SUMMARYTwo trials designed to examine the effect of a vaccine against coccidiosis were carried out with commercial replacement layers. The effect of vaccination was evaluated by challenging vaccinated and non-vaccinated chickens. In the first trial chickens vaccinated at 14 days of age were compared with non-vaccinated, medicated chickens fed robenidine at 66 ppm throughout and with unmedicated chickens kept in the same house. In the second trial birds were vaccinated at 7 days of age and compared with non-vaccinated birds on a 'Pancoxin' stepdown programme and with chickens maintained coccidia-free by feeding robenidine at 66 ppm throughout.The vaccine was composed of two attenuated strains of E. mivati and E. tenella, and virulent laboratory strains of three or four other species of Eimeria. Resistance of the chickens to E. acervulina, E. brunetii and E. maxima and partial resistance to the other species developed within 3 weeks. In general, immunity increased and was high against all species, although less complete in the case of E. mivati and, when judged by lesion scores, E. tenella.

Small numbers of the nematode species:Spiculopteragia asymmetrica, Apteragia quadrispiculata, Nematodirus filicollis, Capillaria bovis, Cooperia pectinataandOesophagostomum venulosum, were recovered from the gastro-intestinal tracts of wild Fallow deer killed in Essex. In addition, the larval cyst of the cestodeTaenia hydatigenawas found in the liver of one animal.

Five controlled trials were conducted in Germany or in the United Kingdom, using 74 female sheep of merino or Dorset horn breeds, to evaluate the efficacy of an ivermectin controlled-release capsule against naturally acquired or induced infections of gastrointestinal nematodes, lungworms and nasal bot larvae and against incoming infections with gastrointestinal and pulmonary nematodes. Half of the animals were treated with one ivermectin controlled-release capsule that delivered ivermectin at the rate of 1.6 mg per day for 100 days while the other half remained untreated. Parasites were counted 21, 28, 35 or 56 days after administration of the capsule. The treatment was highly effective (> or = 99 per cent) against established parasites of the following species: Haemonchus contortus (adults and fourth-stage larvae), Ostertagia circumcincta, O pinnata, O trifurcata, Ostertagia species fourth-stage larvae, Trichostrongylus axei, T colubriformis, T vitrinus, Cooperia curticei, Nematodirus battus, N filicollis, Strongyloides papillosus, Chabertia ovina, Oesophagostomum venulosum, Trichuris ovis, Tr skrjabini, Dictyocaulus filaria, Protostrongylus rufescens and Oestrus ovis (larvae). The treatment prevented the establishment of the gastrointestinal nematodes H contortus, O circumcincta, T axei, T colubriformis, C curticei, N battus, N filicollis, Ch ovina, Oe vennulosum and the establishment of the lungworm D filaria by > 99 per cent compared with untreated controls (P < or = 0.01).

Four controlled studies, one each in Australia, Germany, the United Kingdom, and the United States, involving 30 calves each were conducted to evaluate the effect of simulated rainfall on the efficacy of Ivomec Pour-On against infections of Cooperia spp. At 3 weeks before treatment the calves were infected orally with third-stage larvae of Cooperia spp. In each study a recent, locally derived field isolate was used. The calves were allocated by restricted randomization based on body weight within sex to one of the following treatments: unmedicated control with no rain, Ivomec Pour-On with no rain, Ivomec Pour-On with rain starting at 40 min before treatment, Ivomec Pour-On with rain starting at 10 min after treatment, and Ivomec Pour-On with rain starting at 60 min after treatment. Ivomec Pour-On was applied topically at a dose rate of 1 ml/10 kg body weight (500 microg ivermectin/kg body weight). The simulated rainfall was equivalent to a heavy shower of approximately 12.5 mm of water during a 30-min period. The calves were necropsied for worm counting at 14 or 15 days after treatment. An evaluation of the pooled data showed that as compared with the untreated controls, the Ivomec Pour-On-treated calves with no rain had significantly (P < 0.01) fewer C. oncophora (> 99%), C. punctata (> 99%), C. surnabada (> 98%), and combined Cooperia spp. (> 99%). The reduction in Cooperia numbers noted for calves exposed to simulated rainfall was > 96% for all Cooperia species, regardless of when the rainfall started relative to the application of Ivomec Pour-On. There was no significant (P > 0.1) difference between the Ivomec Pour-On-treated calves with no rain and the pooled groups with simulated rainfall or between the group with rain before treatment and the pooled groups with rain after treatment. Ivomec Pour-On was highly effective against established infections of Cooperia spp. when applied to wet animals or to animals becoming wet shortly after treatment.

The effect of arpinocid (9-[2-chloro-6-fluorophenyl)methyl]-9H-purin-6-amine) on artificial and natural coccidial infections in broiler chickens was evaluated in a series of pen trials conducted in England, France, and Germany. In trials with induced infections, mortality attributable to coccidiosis did not occur at 50, 60, and 70 ppm although it ranged from 3.2 to 9% in unmedicated groups. At 7 to 8 weeks of age, birds receiving arprinocoid in feed at levels of 40, 50, 60, and 70 ppm had improved body weights and feed conversion compared with unmedicated birds, the differences being significant (P is less than .05) in 4 out of 5 trials. Productivity of birds on arprinocid was equivalent or significantly superior (P is less than 0.5) to those on halofuginone (3 ppm), monensin (100 ppm), nicarbazin (125 ppm), and PANCOXIN (165 ppm). Based on the results of these pen trials, arprinocid at levels of 50 to 70 ppm in feed is a highly efficacious compound for the prophylaxis of coccidiosis, preventing mortality, and permitting good growth and feed conversion under conditions of both mild and severe infection pressure.