In vitro evaluation of ivermectin, moxidectin, albendazole and pyrantel against cyathostomins of horses

Abstract

Cyathostomins are the most prevalent nematodes of horses, and multidrug resistance has been reported worldwide. There is a need to implement alternative drug monitoring analytical tests. The objective of this study was to determine the consistency (5 repetitions) of the larval migration on agar test (LMAT) using ivermectin, moxidectin, pyrantel or albendazole against cyathostomin infective-stage larvae in eight different concentrations. LMAT showed a strong coefficient of determination (R 2 > 0.91), between the test repetitions (n=5). The average 50% effective concentration (EC50) for ivermectin, moxidectin, pyrantel and albendazole were 0.0404, 0.0558, 0.0864 and 0.0988 nMol, respectively. The results of the EC50 for albendazole showed the greatest range of concentration. Ivermectin and moxidectin had the lowest in between-test variation. In the future, internationally certified susceptible isolates could be used for screening new drug candidates, or to follow up the pattern of drug efficacy from field populations.Keywords: Horse, Anthelmintics, In vitro test, parasites. ResumoCiatostomíneos são os nematodas mais prevalentes em equinos e a resistência múltipla foi relatada em todo o mundo. Existe a necessidade de implementar o monitoramento dos produtos com testes analíticos alternativos. O objetivo deste estudo foi determinar a consistência (5 repetições) do teste de migração larval em ágar (TMLA) usando ivermectina, moxidectina, pirantel e albendazole contra larvas infectantes de ciatostomíneos em oito concentrações diferentes. O TMLA demonstrou um coeficiente de determinação (R 2 ) acima de 0,91 entre as repetições do teste. A concentração efetiva para 50% (CE50) para ivermectina, moxidectina, pirantel e albendazole foi de 0,0404; 0,0558; 0,0864 e 0,0988 nMol, respectivamente. A CE50 do albendazole demonstrou a maior amplitude entre os testes. A ivermectina e a moxidectina tiveram as menores variações das doses entre as repetições. No futuro, isolados certificados susceptíveis poderão ser testados com o TMLA para indicação de novos produtos e mesmo para acompanhar o perfil de eficácia de populações do campo.Palavras-chave: Cavalos, anti-helmínticos, teste in vitro, parasitos.

Helminths and their management in Swiss Army horses: differences between riding horses and pack horses evidence the need of improvement

“…Pyrantel was regularly used in 96,2 % of riding horses, and also in 16,2 % of the pack horses. The use of this anthelmintic could probably be omitted in many cases, since reduced efficacy of pyrantel against Cyathostominae has been reported in many studies, 7,27,32,38,56 including Switzerland, 31 particularly when comparing data with MLs. The widely adopted strategy against AR spreading, promoting the use of alternating between drugs, has not been scientifically proven useful, 22 and one study in fact confirmed that changing drug classes between anthelmintic treatments did not influence the development of AR.…”

In Vitro Inhibiting Effects of Three Fungal Species on Eggs of Donkey Gastrointestinal Strongyles

“…Gastrointestinal strongyles (GIS), especially cyathostomins, are considered some of the most common and important donkey helminths [ 4 , 5 ]. In horses, the administration of anthelmintic drugs, mainly benzimidazoles, macrocyclic lactones, and tetrahydropyrimidines, may substantially reduce the prevalence of GIS infections [ 6 , 7 ]. Nevertheless, the control of GIS in dairy donkey farms may be problematic.…”