Efficacy of ivermectin and levamisole against immature Dictyocaulus viviparus in cattle

Eighteen calves aged approximately three months were each infected with Dictyocaulus viviparus larvae at a rate of 30/kg bodyweight. Seven days later they were randomly allocated to three groups of six animals. Calves of group 1 were controls. Calves of group 2 were given levamisole at a dose rate of 10 mg/kg and calves of group 3 were given ivermectin at a dose rate of 200 micrograms/kg. The anthelmintic activity of these two drugs was compared using clinical, functional, parasitological and pathological parameters. The results showed that the efficacy of ivermectin, given at a therapeutic dose, against immature D viviparus was higher than that of levamisole, given at double the recommended dose.     

Anthelmintic activities of ivermectin against immature and adult Dictyocaulus viviparus

Eighteen calves about 3 months old were inoculated with 3,000 Dictyocaulus viviparus infective larvae. Three groups of 6 calves each were formed. Thirteen days after inoculations, 3 of the 6 group 1 control calves were given vehicle subcutaneously (SC) and the group 2 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Thirty-five days after inoculation, the remaining 3 calves in group 1 were given vehicle SC and the group 3 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Necropsies were performed 42 days after inoculations. A total of 474 D viviparus was recovered from the group 1 control calves, whereas none was recovered from the calves treated when the nematodes were in the 4th stage of development (group 2) or adult stage (group 3).     

A comparison of interactions between vaccination against Dictyocaulus viviparus and anthelmintic suppression in immunised and unimmunised yearling cattle

Twenty parasite-naive calves aged approximately four months were divided randomly into four groups of five. Two groups were treated with oral lungworm vaccine. One immunised group plus another non-immunised group were put out to graze on May 1 on a pasture known to be contaminated with Dictyocaulus viviparus infective larvae during the previous autumn. All the calves both indoor and outdoor were treated with ivermectin at three, eight and 13 weeks after the first groups started to graze and again at housing at the end of September. After the winter housing period on April 27 of the following year all the calves were given an artificial challenge of D viviparus infective larvae at the rate of 15 larvae per kg bodyweight, and the clinical and parasitological reactions monitored. All the calves which had been vaccinated or exposed to field infection during year 1 reacted strongly in ELISAs using antigen prepared from fourth stage D viviparus larvae but much less strongly in similar tests using adult derived antigen. Clinically those calves exposed to previous field infections were less severely affected than the housed calves, although parasitologically all three groups with prior exposure to D viviparus appeared to have a similar functional level of immunity to the challenge infection in comparison to the unexposed calves of the same age.     

Persistent anthelmintic activity of ivermectin in cattle

Two studies are described which demonstrate the persistent activity of ivermectin injected subcutaneously into cattle at 200 micrograms/kg in preventing the establishment of induced infections with the gastrointestinal parasites Ostertagia ostertagi and Cooperia oncophora and the lungworm Dictyocaulus viviparus. These results indicated a reduction in mean worm count compared with the control group for O ostertagi of more than 99, 45 and 94 per cent with a seven, 14 or 21 day interval between treatment with ivermectin and the administration of infective larvae, respectively, in trial 1 and more than 99, more than 99 and 99 per cent at seven, 10 or 14 days, respectively, in trial 2. Corresponding values against C oncophora were 99, 0 and 45 per cent at seven, 14 and 21 days in trial 1 and more than 99, 84 and 31 per cent at seven, 10 and 14 days in trial 2. Against D viviparus, reduction in counts were more than 99, 98 and more than 99 per cent at seven, 14 and 21 days, respectively, in trial 1 and 100, 100 and 100 per cent at seven, 10 and 14 days, respectively, in trial 2. The relevance of these results to the build-up of infective larvae on pasture and infection in cattle is discussed.     

Efficacy of levamisole pour-on compared with levamisole subcutaneous injection against Dictyocaulus viviparus infection in calves.

The efficacy of levamisole pour-on against Dictyocaulus viviparus was compared to that of subcutaneous levamisole injection. Eighteen calves were raised individually and artifically infected with D. viviparus larvae. Faecal samples were collected 27 and 28 days later and larvae per gram (l.p.g.) determined. The animals were then divided into three comparable groups. Group 1 animals remained untreated as controls. Group 2 animals received levamisole 10% w/v subcutaneous injection at a dose of 5 mg kg-1 and Group 3 received levamisole pour-on 20% w/v at a rate of 10 mg kg-1 applied transdermally. Results of l.p.g. measurements from faecal samples taken 7 and 8 days post-treatment indicated a dramatic reduction in the worm burden of animals in both treatment groups. Necropsies at 14 days post-treatment revealed few adult worms in these groups, indicating a 99 and 98% kill rate for pouron and subcutaneous injection, respectively.     

Effect of repeated doses of levamisole on grazing cattle infected with Dictyocaulus viviparus

Seventy-one worm-free Friesian calves were allocated by weight to three trial groups (1, 3 and 4) of 18 and a control group (2) of 17 animals. Calves in group 1 were vaccinated with a bovine lungworm oral vaccine on days 0 and 28, and on day 42 all groups were turned out to graze together on pasture known to be infected with Dictyocaulus viviparus larvae. Twenty-eight days after first exposure to infection one control calf died of parasitic bronchitis. Anthelmintic medication consisting of two doses of levamisole (7 . 5 mg/kg) at 14 day intervals was promptly administered to group 3 calves and three doses at the same intervals to group 4 calves. All calves were challenged with 20,000 infective D viviparus larvae on day 147. Calves were weighed every 14 days throughout the trial which ended 42 days after challenge. Pasture contamination and infectivity were monitored by pasture larval counts and tracer calves. Statistically there was no significant difference between the performances of treated and vaccinated groups before challenge but all were significantly superior to the control group. After challenge the productivity of all experimental groups was temporarily depressed but the levamisole treated cattle recovered more rapidly becoming significantly heavier than the vaccinates at the end of the trial. The mean group weight gains over the trial period were 89 . 92, 63 . 87, 88 . 67 and 98 . 70 kg in groups 1, 2, 3 and 4 respectively.     

Prophylactic efficacy of an ivermectin sustained-release bolus against challenge exposure with gastrointestinal and pulmonary nematode infective larvae in calves

Twelve Holstein calves were used to determine the prophylactic efficacy of ivermectin against challenge exposure with gastrointestinal and pulmonary nematodes. Two groups of 6 calves (mean body weight, 205 kg) each were formed by restricted randomization according to body weight. Group-1 calves served as nonmedicated controls. Each calf of group 2 was orally given one prototype sustained-release bolus designed to deliver ivermectin at a continuous daily dose of 8 mg. Third-stage nematode infective larvae were given to the calves on posttreatment days 28 and 42. The calves were euthanatized 77 or 78 days after treatment. Ivermectin was 100% effective (P less than 0.05) in preventing the establishment of infection by Haemonchus placei, Ostertagia ostertagi, Cooperia spp (C punctata, C oncophora, C surnabada), Nematodirus helvetianus, Oesophagostomum radiatum, and Dictyocaulus viviparus and was greater than 99% effective against Trichostrongylus axei. Incidental infection by Trichuris spp was reduced by 94% (P = 0.08).     

Chemoprophylaxis and immunity to parasitic bronchitis in cattle — a field experiment comparing topical ivermectin and an oxfendazole intraruminal device

Seeder calves infected with Dictyocaulus viviparus were used to contaminate a field divided into three similar paddocks. Twenty-four autumn-born calves were allocated to three matched groups; one group was given topical ivermectin treatments (0.5 mg/kg) at 3, 8 and 13 weeks after turnout (Day 0); each member of a second group was given an oxfendazole pulse-release intraruminal device (OPRB) at turnout; while a third group was kept as untreated controls to monitor the natural epidemiological pattern of events. Severe pasteurella pneumonia exacerbated by lungworm infection occurred in the controls after Day 24. Two died and repeated doses of antibiotic and anthelmintic therapy were necessary to save the remainder. Clinical signs were much milder in the ivermectin and OPRB groups and resolved with only a single dose of antibiotic. The OPRB group excreted some lungworm larvae at this time, but none was detected in the faeces of the ivermectin group during the grazing season. At housing, five calves from each group and four lungworm-naive calves were challenged with D. viviparus larvae. The infection became patent in all challenge-control calves, but no larvae were passed by any of the trial animals. Post-mortem worm-counts revealed percentage takes for the challenge controls, trial controls, ivermectin and OPRB groups of 16.7, 0.01, 0.9 and 0.2, respectively. All trial groups had therefore developed a substantial immunity.     

Efficacy of low doses of fenbendazole and its administration via drinking water in the prophylaxis of nematodiasis in grazing calves

Under experimental conditions, fenbendazole given at doses of 0.4 and 1.0 mg/kg body weight suppressed calves' faecal output of Ostertagia and Cooperia species eggs and Dictyocaulus viviparus larvae. Both dose levels were given in the form of small daily drenches and the higher level showed greater efficacy. In a grazing experiment, medication with fenbendazole at 1.0 mg/kg/day administered intermittently to calves using an automatic dose dispenser almost completely suppressed the output of trichostrongylid eggs. As a result, infection on the pasture and in the calves remained at a low level throughout the grazing season. By contrast, control pasture and control calves showed rather heavy infection from mid-August onwards with significantly lower weight gains and widespread signs of parasitic gastroenteritis. At post mortem examination of representative calves from each group in November, the medicated animals had 99 per cent less Ostertagia species, whether adults or larvae arrested at the early fourth stage, and 95 per cent less Cooperia species compared with controls. Medication in the drinking water suppressed the faecal output of D viviparus larvae for most of the grazing season by comparison with the controls but the medicated calves became infected with this parasite towards the end of the season. Until this problem is overcome, precautions against parasitic bronchitis are advised when this system of medication is adopted.     

Patterns of parasitic nematode infection and immunity in dairy heifers treated with ivermectin in a sustained-release bolus formulation either at turnout or in the middle of the grazing season

Twenty-eight Holstein-Friesian heifers, born the previous year and weighing between 130 and 310 kg, were allocated to one of two treatment groups by restricted randomisation, based on their initial weight. The heifers in group 1 were each treated with ivermectin in a sustained-release bolus formulation at turnout in April, and those in group 2 were each given an ivermectin bolus on July 10, 84 days after turnout. On that day the mean geometric worm egg counts of groups 1 and 2 were 0.4/g and 38.8/g, respectively, and they both had a mean plasma pepsinogen concentration of 0.59 iu/litre; in group 1, two of 14 faecal samples were positive for Dictyocaulus viviparus larvae, and in group 2 all 13 samples were positive; in group 1 eight calves were positive and three inconclusive for the presence of antibodies to D viviparus, and in group 2 the corresponding figures were 10 positive and two inconclusive; the mean liveweights of groups 1 and 2 were 274.4 kg and 262.8 kg, respectively. By December 4,231 days after turnout, the corresponding results were: mean geometric worm egg counts of 2.2/g and 0.5/g; one of 13 and none of 14 faecal samples positive for D viviparus larvae; 12 positive and two inconclusive and none positive and 10 inconclusive for the presence of antibodies to D viviparus; 214 days after turnout their mean liveweights were 361.1 kg and 358.3 kg. Although the patterns of parasitic nematode infection were different in the two groups during the grazing season, by the time they were housed both groups had achieved similar liveweights and showed evidence of an immune response to both D viviparus and gastrointestinal nematodes.     

Induction of protective immunity to Dictyocaulus viviparus in calves while under treatment with endectocides

Three groups of five parasite-naive calves were used. The treatments were: (a) Group 1 calves were weighed on Day 0 and injected with doramectin at 200 microg/kg. From Day 1 to 19 they were dosed orally with 2000 infective larvae of Dictyocaulus viviparus. On Day 28 they were again injected with doramectin, and infected with D. viviparus larvae from Days 33 to 41. They were then left untreated until Day 81 when they were infected with 20 infective larvae of D. viviparus per kg body weight. They were killed on Day 110 and lungworms were counted; (b) Group 2 calves were immunised with oral lungworm vaccine on Days 0 and 28, and infected and slaughtered as Group 1 on Days 81 and 110, respectively; (c) Group 3 calves acted as infection controls. Blood samples were taken at Days 0, 21, 49, 77 and 110 for antibody tests to D. viviparus. At autopsy there were no significant differences between the number of lungworms from Groups 1 and 2 (Means 17.4 and 31.3, respectively); Group 1 had significantly less value than Group 3 (Mean 228) (p < 0.05). Increased antibody titres to the larval sheath of the infective larvae were observed from Groups 1 and 2, showing that the larvae in Group 1 had penetrated the intestine before being killed by the circulating anthelmintic. This experiment shows that if calves are exposed to infective larvae while under systemic endectocide cover, an immune reaction is stimulated.     

Efficacy of ivermectin against induced gastrointestinal nematode infections in goats

The efficacy of ivermectin (0.08 per cent w/v oral solution) at different dose levels was evaluated against induced infections of adult Haemonchus contortus (21 days old) and Trichostrongylus colubriformis (21 days old) and fourth stage larvae of Oesophagostomum columbianum (17 days old), Ostertagia circumcincta (five days old) and Strongyloides papillosus (five days old). Twenty-five Boergoats (mutton goats) were randomly allocated by bodyweight within each sex to an untreated control group and four ivermectin treatment groups; ivermectin was administered at either 25, 50, 100 or 200 micrograms/kg orally, once. The goats were killed and processed for worm recovery 25 to 27 days after treatment. At 25 micrograms/kg the efficacy of ivermectin varied from 43 per cent for adult T colubriformis to more than 99 per cent for fourth larval stage O columbianum. Ivermectin at 50 micrograms/kg or higher was 99 per cent or more effective against all induced parasite infections with the exception of ivermectin at 50 micrograms/kg against S papillosus (97 per cent). For all parasites there was a statistically significant (P less than 0.05) difference between the control group and the pooled treated groups. No adverse reactions to ivermectin treatment were observed in the goats.     

Anthelmintic efficacy of albendazole against adult Dictyocaulus viviparus in experimentally infected calves.

Anthelmintic activity of albendazole against adult Dictyocaulus viviparus was evaluated in a controlled experiment. Calves were raised nematode-free to approximately 8 weeks of age and were each given 4,000 infective 3rd-stage larvae. Twenty calves with patent parasitisms were allotted to 2 groups of 10 calves each. Calves in group 1 were used as nonmedicated controls, and calves in group 2 were given albendazole in paste formulation at the dosage concentration of 7.5 mg/kg of body weight on the 30th day after administration of infective larvae. At necropsy, nonmedicated control calves had a total of 308 adult D viviparus, whereas the albendazole-treated calves had 11, for an average efficacy of 96.4%. These reductions were statistically highly significant (P less than 0.01). At necropsy, none of the treated calves was passing 1st-stage C viviparus larvae in their feces, whereas control calves were passing an average of 46 larvae/10 g of feces.     

Persistent efficacy of doramectin injectable against artificially induced infections with Cooperia punctata and Dictyocaulus viviparus in cattle.

Three studies were conducted to evaluate the persistent efficacy of doramectin injectable solution against experimental challenges with infective larvae of Cooperia punctata and Dictyocaulus viviparus. In each study, four groups of ten randomly-assigned calves, negative for trichostrongyle-type eggs on fecal examination, were treated subcutaneously in the midline of the neck with saline (1 ml/50 kg) on Day 0 or doramectin (200 microg/kg = 1 ml/50 kg) on Day 0, 7, or 14. Two additional calves from the same pool of animals were randomly assigned as larval-viability monitors and received no treatment. On Days 14-28, approximately 1000 and 50 infective larvae of Cooperia spp. and D. viviparus, respectively, were administered daily by gavage to each animal in Groups T1-T4. On Day 28, the two larval-viability monitor calves were inoculated in a similar manner with a single dose of approximately 30000 and 2000 larvae of Cooperia spp. and D. viviparus, respectively. Equal numbers of calves from each treatment group were killed on Days 42-45, as well as the two viability monitor animals to enumerate worm numbers. A 2% or 5% aliquot of small intestinal contents and washings were examined for worm quantification and identification, while 100% of the lung recoveries were quantified and identified. For each study and across the three studies, geometric mean worm recoveries for each treatment group were calculated from the natural log transformed data (worm count + 1) and were used to estimate percentage reduction. In the three studies, doramectin injectable solution was 97.5% efficacious against lungworms for up to 28 days and was 99.8% efficacious in reducing infection resulting from challenge with infective larvae of C. punctata for at least 28 days post-treatment.     

Efficacy of a homoeopathic prophylaxis against experimental infection of calves by the bovine lungworm Dictyocaulus viviparus

Two groups of parasite-free calves, one of which had been treated with four doses of a homoeopathic oral vaccine for parasitic bronchitis due to Dictyocaulus viviparus and the other with a placebo, were infected at the rate of 25 infective larvae/kg bodyweight 18 days after the final dose. Both groups became severely affected by parasitic bronchitis, with clinical signs starting 13 days after infection. There were no discernible differences between the treated and control groups in their manifestations of resistance to D viviparus or their clinical responses to the disease produced.     

Immunity to parasitic bronchitis of yearling cattle treated with ivermectin during their first grazing season

A group of 12 winter-born calves was divided into two groups of six. During the following summer one group grazed on pasture infected with Dictyocaulus viviparus, and was treated with ivermectin injections at three, eight and 13 weeks after turn out. The other group remained housed. Both groups were housed during the winter and then together with a group of younger calves were challenged with a trickle infection of D viviparus larvae at the rate of 25 third stage larvae/kg bodyweight for one month and then slaughtered. The group which had been exposed to previous infection was least affected by parasitic bronchitis and on the basis of serological titres and worm burdens had developed resistance to the challenge infection. The other older group was also more resistant than the younger calves.     

Anthelmintic effect of levamisole hydrochloride or ivermectin on tissue toxocariasis of mice

Paranatal transmission of Toxocara canis infection could be prevented in pups if an effective drug were administered to pregnant bitches. This drug also could eliminate the larvae in dogs that have been experimentally infected repeatedly to produce protective immunity. For these reasons, we assayed the effect of 2 doses of levamisole hydrochloride or ivermectin on T canis larvae. Mice (5 groups) were infected with 1,000 infective T canis larvae and then treated with 2 different dosages of levamisole hydrochloride (6 mg/kg or 12 mg/kg, given subcutaneously), 2 different dosages of ivermectin (0.2 mg/kg or 0.4 mg/kg, given IM) or 0.15M NaCl (given subcutaneously) once a day from days 15 to 28 of infection. On day 33 of infection, the parasites in liver, lungs, brain, and carcass were obtained and compared between groups. The smaller dosage of levamisole hydrochloride (6 mg/kg) significantly decreased only carcass parasitism to 17% of that in the controls, but did not affect significantly the total parasite load. The larger dosage of levamisole hydrochloride (12 mg/kg) decreased the infection in all organs, but particularly in carcass and brain; total parasitism was only 36% of that in the controls. The smaller dosage of ivermectin (0.2 mg/kg) significantly increased the number of larvae in the lungs to 550% of that in the controls, but it did not significantly affect the total parasite load. The larger dosage of ivermectin (0.4 mg/kg) significantly decreased only brain parasitism, but liver and total parasitism were decreased to 40% and 57%, respectively, compared with that in the controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Treatment of inhibited Dictyocaulus viviparus in cattle with ivermectin

Fifteen calves, each infected with approximately 3000 third stage larvae, were used to compare the tendencies of two strains of Dictyocaulus viviparus to inhibit at the fifth larval stage and to evaluate the efficacy of ivermectin. There were notable differences between the strains. While greater than 99% of worms developing from infection with an Alpine strain remained inhibited 42 days after infection, only 0-26% of those recovered following infection with a U.K. laboratory strain were arrested. Neither adult nor immature D. viviparus were present in the lungs of animals treated with ivermectin subcutaneously at 200 micrograms/kg body weight 28 days after infection with the Alpine larvae.     

Evaluation of the efficacy of doramectin against an artificial infection of Dictyocaulus viviparus in calves

Three groups of eight Friesian calves, reared parasite-free, were experimentally infected with 1000 infective larvae of Dictyocaulus viviparus. Two groups were injected subcutaneously with 1% doramectin at 0.2 mg/kg body weight, one group 5 days after infection and the other 25 days after infection. A third group served as untreated controls. Faecal samples were examined for lungworm larvae on days 28, 32, 33, 34 and 35 after infection; the calves were killed and necropsied 39 or 40 days after infection and any lungworms present recovered and counted. Doramectin proved 100% effective against both 5-day-old and mature D. viviparus infections.     

Efficacy of oxfendazole against inhibited larvae of Ostertagia ostertagi in naturally infected calves in the southern USA

Forty yearling calves were assigned to four equal groups; three of the groups were treated with oxfendazole at dose rates of 6.75 mg/kg, 4.50 mg/kg, or 2.25 mg/kg bodyweight while the fourth group served as an untreated control. The calves were native to north-east Mississippi, USA, and harboured natural infections of gastrointestinal nematodes. The study was conducted during July when inhibited early fourth-stage larvae may be found in large numbers after their acquisition in the spring. The calves were maintained in separate groups on concrete-floored pens for 17 days before the intraruminal administration of oxfendazole. Seven days after treatment, the calves were slaughtered and the gastrointestinal parasites counted. At all the dose rates examined oxfendazole exhibited an efficacy of at least 99.4 per cent against adults of Haemonchus placei, Trichostrongylus axei, Bunostomum phlebotomum, Cooperia species, T colubriformis, Oesophagostomum radiatum, and Trichuris ovis. The efficacy against adult Ostertagia ostertagi was at least 99.4 per cent at dose rates of 6.75 and 4.50 mg/kg bodyweight, but decreased to 93.7 per cent at 2.25 mg/kg. The efficacy of oxfendazole against inhibited larvae of O ostertagi decreased with dose rate from 78.8 per cent at 6.75 mg/kg, to 58.9 per cent at 4.50 mg/kg and 20.3 per cent at 2.25 mg/kg bodyweight.