morantel and Ostertagiasis

A comparison was made of the efficacy and parasitological sequelae over 2 years, of continuous and intermittent periods of anthelmintic suppression applied both early and in the middle of the first grazing season of calves. Five groups of 15 calves grazing separate paddocks within the same field were allotted to one of the following treatment regimes during their first year at grass: Group 1, untreated controls; Group 2, treated with ivermectin injections at 3, 8 and 13 weeks after turnout; Group 3, treated with ivermectin injections at 10, 15 and 20 weeks after turnout; Group 4, treated with a morantel slow release intraruminal bolus at turnout; Group 5, treated with a morantel slow release bolus at 10 weeks after turnout. Five animals from each group were slaughtered at the end of both grazing seasons. Two months after the end of the second season the remaining five calves were challenged with an experimental infection of 250,000 third-stage larvae (L3) of both Ostertagia ostertagi and Cooperia oncophora. All treatment regimes protected the respective calves from parasitic gastroenteritis. Over the 2 year observation period Groups 2 and 4 showed significantly better weight gain than other groups, and at the end of the first season, they were found to harbour significantly fewer O. ostertagi in the early fourth stage of development. During Year 1, Groups 2 and 3 excreted much lower percentages of Ostertagia spp. eggs than other groups. In Year 2, Group 2 excreted a higher percentage of Ostertagia spp. eggs although the total egg output was approximately half that of Group 1 during the same period. The results showed that the effects of anthelmintic suppression on egg output of different nematode species was affected by the activity of the anthelmintic used.

Topics: Animal Feed; Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Helminthiasis; Helminthiasis, Animal; Injections; Ivermectin; Morantel; Ostertagiasis; Parasite Egg Count; Pepsinogens; Poaceae; Seasons

Topics: Animals; Anthelmintics; Benzimidazoles; Drug Resistance; Feces; Morantel; Ostertagia; Ostertagiasis; Parasite Egg Count; Random Allocation; Sheep; Sheep Diseases

Morantel could not be detected (< 0.05 microgram/ml) in the plasma of cattle or goats following the oral administration of morantel tartrate at a dose rate of 10 mg/kg bodyweight. No morantel was detected in the milk of lactating goats except in one animal where a concentration of 0.092 microgram/ml was detected at 8 h after drug administration. Morantel was highly effective against Cooperia oncophora infections in calves treated 6, 9 or 18 days after infection; however, was highly effective against Ostertagia ostertagi only when treated 18 days after infection. Morantel did not affect the fecundity of adult O. ostertagi surviving treatment 18 days after infection which had similar average numbers of eggs in their uteri (range 13.4 +/- 0.73-16.8 +/- 0.98) as did parasites from control animals (range 12.0 +/- 0.70-13.6 +/- 0.66). Morantel could be detected at a concentration of 96 +/- 4.5 micrograms/g (dry weight) in the faeces of a calf 24 h after treatment with 10 mg/kg bodyweight of morantel tartrate. The concentration of morantel in replicate samples of this faeces exposed to natural atmosphere, but not to soil or soil organisms, declined slowly over the following 322 days. At day 322 after the start of the experiment 8.8 micrograms/g of morantel could be measured in the remaining faecal material. Throughout the faecal degradation study the concentration of morantel in the crusts of the replicate sample pats was lower than the concentration in the core samples.

Topics: Animals; Cattle; Cattle Diseases; Feces; Goats; Milk; Morantel; Nematode Infections; Ostertagiasis

An experiment was conducted in calves to investigate the efficacy of a morantel sustained release trilaminate bolus (MSRT) to control gastrointestinal parasitism and to assess the development of immunity during the use of MSRT. Two groups (M and U) of four calves each were infected three times a week with a mixed Ostertagia ostertagi and Cooperia oncophora infection for 12 weeks. Calves of Group M received an MSRT at the start of the experiment. Twenty weeks after the start of the experiment, all animals, including a previously uninfected control group (C), received a challenge with 100,000 Ostertagia and 100,000 Cooperia. After a further 4 weeks all calves were necropsied for worm counts. During the trial calves were weighed and faecal egg counts, larval differentiation and pepsinogen concentrations were determined. The results demonstrated the high level of efficacy of the MSRT in reducing the faecal egg output and preventing parasitic gastroenteritis under conditions of a continuous high rate of infection. Efficacy of treatment was higher for Cooperia than for Ostertagia. Post-mortem worm counts suggested a partially impaired immunity build-up in Group M, at least for Cooperia.

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Feces; Immunity, Active; Intestinal Diseases, Parasitic; Morantel; Nematode Infections; Ostertagiasis; Parasite Egg Count; Pepsinogens; Random Allocation; Trichostrongyloidiasis; Weight Gain

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Drug Resistance; Feces; Female; Larva; Morantel; Nematoda; Ostertagia; Ostertagiasis

Two experiments with a morantel resistant strain of Ostertagia ostertagi were carried out. In the first experiment five groups of five calves were infected with 60,000 larvae of this resistant strain. Calves of one group remained untreated, calves of the other groups were treated with morantel tartrate, oxfendazole, levamisole or ivermectin in the recommended doses. It was demonstrated that there was side resistance to levamisole, but not to oxfendazole or ivermectin. Compared with the untreated controls the reduction percentages of the worm burdens were 45.3 (morantel tartrate), 99.7 (oxfendazole), 83.5 (levamisole) and 100 (ivermectin). In the second experiment a comparison was made between the effect of levamisole against a morantel susceptible strain of O. ostertagi and the resistant strain. Two groups of five calves were infected with the susceptible strain and two groups with the resistant one. One group of each pair remained untreated, the other was treated with levamisole. The reduction percentages of the worm burdens were 99.6 (susceptible strain) and 63.6 (resistant strain). This result confirms the efficacy of levamisole to susceptible O. ostertagi and the side resistance of the morantel resistant strain.

Topics: Animals; Anthelmintics; Cattle; Cattle Diseases; Drug Resistance; Female; Male; Morantel; Ostertagia; Ostertagiasis

An experiment was conducted in calves to investigate the effect of sustained release and pulse release anthelmintic intraruminal boli on the development of pathophysiological changes following daily infection with Ostertagia ostertagi and Cooperia oncophora for six weeks. After infection various pathophysiological changes were detected including increases in serum pepsinogen concentration, enteric plasma protein losses and in the catabolic rate of albumin. Such changes developed rapidly in the unprotected calves following patency after 17 days and persisted until the termination of the study. There were indications that the sustained anthelmintic release device was more efficacious than the pulse anthelmintic release device in reducing the worm burdens and early pathophysiological changes associated with infection. It was found at necropsy that the release of anthelmintic by the oxfendazole pulse release bolus had been delayed in several calves.

Topics: Animals; Anthelmintics; Benzimidazoles; Blood Proteins; Cattle; Cattle Diseases; Delayed-Action Preparations; Intestinal Diseases, Parasitic; Male; Morantel; Ostertagiasis; Parasite Egg Count; Pepsinogens; Serum Albumin; Trichostrongyloidiasis

Changes in anthelmintic resistance in nematode parasites were monitored in sheep grazing on 2 separate farms, but with the same anthelmintic treatment program, over 16 years. High levels of benzimidazole resistance emerged in Ostertagia and Trichostrongylus spp populations on both farms following 9 years of continuous use of this class of drug. Subsequently, variations in the levels of resistance occurred for the same species between farms and between species on the same farm. A change to levamisole for 2 years resulted in a significant reversion towards benzimidazole susceptibility, but a concomitant rise in levamisole resistance, in Ostertagia on one farm. However, benzimidazole resistance increased rapidly following the re-introduction of oxfendazole into the anthelmintic treatment program. Results from both farms illustrate the pitfalls of using one anthelmintic class for an extended period and provide indirect support for the alternation of anthelmintic classes at approximately yearly intervals.

Topics: Animals; Antinematodal Agents; Benzimidazoles; Drug Resistance; Levamisole; Morantel; Ostertagia; Ostertagiasis; Sheep; Sheep Diseases; Trichostrongyloidiasis; Trichostrongylosis; Trichostrongylus

An experiment was carried out to assess the effect of morantel tartrate in the faeces of calves treated with a bolus on the survival and development of Ostertagia ostertagi eggs. Since the drug delivered from the bolus greatly reduces the nematode population in an infected animal and thus the number of eggs excreted it was necessary to mix O ostertagi eggs into the faeces of calves to which boluses had been administered. In three preliminary experiments it was shown that the methods used to extract the nematode eggs from faeces of infected cattle and remix them into faeces from uninfected cattle did not appear to affect their development into larvae or their even distribution in the faeces into which they had been remixed. The concentration of morantel tartrate lethal to O ostertagi eggs was in the range 0.0015 to 0.0025 M in vitro. It was demonstrated that the presence of the drug in the faeces of dosed calves prevented the maturation of approximately 99 per cent of O ostertagi eggs to infective larvae between days 7 and 84 after the administration of a bolus and of 75 per cent on day 91. These results help to explain the well recognised effect of the bolus in cleaning pastures of O ostertagi.

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Feces; Larva; Male; Morantel; Ostertagia; Ostertagiasis; Parasite Egg Count; Pyrimidines; Trichostrongyloidiasis

Topics: Animals; Anthelmintics; Drug Resistance; Drug Therapy, Combination; Fenbendazole; Levamisole; Morantel; Organophosphorus Compounds; Ostertagiasis; Sheep; Sheep Diseases; Trichostrongyloidiasis; Trichostrongylosis

Herbage intake was measured in two groups of 20 first-year grazing cattle. The animals in one group each received a morantel sustained release bolus at turnout to control nematode parasitism and the animals in the other group remained untreated. The latter group showed a mean peak faecal egg count of 655 eggs per gram (e.p.g.) in October associated with high serum pepsinogen concentration and clinical signs of ostertagiasis, compared with a peak of 119 e.p.g. in the treated group which remained in good health. In September the daily voluntary feed intake of the untreated animals was significantly depressed (94 g kg-1 body weight vs. 77 g kg-1 P less than 0.001), but no difference in digestive efficiency was recorded between the two groups. This difference in feed intake was associated with a 47 kg mean live weight advantage of the treated animals at housing.

Topics: Animals; Body Weight; Cattle; Cattle Diseases; Delayed-Action Preparations; Digestion; Eating; Intestinal Diseases, Parasitic; Male; Morantel; Ostertagia; Ostertagiasis; Pyrimidines; Seasons; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylus

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Drug Resistance; Feces; Female; Larva; Morantel; Ostertagia; Ostertagiasis; Parasite Egg Count; Pepsinogens; Pyrimidines; Trichostrongyloidiasis

Topics: Animals; Body Weight; Cattle; Cattle Diseases; Delayed-Action Preparations; Feces; Female; Gastroenteritis; Intestinal Diseases, Parasitic; Larva; Morantel; Ostertagiasis; Parasite Egg Count; Pyrimidines; Trichostrongyloidiasis

Nematodiasis and its subsequent effect on production in Hereford weaner steers in western Victoria was studied during 1983 and 1984. In the first summer, steers were allocated to 2 replicates of 6 treatments--No treatment (Nil); Morantel slow release bolus in March (M1); Morantel bolus in March and June (M2); pour-on levamisole in January, May and July (R3); albendazole in January and July (V2) and albendazole in January, May and July, (V3). In 1984, treatment M2 was discontinued to provide extra replicates for Nil and M1. The replicate paddocks were 5 ha and were stocked with 7 and 8 steers in 1983 and 1984, respectively. Nematode egg counts in faeces, were generally less than 50 epg, indicating low numbers of adult nematodes. Faecal egg counts were highest in autumn and declined during the year. There was a significant (P = 0.02) effect of treatment on mean faecal egg count. Mean egg counts for treatment groups Nil and M1 were 16 and 10 epg above the overall mean (47 epg); those of the other treatments were 6 to 12 epg below the mean. There were no significant (P = 0.8) differences between treatments in the numbers of nematode larvae on pasture, during the experiment. At the end of both years of the experiment most nematodes (92%) were early fourth stage larvae of O. ostertagi. There were no consistent differences in nematode counts between treatments. There were no significant (P = 0.33) differences between treatments in bodyweights at any time during the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Albendazole; Animals; Anthelmintics; Australia; Benzimidazoles; Body Weight; Cattle; Cattle Diseases; Feces; Levamisole; Male; Morantel; Nematode Infections; Ostertagiasis; Parasite Egg Count; Seasons

Infective 3rd-stage larvae of Ostertagia and Cooperia, obtained from the feces of nonmedicated and morantel sustained-release bolus (MSRB)-treated calves, were orally administered to 2 groups of parasite-free calves. After a 42-day maturation period, a therapeutic dose of morantel tartrate was administered to half of the calves from each group. All calves were necropsied 7 days after treatment. After comparing the nematode counts for the nonmedicated and morantel-treated calves of each group, morantel tartrate was demonstrated to be equally effective against the nonmedicated-derived and MSRB-derived nematode populations. The sensitivity of Ostertagia spp and Cooperia spp to morantel tartrate, therefore, was not diminished after use of the MSRB for a single grazing season.

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Feces; Morantel; Ostertagiasis; Parasite Egg Count; Pyrimidines; Seasons; Trichostrongyloidea; Trichostrongyloidiasis

The morantel sustained release bolus was administered at turnout to first-season grazing calves in order to assess its efficacy in the seasonal control of infection by nematode parasites in Ireland. The pastures grazed by control calves showed a marked increase in gastrointestinal trichostrongylid infective larvae by September, while numbers of infective larvae on pasture grazed by bolus-treated calves remained at a low level throughout the grazing season. In consequence, the controls showed significantly higher worm egg counts in late season and significantly higher worm burdens (mainly Ostertagia spp) at necropsy carried out in November on representative number of principal animals selected from each group. These reduced worm burdens were attributed to the suppression of egg output during the early part of the season as a result of treatment with the morantel sustained release bolus at turnout in the spring. Pasture contamination with Dictyocaulus viviparus larvae was present on all treatment pastures. The bolus-treated calves however were subjected to an increase in D. viviparus infection which occurred on their pasture in late season after the active life of the bolus had expired. It was concluded that bolus treatment delayed (rather than prevented) the buildup of D. viviparus infection on the pasture by 60-90 days.

Topics: Animals; Body Weight; Cattle; Cattle Diseases; Delayed-Action Preparations; Dictyocaulus Infections; Drug Evaluation; Ireland; Male; Morantel; Ostertagiasis; Parasite Egg Count; Pyrimidines; Seasons; Trichostrongyloidiasis

Two field isolates of Ostertagia spp. of sheep from the Swellendam and Malmesbury districts in the south-western Cape were shown to be resistant to benzimidazole anthelmintics. At therapeutic dosage rates albendazole was 32,5%, thiabendazole 0%, oxfendazole 14,9% and morantel 91,4% effective against the adult stage of Ostertagia spp. in naturally infested lambs at Swellendam. Efficacy against the adult stage of the same isolate of Ostertagia spp. in artificially infested sheep in the laboratory was tested at dosage rates of albendazole 3,8% mg/kg or 7,6 mg/kg, mebendazole 15 mg/kg, levamisole 7,5 mg/kg and morantel 14,5 mg/kg and varied from 0%, 0%, 1,9% 53,9% and 87,0% respectively. Albendazole, the only anthelmintic tested against the Malmesbury strain of Ostertagia spp. was 9,8% effective against the adult stage in naturally infested lambs. Trichostrongylus spp. and Nematodirus spp. simultaneously present in these animals were fully susceptible to all the anthelmintics tested.

Topics: Abomasum; Animals; Anthelmintics; Benzimidazoles; Drug Resistance; Feces; Morantel; Ostertagiasis; Parasite Egg Count; Rumen; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidea; Trichostrongyloidiasis

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Dose-Response Relationship, Drug; Male; Morantel; Ostertagiasis; Pyrimidines; Time Factors; Trichostrongyloidea; Trichostrongyloidiasis

Benzimidazole resistant strains of Haemonchus contortus and Ostertagia spp were subjected to selection pressure over five laboratory generations with the recommended dose rates of either cambendazole, oxfendazole or morantel. A change in response, with larger residual worm burdens remaining after treatment at the fifth generation, was shown for both cambendazole and oxfendazole against both species of nematode. No change in response against either species are shown for morantel. The results are discussed in terms of the problem associated with inefficient removal of the adult parasites after treatment.

Topics: Animals; Anthelmintics; Benzimidazoles; Cambendazole; Carbamates; Drug Resistance; Haemonchiasis; Male; Morantel; Ostertagiasis; Selection, Genetic; Sheep; Sheep Diseases; Trichostrongyloidiasis

The anthelmintic efficacy of low-dose phenothiazine therapy, administered as a 1:40 phenothiazine: molasses mixture, was tested against patent infections of strains of Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia spp susceptible or resistant to thiabendazole (an other benzimidazoles), levamisole and morantel tartrate. Phenothiazine reduced faecal egg output for both susceptible and resistant strains of all three nematodes. In daily doses of 0.25 g per sheep per day and above it completely inhibited larval production in susceptible strains. Against resistant strains, there was a reduced efficiency with 82.3 per cent inhibition of egg hatch at the 0.25 g per sheep per day level. Phenothiazine treatment had no significant effect on worm numbers for either susceptible or resistant worms. It is suggested that benzimidazole-resistant strains may be cross-resistant to phenothiazine.

Topics: Animals; Drug Resistance; Haemonchiasis; Levamisole; Male; Morantel; Ostertagiasis; Phenothiazines; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylosis

Low-dose daily phenothiazine therapy, administered as a 1:40 phenothiazine:molasses mixture, was tested against sequential infections of strains of Haemonchus contortus. Trichostrongylus colubriformis and Ostertagia spp susceptible or resistant to thiabendazole, levamisole and morantel tartrate. Phenothiazine at a dose rate of 0.5 g per sheep per day significantly reduced the numbers of worm eggs per gram of faeces in both susceptible and resistant strains by an average of 48 per cent and 60 per cent respectively. Phenothiazine completely inhibited larval production in susceptible strains. With resistant worms, larval production was depressed by up to 85.7 per cent. Treatment with phenothiazine : molasses mixture reduced the numbers of worms which became established in resistant Ostertagia spp and susceptible T colubriformis but had no effect on the establishment of susceptible H contortus and Ostertagia spp or resistant H contortus and T colubriformis.

Topics: Administration, Oral; Animals; Drug Resistance; Haemonchiasis; Levamisole; Male; Morantel; Ostertagiasis; Phenothiazines; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylosis

The efficacy of a morantel sustained release bolus to control ostertagiasis in grazing calves was assessed. Administration of the bolus into the rumen of calves immediately before turnout on to spring pasture in May substantially reduced the level of pasture contamination with infective larvae later in the season. Compared with controls there was a 71 per cent reduction in worm burdens acquired over the entire grazing season with a mean improvement in weight gain of 24 kg. When administration was delayed until midsummer (July) a good anthelmintic effect was obtained but there was little reduction in pasture contamination levels. Worm burdens acquired over the grazing season were reduced by only 48 per cent with a mean weight gain advantage of only 9 kg compared with controls. The control obtained against Dictyocaulus viviparus by both treatments was not absolute, failing to prevent the development of mild parasitic bronchitis.

Topics: Animals; Cattle; Cattle Diseases; Delayed-Action Preparations; Dictyocaulus; Feces; Morantel; Ostertagiasis; Parasite Egg Count; Pyrimidines; Seasons; Trichostrongyloidea; Trichostrongyloidiasis

Merino and Border Leicester cross Merino sheep, nine months old, were infected with 10,000 third stage larvae of both Trichostrongylus colubriformis (PF4) and Ostertagia circumcincta/O trifurcata (PF5), known to have varying degrees of resistance to levamisole, morantel tartrate and thiabendazole. Crossbred sheep carried heavier Ostertagia sp worm burdens but there was no difference in susceptibility between the two breeds of sheep to infection with T colubriformis. The anthelmintic efficacy of thiabendazole, at 50 mg/kg, against T colubriformis was 81.8 per cent and 92.4 per cent for Merinos and crossbreds respectively while levamisole, at 6.75 mg/kg, was 12.3 per cent and 18 per cent effective. Thiabendazole removed 92.3 per cent and 83.8 per cent of Ostertagia sp in Merinos and crossbreds respectively. However, worm burdens in levamisole treated sheep were not significantly different from controls. No significant breed differences were found in 24 h faecal egg outputs. It is suggested that breed differences previously described in four-month-old sheep may have been due to differences in the rate of development of immune responsiveness. This disparity was no longer detectable in the immunologically mature sheep used in this study.

Topics: Animals; Drug Resistance; Female; Levamisole; Male; Morantel; Ostertagiasis; Pyrimidines; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylosis

Strains of Trichostrongylus colubriformis (designated PF4) and Ostertagia sp (O circumcincta/O trifurcata, designated PF5), with varying degrees of resistance to levamisole, morantel tartrate and thiabendazole were isolated into pure culture. Detailed dose response studies showed that both T colubriformis and Ostertagia sp were highly resistant to levamisole and morantel with low level resistance to thiabendazole. The effective dose required to remove 80 per cent worm burdens (ED80) was calculated for each anthelmintic. For T colubriformis the ED80 for levamisole and thiabendazole were 12.6 and 40.1 mg/kg respectively. For Ostertagia sp, the ED80 for levamisole, thiabendazole and morantel were 20.4, 45.2 and 35.8 mg/kg respectively. The implications of these results are discussed with reference to alternative means of chemical control.

Topics: Animals; Drug Resistance; Female; Levamisole; Male; Morantel; Ostertagiasis; Pyrimidines; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylosis

Field strains of Trichostrongylus colubriformis and Ostertagia circumcincta, designated PF4 and PF5 respectively, were recovered from a farm on which the sole use of levamisole over a preceding 12 year period led to the development of anthelmintic resistance. The results of field observations and preliminary critical trials in both Merino and crossbred sheep showed that both species have varying degrees of resistance to three major anthelmintics; levamisole, morantel tartrate and thiabendazole. Mean worm count reductions for adult T colubriformis (PF4) for therapeutic doses of morantel tartrate, thiabendazole and levamisole in crossbreds were 45.7 per cent, 97.3 per cent and zero respectively, and for Merinos 80.7 per cent, 88.3 per cent and 92.0 per cent respectively. Against O circumcincta the corresponding reductions for crossbreds were 51.4 percent, 95.4 per cent and 20.3 per cent and for Merinos, 52.5 per cent, 73.1 per cent and 29.8 per cent. There was no statistically significant difference in the responses of both parasite species to either levamisole or morantel. This result suggests that resistance to the two chemically unrelated drugs may be co-inherited.

Topics: Animals; Drug Resistance; Levamisole; Morantel; Ostertagiasis; Pyrimidines; Sheep; Sheep Diseases; Thiabendazole; Trichostrongyloidea; Trichostrongyloidiasis; Trichostrongylosis

Topics: Animals; Drug Resistance; Levamisole; Morantel; Ostertagiasis; Pyrimidines; Selection, Genetic; Sheep; Thiabendazole; Trichostrongyloidea

Topics: Administration, Oral; Animals; Anthelmintics; Cattle; Cattle Diseases; Dictyocaulus Infections; Levamisole; Morantel; Nematode Infections; Ostertagiasis; Water

The anthelmintic efficacy of morantel tartrate at 5mg/kg bodymass was investigated in three separate controlled trials comprising 68 calves. High anthelmintic activity was established against adult Haemonchus placei, Ostertagia ostertagi, Cooperia spp. (C.pertinata and C. punctata), Bunostomum phlebotomum and Oesophagostomum radiatum.

Topics: Animals; Cattle; Cattle Diseases; Haemonchiasis; Hookworm Infections; Morantel; Nematode Infections; Oesophagostomiasis; Ostertagiasis; Pyrimidines