Critical tests with oxibendazole against gastrointestinal parasites of ponies.

Twenty ponies were allotted to 4 groups of 5 ponies each, and oxibendazole was orally administered at dose levels of 5, 10, 15, and 20 mg/kg. In the 3 groups of ponies given the largest doses, efficacy against 3 species of Strongylus was between 92 and 100% and that against small strongylids of the genera Cyathostomum, Cylicocyclus, Cylicodontophorus, and Cylicostephanus was more than 99%. All adults and 95 to 100% of larvae of the pinworm Oxyuris equi were removed. In the group of ponies given 5 mg/kg, 86 to 100% of the large strongylids and 84 to 100% of the small strongylids were removed, as were all larval and adult pinworms. Trichostrongylus axei was found only in 4 of the 5 ponies given 5 mg/kg; results were encouraging, but not consistent. Almost all of the Parascaris equorum were found in this group of ponies; no anthelmintic activity was detected at this dose level. Oxibendazole removed approximately 99% of small strongylid 4th-stage larvae. No efficacy against the larval stages of Gasterophilus intestinalis and against Habronema spp and Setaria equina was observed.     

Oxibendazole: critical anthelmintic trials in equids.

The efficacy of oxibendazole against gastrointestinal parasites of horses was evaluated by the critical test method. Naturally infected ponies of various ages were given single oral doses of 5, 10, or 15 mg-kg of bodyweight. The drug was highly effective against adult large strongylids (Strongylus vulgaris, S edentatus, S equins), adult small strongylids (especially species of the genera Cylicostephanus, Cylicocyclus, Cyaathostomum, and Triodontophorus), and adult and larval stages of the large pinworm, Oxyuris equi. There was no apparent dose-related differences in efficacy. Oxibendazole was less effective against fourth-stage small strongylid larvae than it was against adults. The drug was inactive against stomach bots (Gasterophilus spp), tapeworms (Anoplocephala magna and A perfoliata), lungworms (Dictyocaulus arnfieldi), abdominal worms )Setaria equina), and mature or immature nematodes in locations other than the lumen of the gastrointestinal tract.     

The efficacy of fenbendazole in the control of immature strongyle infections in ponies

The efficacy of fenbendazole against immature stages of Trichonema spp., Strongylus vulgaris and Strongylus edentatus was evaluated. Naturally infected 6 to 12 month old ponies were given single, oral doses of 0, 15, 30 and 60 mg/kg of body weight. A dose response relationship was noted between increasing dose levels and efficiency against larval trichonemes and migrating stages of S. vulgaris and S. edentatus. Dose levels of 30 mg/kg and higher removed 93 per cent of mucosal stages of Trichonema spp., while doses of 60 mg/kg removed 83 per cent and 89 per cent of the migrating larvae of S. vulgaris and S. edentatus respectively.     

Re-evaluation of ivermectin efficacy against equine gastrointestinal parasites.

Two trials were conducted to confirm the efficacy of ivermectin paste against endoparasites of horses. In these trials, 20 ponies were treated with ivermectin oral paste at 200 mcg x kg body weight once on Day 0, and 20 ponies served as unmedicated controls. The animals carried naturally acquired parasite infections as confirmed by pretrial fecal examination. The animals were necropsied for worm recovery on Days 14, 15 or 16. Parasites recovered were identified to species. Horses treated with ivermectin had significantly (P<0.05) fewer (>99.0% reduction) adult small strongyles (Coronocyclus spp including C. coronatus, C. labiatus, C. labratus; Cyathostomum spp including C. catinatum, C. pateratum; Cylicocyclus spp including C. ashworthi, C. elongatus, C. insigne, C. leptostomum, C. nassatus, C. radiatus; Cylicodontophorus bicoronatus; Cylicostephanus spp including C. asymetricus, C. bidentatus, C. calicatus, C. goldi, C. longibursatus, C. minutus; Gyalocephalus capitatus; Parapoteriostomum spp including P. euproctus, P. mettami; Petrovinema poculatum; Poteriostomum spp including P. imparidentatum, P. ratzii) and adult large strongyles (Strongylus edentatus, S. vulgaris; Triodontophorus spp including T. brevicauda, T. serratus; Craterostomum acuticaudatum) than the controls. Ivermectin was also highly effective (94% to >99%, P<0.05-0.01) against Gasterophilus intestinalis larvae, Habronema spp., Oxyuris equi, Parascaris equorum. The data from these two trials confirm that ivermectin paste administered to horses orally at 200mcg x kg(-1) continues to be highly effective for treatment and control of a broad range of small and large strongyle species as well as other species of gastrointestinal parasites.     

An evaluation of the efficacy of oxfendazole against the common nematode parasites of the horse.

In a controlled trial in naturally-infected young ponies, oxfendazole administered orally at dose-rates of 10 mg per kg and 50 mg per kg resulted in complete elimination of Trichostrongylus axei, Parascaris equorum, Oxyuris equi and adult Strongylus vulgaris. Also, all migrating Strongylus edentatus larvae recovered from the subperitoneal tissues of the flank were found to be dead. Minimum efficiencies of 99.8 per cent and 99.1 per cent were obtained against adult small strongyles (Trichonema spp) and 97.6 per cent and 100 per cent of developing small strongyle larvae at dose-rates of 10 mg per kg and 50 mg per kg respectively. Although the arterial lesions caused by migrating S vulgaris larvae were less severe in the treated compared with the untreated animals, reductions in mean larval numbers over controls were only in the region of 49 to 59 per cent.     

Controlled tests of activity of ivermectin against natural infections of migratory large strongyles and other internal parasites of equids

Four controlled tests (experiments A, B, C, and D) were conducted in naturally infected yearling equids to evaluate activity of ivermectin (0.2 mg/kg IM) against migrating Strongylus vulgaris and S edentatus in mesenteric arteries and ventral abdominal wall, respectively. Data were also obtained on activity against other internal parasites of the gastrointestinal tract and eyeworms. The type and number of equids in the experiments were as follows: experiment A-3 ponies, 2 treated and 1 non-treated; experiment B-4 mixed-bred horses, 2 treated and 2 nontreated; experiment C-5 mixed-bred horses, 3 treated and 2 nontreated; experiment D-4 mixed-bred horses, 2 treated and 2 nontreated. Intervals between treatment and necropsy were 35 days in experiment A, 52 to 53 days in experiment B, 38 to 41 days in experiment C, and 45 days in experiment D. Efficacious killing of retroperitoneal forms of S edentatus in the ventral abdominal wall was obtained in the 4 experiments. Only dead worms or fragments were recovered from treated animals, while living 4th-stage and/or 5th-stage S edentatus was present in nontreated equids in each test. A similar killing effect on S vulgaris in cranial mesenteric arteries was recorded in 2 experiments (B and D); only 1 dead 5th-stage worm was found in 1 of the treated yearlings in experiment B, whereas living 4th- and 5th-stages of S vulgaris were found in the nontreated controls in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effectiveness of oxfendazole against early and later 4th-stage Strongylus vulgaris in ponies

Twenty pony foals (reared worm free), 6.5 to 10 weeks of age, were inoculated with Strongylus vulgaris and allocated to 5 groups, each with 4 foals. One week after inoculation, 1 group of 4 foals was given oxfendazole (OFZ) at a dosage rate of 10 mg/kg of body weight, another group was given 2 such treatments 48 hours apart, and a 3rd group was given a placebo. All treatments were administered by stomach tube. Three weeks later, foals were euthanatized and necropsied in a test for efficacy against early 4th-stage larvae. Oxfendazole was 80% and 94.9% effective against early 4th-stage S vulgaris with 1 and 2 doses, respectively. A 4th group of 4 foals was given 2 treatments of OFZ, 48 hours apart, about 8 weeks after inoculation, and a 5th group was given a placebo. These foals were euthanatized and necropsied 5 weeks after treatment in a test for efficacy against later 4th-stage larvae. Two doses of OFZ were 96.6% effective against later 4th-stage larvae.     

Controlled test and clinical evaluation of dienbendazole against naturally acquired gastrointestinal parasites in ponies

A controlled test was performed to titrate the anthelmintic dosage of dienbendazole in 24 mixed-breed ponies naturally infected with Strongylus vulgaris, S edentatus, and small strongyle species, as determined by parasitic egg and larval counts in feces. Comparison of results of treatment was made among 3 dienbendazole dosages--2.5, 5, and 10 mg/kg of body weight--and a gum (excipient) mixture given by nasogastric intubation. All ponies were euthanatized and necropsied at 7 or 8 days after treatment. Trichostrongylus axei, Habronema muscae, S vulgaris, S edentatus, small strongyles, and Oxyuris equi were efficaciously eliminated in response to all doses of dienbendazole; Gasterophilus spp were not affected by any dose. There were not sufficient numbers of Draschia megastoma, Anoplocephala spp, or Parascaris equorum in the ponies to evaluate drug effect. Changes in the appearance of the intestinal lining were dose-dependent; in the ponies treated with 5 and 10 mg of dienbendazole/kg, the mucosa appeared clean and smooth, though in ponies given 2.5 mg/kg, it appeared clean, but was nodular and moderately reactive to embedded immature small strongyles. In the gum mixture-treated ponies, the large intestinal mucosa was inflamed, with edematous areas, in response to infections caused by large and small strongyles. A limited clinical titration was done in 12 ponies that were fecal culture negative for S vulgaris larvae, although other strongyles were detected. Two ponies in each of 6 groups were given the following dosages: 0 (gum mixture only), 0.5, 1, 2.5, and 5 mg of dienbendazole/kg. One group of 2 ponies was given 5 mg of fenbendazole/kg as a standard treatment control.(ABSTRACT TRUNCATED AT 250 WORDS)     

Critical test evaluation of butamisole against gastrointestinal parasites of horses and ponies.

A critical test was performed to evaluate the anthelmintic properties of an injectable butamisole formulation and to compare the efficiency with that of a commercially available piperazine-thiabendazole anthelmintic. The test was done in 10 horses and 15 ponies with naturally acquired parasitic infections. Butamisole was administered at the dose level of 2.5 or 3.75 mg/kg of body weight by either subcutaneous or deep intramuscular injection. Given at the dose level of 2.5 mg/kg, butamisole was highly effective (99%) against Strongylus vulgaris and moderately effective (49%) against Parascaris equorum. At the 3.75 mg/kg dose rate, butamisole was highly effective against both S vulgaris (97%) and P equorum (94%). Butamisole had limited efficacy against other parasite species. Signs of toxicosis, long-term swelling of the injection sites, or tissue damage were not seen after injection.     

Evaluation of four forms of oxfendazole against nematodes of cattle.

Oxfendazole, methyl [5-(phenylsulfinyl)-1H-benzimidazol-2-yl] carbamate, was evaluated in calves naturally infected with endoparasites. The compound was used as a drench, a paste, a bolus, and as top-dress crumbles at a dosage of 2.5 mg/kg of body weight. The four formulations produced similar effects and were 99% to 100% effective in removing the following adult parasite genera: Haemonchus, Ostertagia, Trichostrongylus. Cooperia, Bunostomum, Oesophagostomum, and Dictyocaulus. Mean efficacy against Trichuris spp varied from 87% to 95%, depending on the formulation used.     

Critical tests in equids with fenbendazole alone or combined with piperazine: particular reference to activity on benzimidazole-resistant small strongyles

Seven critical tests in equids were conducted with single doses of fenbendazole (5 mg kg-1) alone (Panacur--American Hoechst, Somerville, NJ); (2 tests with paste and 1 with suspension formulation) or in combination with piperazine (American Hoechst); (40 mg base kg-1); (4 tests with paste formulation). The main purpose of the tests was evaluation of activity against benzimidazole-resistant small strongyles (Cyathostomum catinatum, Cyathostomum coronatum, Cylicocyclus nassatus, Cylicostephanus goldi, and Cylicostephanus longibursatus). Natural infections of 2 populations of benzimidazole-resistant small strongyles were evaluated; 1 was population B in 2 horses and the other was population S in 5 ponies. Removal of the 5 species of population B was 49-91% in the animal treated with fenbendazole paste alone and 100% (4 of these species present) in the animal treated with the combination. For population S, 2 of the 5 resistant species were present in small numbers in 1 animal treated with fenbendazole paste alone and all were removed; the 1 animal receiving fenbendazole suspension alone had removals of 0-70% for the 5 benzimidazole-resistant species. Also for population S, the 5 resistant species were present in 2 animals treated with the paste combination and removal was 98-100% and of 4 of the 5 resistant species in 1 animal, removal was 76-99%. Removal of large strongyles (Strongylus vulgaris and Strongylus edentatus) was 92-100% for fenbendazole paste alone or in combination with piperazine in the 5 infected animals. For Oxyuris equi, present in 1 animal treated with the combination, there was 91% removal of immature and 100% removal of mature specimens. There probHably was no activity by fenbendazole alone or the combination against bots, tapeworms, and parenteral stages of S. vulgaris and S. edentatus. The combination may have had some activity against immature Habronema spp. and mature abronema muscae.     

Benzimidazole resistance of equine stronygles--critical tests of six compounds against population B

Critical tests were conducted on eight horses naturally infected with several species of large and small strongyles from population B. Tested were six benzimidazoles, including thiabendazole (2 lots) (44 mg/kg of body weight); mebendazole (8.8 mg/kg); cambendazole (two formulations) (20 mg/kg); fenbendazole (10 mg/kg); oxibendazole (10 mg/kg); and oxfendazole (10 mg/kg). All compounds were administered by stomach tube except one of the two cambendazole formulations which was an intraoral paste. Removal of large strongyles (when present), Strongylus vulgaris and Strongylus edentatus, was 100% by each drug. In general, five species of small strongyles (Cyathostomum catinatum, Cyathostomum coronatum, Cylicocyclus nassatus, Cylicostephanus goldi, and Cylicostephanus longibursatus) exhibited varying degrees of resistance (% removal) to all of the drugs except oxibendazole. A total of 19 other species of small strongyles from seven genera, including the three described earlier were about 100% removed by the six benzimidazoles. Poor removal of immature (fourth-stage larvae) forms was also characteristic of the six drugs.     

Use of oxibendazole for control of cambendazole-resistant small strongyles in a band of ponies: a six-year study

Oxibendazole (OBZ; 10 mg/kg of body weight) was administered to ponies at 8-week intervals to control strongylosis in a breeding band of Shetland-type ponies (n = 29 to 50) from October 1978 through September 1984. A similar use of cambendazole (CBZ; 20 mg/kg of body weight) in this band of ponies during the preceding 4-year period resulted in the survival of a CBZ-resistant population (S) of small strongyles. Effectiveness of OBZ treatments was monitored by pre- and posttreatment counts of the number of strongyle eggs per gram of feces (epg) and of the number of strongyle larvae per gram of feces (lpg). For the first 4 years of the 6-year period, epg and lpg counts were determined for 3 to 5 of the OBZ treatments; during the last 2 years, counts were determined for each treatment. For the 1st year, the mean reduction in epg was 96%. During the 2nd and 3rd years, mean reductions in epg were 80% and 81%, respectively. For the 4th and 5th years, mean reductions in epg were 69% and 43%, respectively. For the 6th year, the mean reduction in epg was 37%. Statistical analyses of the epg data, using the linear plateau method, indicated a significant increase in residual (surviving) strongyle infections after the periodic OBZ treatments, with a mean annual increase in survival of 10.3% for the 6 years. Changes in lpg were variable, but an overall loss of effectiveness of the OBZ treatments was evident. Only infective larvae of small strongyles were observed in the cultures; larvae of 2 species of large strongyles, Strongylus vulgaris and Strongylus edentatus, were conspicuously absent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficacy of oxfendazole against inhibited Ostertagia ostertagi in naturally infected cattle.

Oxfendazole was administered to pregnant cows at 2.5 and 5 mg/kg body weight to determine the anthelmintic efficacy against naturally acquired larvae which became inhibited at the early 4th stage. The experimental design included three groups of orally-treated cows, that is, 10 placebo treated control cows, 11 cows treated with 2.5 mg/kg of oxfendazole and 10 cows treated with 5.0 mg/kg of oxfendazole. Oxfendazole at 2.5 mg/kg body weight was 82 and 94% effective against EL-4 and adult O. ostertagi, respectively. At 5 mg/kg, Oxfendazole was 95 and 99% effective against EL-4 And adult O. ostertagi, respectively. The results suggested the use of a field dosage level of 5 mg/kg body weight oxfendazole where inhibited larvae may be encountered.     

Activity of closantel in the prevention of Gasterophilus and Strongylus vulgaris larval infections in equine foals and yearlings

Two controlled tests were conducted in equine foals and yearlings to determine the optimal oral dosage and the duration of activity of closantel for the prevention of Gasterophilus spp larval infections. Additional data were collected on the activity of closantel against Strongylus vulgaris larval infections. In experiment 1, 12 foals and 12 yearlings were equally allocated to 4 experimental groups, and were given oral treatments with closantel at dosages of 0 (nontreated controls), 2, 5, or 8 mg/kg of body weight every 2 months during bot season. The foals and yearlings were allowed to graze on open pasture throughout the experiment to provide a natural source for bot and helminth infections. All animals were euthanatized and necropsied 6 weeks after the final treatment. Closantel was highly effective (98.6% to 100%) at all doses in preventing Gasterophilus spp larval infections in the foals, but only the 8 mg/kg dose had significant (P less than 0.05) activity (99.7%) in the yearlings. This dose also significantly reduced the numbers of 4th-stage and immature adult S vulgaris (86.0%) in the mesenteric arteries as compared with nontreated controls. In experiment 2, 9 foals and 9 yearlings received a single oral treatment of 8 mg of closantel/kg of body weight; 3 foals and 3 yearlings were kept as nontreated controls. Groups of 6 treated (3 foals, 3 yearlings) and 2 control (1 foal, 1 yearling) animals were euthanatized and necropsied 1, 2, and 3 months after treatment. Closantel remained effective for 2 months in preventing infections of G intestinalis larvae in these foals and yearlings. Clinical signs of toxicosis were not observed in the treated animals of either study.     

Critical and controlled tests of activity of moxidectin (CL 301,423) against natural infections of internal parasites of equids.

The activity of moxidectin was evaluated in 1988 and 1989 against natural infections of internal parasites in 20 critical tests (n = 20 equids) and three controlled tests (n = 20 equids). Two formulations, injectable administered intramuscularly (i.m.) or intraorally (i.o.) and gel i.o., were given at dose rates of 0.2, 0.3 or 0.4 mg kg-1 body weight. For the critical tests (all three dose rates evaluated), removals of second instar Gasterophilus intestinalis were 93-100%, except (89%) for the injectable formulation (i.m.) at 0.2 mg kg-1. Removals of third instar G. intestinalis were 88-100% for the injectable formulation given i.m. or i.o. and 93-100% for the gel formulation, except (53%) for one batch (0.4 mg kg-1). Activity was 100% for third instar Gasterophilus nasalis, Parascaris equorum, Strongylus vulgaris and Strongylus edentatus. For Oxyuris equi, removals were 91-100%, except (27%) for one batch of the injectable formulation given i.o. at 0.3 mg kg-1. There was apparent activity against migrating S. vulgaris and S. edentatus at various dose rates and routes of administration for both formulations. At necropsy, there were local reactions observed at the injection site of three equids. In the controlled tests, dose rates were 0.2 or 0.4 mg kg-1. Removal of third instar G. intestinalis was highest for the injectable formulation given i.m. All formulations and dose rates were highly effective against S. vulgaris and S. edentatus, but variable and incomplete against O. equi. Removal was excellent on Habronema muscae and on migrating S. vulgaris and S. edentatus, although incomplete on S. vulgaris. Gasterophilus nasalis third instars and P. equorum were present in low numbers in some non-treated equids, but none were recovered from treated equids. Toxicosis was not evident.     

Efficacy of ivermectin in injectable and oral paste formulations against eight-week-old Strongylus vulgaris larvae in ponies

A controlled test method was used to evaluate the efficacy of injectable micelle and oral paste formulations of ivermectin (22,23-dihydroavermectin B1) against 8-week-old Strongylus vulgaris larvae in experimentally infected pony foals. The dosage level of the drug in both formulations tested was 0.2 mg/kg. Ponies were euthanatized and necropsied 5 weeks after treatment. Based on the recovery of live vs dead S vulgaris from mesenteric arteries, both formulations were greater than 99% effective. Increased weight gains and marked reductions in the severity of arterial lesions were observed in treated ponies.     

Controlled test evaluation of the benzimidazole anthelmintic VET 220-S alone or with concomitant trichlorfon treatment against naturally acquired gastrointestinal parasites in ponies

A controlled test was done in 30 naturally infected ponies to evaluate the antiparasitic activity of the dienbendazole analog VET 220-S given alone or with trichlorfon (TCF) by nasogastric intubation. Six ponies were nontreated; 6 were given VET 220-S (5.0 mg/kg); 6 were given TCF (40 mg/kg); 6 were given VET 220-S (2.5 mg/kg) and TCF (40 mg/kg); and 6 were given VET 220-S (5.0 mg/kg) and TCF (40 mg/kg). All ponies were euthanatized and necropsied 7 or 8 days after treatment. Draschia megastoma, Oxyuris equi, Strongylus vulgaris, S edentatus, and small strongyles were removed efficaciously by all doses of VET 220-S. Habronema muscae and microfilariae of Onchocerca cervicalis were not removed by VET 220-S or TCF. Gasterophilus intestinalis was 97.9% removed by TCF. Pregnant mares in all groups were not adversely affected by treatment, except for 1 mare that had diarrhea after TCF treatment. Parasite eggs per gram and larval culture data agreed with necropsy data.     

Fenbendazole in equids: further controlled tests with emphasis on activity of multiple doses against naturally occurring infections of migratory large strongyles

Two controlled tests (experiments D and E) were done to evaluate a fenbendazole (FBZ) paste dosage regimen (10 mg/kg once a day for 5 days) for activity against naturally occurring infections of migrating Strongylus vulgaris and S edentatus in the mesenteric arteries and ventral abdominal wall, respectively. Data were also obtained on other internal parasites of the gastrointestinal tract and eyes in experiment E. Eight pony yearlings were used in experiment D (4 treated and 4 nontreated) and 6 horse weanlings were used in experiment E (3 treated and 3 nontreated). Intervals, expressed as days between treatment and necropsy of animals, were 42 (n = 1) or 52 (n = 7) for experiment D and 52 or 53 for experiment E. Animals were on pasture during all or a portion of post-treatment intervals of both experiments. Efficacious killing of retroperitoneal forms of S edentatus in the ventral abdominal wall was observed in both experiments. The average numbers of live 4th-stage forms in equids were 0.0 (treated) and 2.25 (nontreated) for experiment D and 2.0 (treated) and 1.7 (nontreated) for experiment E. The average numbers of 5th-stage S edentatus were 0.5 (treated) and 4.0 (nontreated) for experiment D and 1.3 (treated) and 23.3 (nontreated) for experiment E. Fragments of dead specimens of S edentatus were also found in nodules in treated animals in both experiments, but not in nontreated animals. Consistency of the retroperitoneal lesions provided additional evidence of the killing action of the FBZ treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum protein changes in ponies on different parasite control programmes

Serum protein responses were examined in 52 ponies divided into five groups and subjected to various control strategies that resulted in pasture infectivity ranging from 706 to 18,486 infective third stage, cyathostome and Trichostrongylus axei larvae per kilogram of herbage (L3/kg) by 17 September 1984. Major protein changes occurred only in young ponies (Groups 4 and 5) and were observed before exposure to maximum numbers of pasture larvae (Group 4; 10,210 L3/kg, Group 5: 10,042 L3/kg) on 17 September. It appeared that a primary infection of T axei was a greater stimulus to serum beta-globulin and immunoglobulin (Ig)G(T) responses that provided by continued infection with cyathostome (small strongyle) worms. The large strongyles (Strongylus vulgaris, S edentatus and S equinus) were not detected in any larval cultures or on pastures grazed by the young ponies. A fall in beta-globulin and IgG(T) concentrations of Group 5 ponies one month after treatment with ivermectin indicated a larvicidal action against T axei and/or the cyathostomes. A subsequent rise in serum albumin concentrations of Group 5 ponies suggested that a protein-losing gastroenteropathy had been alleviated by the larvicidal action of ivermectin. Mature control ponies (Group 1) showed little beta-globulin response and only a modest IgG(T) response in six of the 10 ponies after exposure to heavily infected lawns (18,486 L3/kg) in September 1984. It was concluded that serum protein and IgG(T) responses were of limited value as an aid to diagnosis of parasitism because of numerous difficulties of interpretation.