Parasitism (Trichostrongylus colubriformis and Eimeria ninakohlyakimovae) in sheep: relationship between wool fiber diameter changes and feed conversion efficiency

Twenty-five lambs, 5 months of age, were used to compare the infection pressure of Trichostrongylus colubriformis with that of Eimeria ninakohlyakimovae. Effects of the parasitic infection pressure were assayed by determining body weight gains, feed conversion efficiencies, and wool fiber diameter changes (reflecting changes in protein metabolism) in lambs fed a good ration and those given a marginal diet (dehydrated alfalfa pellets). Significant differences in weight grains or feed conversion efficiencies of nematode- or coccidia-infected lambs and noninfected controls were not found, but significant differences due to the parasites' effect on wool fiber diameters and in lamb response to different feeds were found. Protein uptake or assimilation, or both, were apparently affected by a combination of infection with E ninakohlyakimovae and a marginal diet.

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.

The effect of route of administration on the anthelmintic efficacy of benzimidazole anthelmintics in sheep infected with strains of Haemonchus contortus and Trichostrongylus colubriformis resistant or susceptible to thiabendazole

Observations of erratic anthelmintic activity of fenbendazole against known standardised thiabendazole-resistant strains of Haemonchus contortus and Trichostrongylus colubriformis in sheep were investigated. Fenbendazole at a dose rate of 10 mg/kg body weight was administered by oral, intra-ruminal or intra-abomasal routes, and was most effective against both resistant strains following intra-ruminal administration. In addition thiabendazole, oxibendazole, fenbendazole, parbendazole and mebendazole plus two unrelated compounds, levamisole and morantel tartrate, were used at one and a half times their suggested or recommended therapeutic dose rate against thiabendazole-resistant strains of H contortus and T colubriformis in sheep; each drug being administered by the intra-ruminal or intra-abomasal routes. Fenbendazole was more effective against both strains following intra-ruminal administration. Parbendazole was more effective against the resistant strain of T colubriformis following intra-ruminal administration. At the dose rate chosen for the other benzimidazoles used against these resistant strains, there was no difference in anthelmintic efficacy due to route of administration. Levamisole was highly effective against both resistant strains, irrespective of the route of administration. In the groups treated with morantel tartrate, the results obtained were difficult to interpret due to mortalities and a highly variable response in the surviving sheep. Fenbendazole, thiabendazole and mebendazole when used at their suggested or recommended therapeutic dose rate in sheep, were highly effective against known thiabendazole-susceptible strains of H contortus and T colubriformis following both intra-ruminal or intra-abomasal administration.

Parasitism and calfhood diseases

That animals can and do acquire an effective immunity against helminth parasites has been demonstrated extensively experimentally, and the fact that domestic animals such as cattle, sheep, and horses become adults while maintaining good health in spite of constant exposure to reinfection long has suggested that immunity must be important to such survival. Although our attempts to date to vaccinate calves against helminth parasites have either failed or been unsatisfactory because of the pathosis induced by the experimental vaccines, the results are not surprising or discouraging. In contrast to the long history of immunization research on bacterial and viral diseases, only within a relatively short time have serious efforts been directed at exploiting hostal immunity for prevention and control of helminthic diseases. Unlike the comparatively simple structures of viruses and bacteria, helminths are complex multicellular animals with vast arrays of antigens and complicated physiological and immunological interactions with their hosts. Much more fundamental information on helminth-bovine interactions, on helminth antigens, and on cattle antibody systems must be developed before progress on control of cattle helminths by vaccination can be meaningful.

[Cooperia curticei Giles, 1892 (nematoda: trichostrongylidae) parasite of goats (capra hircus) in the State of São Paulo, Brazil (author's transl)]

Cooperia curticei Giles, 1892 (Nematoda: Trichostrongylidae) is reported, for the first time, parasitizing the small intestine of goats (Capra hircus) in the State of São Paulo, Brazil. The animals came from the Region of the Alta Araraquarense. The spicules of the worms were well chitinized and measured, on the average, 153,68 micrometer with a standard error of 0,91 micrometer.

Live mass gains and wool production of merino sheep: three treatment programmes for parasite control

A trial is described comparing the live mass gains and wool production of three groups of Merino sheep treated either at four-weekly intervals, strategically or not at all for the control of helminths and Oestrus ovis during a 19 month period. The group treated at four-weekly intervals had the greatest gain in masass was not greater than that of the group treated strategically. At both shearings the four-weekly treated group produced more wool than did the strategically treated group. The latter group produced more wool in total than did the untreated group. The seasonal incidence of nematodes, cestodes and Oestrus ovis on the trial farm was determined by the slaughter of tracer lambs at regular intervals.

Subclinical trichostrongylosis in growing lambs produced by continuous larval dosing. The effect on performance and certain plasma constituents

Three groups of eight-four-month-old worm-free lambs were used to investigate the effect of Trichostrongylus colubriformis infection on growth rate, food intake, and concentration of plasma constituents. Groups ALC and ALI were fed ad libitum, the latter being dosed daily with 2500 infective larvae for 14 weeks. Lambs in group PF were paired to individuals in group ALI and offered the same quantity of food as the infected pair consumed. Hypophosphataemia and hypoalbuminaemia developed in ALI at week 3 and hyperglobulinaemia was present from week 6. There was no significant difference in plasma calcium, protein, urea or glucose concentration between the three groups at any stage. No clinical signs of parasitism were seen in seven of eight ALI lambs and egg counts were generally less than 2000 epg. Worm burdens of 1500-82,900 were found at slaughter. Group weight gain was only 50 per cent of PF lambs which received the same digestible energy intake. Group ALI consumed 15-5 kg dry matter per kg gain in bodyweight compared with 8-6 kg/kg and 9-8 kg/kg for ALC and PF respectively. The infections resulted in extensive villous atrophy and flattening of the intestinal mucosa. Bone growth was arrested and osteoporosis present in five group ALI lambs. The possible use of plasma constituents, particularly phosphorus, as aids for the diagnosis of the early stages of trichostrongylosis in the field is assessed.

The anthelmintic efficacy of fenbendazole against thiabendazole-resistant strains of Haemonchus contortus and Trichostrongylus colubriformis in sheep

The anthelmintic efficacy of fenbendazole (methyl 5-(phenylthio)-2-benzimidazole carbamate) was tested in sheep against standardised strains of Hcaemonchus contortus and Trichostrongylus colubriformis, known to be resistant to thiabendazole (LD90 for thiabendazole against H ontortus was 200 mg/kg bodyweight and against T colubriformis was 150 mg/kg). Fenbendazole at dose rates of 5, 10 and 20 mg/kg per os reduced total worm counts in H contortus infected sheep by 66, 90 and 100 per cent respectively, with similar reductions recorded for worm egg outputs. For the thiabendazole resistant strain of T colubriformis, fenbendazole reduced total worm counts in infected sheep by 4, 44 (40-48), 79 (75-83), 96 and 100 per cent at dose rates of 5, 10, 20, 40 and 80 mg/kg per os. Significant suppression of worm-egg production by thiabendazole resistant T colubriformis was obtained with fenbendazole at dose levels of 5 mg/kg and above. The implications of these results are discussed in the light of the increasing occurrence of strains of trichostrongylid nematodes resistant to currently available benzimidazole anthelmintics.

The common diarrhoeas of sheep in Britain

As every sheep farmer knows, diarrhoea is of common occurrence in animals of all ages in his flock. In lambs it can result in sigificant mortality while in older animals growth rates are reduced and weight loss can occur. Although diarrhoea can be an incidental finding in many sheep diseases, particularly in their terminal stages, only on those conditions are commented on in which diarrhoea is the predominant feature of the clinical syndrome. The subject is discussed below on both an age and seasonal basis and, if an initial assumption is made that lambing takes place at the traditional March/April period, animals will be increasing in age as the seasons progress. Thus the sequence commences in the spring with the young lamb and concludes the following winter with the adult.

[Investigations concerning bovine gastro-intestinal strongyles. II. Seasonal variations in the herbage infestation with infective larvae (author's transl)]

Ecological studies of bovine gastro-intestinal trichostrongylide larvae have been carried on during a three-year period (1972-1974). The studies mainly included pastures grazed by heifers (2nd time grazing cattle). Examination of the herbage samples was based on washing and filtration (sieve mesh-size 36 and 28 mu) followed by Baermann test on the debris. The pasture infestation with infective larvae (L3) followed a nearly stereotype seasonal pattern (cf. fig. 2 and fig. 3): A considerable larval population survived on the pasture during the winter, the infestation decreased strongly during April-May, was low during June and beginning of July, and increased from the middle of July to reach a peak in September-October. The infestation was usually much higher just around the faecal pats than in the rest of the pasture area (cf. fig. 3). The observed populations of trichostrongylide larvae were dominated by Ostertagia (ostertagi), but included other species as well, e.g. Cooperia (oncophora), Nematodirus spp., etc.

Present status of trichostrongyliasis in Iran

Infection with species of Trichostrongylus is common among man and animals in most parts of Iran, and human infections with T. orientalis, T. colubriformis, T. vitrinus, T. axei, T. capricola, T. probolurus, T. skrjabini, and a possibly new, unnamed species have been reported. All are found in Isfahan, central Iran, where the overall prevalence is 67% and the predominant species are T. orientalis and T. colubriformis. Among 737 nomads migrating from the central parts to the south, 86% were found to be infected with one or more of five species (in order of frequency): T. colubriformis, T. orientalis, T. axei, T. capricola, and T. vitrinus. In Khuzestan, southwest Iran, human infections with T. orientalis, T. colubriformis, T. axei, and T. vitrinus with an overall prevalence of 71% have been reported. In the northern parts, along the Caspian Sea, the rate is 7% and the species found, in order of frequency, are T. colubriformis, T. axei, T. vitrinus, and T. orientalis. Trichostrongylus infections are also found in the northwest but are rarely seen in the northeast. In most areas females are more frequently and more heavily infected than are males. All species found in man, except the new, unnamed species, are also found in sheep, goats, cattle, and camels; the number of species found and the order of their frequency differ in various animals and in different areas. Infection in other mammals, such as hares (T. retortaeformis and T. orientalis) and porcupines (T. orientalis), has also been reported.

Relationship of pasture rotation to acquisition of gastrointestinal nematodes by sheep

In a study of the relationship between pasture rotation in Illinois and acquisition of nematodes (mostly Haemonchus contortus) and body weight gains by lambs grazing with their ewes, 2 pasture rotation systems were tested. (1) Lambs and ewes were rotated through a series of 12 alfalfa-bromegrass-lespedeza pastures, each pasture being grazed for 3 to 4 days and rested for 5.5 weeks; 4 complete rotations were done during a 168-day grazing season. (2) Lambs and ewes were moved every 2 days, and 3 complete rotations of 50, 42, and 54 days, respectively, were done during the 146-day grazing season. The lambs under rotation had more nematodes and gained less weight than nonrotated control lambs, although rotation increased the amount of pasturage. Rotation is not recommended to control nematode parasitism of sheep in Illinois.

Efficacy of Fenbendazole against gastrointestinal parasites of sheep

Lambs severely parasitized by Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Oesophagostomum, and Nematodirus were treated with fenbendazole (methyl 5-(phenylthio)-2-benzimidazolecarbamate) given at 3 dose levels: 3.5, 5.0, and 7.5 mg/kg of body weight. Efficacies against these genera, except Haemonchus and Nematodirus, were 100% at the 3 dose levels. Efficacies for the 3 doses against Haemonchus were 93.4, 95.3, and 99.8%, respectively, and against Nematodirus, 99.5, 99.6, and 100%. Efficacies for the doses against Trichuris were 69.1, 83.6, and 98.2%. Toxicosis due to the durg was not seen in these lambs, although they were severely debilitated.

The effect of mixed grazing of sheep and cattle on worm burdens in lambs

Lambs from ewes grazed without cattle at 4.9, 7.4 and 9.9 ewes and lambs per hectare and from ewes run with steers at an equivalent median stocking rate at four ratios in which sheep comprised 30%, 40%, 50% and 70% of the animal equivalents were killed and examined for worms. When sheep grazed alone, there was no significant increase in the number of worm species normally found in sheep, namely Ostertagia circumcincta and Nematodirus spathiger, with an increase in stocking rate. When sheep grazed with cattle, there was a decrease in the number of worm species normally found in sheep but an increase in the number of those normally found in cattle, namely Cooperia oncophora and Trichostrongylus axei, as the proportion of cattle in the ratio increased. The total worm burdens were low due to the management of the flock and parasites were not shown to have affected productivity. The results are discussed and the practical aspects of the findings are presented.

The anthelmintic efficacy of fenbendazole against a mixed nematode infection in sheep

Fenbendazole (methyl-5-(phenylthio)-2-benzimidazole carbamate) at dose rates of 5 mg/kg and above was 100 per cent effective in eliminating a naturally acquired Dictyocaulus filaria infection in sheep. The drug was 100 per cent effective in eliminating concurrent infections of adult Trichostrongylus axei, Haemonchus contortus, Haemonchus placei, Ostertagia circumcincta, Ostertagia ostertagii, Cooperia oncophora, Cooperia mcmasterii, Nematodirus spathiger, Neumatodirus filcollis, Oesophagostomum venulosum and Chabertia ovina. Fenbendazole was 93 per cent and 97 per cent effective at doses of 5 and 10 mg/kg respectively in removing infection with adult T colubriformis, and post-treatment worm-egg production was completely suppressed in surviving female worms. No adverse side-effects were observed in treated sheep at either of the two dose rates used.