Efficacy of ivermectin in a topical formulation against induced gastrointestinal and pulmonary nematode infections, and naturally acquired grubs and lice in cattle

Efficacy of ivermectin in a topical formulation was evaluated in cattle against adult gastrointestinal and pulmonary nematode infections (experiment 1, n = 24), the 2nd- and 3rd-stage larvae of Hypoderma spp (experiment 2, n = 12), and the biting louse Damalinia bovis (experiment 3, n = 12). Nematode infections were induced and grubs and lice were naturally acquired. Treatments consisted of a single dose of ivermectin in a topical formulation of 200, 500, or 1,000 micrograms/kg of body weight in experiment 1 or 500 micrograms/kg in experiments 2 and 3. At 1,000 micrograms/kg, ivermectin was 100% effective against Ostertagia ostertagi, Trichostrongylus colubriformis, Oesophagostomum radiatum, Nematodirus helvetianus, Haemonchus placei, and Dictyocaulus viviparus and was greater than 99% effective against Cooperia oncophora, C punctata, and T axei. At 500 micrograms/kg, the efficacy was 100% against C oncophora, C punctata, O ostertagi, T axei, Oes radiatum, N helvetianus, Haem placei, and Dict viviparus and greater than 99% against T colubriformis. At 200 micrograms/kg, the efficacy was 100% against Oes radiatum, Haem placei, and Dict viviparus, greater than 99% for O ostertagi, 96% for C oncophora, 86% for C punctata, 90% for T axei, 85% for T colubriformis, and 71% for N helvetianus. At 500 micrograms/kg, ivermectin was highly effective against the grubs Hypoderma bovis and H lineatum and eliminated the louse Damalinia bovis.     

Persistent anthelmintic activity of topically administered ivermectin in cattle

The persistent anthelmintic effect of ivermectin as a topical treatment at 500 microg/kg was evaluated against induced infections of Ostertagia ostertagi, Trichostrongylus axei and Dictyocaulus vivparus in calves. The results showed a highly significant (P<0.001) anthelmintic activity for at least 14 days against O. ostertagi and T.axei (>99 per cent efficacies) and for at least 28 days (98 per cent efficacy) against D. viviparus.     

Efficacy of febantel against abomasal nematodes and lungworms in cattle

The efficacy of febantel at a dosage of 5 mg/kg (45.5% paste formulation) against inhibited early 4th-stage larvae (EL4) of Ostertagia ostertagi, other nematodes of the abomasum, and Dictyocaulus viviparus was investigated in 4- to 6-month-old Holstein calves that grazed on pasture heavily contaminated with parasites from February 24 to April 1, 1986 (36 days). In Louisiana, this is the first month of a 3-month period in which increasing numbers of inhibition-prone O ostertagi larvae are acquired, and infection risk with D viviparus may remain high. Three of 4 calves that died of lungworm infection during the pasture-exposure period were necropsied. Large numbers of abomasal nematodes, including inhibited O ostertagi larvae, and large numbers of D viviparus were recovered. Twenty-five calves were randomly allotted by equal distribution of body weight to 2 groups and treated on April 4: placebo-treated calves (n = 13) and febantel-treated calves (n = 12). Equal numbers of treated and control calves were killed at 6 and 7 days, respectively, after treatment. Mean numbers of O ostertagi in control cattle were: adults, 4,931; developing 4th-stage larvae (DL4), 1,119; and inhibited EL4, 3,410. Ostertagia lyrata, Trichostrongylus axei, Haemonchus sp, and D viviparus were well distributed in nearly all control calves. Percentage reduction of O ostertagi in treated calves, when compared with controls, was: adults, 83.6%; DL4, 57.8%; and inhibited EL4, 34.8%. Percentage reductions of other species were: O lyrata, 92.6%; T axei adults, 99.3% and 4th-stage larvae (L4), 100%; Haemonchus sp adults, 66.7%, and L4, 64%; D viviparus adults 90.6%, and immature forms, 97.1%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of topically administered doramectin against eyeworms, lungworms, and gastrointestinal nematodes of cattle.

OBJECTIVE: To evaluate efficacy of topically administered doramectin against eyeworms, lungworms, and gastrointestinal nematodes of cattle. ANIMALS: 400 cattle (20 cattle in each of 20 trials). PROCEDURE: Trials were conducted in North America; natural and experimentally induced infections were used. In each trial, cattle were allocated randomly to control (placebo [saline [0.9% NaCl] solution at 1 ml/10 kg of body weight] or untreated; n = 10) or doramectin-treated (500 microg/kg of body weight; 10) groups. Treatments were applied in a single passage along the midline of the back, from the withers to the tailhead. Cattle were euthanatized > or =14 days after treatment, and worm burdens were determined by use of standard techniques. RESULTS: Efficacy of doramectin was > or =95.3% against adults of Thelazia gulosa, T skrjabini, Dictyocaulus viviparus, Haemonchus contortus, H placei, Ostertagia lyrata, O ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Capillaria spp, Cooperia oncophora, C pectinata, C punctata, C spatulata, C surnabada, Nematodirus spathiger, Strongyloides papillosus, T colubriformis, Oesophagostomum radiatum, and Trichuris spp. Efficacy was 95.1% against fourth-stage larvae of D viviparus, H placei, O lyrata, O ostertagi, T axei, C oncophora, C punctata, C spatulata, C surnabada, N helvetianus, T colubriformis, O radiatum, and Trichuris spp. In addition, efficacy against inhibited fourth-stage larvae of O ostertagi and Ostertagia spp was > or =98.1%. CONCLUSIONS AND CLINICAL RELEVANCE: A single topical application of doramectin pour-on was efficacious against a broad range of nematode species in cattle.     

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.     

Ivermectin: controlled test of anthelmintic activity in dairy calves with emphasis on Dictyocaulus viviparus

Twelve dairy calves, naturally infected with lungworms and gastrointestinal parasites, were selected for a controlled test with single doses of ivermectin, administered subcutaneously, at the dose rate of 200 micrograms/kg. Specific interest was on efficacy of ivermectin against lungworms (Dictyocaulus viviparus), with ancillary interest directed on abomasal parasites. Ivermectin was administered to 6 calves, and the vehicle only, to 6 calves. At necropsy, 7 days after treatment, lungworms were not recovered from any of the treated calves; nontreated calves, given the vehicle only, were infected with 1 to 46 lungworms each. Removal efficacy against adult Ostertagia ostertagi was 99%. Fourth-stage Ostertagia spp and Trichostrongylus spp and mature Trichostrongylus axei, present in low numbers, were all removed. The fecal egg count for gastrointestinal parasites indicated all eggs, except for a few Nematodirus eggs, were cleared from treated calves. One treated calf showed signs of irritation of the neck at injection site for a short time after treatment and 1 treated calf had a slight indurated area at injection site at necropsy.     

Synergistic influence of Ostertagia ostertagi and Trichostrongylus axei on Ostertagia ostertagi larval inhibition and abomasal lesions in cattle

Parasite-free 4-month-old calves were inoculated with Ostertagia ostertagi and/or Trichostrongylus axei followed 6 weeks later by increasing doses of O ostertagi for 8 weeks. Clinical signs of parasitism, fecal egg counts, and plasma pepsinogen concentrations were monitored, and gross lesions and parasite burdens were determined postmortem. Clinical signs of parasitism were not observed and weight gains were not affected in experimentally infected calves. In calves infected with O ostertagi, mean plasma pepsinogen concentrations were greater than for control calves and were diagnostically significant 4 weeks after inoculation and during the last 4 weeks of serial inoculations with O ostertagi. In calves that were given O ostertagi and T axei, abomasal pH was significantly increased, and abomasal lesions were more pronounced than in control calves or in calves inoculated with only O ostertagi or T axei. Abomasal lymph nodes were enlarged in all parasitized calves; other lymph nodes in the calves inoculated with both O ostertagi and T axei were usually smaller than in calves inoculated with only O ostertagi or T axei. Numbers of O ostertagi-inhibited larvae were small in all inoculated calves, but the percentage inhibition was significantly greater in calves inoculated with both O ostertagi and T axei. The percentage inhibition was 3.53% for the O ostertagi-inoculated calves and 7.07% for calves inoculated with both O ostertagi and T axei. These percentages indicated a synergistic effect of concurrent abomasal parasitism, whereas a synergistic effect on T axei worm burden was not observed. The low percentage of larval inhibition indicated that factors other than host resistance are involved in naturally occurring pretype II ostertagiosis.     

Efficacy of abamectin against natural infections of gastrointestinal nematodes and lungworm of cattle with special emphasis on inhibited, early fourth stage larvae of Ostertagia ostertagi.

The anthelmintic efficacy of abamectin (avermectin B1) was evaluated against gastrointestinal nematodes, including Ostertagia ostertagi inhibited larvae and lungworm, in yearling crossbred beef heifers during late spring. The calves were grazed on contaminated pasture for 10 weeks and then held under conditions free of nematode infection for 3 weeks prior to allotment and treatment on 5 June. Thirteen calves were randomly assigned to two groups of six by restricted randomization on body weights; the extra lightest calf was assigned to the non-treated control group. Group 1 calves were treated with abamectin at 200 micrograms kg-1 body weight by s.c. injection and Group 2 calves were not treated; all were killed at 14 days after treatment. Ostertagia ostertagi was present in all controls; arithmetic mean numbers of adults, developing fourth stage larvae (L4) and inhibited EL4 were 7683, 605 and 36,102, respectively. Other nematode genera present in controls in sufficient numbers for the experiment were Haemonchus placei adults, Trichostrongylus axei adults, Cooperia spp. adults, Oesophagostomum radiatum adults, Bunostomum phlebotomum adults, Dictyocaulus viviparus adults and E5 (immature adults). Abamectin was highly effective (consistently greater than 99% efficacy and P less than 0.05) in removing all nematodes present in treated calves as represented in non-treated controls, including the primary target of Ostertagia ostertagi inhibited EL4. The lowest efficacy was 93.8%, against D. viviparus E5.     

Anthelmintic efficacy of ivermectin against immature gastrointestinal pulmonary nematodes of calves

Anthelmintic efficacy of ivermectin (greater than or equal to 80% 22,23-dihydroavermectin B1a and less than or equal to 20% 22,23-dihydroavermectin B1b) was evaluated in a controlled experiment against immature nematodes. Twenty calves raised to about 8 weeks of age under nematode-free conditions were allocated into 4 groups. Infective larvae of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, Oesophagostomum radiatum, and Dictyocaulus viviparus were given orally to each calf on a staggered schedule 6 to 14 days before treatments. The drug was given subcutaneously when the nematodes were in the early 4th stage of development, and the calves were killed 23 or 24 days later. Group 1 nonmedicated control calves had a geometric mean of 25,102 nematodes; groups 2, 3, and 4 calves given ivermectin at dose rates of 50, 100, or 200 micrograms/kg had reductions of 88.2%, 98.0%, and 99.8%, respectively.     

Further tests of activity of levamisole on Ostertagia ostertagi in dairy calves with notes on overwinter survival of gastrointestinal helminths on pasture

Two controlled tests were conducted in 1981 and 1982 in dairy calves on the University of Kentucky research farm to determine activity of the bolus formulation of levamisole given at the dose rate of 8 mg/kg against naturally occurring infections of Ostertagia ostertagi. Removal efficacies of mature O ostertagi were 98% in the 1981 test (3 treated and 3 nontreated calves) and 94% in the 1982 test (7 treated and 8 nontreated calves). Against immature Ostertagia spp, removal efficacies were 100% and 65% for the 1st and 2nd tests, respectively. The calves were grazed on the same pasture as dairy calves in previous controlled tests in 1979 and 1980 where activity of levamisole against mature O ostertagi (data recently published) was much less than in the present tests. It does not appear that the poor performance in the early tests can be attributed to the drug resistance phenomenon. Data on overwinter survival (119 days) of free-living stages of gastrointestinal parasites on pasture were derived from the nontreated calves in the 1982 controlled test. The calves, raised helminth-free, were placed on the pasture on Apr 5, 1982. Helminths recovered at necropsy of the calves, besides O ostertagi, included Trichostrongylus axei, Nematodirus helvetianus, Nematodirus spp, Cooperia oncophora, Trichuris spp, and Moniezia spp. The lung-worm, Dictyocaulus viviparus, previously found in cattle on the farm, was not found in these calves.     

Efficacy of ivermectin against the abomasal nematode mecistocirrus digitatus in naturally infected zebu calves

Anthelmintic efficacy of ivermectin against Mecistocirrus digitatus was evaluated in 10 naturally infected zebu calves. Group 1 (n = 5) was not treated, and group 2 (n = 5) was treated SC with 200 micrograms of ivermectin/kg of body weight. Calves were euthanatized 14 or 15 days after treatment. There was 100% overall reduction of M digitatus in treated calves, which was significant (P = 0.0079) compared with reduction in controls. Cooperia punctata, Haemonchus similis, and Trichostrongylus axei were found in controls. Efficacy against these parasites in treated calves was 100%.     

Effects of ivermectin and fenbendazole in strategic treatment of gastrointestinal nematode infections in cattle

Four groups of 18 beef calves each were used to evaluate effects of different treatments on parasite control and weight gains. The investigation extended from November 1986 (weaning) to October 1987. Group-1 calves were treated with ivermectin (200 micrograms/kg of body weight, SC) at approximately 6-week intervals for a total of 8 treatments; group-2 calves were given the same dosage of ivermectin by the same route of administration as group-1 calves in November, March, and July; group-3 calves were given fenbendazole paste (5 mg/kg, PO) at the same times as group-2 calves; and group-4 calves served as untreated controls with provision for ivermectin salvage treatment. All groups grazed on individual pairs of larval-contaminated, 1.6-ha pastures. Highest (P less than 0.05) initial worm counts in fall tracer calves were found in group 3 (Ostertagia ostertagi and Trichostrongylus axei adults) and group 4 (O ostertagi and Haemonchus adults). Fecal egg counts of group-1 calves were low throughout the experiment and pasture larval counts remained negligible after July. Egg counts and larval counts of other groups remained higher into summer. Worm counts, including O ostertagi inhibited early fourth-stage larvae (EL4), were highest (P less than 0.05) in groups-3 and -4 spring tracer calves; numbers of O ostertagi EL4 were similarly high in groups 2, 3, and 4; and T axei counts were highest (P less than 0.05) in groups-3 and -4 yearlings slaughtered in spring. Liveweights of group-1 calves were greater (P less than 0.05) than in other groups from March 2 to October, and by July 2, group-2 calves had a liveweight advantage over group-4 calves. Group-3 calves had the lowest rate of gain from March to July and mean liveweight of the group was less (P less than 0.05) than in all other groups from April to October. Only minimal worm numbers were recovered from groups-1 or -2 calves in October. Large numbers of O ostertagi and T axei were recovered from group-4 calves and O ostertagi from group-3 calves. A few calves in groups 3 and 4, but particularly in group 4, were affected by type-II disease (chronic to acute gastritis caused by maturation and emergence of previously inhibited larvae) from August to October. Final mean liveweights in descending order were 365 kg in group 1, 328 kg in group 2, 316 kg in group 4, and 281 kg in group 3.     

Efficacy of ivermectin delivered from a sustained-release bolus against inhibited early fourth-stage larvae of Ostertagia ostertagi and other nematodes in cattle.

The anthelmintic efficacy of ivermectin (IVM) delivered from a sustained-release (SR) bolus was evaluated against natural infections with gastrointestinal tract nematodes in 12 crossbred beef heifers in spring. The 12 calves were randomly allotted to 2 groups of 6 calves each. Group-1 calves were treated with an SR bolus designed to deliver 8 mg of ivermectin/d. Group-2 calves were nontreated controls. Cattle groups were kept in separate concrete-floored pens (grass hay nutrition) and slaughter was performed at 35 days after treatment. Fecal egg counts for group-1 calves remained zero after treatment, except for detection of less than 1 egg/g of feces in 1 calf at the time of slaughter; counts in nontreated calves increased. Mean and range of Ostertagia ostertagi inhibited larvae in nontreated calves were 27,093 and 10,622 to 56,368, respectively. Efficacy of the IVM SR bolus was 100% against O ostertagi developing fourth-stage larvae (L4) and inhibited early L4, Haemonchus placei adults, Cooperia punctata and C spatulata adult males, Cooperia spp adult females, Cooperia spp L4, Trichostrongylus colubriformis adults, Bunostomum phlebotomum adults, and Oesophagostomum radiatum adults. Efficacy for O ostertagi and T axei adults was 99.9%. Numbers of nontreated calves infected with C pectinata adult males and Oes radiatum L4 were too low to evaluate efficacy. Calves treated with the IVM bolus gained 10.2 kg, whereas nontreated calves lost 1.8 kg. Abomasal lesions were clearly greater in nontreated calves on the basis of index comparisons of abomasal weight and total live weight and gross pathologic features.     

Efficacy of oxfendazole against inhibited larvae of Ostertagia ostertagi acquired by calves in the spring

During the spring of 1985, 40 calves grazed pastures known to have high numbers of spring inhibition-prone, infective Ostertagia ostertagi larvae. Calves were removed from pasture and placed in outdoor pens with concrete floors from 10 days prior to treatment until necropsy 14 days after treatment. Ten calves were allocated to each of 4 treatment groups, and oxfendazole was administered to each group by intraruminal injection at dosages of 0, 2.25, 4.5, and 6.75 mg/kg of body weight. Efficacies greater than or equal to 94.6% were achieved at dosages of 4.5 and 6.75 mg/kg against adult Ostertagia spp, Trichostrongylus spp, Haemonchus placei, Cooperia punctata, Bunostomum phlebotomum, Oesophagostomum radiatum, and Dictyocaulus viviparus. Efficacy against inhibited larvae of O ostertagi was variable, with the highest efficacy (90.2%) attained at a dosage of 6.75 mg/kg.     

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.     

Anthelmintic activities of B1a fraction of avermectin against gastrointestinal nematodes in calves

Anthelmintic activities of the B1a fraction of avermectin were evaluated in a controlled experiment. Twenty 12-week-old calves artificially infected with gastrointestinal nematodes were allotted to four groups. Calves in group 1 were used as nonmedicated controls; other calves in groups 2, 3, and 4 were given (orally) B1a avermectin at dosage levels of 50, 100, and 200 microgram/kg of body weight, respectively. These treatments were given 35 days after calves were inoculated with infective nematode larvae. In groups 2, 3, and 4, overall reductions (based on geometric means) were 98.6%, 98.7%, and 98.4%, respectively. These reductions were highly significantly different (P less than 0.01) from the control calves. Nematodes in the calves were Haemonchus contortus. Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, and Oesophagostomum radiatum.     

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).     

Efficacy of albendazole for treatment of naturally acquired nematode infections in Washington cattle.

Albendazole, methyl 5-propylthio-1H-benzimidazol-2-yl carbamate, was given as a bolus (7.68 to 8.18 mg/kg of body weight) to cattle naturally infected with gastrointestinal nematodes and lungworms in a controlled trial. Over 99% of adult Ostertagia ostertagi, Trichostrongylus longispicularis, Cooperia oncophora, Nematodirus helvetianus, and Dictyocaulus viviparus were removed by the treatment. Efficacy against immature O ostertagi, early fourth-stage O ostertagi, and Oesophagostomum radiatum was 95.2%, 86.6%, and 96.7%, respectively. In a field trial, the same compound administered in a paste formulation (at approximately 7.5 mg/kg) eliminated over 99% of strongylin and Moniezia eggs from feces of treated cattle.     

High concentration of serum gastrin immunoreactivity and abomasal mucosal hyperplasia in calves infected with Ostertagia ostertagi and/or Trichostrongylus axei

Parasite-free, 4-month-old-calves were inoculated with Ostertagia ostertagi and/or Trichostrongylus axei, followed 6 weeks later by inoculation with increasing doses of O ostertagi for 8 weeks in the 2 groups (n = 4) of calves that had been given O ostertagi. Gastrin immunoreactivity concentration in serum was measured before and after infection and was correlated with changes in mucosal thickness. Gastrin immunoreactivity concentration in preinoculation control sera ranged from 95.2 to 287.1 pg/ml, and increased values were measured in all parasitized calves after 15 weeks. Significantly (P less than 0.05) increased serum gastrin immunoreactivity concentration compared with the preinfection value, was found in calves infected with O ostertagi or T axei, and highly significant (P less than 0.01) values were observed in calves infected with both parasites. Abomasal mucosal hyperplasia was observed in all parasitized calves; increased mucosal thickness and mucosal cross-sectional area were most prominent in calves infected with O ostertagi and T axei.     

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.