate energy charge of T. colubriformis during this period. In neither case did the energy charge fall quickly, nor did it fall to the low levels which would be expected if the levamisole were inhibiting synthesis of ATP. The changes in energy charge of the nematodes which occurred following administration of levamisole to their hosts was of the order which can be satisfactorily explained by changes in the environment of the nematodes, such as reduced oxygen tension. It is concluded that the maintenance of levamisole-induced paralysis of these two species of trichostrongyle in vivo does not rely on the inhibition of fumarate reductase.

Anthelmintic efficiency of ivermectin against naturally acquired bovine gastrointestinal nematodes

Ivermectin, one of the new avermectin group of anthelmintics, was more than 99 per cent effective in removing all stages of Ostertagia ostertagi including inhibited larvae, and adult Trichostrongylus axei when administered to cattle orally at 100 microgram/kg body-weight or subcutaneously at 100 and 200 microgram/kg body-weight. High efficacy (> 98.6 per cent) was also obtained against adults and inhibited larvae of Cooperia oncophora at 100 microgram/kg orally or 200 microgram/kg by subcutaneous injection. The latter treatment caused an 82.3 per cent reduction of adult Nematodirus helvetianus.

Economic value and course of infection after treatment of cattle having a low level of nematode parasitism

To determine whether it is economically advantageous to treat calves having inapparent parasitism, we conducted experiments from 1971 to 1976, involving more than 1,800 calves from 30 pens or lots, using formulations of thiabendazole, levamisole, and crufomate (ruelene). Differential egg counts, cultured larvae, and cultured parasitic stages were used to estimate the kind and degree of nematode parasitism. Differentiation of infective larvae consistently established Cooperia as the predominating (%) genus in all fecal samplings. Bunostomum, when initially present, decreased or disappeared, whereas Trichostrongylus increased; other genera fluctuated less consistently. These qualitative generic fluctuations were not primarily the result of treatment, but more likely were seasonal variation. Judged by average daily gain (ADG), anthelmintic treatment was statistically advantageous at one or more points during the observation periods in 10 of 13 treated groups. In seven treated groups, the observation periods were concluded with statistical advantage in ADG, whereas in three groups, compensatory gain by corresponding controls had neutralized earlier advantages. The comparative influence of the various anthelmintics was not consistent from year to year. When total cost/kilogram gain was calculated from feed efficiency measuremnts and other costs, economic treatment advantage was evident in seven of 11 tests (7 of 10 treatment groups) from 1973 through 1976. This financial advantage, due primarily to feed efficiency and noted after 28 to 51 days, justified anthelmintic treatment. This advantage was not likely lost by the animals in subsequent periods (to 218 days) on pasture or in lots, since ADG indicated the treated calves performed either as well as, or better than, the nontreated controls. Considering all aspects of the study, the results indicate calves coming into Kansas from southern states and weighing 184 to 267 kg may possess a level of subclinical (symptomless) nematode parasitism that when treated will result in a response justifying expense for using anthelmintics.

Efficacy of oxfendazole against Nematodirus battus and inhibited stages of sheep nematodes

Oxfendazole administered at a dose rate of 5 mg/kg was 100 per cent effective against artificially acquired seven-day-old and 23-day-old infections of Nematodirus battus in lambs. At the same dose rate it was 100 per cent effective against naturally acquired infections of adult Trichostrongylus spp, adult and arrested early fourth stage larvae of Haemonchus contortus and Nematodirus spp. Efficacy against Ostertagia spp was 99 to 100 per cent against adults and 100 per cent against inhibited larvae, the predominant species of this genus being O circumcincta.

The effect of a preparturient fenbendazole treatment on lactation yield in dairy cows

Studies carried out on nine farms in north-west England indicated that fenbendazole treatment of adult winter calving dairy cows in the dry period caused an overall increase of 173 kg in their subsequent lactation yield. There was some evidence to suggest that a correlation existed between pasture Ostertagia ostertagi larval burdens and subsequent serum pepsinogen and milk yield responses post treatment. Marked interherd and regional differences existed in the milk yield response to anthelmintic treatment and possible reasons for such results are discussed.

The efficacy of fenbendazole at a dosage rate of 7,5 mg/kg against nematode infestations in cattle

Fenbedazole, dosed to artificially infested cattle at 7,5 mg/kg live mass, was more than 80% effective in more than 80% of the treated animals against immature and adult Haemonchus placei, Ostertagia ostertagi; Cooperia spp., Bunostomum phlebotum and Oesophagostomum radiatum.

Efficacy of anthelmintics against cattle nematodes

The efficacies of fenbendazole and thiabendazole against artifically acquired cattle nematodes and the efficacies of fenbendazole, prabendazole and levamisole against naturally acquired cattle nematodes were studied in western Victoria. Fenbendazole significantly (P less than 0.05) reduced numbers of late and early fourth stage larvae (greater than 96%), artificially acquired Cooperla spp (100%) and naturally acquired adult Ostertagia ostertagi (98%) and Trichostrongylus axei (90%). Thiabendazole significantly reduced numbers of artificially acquired late fourth stage larvae (83%) and parbendazole significantly reduced numbers of adult O. ostertagi (72%) in one group of cattle. Fenbendazole was the most effective anthelmintic.

Anthelmintic efficiency of oxfendazole, fenbendazole and levamisole against naturally acquired infections of Ostertagia ostertagi and Trichostrongylus axei in cattle

The anthelmintic efficiencies of oxfendazole, fenbendazole and levamisole, each at 4 dose rates spanning the manufacturers' recommended dosages were compared in beef cattle with naturally acquired infections of Ostertagia ostertagi and Trichostrongylus axei. In 8 of the 9 cases tested there was no significant increase in anthelmintic efficiency due to increased dose rates of any of the drugs. Percentage efficiencies and their standard errors, calculated from mean worm counts of pooled data for adult worms, developing 4th stage and early 4th stage larvae of O. ostertagi, were respectively, 86.9+/-4.2, 77.4+/-6.1, 74.5+/-7.3 for oxfendazole, 93.7+/-2.0. 80.7+/-6.8, 59.6+/-13.9 for fenbendazole and 69.7+/-6.9, 39.4+/-14.8, 31.2+/-22.6 for levamisole. Counts of O. ostertagi from cattle treated with oxfendazole and fenbendazole were not significantly different, but both were significantly lower than those from cattle given levamisole. Efficiency against T. axei exceeded 99% for all drugs. Practical implications for therapy and preventative control of ostertagiasis are discussed.

[Study of the effectiveness of morantel tartrate (Exhelm II) in bovine gastrointestinal strongylosis in Ivory Coast]

A study of the seasonal incidence of the strongyles of the bovine digestive tract, under natural climatic conditions (rainfall, humidity and temperature) and the use of Morantel Tartrate (Exhelm II, Pfizer, France) for its control was conducted, in the North of the Ivory Coast during 1976-1977. Young calves belonging to the local breeds Baoulé, N'Dama, and cross bred Zebus-taurins employed for this study were located in the East, West, North and Centre of the Korhogo area. On the basis of the results obtained it could be concluded that: the infestation rate calculated on the basis of egg output, increases during the rainy season, between April and October and decreases during the dry season namely between November and March/April; the animals treated twice or three times with Exhelm II expelled considerably less E.P.G., in comparison to that of the control group. It is suggested that this drug may be used at the dosage rate of 7,5 mg per kg live body weight under field condition at least twice in a year, at the beginning and at the end of the rainy season. A third treatment using this same anthelmintic during the rainy season does not seem to be more profitable than two treatments. As such this third treatment should not however be considered as being essential. N'Dama and Baoule of that region have mixt infection of strongyles comprising of Trichchostrongylus 38%, Oesophastomum 30%, Cooperia 17%, Bunostomum 16%, Haemonchus 15%, Hematodirus 2% and Ostertagia 0,2%.

Efficacy of albendazole for treatment of naturally acquired nematode infections in Washington cattle

Albendazole, methyl 5-propylthio-1H-benzimidazol-2-yl carbamate, was given as a bolus (7.68 to 8.18 mg/kg of body weight) to cattle naturally infected with gastrointestinal nematodes and lungworms in a controlled trial. Over 99% of adult Ostertagia ostertagi, Trichostrongylus longispicularis, Cooperia oncophora, Nematodirus helvetianus, and Dictyocaulus viviparus were removed by the treatment. Efficacy against immature O ostertagi, early fourth-stage O ostertagi, and Oesophagostomum radiatum was 95.2%, 86.6%, and 96.7%, respectively. In a field trial, the same compound administered in a paste formulation (at approximately 7.5 mg/kg) eliminated over 99% of strongylin and Moniezia eggs from feces of treated cattle.

Anthelmintic activity of albendazole in white-tailed deer

Albendazole at dose rates of 11 to 54 mg/kg (mean of 25 +/- 11 SD) of body weight was highly effective (greater than 99%) against Haemonchus contortus, Ostertagia odocoilei, O mossi, Trichostrongylus askivali and Nematodirus odocoilei in 22 white tailed deer (Odocoileus virginianus) in southern Texas. It was 38% effective against mature and immature deer liver flukes (Fascioloides magna). Toxicoses associated with treatment were not observed. Large numbers of abomasal nematodes (mean of 2,949 +/- 3.147 SD) were recovered from 16 untreated control deer, indicating these may have had a potential impact on herd health and indicating the importance of treatment or other management alternatives.

Anthelmintic activities of fenbendazole against Nematodirus helvetianus in cattle: effect on egg production, embryogeny, and development of larval stages

Calves experimentally infected with Nematodirus helvetianus were treated with a single dose of fenbendazole at the rate of 5 mg/kg of body weight. Fenbendazole was found to have an efficacy of 97.4% against adult N helvetianus. Additionally, eggs recovered 12 hours after calves were given the anthelmintic had fewer and frequently abnormal blastomeres. Fewer eggs were evident at 36 hours after treatment, and none was found at 72 hours or later. On the culturing of eggs from manure passed at 12 hours and later, almost no larval stages developed.

Thiophanate as a low daily dosage anthelmintic in sheep

Thiophanate administered daily at low dosages reduced nematode faecal egg output, egg hatchability and parasitic worm burdens in treated lambs and ewes. Six daily doses of 1 or 3 mg per kg thiophanate (approximately 1/25th to 1/75th of the median therapeutic dose), given to lambs experimently infected with Trichostrongylus colubriformis, were partially effective in suppressing faecal egg output and egg hatchability. Six doses of 5 mg per kg per day were effective in lambs infected with Haemonchus contortus and Nematodirus spathiger. Daily doses of thiophanate (50 or 200 mg per head) given over 14 weeks to lambs grazing contaminated pasture resulted in improved productivity (the higher dosage) and suppression of output of viable eggs and reduced worm burdens (both dosages). Reduced output of viable eggs was also obtained in housed, lactating ewes receiving 5 or 7 mg per kg thiophanate dispersed daily in the feed for 11 or nine weeks respectively after lambing.

Anthelmintic activity of fenbendazole against gastrointestinal nematodes in calves

Anthelmintic activities of fenbendazole were evaluated in a controlled experiment. Forty calves artificially infected with gastrointestinal nematodes were allotted to 4 groups. Calves in group 1 were used as nonmedicated controls; the other calves were given (orally) fenbendazole at the dose level of 5 mg/kg in the forms of a suspension (group 2), medicated feed to individual calves (group 3), and medicated feed to the group (group 4). These treatments were given on day 35 after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 99.5%, 99.7%, and 99.6%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes present in the calves were Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia onchophora, C punctata, and Oesophagostomum radiatum.

The efficacy of in-feed medication with fenbendazole against gastrointestinal nematodes of sheep, with particular reference to inhibited larvae

Anthelmintic activity of fenbendazole in a feed formulation was tested against nematode parasites of sheep. Dose rates ranging from 1.4 mg per kg for four days to 0.4 mg per kg for 14 days removed 98 to 100 per cent of the total gastrointestinal worm burden, including large numbers of inhibited fourth stage larvae of Ostertagia circumcincta. One hundred per cent effectiveness against adult Dictyocaulus filaria was also recorded.

Effect of albendazole on gastrointestinal parasites of cattle

The efficacy of albendazole in removing gastrointestinal nematodes and tapeworms was studied in 16 treated and 16 untreated (control) beef calves. The anthelmintic was administered as an oral drench at a dose level of 5 ml/45.5 kg of body weight (5 mg/kg). Percentage of efficacy against the various genera was: Trichostrongylus axei, Oesophagostomum radiatum, and Moniezia-100.0; Haemonchus placei, Cooperia spp, and Trichostrongylus colubriformis - greater than 99.0; Ostertagia ostertagi -98.3; and Bunostomum phlebotomum -96.2. Efficacy against Trichuris was 20.2. Efficacy against immature nematodes in the abomasum and small intestine was high, 91.9 and 86.4, respectively, but total numbers of nematodes were not large. Efficacy against immature stages in the cecum and remainder of the large intestine was 48.5. Signs of toxicosis were not observed in calves treated with albendazole.

Controlled trials of the anthelmintic oxfendazole in ewes and lambs naturally infected with gastrointestinal nematodes

Oxfendazole doses at a rate of 5 mg per kg, before or after lambing, reduced nematode egg output to insignificant levels in ewes, most of which were not exposed to re-infection. Ewes treated with oxfendazole had a significantly lower egg output than those treated with levamisole, although the latter anthelmintic was also highly effective. In lambs, oxfendazole at a dose rate of 5 mg per kg, showed 100 per cent efficacy for Ostertagia circumcincta, O trifurcata, Teledorsagia davtiani, Trichostrongylus axei, T vitrinus, T colubriformis, Nematodirus battus, N filicollis, immature Nematodirus, Chabertia ovina, and 93 per cent efficacy for Trichuris spp. Levamisole showed similar efficacies but did not remove Trichuris.

Anthelmintic dihydroquinoxalino[2,3-b]quinoxalines

A series of dihydroquinoxalino[2,3-b]quinoxalines was synthesized and tested for anthelmintic activity in a model assay. The most promising compound, 5,12-diacetyl-5,12-dihydroquinoxalino[2,3-b]quinoxaline, was orally effective in sheep at a dose of 200 mg/kg against a broad range of helminths.

Anthelmintic efficiency of oxfendazole in California lambs

Oxfendazole, methyl 5(6)-phenylsulfinyl-2-benzimidazole carbamate, was given by oral drench (5 mg/kg) to California lambs harboring natural infections of gastrointestinal nematodes. Ninety-nine percent of adult Ostertagia circumcincta, Ostertagia trifurcata, Trichostrongylus axei, Trichostrongylus vitrinus, Trichostrongylus colubriformis, Nematodirus filicollis, and Nematodirus spathiger were removed by the anthelmintic.

Anthelmintic activity of albendazole against gastrointestinal nematodes in calves

Anthelmintic activities of albendazole were evaluated in a controlled experiment. Forty calves experimentally infected with gastrointestinal nematodes were allotted to 4 groups. Calves in group 1 were used as nonmedicated controls; calves in groups 2, 3, and 4 were given (by oral route) a suspension containing albendazole at dose concentrations of 2.5, 5.0, and 7.5 mg/kg of body weight on the 35th day after administration of infective nematode larvae. In groups 2, 3, and 4 calves, average overall reductions (based on geometric means) were 77.1, 93.6, and 98.1%, respectively. These reductions were highly significant (P less than 0.01) in calves given doses of 5.0 and 7.5 mg/kg, and were significant (P less than 0.05) in calves given the 2.5-mg/kg dose. Ostertagia ostertagi, Trichostrongylus axei, Cooperia onchophora, Cooperia punctata, and Oesophagostomum radiatum removals at the 5.0- and 7.5-mg/kg dose levels were all highly significant (P less than 0.01); whereas, removals of Haemonchus contortus were not significant, even at the 7.5-mg/kg dose level.

Levamisole: anthelmintic activity in calves following dermal application

A series of seven experiments designed to evaluate the anthelmintic efficacy of levamisole (1-tetramisole) by dermal application is described. This work involved use of 181 artificially infested calves. The drug was formulated at a concentration of 10% m/v levamisole base in a solvent system promoting dermal absorption and was applied to both sides of the spine in the lumber region at a dose rate of 10 mg levamisole base per kg livemass. A consistent performance was achieved in these investigations, the results from all of which were based upon necropsy findings. Efficacy of treatment was assessed against the third and fourth larval stages and fifth stage larvae/adult worms of six nematode species; the respective efficacies obtained were Haemonchus placei 72,0%; 99,3%; and 100%: Ostertagia ostertagi 85,5%; 38,1% and 74,5%: Cooperia spp. 98,9%; 99,9% and 100%: Bunostomum phlebotomum 83,0%; 100% and 98,5%: Oesophagostomum radiatum 47,4%; 94,9% and 99,6% and Dictyocaulus viviparus 79,5%; 94,1%; 90.9% (fifth stage larvae) and 93,8% (adult worms). The anthelmintic efficacy of levamisole in these experiments is of the same order as that achieved by orthodox methods of administration at dose rates between 7,5 and 10,0 mg levamisole HC1 per kg livemass. These findings add a new dimension to the use of levamisole and to anthelmintic therapy in general.

Further controlled evaluations of fenbendazole as a bovine anthelmintic

The efficacy of fenbendazole (methyl-5-(phenythio)-2-benzimidazole-carbamate) in cattle parasitized by the lungworm Dictyocaulus viviparus and in other cattle parasitized by Haemonchus, Ostertagia, Trichostrongylus, Cooperia, and Oesophagostomum was investigated in 3 controlled critical experiments. A single treatment with 5.0 mg/kg of body weight administered in the feed or in a 10% suspension exceeded 99% efficacy against these helminths. Dosages of 1, 0.5, 0.35, and 0.25 mg/kg of body weight administered for 5 days to individual calves in their feed were 99% efficacious against all helminths, except Haemonchus. The 1.0 mg/kg dose removed 99.5% of the Haemonchus, and the other 3 dosages had efficacies of 91.0, 93.7, and 95.6%, respectively. The small daily dosages were not evaluated against Dictyocaulus.

Evaluation of the effect of different methods of control of soil-transmitted helminths in Khuzestan, southwest Iran

Three methods of control of soil-transmitted helminths, namely, sanitation, mass-treatment, and sanitation plus mass-treatment, were tried in 15 villages in Khuzestan, southwest Iran. Stool samples from the inhabitants of each village were examined both quantitatively and qualitatively just before starting each control method and again about 4 years later, except for the inhabitants of one village whose stools were re-examined 7 months after moving to a new settlement. Sanitation measures consisted of one latrine for each family and the provision of a sanitary water supply in each village. The drugs piperazine and bephenium hydroxynapthoate were administered alternately every 3 months. The reduction in rates of infection with Ascaris, hookworm, and Trichostrongylus spp., respectively, for the above mentioned methods were as follows: sanitation alone, 28%, 4% and 30%; mass-treatment alone, 84%, 73%, and 31%; sanitation plus mass-treatment, 79%, 69%, and 30% and in the newly constructed village, 76%, 21%, and 38%. In a control group corresponding reductions were 19%, 11%, and 31%. The percentage of egg reduction in persons still infected with these three parasites was, respectively, as follows: mass-treatment plus sanitation, 88%, 88%, and 53%; mass-treatment alone, 90%, 87%, and 37%; sanitation alone, 60%, 26%, and 0.6%; in the newly constructed village, 87%, 78%, and 39%; and in the control group, 29% increased 12%, and 24.5%. The significance of these findings is discussed.

Efficacy of albendazole against Haemonchus, Nematodirus, Dictyocaulus, and Monieza of sheep

Albendazole was highly efficacious in the removal of monospecific and mixed infection of Haemonchus contortus, Nematodirus spathiger, and Dictyocaulus filaria from sheep. A dose level of 5 mg/kg removed nearly all gastrointestinal nematodes, and 10 mg/kg removed all lungworms. Tapeworms of the genus Moniezia were completely removed by a dose level of 10 hg/kg.

Efficacy of albendazole against gastrointestinal nematodes of cattle

Forty-five calves with artificial and pasture-acquired nematode infections were medicated with albendazole at dose levels of 0, 2.5, 5.0, or 10 mg/kg of body weight. A dose level of 2.5 mg/kg removed at least 99% of adult Trichostrongylus axei, Trichostrongylus colubriformis, Cooperia oncophora, and Bunostomum phlebotomum. Burdens of Haemonchus contortus, Strongyloides papillosus, and Ostertagia ostertagi were reduced 79, 88, and 97%, respectively. At a dose level of 5.0 mg/kg, at least 95% of all adult nematodes were removed; at 10 mg/kg, at least 97% were removed. At least 99% of 4th-stage larvae of O ostertagi, T axei, C oncophora and T colubriformis and 96% of H contortus were expelled at a dose level of 2.5 mg/kg. At 5.0 and 10 mg/kg, 99 to 100% of all species of larvae were removed. Trichuris spp adults were slightly susceptible at all dose levels; larvae were susceptible (83%) only at 10 mg/kg.

Evaluation of oxfendazole against natural infections of gastro-intestinal nematodes and lung-worms in calves

The anthelmintic activity of oxfendazole (Syntex) was tested in calves at dosages of 2-5 and 5-0 mg per kg. At both dose levels, oxfendazole showed 100 per cent efficacy against adult Ostertagia ostertagi, O lyrata, O cremensis, fifth stage Ostertagia spp and adult Haemonchus spp. Against adult Cooperia oncophora, efficacy was 99.8 per cent and 100 per cent at doses of 2.5 mg per kg and 5.0 mg per kg respectively while at both dose levels 100 per cent activity was recorded against C surnabada and fourth and fifth stage Cooperia spp. One hundred per cent efficacy was obtained with both dose levels against adult and fifth stage Dictyodaulus viviaprus; against Trichuris spp, percentage efficacy was 92 and 100 per cent at doses 2.5 and 5.0 mg per kg respectively. Oxfendazole showed higher efficacy than levamisole against Ostertagia spp but against the other species encountered, both anthelmintics possessed similar efficacy. Both anthelmintics significantly increased the calves' weight gains.

Efficacy of oxibendazole against gastrointestinal nematodes of cattle

In 3 separate studies, oxibendazole in drench and premix formulation was shown efficacious against larvae and adults of the genera Haemonchus, Ostertagia, Trichostrongylus, Strongyloides, Nematodirus, Cooperia, Bunostomum, Capillaria, Oesophagostomum, and Trichuris. In the first study, artificially infected calves were cleared of virtually all histotrophic larvae and adult parasites after medication with oxibendazole drench at a dose level of 10 mg/kg of body weight. Smaller doses (7.5 and 5.0 mg/kg) expelled 84 to 100% of the parasites. Oxibendazole at a dose level of 15 mg/kg in premix form was given to artificially infected calves 3, 7, or 42 days after infection in a 2nd study. Third stage and 4th stage Cooperia oncophora larvae were, respectively, 92 and 98% susceptible to the drug at day 3 and day 7 after infection; neither larval stages of Ostertagia ostertagi and of Oesophagostomum radiatum were susceptible. Premix given on day 42 after infection removed 83 to 100% of adult O ostertagi, Nematodirus spp, C oncophora, O radiatum, and Trichuris spp. In a 3rd study, calves harboring a mixture of parasitic stages from artificial and pasture-acquired infections were medicated with oxibendazole at a dose of 15 mg/kg in premix form. The burdens of larvae from the abomasum and small intestines were reduced 93 to 95%, respectively; the burdens of adults of 11 species of worms were reduced 87 to 100%.