Migration of warble fly larvae in the yak and optimum timing of ivermectin treatment

Sixty yaks were autopsied to determine the migration pattern of warble fly larvae. In August, first instars were observed in the body of yak for the first time. These larvae peaked in number in October. From November to February, second instars were detected and their number peaked in January. Third instars appeared in January and peaked in March. Forty-five yaks were administered with ivermectin: 15 animals in September, 15 in October and 15 in November. Between December and June, the number of warbles was checked by palpation. Although some warbles were observed in the September- and November-treated groups, no warbles were detected in the October-treated group. Treatment of yaks with ivermectin was most effective for warble fly in October.     

Field efficacy of minidosed eprinomectin against Hypoderma spp. in dairy cattle

A chemoprophylactic field trial was conducted to assess the efficacy of pour-on eprinomectin applied at the approximate dose of 50 mcg/kg to dairy cattle with naturally occurring hypodermosis. Two-hundred-eleven cattle, selected from two herds with a high prevalence of Hypoderma spp. infestation, were divided in three groups: Group A (N = 71) was treated with pour-on eprinomectin at the recommended dosage of 500 mcg/kg, Group B (N = 64) at the lower dose of 50 mcg/kg, a third group (Group C, N = 76) served as untreated control group. Treatments were performed in November-December 2002 and the animals were examined for the presence of warbles in the following April and June. No larvae emerged in the treated groups, whereas a variable number of warbles (ranging from 1 to 28) were found in control animals. Adverse reactions were not observed in any animal, and only minor side effects were observed. A larger field trial carried out in the following year (1064 treated and 131 untreated control cattle) confirmed the chemoprophylactic efficacy of minidosed eprinomectin against Hypoderma spp. Administration of eprinomectin minidoses in dairy cattle is interesting because of the low costs involved and no need for milk withdrawal.     

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.     

埃普利诺菌素浇泼剂对牦牛皮蝇幼虫驱除效果试验

应用埃普利诺菌素浇泼剂驱除牦牛皮蝇幼虫,并设埃普利诺菌素注射剂药物对照组和阳性对照组。结果：剖检埃普利诺菌素浇泼剂300μg/kg,400μg/kg,500μg/kg剂量组牦牛与药物对照埃普利诺菌素注射剂组及伊维菌素浇泼剂组牦牛,均未检出皮蝇1期幼虫,而阳性对照组牦牛皮蝇1期幼虫感染率35.0%,平均感染强度29.4（9～53）条。翌年3、5月份两次触摸检查牛背部皮下瘤疤和皮肤虫孔,4个药物试验组牦牛均未检出,而阳性对照组牦牛两次检查平均感染率45.16%,平均感染强度6.45个。试验证明埃普利诺菌素浇泼剂低、中、高3个剂量对寄生于牦牛的皮蝇幼虫驱净率、驱虫率均达100.0%,高效安全。     

皮蝇幼虫在牦牛体内移行动态与伊维菌素最佳驱除时间

2004年经剖检60头幼年牦牛,对牛皮蝇幼虫在牦牛体内移行动态进行了观察。8月份,第一期幼虫在牦牛体内出现,10月中旬牦牛体内第一期幼虫呈高峰。从11月中旬到第二年2月中旬第二期幼虫出现,元月中旬二期幼虫出现高峰,三期幼虫从元月中旬到6月初出现,3月中旬出现高峰。用伊维菌素给45头幼年牦牛投药:9月中旬,10月中旬和11月中旬各15头。9月中旬和11月中旬的投药群,在12月中旬均出现瘤疱,而10月中旬的投药群未发现瘤疱,表明10月中旬对第一期幼虫为最佳驱除时间。     

Field efficacy of minidosed pour-on ivermectin and eprinomectin against goat warble fly infestation by Przhevalskiana silenus

The efficacy of minidose of pour-on ivermectin and eprinomectin formulations against first instar larvae of Przhevalskiana silenus was observed in naturally infested goats in the Jammu region, North India. The study was performed in mid August 2011. A total of 280 goats were randomly divided in to 7 groups of 40 each. Goats of the first three groups were treated with pour-on ivermectin at dosage of 2, 5, and 200 μg/kg body weight, respectively, whereas animals of the fourth to sixth groups were treated with pour-on eprinomectin at 25, 50, and 500 μg/kg body weight, respectively. Group VII animals were kept as untreated control. The results indicated that no warbles were recorded between December 2011 and March 2012 on back of animals treated with pour-on preparations of ivermectin at dosage of 5 and 200 μg/kg body weight, respectively, and eprinomectin at dosage of 50 and 500 μg/kg body weight, respectively. Thus, it is concluded that administration of minidose of pour-on ivermectin (5 μg/kg body weight) and eprinomectin (50 μg/kg body weight) is cost effective and so can be used for warble fly control campaign in Jammu region.     

Persistent activity of topical ivermectin against artificial infestations with Hypoderma lineatum (Diptera: Oestridae)

In controlled experiments utilizing artificial infestations, a topical formulation of ivermectin (IVOMEC Pour-On for Cattle) was 100% effective against migrating first instar Hypoderma lineatum for 3 weeks following treatment. Larvae were apparently killed early in the infestation as no significant level of specific antibodies was found in the treated calves. At 4 weeks post-treatment the efficacy remained high at 96%; mortality of larvae in the one calf in which warbles were observed and from which mature third instars were collected, was higher than that seen in the untreated calves, indicating some level of treatment induced effect. No specific antibodies were detected in calves that did not develop palpable warbles. Antibody kinetics in those calves from which viable larvae emerged were typical. The length of activity of this product against early stages of the cattle grub makes it practical to apply treatment up to 3 weeks before the end of fly activity.     

Efficacy of a pour-on formulation of doramectin against lice, mites, and grubs of cattle

OBJECTIVE: To determine effectiveness of a pour-on formulation of doramectin against Damalinia bovis, Haematopinus eurysternus, Linognathus vituli, Solenopotes capillatus, Chorioptes bovis, Sarcoptes scabiei, Hypoderma bovis, and Hypoderma lineatum. ANIMALS: Cattle of various ages with naturally acquired or artificial infestations with 1 or more species of lice, mites, or grubs. PROCEDURE: In 10 louse and 6 mite studies, cattle were treated with doramectin (500 microg/kg, topically) on day 0, and parasite counts were performed approximately weekly from days 0 to 35. In 6 grub studies, cattle expected to harbor Hypoderma spp were treated before emergence of warbles. After warbles began to emerge, they were counted every 2 weeks, and grubs were collected and identified by species. RESULTS: Burdens of D bovis, H eurystemus, L vituli, and S capillatus on doramectin-treated cattle were 0 by 28 days after treatment. Burdens of C bovis and S scabiei decreased to 0 in naturally infested cattle and approximately 0 in artificially infested cattle by day 14 to 15. In grub studies, 107 of 136 control cattle had warbles, whereas 2 of 136 doramectin-treated cattle had 1 warble each, which represented a cure rate of 98.5%. CONCLUSION AND CLINICAL RELEVANCE: One topical application of doramectin was highly efficacious against common species of lice, mites, and grubs known to affect performance, health, and appearance of cattle.     

Comparison of the efficacy of dermal formulations of ivermectin and levamisole for the treatment and prevention of Dictyocaulus viviparus infection in cattle

Four groups of six parasite-naive calves were infected at seven day intervals with three doses of infective larvae of Dictyocaulus viviparus. Twenty-one days after the first dose three of the groups were treated either with an injectable formulation of ivermectin at a dose rate of 200 micrograms/kg bodyweight, or with pour-on preparations of levamisole at 10 mg/kg or ivermectin at 500 micrograms/kg. On day 28 two calves from each group were slaughtered and their burdens of lungworms counted. On day 35 the remaining calves were reinfected with D viviparus infective larvae at a rate of 80 L3/kg. The levamisole preparation was 94.6 per cent effective and both ivermectin preparations were 100 per cent effective against the initial infections. The ivermectin-treated calves were protected from the reinfection which subsequently became patent in the levamisole-treated and control calves.     

Oral and parenteral administration of ivermectin to reindeer.

The anti-parasitic effect of the orally administered paste formulation of ivermectin (Ivomec) in reindeer was evaluated by means of a trial designed to compare the efficacies of orally and s.c. administered ivermectin at the same dosage (0.2 mg kg-1 body weight) in naturally infected adult reindeer (n = 92). Both formulations were 100% effective against larvae of the warble fly, Oedemagena tarandi, while oral treatment was less efficacious than s.c. injection against parasitic nematodes. Both formulations, but particularly the injectable ivermectin treatment, increased the weight gain of pregnant females compared to that of those not treated.     

An Intradermal Test to Detect Latent Warble (Hypoderma spp.) Infection in Cattle

An intradermal test was developed to screen cattle for infection with the first-instar larvae of the warble flies Hypoderma lineatum and H. bovis. The diagnostic antigen, prepared from the first-instar larvae of H. lineatum, produced a distinct dermal reaction in cattle infected with the first-instar larvae of either species, but not in cattle in which the infection could not be confirmed later either on necropsy or by the appearance of warbles in the back. The reaction to the antigen was unpredictable in cattle with warbles in their backs. The diagnostic property of the antigen was also demonstrated in rabbits and guinea pigs artificially sensitized to the antigen.     

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.     

Comparison of the persistent efficacy of the injectable and pour-on formulations of doramectin against artificially-induced infection with Dictyocaulus viviparus in cattle

The persistent efficacy of the injectable and topical formulations of doramectin was compared against experimental challenges with infective larvae of Dictyocaulus viviparus in two separate studies. Four groups of 10 randomly-assigned calves, negative for lungworm larvae by the Baermann technique, were used in each study. Calves were treated subcutaneously in the midline of the neck or poured down the midline of the back with saline (1 ml/50 kg. injection: 1 ml/10 kg. pour-on) on Day 0 or doramectin (200 microg/kg = 1 ml/50 kg. injection: 500 microg/kg = 1 ml/10 kg. pour-on) on Day 0, 7, or 14. Two additional calves from the same pool of animals were randomly assigned as larval-viability monitors and received no treatment. Calves were inoculated daily with a gavage of approximately 100 larvae of D. viviparus from days 35 to 49 for the injectable study and days 28 to 42 for the pour-on study. The two larval viability monitor calves received approximately 3000 infective larvae in the same manner on Day 49 or 42 for the injectable and pour-on studies, respectively. Equal numbers of calves from each treatment group as well as the larval viability monitor calves were necropsied on days 14 and 15 after the last lungworm inoculation to enumerate the worm burden. The worms recovered were quantified and identified. For each study, geometric mean worm recoveries for each treatment group were back transformed from the natural log-transformed data (worm count +1) and were used to estimate percentage reduction. Doramectin injectable solution was 100.0% efficacious against lungworms for up to 49 days and the pour-on formulation was 100.0%, 93.1% and 81.5% effective in reducing lungworm infection resulting from challenge infection for up to 28, 35, and 42 days post-treatment, respectively.     

Pharmacokinetics of ivermectin in llamas (Lama glama)

The pharmacokinetic behaviour of ivermectin was investigated in adult llamas (Lama glama) by using high performance liquid chromatography with a lower limit of quantification of 2 ng/ml to measure its concentration in serum. Llamas were treated with one of three commercial formulations (injectable, pour-on or oral paste) at dosages recommended by the manufacturer, or with an experimental injectable sustained-release formulation. In five llamas given 1 per cent ivermectin subcutaneously at 200 microg/kg, the median peak serum concentration (Cmax) was 3 ng/ml and the area under the serum concentration-time curve (AUC) was 13.5 ng x day/ml. In six llamas treated topically with 0.5 per cent ivermedin pour-on at 500 microg/kg, Cmax was 2.5 ng/ml or less and the AUC was 7.75 ng x day/ml or less. In seven llamas with measurable concentrations of ivermedin, the median times to peak serum concentration (tmax) were six days after subcutaneous injection and seven days after treatment with the pour-on formulation. In six llamas, the serum concentration of ivermectin remained less than 2 ng/ml for 124 hours after treatment with a 1.87 per cent oral paste at 200 microg/kg. In five llamas treated subcutaneously with 25 per cent ivermectin sustained-release microspheres at 1500 microg/kg, the median Cmax was 5 ng/ml and the median AUC was 224 ng x day/ml.     

Anthelmhntic effects of injectable and oral paste formulations of ivermectin against 28-day infections of parascaris equorum

Efficacy of ivermectin treatment (0.2 mg/kg) against 28-day experimental infections of Parascaris equorum was determined in 18 pony foals6–17.5 weeks old. There were 6 foals in each group: nontreated control, ivermectin injectable or oral paste. In comparison with larvae found in the nontreated controls, ivermectin injectable or paste was 96.0% and 99.9% efficacious. There was a distinct difference in drug effect against the larger (ca 26mm.) vs the smaller (13–19mm) larvae by the 2 formulations of ivermectin. There were no adverse signs related to treatment of the young foals.     

Efficacy of abamectin against ivermectin-resistant strain of Trichostrongylus colubriformis in sheep

The efficacy of two formulations of abamectin, i.e. oral and injectable was determined against ivermectin-resistant strain of T. colubriformis in sheep. Twenty-four lambs were infected with 10,000 third stage larvae of ivermectin-resistant strain of T. colubriformis. Twenty-four days post-infection, the lambs were divided randomly into four groups of six animals each according to egg counts. The first group was left untreated and kept as a control. The second group was treated with ivermectin (oral) at 0.2mg kg(-1) body weight. The third group was treated with oral formulation of abamectin at 0.2mg kg(-1) body weight. The fourth group was treated with injectable formulation of abamectin at 0.2mg kg(-1) body weight. Fecal egg count and controlled slaughter tests were employed to determine the efficacy of abamectin (oral and injection) against ivermectin-resistant strain of T. colubriformis in sheep. Reduction in arithmetic mean fecal egg counts achieved by ivermectin (oral), abamectin (oral) and abamectin (injection) was 66, 98 and 76%, respectively 10 days after treatment. Ivermectin (oral), abamectin (oral) and abamectin (injection) reduced arithmetic mean worm burden by 63, 97 and 74%, respectively. The findings demonstrated that abamectin oral formulation was more effective than abamectin injection against ivermectin-resistant strain of T. colubriformis in sheep.     

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

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

Transmission of Babesia spp by the cattle tick (Boophilus microplus) to cattle treated with injectable or pour-on formulations of ivermectin and moxidectin

OBJECTIVE: To assess the efficacy of ivermectin and moxidectin to prevent transmission of Babesia bovis and Babesia bigemina by Boophilus microplus to cattle under conditions of relatively intense experimental challenge. DESIGN: Naive Bos taurus calves were treated with either pour-on or injectable formulations of either ivermectin or moxidectin and then exposed to larvae of B microplus infected with B bovis or larvae or adults of B microplus infected with B bigemina. One calf was used for each combination of haemoparasite, B microplus life stage, drug and application route. PROCEDURE: Groups of calves were treated with the test drugs in either pour-on or injectable formulation and then infested with B microplus larvae infected with B bovis or B bigemina. B bigemina infected adult male ticks grown on an untreated calf were later transferred to a fourth group of animals. Infections were monitored via peripheral blood smears to determine haemoparasite transmission. RESULTS: Cattle treated with either pour-on or injectable formulations of ivermectin and moxidectin became infected with B bovis after infestation with infected larvae. Similarly, larvae infected with B bigemina survived to the nymphal stage to transmit the haemoparasite to animals treated with each drug preparation. Cattle treated with pour-on formulations of ivermectin and moxidectin then infested with adult male ticks infected with B bigemina did not become infected with B bigemina whereas those treated with the injectable formulations of ivermectin and moxidectin did show a parasitaemia. CONCLUSIONS: Injectable or pour-on formulations of ivermectin and moxidectin do not prevent transmission of Babesia to cattle by B microplus. Use of these drugs can therefore not be recommended as a primary means of protecting susceptible cattle from the risk of Babesia infection.     

Efficacy of ivermectin chewable tablets and two new ivermectin tablet formulations against Dirofilaria immitis larvae in dogs.

One hundred four heartworm-free Beagles less than 1 year old were studied to determine the efficacy of ivermectin chewable tablets and of 2 other ivermectin tablet formulations against heartworm larvae. At 30 days after SC inoculation of dogs with infective Dirofilaria immitis larvae, all ivermectin formulations were given orally at dosage of 6 micrograms/kg of body weight. The ivermectin chewable tablets also were given orally at dosage of 2 and 6 micrograms/kg at 30 and 45 days, respectively, after injection of larvae. Replicates of 6 or 8 dogs in each study were formed on the basis of gender and body weight and, within replicates, were randomly allocated to treatment groups. At 30 days after injection of larvae, the additional dogs (in replicates of 8) were assigned to the control group and to the group given ivermectin chewable tablets at dosage of 6 micrograms/kg. All dogs were housed individually. Necropsy was performed approximately 5 or 6 months after larvae were administered. In both trials, all control dogs had heartworms at necropsy (University of Illinois--geometric mean, 35.0; Florida--geometric mean, 26.1). In both trials, the ivermectin chewable tablet (6 micrograms/kg) and both tablet formulations (6 micrograms/kg) given at 30 days after larval injection, and the chewable formulation (6 micrograms/kg) given at 45 days after larval injection were 100% effective (P less than 0.01) in preventing development of induced infection with D immitis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Activity of ivermectin against natural infections by abomasal nematodes in lambs in controlled tests: evaluation of equine and bovine injectable formulations administered intraorally

The efficacy of 2 injectable formulations of ivermectin, administered intraorally at the dosage of 200 micrograms/kg of body weight, was evaluated against naturally occurring infections by abomasal nematodes in lambs in 2 controlled tests. One test (A) included 17 lambs treated with the equine formulation and 16 nontreated lambs. For the other test (B), 14 lambs were treated with the bovine formulation, and 12 were nontreated. In controlled test A, only mature nematodes were recovered, and removals were 98% to 100% for Haemonchus contortus, Ostertagia circumcincta male, O trifurcata male, Ostertagia spp female, and Trichostrongylus axei. For controlled test B, removals were 99% to 100% for Haemonchus spp (immature), H contortus (mature), Ostertagia spp (immature), O circumcincta male (mature), O trifurcata male (mature), Ostertagia spp female (mature), Trichostrongylus spp (immature), and T axei (mature). Toxicosis was not evident in treated lambs.