101
|
Egerton JR, Suhayda D, Eary CH. Laboratory selection of Haemonchus contortus for resistance to ivermectin. J Parasitol 1988; 74:614-7. [PMID: 3397823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The eighth generation of adult Haemonchus contortus, selected by subjecting infected pairs of sheep to suboptimal ivermectin treatment once per generation from parent (P; BBH isolate) through F7 (IV-A; selected isolate), required an approximate 4-fold increase in the ivermectin dose to produce 95% efficacy compared with its contemporary parent isolate. In a dose titration experiment the dose-response curve of the drug pressure-derived isolate, IV-A, was significantly (0.02 less than P less than 0.05) less steep than was the response curve of the parent, BBH, isolate. Potency estimates based upon these nonparallel dose-response curves would not remain constant over a range of efficacy levels but would decrease rapidly at efficacies greater than 95%. Passage of a closed population of the F8 generation of IV-A sequentially through pairs of sheep for an additional 11 generations (F8A-F8K) without additional drug pressure being applied produced no reversion to sensitivity to ivermectin relative to the F7 generation, thus suggesting that the selected "resistance" was stable.
Collapse
|
102
|
Bauer C, Fiege N, Klatte D, Enninga J, Bürger HJ. [Field studies of anthelmintic resistance of trichostrongylids in Hessian sheep herds]. BERLINER UND MUNCHENER TIERARZTLICHE WOCHENSCHRIFT 1988; 101:185-9. [PMID: 3401204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
103
|
Lacey E, Snowdon KL. A routine diagnostic assay for the detection of benzimidazole resistance in parasitic nematodes using tritiated benzimidazole carbamates. Vet Parasitol 1988; 27:309-24. [PMID: 3369079 DOI: 10.1016/0304-4017(88)90045-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Resistance to benzimidazoles (BZs) in parasitic nematodes has recently been shown to be due to a reduction in the ability of BZs to bind the structural protein, tubulin, in resistant isolates. Based on these observations the development and standardisation of a routine diagnostic assay has been undertaken by measuring the binding of tritiated mebendazole to crude supernatants of L3 larvae. The assay is rapid, requiring less than 2 h, and is robust, highly reproducible and sensitive to minor changes in the resistance status of parasite populations. Investigation of the routine application and validity of this assay has been documented using 24 isolates of known resistance status from the species Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia circumcincta: In all cases the observed binding and calculated susceptibility factors were in accordance with their respective resistance status.
Collapse
|
104
|
Boisvenue RJ, Colestock EL, Hendrix JC. Anthelmintic activity of continuous low doses of fenbendazole into the rumen of sheep. Vet Parasitol 1988; 26:321-7. [PMID: 3347991 DOI: 10.1016/0304-4017(88)90100-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Fenbendazole (FBZ) was continuously infused for 30 days into the rumen of 103 lambs which had mature or developing benzimidazole-susceptible or thiabendazole-resistant Haemonchus contortus and susceptible Trichostrongylus colubriformis infections. Ovicidal, larvicidal and adulticidal activities were exhibited against benzimidazole-susceptible and benzimidazole-resistant H. contortus worms by FBZ at a dose level of greater than or equal to 0.2 mg kg-1 body weight day-1. Reasonably consistent high level efficacy against H. contortus was obtained with dose levels greater than 0.4 mg kg-1. Excellent control of susceptible T. colubriformis worms was achieved with the lowest dose tested of 0.4 mg kg-1 day-1. The intraruminal infusion critical study method is a tool to determine the feasibility of incorporating a candidate anthelmintic compound in a continuous sustained-release rumen device formulation. The anthelmintic profile of FBZ obtained by low-level intraruminal administration suggests that it would be a potential candidate.
Collapse
|
105
|
Lacey E, Snowdon KL, Eagleson GK, Smith EF. Further investigation of the primary mechanism of benzimidazole resistance in Haemonchus contortus. Int J Parasitol 1987; 17:1421-9. [PMID: 3440696 DOI: 10.1016/0020-7519(87)90077-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
106
|
Abstract
Fifteen calves, each infected with approximately 3000 third stage larvae, were used to compare the tendencies of two strains of Dictyocaulus viviparus to inhibit at the fifth larval stage and to evaluate the efficacy of ivermectin. There were notable differences between the strains. While greater than 99% of worms developing from infection with an Alpine strain remained inhibited 42 days after infection, only 0-26% of those recovered following infection with a U.K. laboratory strain were arrested. Neither adult nor immature D. viviparus were present in the lungs of animals treated with ivermectin subcutaneously at 200 micrograms/kg body weight 28 days after infection with the Alpine larvae.
Collapse
|
107
|
Carmichael I, Visser R, Schneider D, Soll M. Haemonchus contortus resistance to ivermectin. J S Afr Vet Assoc 1987; 58:93. [PMID: 3681886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
|
108
|
Borgsteede FH, Couwenberg T. Changes in LC50 in an in vitro egg development assay during the patent period of Haemonchus contortus in sheep. Res Vet Sci 1987; 42:413-4. [PMID: 3616153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Using an in vitro egg development assay with thiabendazole as anthelmintic the LC50 of eggs produced by two sheep infected with either a susceptible or a resistant strain of Haemonchus contortus was followed during the patent period from 22 days to 77 days after infection. In both sheep the LC50 followed the same pattern. At the start of the patent period the average values for the susceptible and the resistant strain were, respectively, 0.05 and 0.21 micrograms ml-1 thiabendazole, after 40 to 60 days 0.09 and 0.35 micrograms ml-1, while after 77 days 0.07 and 0.24 micrograms ml-1 were recorded.
Collapse
|
109
|
Folz SD, Pax RA, Thomas EM, Bennett JL, Lee BL, Conder GA. Detecting in vitro anthelmintic effects with a micromotility meter. Vet Parasitol 1987; 24:241-50. [PMID: 3617429 DOI: 10.1016/0304-4017(87)90045-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
An in vitro target parasite anthelmintic assay utilizing a micromotility meter has been developed and validated. Haemonchus contortus, an economically important ruminant helminth with worldwide distribution, was the parasite used in the model. Four commercially available ruminant anthelmintics (albendazole, ivermectin, levamisole hydrochloride and coumaphos) were initially evaluated at concentrations of 200, 150, 100 and 50 micrograms ml-1. All four significantly affected helminth motor activity and were active at 200 and 150 micrograms ml-1, and three of the four were active at 100 and 50 micrograms ml-1. An Upjohn compound (p-toluoyl chloride phenylhydrazone) was also assayed and was significantly active at all four levels. In a subsequent titration study, albendazole, levamisole hydrochloride, ivermectin and the hydrazone were significantly active at 100 and 10 micrograms ml-1; only levamisole hydrochloride and the hydrazone were active at 1.0 microgram ml-1. None of the drugs were active at 0.1 microgram ml-1. The data indicate that the in vitro H. contortus assay utilizing the micromotility meter is sensitive, accurate, rapid, repeatable, and inexpensive. With additional effort, this model can be extended to incorporate other target helminth parasites and stages of development. This in vitro assay system should be a valuable addition to the battery of tests used to identify anthelmintic candidates, monitor drug resistance, and define the kinetics and mode of action of drugs.
Collapse
|
110
|
Bauer C, Ullrich D, Fiege N, König D, Luft W, Bürger HJ. [Benzimidazole resistance in Haemonchus contortus in a south German sheep herd]. DTW. DEUTSCHE TIERARZTLICHE WOCHENSCHRIFT 1987; 94:205-6. [PMID: 3297604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
111
|
Düwel D, Schmid K, Bechmann G. [Benzimidazole-resistant Haemonchus contortus in sheep in West Germany]. BERLINER UND MUNCHENER TIERARZTLICHE WOCHENSCHRIFT 1987; 100:120-3. [PMID: 3593194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
112
|
Petronijevic T, Rogers WP. Undissociated bases as the stimulus for the development of early parasitic stages of nematodes. Int J Parasitol 1987; 17:911-5. [PMID: 3583539 DOI: 10.1016/0020-7519(87)90007-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
113
|
Lacey E, Brady RL, Prichard RK, Watson TR. Comparison of inhibition of polymerisation of mammalian tubulin and helminth ovicidal activity by benzimidazole carbamates. Vet Parasitol 1987; 23:105-19. [PMID: 3564338 DOI: 10.1016/0304-4017(87)90029-x] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The correlation between the inhibition of hatching of Haemonchus contortus eggs and inhibition of mammalian tubulin polymerisation by benzimidazole carbamates has been investigated. The hatching process was observed to be independent of the biomass (eggs plus debris) over a 6-fold range and the early (E1-E3) stages of egg development, but was dependent on the concentration of co-solvent (DMSO) and time of incubation. Benzimidazole carbamates with strong inhibitory activity against mammalian tubulin were potent inhibitors of egg hatch, while non-inhibitors failed to prevent hatching. It is postulated that the primary mode of action of these drugs on nematode eggs is the inhibition of microtubule-dependent processes within the developing egg. The implications and limitations of this correlation are discussed.
Collapse
|
114
|
Obendorf DL, Parsons J, Nicholls J. An egg development test for the evaluation of benzimidazole resistance in Nematodirus spathiger. Aust Vet J 1986; 63:382-3. [PMID: 3827781 DOI: 10.1111/j.1751-0813.1986.tb02911.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
115
|
Waller PJ, Lacey E. The effect of triflumuron (SIR8514) on the free-living stages of sheep nematodes. Vet Parasitol 1986; 21:119-26. [PMID: 3739204 DOI: 10.1016/0304-4017(86)90152-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Studies both in vitro and in vivo showed that the insect growth regulator, triflumuron, exhibited potent larvacidal effects against the free-living stages of Trichostrongylus colubriformis. Effects were not as marked on the closely related nematodes, Haemonchus contortus and Ostertagia circumcincta. Nevertheless, these findings suggest that growth regulators may be used to develop novel methods of nematode control, and thus offer alternatives or adjuncts to conventional anthelmintic therapy and at the same time reduce the selection for anthelmintic resistance.
Collapse
|
116
|
Petronijevic T, Rogers WP, Sommerville RI. Organic and inorganic acids as the stimulus for exsheathment of infective juveniles of nematodes. Int J Parasitol 1986; 16:163-8. [PMID: 3721706 DOI: 10.1016/0020-7519(86)90101-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
117
|
Gruner L, Kerboeuf D, Beaumont C, Hubert J. Resistance to benzimidazole of Haemonchus contortus utkalensis in sheep on Martinique. Vet Rec 1986; 118:276. [PMID: 3962103 DOI: 10.1136/vr.118.10.276] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
118
|
Webb RF, Ottaway SJ. The prevalence of anthelmintic resistance in sheep nematodes on the central tablelands of New South Wales. Aust Vet J 1986; 63:13-6. [PMID: 3954686 DOI: 10.1111/j.1751-0813.1986.tb02863.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A survey was undertaken to assess the prevalence of anthelmintic resistance in sheep nematode populations on 40 commercial farms distributed throughout the central tablelands of New South Wales. Representatives of the 2 major groups of broad spectrum anthelmintics with different modes of action (thiabendazole and levamisole) were used at the manufacturer's recommended dose rates. Efficacy was assessed on the basis of the reduction in faecal strongyle egg counts 7 days after treatment. An efficacy of less than 90% using both anthelmintics was obtained on 4 farms. Thiabendazole had an efficacy of less than 90% on a further 21 farms and levamisole had an efficacy of less than 90% on an additional 4 farms. There was no evidence of anthelmintic resistance on 8 farms, while the remaining 3 had insignificant parasite burdens. Based on larval cultures from faeces, Ostertagia and Trichostrongylus were the most significant species in resistant populations. Haemonchus burdens were sporadic and levels of resistance relatively low. Nematodirus burdens were widespread but no evidence of resistance was detected.
Collapse
|
119
|
Dobson RJ, Donald AD, Waller PJ, Snowdon KL. An egg-hatch assay for resistance to levamisole in trichostrongyloid nematode parasites. Vet Parasitol 1986; 19:77-84. [PMID: 3962165 DOI: 10.1016/0304-4017(86)90034-8] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
An in vitro technique is described for detecting resistance of nematodes to the anthelmintic levamisole hydrochloride. Samples of eggs are developed under controlled temperature conditions until just prior to the commencement of hatching. They are then exposed to different concentrations of the drug and, when hatching is almost complete, the test samples are killed and preserved. The proportion of unhatched eggs at each drug concentration can then be counted at leisure. Provided a suitable range of drug concentrations is chosen for each test isolate, this assay provides results which may be satisfactorily fitted to a log-concentration-probit regression model. Comparisons with in vivo anthelmintic assays have shown that the technique provides an accurate reflection of the resistance status of parasite populations.
Collapse
|
120
|
Kaur R, Sood ML. Effects of anthelmintics on Haemonchus contortus (Nematoda: Trichostrongylidae). Vet Res Commun 1986; 10:21-36. [PMID: 3511606 DOI: 10.1007/bf02213962] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The review summarizes and evaluates recent information about the effects of anthelmintics on Haemonchus contortus. The topic is discussed under the headings effects of drugs on the absorptive surfaces, effects of drugs on metabolism, effects of drugs on the neuromuscular system, effects of drugs on developmental stages, anthelmintic efficacy, and resistant strains. Possible future lines of work are suggested in the conclusions.
Collapse
|
121
|
Rapson EB, Jenkins DC, Topley P. Trichostrongylus colubriformis: in vitro culture of parasitic stages and their use for the evaluation of anthelmintics. Res Vet Sci 1985; 39:90-4. [PMID: 4035096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Approximately 50 per cent of fourth stage larvae of Trichostrongylus colubriformis taken from the gerbil, Meriones unguiculatus, on day 8 after infection, moulted to the young adult stage when cultured in a complex medium over a seven day period in vitro. Larvae at the late fourth stage of development were highly susceptible to certain benzimidazole, prebenzimidazole, imidazothiazole, pyrimidine, quaternary ammonium, organophosphorus and macrocyclic lactone anthelmintics when any of these were included at very low concentrations in the culture medium. However, few anthelmintics lacking activity against T colubriformis in vivo affected these larvae. An assay employing these larvae in vitro should offer a means for assessing the intrinsic activity of new compounds against T colubriformis in the absence of any complicating host pharmacokinetic factors, and could also be adapted for use as a high capacity preliminary screen. Thus it should now be possible to employ a target parasite at the earliest stages of a lead discovery programme obviating the need to use less relevant free-living nematodes or ones that are natural parasites of rodents.
Collapse
|
122
|
Sangster NC, Prichard RK. The contribution of a partial tricarboxylic acid cycle to volatile end-products in thiabendazole-resistant and susceptible Trichostrongylus colubriformis. Mol Biochem Parasitol 1985; 14:261-74. [PMID: 3990706 DOI: 10.1016/0166-6851(85)90054-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Acetate, propionate, ethanol and propanol were the predominant end-products released during incubation of a thiabendazole resistant and a susceptible strain of Trichostrongylus colubriformis. The parasites in all the incubations appeared to be deficient in reducing equivalents if the end-products arose from the classical catabolic pathway through fumarate reductase (EC 1.3.1.6). Possible alternative pathways for accounting for redox balance, including beta-oxidation, the pentose phosphate pathway and amino acid metabolism were investigated. Palmitate was oxidised aerobically. Radiolabelled tricarboxylic acid cycle intermediates, citrate and alpha-ketoglutarate, were decarboxylated to 14CO2 indicating that at least a partial tricarboxylic acid cycle to succinyl-CoA via alpha-ketoglutarate operates both anaerobically and aerobically in T. colubriformis. These data and the pattern of end-products suggest the presence of two pathways to propanol and propionate either through fumarate reduction or alpha-ketoglutarate oxidation. T. colubriformis may apportion carbon flow through these pathways to maintain a stable redox ratio. Similar calculations on previously reported data indicate that both pathways may also operate in Haemonchus contortus. Exposure of resistant T. colubriformis to thiabendazole under anaerobic conditions caused an increased accumulation of end-products, especially propanol, in the incubation medium. The alpha-ketoglutarate pathway may lower the dependence of the parasite on the fumarate reductase route which is sensitive to thiabendazole. The operation of the alpha-ketoglutarate pathway, with propanol as an end-product, may provide a mechanism for regulating redox balance in trichostrongylidae.
Collapse
|
123
|
Martin PJ, Anderson N, Jarrett RG. Resistance to benzimidazole anthelmintics in field strains of Ostertagia and Nematodirus in sheep. Aust Vet J 1985; 62:38-43. [PMID: 3994603 DOI: 10.1111/j.1751-0813.1985.tb14230.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Resistance to a range of benzimidazole anthelmintics was investigated in 2 strains of Ostertagia spp. One strain (SR80) had been exposed to fenbendazole, oxfendazole and thiabendazole, the other strain (KR79) only to thiabendazole. Both strains showed a high degree of resistance to albendazole, fenbendazole, oxfendazole and thiabendazole, which had efficiencies of 11-38% and 0-60% against all developmental stages of SR80 and KR79, respectively. There was no significant reduction in the KR79 worm count by thiabendazole at 132 mg kg-1 given either as a single dose or divided into 12 equal portions, one administered every 6h. Nematodirus spp were also found to be resistant to all benzimidazoles tested. Levamisole at 7 mg kg-1 and naphthalophos at 30 mg kg-1 had efficiences of 89 and 66%, respectively, against SR80 Ostertagia and 99 and 19% against Nematodirus, all but the last of these being significant reductions in worm burdens. The resistant SR80 Ostertagia occurred on a research station, but possibly originated from a property which 3 years earlier had supplied ewes to the station. The use of benzimidazole anthelmintics and subsequent grazing on worm-free pasture may have enhanced the level of resistance. A relationship was established between egg counts and adult worm counts 10 days post-treatment, which suggested that for Ostertagia the worm count could be predicted from the geometric mean egg count from about 10 animals. Thus, where an Ostertagia population is suspected of being resistant, an anthelmintic efficiency assay using pre- and post-treatment faecal egg counts should provide a satisfactory diagnostic procedure.
Collapse
|
124
|
Newby TJ, Yazwinski TA, Presson BL, Holtzen HM, Bischoff MJ, Featherstone HE. Effect of the morantel sustained-release bolus, used during one grazing season, on the sensitivity of Ostertagia and Cooperia to morantel tartrate in calves. Am J Vet Res 1985; 46:424-5. [PMID: 3994107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Infective 3rd-stage larvae of Ostertagia and Cooperia, obtained from the feces of nonmedicated and morantel sustained-release bolus (MSRB)-treated calves, were orally administered to 2 groups of parasite-free calves. After a 42-day maturation period, a therapeutic dose of morantel tartrate was administered to half of the calves from each group. All calves were necropsied 7 days after treatment. After comparing the nematode counts for the nonmedicated and morantel-treated calves of each group, morantel tartrate was demonstrated to be equally effective against the nonmedicated-derived and MSRB-derived nematode populations. The sensitivity of Ostertagia spp and Cooperia spp to morantel tartrate, therefore, was not diminished after use of the MSRB for a single grazing season.
Collapse
|
125
|
Snider TG, Williams JC, Knox JW, Roberts ED, Romaire TL. Persistence of dead Ostertagia ostertagi in the abomasal mucosa following anthelmintic treatment. Vet Rec 1985; 116:69-72. [PMID: 3838393 DOI: 10.1136/vr.116.3.69] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Anthelmintic trails, conducted with albendazole, fenbendazole and ivermectin for efficacy against gastrointestinal nematodes, principally inhibited early fourth larval stages of Ostertagia ostertagi in naturally infected cattle. Cattle wee slaughtered seven to 20 days after treatment. O ostertagi was the predominant abomasal nematode recovered with occasional small numbers of Haemonchus species and Trichostrongylus axei. Control calves uniformly had very large O ostertagi infections, primarily early fourth stage larvae. Viable surviving worms and variable numbers of dead and degenerate worms were recovered in abomasal contents and washings. These O ostertagi larvae and adults were characterised by adherent debris or proteinaceous material, degenerated cuticles and distortion of internal structures. This study demonstrated the necessity for proper timing of slaughter for anthelmintic trial evaluation to allow clearance of dead nematodes, specifically O ostertagi larvae which are sequestered in the abomasal glandular tissue. Nematode collection within seven to 12 days after treatment will include dead and degenerate larval nematodes. The peripheral coating of larvae was suggestive of the Splendore-Hoeppli effect which has been associated with immunological responsiveness. The antigenic stimulus for this material and the lymphocyte and eosinophil infiltration was suspected to be early fourth stage O ostertagi larvae within the mucosa but was not identified definitively.
Collapse
|
126
|
Watkins AR, Slocombe JO, Fernando MA. The effects of single and multiple doses of thiabendazole on growing and arrested stages of the rabbit stomach worm Obeliscoides cuniculi. Vet Parasitol 1984; 16:295-302. [PMID: 6542726 DOI: 10.1016/0304-4017(84)90047-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Preliminary observations, using 5 rabbits carrying long-standing infections, indicated that single doses of thiabendazole were effective against adult O. cuniculi and that repeated doses may have had some effect on arrested larvae. A multiple dosing regime, consisting of 1 dose at 110 mg kg-1 body weight followed by 8 doses at 70 mg kg-1 body weight at 4-h intervals, was successful in removing 99.12% of developing worms and 86.04% of arrested larvae.
Collapse
|
127
|
Williams JC, Knox JW, Marbury KS, Kimball MD, Scheide SW, Snider TG, David MU. Efficacy of fenbendazole against inhibited larvae of Ostertagia ostertagi in yearling cattle. Am J Vet Res 1984; 45:1989-93. [PMID: 6497097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Efficacy of fenbendazole, at doses of 7.5 and 10.0 mg/kg of body weight, against inhibited early 4th-stage larvae of Ostertagia ostertagi and other nematodes of the abomasum and intestinal tract, was investigated in naturally infected yearling heifers in late May 1982. In Louisiana, this is near the end of the period (March to May) in which maximal numbers of inhibition-prone larvae are acquired. The mean numbers of O ostertagi in 10 untreated control cattle were: adults, 4,880; developing 4th-stage larvae, 12,546; and inhibited early 4th-stage larvae, 167,931. At the 7.5 mg/kg dose level (10% liquid suspension) in 10 cattle, percentage reduction of O ostertagi in comparison with controls was: adults, 95.7%; developing 4th stages, 91.1%; and inhibited 4th stage, 55.0%. Percentage reductions of other genera were as follows: abomasum--Trichostrongylus axei, 99.6%; Haemonchus sp, 95.1%; intestinal tract--Cooperia spp, 97.8%; Trichostrongylus colubriformis, 100.0%; and Oesophagostomum radiatum 4th stage and adults, 100.0%. At the 10.0 mg/kg dose (10% liquid suspension) in 11 cattle, the percentage reduction of O ostertagi in comparison with controls was: adults, 98.6%; developing 4th stages, 92.9%; and inhibited 4th stage, 80.0%. Percentage reductions of other genera were: abomasum--T axei, 99.9%; Haemonchus sp, 98.8%; intestinal tract--Cooperia spp, 99.3%; T colubriformis, 100.0%; and Oes radiatum 4th stage and adults, 100.0%. Variability of efficacy against inhibited larvae was observed, particularly at the 7.5 mg/kg dose; at this dose, 7 of the 10 heifers in the group yielded in excess of 54,000 surviving larvae.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
128
|
Ibarra OF, Jenkins DC. The relevance of in vitro anthelmintic screening tests employing the free-living stages of trichostrongylid nematodes. J Helminthol 1984; 58:107-12. [PMID: 6747252 DOI: 10.1017/s0022149x00028583] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The response of the free-living stages of Nippostrongylus brasiliensis, Nematospiroides dubius, Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia ostertagi to a wide variety of antiparasitic agents in vitro was investigated. All the major broad spectrum veterinary anthelmintics showed good activity against each of these worms with EC50 values varying from about 0.0002 mg/l for certain benzimidazoles and ivermectin to about 6.5 mg/l for febantel. Of 22 known narrow spectrum anthelmintics useful only against H. contortus and/or helminths other than trichostrongyles, only 10% showed good activity at concentrations equal to or less than 10.0 mg/l. Further, only one of 15 antiprotozoal agents showed good activity in these tests at the 10.0 mg/l level. The screening test employing free-living Nippostrongylus brasiliensis was selected for an extended trial where the evaluation of 1400 miscellaneous organic chemicals was undertaken. Approximately 10% of these showed activity at concentrations equal to or less than 10.0 mg/l. It is concluded that in vitro screening tests employing the free-living stages of these five genera of nematodes afford simple yet effective means for selecting relevant compounds for further evaluation as possible leads to new broad spectrum anthelmintics for use in ruminants. However, tests using the free-living stages of these worms, including H. contortus, are unsuitable for detecting narrow spectrum 'specifics', e.g., for the treatment of haemonchiasis.
Collapse
|
129
|
Hall CA, Oddy VH. Effect of cimetidine on abomasal pH and Haemonchus and Ostertagia species in sheep. Res Vet Sci 1984; 36:316-9. [PMID: 6463375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Cimetidine, a histamine H2-receptor blocking agent which reduces gastric acid flow in simple stomach animals was administered directly into the abomasum of sheep at 100 mg kg-1 twice daily for five consecutive days and again on the eighth day. The drug caused a significant increase in the pH values of the abomasal contents and was highly effective in reducing the adult population of Haemonchus contortus (100 per cent) and Ostertagia circumcincta (70 per cent) in the abomasum of sheep. The possibility of using cimetidine as a method of treating abomasal nematode parasitism is discussed.
Collapse
|
130
|
Sangster NC, Prichard RK. Uptake of thiabendazole and its effects on glucose uptake and carbohydrate levels in the thiabendazole-resistant and susceptible Trichostrongylus colubriformis. Int J Parasitol 1984; 14:121-6. [PMID: 6735575 DOI: 10.1016/0020-7519(84)90038-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
131
|
Martin PJ, Anderson N, Lwin T, Nelson G, Morgan TE. The association between frequency of thiabendazole treatment and the development of resistance in field isolates of Ostertagia spp. of sheep. Int J Parasitol 1984; 14:177-81. [PMID: 6735581 DOI: 10.1016/0020-7519(84)90046-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
132
|
Herd RP, Streitel RH, McClure KE, Parker CF. Control of hypobiotic and benzimidazole-resistant nematodes of sheep. J Am Vet Med Assoc 1984; 184:726-30. [PMID: 6725108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
In studies comprising a total of 117 naturally infected crossbred lambs, it was found that lambs turned out to spring pasture were exposed to immediate infection with overwintered Ostertagia, Nematodirus, and Trichostrongylus spp, but did not acquire Haemonchus contortus infection until July. With all species, there appeared to be only one major disease-producing generation of worms per year; it was responsible for serious worm burdens and clinical disease from July onward. High frequencies of hypobiosis (arrested development) were demonstrated in H contortus (98% to 100%), Ostertagia circumcincta (89% to 96%), and Nematodirus filicollis (77% to 90%) by late November; Trichostrongylus spp comprised most of the adult (egg-laying) worm population at that time. The onset of hypobiosis appeared to be induced by seasonal stimuli rather than by host-immune responses. The results of these studies showed benzimidazole resistance to be a major problem. In the first year, fenbendazole (5 mg/kg) reduced worm burdens by 46% and 20% in September and December, respectively. In December of the second year, levamisole (8 mg/kg) reduced worm burdens by 99%, thiabendazole (44 mg/kg) by 55%, fenbendazole (5 mg/kg) by 47%, and fenbendazole (15 mg/kg) by 11%. Levamisole was highly efficient (99%) against adult worms, hypobiotic worms, and benzimidazole-resistant worms. Ostertagia circumcincta was strongly resistant to the benzimidazole drugs at all dosages tested, while H contortus and Trichostronglylus spp were partially resistant. There was no evidence of reversion of resistant worms to susceptibility on this farm, even though benzimidazole drugs had not been used for 9 years.
Collapse
|
133
|
Berger H, Garces TR, Wang GT, Gale GO, Steller WA, Simkins KL. Anthelmintic efficacy, safety, and residue evaluation of levamisole gel formulation in cattle. Am J Vet Res 1984; 45:162-4. [PMID: 6703451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Anthelmintic efficacy, safety, and residue studies were conducted in beef calves using a levamisole gel formulation. The effectiveness of levamisole gel and tablet formulations was studied in 30 calves with experimental infection of Ostertagia ostertagi. Removal of 33- to 34-day-old O ostertagi was 99.6% and 97.7%, for the gel and tablet formulation, respectively, when administered orally to supply 8 mg of levamisole HCl equivalent/kg of body weight. A comparative blood concentration study was also used to demonstrate bioequivalence of the levamisole gel to the tablet formulation. In a cross-over-designed test, 5 cattle/treatment group were dosed orally with levamisole 11.5% gel or levamisole tablets at the dosage rate of 8 mg of levamisole HCl/kg. Blood levamisole values were similar with the levamisole gel and tablet formulations. In a safety study, 3 groups of 6 calves each were given levamisole gel orally to provide 8, 24, or 40 mg of levamisole HCl/kg. A 4th group served as controls. Adverse clinical signs were not observed in cattle treated with the recommended dosage level of 8 mg/kg. Transient salivation was noticed in 1 placebo control calf, 2 calves given 24 mg/kg, and 4 calves given 40 mg/kg. Edible tissues from cattle given a single oral dose of levamisole gel (8 mg/kg) were analyzed for drug residues 2 hours and 2, 3, 5, and 7 days after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
|
134
|
Jenkins DC, Ibarra OF. Nematospiroides dubius: response of the late fourth-stage larva to anthelmintics in vitro. ZEITSCHRIFT FUR PARASITENKUNDE (BERLIN, GERMANY) 1984; 70:395-402. [PMID: 6741225 DOI: 10.1007/bf00927827] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Approximately 60% of fourth-stage larvae of Nematospiroides dubius recovered from mice 6 days after infection, developed to the young adult stage when cultured over a 7-day period in a complex medium in vitro. Larvae at the late fourth stage of development were found to be highly susceptible to most broad spectrum anthelmintics under in vitro conditions, the benzimidazole, imidazothiazole, pyrimidine, isothiocyanate and macrocyclic lactone compounds all being active at very low concentrations. Narrow spectrum anthelmintics active only against ascarids, pinworms, filariae, cestodes or trematodes had little or no effect on these larvae. Ineffective also were those chlorinated hydrocarbon, substituted phenol and salicylanilide compounds known to affect Haemonchus but not trichostrongylid worms in general. It is concluded that in vitro assays employing larvae of N. dubius are useful for the stringent screening of compounds for broad spectrum antitrichostrongyle activity. Used in conjunction with in vivo screens employing N. dubius in mice, they also afford means for detecting intrinsic activity against the parasite in a system free from any complicating host pharmacokinetics.
Collapse
|
135
|
Boisvenue RJ, Brandt MC, Galloway RB, Hendrix JC. In vitro activity of various anthelmintic compounds against Haemonchus contortus larvae. Vet Parasitol 1983; 13:341-7. [PMID: 6686387 DOI: 10.1016/0304-4017(83)90050-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Twenty-five known anthelmintic compounds were evaluated in vitro against the highly motile exsheathed non-feeding third-stage of Haemonchus contortus larvae. Activity was based on lack of motility or death of larvae after 24 h of chemical exposure. Six compounds (avermectins, closantel, levamisole, morantel, phenylhydrazone and ticarbodine) were active at a concentration of 100 micrograms cm-3 or less. The most active compounds were avermectins and levamisole. When higher in vitro concentrations were used, ten compounds (bephenium, coumaphos, dichlorovos, disophenol, hygromycin b, methyridine, parbendazole, phenothiazine, pyrantel and thiabendazole) exhibited activity. Nine compounds were found to be inactive; among these were the new benzimidazoles, i.e., albendazole, fenbendazole, mebendazole and oxibendazole. Because of the inactivity of the new benzimidazoles, this in vitro system is unsuitable as a routine screening tool. Also, the system appears to favor drugs that act quickly through percuticular entry. In an initial group of 5280 untested compounds, 254 (4.8%) exhibited in vitro activity at 100 micrograms cm-3 against the non-feeding larvae stage. The exogenous and in vitro cultivation techniques required for collecting, cleaning and exsheathing the larvae are described.
Collapse
|
136
|
Honde C, Bueno L. Stimulatory effects of prostaglandin F2 alpha on faecal egg production in Haemonchus contortus infected sheep. Res Vet Sci 1983; 35:291-4. [PMID: 6665312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The effect of prostaglandin F2 alpha on the pattern of faecal egg count was tested in 10- to 12-month-old sheep infected with 20,000 Haemonchus contortus larvae. Prostaglandin was infused intravenously 25, 50 and 75 days after infection for four hours at a rate of 5 micrograms/kg/minute and the egg counts in the faeces were determined daily for 110 days. Treatment on days 50 and 75 was followed by a significant rise in egg count lasting 19 and 12 days respectively. This observed rise seems to be related to a resumption of development of arrested larvae induced by prostaglandin treatment, and a hypothesis is proposed to explain its initiation.
Collapse
|
137
|
Waller PJ, Dobson RJ, Donald AD. Further studies of the effect of selection with levamisole on a benzimidazole resistant population of Ostertagia spp. of sheep. Int J Parasitol 1983; 13:463-8. [PMID: 6642861 DOI: 10.1016/s0020-7519(83)80009-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
138
|
Jones RM, Bliss DH. The susceptibility of Ostertagia and Cooperia to morantel tartrate after extended exposure to the morantel sustained release bolus. Vet Parasitol 1983; 12:329-36. [PMID: 6684361 DOI: 10.1016/0304-4017(83)90039-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
139
|
Hennessy DR, Lacey E, Prichard RK. Pharmacokinetic behaviour and anthelmintic efficacy of 1-n-butyl carbamoyl oxfendazole given by intramuscular injection. Vet Res Commun 1983; 6:177-87. [PMID: 6880009 DOI: 10.1007/bf02214911] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Oxfendazole (OFZ) was chemically modified to 1-n-butyl carbamoyl OFZ (C4-OFZ) in an attempt to improve the solubility of OFZ and enable it to be administered by injection. After intramuscular injection to sheep and cattle, C4-OFZ was metabolised to OFZ which resulted in higher plasma OFZ concentrations that persisted for a considerably longer period than those observed following administration of OFZ orally. The anthelmintic efficacy of injected C4-OFZ was tested, in sheep, against strains of Trichostrongylus colubriformis, Haemonchus contortus and Ostertagia circumcincta, which were highly resistant to benzimidazoles. In all cases, the C4-OFZ treatment showed a significant improvement in efficacy over the conventional oral OFZ drench.
Collapse
|
140
|
Van Schalkwyk PC, Geyser TL, Rezin VS. [Two cases of Ostertagia spp. in sheep showing resistance to benzimidazole anthelmintics]. J S Afr Vet Assoc 1983; 54:93-8. [PMID: 6631911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Two field isolates of Ostertagia spp. of sheep from the Swellendam and Malmesbury districts in the south-western Cape were shown to be resistant to benzimidazole anthelmintics. At therapeutic dosage rates albendazole was 32,5%, thiabendazole 0%, oxfendazole 14,9% and morantel 91,4% effective against the adult stage of Ostertagia spp. in naturally infested lambs at Swellendam. Efficacy against the adult stage of the same isolate of Ostertagia spp. in artificially infested sheep in the laboratory was tested at dosage rates of albendazole 3,8% mg/kg or 7,6 mg/kg, mebendazole 15 mg/kg, levamisole 7,5 mg/kg and morantel 14,5 mg/kg and varied from 0%, 0%, 1,9% 53,9% and 87,0% respectively. Albendazole, the only anthelmintic tested against the Malmesbury strain of Ostertagia spp. was 9,8% effective against the adult stage in naturally infested lambs. Trichostrongylus spp. and Nematodirus spp. simultaneously present in these animals were fully susceptible to all the anthelmintics tested.
Collapse
|
141
|
Barton NJ. Development of anthelmintic resistance in nematodes from sheep in Australia subjected to different treatment frequencies. Int J Parasitol 1983; 13:125-32. [PMID: 6853014 DOI: 10.1016/0020-7519(83)90002-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
142
|
Cawthorne RJ, Whitehead JD. Isolation of benzimidazole resistant strains of Ostertagia circumcincta from British sheep. Vet Rec 1983; 112:274-7. [PMID: 6687770 DOI: 10.1136/vr.112.12.274] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Two strains of Ostertagia circumcincta were isolated from sheep in Great Britain; one (CVL strain) from a breeding flock maintained at the Central Veterinary Laboratory, the other (H2 strain) from a commercial flock in southern England. Their resistance to benzimidazole anthelmintics was assessed by means of in vitro egg hatch assays and slaughter trials. In vitro egg hatch assays gave calculated ED50 estimates of 0.799 micrograms thiabendazole/ml for the CVL strain and 0.794 micrograms thiabendazole/ml for the H2 strain, compared with ED50 estimates of 0.038 micrograms thiabendazole/m and 0.036 micrograms thiabendazole/ml for two known susceptible strains of O circumcincta. There was a 40.7, 28.4 and 66.9 per cent reduction in the group mean worm burdens of lambs infected with the CVL strain following treatment with thiabendazole, fenbendazole and oxfendazole, respectively, and 23.8, 0.0, 79.6, 52.7, 99.9 and 100 per cent reduction in the group mean worm burdens of lambs infected with the H2 strain following treatment with thiabendazole, fenbendazole, oxfendazole, albendazole, levamisole and ivermectin, respectively. Detailed field histories for both strains are given.
Collapse
|
143
|
Eysker M, Jansen J, Boersema JH, Lewing-Van der Wiel PJ. Development of benzimidazole resistance in a Haemonchus contortus strain in the Netherlands following fenbendazole treatment of ewes at parturition. Res Vet Sci 1983; 34:46-9. [PMID: 6836180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In contrast to observations in former years treatment of ewes after parturition with 5 to 7.5 mg/kg fenbendazole was not fully effective in removing Haemonchus contortus. Comparison of the H contortus populations in the lambs of these ewes and those of untreated ewes later in the year revealed that the treatment resulted in fenbendazole resistance and also in side resistance to other benzimidazoles. Though the faecal egg counts of the treated ewes were low, the prophylactic effect of the treatment on the population build up of H contortus in the lambs was very limited.
Collapse
|
144
|
Hall CA, Ritchie L, Kelly JD. Changes in resistance in mixed infections of susceptible and benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis passaged in sheep. Res Vet Sci 1983; 34:55-7. [PMID: 6836181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Benzimidazole resistant strains of Haemonchus contortus and Trichostrongylus colubriformis were each diluted with equal numbers of their respective susceptible genotypes and passaged in separate worm-free sheep. The progeny of the mixed susceptible and resistant infections were diluted with equal numbers of susceptible genotypes before passaging on two further consecutive occasions in worm-free sheep. In H contortus the amount of thiabendazole required to prevent a 50 per cent egg hatching (LC50) was reduced at each generation, but the reduction was significant (P less than 0.05) only at the third passage. In T colubriformis the LC50 for thiabendazole was reduced only at the first passage and thereafter remained constant. The reduction was not significant. In another experiment, the dilution with susceptible genotypes was made only at the first passage. Thereafter for two further generations the progeny produced from the mixed infection were passaged in worm-free sheep. In H contortus a reduced amount of thiabendazole was required to prevent a 50 per cent egg hatching at each generation, but did not reach a level of significance. The result for T colubriformis was identical to the continuous dilution experiment.
Collapse
|
145
|
Davey KG, Sommerville RI, Rogers WP. The effect of ethoxyzolamide, an analogue of insect juvenile hormone, nor-adrenaline and iodine on changes in the optical path difference in the excretory cells and oesophagus during exsheathment in Haemonchus contortus. Int J Parasitol 1982; 12:509-13. [PMID: 7160957 DOI: 10.1016/0020-7519(82)90045-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
146
|
Kaur R, Sood ML. Haemonchus contortus: the in vitro effects of DL-tetramisole and rafoxanide on glycolytic enzymes. Int J Parasitol 1982; 12:585-8. [PMID: 7160961 DOI: 10.1016/0020-7519(82)90056-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
147
|
Kirsch R, Schleich H. Morphological changes in trichostrongylid eggs after treatment with fenbendazole. Vet Parasitol 1982; 11:375-80. [PMID: 6892181 DOI: 10.1016/0304-4017(82)90105-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The influence of daily doses of 0.05-0.1 mg fenbendazole/kg body weight on egg development was tested in twenty-seven lambs artificially infected with Haemonchus contortus plus Trichostrongylus colubriformis or Ostertagia circumcincta, as well as in two additional sheep naturally infected with Nematodirus spp. Atypical eggs were detected before a reduction in the number of eggs. Atypical eggs had blastomeres of different sizes and shapes; knot-like, crater-like or bubble-like. In isolated cases eggs with atypical first larvae were recognizable. Morphologically changes eggs occurred in the reproductive organs of female O. circumcincta worms. None, or only a very small number of third stage larvae, could be cultured from the faeces of treated sheep.
Collapse
|
148
|
Lyons ET, Drudge JH, Tolliver SC. Ivermectin: activity against larval Strongylus vulgaris and adult Trichostrongylus axei in experimental infections in ponies. Am J Vet Res 1982; 43:1449-50. [PMID: 6896612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Activity of ivermectin, administered IM at the dosage rate of 200 micrograms/kg of body weight, was evaluated in controlled tests against migrating larvae of Strongylus vulgaris and adult Trichostrongylus axei in experimental infections in 6 ponies raised worm-free. Ponies were given 2,190 or 2,400 infective 3rd-stage larvae of S vulgaris at 7 days before treatment and 22,000 or 22,750 infective 3rd-stage larvae of T axei at 42 or 45 days before treatment. Three ponies were given ivermectin plus vehicle, and 3 ponies were given the vehicle only; the ponies were euthanatized 7 or 9 days after treatment. At necropsy, 4th-stage S vulgaris larvae were not recovered from visceral arteries of the 3 ivermectin plus vehicle-treated ponies, but 21 to 40 larvae were recovered from each of the 3 vehicle-treated ponies. Also at necropsy, adult T axei (140 specimens) were recovered from only 1 ot the 3 ivermectin plus vehicle-treated ponies, but 4,610 to 6,410 specimens were found in each of the 3 vehicle-treated ponies. Toxicosis was not observed after treatment.
Collapse
|
149
|
Hall CA, Ritchie L, Kelly JD. Effect of removing anthelmintic selection pressure on the benzimidazole resistance status of Haemonchus contortus and Trichostrongylus colubriformis in sheep. Res Vet Sci 1982; 33:54-7. [PMID: 7134649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
|
150
|
Lyons ET, Tolliver SC, Drudge JH. Controlled test of the efficacy of the feed premix formulation of crufomate on the parasites of the gastrointestinal tract and lungs of dairy calves. Am J Vet Res 1982; 43:1072-4. [PMID: 6213184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Activity of the feed premix formulation (M-1839) of crufomate against helminths of the gastrointestinal tract and lungs of cattle was determined in a controlled test. Eight calves were treated and 7 were nontreated. The dosage rate of crufomate was 17 mg of active drug/kg of body weight daily for 3 consecutive days. Removal activity was high against mature Cooperia oncophora (99%) and C punctata (96%) and immature Cooperia spp (87%). Removal of mature Ostertagia ostertagi was 68%. The removal of strongyloides papillosus and Bunostomum phlebotomum was 72% and 67%, respectively, but only a few specimens were present in the nontreated calves. Efficacies against the other mature and immature species of nematodes ranged from 0% to 34%. Lungworms (Dictyocaulus viviparus) were not effectively removed.
Collapse
|