Molecular characterization of the nematode Heterakis gallinarum (Ascaridida: Heterakidae) infecting domestic chickens (Gallus gallus domesticus) in Tunisia

Abstract

Heterakis gallinarum is one of the most recurrently diagnosed nematodes within the gastrointestinal tract of galliform birds.In the present study, we investigated the genetic diversity of 96 H. gallinarum collected from free-range chickens from different localitiesin Tunisia. We assessed phylogeny and genetic variability using the internal transcribed spacers (ITS) of the nuclear ribosomal DNAand the mitochondrial cytochrome c oxidase subunit I gene. Haplotype and nucleotide diversities indicate that H. gallinarum is aspecies with extremely low genetic diversity. Based on the networks and phylogenetic trees, there was strong support for the absenceof significant geographical structuring among the H. gallinarum populations in different localities in Tunisia. Mismatch distributionsand neutrality tests of both genetic markers suggest that at least one expansion event occurred in the population demographic historyof H. gallinarum. Our data showed a lack of population structure using the pairwise fixation index (FST) and an extensive gene flow. Itindicated that the most likely major contributor to the low genetic diversity and gene flow is the movement of the parasitized birds; inother words, the frequency of the poultry trade considerably affects patterns of worm gene flow.