The efficacy of an imidacloprid/moxidectin combination against naturally acquired Sarcoptes scabiei infestations on dogs

The study was undertaken to evaluate and compare the efficacy of an imidacloprid (10% w/v)/moxidectin (2.5% w/v) combination (Advocate Bayer HealthCare, Animal Health) with that of selamectin for the treatment of Sarcoptes scabiei on dogs. Thirty naturally infested dogs, of which one was later withdrawn because of distemper, were allocated to two equal groups and individually housed. The dogs in each group were treated twice, four weeks apart, with either the combination product (0.1 mL/kg body weight) or with selamectin (0.05 mL/kg body weight) administered topically. Skin scrapings were made every 14 days over a period of 50 to 64 days after the first treatment to quantify mite numbers. Clinical signs and the extent of sarcoptic lesions were assessed on each dog when skin scrapings were made. Efficacy was based on the presence or absence of mites, supported by clinical signs associated with canine sarcoptic mange. From Day 22 and onwards no Sarcoptes mites were found in the skin scrapings of any of the treated dogs. Treatment with the imidacloprid/moxidectin formulation or with selamectin was highly effective against Sarcoptes scabiei and resulted in an almost complete resolution of clinical signs within 50 to 64 days after the initial treatment.     

Field efficacy of moxidectin in dogs and rabbits naturally infested with Sarcoptes spp., Demodex spp. and Psoroptes spp. mites

The efficacy of moxidectin 1% injectable for cattle was evaluated in dogs and rabbits with naturally acquired sarcoptic, demodectic or psoroptic mites. Twenty-two dogs with generalised demodicosis were orally treated with 0.4mg/kg moxidectin daily. Forty-one dogs suffering from sarcoptic mange were treated with 0.2-0.25mg/kg moxidectin either orally or subcutaneously every week for three to six times. Seven rabbits were treated orally with 0.2mg/kg moxidectin twice 10 days apart. Of the 22 dogs with demodicosis, 14% were stopped treatment because of side effects, 14% were lost and of the remaining 72% all were cured (mean therapy duration 2.4 months). Thirty-seven of the sarcoptic mange-infected dogs finished treatment and were cured. In 17% of dogs, side effects were noted. All seven rabbits treated for psoroptic mange were cured and did not show any side effect. Our results indicate that moxidectin is effective and a good alternative for the treatment of demodicosis and scabies in dogs and psoroptic mange in rabbits. Side effects seem to occur more frequently if applied subcutaneously, therefore the oral route should be preferred.     

Efficacy of moxidectin against sarcoptic mange and effects on milk yield of ewes and growth of lambs

Forty-eight dairy ewes and 45 lambs naturally infested with sarcoptic mange, were divided into three equal groups and treated with moxidectin 1% inj. sol. at a dose rate of 0.2 mg moxidectin kg(-1) bodyweight once or twice ten days apart. During the study, the skin lesions were scored and the number of mites recovered in facial skin scrapings from the animals were recorded. Moxidectin was found to be effective against ovine sarcoptic mange, when given twice; the percentage reduction of mites was 100% (p < 0.0001) and the skin lesions disappeared completely (p = 0.0001). In sheep treated once only, the percentage reduction of mites varied from 75% to 92%. Treated ewes produced up to 22.4% more milk than the infested ones (p = 0.0001). Treated lambs had up to 15% greater final weight and up to 23.7% more growth than infested controls (p = 0.0001). It is concluded that two injections of moxidectin 1% inj. sol. at a dose rate of 0.2 mg kg(-1) bodyweight, given ten days apart, were effective against ovine sarcoptic mange. Furthermore, it is considered that sarcoptic mange adversely affects the production of the infested animals.     

Efficacy of a long-acting formulation of ivermectin against Psoroptes ovis (Hering, 1838) on cattle

A study was conducted in cattle experimentally infested with Psoroptes ovis to compare the prophylactic control against P. ovis provided by a long-acting injectable formulation of ivermectin to that of a commercially available injectable formulation of doramectin. Thirty Holstein steers were used. Animals were allocated by restricted randomization based on Day 0 body weight, forming six replicates of five animals each. Within each replicate, one animal was randomly allocated to one of the following treatment groups, with ivermectin and doramectin administered subcutaneously where indicated: (1) untreated controls; (2) ivermectin long-acting injectable (LAI) 630 mcg/kg, 56 days before challenge; (3) ivermectin LAI 630 mcg/kg, 42 days before challenge; (4) ivermectin LAI 630 mcg/kg, 35 days before challenge; or (5) doramectin 200 mcg/kg, 35 days before challenge. Animals were housed in individual pens 1 week prior to treatment. All animals were experimentally infested with P. ovis mites in the area between the shoulders, on the same day. Live mites were counted in scrapings from mange lesions at 2 sites on each animal 14, 21 and 28 days after challenge. Live mites were found in 33, 67 and 83% of the untreated controls on each respective evaluation. No P. ovis mites were found in steers treated with ivermectin LAI. Those animals showed lower (P < 0.05) mite counts than untreated controls on evaluations conducted 21 and 28 days after challenge. These results indicate that the ivermectin long-acting injectable formulation prevents induced infestations by P. ovis for at least 56 days after treatment. Doramectin injectable formulation, used at 200 mcg/kg, did not have a prophylactic effect 35 days after treatment.     

Sarcoptes scabiei var. suis in a closed pig breeding and fattening herd and control possibilities after treatment

On an Austrian pig breeding and finishing farm containing 13,000 pigs a mange prevalence of 38.7% according to the results of the skin scraping and 28.2% based on serology was determined. Due to the insufficient treatment (single treatment of the sows using Phoxim [Sebacil pour on]), sustainable control was impossible. That could be confirmed by the high number of mange positive gilts and finishing pigs. Before eradication started the following prevalences of mange could be found: sows 6.74% (skin scrapings), respectively 6.18% (serologically), gilts 18.18% resp 28.67%, finishing pigs 54.35% and 38.58%. The breeding stock for eradication was treated with doramectin (Dectomax) injectable solution and the finishing pigs with Ivomec-praemix, both applied twice. The success of treatment of the different farm units and of different age groups was controlled for the following ten months by combined diagnostic methods. In addition to skin scrapings, serum and colostral samples were carried out using a commercially available ELISA licensed for investigation of blood serum and colostrum. After treatment antibodies in the serum of the sows and gilts and Sarcoptes mites in their skin scrapings were detectable for up to four months after treatment. In serum samples of piglets and colostrum samples antibodies against Sarcoptes mites were detectable up to five months after final treatment. Due to the higher level and longer verifiability of antibodies in blood samples of piglets for five months after treatment and high prevalences their use as a diagnostic tool can be recommended. In contrast the use of colostral samples for routine diagnosis should be investigated more thoroughly. The comparison of the results of different diagnostic methods showed that for reliable mange diagnosis combined methods are recommended.     

Use of doramectin for treatment of notoedric mange in five cats

Five of 16 cats belonging to the same owner were brought to the veterinary hospital because of a 30-day history of signs of intense pruritus and alopecic and erythematous areas with bloody crusts. Notoedric mange was diagnosed and confirmed by microscopic examination of skin scrapings of all 5 cats. The remaining cats did not have clinical signs of mange, and Notoedres cati were not observed after microscopic examination of skin scrapings. A decision was made to treat all 16 cats with doramectin subcutaneously. In each cat, 0.1 ml of a 1% solution of doramectin was administered s.c. Body weights ranged from 2.9 to 7.1 kg (6.4 to 14.2 lb) in the 16 cats and the final doses varied from 143 to 345 micrograms/kg (65 to 157 micrograms/lb) of body weight, with a mean (+/- SD) of 270.4 +/- 64 micrograms/kg (122.9 +/- 29.1 micrograms/lb). The mean dose for the 5 affected cats was 292.2 +/- 44.8 micrograms/kg (132.8 +/- 20.4 micrograms/lb), with a range of 208 to 333 micrograms/kg (94.6 to 151.4 micrograms/lb). Lesions began to recede 1 week after treatment. Fifteen days after treatment, all 5 affected cats were clinically normal. Findings in our cats suggest that a single mean dose of doramectin of approximately 290 micrograms/kg is sufficient to control notoedric mange in cats.     

Persistent efficacy of doramectin and ivermectin against experimental infestations of Sarcoptes scabiei var. suis in swine

Two studies were performed to compare the persistent efficacy of doramectin and ivermectin in swine experimentally infested with Sarcoptes scabiei var. suis. In the Study 1, 84 pigs were treated with doramectin, ivermectin, or saline solution on Day 0. Pigs were then challenged with mites on Days 0, 7, 14, 21, 28, 35, or 42. Weekly evaluations were performed for 5 weeks following challenge with mites. Weekly evaluations included physical examination for clinical signs of sarcoptic mange and collection of skin scrapings for determination of mite counts. In the Study 2, 80 pigs were treated with doramectin, ivermectin, or saline solution on Day 0, and challenged with mites on Days 3, 6, 9, 12, 15, 18, 21, 24, or 27. Weekly evaluations were performed for 6 weeks after challenge exposure. All negative-control (saline-treated) animals in both studies developed evidence of mite infestation. In the Study 1, doramectin prevented mite infestations 7 days longer than ivermectin. Results from the Study 2 indicated that the persistent efficacy of doramectin was 18 days on the basis of mite recovery. This was twice as long as the persistent efficacy of ivermectin, which was 9 days on the basis of mite recovery.     

Comparative therapeutic effect of moxidectin,doramectin and ivermectin on psoroptes mites infestation in buffalo (<Emphasis Type="Italic">Bubalus bubalis</Emphasis>)

The aim of the present study was to carry out comparative therapeutic effect of moxidectin pour on, doramectin and ivermectin on psoroptes infestation in buffalo. A total of 318 buffalo in 77 small scale herds suspected to have mange mites were examined clinically and parasitologically. Fifty-three (16.66%) buffalo in 25 herds were recorded to be infested; 51 (16.35%) with psoroptic mites, and two (0.31%) with chorioptic mites. Buffalo with psoroptic mites were randomly allocated into three groups (17 buffalo each). First group was treated with moxidectin pour on at a dose rate of 0.5 mg kg^-1. The second group received doramectin (200 μg kg^-1 twice subcutaneously, 14 days apart). The third group received ivermectin (200 μg kg^-1 twice subcutaneously, 14 days apart). Adjunct to each drug, deltamethrin was applied to the surrounding environment twice at a two week interval. Treatment outcomes of 51 buffalo with psoroptic mites showed that moxidectin pour on and doramectin had a significant higher effect on mite count reduction (MANOVA, P < 0.01; Walks^, Lambda, P < 0.01) and clinical sum scores (MANOVA, P < 0.05; Walks^, Lambda, P < 0.05) compared with injectible ivermectin. On clinical level, the number of clinically recovered buffalo in moxidectin and doramectin treated groups was significantly (P < 0.05) higher than that of ivermectin treated group. The result of the present study indicated that psoroptic mites are the main cause of mange in buffalo in Lower Egypt. This is the first report that describes the effect of moxidectin in buffalo. Moxidectin is a good alternative and easily applied drug for treatment of psoroptes infestation in buffalo.     

米尔贝肟对自然感染疥螨病犬的治疗效果

为了评价米尔贝肟对临床自然感染疥螨犬的治疗效果,选用自然感染疥螨犬65例,随机选择5条服用伊维菌素,另外60条随机分为3组,分别服用高剂量(2g/kg体重)、中剂量(1g/kg体重)、低剂量(0.5g/kg体重)的米尔贝肟。给药后2、14、28、42d和56d,刮取皮屑,检查螨虫和虫卵,同时观察临床症状。试验结束时米尔贝肟高剂量组、伊维菌素组的无螨虫犬的比例和螨虫的下降率均为100%,临床症状如红疹、结痂、过度角化等现象均消失,所有动物毛发都开始大范围重生;米尔贝肟中、低剂量组结果稍差。米尔贝肟按2g/kg体重剂量,每周1次,连续用药3周,给药对自然感染疥螨病犬有很好的治疗效果。     

Comparative evaluation of two ivermectin injectable formulations against psoroptic mange in feedlot cattle

A study was carried out to compare the efficacy of two injectable formulations of ivermectin, Ivomec,(1) Merial (IVM reference) and Ivogell,(2) Intervet (IVM generic) in the treatment of psoroptic mange (Psoroptes ovis) in Charollais feedlot cattle. A total of 22 animals were ranked in order of the severity of mange and allocated to 11 replicates of 2 animals each. Within each replicate, one animal was randomly allocated to IVM reference product treatment (Group 1) and one to IVM generic (Group 2). Animals were treated on Day 0 and on Day 8 at the recommended dosage of 200 microg ivermectin/kg bodyweight. The pharmacokinetics profiles (pK) of both IVM formulations were evaluated in plasma samples taken from 6 cattle randomly chosen per group on Day 0, before treatment, and then at 6, 12, 24 hours and daily from Day 2 to Day 7 after the treatment on Day 0. Additionally, the severity of mange lesions was assessed and mites were counted in skin scrapings on Days 0, 8, 15 and 25. Animals were weighed on Day 0 and 25 and body weight and average daily gains (ADG) were evaluated. No statistical differences were found between the cattle of the two groups in any pK parameters, although the mean IVM plasma concentrations in cattle treated with the IVM reference product were consistently higher than those found in cattle treated with the generic compound. By Day 25, all animals in Group 1 had recovered clinically and parasitologically from psoroptic mange while cattle from Group 2 still had mange lesions and, in two animals, living mites were found in the skin scrapings; these differences were significant (P<0.001). The mean body weight of the two groups was significantly different on Day 25 (P<0.01) when animals in Group 1 weighed 20 kg more than those in Group 2. In conclusion, despite similarities in their pharmacokinetic profiles and formulations, the clinical efficacy of the two injectable formulations of IVM differed significantly in their therapeutic efficacy against psoroptic mange in feedlot cattle up to 25 days after treatment: this difference in response was reflected in an incomplete clinical and parasitological response in Group 2 and a slower growth rate.     

Efficacy of topical administration of eprinomectin for treatment of ear mite infestation in six rabbits

Six rabbits naturally infested with Psoroptes cuniculi were treated topically on the skin at the base of the neck with 0.5 mg kg(-1) of 0.5% pour-on eprinomectin for cattle, twice at 14-day intervals. Efficacy of the drug was based on the disappearance of clinical signs and the absence of live mites for a period of 6 weeks. Clinical improvement was seen within 3 days of the first application; however, complete recovery of clinical signs and elimination of mites in 5/6 rabbits did not occur until the end of the study. No adverse reactions attributable to eprinomectin treatment were observed during the observation period. Results of this trial indicated that eprinomectin was partially effective in the treatment of psoroptic mange in rabbits.     

Oral administration of moxidectin for treatment of murine acariosis due to Radfordia affinis

A field trial was conducted to assess the safety and efficacy of oral administration of moxidectin in mice naturally infected with the fur mites Radfordia affinis. The natural infection was diagnosed in two colonies within a large academic institution by direct hair examination. Animals received moxidectin (1% Cydectin, FortDodge) at an oral dosage of approximately 2 mg/kg body weight by micropipette; administration was repeated after 15 days. Forty mice served as an untreated control group. Moxidectin treatment resulted in clinical improvement within a few days after initial treatment, and mites were eradicated from all infested animals at day 30. No side effects or signs of ill health were observed in any of the treated animals. To our knowledge, this is the first report of oral moxidectin for treatment of murine acariosis.     

Efficacy of a novel formulation of metaflumizone plus amitraz for the treatment of sarcoptic mange in dogs

A novel spot-on formulation containing metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated for efficacy against sarcoptic mange mites in naturally infested dogs. Sixteen dogs were allocated to two equal groups and were housed individually. Eight of the dogs were treated topically with metaflumizone plus amitraz at the proposed minimum dose rate (20mg/kg of each of metaflumizone and amitraz, at a dose volume of 0.133ml/kg) on Days 0 and 28. The other eight were treated with metaflumizone plus amitraz at the proposed minimum dose rate on Days 0, 14, 28 and 42. To enumerate Sarcoptes scabiei mites, skin scrapings were taken on each of Days 2, 14, 28, 42 and 56. Clinical signs of mange and the extent of sarcoptic lesions were evaluated on each dog when scrapings were made. Evaluation of the efficacy of the treatment was based on the absence of mites supported by the absence of clinical signs associated with canine sarcoptic mange. Treatment with metaflumizone plus amitraz at the minimum proposed dose rate at monthly (two treatments) or two-weekly (four treatments) intervals resulted in a rapid reduction of mites and improved clinical signs. The overall cure rates at Day 56, based on zero mite counts and/or resolution of clinical signs were 75% and 83% of dogs for the monthly and two-weekly regimens, respectively.     

Efficacy of a novel formulation of metaflumizone plus amitraz for the treatment of demodectic mange in dogs

A novel spot-on formulation containing metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated for efficacy against demodectic mange mites in naturally infested dogs. Sixteen dogs were allocated to two equal groups and individually housed. Eight of the dogs were treated topically with metaflumizone plus amitraz at the proposed minimum dose rate (20mg/kg of each of metaflumizone and amitraz, 0.133ml/kg) on Days 0, 28, and 56. The other eight were treated with metaflumizone plus amitraz at the proposed minimum dose rate on Days 0, 14, 28, 42, 56, and 70. Mite numbers were estimated from skin scrapings taken on Days -3 to -1, 28, 56, and 84. Clinical signs of mange and the extent of demodectic lesions on each dog were evaluated when skin scrapings were conducted. Efficacy of the treatment was based on a reduction in mite numbers and an assessment of the clinical signs associated with canine demodectic mange. Treatment at monthly or two-weekly intervals for 3 months resulted in a rapid reduction in mite numbers (>94 and >99% for the monthly and two-weekly treatments, respectively) and an improvement in clinical signs. Success rates, based on zero mite counts in skin scrapings at Day 84 were 42.9 and 62.5% of dogs for the monthly and two-weekly regimens, respectively.     

Transmission of Sarcoptes scabiei in Swine by Fomites

Transmission of sarcoptic mange by fomites was investigated by placing mange-free piglets in pens for either fixed or variable periods of time during the first six days following removal of mange infected swine. Transmission occurred in pigs with as little as 24 hours exposure to fomites. Clinical signs of pruritis and focal erythematous skin lesions developed in various pigs from four and a half to 13 weeks after exposure. Pigs with the longer exposure developed clinical signs more rapidly than those with a shorter exposure. Four of six pigs developed a chronic form of the disease characterized by thickened encrustations and scurf from which mites were readily demonstrated. The remaining two pigs developed only the pruritic form and mites were never found in numerous skin scrapings examined.     

Use of selamectin for the treatment of psoroptic and sarcoptic mite infestation in rabbits

Selamectin, a novel avermectin compound, was evaluated for its efficacy against naturally occurring infestations of Psoroptes cuniculi and Sarcoptes scabiei. A total of 42 New Zealand rabbits with psoroptic mange and 37 Angora rabbits with sarcoptic mange were used in the present study. On day 0, infested rabbits were treated topically with either selamectin at minimum dose of 6 mg kg(-1) (6-18 mg kg(-1) for New Zealand rabbits, n = 31 and 10-12 mg kg(-1) for Angora rabbits, n = 23) or vehicle only (control groups, n = 11 for New Zealand rabbits, n = 14 for Angora rabbits). The efficacy of selamectin was assessed both clinically and parasitologically by the presence or absence of viable mites. Rabbits were scraped for sarcoptic mites on days 7, 14, 28, 42 and 56 and had otoscopeic and/or microscopic examination for the detection of Psoroptes mites on days 7, 14, 42 and 56. Fisher's exact test was used to assess differences between the vehicle and selamectin treatment in the number of rabbits without mites (cure rates) on each assessment date. It was found that significantly fewer selamectin-treated rabbits had mites detected on skin scrapings (for S. scabiei) or otoscopeic and/or microscopic examination (for P. cuniculi) (P < 0.01) than the vehicle group. Results of the present study suggest that selamectin is effective against naturally infestations of P. cuniculi and S. scabiei in rabbits.     

Comparative study of doramectin and fipronil in the treatment of equine chorioptic mange

In equids, chorioptic mange is a common dermatitis for which there are no licensed medications in the uk. Doramectin and fipronil are licensed for the control of ectoparasites in other species and were evaluated for the treatment of 17 cases of chorioptic mange in 13 equids. Equids were included if clinical findings were indicative of chorioptic mange, chorioptes mites were positively identified and concurrent disease that could affect response to disease was not evident. A random number table was used to allocate subjects to receive doramectin (group D, eight animals) or fipronil (group F, nine animals). Each of the horses in group D were given 0.3 mg/kg doramectin (Dectomax; Pfizer) on two occasions 14 days apart by subcutaneous injection. All limbs of the horses in group F were sprayed with fipronil 0.25 per cent solution (Frontline; Merial) to the level of the stifles and elbows. Both groups were examined on the day of treatment and 14 and 28 days later to assess the behavioural signs of pruritus and the severity of the dermatological lesions. Acetate tape impressions were collected from the distal limbs and the degree of mite infestation was assessed. By day 28 there were no behavioural signs of chorioptic mange in any of the animals, and there were significant reductions in the numbers of mites in both groups. However, there were no significant reductions in the mean lesion score in either group. There was no significant difference between the effectiveness of the two treatments.     

Sarcoptic mange in three alpacas treated successfully with amitraz

Sarcoptic mange is a serious skin disease in alpacas that can result in high morbidity and even mortality. Three alpacas were presented with sarcoptic mange that had previously failed to respond to repeated topical applications of eprinomectin, and an injection of doramectin. They were moderately to severely pruritic, had extensive lesions of alopecia, erythema, scaling and crusting, and had lost weight. As no drug is currently licensed for the treatment of sarcoptic mange in alpacas in the UK, they were treated with a topical solution of amitraz (50 mL in 10 L) after initial bathing with antibacterial or keratolytic shampoos. The clinical signs completely resolved with no relapse over a 10-month follow-up period. In this small group of alpacas, amitraz was an effective and well-tolerated treatment for sarcoptic mange.     

Eprinomectin treatment of psoroptic mange in hunter/jumper and dressage horses: a prospective, randomized, double-blinded, placebo-controlled clinical trial

The purpose of this prospective, double-blinded, placebo-controlled clinical trial was to investigate the efficacy of topical eprinomectin for the treatment of psoroptic mange infestation in horses. 24 privately owned hunter/jumper and dressage horses were diagnosed with psoroptic mange infestation based on physical findings and skin scraping results were enrolled and randomly assigned to either topical eprinomectin pour-on solution (at a dose of 500mug/kg body weight weekly once for four applications) treatment group or a placebo group (purified water). Clinical evaluations and skin scrapings were done by the same veterinary investigator at the beginning, during and at the end of the treatment. Both owners and veterinary investigator were blinded to the allocation to the groups. The efficacy of eprinomectin was assessed both clinically and parasitologically by the presence or absence of viable mites. Horses were scraped for psoroptic mites on days 7, 14, 21, 28 and 40 for follow-up. Fisher's exact test was used to assess differences between the eprinomectin treatment and placebo in the number of horses without mites (cure rates) on each assessment date. It was found that significantly fewer eprinomectin treated horses had P. equi mites detected on skin scrapings (p<0.01) than the placebo group. In conclusion, eprinomectin was effective and safe therapy against natural infestations of P. equi in the horses included in this study.     

The difference in efficacy of ivermectin oral, moxidectin oral and moxidectin injectable formulations against an ivermectin-resistant strain of Trichostrongylus colubriformis in sheep

AIM: To evaluate the efficacy of ivermectin oral, moxidectin oral and moxidectin injectable formulations against an ivermectin-resistant strain of Trichostrongylus colubriformis in sheep. METHODS: Twenty-four mixed breed lambs were infected with 15,000 infective third-stage larvae of an ivermectin-resistant strain of T. colubriformis which had originally been isolated from a goat farm in Northland in 1997. Twenty-six days post infection, the lambs were divided into 3 treatment groups and a control group (n=6 lambs/group). Treatment consisted of either ivermectin oral formulation (0.2 mg/kg), moxidectin oral formulation (0.2 mg/kg), or moxidectin injectable formulation (0.2 mg/kg). Faecal egg counts (FECs) were determined at 0, 3, 5, 7 and 10 days after treatment. All animals were necropsied 12 days after treatment and worm counts were performed. Larval development assays were conducted 24 days post infection. A further 3 lambs were infected with 15,000 infective third-stage larvae of a fully susceptible strain of T. colubriformis for comparative purposes in the larval development assay. The efficacy of the moxidectin injectable formulation was also confirmed in these 3 lambs. RESULTS: The FEC reduction test at day 10 after treatment revealed 62%, 100% and 0% reductions in arithmetic-mean FECs for ivermectin oral, moxidectin oral and moxidectin injectable groups, respectively. The ivermectin oral, moxidectin oral and moxidectin injectable formulations achieved 62%, 98% and 4% reductions in arithmetic-mean worm burdens, respectively. Larval development assays showed resistance ratios for ivermectin of 4:1, avermectin B2 of 2.7:1, ivermectin aglycone of 37:1, moxidectin of 1.4:1, thiabendazole of 14.6:1 and levamisole of 1.8:1. CONCLUSIONS: The moxidectin oral formulation provided a high degree of control against ivermectin-resistant T. colubriformis whereas the moxidectin injectable formulation had very low efficacy. Ivermectin aglycone was the analogue of choice for diagnosis of ivermectin resistance in T. colubriformis in the larval development assay.