Efficacy of doramectin against experimental infections by some nematode parasites in cattle in New Zealand

A study was undertaken to determine the efficacy of the novel avermectin, doramectin, against experimental larval and adult infections of three species of nematode parasite important to cattle production in New Zealand. Eighteen worm-free dairy bull beef calves were randomly allocated on live weight to three similar treatment groups. Each calf was given 30,000 Ostertagia ostertagi, 20,000 Cooperia spp. and 10,000 Trichostrongylus axei infective larvae as a single dose. One group was treated with doramectin 6 days after infection while the remaining groups received saline or doramectin 27 days after infection. Given as a single subcutaneous injection behind the ear, doramectin at 200 microg/kg removed 99.9-100% of adult and larval stages of O. ostertagi, Cooperia spp. and T. axei when compared to infections established in untreated controls (p<0.001). No adverse reactions were observed following treatment in the doramectin-treated animals. No injection site lesions were found by palpation following treatment or by injection site examination at necropsy.     

Activity of the Pinus elliottii resin compounds against Lernaea cyprinacea in vitro

Lernaea cyprinacea infestation is a major problem for fishing culture in Brazil, which was introduced in the mid-eighties. To attempt controlling this parasite, an evaluation of the activity of the Pinus elliottii resin constituents against it was undertaken. To run the bioassay, fish infested with L. cyprinaceae were transferred to aquaria and kept at room temperature and ventilation for 15 days for adaptation. Afterwards, fish were sacrificed and the parasites were kept under water to run the experiments by evaluating the activities of the steamed oil and the chloroform fraction of the resin at concentrations of 0.5, 1.0, 2.0 and 5.0 ppm. The crude resin was also evaluated at concentrations of 1.0, 5.0 and 10 ppm, as well as the major components of its steamed oil, alpha and beta-pinenes, both at concentrations of 0.5 and 1.0 ppm. The results showed that both fractions from the resin were effective at 0.5 ppm concentration, while the pure compounds were less active. Moreover, the acute toxicity (DL(50)) of the crude resin for the fish Leptorinus piau, aged 1 month, was established at 200.0 ppm, which ensures its safe use.     

Comparative susceptibility of carp fingerlings to Lernaea cyprinacea infection

Study was conducted to find out the comparative susceptibility of fingerlings of seven species of carps (Labeo fimbriatus, L. rohita, L. calbasu, Catla catla, Ctenopharyngodon idella, Cyprinus carpio and Hypophthamichthys molitrix) grown under both mono and polyculture to Lernaea cyprinacea infection. Under monoculture, C. carpio, L. rohita and L. calbasu, did not acquire Lernaea infection and were thus considered resistant, whereas C. idella, H. molitrix, C. catla and L. fimbriatus were susceptible. Even challenge with higher infective doses of copepodids under monoculture did not result in infection in the resistant fish species. The resistance of L. rohita and C. carpio to Lernaea infection under monoculture was not sustained when these two fish species were maintained in polyculture along with susceptible fish species. Labeo calbasu, even under polyculture, however, did not acquire Lernaea infection indicating that this fish species is the most resistant and least preferred host for this parasite. Similarly, C. carpio, L. rohita and L. calbasu when grown together in polyculture and exposed to a higher infective dose (120 copepodids/fish) also did not develop the infection. The possible reasons for differences in susceptibility shown by these carp species in monoculture and the loss of resistance by rohu and common carp while in polyculture with susceptible species are discussed. The ability of resistant fish species to prevent establishment of anchor worms on them under monoculture can be utilized to control this parasitic infection commonly encountered in culture ponds.     

Efficacy of ivermectin against experimental and natural infections of Gasterophilus spp in ponies

Antiparasitic efficacy of ivermectin against migrating Gasterophilus intestinalis was evaluated in 36 treated and 24 nontreated (n = 12) or vehicle-treated (n = 12) ponies experimentally and naturally infected with G intestinalis and naturally infected with G nasalis. Each pony was experimentally infected with 500 G intestinalis 1st instars in 2 divided doses on days -14 and -7 before treatment. On day 0, ivermectin was administered at the rate of 200 micrograms/kg of body weight by IV (n = 12) or IM injection (n = 12) or given as an oral paste (n = 12). Ponies were euthanatized and necropsied 21 days after treatment. In each nontreated or vehicle-treated pony, late 1st-, 1st- to 2nd- instar molt, and early 2nd-instars of G intestinalis were found in the mouth, and 2nd- and 3rd instars of G intestinalis and 3rd instars of G nasalis were found in the stomach. Bots were not found in any ivermectin-treated pony and, thus, ivermectin was 100% effective against oral and gastric stages. Adverse reactions were not observed in ponies given ivermectin by IM injection or orally, but 1 pony given the vehicle IV and 1 pony given ivermectin (in the vehicle) IV had an anaphylactic reaction, resulting in death of the ivermectin-treated pony. It was speculated that the adverse reaction was caused by histamines released in response to vehicle components given by IV injection.     

The effect of doramectin, moxidectin and netobimin against natural infections of Syphacia muris in rats

In this study, the effect of doramectin, moxidectin and netobimin was investigated in naturally infected Syphacia muris in rats. The natural infection was determined by the use of cellophane tape method on the perianal region and by the technique of centrifugal flotation of feces. The infected rats were divided into three treated and one control group (N = 10). Doramectin and moxidectin at the dose of 0.2 mg/kg per day and netobimin at the dose of 7.5 mg/kg per day were given in the diet for 4 days. Cellophane tape preparations were performed in all groups on 4th and 7th day after the last treatment. The rats of treated groups were necropsied on 7th day after the last treatment together with that of control group. While doramectin and netobimin were highly effective against S. muris, moxidectin was not found to be effective for eradication of S. muris.     

多拉菌素注射剂对牦牛皮蝇幼虫的驱杀效果试验

多拉菌素(doramectin)又称都林霉素,是一种新型的阿佛曼菌素类药物一阿维菌素(avermectins)的第3代衍生物,其驱虫机理与伊维菌素相同,但抗虫作用强大而持久[1].     

Massive Lernaea cyprinacea Infestations Damaging the Gills of Channel Catfish Polycultured with Bighead Carp

Abstract

During June and July 1998, at least three Arkansas fish farms polyculturing bighead carp Hypophthalmichthys nobilis with channel catfish Ictalurus punctatus suffered major losses of catfish associated with massive infestations by the crustacean parasite Lernaea cyprinacea. The channel catfish had few adult Lernaea attached to their skin, but there were 8–50 Lernaea copepodids on the surface of each catfish gill filament. The copepodids were found grazing on the gill tissue, and their feeding activity was associated with gill damage including epithelial hyperplasia, telangiectasis, and hemorrhage. Bighead carp in the same ponds were reported to have had numerous adult Lernaea on their skin but did not die during the epizootic. It is possible that the filter-feeding apparatus of the carp captured the copepodids, thus preventing heavy infestation of the gill filaments. Lernaea copepodids have not been implicated previously in fish losses resulting from parasite damage to the gills. The loss of catfish in these cases is likely to be due to their polyculture with the bighead carp, a species that provides an excellent host for adult Lernaea.     

Persistent efficacy of doramectin and moxidectin against Cooperia oncophora infections in cattle

Duplicate studies in France and Northern Ireland were carried out to determine the persistent efficacy of topical moxidectin and doramectin against natural infections of Cooperia oncophora. In each study, groups of 15 nematode-na?ve calves were treated either with topical doramectin or moxidectin, and put out to graze on pasture contaminated with C. oncophora infective larvae. The persistent efficacy for preventing establishment of infection was assessed by the time to faecal egg excretion of C. oncophora eggs. It was found that the moxidectin treatment prevented infection for less than 10 days and the effect of doramectin lasted for 24 days.     

Efficacy of doramectin against naturally acquired adult and inhibited larval infections by some nematode parasites in cattle in New Zealand

A study was conducted to determine the therapeutic efficacy of 1% doramectin injected subcutaneously at 200 microg/kg into cattle harbouring naturally acquired infections of inhibited Ostertagia ostertagi larvae. Sixteen yearling Friesian bulls, grazed without anthelmintic treatment throughout the autumn-winter, were selected on the basis of similar body weights and serum pepsinogen activities. After removal from pasture on day -23 they were weighed and randomly assigned to two treatment groups on the basis of this weight. On day 0, one group was given saline (1 ml/50 kg) while the second was treated with doramectin (200 microg/kg). Both treatments were given by subcutaneous injection. All stock were slaughtered 14-15 days after treatment. Moderate to high levels of adult O. ostertagi and Trichostrongylus axei and early and late 4th larval stages of O. ostertagi were recovered from saline-treated calves at necropsy. Doramectin was highly effective in eliminating all stages of O. ostertagi (99.9%; p<0.0001) and T. axei (100%; p<0.0001). No evidence of lesions were detected at the injection sites at necropsy. These results confirm that doramectin is an extremely effective broad-spectrum avermectin anthelmintic with efficacy against inhibited as well as maturing larval and adult forms of O. ostertagi.     

Efficacy of doramectin against naturally acquired adult and inhibited larval infections by some nematode parasites in cattle in New Zealand

A study was conducted to determine the therapeutic efficacy of 1% doramectin injected subcutaneously at 200 uglkg into cattle harbouring naturally acquired infections of inhibited Ostertagia ostertagi larvae. Sixteen yearling Friesian bulls, grazed without anthelmintic treatment throughout the autumn-winter, were selected on the basis of similar body weights and serum pepsinogen activities. After removal from pasture on day -23 they were weighed and randomly assigned to two treatment groups on the basis of this weight. On day 0, one group was given saline (1 ml/SO kg) while the second was treated with doramectin (200 𝛍g/kg). Both treatments were given by subcutaneous injection. All stock were slaughtered 14–1.5 days after treatment. Moderate to high levels of adult O. ostertagi and Trichostrongylus axei and early and late 4th larval stages of O. ostertagi were recovered from saline-treated calves at necropsy. Doramectin was highly effective in eliminating all stages of O. ostertagi (99.9%; p<0.0001) and T: axei (100%; p<0.0001). No evidence of lesions were detected at the injection sites at necropsy. These results confirm that doramectin is an extremely effective broad-spectrum avermectin anthelmintic with efficacy against inhibited as well as maturing larval and aduit forms of O. ostertagi.     

Efficacy of the amino-acetonitrile derivative,monepantel, against experimental and natural adult stage gastro-intestinal nematode infections in sheep

Multiple drug resistance by nematodes, against anthelmintics has become an important economic problem in sheep farming worldwide. Here we describe the efficacy of monepantel, a developmental molecule from the recently discovered anthelmintic class, the amino-acetonitrile derivatives (AADs). Efficacy was tested against adult stage gastro-intestinal nematodes (GINs) in experimentally and naturally infected sheep at a dose of 2.5 mg/kg body weight when administered as an oral solution. Some of the isolates used in experimental infection studies were known to be resistant to the benzimidazoles or levamisole anthelmintics; strains resistant to the macrocyclic lactones were not available for these tests. Worm count-based efficacies of >98% were determined in these studies. As an exception, Oesophagostomum venulosum was only reduced by 88% in one study, albeit with a low worm burden in the untreated controls (geometric mean 15.4 worms). Similar efficacies for monepantel were also confirmed in naturally infected sheep. While the efficacy against most species was >99%, the least susceptible species was identified as Nematodirus spathiger, and although efficacy was 92.4% in one study it was generally >99%. Several animals were infected with Trichuris ovis, which was not eliminated after the treatment. Monepantel demonstrated high activity against a broad range of the important GINs of sheep, which makes this molecule an interesting candidate for use in this species, particularly in regions with problems of anthelmintic resistance. Monepantel was well tolerated by the treated sheep, with no treatment related adverse events documented.     

Efficacy of doramectin against naturally acquired nematode infection in Iberian swine

Studies were carried out to determine the therapeutic efficacy of doramectin, administered intramuscularly at a dose of 300 microg/kg live weight, against naturally acquired helminths of extensively farmed Iberian pigs. The first study (slaughter study) evaluated, through necropsy of the study animals, the product's efficacy against gastrointestinal and pulmonary nematodes (Ascaris suum, Oesophagostomum dentatum and Metastrongylus sp.) whilst the second, faecal egg count reduction study, (FECR study) evaluated the drug's efficacy only against gastrointestinal helminths (A. suum, Trichuris suis and Oesophagostomum sp.).The first study used 20 animals divided into two equal groups of 10 on the basis of body weight and faecal egg count. One group constituted saline treated controls and the other was doramectin treated. On Day 14 post treatment half of the animals in each group were necropsied and the number of parasites present counted. On Day 15 the remaining half of each group underwent the same procedure. The second study was carried out with 40 animals divided equally into two groups of 20. This study determined the effect of doramectin treatment on faecal egg counts as an indicator of parasite burden.The first study demonstrated an efficacy of 100% against adult Metastrongylus sp. and A. suum, whilst the efficacy against O.dentatum was 96.3%. The second study indicated that at Day 21 post treatment there was a 100% reduction in egg counts in faeces in comparison to untreated controls.     

Efficacy of injectable ivermectin against natural infections of Stephanurus dentatus in swine

Ivermectin (300 micrograms/kg of body weight) was given to swine subcutaneously in the neck to test its efficacy against the kidney worm, Stephanurus dentatus. Two separate field trials were conducted using 146 swine (40 males and 106 females). Urine was obtained before and after treatment and was examined for presence of S dentatus eggs. Stephanurus dentatus eggs were quantitated in positive samples. All treated swine positive for S dentatus eggs in the pretreatment urine samples (n = 54) were negative by 14 to 21 days after treatment with ivermectin. Adverse reactions caused by ivermectin injection were not noticed.     

Efficacy of Cydectin moxidectin 1% injectable against experimental infections of Dictyocaulus viviparus and Bunostomum phlebotomum superimposed on natural gastrointestinal infections in calves.

Twenty male Holstein calves averaging 105 kg in weight and naturally infected with gastrointestinal nematodes and small numbers of lungworm and hookworm, were given experimental infections with the two latter species to provide adult and larval stages for anthelmintic evaluation. Following random allotment, one group of 10 calves was injected subcutaneously with moxidectin at a dosage of 0.2 mg kg-1 of body weight. A second group of 10 was injected subcutaneously with unmedicated blank vehicle at a dosage of 1 ml per 50 kg of body weight. Fecal samples were examined before treatment and at 7 and 13 days after treatment. The 20 calves were necropsied for worm recovery at 13 and 14 days after treatment. All calves were positive for lungworm and hookworm on the treatment date. Treatment was 100% effective in elimination of hookworm eggs and lungworm larvae and 99.9% in reducing total egg counts at both 7 and 13 days after treatment. Moxidectin was 100% effective (P less than 0.01) in eliminating the following 11 species of nematodes. Dictyocaulus viviparus mature and immature adults (E5), Bunostomum phlebotomum adults and L4, Ostertagia ostertagi adults and early L4, Ostertagia lyrata adult males, Haemonchus placei adults. Trichostrongylus axei adults, Cooperia spp., including Cooperia punctata, Cooperia spatulata, and Cooperia pectinata adults, Oesophagostomum radiatum adults and Trichuris discolor adults. No adverse reactions to moxidectin treatment were observed.     

Efficacy of enrofloxacin against severe experimental Anaplasma marginale infections in splenectomized calves

Four Anaplasma marginale-infected splenectomized calves with greater than 25% parasitized erythrocytes received enrofloxacin at 12.5 mg/kg SC twice, 48 hours apart. Two infected splenectomized calves were designated as untreated controls. A precipitous decline in percent parasitized erythrocytes from 39.13% to less than 1% was observed over 12 days following treatment. However, a self-limiting recrudescence of A. marginale parasites was observed within 30 days after treatment. Untreated control calves became moribund and were euthanized. These data indicate that the regimen of enrofloxacin tested herein ameliorates, but does not eliminate, A. marginale infections in splenectomized calves.     

Persistent efficacy of doramectin pour-on against artificially induced infections of nematodes in cattle.

Two studies were conducted to determine the persistent efficacy of doramectin pour-on against an artificial, trickle challenge of mixed nematodes in calves. In each study, 42, 4-8 months old calves were randomly assigned into four groups of 10 animals each (T1-T4), plus two larval-viability monitor animals. All animals were treated with fenbendazole (10 mg kg(-1)) 14 days prior to the start of the study to clear any existing infection. Doramectin pour-on at 500 microg kg(-1) was used on each animal in Groups T2, T3, and T4 with intervals of 1 week (Day 0, 7, and 14, respectively). Calves in Group T1 were treated with saline solution on Day 0 and at the same volumetric rate (1 ml 10 kg(-1)) as the doramectin treated animals. All treatments were applied in a single passage along the midline of the back, from the withers to the tailhead. Subsequently, trickle inoculations with infective larvae were administered to all calves for 22 consecutive days (Days 14-35). Doramectin pour-on provided > or = 91.9% efficacy against challenge with Dictyocaulus viviparus, Haemonchus spp., and Ostertagia ostertagi for up to 35 days post-treatment and against challenge with Cooperia oncophora, Cooperia punctata, and Oesophagostomum radiatum for up to 28 days post-treatment.     

Efficacy of a pour-on formulation of doramectin against lice, mites, and grubs of cattle

OBJECTIVE: To determine effectiveness of a pour-on formulation of doramectin against Damalinia bovis, Haematopinus eurysternus, Linognathus vituli, Solenopotes capillatus, Chorioptes bovis, Sarcoptes scabiei, Hypoderma bovis, and Hypoderma lineatum. ANIMALS: Cattle of various ages with naturally acquired or artificial infestations with 1 or more species of lice, mites, or grubs. PROCEDURE: In 10 louse and 6 mite studies, cattle were treated with doramectin (500 microg/kg, topically) on day 0, and parasite counts were performed approximately weekly from days 0 to 35. In 6 grub studies, cattle expected to harbor Hypoderma spp were treated before emergence of warbles. After warbles began to emerge, they were counted every 2 weeks, and grubs were collected and identified by species. RESULTS: Burdens of D bovis, H eurystemus, L vituli, and S capillatus on doramectin-treated cattle were 0 by 28 days after treatment. Burdens of C bovis and S scabiei decreased to 0 in naturally infested cattle and approximately 0 in artificially infested cattle by day 14 to 15. In grub studies, 107 of 136 control cattle had warbles, whereas 2 of 136 doramectin-treated cattle had 1 warble each, which represented a cure rate of 98.5%. CONCLUSION AND CLINICAL RELEVANCE: One topical application of doramectin was highly efficacious against common species of lice, mites, and grubs known to affect performance, health, and appearance of cattle.     

Persistent activity of doramectin injectable formulation against experimental challenge with Haemonchus placei in cattle.

Two studies were conducted in North America to evaluate the persistent activity of doramectin injectable formulation against experimental challenge with Haemonchus placei. In both studies, calves were randomly assigned to 1 of 4 treatment groups (n = 10 per group) or a larval viability group (n = 2). Calves were treated subcutaneously in the lateral midline of the neck with saline (1 ml/50 kg) on Day 0, or with doramectin (200 mg/kg = 1 ml/50 kg) on Day 0, 7, or 14. Animals used to assess larval viability did not receive any treatment. Beginning on Day 14 and continuing through Day 28, each of the 40 treated calves were given approximately 300 infective larvae of H. placei per os. The two larval viability animals received approximately 10,000 larvae as a single dose on Day 28. Approximately two weeks later, all animals were slaughtered and the abomasum from each calf processed for nematode recovery. A 2% aliquot of abomasal contents plus wash was examined for enumeration and identification of nematodes. Geometric mean H. placei counts were calculated from the log (H. placei count +1) and used to estimate percentage reduction. Overall, doramectin was > or =96.9% efficacious in reducing infection with H. placei when challenged daily 14-28 days after treatment.