Efficacy of monepantel against lower developmental stages of a multi-resistant and susceptible Haemonchus contortus isolates: an in vitro study

Abstract

SummaryMonepantel (MOP) belongs to a new class of anthelmintic compounds, the amino-acetonitrile derivates, which have a different mode of action as the currently used anthelmintics. Many present studies confirmed the high efficacy of MOP against fourth larval and adult stages of Haemonchus contortus. The objective of this study was to determine in vitro efficacy of MOP against lower development stages (eggs, L 1 -L 3 larvae) and to compare it between resistant and susceptible isolates of H. contortus. For this purpose, two in vitro tests -egg hatch test and micro-agar larval development test were used. Results were quantified as 50 % lethal concentration (LC 50 ), 99 % lethal concentration (LC 99 ) and resistance factor (RF). This study revealed the high efficacy against lower larval stages (L 1 -L 3 ) of both resistant and susceptible strains of this parasite. Larval susceptibility was not dependent of the sensitivity status of the nematode isolate. On the other hand, ovicidal effect of MOP was very low.

Anthelmintic resistance of Haemonchus contortus from sheep flocks in Brazil: concordance of in vivo and in vitro (RESISTA-Test©) methods

“…Because of this, it is necessary to highlight the importance of using standard substances in order to establish cutoff criteria and reduce the variability of the criteria to a minimum. Although in the present study the approach used to determine the cutoff values (LC 50 ) for MPT was through the commercial anthelmintic (Zolvix ® ), it was justified by the fact that in previous studies Zolvix ® presented better performance than MPT (chemical base), for detecting resistance to LDT among H. contortus (Lecová et al, 2013;Raza et al, 2016;Kotze et al, 2018;Gainza et al, 2019).…”

Monepantel: the most studied new anthelmintic drug of recent years

“…The efficacy of MOP against lower developmental stages (eggs and L 1 –L 3 larvae) of H. contortus isolates was studied by Lecová et al (2013). In this study, two in vitro methods were used.…”

“…Both larval tests rely on the development of eggs to L 3 larvae (Coles et al 2006). The study of Lecová et al (2013) showed that MOP had no significant ovicidal effect, which means that the MOP do not affect the eggs and therefore they have the potential to develop to infective larvae. On the other hand, MOP exhibited significant larvicidal effect, what conversely means that the parasites will not be able to develop to infective larvae.…”

Comparison of biotransformation and efficacy of aminoacetonitrile anthelmintics in vitro

“…This results in a constant uncontrolled flux of ions and finally in a depolarization of muscle cells. [13] The present information about MOP has been reviewed recently. [12] MOP is also effective against nematodes' earlier larval stages (L 1 -L 3 ) and larval susceptibility is not dependent on the drug-sensitivity status of the nematode isolate.…”

“…[12] MOP is also effective against nematodes' earlier larval stages (L 1 -L 3 ) and larval susceptibility is not dependent on the drug-sensitivity status of the nematode isolate. [13] The present information about MOP has been reviewed recently. [14] Since 2010, MOP has been used in the therapy of nematode infections in sheep mostly with success.…”