Molecular study on nematode infection in sheep abomasa: a regional investigation in Iran and Iraq

Gastrointestinal nematodes are leading causes of loss in livestock and are the primary restriction to its profitable production, worldwide. This study was carried out to determine the prevalence and diversity of sheep abomasum nematode species in Urmia (Iran) and Soran (Iraq) slaughterhouses from October 2019 to January 2021. A total of 280 abomasa (each city 140 samples) were randomly collected from the slaughtered sheep. The abomasal content and mucosa were removed and washed. The collected nematodes were morphologically identified. Genomic DNA was extracted from identified nematodes and a fragment from the internal transcribed spacer 2 ribosomal ribonucleic acid (ITS2-rDNA) gene was amplified. In Urmia city, two species including Teladorsagia circumcincta (40.7%), and two morphotypes of Marshallagia species; Marshallagia marshalli (35.0%) and M. trifida (4.3%) were identified. In Urmia city, 52.9% of the examined sheep were infected with at least one species of nematodes. The overall prevalence of abomasa infection with nematodes in Soran city was 91.4%. In the examined sheep abomasa in Soran city, four species of nematodes were identified, including Marshallagia species with two morphotypes, M. marshalli (85.0%) and M. trifida (20.7%), Teladorsagia circumcincta (32.1%), Parabronema skrjabini (1.4%), and Haemonchus contortus (0.7%). Except for H. contortus, all the other identified nematode species were confirmed using molecular techniques. It was concluded that abomasal nematode infections are widespread in sheep particularly in Soran city. Marshallagia marshalli and T. circumcincta were most prevalent nematodes in both regions. In addition, further molecular studies are recommended to understand the intra-specific variations in the genus Marshallagia and more accurate identification of morphotypes in these regions.