Efficacy of three broad-spectrum anthelmintics against gastrointestinal nematode infections of goats

Groups of 10 goats, harbouring both naturally acquired and experimental infections of gastrointestinal nematodes, were drenched with either levamisole (5 mg kg-1), albendazole (3.8 mg kg-1) or parbendazole (15 mg kg-1), or remained untreated. Haemonchus contortus was the numerically dominant infection, with Strongyloides papillosus, Trichostrongylus colubriformis and Oesophagostomum columbianum also present. At 5-6 days post-treatment, goats were killed and necropsied. Post-mortem worm counts showed that the reduction in mean total worm burdens was 57.4% in levamisole-treated animals, 71.1% in the albendazole group and 85.1% in the parbendazole group. Reductions for H. contortus were 80.2, 87.9 and 83.9% in the levamisole-, albendazole- and parbendazole-treated groups, respectively. These data indicate that the anthelmintics in question are not being applied at an adequate dose rate for goats, and/or resistance to anthelmintics is occurring in the field in Pernambuco State, northeast Brazil.     

Activity of febantel on natural infections of gastrointestinal helminths in lambs in a controlled test

The efficacy of febantel paste formulation (6 and 12 mg/kg) against natural infections of gastrointestinal helminths in lambs (n = 33) in Kentucky was evaluated in a controlled test. For the test, 23 lambs were treated orally (17 at 6 mg/kg and 6 at 12 mg/kg) and 10 lambs were not treated. Removals at both dosages in treated lambs were 95% to 100% for species of immature and mature Haemonchus, Trichostrongylus, and Cooperia; and mature Ostertagia females, Nematodirus, and Strongyloides. For immature Nematodirus, removals were 92% and 77% at the dosages of 6 and 12 mg/kg, respectively. Only a few specimens (av less than 100) of some other species or stages were found in the nontreated group and removal of them (at both dosages) were 94% to 100% for Ostertagia (immature and males), Strongyloides (immature), Oesophagostomum (immature), and Moniezia (mature); and 61% (at 6 mg/kg) and 100% (at 12 mg/kg) for Capillaria (mature), 0% for Trichuris (mature, at both dosages), and 67% (at 6 mg/kg) and 100% (at 12 mg/kg) for Oesophagostomum (mature).     

Activity of ivermectin against canine intestinal helminths

The anthelmintic activity of ivermectin was tested in 98 dogs against adult ascarids (Toxocara canis, Toxascaris leonina), hookworms (Ancylostoma caninum, A braziliense), and whipworms (Trichuris vulpis), and against experimentally induced infections (4th-stage larvae) of T canis and A caninum. Dosage levels tested were single subcutaneous injections of 50, 100, 200, or 400 micrograms/kg of body weight with appropriate vehicle-treated controls. A minimum of 4 (usually 5) dogs were tested with each parasite and dosage level. The lowest dosage level, 50 micrograms/kg, and all higher dosage levels expelled greater than 99% of the adult forms of both species of hookworms and intestinal larval forms of A caninum, as determined by worm counts at necropsy. A dosage level of 100 micrograms/kg was required to expel greater than 99% of whipworms and 200 micrograms/kg was necessary to expel adult (91%) and larval (97%) stages of T canis. Ivermectin was only marginally effective (34.2%, 46.2%, 69.2%, and 53.8%) against Toxascaris leonina at 50, 100, 200, and 400 micrograms/kg, respectively, and had no effect against occasional infections with the tapeworms, Dipylidium caninum (14 dogs) and Taenia spp (3 dogs).     

Efficacy of an in-feed ivermectin formulation against gastrointestinal helminths, lungworms, and sarcoptic mites in swine

The efficacy of ivermectin as an in-feed formulation was evaluated against naturally acquired gastrointestinal helminths, lungworms, and sarcoptic mites (experiment 1; n = 24) and against induced infection with intestinal nematodes (experiment 2; n = 24) in pigs. Treatments consisted of ivermectin administered in feed at concentrations calculated to provide 100 or 200 micrograms/kg of body weight/d for 7 days or of nonmedicated feed (controls) for 7 days. At concentration of 100 micrograms of ivermectin/kg/d, efficacy against naturally acquired infections was 97.7% for Ascaris suum, 97.8% for Metastrongylus spp, greater than 99% for Oesophagostomum spp, 100% for Macracanthorhynchus hirudinaceus, and 89.7% for Ascarops strongylina. Against induced infections (fourth-stage larvae), efficacy was 100% for A suum and 96.9% for Oesophagostomum spp. At concentration of 200 micrograms of ivermectin/kg/d, efficacy against naturally acquired infections was 100% for A suum, Hyostrongylus rubidus, Metastrongylus spp, and Ascarops strongylina; greater than 99% for Oesophagostomum spp; and 85.9% for Macracanthorhynchus hirudinaceus. Against induced infections (fourth-stage larvae), efficacy was 100% for A suum and 95% for Oesophagostomum spp. At concentrations of 100 and 200 micrograms of ivermectin/kg/d, efficacy against Sarcoptes scabiei var suis was evidenced by elimination of the mite by posttreatment day 14.     

Efficacy of eprinomectin pour-on against gastrointestinal nematode infections in sheep

Two field trials were conducted in two farms (farms A and B) in southern Italy, to assess the efficacy of eprinomectin applied topically at the dose rate of 500 micro g/kg to sheep with naturally occurring infections of gastrointestinal nematodes (GIN). The nematode population determined by necropsy consisted of Teladorsagia circumcincta, Haemonchus contortus, Trichostrongylus vitrinus, T. capricola, Nematodirus sp., and Chabertia ovina in sheep from farm A, and of T. circumcincta, T. vitrinus, T. capricola, T. colubriformis, and C. ovina in sheep from farm B. In each farm, 42 female sheep were assigned to a eprinomectin treated group (E-group) and a control untreated group (C-group) of 21 animals each. On farm A, the percentage reductions in strongyle faecal egg counts from E-group compared to C-group were 99.1% on day 10; 97.4% on day 30; and 67.0% on day 60. On farm B, on the same days, they were 95.4, 84.9, and 69.4%, respectively. In the course of the two trials, eprinomectin was well tolerated by all the animals with no adverse reactions following the topical treatment.     

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.     

Efficacy of thiophanate and albendazole against natural infections of Dicrocoelium dentriticum, Fasciola hepatica, and gastrointestinal nematodes and cestodes in sheep

The anthelmintic efficacy of thiophanate and albendazole was compared in sheep with heavy infestations of Dicrocoelium dentriticum. The effectiveness of each drug was determined by counting the numbers of D. dentriticum in animals killed 21 days after treatment. In one group, the dose of thiophanate recommended for use against gastrointestinal (GI) nematodes (50 mg kg-1 live weight) was found to be 74.4% effective against D. dentriticum. Two tablets (each containing 76 mg of active ingredient) of albendazole per 30 kg live weight were given to a second group and the dose repeated after 1 week. Under this regime, albendazole was found to be 12.7% effective against D. dentriticum. The effect of each drug on other parasites was as follows; thiophanate had no effect against Fasciola hepatica or cestodes, while albendazole was 71.5% effective against F. hepatica and 100% effective against cestodes. Both drugs were highly effective against GI nematodes.     

Efficacy, safety and palatability of a new broad-spectrum anthelmintic formulation in dogs

The efficacy, safety and palatability of a new flavoured chewable anthelmintic tablet were investigated in dogs. The efficacy, based on worm counts, of a single recommended therapeutic dose (RTD) of 5 mg pyrantel + 20 mg oxantel + 5 mg praziquantel/kg bodyweight was assessed in experimental infections (EI) and natural infections (NI) with Trichuris vulpis, Echinococcus granulosus and Toxocara canis. For T vulpis, the efficacy of the treatment was 99.3 per cent in EI (comparing groups of six treated and six control dogs) and 100 per cent in NI (nine treated and nine control dogs). For E granulosus, the efficacy was more than 99.9 per cent in EI (11 treated and 11 control dogs). For T canis, the efficacy was 94.3 per cent in EI (10 treated and 10 control dogs) and 100 per cent in NI (12 treated and 13 control dogs). In a field study, Ancylostoma caninum (11 dogs) and T canis (11 dogs) faecal egg counts were reduced by more than 99 per cent, and in eight dogs with Dipylidium caninum proglotides in the faeces the efficacy was 100 per cent. The tablets were readily consumed by 56 of 64 (87.5 per cent) privately owned dogs. Safety was assessed in groups of six dogs treated either once with twice the RTD, once with six times the RTD, with twice the RTD on three consecutive days, or untreated. There were no significant differences in blood parameters between the groups, and no abnormal clinical findings. Two dogs treated with six times the RTD vomited, but no vomiting was observed when administration was repeated two days later.     

Efficacy of moxidectin, nemadectin and ivermectin against an ivermectin-resistant strain of Haemonchus contortus in sheep.

The efficacies of ivermectin, nemadectin and moxidectin were evaluated when administered orally to lambs infected with either a susceptible laboratory strain of Haemonchus contortus or a strain reported to be resistant to ivermectin. Groups of 24 Dorset cross Cheviot cross Suffolk lambs were infected with either the susceptible or resistant strain of H contortus and allocated to treatment groups according to their faecal egg counts 27 days after infection. One day later the lambs were dosed orally with one of the three anthelmintics at 0.2 mg/kg bodyweight, and they were killed and surviving worms were recovered 13 or 14 days after treatment. Against the ivermectin resistant strain, ivermectin did not significantly reduce the egg count or the numbers of adult H contortus; however, both nemadectin and moxidectin reduced the nematode egg counts and the numbers of H contortus by 99 and 100 per cent, respectively. Against the susceptible strain, all the anthelmintics reduced the egg counts by 100 per cent as early as four days after treatment and reduced the numbers of susceptible H contortus by 100 per cent. No adverse reactions to any of the drugs were observed.     

Evaluation of oxfendazole against natural infections of gastrointestinal nematodes in Nigerian calves

The efficacy of oxfendazole was tested in naturally infected Sokoto-Gudali calves at a dosage of 2.8 mg per kg. At this dosage level, oxfendazole showed 100 per cent efficacy against adult and immature forms of Haemonchus spp, Trichostrongylus spp, Bunostomum phlebotomum and Oesophagostomum radiatum. Although efficacy of 100 per cent was recorded for the adult form of Cooperia spp, only 48 per cent reduction was recorded for its immature stages. Similarly, a percentage reduction of 75 was recorded for adult Trichuris spp. No larvae hatched out of a seven-day vermiculite culture of faeces collected from the treated calves 24 h after treatment.     

Epidemiology of gastrointestinal helminths infections in Dorper sheep in a semi-arid area of Kenya

A survey on the prevalence and intensity of infection with gastrointestinal helminths of Dorper sheep in relation to age and weather factors was carried out on a ranch in Kajiado district, a semi-arid area of Kenya for a period of 13 months (May 1999 to May 2000). Faecal samples from lambs (3 months to 1 year), yearlings (1-2 years) and adult breeding ewes (2-4 years) were examined for helminth egg output and helminth genus composition at 3-week intervals. The results indicated that the prevalence of strongyle and tapeworms infections were highest for lambs, followed by the adult breeding ewes and then for the yearlings. In all age groups the proportions of infected animals were higher during the wet season than in the dry season for both nematodes and tapeworms. The mean strongyle egg counts were higher during the dry season for lambs, but were higher during the wet season for the other age groups. Mixed strongyle infections were detected, with Trichostrongylus (55 %), Haemonchus (28 %), Cooperia (10.5 %) and Oesophagostomum (6.5 %) being the most frequently encountered genera throughout the study period. The trends in strongyle faecal egg counts indicated the occurrence of hypobiosis, with resumption of development towards the end of the dry season and at the onset of the short rains in October and November. Self-cure was also observed in September and November in all age groups, although less frequently in lactating ewes. The prevalence and intensities of infection with gastrointestinal helminths in this area appeared to be influenced by the age of the host and weather factors.     

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 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.