Frequency of benzimidazole resistance inHaemonchus contortus populations isolated from buffalo, goat and sheep herds

Abstract

Anthelmintic resistance is an increasing problem that threatens livestock production worldwide. Understanding of the genetic basis of benzimidazole resistance recently allowed the development of promising molecular diagnostic tools. In this study, isolates of Haemonchus contortus obtained from goats, sheep and buffaloes raised in Brazil were screened for presence of the polymorphism Phe200Tyr in the β-tubulin 1 gene, which confers resistance to benzimidazole. The allelic frequency of the mutation conferring resistance ranged from 7% to 43%, and indicated that resistance to benzimidazole could be found in nematodes isolated from all the ruminant species surveyed. Although significant variation in the frequency of the F200Y mutation was observed between different herds or host species, no significant variation could be found in populations isolated from animals within the same herd. These findings suggest that screening of samples from a few animals has the potential to provide information about the benzimidazole resistance status of the entire herd, which would enable a considerable reduction in the costs of diagnosis for the producer. Molecular diagnosis has practical advantages, since it can guide the choice of anthelmintic drug that will be used, before its application in the herd, thus reducing the economic losses driven by anthelmintic resistance.Keywords: Anthelmintic resistance, benzimidazole drugs, molecular diagnosis, domestic ruminants, genetic polymorphisms. ResumoA resistência aos anti-helmínticos é um problema crescente que ameaça a produção pecuária em todo o mundo. A compreensão da base genética da resistência ao benzimidazol permitiu, recentemente, o desenvolvimento de métodos diagnósticos moleculares promissores. Neste estudo, isolados de Haemonchus contortus obtidos a partir de rebanhos de caprinos, ovinos e bubalinos criados no Brasil foram avaliados quanto à presença do polimorfismo F200Y no gene da β-tubulina1, o qual confere resistência ao benzimidazol. A frequência alélica da mutação variou de 7% a 43%, indicando que a resistência ao benzimidazol pode ser encontrada em nematoides isolados a partir de todas as espécies de ruminantes pesquisadas. Embora tenha sido observada variação significativa das frequências de mutação F200Y entre rebanhos/espécies hospedeiros distintos, não foi encontrada variação significativa entre populações isoladas de animais dentro de um mesmo rebanho. Estes achados sugerem que a avaliação de amostras de alguns poucos animais tem o potencial de fornecer informações sobre o nível de resistência ao benzimidazol de todo o rebanho, possibilitando uma redução considerável dos custos de diagnóstico para o produtor. O diagnóstico molecular apresenta vantagens práticas, uma vez que pode guiar a escolha da base anti-helmíntica a ser utilizada antes da sua aplicação no rebanho, reduzindo, portanto, as perdas ocasionadas pela resistência aos fármacos anti-helmínticos.Palavras-chave: Resistência a anti-helmínticos, benzimidazóis, diagnóstico molecular, ruminantes domés...

Characterization of the complete mitochondrial genomes of two sibling species of parasitic roundworms, Haemonchus contortus and Teladorsagia circumcincta.

“…The phylogenomic tree based on the concatenated PCGs of the complete mt genomes (Fig. 4), placed H. contortus NZ_Hco_NP and T. circumcincta NZ_Teci_NP in their respective clades with other H. contortus and T. circumcincta strains, which are in agreement with previous studies [8][9][10]43]. However, our tree is not directly comparable to previously described phylogenetic trees that performed different analyses and compared a broader set of taxa, but mainly because the trees were based on the ITS rDNA nuclear genetic markers [15,63,64].…”

“…Parasitic roundworms belonging to the Haemonchidae family are able to infect a range of ruminant hosts. For example and on communal pastures in particular, H. placei is primarily a cattle parasite but can also infect small ruminants [6][7][8], and vice versa for H. contortus [9]. Given the increase in availability of genomic information resources [10], it is crucial for the management of parasitic diseases that readily accessible molecular tools are developed to enable end-users to easily determine which species is infecting which animal host.…”

Overview of anthelmintic resistance of gastrointestinal nematodes of small ruminants in Brazil

“…The document covers in vivo testing and field sampling of material, including questionnaires for producers, while the manual emphasizes in vitro and molecular laboratory The new molecular biology tools, which are highly accurate, can be used for the diagnosis of susceptible and resistant parasites . Molecular tests based on the analysis of polymorphisms in the target gene associated with resistance, using PCR, are highly sensitive (SILVESTRE & HUMBERT, 2000), do not require fecal cultures, and can supplement traditional diagnostic methods (NUNES et al, 2013). However, due to the extremely polygenic nature of populations, researchers have yet to discover the mechanism of drug resistance and pinpoint one or more candidates for specific markers (FORTES & MOLENTO, 2013).…”

“…This polymorphism has also more recently been associated with resistance to avermectins (MOTTIER & PRICHARD, 2008). In Brazil, Nunes et al (2013) evaluated goat, sheep and buffalo herds with respect to the presence of polymorphism which confers resistance to benzimidazole, and stated that molecular diagnosis is the guide of choice for anthelmintic drugs before they are used on the herd. Studies of molecular tests on AHR in Brazil have also been evaluated, involving testing of beta-tubulin mutations or genetic evaluations of nematodes, corroborating researches into AHR (SILVA et al, 2015;SANTOS et al, 2014;AMARANTE et al, 2014;BRASIL et al, 2012).…”

Anthelmintic resistance status of gastrointestinal nematodes of sheep to the single or combined administration of benzimidazoles and closantel in three localities in Mexico

“…and Trichostrongylus spp. from sheep in Brazil have developed simultaneous resistance to albendazole, ivermectin, levamisole, moxidectin, and closantel 21 . Multiple-anthelmintic resistance has also been reported in major sheep producing countries, such as Australia and New Zealand, and in various South American regions 1 .…”