An economic and efficacy comparison between morantel (when administered from an intraruminal bolus) and conventional anthelmintic treatment in grazing cattle

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).

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) second edition of guidelines for evaluating the efficacy of anthelmintics in ruminants (bovine, ovine, caprine)

The first edition of the W.A.A.V.P. anthelmintic guidelines for ruminants was published in 1982. Since then improved parasitological procedures have been developed, new therapeutic and prophylactic products have appeared requiring different test methods, and registration authorities are requesting more detailed record keeping and data validation. This second edition addresses these developments and fulfills the original goal of publishing guidelines for high quality, scientifically valid testing standards for trials that would be accepted as proof of efficacy by registration authorities regardless of country of origin. This second edition includes updated guidance on standard parasitological procedures, dose titration, dose confirmation and clinical trials, and provides guidelines for evaluating products for efficacy against anthelmintic resistant parasites, persistence of activity and prophylactic activity. Tests for efficacy against nematodes, trematodes and cestodes are included.

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

The effectiveness of the morantel sustained release trilaminate (MSRT) in controlling gastrointestinal nematodes through a grazing season was evaluated using 60 yearling beef stocker calves randomly divided into 2 groups of 30 animals each. In April 1985, the calves comprising the treatment group each received an MSRT designed to release morantel tartrate continuously for 90 days while those of the control group remained unmedicated. All animals were weighed and samples of rectal feces were taken at 14-day intervals, beginning on Day 0, until trial termination (Day 168). At trial termination, 10 control and 10 treated calves were necropsied for recovery of gastrointestinal nematodes. Three sets of parasite-naïve tracer calves were utilized to evaluate the initial, interim and final levels of pasture contamination by nematode larvae. Overall, the use of the MSRT resulted in a 75.5% reduction (P less than 0.001) in output of nematode eggs from the principals, an 81.8% reduction (P less than 0.001) in numbers of gastrointestinal nematodes in principals (at trial termination), and a 96.9% reduction (P less than 0.05) of pasture larval nematode contamination (as indirectly indicated by parasite burdens in tracer calves). The mean weight advantage of treated calves was 16.6 kg per head (P less than 0.001).

The prophylactic effect of ivermectin treatments on gastrointestinal helminthiasis of calves turned out early on pasture or late on mown pasture

A study was undertaken to ascertain the prophylactic effect on gastrointestinal helminthiasis of (1) a single ivermectin treatment of calves 3 weeks after a late turnout on mown pasture and (2) two ivermectin treatments of calves 3 and 8 weeks after an early turnout. The single ivermectin treatment after a late turnout on mown pasture appeared to be an effective control measure for infections of Cooperia and, in particular, Ostertagia. The two treatments after an early turnout were also effective, although less so than the single treatment combined with the late turnout on mown pasture. Ivermectin treatment had no effect on the faecal egg output or the pasture larval counts of Nematodirus helvetianus. The proportion of inhibited early fourth stage larvae of Ostertagia was much higher in the control group than in either of the experimental groups.

The prophylactic effect of ivermectin treatment of calves, three weeks after turnout, on gastro-intestinal helminthiasis

In two grazing experiments carried out in 1982 and 1983 the prophylactic effect on gastro-intestinal helminthiasis of a single ivermectin treatment of calves 3 weeks after turnout was studied in animals which were turned out early on contaminated pasture and in calves which were turned out late on mown pasture. A single ivermectin treatment 3 weeks after early turnout did not prevent heavy helminth infections. However, such single treatment of calves 3 weeks after a late turnout on mown pasture appears to be a promising way of preventing heavy infections. Late turnout on mown pasture without anthelmintic treatment was not enough to prevent heavy infections. Ivermectin treatment was more effective against Ostertagia spp. than against Cooperia spp. There was no effect on the faecal egg output of Nematodirus helvetianus. Predominantly due to the dry summer, infections were lighter in 1983 than in 1982. These lower infections, and possibly also a delay in the onset of inhibition and differences in helminth strains, may explain the lower proportion of inhibited development in Ostertagia spp. in 1983 than in the comparable groups in 1982.

New methods of drug application for control of helminths

Several new ways have been developed of delivering anthelmintics to ruminants aimed particularly at reducing labour. For single doses, these include a semi-automatic rumen injector for giving insoluble drugs to cattle more conveniently and efficiently than by oral dosing, and the dermal application of levamisole which is, however, subject to seasonal variation in absorption. Sustained administration offers potentially a high level of preventive control but carries a greater risk of developing drug resistance. Even with the best available methods of group administration in feed supplements or drinking water, there remains some uncontrollable variation in individual intake. Intraruminal sustained release devices largely overcome this problem and constitute the most important new technology. They are represented at present by the commercially successful morantel sustained release bolus, and the more versatile Laby capsule which is under development for anthelmintic delivery. Other new applications include the possible development of synergists, potentiators and drug combinations, the special features of drugs which bind strongly to plasma proteins, and the new possibilities offered by a drug highly effective against all stages of Fasciola hepatica. In the general approach to anthelmintic application in helminth control, there have been advances in knowledge of helminth population biology which can lead to better timing of strategic dosing programs, which show that single treatments can have persistent benefits without a simultaneous reduction in infection rate, and which question the conventional view that control schemes require the treatment of all animals in the group.