Libyostrongylus douglassii in ostriches (Struthio camelus ssp.) in the Netherlands: case report and review

Several types of worms can parasitize ostriches, the most pathogenic of which is the wire worm (Libyostrongylus douglassii). This worm, which occurs in the stomach, can cause severe lesions which can lead to a high mortality, especially among young birds. This article describes mortality due to this parasite on an ostrich farm and discusses relevant literature on L. douglassii.     

Efficacy of ivermectin against the swine kidney worm, Stephanurus dentatus

Ivermectin in solution was given subcutaneously (in the neck) at the rate of 0.5 mg/kg of body weight to 5 sows naturally infected with kidney worm (Stephanurus dentatus). Six similar sows were used as nontreated controls. A total of 114 kidney worms were recovered from daily urine samples of 4 of the 5 treated sows (the 5th sow's samples were negative) during the first 4 days after treatment. Ten kidney worms were recovered from daily urine samples of 1 control sow on the 2nd and 3rd days of the post-treatment period. Examination of urine samples from treated sows for kidney worm eggs showed a precipitous numerical decrease. Treated animals became negative between the 5th and 12th days after treatment, and remained negative until necropsy on the 61st day. Compared with control sows, hatchability of eggs and survival of larvae from treated sows was reduced by 9% and 7%, respectively. Kidney worms were not recovered at necropsy from the treated sows, and a total of 392 kidney worms were recovered from the control sows (av 65).     

Efficacy of injectable ivermectin against natural infections of Stephanurus dentatus in swine

Ivermectin (300 micrograms/kg of body weight) was given to swine subcutaneously in the neck to test its efficacy against the kidney worm, Stephanurus dentatus. Two separate field trials were conducted using 146 swine (40 males and 106 females). Urine was obtained before and after treatment and was examined for presence of S dentatus eggs. Stephanurus dentatus eggs were quantitated in positive samples. All treated swine positive for S dentatus eggs in the pretreatment urine samples (n = 54) were negative by 14 to 21 days after treatment with ivermectin. Adverse reactions caused by ivermectin injection were not noticed.     

Morphological diagnosis of infective larvae of Libyostrongylus douglassii (Cobbold, 1882) Lane, 1923 and L. dentatus Hoberg, Lloyd and Omar, 1995 (Nematoda: Trichostrongylidae) of ostriches

The differentiation of the species of the Libyostrongylus genus is only possible with the obtainment of the adult parasites in the ostriches proventriculus and gizzard. The present work confirms that it is possible to differentiate the infective larvae of L. douglassii and L. dentatus allowing the differential diagnosis of these species by fecal culture. To show this, adult females from both species were collected from ten proventriculus from adult ostriches and separated by species. Both groups were macerated individually added to sterilized feces for standard fecal cultures. The infective larvae were recovered, identified, quantified and measured. All proventriculus analyzed were parasitized by Libyostrongylus spp. and a clear heterogeneous location for each species was observed. The infective larvae from the fecal cultures of macerated L. douglassii presented a mean total length of 874.3+/-33.80 microm, and a short sheath tail (29.5+/-4.11 microm) with acute termination. The infective larvae from the macerated L. dentatus presented mean total length of 856.0+/-43.63 microm, long sheath tail (61.2+/-9.52 microm) with filamentous termination. The mean measures of the tails of both species had a significant difference. The differentiation of the infective larvae of L. douglassii and L. dentatus by fecal cultures will facilitate the diagnosis of both species for further understanding the Libyostrongylus biology.     

Assessing resistance of ivermectin and moxidectin against nematodes in cattle naturally infected using three different methodologies

The objective of this study was to evaluate the accuracy of the faecal egg count reduction test (FECRT) and the faecal egg count efficacy test (FECET) to assess the resistance status of ivermectin (630 μg/kg) and moxidectin (200 μg/kg), using the controlled efficacy test as a reference, and whether the results of the EPG are equivalent to the efficacy results from the parasitological necropsies. Two experiments were conducted. The results demonstrate that it was not possible to demonstrate that the EPG values were equivalent with the ivermectin and moxidectin efficacy obtained by parasitological necropsies, mainly if the phenomenon of parasites resistance is not advanced in a determined field population. Maybe the FECET technique would be possibly better than the FECRT. The high anthelmintic efficacy of 200 μg/kg moxidectin, in naturally infected cattle, against field population of nematodes that are resistant to 630 μg/kg ivermectin, was observed in this study.     

Efficacy of moxidectin, nemadectin and ivermectin against an ivermectin-resistant strain of Haemonchus contortus in sheep.

The efficacies of ivermectin, nemadectin and moxidectin were evaluated when administered orally to lambs infected with either a susceptible laboratory strain of Haemonchus contortus or a strain reported to be resistant to ivermectin. Groups of 24 Dorset cross Cheviot cross Suffolk lambs were infected with either the susceptible or resistant strain of H contortus and allocated to treatment groups according to their faecal egg counts 27 days after infection. One day later the lambs were dosed orally with one of the three anthelmintics at 0.2 mg/kg bodyweight, and they were killed and surviving worms were recovered 13 or 14 days after treatment. Against the ivermectin resistant strain, ivermectin did not significantly reduce the egg count or the numbers of adult H contortus; however, both nemadectin and moxidectin reduced the nematode egg counts and the numbers of H contortus by 99 and 100 per cent, respectively. Against the susceptible strain, all the anthelmintics reduced the egg counts by 100 per cent as early as four days after treatment and reduced the numbers of susceptible H contortus by 100 per cent. No adverse reactions to any of the drugs were observed.     

Efficacy of ivermectin and moxidectin against Otostrongylus circumlitus and Parafilaroides gymnurus in harbour seals (Phoca vitulina)

Verminous bronchopneumonia caused by infection with Otostrongylus circumlitus and Parafilaroides gymnurus is an important cause of death during the rehabilitation of harbour seals (Phoca vitulina). During the winter of 2000/01, 35 juvenile harbour seals with severe clinical signs of verminous bronchopneumonia were treated with either 0.2 mg/kg ivermectin orally or 0.2 mg/kg moxidectin subcutaneously, and monitored for 30 days. The efficacy of the anthelmintics was determined by the pattern of larval excretion (Baermannisation) and the progress of the clinical signs. Both anthelmintics had reduced larval excretion by at least 99 per cent after 10 days, but the seals' rapid breathing rate and and dyspnoea returned to normal more quickly in the animals treated with moxidectin. The pharmacokinetics of the anthelmintics were determined by solid-phase extraction, and high-performance liquid chromatography with fluorescence detection. Moxidectin had a mean (sd) residence time of 9.04 (2.12) days compared with 4.83 (1.14) days for ivermectin.     

Mixed infection by Libyostrongylus douglassii and L. dentatus (Nematoda: Trichostrongylidae) in Struthio camelus (Ratites: Struthioniformes) from Brazil with further morphological characterization of adults

The genus Libyostrongylus includes three species, L. douglassii, L. dentatus and L. magnus that occur as parasites in the proventriculus of Struthio camelus. We confirmed a mixed infection by L. douglassii and L. dentatus in farmed ostriches from the southeast of Brazil for the first time, and provided new information on some morphological characters that differentiate these species. Adult nematodes collected from the proventriculus of ostriches were observed by light and scanning electron microscopy. Morphologic characterization and morphometric analysis of the nematodes enabled the distinction of both species and corroborated results of prior studies. Specimens of L. dentatus have a buccal capsule with a prominent esophageal tooth. Furthermore, males and females of L. dentatus were larger (4954 and 9347 microm) than those of L. douglassii (3411 and 4229 microm), but measurements for most characters in both species were smaller then those previously reported. Besides, the cephalic structure based on scanning electron microscopy differs, and L. dentatus has thick lips with round papillae, whereas L. douglassii has fine lips with lengthened papillae. The confirmation of both species in South America strongly suggests that the mixed infection may be common in farmed ostriches.     

Reduced efficacy of ivermectin, abamectin and moxidectin against field isolates of Haemonchus contortus

OBJECTIVES: To investigate the reduced efficacy of ivermectin, abamectin and moxidectin against two field isolates of Haemonchus contortus. These isolates were identified on separate properties in the New England region of New South Wales. PROCEDURE: Reduced efficacy of macrocyclic lactone anthelmintics against two field isolates of H contortus was suspected. These isolates were obtained from sheep on separate farms and pen trials were performed to investigate the efficacy of macrocyclic lactones. The percentage efficacy was calculated for moxidectin, ivermectin and closantel against the isolate from one farm (VHR23) and for moxidectin, ivermectin and abamectin against the isolate from the second (VHR29). The persistent activity of moxidectin against both isolates was investigated. RESULTS: Ivermectin and closantel were found to have efficacies below 80% against established populations of VHR23. Moxidectin was effective against an established population of VHR23 but the persistent activity was reduced to 7 days. Moxidectin was also found to be effective against established populations of VHR29, however, ivermectin and abamectin were found to have efficacies below 80%. There was no evidence of persistent activity of moxidectin against VHR29. CONCLUSION: A reduction in efficacy of abamectin and/or ivermectin against field isolates of H. contortus was identified from two farms in the New England region of New South Wales. The persistent effect of moxidectin was reduced against both isolates.     

Efficacy of ivermectin against Sarcoptes scabiei in pigs

The efficacy of orally administered ivermectin against Sarcoptes scabiei was investigated in pigs harbouring experimentally induced infections. Treatment at dosage rates of 300 and 500 microgram per kg body-weight provided 100% control as assessed by mite populations and clinical signs, while at a dose rate of 180 microgram per kg mite populations were substantially reduced but not eliminated.     

Efficacy of ivermectin against Dictyocaulus arnfieldi in ponies

The efficacy of orally administered ivermectin against induced Dictyocaulus arnfieldi infection was evaluated in a controlled study comprising 12 yearling ponies. Treatment with ivermectin paste, at a dose rate of 200 micrograms/kg bodyweight orally once, was 100 per cent effective against both adult and immature or inhibited stages of the horse lungworm. Similar control of second and third instars of Gastrophilus intestinalis was observed and no nematode eggs were present in faeces from seven to 15 days after treatment when the study was terminated.     

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 moxidectin against gastrointestinal nematodes of cattle.

Three groups of 11 naturally infected crossbred beef calves were injected subcutaneously with moxidectin 1 per cent injectable at 0.2 or 0.3 mg moxidectin/kg bodyweight or with the unmedicated vehicle. Nematode infections had been acquired during grazing from December to April. Based on the faecal egg counts and total worm counts of the control calves at necropsy (11 to 13 days after treatment) most of the calves had heavy parasitic burdens. Ostertagia ostertagi was predominant and the mean numbers of adults, developing fourth stage larvae (L4) and inhibited early L4 were 45,906, 10,061 and 68,918, respectively. Haemonchus placei and Trichostrongylus axei were also present in the abomasa. Three species of Cooperia, Oesophagostomum radiatum L4 and T colubriformis adults were found in the intestinal tract. Both dosages of moxidectin were equally effective (P < 0.05) against all the abomasal nematodes (99.9 to 100 per cent) and the intestinal tract nematodes (99.4 to 100 per cent). No adverse reactions to the moxidectin treatment were observed. Abomasal pathology characteristic of heavy O ostertagi infection was observed in the control calves, but not in the treated calves.     

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.     

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.     

Efficacy of moxidectin and other anthelmintics against small strongyles in horses

Objective To compare the efficacy of moxidectin to ivermectin, oxibendazole and morantel against some gastrointestinal nematodes in horses.
Design Faecal egg count reduction after treatment.
Procedure A farm was selected where the population of small strongyles in horses was known to be resistant to oxibendazole. Horses were allocated to treatment groups based on faecal egg counts. After treatment, faecal samples were taken up to 109 days after treatment and faecal egg counts estimated. Faecal cultures were used to estimate the contribution of small and large strongyles to the faecal egg counts at each sampling.
Results Moxidectin (0.4 mg/kg) suppressed faecal egg counts for 109 days after treatment in most horses compared to 40 days with ivermectin (0.2 mg/kg), 13 days with morantel (9.4 mg/kg) and less than 13 days with oxibendazole (10 mg/kg). Most of the faecal egg count was attributable to small strongyles based on faecal culture, although Strongylus vulgaris was present in some samples in low numbers. Oxibendazole resistance in small strongyles was confirmed and a less than expected efficacy of morantel was also seen.
Conclusion Moxidectin was highly effective in reducing faecal egg counts after treatment for at least 12 weeks and up to 16 weeks in most horses. These horses were infected with a population of small strongyles known to be resistant to oxibendazole and possibly morantel. The duration of the reduction in faecal egg counts after treatment with moxidectin (0.4 mg/kg) was at least twice that of ivermectin (0.2 mg/kg) and greater than four times that for morantel and oxibendazole.     

Efficacy of moxidectin 0.5% pour-on against swine nematodes

Forty pigs with induced infections of Ascaris suum, Trichuris suis, Metastrongylus spp., Oesophagostomum dentatum and O. quadrispinulatum were assigned to five-dose groups of moxidectin 0.5% pour-on with eight pigs per dose group. The doses were: moxidectin, 0 (vehicle control), 0.75, 1.00, 1.25, and 1.50 mg/kg(-1) body weight. Worm egg counts (EPG) were made from fecal samples collected on Day 2 pretreatment and on Day 14 or 15 post-treatment. Animals were ranked according to the descending order of A. suum egg counts made on Day 2 and blocked in groups of five. Pigs in blocked groups were assigned randomly to each of the five dose groups. Treatment doses were calculated on the basis of weights taken on Day 1 and were administered topically from the neck to the base of the tail. Pigs were housed by pairs in individual pens provided with self-feeders and automatic waterers. Necropsies were performed on equal numbers of pigs from each treatment group on days 14 and 15 post-treatment. Adult and larval worms were collected, identified and counted by standard parasitological techniques. All counts were transformed by Y=log10 (count+1) transformation prior to analysis. A two-way analysis of variance was conducted and treatment effect was tested for significance at the 5% level. Efficacies based on geometric means and optimal doses were as follows: Ascaris suum, 98.3% at 1.25; Metastrongylus spp., 100% at 0.75; Oesophagostomum quadrispinulatum, 100% at 1.50; and Trichuris suis, 93.5% at 0.75. Efficacy for O. dentatum was from 81.3% to 100%; however, the average number of O. dentatum (30) was too small for significance. Two species of lungworms were present, Metastrongylus apri and M. pudendotectus but they were not speciated at necropsy. As reported for several anthelmintics, the efficacy of moxidectin was variable for Trichuris. The highest efficacy was in the 0.75 dose group with six pigs harboring a few or no worms. The lowest efficacy was in the 1.25 group with only two pigs harboring a few or no worms.