Attempts to detect synergy between vaccination and anthelmintic against a drug resistant isolate of Haemonchus contortus
11
Citation
11
Reference
10
Related Paper
Citation Trend
Cite
Citations (57)
Albendazole
Eggs per gram
Cite
Citations (28)
Three anthelmintic pastes were compared in terms of their ability to suppress the output of parasite eggs in the faeces of 108 grazing horses at four sites in Britain; the horses were treated once with either ivermectin, fenbendazole or pyrantel. At each site, the horses grazed together throughout the trials which took place during the summers of 1985 and 1986. The median periods before parasite eggs reappeared in faeces were 70 days for ivermectin, 14 days for fenbendazole and 39 days for pyrantel embonate. Geometric mean faecal egg counts in the groups treated with ivermectin and pyrantel were significantly less (P less than 0.05) than in the fenbendazole group on days 21, 28, 35 and 42 after treatment. On days 49, 56, 63 and 70 the mean egg counts in the ivermectin group were significantly lower (P less than 0.05) than those in either of the other groups. The results indicated that in order to ensure minimal contamination of pastures, grazing horses treated with ivermectin paste would have required a second treatment approximately 10 weeks after the first, and to achieve similar control with fenbendazole or pyrantel embonate, a second treatment would have been required after approximately two weeks and six weeks, respectively.
Pyrantel
Eggs per gram
Cite
Citations (18)
Cite
Citations (23)
Cite
Citations (11)
Haemonchus contortus poses a severe hazard to the healthy development of the sheep industry and threatens the welfare of sheep. Ivermectin is the primary anthelmintic used for the prevention and treatment of H. contortus parasitism. However, the widespread and uncontrolled application of ivermectin has resulted in the development and spread of resistant strains of H. contortus. P-glycoprotein (P-gp) plays important roles in the pharmacology and toxicology of ivermectin, and changes in P-gp expression levels can be used to analyze the resistance of H. contortus to ivermectin. This study aimed to analyze the effects of ivermectin on P-gp expression in H. contortus L3 larvae isolated from China and to evaluate whether changes in P-gp expression levels can be used to analyze resistant H. contortus strains. In the absence of drug treatment, the ivermectin-resistant strains isolated in China showed increased expression of P-gp11 (p < 0.01) compared with sensitive strains from elsewhere, whereas the expressions of P-gp2 and P-gp9.1 were downregulated (p < 0.01). When the same strain was compared before and after drug treatment, obvious differences in expression were observed between the different strains. Ivermectin-induced P-gp expression was found to be very complex among the L3 larvae of different strains. In addition, it was confirmed that using P-gp to determine ivermectin resistance in H. contortus strains from different geographic environments can yield different results.
Cite
Citations (4)
Parasitology
Cite
Citations (21)
Membranes from both ivermectin-sensitive and -resistant Haemonchus contortus L3 larvae were examined for the presence of high affinity [3H]ivermectin binding sites. Both tissue preparations displayed high affinity drug binding sites (Kd = 0.13 nM). Receptor density (Bmax = 0.4 pmol/mg) was the same in both the sensitive and resistant nematodes suggesting that target site modification was not involved in the development of drug resistance in this particular strain of H. contortus. The H. contortus ivermectin binding site appeared to be similar to the well characterized Caenorhabditis elegans ivermectin binding site with respect to affinity for ivermectin and receptor density.
Cite
Citations (55)