Effectiveness of ivermectin paste for removal of nematodes in the horse

Thirteen Standardbred horses, two to five years of age, were treated with ivermectin paste per os at 200 μg/kg of body weight and 13 were untreated. Two weeks after treatment, previously untreated horses were given the paste. Fecal samples were collected from all horses at the time of treatment and periodically thereafter up to 14 weeks and were examined for nematode eggs using the Cornell-McMaster dilution and the Cornell-Wisconsin double centrifugation procedures.

All horses consumed the paste readily and had no signs of toxicosis. Strongyle eggs were found in the feces of all horses before treatment but not at two to three weeks after treatment. At five to six weeks after treatment only two horses had eggs in the feces. At eight, ten, 12 and 14 weeks after treatment 27, 69, 88 and 100% of the horses examined, respectively, had a few strongyle eggs but these were no greater than 18% of that of the pretreatment samples. Ivermectin oral paste, therefore, appeared to be highly effective against both adult and immature strongyles.

     

Comparison of ivermectin, oxibendazole, and pyrantel pamoate in suppressing fecal egg output in horses

Thirty resident horses at a boarding stable in Alberta were used to evaluate the relative efficacies of ivermectin, oxibendazole, and pyrantel pamoate in reducing fecal egg output in adult horses under routine management conditions during spring and early summer, and to more clearly define the duration of suppression of fecal egg production following anthelmintic treatment. Horses were blocked according to pretreatment egg counts and randomly assigned to one of three treatments: pyrantel pamoate at 6.6 mg/kg body weight; oxibendazole at 10 mg/kg body weight; or ivermectin at 200 μg/kg body weight. All treatments were administered orally as a paste on day 0.Fecal samples were collected for examination by the modified Wisconsin procedure before treatment, and then at 4-11 day intervals up to day 72.

Very few if any strongyle eggs were found in the feces of any horses up to day 35. On days 42, 50 and 57, the geometric mean egg count for the ivermectin group was significantly (p<0.05) lower than that for the oxibendazole or pyrantel pamoate groups. Based on a survival curve analysis of the data, the mean number of days for recurrence of eggs in the feces was significantly longer for the ivermectin group than for the oxibendazole and pyrantel pamoate groups.

Under conditions encountered in this study, the posttreatment interval to resumption of fecal egg out-put in horses treated with ivermectin was eight to nine weeks, compared with five to six weeks for horses treated with oxibendazole or pyrantel pamoate.

     

The persistence of benzimidazole-resistant cyathostomes on horse farms in Ontario over 10 years and the effectiveness of ivermectin and moxidectin against these resistant strains

Three clinical trials with fecal egg count reduction tests and coproculture were conducted on 2 standardbred farms in Ontario. On Farm A, the treatment groups were mebendazole and ivermectin in trial 1, and fenbendazole and moxidectin in another. On Farm B, treatment groups were mebendazole and ivermectin. All horses treated with mebendazole or fenbendazole were subsequently treated with ivermectin or moxidectin. Strongyle eggs/g feces were estimated pre- and post-treatment using the Cornell-McMaster dilution and Cornell-Wisconsin centrifugal flotation techniques. After treatment, there was no change in the arithmetic mean eggs/g feces for horses given mebendazole, and a reduction of only 49.1% for those given fenbendazole. All horses receiving ivermectin or moxidectin had their egg counts reduced to 0. Only cyathostomes were found on culture. On both farms the benzimidazole resistant strains appeared to have persisted for at least 10 years. Development of and monitoring for anthelmintic resistance are briefly discussed.     

Effects of continuous ivermectin treatment from birth to puberty on growth and reproduction in dairy heifers.

The effect of continuous ivermectin treatment from birth to puberty on growth and reproductive performance was studied in Holstein heifer calves grown on pastures in comparison to naturally nematode-infected, untreated animals. Ivermectin effectively abated the presence of nematode eggs in feces. Eggs per gram (EPG) in parasitized animals increased rapidly from wk 12 to 18 of age and then decreased. Animals treated with ivermectin grew faster than untreated ones, and differences in body weight became significant at 6 wk of life, even before eggs appeared in the feces of either treatment group. Ivermectin-treated heifers reached puberty 3 wk earlier than infected ones as assessed with serum progesterone concentrations (ivermectin, 30.4 +/- .8 vs untreated, 33.7 +/- 1.3 wk of age). This delay was not directly related to body weight. In addition, pelvic area at 39 wk and at 15 mo of age was increased in treated heifers (8 and 11%, respectively) compared with parasitized animals. No differences in the wither heights were observed. We conclude that ivermectin treatment in dairy heifers may increase growth rate during development, advance the onset of ovarian function, and positively affect yearling pelvic area.     

Field efficacy of ivermectin plus praziquantel oral paste against naturally acquired gastrointestinal nematodes and cestodes of horses in North America and Europe

The efficacy of an oral formulation of ivermectin plus praziquantel in the reduction of nematode and cestode egg counts in horses was assessed in 273 horses under field conditions at 15 sites in North America (n = 6) and Europe (n = 9). Horses were confirmed by fecal examination to have natural infections of strongyles (100%) and tapeworms (76%). Replicates of four horses were formed at each site, and in each replicate three animals received ivermectin (0.2 mg/kg body weight) plus praziquantel (1 mg/kg body weight) oral paste and one animal remained untreated or received vehicle paste. Fecal samples were collected for fecal nematode and cestode egg counting before and 7, 8, 9, 14, 15, and 16 days after treatment. Horses treated with ivermectin plus praziquantel oral paste had significantly (P <.01) lower posttreatment strongylid and cestode egg counts (reductions of 98% or more) than controls. Combined site analyses revealed that 95% or 96% of the horses positive for cestode eggs before treatment that were treated with ivermectin plus praziquantel were negative for cestode eggs at each posttreatment fecal examination. No adverse reactions attributable to ivermectin plus praziquantel oral paste treatments were observed. The results of the studies demonstrated that ivermectin plus praziquantel paste was highly effective in reducing egg shedding by gastrointestinal nematodes and cestodes, and no adverse reactions were observed in horses treated under field conditions.     

Preliminary Analysis of the Results of Selective Therapy Against Strongyles in Pasturing Horses

Control of horse parasites often omits application of measures to eradicate the free-living stages in pastures and frequently relies on chemotherapy only. Selective therapy was used for Spanish Sport horses grazing either in the same pasture (continuous) or in rotated meadows. In each group, equines exceeding a cutoff value of 300 strongyle eggs per gram of feces received ivermectin or moxidectin. Efficacy of the treatment was assessed by estimating reduction of fecal egg counts and the number of horses shedding parasite eggs (PHR). Coprocultures revealed presence of the cyathostomins Cyathostomum and Gyalocephalus spp. In all treated groups, a 100% value for both reduction of fecal egg counts and PHR against cyathostomins was obtained, and PHR values ranged from 100% to 12%. The longest strongyle egg reappearance period was observed in horses undergoing rotation grazing and receiving ivermectin (9 weeks), compared with a 6-week period recorded for the other treated equines. Our results seem to point that the efficacy of selective therapy in equine herds could be reduced if the horses with fecal egg counts below the threshold value (thus not receiving chemotherapy) remain grazing in the same pastures with the treated ones. It is strongly suggested that interested parties consider performing periodic fecal analyses to monitor fecal egg counts, together with the percentage of horses passing eggs in feces, to improve the effect of this procedure.     

A comparison of two programs (pyrantel tartrate administered daily and 3X pyrantel pamoate adminitered at 8-week intervals) for the reduction of tapeworm EPG in the horse

A 26-week study was conducted with 24 horses to compare the effectiveness of two different treatment regimens in reducing the number of tapeworm eggs per gram (EPG) of feces. Ten horses were treated daily with 2.6 mg/kg of pyrantel tartrate (approved normal dosage for nematodes). Eleven horses received pyrantel pamoate at 8-week intervals at 19.8 mg/kg (3X the normal use for nematodes). Three horses served as controls and received ivermectin at 8-week intervals. Levels of tapeworm EPG were monitored at 2-week intervals for the duration of the 26-week period of study. Prior to administration of the first treatment, all 24 horses had positive EPG counts. Following the second week of treatment, no tapeworm eggs were detected in fecal samples of the 10 horses treated with pyrantel tartrate. Of the 11 horses treated with 3X pyrantel pamoate at 8-week intervals, one to two at each sample collection date had positive tapeworm EPG counts through the tenth week following the initial treatment, that is, through two weeks following the second 3X pyrantel pamoate treatment. Of the three control horses treated only with invermectin, at least one, and sometimes all three, had positive EPG counts at each collection date, indicating continuous tapeworm infection.     

The efficacy and acceptability of ivermectin liquid compared to that of oral paste in horses

One hundred-twenty horses and ponies ranging in age from 142 days to 23 years were used to assess the efficacy and acceptability of ivermectin liquid for horses when given as an oral drench or by nasogastric intubation. Prior to treatment, animals in this study were found to have eggs in the feces of one or more of the following: strongyle type, Parascaris equorum, and Strongyloides westeri. While egg parasite per gram (EPG) numbers from 30 untreated controls remained consistently positive over a 14 day period, parasite EPG numbers from animals treated on Day 0 were reduced to 0 by day 14 as determined by a modified McMaster technique.     

Demonstration of the sustained anthelmintic activity of a controlled-release capsule formulation of ivermectin in ewes under field conditions in New Zealand

Ten field trials were conducted in the North and South Islands of New Zealand to evaluate the anthelmintic efficacy of an intraruminal controlled-release capsule formulation of ivermectin. A total of 810 Coopworth, Perendale, Romney or Coopworth ' Romney ewes, weighing on average 42-70 kg, were used. Ewes were either untreated or treated shortly before lambing in late winter-early spring (eight trials) or in late spring (two trials) with an ivermectin controlled-release capsule which delivers ivermectin at 1.6 mg per day for 100 days (minimum dose rate 20microg/kg/day). Bodyweights, faecal nematode egg counts and dag scores were determined before treatment and at about 2 and/or 4, 6 or 8, 10 or 12, 14 and 16 weeks after treatment. Ewes treated with the ivermectin controlled-release capsule gained on average 1.1kg more than untreated sheep over the 16 weeks of the trials, but this difference was not significant (p > 0.10). Before treatment, faecal strongylid egg counts were equivalent (p > 0.10), but at each time point thereafter, egg counts in ivermectin controlled-release capsule treated sheep were significantly lower (p < 0.01; p < 0.05 at Week 2). Dag scores were not different at the start of the trial (p > 0.10), but at the end of the trial ivermectin controlled-release capsule treated ewes had significantly lower scores (p < 0.01) than untreated ewes. These findings indicated that treated animals shed significantly fewer nematode eggs and therefore pasture contamination with nematode eggs should be significantly reduced for at least 112 days. The control of dags should result in reduced direct losses due to the decreased value of dag wool, and indirect losses due to the cost of dagging sheep and the cost associated with the treatment and control of flystrike initiated by dags in the breech area.     

Field efficacy of ivermectin, fenbendazole and pyrantel embonate paste anthelmintics in horses

Three anthelmintic pastes were compared in terms of their ability to suppress the output of parasite eggs in the faeces of 108 grazing horses at four sites in Britain; the horses were treated once with either ivermectin, fenbendazole or pyrantel. At each site, the horses grazed together throughout the trials which took place during the summers of 1985 and 1986. The median periods before parasite eggs reappeared in faeces were 70 days for ivermectin, 14 days for fenbendazole and 39 days for pyrantel embonate. Geometric mean faecal egg counts in the groups treated with ivermectin and pyrantel were significantly less (P less than 0.05) than in the fenbendazole group on days 21, 28, 35 and 42 after treatment. On days 49, 56, 63 and 70 the mean egg counts in the ivermectin group were significantly lower (P less than 0.05) than those in either of the other groups. The results indicated that in order to ensure minimal contamination of pastures, grazing horses treated with ivermectin paste would have required a second treatment approximately 10 weeks after the first, and to achieve similar control with fenbendazole or pyrantel embonate, a second treatment would have been required after approximately two weeks and six weeks, respectively.     

Identification of foals infected with Parascaris equorum apparently resistant to ivermectin

During September 2002, routine fecal examinations performed on 16 Thoroughbred foals residing on a farm outside Toronto, Ontario, Canada, revealed low to moderate numbers of Parascaris equorum eggs in feces from 9 of the 16. All foals were then treated with ivermectin at a dose of 220 to 280 microg/kg (100 to 127 microg/lb), p.o., and fecal egg counts were repeated 12 days later. Fecal P. equorum egg counts increased between the first and second fecal examination in 7 foals, were unchanged in 1, and decreased in 5. Fecal samples were collected 13 days after treatment from 21 additional foals that had been treated with ivermectin at the same dose, and P. equorum eggs were detected in 12 of the 21. For all 37 foals, high P. equorum egg counts (> or = 100 eggs/g of feces) 12 to 13 days after ivermectin treatment were significantly more likely in foals that had been regularly treated with ivermectin since birth and permanently resided on the farm, compared with foals that had been treated with other anthelmintics or had an unknown deworming history. Collectively, these data suggested that P. equorum in these foals was resistant to ivermectin administered at the recommended dose.     

Alternative antiparasitic treatment of horses with pyrantel pamoate suspension and ivermectin oral solution compared with horses treated only with ivermectin

A practical parasite control program was evaluated in a 2-year clinical trial using pyrantel pamoate suspension (PYR) and ivermectin oral solution (IVM) in a seasonal rotation program, in comparison with continued use of IVM given at 2-month intervals. At least 15 horses in each of 2 treatment groups were distributed over 8 locations. In the alternation program, IVM was given twice (October, December) during the botfly (Gasterophilus spp.) season and again in April to treat against the lighter botfly season and to kill existing Onchocerca microfilariae prior to heavy Culicoides swarming. Pyrantel was given in February, June and August to continue suppression of strongyle infections and to treat against potentially developing Anoplocephala infections. In the program of IVM continuous use, the drug was given on the same schedule as either treatment on the alternation program.The course of strongyle infections was monitored by fecal sample analyses (EPG) at semimonthly intervals and by larval cultures of treatment pairs prepared at each treatment interval (alternation program) or at 4-month intervals (continuous IVM program). The strongyle egg count numbers were reduced to zero by the first IVM treatment, increased only slightly by the next treatment at 2 months, and repeated the reduced pattern with each treatment for 2 years. The alternation program in the first year had typical responses to each drug: IVM reducing strongyle EPG counts to zero which increased slightly at 2 months, followed by the PYR treatment, which reduced the strongyle egg counts for 4 weeks with rebound at 6 and 8 weeks. At the end of the first year and into the second, the IVM treatments of October and December established a zero or low strongyle EPG pattern which continued through the spring with PYR and IVM treatments. The second summer PYR treatments then maintained far better cyathostome control than had been reported for this drug. There may be a complementary or enhancing effect by prior treatment with ivermectin within the rotation protocol. The practical therapeutic compatibility between these 2 antiparasitics became obvious. Anoplocephala eggs were found in feces of some horses treated with IVM only, but no Anoplocephala eggs were found in post-treatment feces of horses treated on the alternation program.Strongyle larval cultures prepared as treatment pairs indicated high efficacy by ivermectin throughout the 2 years whether used alone or as a rotational drug, with improved cyathostome control by pyrantel pamoate. The combined use of EPG determinations and concurrent larval cultures in anthelmintic evaluations provide a greater spectrum of reliable results than from parasite egg counts alone.     

Alternative antiparasitic treatment of horses with pyrantel pamoate suspension and ivermectin oral solution compared with horses treated only with ivermectin oral solution

A practical parasite control program was evaluated in a 2-year clinical trial using pyrantel pamoate suspension (PYR) and ivermectin oral solution (IVM) in a seasonal rotation program, in comparison with continued use of IVM given at 2-month intervals. At least 15 horses in each of 2 treatment groups were distributed over 8 locations. In the alternation program, IVM was given twice (October, December) during the botfly (Gasterophilus spp.) season and again in April to treat against the lighter botfly season and to kill existing Onchocerca microfilariae prior to heavy Culicoides swarming. Pyrantel was given in February, June and August to continue suppression of strongyle infections and to treat against potentially developing Anoplocephala infections. In the program of IVM continuous use, the drug was given on the same schedule as either treatment on the alternation program.The course of strongyle infections was monitored by fecal sample analyses (EPG) at semimonthly intervals and by larval cultures of treatment pairs prepared at each treatment interval (alternation program) or at 4-month intervals (continuous IVM program). The strongyle egg count numbers were reduced to zero by the first IVM treatment, increased only slightly by the next treatment at 2 months, and repeated the reduced pattern with each treatment for 2 years. The alternation program in the first year had typical responses to each drug: IVM reducing strongyle EPG counts to zero which increased slightly at 2 months, followed by the PYR treatment, which reduced the strongyle egg counts for 4 weeks with rebound at 6 and 8 weeks. At the end of the first year and into the second, the IVM treatments of October and December established a zero or low strongyle EPG pattern which continued through the spring with PYR and IVM treatments. The second summer PYR treatments then maintained far better cyathostome control than had been reported for this drug. There may be a complementary or enhancing effect by prior treatment with ivermectin within the rotation protocol. The practical therapeutic compatibility between these 2 antiparasitics became obvious. Anoplocephala eggs were found in feces of some horses treated with IVM only, but no Anoplocephala eggs were found in post-treatment feces of horses treated on the alternation program.Strongyle larval cultures prepared as treatment pairs indicated high efficacy by ivermectin throughout the 2 years whether used alone or as a rotational drug, with improved cyathostome control by pyrantel pamoate. The combined use of EPG determinations and concurrent larval cultures in anthelmintic evaluations provide a greater spectrum of reliable results than from parasite egg counts alone.     

Effect of fenbendazole and ivermectin on development of strongylate nematode eggs and larvae in calf feces.

Thirty-nine weaned steer calves (mean weight 284 kg) were maintained under dry-lot conditions and assigned (based on fecal nematode egg count) to one of three treatment groups of 13 animals each as follows: control (no treatment), fenbendazole (5 mg kg-1), and ivermectin (0.2 mg kg-1). Fecal samples were collected 12 h before treatment, at treatment, and 12, 24, 48 and 72 h after treatment for determination of nematode eggs per gram, and (after culture) infective larvae per gram and population distribution. The effect of treatment on egg development was observed in feces collected 12 and 24 h after treatment. There was essentially no difference in efficacy, based on egg counts, of fenbendazole and ivermectin. Egg count was reduced 100% by both anthelmintics at 72 h after treatment. Viability, based on percent of eggs reaching the infective larval stage, of developing stages at 12, 24, and 48 h after fenbendazole treatment was 0.1%, 1.1%, and 0%; after ivermectin treatment the corresponding values were 23.7%, 30.1%, and 28.6%, respectively. Fenbendazole treatment resulted in little or no development of eggs and/or larvae in feces deposited 12 and 24 h after treatment, whereas development proceeded normally (compared with the control group) in ivermectin treated feces. Population distribution of infective larvae was predominantly Haemonchus and Cooperia with some Ostertagia and Oesophagostomum.     

Anti-strongyle activity of a propylene glycol-glycerol formal formulation of ivermectin in horses (mares)

Four groups of 10 horses (mares) each were treated with a 1% solution of ivermectin (200 micrograms/kg of body weight) in a propylene glycol-glycerol formal base orally, a 1% solution of ivermectin (200 micrograms/kg) in a propylene glycol-glycerol formal base via nasogastric tube, a 1.87% paste of ivermectin (200 micrograms/kg) orally, or a 22.7% paste of oxibendazole (10 mg/kg) orally. Fecal examinations were done before treatment and on posttreatment days (PTD) 14, 28, 42, 56, and 70. Strongyle egg per gram counts and sugar flotation fecal examinations were performed. Results of fecal examinations before treatment were similar in all horses. All horses treated with ivermectin had similar percentages of reductions in mean strongyle egg per gram counts after treatment; 100% on PTD 14, 28, and 56 and 93.4% to 98.7% on PTD 70. All ivermectin treatment groups had 0 horses detected as passing strongyle eggs on PTD 14 and 28, 0 to 2 on PTD 42, 3 to 5 on PTD 56, and 8 to 9 on PTD 70. Horses treated with oxibendazole had 99.9%, 99.7%, 92.9% 78.6%, and 54.5% reductions in mean strongyle egg per gram counts and 5, 7, 8, 9, and 9 horses detected as passing strongyle eggs on PTD 14, 28, 42, 56, and 70, respectively. Adverse reactions to treatment were not observed.     

Expulsion of small strongyle nematodes (cyathostomin spp) following deworming of horses on a stud farm in Sweden

This study was conducted on a stud farm in Sweden to investigate the species composition of cyathostomins expelled in the faeces of horses after deworming using three different anthelmintic preparations. Twenty-seven horses excreting > or = 200 strongyle eggs per gram faeces (EPG) were divided into three comparable groups and dewormed on day 0 with either of following compounds: 0.2 mg ivermectin per kg body weight (bw), 19 mg pyrantel pamoate per kg bw or 7.5 mg fenbendazole per kg bw. For each of the 3 days following anthelmintic treatment faeces was collected from individual horses and subsamples were fixed in formalin. Four days after the anthelmintic treatment all horses were re-treated with ivermectin and faeces was collected on day 5. Individual subsamples from each of the four sampling occasions were examined for cyathostomin nematodes. Sixty-three to 270 worms per horse were identified to the species level. The majority of the worms recovered were expelled during the first day from horses treated with ivermectin or pyrantel pamoate, and during the second day from horses treated with fenbendazole. Fifteen cyathostomin species were identified and the six most prevalent were Cylicocyclus nassatus, Cyathostomum catinatum, Cylicostephanus longibursatus, Cylicocyclus leptostomus, Cylicostephanus minutus and Cylicostephanus calicatus. These species composed 91% of the total burden of cyathostomins. The number of species found per horse ranged from 6 to 13, with an average of 9. No significant differences in species composition or distribution were found between the treatment groups. On day 5, i.e. 1 day after the last ivermectin treatment, 93% of the adult worms were recovered from horses in the fenbendazole group.This study showed that it was possible to identify cyathostomins expelled in faeces of dewormed horses, and that the most prevalent species corresponded to those found in autopsy surveys performed in other countries.     

Clinical trial of efficacy of ivermectin pour‐on against gastrointestinal parasitic nematodes in silvopasturing horses

The aim of this study was to assess, by a clinical trial, the efficacy of an ivermectin‐based pour‐on treatment against gastrointestinal parasitic nematodes in naturally infected horses using 2 groups of mature indigenous Pura Raza Galega grazing mares. Faecal and blood samples were collected individually over a 21 week period. Faeces were analysed by the coprological flotation, sedimentation and migration techniques. Changes in circulating blood cells were monitored over the study period. The administration of the ivermectin suppressed the eggelimination of ascarids and pinworms throughout the study and no strongyle‐eggs were observed in the treatment group between the 3rd and 10th weeks. The numbers of red cells increased significantly after the anthelmintic therapy, and a statistical reduction in circulating leucocytes was recorded. No side effects were observed. The pour‐on ivermectin formulation was highly successful against gastrointestinal nematodes and appears to be a useful therapeutic routine for large groups of horses.     

Demonstration of the sustained anthelmintic efficacy of a controlled-release capsule formulation of ivermectin in weaner lambs under field conditions in New Zealand

Ten field trials were conducted in the North and South Islands of New Zealand to evaluate the anthelmintic efficacy and production responses attributable to treatment of weaner lambs with an intra-ruminal controlled-release capsule formulation of ivermectin. A total of 800 Coopworth, Perendale and Romney lambs weighing on average 20.8-34.8 kg were used. Lambs were either untreated or treated shortly after weaning with an ivermectin controlled-release capsule which delivers ivermectin at 0.8 mg per day for 100 days (minimum dose rate 20 microg/kg/day). Bodyweights, faecal nematode egg counts and dag scores (assessment of faecal soiling in the breech area) were determined before treatment and at about 4,8, 12, 14 and 16 weeks after treatment. Sheep treated with the Ivermectin capsule gained significantly more weight (11.6 kg) over the 16 weeks of the trials compared to untreated sheep (7.3 kg) (p < 0.01). Before treatment, faecal strongylid and Nematodirus spp. egg counts were equivalent (p > 0.10) but, at each time point thereafter, egg counts in ivermectin capsule-treated sheep were significantly lower (p < 0.01 or p < 0.05). Dag scores were not different at the start of the trial (p > 0.10), but at the end of the trial control sheep had significantly greater dags (p < 0.05) than sheep treated with the ivermectin capsule. These findings indicate that treated animals contributed significantly fewer nematode eggs to the contamination of pasture and therefore pasture contamination should be significantly reduced for at least 112 days. The productivity of the ivermectin capsule-treated sheep over the I6 weeks of the trials was also significantly increased compared to salvage-treated controls. Furthermore, the presence of dags, which predispose sheep to blowfly strike in the breech area and result in production losses due to the costs of dagging and downgrading of breech wool, were also significantly (p < 0.05) reduced in the ivermectin capsule-treated sheep.     

Efficacy of injectable and pour-on microdose ivermectin in the treatment of goat warble fly infestation by Przhevalskiana silenus (Diptera, Oestridae)

The prophylactic efficacy of microdoses of injectable and pour-on ivermectin formulations against larval stages of Przhevalskiana silenus was assessed in naturally infected goats in the region of Calabria (southern Italy).Sixty-eight goats from two goat farms were divided into five groups: one group remained untreated, while the other four groups were treated with microdoses of ivermectin (5 and 10 microg/kg injectable formulation and 10 and 20 microg/kg pour-on formulation).The microdoses of ivermectin were fully effective in the treatment of goat warble fly infestation (GWFI) as no larvae emerged from the warbles in the treated groups, while all the larvae emerged in the control groups. Irrespective of the type of formulation used, the difference between the treated groups and the control group was statistically significant (P< 0.001). By contrast, no statistical differences were found between the goats treated with the injectable formulation and those receiving the pour-on applications, and between the two doses of the injectable and pour-on formulations used. Given the plasma concentrations it attains at its lowest dose (0.052 - 0.042 ng/ml for the injectable formulation and 0.030 ng/ml for the pour-on) the injectable formulation seems to offer the most reliable route for the administration of ivermectin microdoses and it is acceptable for milk consumption. The introduction of ivermectin in the early eighties and the use of microdoses in some cases have made it possible to control cattle hypodermosis in large areas of Europe. As with cattle hypodermosis, the administration of ivermectin microdoses in goats is particularly interesting because of the low costs involved and the low levels of residues found in goat milk; it may thus constitute the basis for GWFI control campaigns in areas where the disease is prevalent.     

Determining Treatment to Control Two Multidrug-Resistant Parasites on a Texas Horse Farm

A study was undertaken at the Texas A&M Horse Center to evaluate and compare the effectiveness of three anthelmintics—ivermectin, fenbendazole, and a combination of ivermectin and pyrantel pamoate—on fecal egg count reductions of cyathostomes and Parascaris equorum in 30 naturally infected foals. The foals were randomized into three treatment groups, with individuals being rerandomized after each 8-week observation period. The treatments of ivermectin and fenbendazole were given at the manufacturer's recommended doses, and the pyrantel treatment was given at two times the manufacturer's recommended dose. Fecal egg counts were performed at the time of treatment and at 2-week intervals after treatment for a total of 8 weeks. Each foal received a total of three treatments during the course of the study. Fecal egg counts were performed by a modified McMaster's test, with a sensitivity of 25 eggs per gram of feces, and by the modified Wisconsin double centrifugal flotation technique, with a sensitivity of 0.2 eggs per gram of feces. Fecal egg reduction percentages were calculated. Analysis of the results showed that ivermectin, either used alone or with pyrantel, was a more effective anthelmintic for cyathostome (small strongyle) control than fenbendazole. Fenbendazole and pyrantel showed a higher initial reduction in Parascaris egg counts when compared with the ivermectin-only-treated group, but this difference lessened over time. The use of the combination treatment showed the best results for controlling both parasites, indicating that a combination of anthelmintics may be necessary to control parasites on some equine farms.