First Molecular Characterization and Seasonality of Larvae of Trichostrongylid Nematodes in Arrested Development in the Abomasum of Iranian Naturally Infected Sheep.

Purpose: The aim of this study was to determine molecularly the species of larvae of trichostrongylid nematodes in arrested development in the abomasum of sheep from Iran and their seasonality. Methods: A total of 240 sheep abomasa were randomly collected at different seasons from Ilam abattoir in 2017–2018. The adult nematodes were isolated and identified. The mucosa of the abomasum was removed and digested using a pepsin solution. DNA from different parts of the abomasum was extracted using a SinaPureTM kit. Polymerase chain reaction (PCR) amplification was performed; the ITS2-rRNA gene was amplified using specific primers. Amplified PCR products were purified and sequenced by Bioneer Corporation (South Korea). The obtained ITS2 sequences were aligned using BLAST analysis and submitted to GenBank. Results: Morphologically, five species of adult nematodes of four genera including Haemonchus contortus, Marshallagia marshalli, Marshallagia occidentalis, Parabronema skrjabini, and Teladorsagia circumcincta were identified. Marshallagia marshalli (65.4%, 120.2 ± 28.5) had the highest prevalence during autumn. Molecularly, arrested development of larvae of M. marshalli and T. circumcincta were demonstrated in mucosa of the abomasum in autumn and early winter using PCR of the ITS-2 region of rRNA. Conclusion: The results evidenced the first molecular characterization of the larvae of trichostrongylid nematodes from abomasum of sheep from Iran. [ABSTRACT FROM AUTHOR]