Morphology and Molecular Studies of Contracaecum Larvae (Nematoda: Anisakidae) in Some Fish species from Sulaimani Province, Kurdistan Region, Iraq

Contracaecum is a genus of nematodes belonging to the family Anisakidae, that parasitise many fishes which act as an intermediate or paratenic hosts, while the piscivorous birds and mammals are definitive hosts. A total of 44 third larval stage of Contracaecum were collected from 13 infected freshwater fishes belonging to five different species in different water bodies in Sulaimani Province, Kurdistan Region, Iraq from January to the end of December 2018. In this investigation, 966 fishes were collected including six species of Nemacheilidae, five species of Cyprinidae, three species of Leuciscidae, two species of Xenocyprididae, one species of each of Bagridae, Heteropneustidae, Mastacembelidae, Mugilidae, Siluridae and Sisoridae. This study revealed that five fish species (Cyprinus carpio, Luciobarbus barbulus, L. esocinus, L. xanthopterus and Mastacembelus mastacembelus) were infected with Contracaecum larvae with the prevalence of 2.05%, 0.92%, 1.92%, 19.35% and 1.06%, respectively. The Contracaecum larvae were morphologically studied by compound light microscope and the molecular analyses was done by amplification, sequencing and comparing different gene loci (ITS1, ITS2 and COX2) of isolated third larval stage of Contracaecum. The ITS1, ITS2 and COX2 were amplified by polymerase chain reaction (PCR) and sequenced. The sequences of ITS1, ITS2 and COX2 reveal that all Contracaecum larvae from all infected fishes represented exactly one species (Contracaecum rudolphii B) based on compering and identity percentage in Gene Bank database. Phylogenetic analysis of the genotype (for ITS1) was described. The genetic characterization of the Contracaecum larvae in the present study is available in the GenBank database and they were deposited in GenBank and their accession numbers were demonstrated.