Glutamate-gated chloride channel subunit cDNA sequencing of Cochliomyia hominivorax (Diptera: Calliphoridae): cDNA variants and polymorphisms

The New World screwworm (NWS) Cochliomyia hominivorax (Coquerel) is one of the major myiasis-causing flies that injures livestock and leads to losses of similar to US$ 2.7 billions/year in the Neotropics. Ivermectin (IVM), a macrocyclic lactone (ML), is the most used preventive insecticide for this parasite and targets the glutamate-gated chloride (GLUCL alpha) channels. Several authors have associated altered GluCl alpha homologues to MLs resistance in invertebrates, although studies about resistance in NWS are limited to other genes. Here, we aimed to characterise the NWS GluCl alpha (ChGluCl alpha) cDNA and to search for alterations associated with IVM resistance in NWS larvae from a bioassay. The open reading frame of the ChGluCl alpha comprised 1,359 bp and encoded a sequence of 452 amino acids. The ChGluCl alpha cDNAs of the bioassay larvae showed different sequences that could be splice variants, which agree with the occurrence of alternative splicing in GluCl alpha homologues. In addition, we found cDNAs with premature stop codons and the K242R SNP, which occurred more frequently in the surviving larvae and was located close to mutation (L256F) involved in ML resistance. Although these alterations were in low frequency, the ChGluCl alpha sequencing will allow further studies to find alterations in the gene of resistant natural populations.