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.

Observations on the epidemiology and control of Strongylus vulgaris infections.

The epidemiology and control of helminth infections in the horse were studied in four small grazing experiments between 1981 and 1984 at the University of Utrecht. At autopsy in November or December negligible Strongylus vulgaris burdens were found in the cranial mesenteric artery of four groups of ponies, which had been treated with an anthelmintic in July and subsequently transferred to a clean pasture. Considerable arterial S. vulgaris burdens were seen in three groups of ponies which were treated with an anthelmintic in July without a move to clean pasture, and in another group of ponies in 1984, which was set stocked on a pasture used for horses in 1983 and which was treated with an anthelmintic (albendazole) 2 days before turnout in April and subsequently in May, June and July. A tracer pony, grazed with this group between the middle of September and the middle of November, harboured an even higher burden of arterial S. vulgaris larvae. The arterial S. vulgaris in the latter group could not be the result of contamination of the pasture with S. vulgaris eggs before July, as in the three other groups with considerable arterial S. vulgaris burdens. Pasture larval counts showed that S. vulgaris larvae do not only overwinter, but are able to survive in considerable numbers until autumn, longer than most other gastrointestinal nematodes. There were some indications that translation of infective larvae, which overwintered on pasture in some free living stage, occurred between May and July.

Alternate grazing of horses and sheep as control for gastro-intestinal helminthiasis in horses.

Gastro-intestinal helminth infections of a group of three yearling mare Shetland ponies, which were set-stocked on a small pasture from February until September, were compared with those of a similar group of ponies, which grazed a similar pasture from February to July and subsequently was removed to a pasture which had been grazed by sheep from April to July. In addition both groups were treated with cambendazole when the latter group was removed to the sheep pasture. Pasture larval counts and worm counts demonstrated that the group grazed after the sheep acquired considerably smaller burdens of nematodes of the subfamilies Cyathostominae and Strongylinae, but considerably higher burdens of Trichostrongylus axei than the group which remained on the same pasture. The T. axei infections in the former group caused an increase in the serum pepsinogen levels within two weeks after removal to the sheep pasture followed by a gradual decrease. At necropsy T. axei populations consisted almost exclusively of inhibited early third stage larvae.

[Observations on the effect of some measures for preventing gastrointestinal helminth infections in sheep]. / Waarnemingen over het effect van enkele maatregelen ter preventie van maagdarmworm infecties bij het schaap.

Prophylactic anthelmintic treatment of ewes about parturition has only a negligible effects on the most important species of helminths when the ewes and their lambs are not grazed on clean pasture. Haemonchus contortus infections were completely prevented in some cases but usually severe infections occurred. As the build-up of these heavy infections in lambs was slightly delayed in comparison with that in the lambs of untreated ewes, treatment about parturition should still be regarded as useful. Treatment of lambs at the time of weaning combined with moving the animals to a clean pasture is a useful though not entirely effective preventive measure. Particularly when the lambs continue to stay on the farm, they have to be moved to clean pasture and/or treated with anthelmintics more frequently.

Prevalence of antibodies to equine viruses in the Netherlands.

The prevalence of antibodies to various viruses was investigated in a series of serum samples collected from horses in the Netherlands between 1963 and 1966 and from 1972 onwards. Neutralizing antibodies to equine rhinopneumonitis virus, equine arteritis virus and to equine rhinovirus types 1 and 2 were detected in respectively 76%, 14%, 66% and 59% of the equine serum samples tested. The observed incidence of serum samples positive to equine adenovirus in the complement fixation test was 39%. Precipitating antibodies to equine infectious anaemia virus were detected only in serum samples from two horses imported from abroad. Haemagglutination inhibiting antibodies to Myxovirus influenzae A/equi-1, M. Influenzae A/equi-2, and Reovirus types 1, 2, and 3 were present in respectively 82%, 50%, 10%, 33% and 3.6% of the serum samples tested. The most frequently observed incidence of antibodies to the various equine respiratory viruses occurred in the groups of horses having repeatedly contact with other horses.

Prevalence of antibodies to equine viruses in the Netherlands.

Summary The prevalence of antibodies to various viruses was investigated in a series of serum samples collected from horses in the Netherlands between 1963 and 1966 and from 1972 onwards. Neutralizing antibodies to equine rhinopneumonitis virus, equine arteritis virus and to equine rhinovirus types 1 and 2 were detected in respectively 76%, 14%, 66% and 59% of the equine serum samples tested. The observed incidence of serum samples positive to equine adenovirus in the complement fixation test was 39%. Precipitating antibodies to equine infectious anaemia virus were detected only in serum samples from two horses imported from abroad. Haemagglutination inhibiting antibodies to Myxovirus influenzae A / equi-1, M. Influenzae A / equi-2, and Reovirus types 1, 2, and 3 were present in respectively 82%, 50%, 10%, 33% and 3.6% of the serum samples tested. The most frequently observed incidence of antibodies to the various equine respiratory viruses occurred in the groups of horses having repeatedly contact with other horses.