Persistent efficacy of doramectin and moxidectin against Cooperia oncophora infections in cattle.

Duplicate studies in France and Northern Ireland were carried out to determine the persistent efficacy of topical moxidectin and doramectin against natural infections of Cooperia oncophora. In each study, groups of 15 nematode-naïve calves were treated either with topical doramectin or moxidectin, and put out to graze on pasture contaminated with C. oncophora infective larvae. The persistent efficacy for preventing establishment of infection was assessed by the time to faecal egg excretion of C. oncophora eggs. It was found that the moxidectin treatment prevented infection for less than 10 days and the effect of doramectin lasted for 24 days.

Response of cattle treated with a fenbendazole slow release bolus to challenge from nematodes the following season.

Nematode infection of cattle treated in their first year at pasture with the fenbendazole slow release bolus ('Bolus group') was compared during the second year with that of untreated cattle. Ostertagia was the most prevalent parasite associated with Cooperia. Except for the Dictyocaulus spp. which caused clinical signs of bronchitis in the 'Bolus' group, the infection during the second year resulted in a moderate response of the cattle whatever the group. Rises in both pepsinogen and gastrin levels were correlated with the number of Ostertagia L3 on herbage. Damages in the abomasal mucosa were more frequent and severe in the 'Bolus' group where more inflammatory signs were observed in spite of a smaller number of worms. Nevertheless, the differences in total weight gains were not significant thanks to a compensatory effect during the second part of the grazing season in the 'Bolus' group. Hypotheses related to a minimum threshold of infection during the first year necessary to develop high enough protection during the second year are discussed. The pathological effects of gastrointestinal nematodes seem to vary more according to the inflammatory response than to the number of worms.

Efficacy of moxidectin pour-on against nematode infections in cattle.

Three groups of eight calves, naturally infected with gastrointestinal nematodes and artificially infected with Dictyocaulus viviparus were used to evaluate the efficacy of moxidectin pour-on at dose rates of 0.35 mg/kg and 0.5 mg/kg bodyweight. With both doses the efficacy was 100 per cent against adult D viviparus, Trichostrongylus axei, Ostertagia species and Nematodirus helvetianus. It was more than 99 per cent against Ostertagia and Nematodirus species fourth stage larvae. A small number of Cooperia species were found after treatment, and for this parasite, the efficacy of moxidectin ranged from 97.6 per cent against the larval stages to 98.8 per cent against the adults. No adverse reactions to the moxidectin treatment were observed.

The use of the morantel sustained release bolus under special farm practices (deprime system) in France.

The efficacy of the morantel sustained release bolus in controlling gastrointestinal and lungworm parasites when used in first-season grazing animals which followed older animals onto spring pasture (deprime system) was assessed in three trials conducted in Normandy, France. In each trial first-season grazing calves were equally allocated onto two separate but equivalent paddocks where they remained throughout the grazing season. A morantel sustained release bolus was administered to one group of animals at turnout, the other group remained as controls. The effect of the treatment on contamination of pasture (herbage larval counts and tracer worm counts), on faecal worm egg and lungworm larval counts, and on weight gain performance of the principal animals was assessed. In all three trials, worm egg output in the bolus-treated animals was substantially lower throughout the season compared with the control animals. Worm burdens of tracer calves grazing pastures of the treated cattle were also reduced compared with tracer calves grazing control pastures. Clinical parasitic gastroenteritis occurred in the control animals but not in the bolus-treated animals in one trial. Overall the bolus-treated animals outperformed the controls by a mean weight gain advantage of 10.5 kg (P less than 0.01).

The control of parasitic gastroenteritis of grazing cattle in Normandy, France using the morantel sustained release bolus.

The efficacy of the morantel sustained release bolus in controlling parasitic gastroenteritis in 153 first-season grazing cattle was assessed in three separate field trials conducted in Normandy, France. In each trial, comparisons were made on weight gain performance and parasitology data (faecal worm egg counts, herbage larval counts and- in two of the trials- worm counts from principal animals sacrificed at the end of the grazing season) when bolus treatment was given either at spring turnout or in mid-season in order to determine the optimum time for bolus administration. Cattle were allocated into three groups, each group maintained on a separate but equivalent paddock constructed from the division of a larger pasture. A morantel sustained release bolus was administered to one group of animals at the time of turnout and to a second group of animals in midsummer. The third group of animals in each trial remained nontreated. The effect of the treatment on the contamination of pasture, and parasite levels and weight gain of the principal trial animals was assessed. Similar results were observed in all three trials. Faecal worm egg counts were reduced during the first part of the grazing season in animals receiving the bolus at turnout compared with mid-season treated animals where egg counts followed a pattern similar to the controls until bolus treatment at which time counts abruptly dropped to a low level. Likewise, levels of infective larvae on pastures grazed by control and mid-season treated animals followed similar patterns, increasing to a high level in late summer, while larval levels on pastures grazed by early-season treated animals remained at low levels throughout most of the season. Serum pepsinogen levels, worm counts and weight gain reflected the results from faecal worm egg and herbage larval counts indicating that early-season treatment with the bolus provided the most efficient treatment time for controlling parasitic gastroenteritis throughout the grazing season. The overall mean weight gain advantage of the early-season bolus-treated animals over the controls was 37.2 kg (P less than 0.01) while the advantage of the mid-season treated animals over controls was 13.7 kg.

Comparison between tracer calves and herbage samplings for the assessment of pasture infectivity in trichostrongylosis of cattle.

Two trials were designed in "Haute Normandie" to assess the value of the number of third stage larvae in herbage samples for monitoring the infection of cattle. Two techniques of sampling were used and were compared to the actual infection of tracer calves. An index of infectivity of the pasture was defined: the number of third stage larvae in 1 kg of dry matter of herbage multiplied by the quantity of grass (dry matter) ingested by calves. There was a significant correlation between this index and the actual worm burdens of tracer calves when parasites were numbered by genera, and for herbage samplings done according to "classical" techniques. The correlation is improved when data are combined from samples taken "close to fecal pats" and "far from fecal pats".

Major internal parasites interfering with cattle production in France, and experiments to control them by strategic treatments. A bibliographic review.

A summary of the cattle management systems and statistics in France is presented as a framework to examine the recently published results on the major internal parasites of cattle in France from numeric data on naturally infested animals. From these results the major or constant parasites are Fasciola, Dictyocaulus, Ostertagia and Cooperia; occasional but important parasites are Nematodirus, Neoascaris, Eimeria, OEsophagostomum and Cysticercus bovis. Pathology results focus on disease given by the most common nematode : Ostertagiasis. For prevention and control of infestations in farm practice with typical management procedures, results are presented in dairy cattle (Brittany and Normandy), and in beef cattle (Limousin).