First Detection of Eustrongylides excisus in Mosquito Fish (Gambusia holbrooki) from Lake Eğirdir

In this study, the presence of Eustrongylides excisus, one of the zoonotic nematodes, was determined for the first time in Gambusia holbrooki from Lake Eğirdir. 70 Gambusia holbrooki samples were examined macroscopically for Eustrongylides excisus infection. The four parasite samples were recorded in 4 fish, one in each fish. The parasitic species identification was performed using the classical method on E. excisus samples isolated from the host fish, then PCR was performed on 18S rDNA. As a result of molecular analyses, 18S rDNA loci fragment of E. excisus was determined to be 941 bases long and registered to the NCBI data system with accession number PP333225. The taxonomic position of the present isolates and other Eustrongylides isolates registered in NCBI was evaluated through a phylogenetic analysis. It was determined that the isolates in this study had similar sequences to the Eustrongylides samples previously reported from Türkiye. In addition, the isolates of this study were found to have close similarity to Eustrongylides isolates from countries geographically close to Türkiye, such as Iran and Italy, while the similarity rate with Eustrongylides isolates from countries such as China, Brazil and India was found to be low. As a result of this study, it was determined for the first time that Gambusia holbrooki plays a role as an intermediate host in the life cycle of E. excisus. In addition, the sequences belonging to the 18S rDNA locus of E. excisus samples from host fish were identified and contributed to the determination of the genetic characteristics of the parasite species.