阿维菌素驱除牛体内寄生虫实验

阿维菌素是伊维菌素的同类产品 ,但价格较伊维菌素低。为检验该药的驱虫效果 ,笔者用黄牛为实验动物 ,进行着两种药物驱虫的对比实验。1　材料与动物1 .1　实验药物　 1 %阿维菌素注射液、1 %伊维菌素注射液 (由本系寄生虫教研室提供 )。1 .2　实验动物及分组　黄牛 84头 (其中     

Efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle

The efficacy of a topical formulation of ivermectin against naturally acquired gastro-intestinal nematodes in weaner cattle was evaluated. At slaughter, 14-15 days after treatment, burdens of Ostertagia spp, Trichostrongylus axei and Oesophagostomum radiatum were significantly lower in the treated calves than in the untreated controls (p<0.01). Efficacies (based on geometric mean worm burdens of treated and control groups) were 99.6%, 95.1% and 100% respectively. The sizes of the Cooperia spp and Trichuris ovis burdens in the treated group did not differ significantly at the 5% level of confidence from those in the control group.     

Field trials in New Zealand confirming the efficacy of eprinomectin applied topically to cattle

The efficacy and acceptability of eprinomectin in a topical formulation against gastro-intestinal nematodes in cattle was assessed under field conditions. Seven similar commercial dairy farms in the North and South Islands of New Zealand were included in the studies, involving 247 Holstein-Friesian, Jersey or Jersey-cross cattle. Cattle were confirmed by positive faecal nematode egg counts to have natural infections of gastro-intestinal nematodes and were held in separate treatment groups. In each replicate, four animals received eprinomectin (500 microg/kg body weight) and one animal received vehicle solution, all applied topically at 1 ml/10 kg body weight. Faecal samples were collected before, and 14 days after treatment, for faecal trongylid egg counts. Animals treated with eprinomectin had significantly lower (p < 0.05) Day 14 faecal strongylid egg counts than the controls. There were no significant differences (p > 0.10) between treated and control groups for pretreatment strongylid egg counts. No formulation runoff or adverse reactions were observed. These studies showed eprinomectin to be effective against gastro-intestinal nematode infections and safe for use in dairy cattle under natural field conditions.     

Efficacy of an injectable formulation of eprinomectin against Psoroptes cuniculi, the ear mange mite in rabbits

Thirty rabbits naturally infected with ear mange mite, Psoroptes cuniculi, were subcutaneously administrated with a single dose of eprinomectin at 100, 200 and 300 microg/kg body weight or vehicle on day 0. The extent of lesions was scored on day -6 (prior to treatment), day 0 (treated), days 7, 14, 21, 28 and 35, the ear scabs were collected simultaneously; mites in scabs were examined and counted. The results showed that a single dose of eprinomectin at 200 or 300 microg/kg body weight following subcutaneous administration was able to eliminate P. cuniculi infection in rabbits, and a dose of eprinomectin at 100 microg/kg could significantly reduce mites but was unable to eliminate P. cuniculi.     

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 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.     

An eprinomectin extended-release injection formulation providing nematode control in cattle for up to 150 days

A series of 10 dose confirmation studies was conducted to evaluate the persistent activity of an extended-release injectable (ERI) formulation of eprinomectin against single point challenge infections of gastrointestinal and pulmonary nematodes of cattle. The formulation, selected based on the optimal combination of high nematode efficacy, appropriate plasma profile, and satisfactory tissue residue levels, includes 5% poly(d,l-lactide-co-glycolic)acid (PLGA) and is designed to deliver eprinomectin at a dose of 1.0 mg/kg bodyweight. Individual studies, included 16–30 cattle blocked based on pre-treatment bodyweight and randomly allocated to treatment with either ERI vehicle or saline (control), or the selected Eprinomectin ERI formulation. Treatments were administered once at a dose volume of 1 mL/50 kg bodyweight by subcutaneous injection in front of the shoulder. In each study, cattle were challenged with a combination of infective stages of gastrointestinal and/or pulmonary nematodes 100, 120 or 150 days after treatment and were processed for parasite recovery according to standard techniques 25–30 days after challenge. Based on parasite counts, Eprinomectin ERI (1 mg eprinomectin/kg bodyweight) provided >90% efficacy (p < 0.05) against challenge with Cooperia oncophora and Cooperia surnabada at 100 days after treatment; against challenge with Ostertagia ostertagi, Ostertagia lyrata, Ostertagia leptospicularis, Ostertagia circumcincta, Ostertagia trifurcata, Trichostrongylus axei, and Cooperia punctata at 120 days after treatment; and against challenge with Haemonchus contortus, Bunostomum phlebotomum, Oesophagostomum radiatum and Dictyocaulus viviparus at 150 days after treatment. Results of a study to evaluate eprinomectin plasma levels in cattle treated with the Eprinomectin ERI formulation reveal a characteristic second plasma concentration peak and a profile commensurate with the duration of efficacy. These results confirm that the Eprinomectin ERI formulation can provide high levels of parasite control against a range of nematodes of cattle for up to 5 months following a single treatment.     

Plasma disposition and faecal excretion of eprinomectin following topical and subcutaneous administration in non-lactating dairy cattle

AIMS: To investigate the plasma disposition and faecal excretion of eprinomectin (EPM) in non-lactating dairy cattle following topical and S/C administration.

METHODS: Holstein dairy cows, 3.5–5 years-old, were selected 20–25 days after being dried off and were randomly allocated to receive EPM either topically (n=5) or S/C (n=5) at dose rates of 0.5 and 0.2?mg/kg bodyweight, respectively. Heparinised blood and faecal samples were collected at various times between 1 hour and 30 days after treatment, and were analysed for concentrations of EPM using high performance liquid chromatography with a fluorescence detector.

RESULTS: The maximum concentration of EPM in plasma (C_max) and the time to reach C_max were both greater after S/C administration (59.70 (SD 12.90) ng/mL and 1.30 (SD 0.27) days, respectively) than after topical administration (20.73 (SD 4.04) ng/mL and 4.40 (SD 0.89) days, respectively) (p<0.001). In addition, S/C administration resulted in greater plasma availability (area under the curve; AUC), and a shorter terminal half-life and mean residence time (295.9 (SD 61.47) ng.day/mL; 2.95 (SD 0.74) days and 4.69 (SD 1.01) days, respectively) compared with topical administration (168.2 (SD15.67) ng.day/mL; 4.63 (SD 0.32) days, and 8.23 (SD 0.57) days, respectively) (p<0.01). EPM was detected in faeces between 0.80 (SD 0.45) and 13.6 (SD 4.16) days following S/C administration, and between 1 (SD 0.5) and 20.0 (SD 3.54) days following topical administration. Subcutaneous administration resulted in greater faecal excretion than topical administration, expressed as AUC adjusted for dose (1188.9 (SD 491.64) vs. 311.5 (SD 46.90) ng.day/g; p<0.05). Maximum concentration in faeces was also higher following S/C than topical administration (223.0 (SD 63.96) vs. 99.47 (SD 43.24) ng/g; p<0.01).

CONCLUSIONS: Subcutaneous administration of EPM generated higher plasma concentrations and greater plasma availability compared with topical administration in non-lactating cattle. Although the S/C route provides higher faecal concentrations, the longer faecal persistence of EPM following topical administration may result in more persistent efficacy preventing establishment of incoming nematode larvae in cattle.     

Efficacy of topical eprinomectin in the treatment of Chorioptes sp. infestation in alpacas and llamas

Chorioptes sp. mite infestation is increasingly recognized as a cause of skin disease in New World camelids and there is a need for an effective treatment protocol to eliminate herd infestation. In this field trial, eprinomectin applied topically at the rate of 0.5 mg kg(-1) weekly for 10 weeks was found to be ineffective in a herd of 12 llamas and 16 alpacas.     

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.     

替米考星注射液对牛呼吸道巴氏杆菌感染的治疗

替米考星（Tilmicosin，其注射剂商品名为MICOTIL）是美国礼来公司于20世纪80年代开发的半合成大环内酯类畜禽专用抗生素，其分子式为C46H80N2O13分子量为869．15，泰乐菌素硫酸或磷酸水解后的衍生物去碳霉糖泰乐菌素与3，5-二甲基哌啶反应生成替米考星碱，再加磷酸和水形成磷酸替米考星。     

Salmonella cholerae-suis from cattle in New Zealand

Abstract

Extract

Salmonella cholerae-suis is considered to be the most common salmonella found in pigs. Following its first isolation by Salmon and Smith (1885 Salmon, E. and Smith, T. 1885. Report on Swine Plague. Rep. U.S. Bur. anim. Ind., : 184–184.  [Google Scholar]), S. cholerae-suis was thought to be the cause of hog cholera. However, hog cholera is now known to be due to a virus, while S. cholerae-suis is a common secondary invader in this disease.     

Selenium reference ranges in New Zealand cattle

AIM: To compare serum selenium and liver selenium concentrations with whole blood concentrations in samples taken at the same time from unsupplemented cattle, and to use these comparisons to establish a reference range for use in diagnosing selenium deficiency. METHODS: Selenium was measured in concurrent whole blood, serum and liver samples obtained from cattle in unsupplemented herds in the Manawatu, Waikato and Wairarapa regions of New Zealand. The results were statistically analysed. RESULTS: The revised reference ranges are as follows. [table: see text] CONCLUSION: The serum and liver selenium concentrations used as reference values prior to this study were inaccurate for the detection of selenium deficiency.     

Inefficacy of moxidectin and doramectin against ivermectin-resistant Cooperia spp. of cattle in New Zealand

Two cases are described in which strains of Cooperia spp. of cattle were found to be resistant to either the oral or the injectable formulations of ivermectin. Injectable moxidectin was not effective against the latter strain and doramectin was not effective against either of the ivermectin-resistant Cooperia isolates. In both cases, the anthelmintic efficacy of oral levamisole was 100%.     

Inefficacy of moxidectin and doramectin against ivermectin-resistant Cooperia spp. of cattle in New Zealand

Two cases are described in which strains of Cooperia spp. of cattle were found to be resistant to either the oral or the injectable formulations of ivermectin. Injectable moxidectin was not effective against the latter strain and doramectin was not effective against either of the ivermectin-resistant Cooperia isolates. In both cases, the anthelmintic efficacy of oral levamisole was 100%.     

Duration of activity of topical eprinomectin against experimental infections with Teladorsagia circumcincta and Trichostrongylus colubriformis in goats

The immediate as well as the persistent anthelmintic efficacies of topically applied eprinomectin were evaluated in goats against induced infections with Teladorsagia circumcincta (2800 L3) and Trichostrongylus colubriformis (6000 L3). Twenty-three culled dairy goats were allocated to the following groups: control animals (group 1), animals treated 21 days prior to nematode infection (group 2), animals treated 7 days prior to nematode infection (group 3) and animals treated 21 days after nematode infection (group 4). Eprinomectin was applied at twice the cattle dose rate (1.0 mg/kg BW). According to the groups, necropsies were undertaken 28 days after nematode infection (groups 1-3) or 14 days after the anthelmintic treatment (group 4). Worm counts were determined for abomasum and small intestine. The curative anthelmintic efficacy of eprinomectin at 1.0 mg/kg BW on existing worm burdens was 100% against T. circumcincta and T. colubriformis. Quite similar worm burdens reductions were observed when eprinomectin was administered 7 days before infection whereas they were only 52.4 and 17.8% for T. circumcincta and T. colubriformis, respectively, for an administration of the drug 21 days prior to the nematode infection.     

Efficacy of ivermectin against Dermatobia hominis in cattle

Dermatobia hominis, the tropical warble fly, is one of the most important ectoparasites of cattle in Latin America. The results of five trials conducted in Paraguay, Brazil and Colombia showed that ivermectin administered subcutaneously at a dose level of 200 mcg/kg body weight was highly effective against the three larval stages of D. hominis in cattle.     

Bovine leukaemia virus infection in New Zealand cattle

Bovine Leukaemia Virus (BLV) infection in New Zealand cattle was investigated. In a national survey of 5000 sera from 500 herds, BLV antibody was not detected. An additional 1062 sera from 140 herds were tested and 3 sera were positive. In the herd of origin of one of these 3 sera, 22.6% of cattle were serologically positive for BLV. Where cases of bovine lymphosarcoma had been diagnosed, 38 of 39 herds tested were negative for BLV antibody. Within the remaining herd, 36% of cows tested were serologically-positive. BLV was isolated from 2 serologically positive cows in this herd.     

Lantana poisoning of cattle and sheep in New Zealand

The investigation of a field case of Lantana camara poisoning in cattle is reported. Toxicity was confirmed by the experimental dosing of two sheep with dried leaf powder at 6 and 12 mg/kg body weight. Marked cholestatic hepatophy and renal tubular disease resulted. This is the first reported case of toxicity due to grazing a Lantana camara variety grown in New Zealand.