Abstract
Background:
The gastrointestinal nematode, Haemonchus contortus (Barber’s pole worm), is a member of the Trichostrongilidae family with a major ovine parasite that resides in the abomasum of sheep, goats, and other ruminants. The spicule lengths provided the quickest and easiest character for separating most populations of H. contortus and Haemonchus placei.

Aim:
Detection and diagnosis of H. contortus in slaughtered small ruminants from Basrah city using PCR technique with specific genes as targets: ITS2 gene (HcI) of ribosomal DNA and (Nad4) gene of mitochondrial DNA. Then, the gene sequence was used to confirm the H. contortus Iraqi strain.

Methods:
A total of 705 slaughtered animals were examined and divided into 556 sheep and 149 goats taken from the Basrah slaughter house.

Results:
The total number of infected animals with Haemonchosis was 90, which was divided into 78 sheep and 12 goats. The total number of isolated worms from the abomasum was 2439 for both sheep and goats, with a total infection percentage of 12.76 %, which was divided into 14.02% and 8.05% in sheep and goats, respectively. The intensity of infection was about 27.1, which was divided into 27.12 and 26.91 in sheep and goats, respectively. The identification of Haemonchus spp. was molecularly performed by detecting the presence of the ITS-2 (295 bp) internal transcribed spacer gene (ribosomal DNA) and the Nad4 (800 bp) nicotinamide dehydrogenase gene (mitochondrial DNA). The process included total DNA extraction and amplification of the mentioned region with specifically designed primers. The polymerase chain reaction product was sent for sequencing analysis to determine the Iraqi strain and for the phylogenetic tree. Sequencing and phylogenetic tree showed 99% identification with two American isolates (EU084691.1 and EU084688.1) for the ITS-2 gene, while the Nad4 gene showed 100% identification with one Pakistani isolate (KJ724441.1), 99% identification with two Pakistani isolates (KJ724441.1 and KJ724524.1), and 97% identification with one Pakistani isolate (KJ724524.1).

Conclusion:
Barber’s pole worms propagated in a large infection percentage and had an abundance of eggs that were discarded. Therefore, it forms a hazard to the animal’s life, causing economic losses. Therefore, the PCR technique was a beneficial way for the genetic discovery of barber pole worms as genus Haemonchus, and ITS-2 and Nad4 gene were good results for the recognition of Haemonchus contortus as a genus and species. The isolated genes were deposited in the Gene Bank under the accession numbers LC275893.1, LC275894.1, LC275895.1, LC275896.1, LC275897.1,
LC275898.1, LC275899.1, LC275900.1, and LC275901.1 as the Iraqi strain.

Key words: Haemonchus spp.; Basrah slaughterhouse; Polymerase chain reaction; Molecular study.