Efficacy of the morantel sustained release trilaminate matrix against gastrointestinal nematodes in beef calves

New oral anthelmintic intraruminal delivery device for cattle

BACKGROUND

The purpose of this work was to develop a new oral drug delivery system intended for cattle and that enables delayed and pulsed release of an anthelmintic agent.

MATERIALS

This new tailored dosage form, also called reticulo-rumen device (RRD) has been evaluated on grazing calves by means of measurements of milliunits of tyrosine concentration, number of eggs per gram of feces, mean number of infective larvae on cattle pasture and increase in mean weight of cattle.

METHODS

The in vivo evaluation was carried out during two grazing seasons on different groups of dairy cattle. During the first grazing season, Group 1 was designated as an untreated control group. The remaining two were assigned to different treatments as follows: Group 2, early season suppression with a marketed intraruminal slow release bolus (Chronomintic(®), Virbac) administered immediately prior to turn-out and Group 3, mid-season suppression with a new RRD administered immediately prior to turn out. When the cattle were turned out at the start of the second grazing season, they were not given any anthelmintic treatment and were divided into two different groups, corresponding to the previous groups that received an anthelmintic treatment during the first grazing season, on that pasture that they had occupied as separate groups in the previous year. Furthermore, during the second season, samples of feces, blood and herbage were collected every month.

RESULTS AND CONCLUSION

During the first grazing season, the results indicated that the fecal egg counts and the number of infective larvae in herbage samples were slightly lower for the group receiving the new RRDs. Regular weighing of the cattle receiving the new RRDs revealed no significant difference with cattle receiving marketed RRDs. Conversely, during the second grazing season, the results for the mean weights of the cattle demonstrated that the weights of animals having been administered new RRDs during the first grazing season were significantly different (P < 0.05) from those in the second group treated with a Chronomintic(®) during the first grazing season. A difference in mean weight of 26 kg was observed between these two groups.

Treatment of external and internal parasites of cattle

To control parasitic disease in cattle, one first has to determine what parasites he or she is trying to control--nuisance and biting flies in a milking parlor or ticks on range cattle? The determination may be based on geographic location, class of cattle, and their management. After determining what is there, then if the numbers are sufficient, justify treatment. Each livestock producer has a different array of parasites with which to deal, and in some circumstances, parasitic disease is below the economic threshold. Others may have occasional clinical disease associated with parasites, but most have situations in which the potential of economic loss is high enough to justify control.

Efficacy of morantel sustained release trilaminate bolus against gastrointestinal nematodes in grazing dairy calves in Kenya

The efficacy of morantel sustained release trilaminate (MSRT) bolus against gastrointestinal nematodes was evaluated under field conditions over a 10-month period. Twenty weaner calves were randomly divided into 2 groups of 10 calves each and grazed from March to December on adjacent, similarly contaminated paddocks. Group 1 calves (T-1) served as untreated controls while group 2 calves (T-2) were dosed at turnout with MSRT bolus designed to release morantel tartrate continuously for 90 days. The efficacy of MSRT was assessed by comparison of parasitological data (faecal worm egg counts, herbage larval counts, worm counts from tracer calves and set-stocked trial calves, determination of haematological parameters and pepsinogen levels), weight gains and clinical status of the animals. Faecal egg counts from the treated group (T-2) were reduced by 100% (P < 0.001) following treatment and remained significantly (P < 0.05) lower than counts from T-1 calves up to trial termination. The use of MSRT bolus resulted in a reduction of 92% (P < 0.001) in the number of gastrointestinal nematodes in set-stocked calves at the end of the study and a 55 to 85.7% reduction in herbage larval infectivity as reflected in lowered parasite burdens in tracer calves. At the trial termination, the control calves had gained on average (+/- s.d.) 59.4 +/- 4.8 kg (200.0 +/- 7.4 g day-1) and the treated ones on an average 128.6 +/- 10.5 kg (530.0 +/- 13.1 g day-1).

Gastrointestinal nematode infections of first-season grazing calves in Belgium: general patterns and the effect of chemoprophylaxis

Comparative analyses of the patterns of gastrointestinal nematode infections of first-grazing season cattle in Belgium are presented. The analysis involves 17 studies covering a 10 year period on 13 different farms in Flanders, Belgium. In all studies the calves were divided into an untreated control group, and one or two groups treated with chemoprophylactic systems. Two general infection levels emerged-'sub-clinical' (14 studies) and 'clinical' (three studies). The 'sub-clinical' infections were characterised by no clinical signs of parasitic gastroenteritis in the untreated control groups. Mean faecal egg counts remained low (less than 200), maximum pepsinogen levels only reached about 3500 mU tyrosine, and very small reductions in overall daily weight gain were observed compared with calves given chemoprophylaxis (less than 40 g day-1). Based on these results, on these 'sub-clinical' farms, chemoprophylaxis may not have been needed. In contrast, multiple salvage treatments of the control calf groups were required in the 'clinical' infections. Even with these salvage treatments mean faecal egg counts were high (more than 300), maximum pepsinogen levels were over 5500 mU tyrosine and there was a very large reduction in overall daily weight gain (more than 300 g day-1). However, it was not possible to predict either at turnout, or during the first month afterwards whether an infection on a particular farm would develop into a 'clinical' infestation. With the present data this prediction was possible from 8 weeks (Day 56) onwards, based on faecal egg counts and pasture larval contamination. It was also possible to predict using serum pepsinogen levels on Day 84. Therefore, one possible strategy for the effective control of gastrointestinal nematode infections of calves in temperate regions would be to evaluate faecal egg counts 2 months after turnout, and then only start treatment (i.e. metaphylaxis) if required.

A comparison of early and mid grazing season suppressive anthelmintic treatments for first year grazing calves and their effects on natural and experimental infection during the second year

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.

Epidemiology of Ostertagia in the Northwestern USA

The two most significant environmental factors that influence the epidemiology of Ostertagia are temperature and moisture. These factors vary more in the west and northwest than in any other part of the USA because of extreme regional differences in climate, topography, and land use. Consequently, patterns of Ostertagia transmission and inhibition also vary widely from region to region and from year to year. Recent data require revisions of previously accepted concepts of northern/southern transmission and inhibition. In particular, the flaw of liberal extrapolation of information from one region to another has now been recognized. Inhibition may not occur along the coast of the Pacific Northwest. Although not completely delineated, the transition zone between northern and southern patterns of inhibition appears to be significantly wider and more variable than previously recognized; Oregon data suggest a possible indeterminate and variable band extending north of the 45th parallel and south of the 43rd parallel. Summer inhibition has now been documented in areas of Oregon and Montana. Other than the recent Oregon and Montana studies, data on this transition zone in the Rocky Mountain region and high plains are sparse to non-existent. In contrast to previously accepted doctrine, the fall rise in egg count generally exceeds the traditionally accepted spring rise in many areas. From the Pacific Northwest to the Midwest, year-round transmission patterns have been observed. The presence of geothermal ground water sources produces microclimates that favor larval survival in many areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of the morantel sustained release trilaminate bolus against gastrointestinal nematodes and its influence on immunity in calves

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.

The epizootiology of gastrointestinal nematodes of cattle in selected areas of Oregon

A study was initiated to (1) determine species of gastrointestinal nematodes present in cattle in selected areas of Oregon, (2) examine seasonal abundance of these nematodes as an indicator of periods of transmission, and (3) determine when developmental inhibition occurs in the major genera of nematodes encountered. Four study sites were chosen: Corvallis, Langlois, near Fort Rock, and southeast of Klamath Falls on the Oregon-California border. Eight sets of three to four tracer calves each were introduced onto pasture at each site over a 2 year period with time of turn out onto pasture corresponding to late spring, mid-summer, late fall and late winter. At Corvallis, a distinct seasonality in parasite transmission was evident, peaking during the fall and winter. At Langlois, transmission was fairly constant throughout the year. No discernible patterns were evident at either Klamath Falls or Fort Rock. Eight nematode genera were found during the study. Ostertagia, Cooperia, Nematodirus and Trichostrongylus were present at all study sites and were the most common genera at each. Trichuris was found at all sites except Klamath Falls. Oesophagostomum was present in tracers only from Langlois and Corvallis while Haemonchus was found only at Klamath Falls and Fort Rock. Capillaria was only present at Klamath Falls. Where possible, specific transmission patterns for Nematodirus, Cooperia, and Ostertagia were determined for each site. Nematodirus was transmitted fairly steadily at both Langlois and Corvallis but was quite variable at Fort Rock. Developmental arrest was detected in this genus at all study sites during the fall and/or winter. Cooperia exhibited the most seasonally defined pattern of transmission, peaking during the fall and winter at Langlois, Corvallis and Klamath Falls. Hypobiotic larvae of Cooperia were present during the fall and/or winter only at Langlois and Corvallis. Peak transmission of Ostertagia at Langlois and Corvallis occurred during the fall and winter. At Fort Rock, transmission was lowest in the fall and increased in the winter. Hypobiotic larvae were evident in the fall and winter at Corvallis, Fort Rock and Klamath Falls. These data suggest Type II ostertagiasis may occur in late winter through spring in these areas. Hypobiotic larvae of Ostertagia were not detected at Langlois. The lack of appropriate environmental stimuli is one possible explanation for the apparent lack of hypobiosis at that site.