Efficacy of moxidectin 1% injectable and 0.2% oral drench against natural infection by Dictyocaulus filaria in sheep

Two separate trials (I and II) with 34 and 32 Churra ewes, respectively, and distributed into two groups, have been carried out to evaluate the efficacy of two different formulations of moxidectin at a dose rate of 0.2mg/kg body weight (b.w.) against natural infection by Dictyocaulus filaria in sheep. Trial I was designed to evaluate a 1% moxidectin injectable formulation, whereas in trial II a 0.2% moxidectin oral drench formulation was used. The efficacy was measured on the basis of the reduction of the faecal larval counts and of adult worm recoveries at slaughter.In each trial, a group of animals was treated on day 0 with moxidectin 1% injectable or moxidectin 0.2% oral drench and the other group acted as untreated control.When the faecal larval counts was compared within the treated groups, the efficacy was over 95% until day +13, and 100% at the remainder of the sampling dates after the application of injectable moxidectin, whereas in trial II, the larvae per gram (lpg) of faeces increased until the first sampling time post treatment (p.t.), day +6, and zero counts were recorded for all animals by the following days. On the basis of adult worm recoveries at necropsy, the efficacy of the treatment was 100% in both trials, however, adult worms were detected at slaughter for all control sheep. These results indicate that moxidectin 1% injectable and moxidectin 0.2% oral drench, administered at 0.2mg/kg b.w., were 100% effective against D. filaria infection in sheep. No adverse reactions to the treatments were observed in the animals.     

Experimental and natural infection of calves with Bunostomum phlebotomum

An experiment was conducted to determine the efficiency of a method of experimental infection of weaner beef calves with Bunostomum phlebotomum and to compare such infection with that established by natural infection. Six calves, maintained on a concrete-floored pen, were inoculated with B. phlebotomum L3 by placing the larval inocuulum, in small volume, in the outer chamber of the ear while the animal was restrained for 18 min. Inoculation doses of 20, 30, 40, 50, 60, and 80 thousand L3 were used. Six other calves were grazed on pasture known to be heavily contaminated with hookworm. All animals were killed 72 days after experimental infection and 93 days after initial exposure to pasture infection. The experimental and naturally-infected calves became patent at 55 and 66 days, respectively, after exposure to L3. Red blood cell counts and hemoglobin values were markedly depressed in both groups and lowest values coincided with onset of patency. There was difference in liveweight changes, but both groups lost weight during the prepatent period of infection and gained weight with the onset of patency. The largest number of hookworms was established at the 30000 L3 inoculation level; little or no establishment was observed at the 2 highest levels. Sizeable adult hookworm burdens were established in 4 out of 6 pastured calves. Intestinal pathology was generally more severe in experimentally-infected calves, consisting of a thickened mucosa and masses of punctate, hemorrhagic foci. Pastured calves also acquired large burdens of Ostertagia ostertagi, particularly inhibited early fourth-stage larvae. Moderate to severe abomasal pathology and elevated plasma pepsinogen were associated with ostertagiasis in the pastured calves. The experimental infection method is efficient in establishing high levels of B. phlebotomum infection in calves currently or previously infected with other gastrointestinal nematodes.     

Efficacy of moxidectin 1% injectable against natural infection of Sarcoptes scabiei in sheep.

Thirty ewes naturally infected with Sarcoptes scabiei var. ovis, were allocated into three groups of 10 animals each. Animals in groups B and C were treated on day 0 and on days 0 and +10, respectively, with moxidectin 1% injectable at a dose of 0.2mg moxidectin/kg body weight (BW). Group A remained untreated. Seven days before treatment, the geometric mean of Sarcoptes scabiei var. ovis per square centimeter of skin in groups A, B and C were not significantly different. From the day of treatment to the end of the trial, the average number of mites/cm(2) increased in untreated animals and decreased in groups B and C, but these values were higher for group C. Active lesions produced by S. scabiei var. ovis consistently increased during the trial in the untreated animals; in group B the minimum count occurred on day +56 this reduction being more evident in group C (no lesions on days +49 and +56). Also in this group, the number of cured animals was 100%, therefore, the application of two treatments with moxidectin (group C) showed higher efficacy than a single treatment (group B). Body condition score decreased in the three experimental groups along the trial. All animals were individually weighed on days -1, +28 and at the end of the trial. No adverse reactions were observed in the animals treated with 0.2mg moxidectin/kg BW.     

Efficacy of fenbendazole against adult Dictyocaulus viviparus in experimentally infected calves.

Fenbendazole, methyl-5(phenylthio)-2-benzimidazolecarbamate, a new broad-spectrum anthelmintic, was evaluated against the adult Dictyocaulus viviparus, lungworm of cattle, in artificially infected calves. At a dosage of 5 mg/kg of body weight, fenbendazole removed 100% of the worms if given as an oral suspension, and 99.7% of the worms if given as a feed additive.     

The efficacy of moxidectin against Dictyocaulus viviparus in cattle.

The efficacy of an injectable and a pour-on formulation of moxidectin against Dictyocaulus viviparus in cattle was examined. The results show that both formulations have an efficacy of 100% against adult worms and developing and inhibited larval stages of D. viviparus.     

Evaluation of the chemoprophylactic efficacy of 10% long acting injectable moxidectin against gastrointestinal nematode infections in calves in Belgium

The chemoprophylactic efficacy of a single dose of the 10% long acting (LA) injectable formulation of moxidectin on nematode infections in calves, was evaluated. Two similar groups of 11 female, first grazing season Holstein calves were turned out in early May on separate plots of a single, naturally infected pasture. Until 56 days post-treatment (pt), the percentage reduction in faecal egg output was 100%, remaining above 90% during the entire trial, except for day 126 pt. More than 90% of the larvae in the treated group were identified as Cooperia until 140 days after treatment and more than 70% during the rest of the trial, whereas in the control group Cooperia was the most abundant species until day 84 pt and Ostertagia from 126 days pt onwards. The reduction in faecal egg output in the treated group was reflected in the mean pepsinogen levels being below the pathogenic threshold at the end of the grazing season (1.8 units of tysrosine (U tyr)) and the absence of diarrhoea during the second half of the grazing season. In the control group pepsinogen levels remained high (mean: 5.5 U tyr) and prolonged diarrhoea occurred in the second half of the grazing season. Furthermore, the weight gain for the treated group at the end of the grazing season was 41.9 kg higher than for the control group. At necropsy, the reduction in O. ostertagi worm burden in the treated group was 97.5% compared to the control group, while the reduction in C. oncophora worm burden was 57%. An additional benefit of the long acting parasitological control, was reduced pasture contamination.     

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.     

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.     

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.     

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.     

Therapeutic and persistent efficacy of moxidectin 1% nonaqueous injectable formulation against natural and experimentally induced lung and gastrointestinal nematodes in cattle

Four controlled trials were conducted to evaluate the therapeutic and persistent efficacy of a new moxidectin formulation (moxidectin 1% nonaqueous injectable) against nematode parasites in cattle. This injectable moxidectin formulation, given as a single subcutaneous injection at a dose rate of 0.02 ml/kg BW to provide 0.2 mg moxidectin/kg BW, was highly efficacious (>90–100%) against larval and/or adult stages of many species of nematodes in cattle including, Dictyocaulus viviparus, Ostertagia spp., Trichostrongylus axei, Haemonchus placei, Trichostrongylus colubriformis, Cooperia spp., Nematodirus helvetianus, Strongyloides papillosus, Oesophagostomum radiatum and Trichuris spp. This formulation had persistent efficacy of >90% against D. viviparus for at least 6 weeks post-treatment, H. placei and Oe. radiatum for 5 weeks post-treatment, and Ostertagia spp. and T. axei for 2 weeks post-treatment.     

Dictyocaulus viviparus in calves: effect of rotational grazing on the development of infections.

A study was made of the possibility of reducing lungworm infections in young grazing calves by rotational grazing for weekly periods on six paddocks. For this purpose three groups of four calves each were grazed on separate pastures in 1989, whereas a fourth group served as a permanently housed control group. Two groups of calves were infected experimentally with six doses of 10 larvae of Dictyocaulus viviparus during the first 3 weeks on pasture. In the third group, low natural infections with overwintered larvae occurred. One of the experimentally infected groups was rotationally grazed for weekly periods on six small plots while both other groups were set-stocked. Faecal larval counts and worm counts in tracer calves demonstrated lower lungworm infections in the rotationally grazed group than in both set-stocked groups. However, the numbers of worms found after challenge infection and subsequent necropsy were relatively high in the rotationally grazed group, indicating that development of immunity was less than in both other groups. Owing to the dry weather conditions in the summer of 1989, no serious clinical signs of husk developed in any of the three groups. These dry conditions, however, did not prevent the build-up of heavy pasture infectivity with gastrointestinal nematodes resulting in heavy worm burdens and serious clinical signs in tracer calves grazing for 4 days in August and September-October, respectively. This implies that rotational grazing did not have a clear effect on build-up of gastrointestinal nematode infections.     

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.     

Sero-epidemiological survey of Dictyocaulus viviparus infections in first-season grazing calves in The Netherlands

A sero-epidemiological survey of Dictyocaulus viviparus infections in calves was carried out using an enzyme-linked immunosorbent assay. Infection level with D viviparus was correlated with farm, herd and management characteristics. At least 75 per cent of the herds were infected with D viviparus. Calves on zero-grazing farms were infected at a lower level than calves grazing pasture. No regional differences in infection rate were observed. On 15 per cent of the farms calves had clinical husk while 51 per cent of farms had experienced husk in the past. A higher level of infection was seen when calves were housed later in the autumn. The number of calves grazing together and the stocking rate had a significant positive influence on the level of infection. No significant difference in the occurrence of clinical husk was observed between calves vaccinated against lung-worm disease and calves not vaccinated against the disease.     

Efficacy of moxidectin against gastrointestinal nematodes of cattle.

Three groups of 11 naturally infected crossbred beef calves were injected subcutaneously with moxidectin 1 per cent injectable at 0.2 or 0.3 mg moxidectin/kg bodyweight or with the unmedicated vehicle. Nematode infections had been acquired during grazing from December to April. Based on the faecal egg counts and total worm counts of the control calves at necropsy (11 to 13 days after treatment) most of the calves had heavy parasitic burdens. Ostertagia ostertagi was predominant and the mean numbers of adults, developing fourth stage larvae (L4) and inhibited early L4 were 45,906, 10,061 and 68,918, respectively. Haemonchus placei and Trichostrongylus axei were also present in the abomasa. Three species of Cooperia, Oesophagostomum radiatum L4 and T colubriformis adults were found in the intestinal tract. Both dosages of moxidectin were equally effective (P < 0.05) against all the abomasal nematodes (99.9 to 100 per cent) and the intestinal tract nematodes (99.4 to 100 per cent). No adverse reactions to the moxidectin treatment were observed. Abomasal pathology characteristic of heavy O ostertagi infection was observed in the control calves, but not in the treated calves.     

Suppressive treatment of abamectin against Dictyocaulus viviparus and the occurrence of resistance in first-grazing-season calves

Dictyocaulus viviparus cause severe lung infections and are endemic in some areas of temperate and tropical countries. Treatment is based on strategic nematode control programs using potent compounds with no reports of drug failure. Macrocyclic lactones (MLs) are available at different concentrations and combinations and have being used heavily by producers. The objective of this work was to determine the efficacy of the MLs ivermectin, moxidectin, doramectin, and abamectin, and the combination ivermectin plus abamectin in naturally infected calves (n=70). Initial infection was determined by necropsy of tracer animals. Faecal larval counts determined that none of the compounds used was able to eliminate D. viviparus for up to 28 days after treatment. The "Area Nova" strain was isolated for future work.     

Efficacy of oral,injectable and pour-on formulations of moxidectin against gastrointestinal nematodes in cattle in New Zealand

The efficacy of moxidectin administered by different routes, against naturally acquired infections of gastrointestinal nematode parasites of cattle, was compared using faecal egg count reduction tests on 14 commercial farms throughout New Zealand. On each farm, groups of 15 calves were sampled for faecal nematode egg count and then treated with ivermectin administered orally, or with moxidectin administered either by the oral, subcutaneous injection or topical (pour-on) route. Samples were again collected 14 days after treatment and efficacy was calculated as the percentage reduction in-group mean egg count between the pre- and post-treatment samples. In addition, efficacy was calculated for individual animals, in order to compare the variability of the different treatments. On four farms untreated control groups were run and five animals from each of the control and all of the moxidectin-treated groups were bled over time to estimate plasma–moxidectin concentrations.Averaged across all tests, the reduction in faecal egg count was significantly greater after treatment with moxidectin oral (91.1%) than following treatment with moxidectin injection (55.5%) or with moxidectin pour-on (51.3%). Low efficacies were invariably against Cooperia oncophora. The oral treatments were significantly less variable in efficacy than the injection and pour-on treatments. Moxidectin concentrations in plasma were highest following subcutaneous injection and lowest following pour-on administration. Plasma levels following oral administration were intermediate, being significantly lower than post-injection and significantly higher than post-pour-on. There was no evidence of transfer of moxidectin to untreated animals through licking. Based on these results, along with those of other studies, it is proposed that oral administration of macrocyclic lactone anthelmintics results in higher concentrations of active reaching the target worms in the gastrointestinal tract than following either administration by injection or by pour-on.     

Dose confirmation studies of moxidectin 1% non-aqueous injectable and moxidectin 0.5% pour-on formulations against experimentally induced infections of larval and adult stage Oesophagostomum radiatum and Trichuris discolor in cattle

Separate controlled trials were conducted to evaluate the efficacy of two formulations of moxidectin (1% non-aqueous injectable solution and 0.5% pour-on (Cydectin) against larval or adult stages of Oesophagostomum radiatum and Trichuris discolor infecting cattle. Fifty-three strongylate-free dairy breed steer calves were obtained from commercial sources. After a brief acclimation period, calves were randomly divided into two pools to evaluate the efficacy of the moxidectin formulations against targeted larval (n = 27 calves) or adult (n = 26 calves) parasites. Calves in the larvacidal trial were inoculated on Day -16 relative to treatment with approximately 1000 embryonated Trichuris spp. eggs and approximately 640 infective Oesophagostomum spp. larvae. Calves were allocated by lottery to one of three treatment groups (n = 8 per group), which included: Group 1--moxidectin 0.5% pour-on (0.5 mg/kg body weight (BW)) applied topically; Group 2--moxidectin 1% non-aqueous injectable (0.2 mg/kg BW) administered subcutaneously; Group 3--untreated controls. Treatments were administered on Day 0 and calves were housed by group with no contact among animals of different treatments. Three sentinel calves were necropsied on Day 0 of the larvacidal trial to assess viability of larval inocula. On Days 14, 15 and 16 after treatment, calves were euthanatized (two or three from each group per day) and samples of gut contents were collected for determination of total worm counts. On Day -63 relative to treatment, calves in the adulticidal efficacy trial were inoculated with approximately 1000 embryonated Trichuris eggs and then on Day -35 with approximately 2500 infective Oesophagostomum spp. larvae. Fecal samples were collected on Day -7 and the 24 calves with the highest egg counts were assigned by lottery to the following three treatment groups (n = 8 per group): Group 4--moxidectin 0.5% pour-on; Group 5--moxidectin 1% injectable; Group 6--untreated controls. Details of experimental treatments, calf housing and necropsy scheduling were similar to the larvacidal trial. In both the larvacidal and adulticidal trials, inocula contained a variety of parasites in addition to the targeted species. Based on geometric means, both moxidectin 0.5% pour-on and moxidectin 1% non-aqueous injectable significantly reduced (P < 0.05) numbers of Oesophagostomum spp. and Trichuris spp. with anthelmintic efficacies of >99% when used against adult or larval stages of infection. In addition, both formulations of moxidectin demonstrated >95% efficacy (P < 0.05) against larval stages of Strongyloides papillosus. The pour-on formulation had >97% adulticidal and larvacidal efficacy against Cooperia spp. females, while the injectable product was effective against female Cooperia spp. larvae and Cooperia oncophora adult males.