First report on molecular detection of Chlamydia abortus infection in sheep flocks in Mosul, Iraq

Chlamydia abortus is considered one of the significant causes of abortion in the sheep population across the country and leads to heavy economic losses. The current study aimed to detect Chlamydia abortus infection by microscopic examination using a Modified Ziehl-Neelsen stain and conventional polymerase chain reaction in sheep flocks in Mosul, Iraq. A total of 157 different samples (49 aborted fetuses, 52 placentas, and 56 vaginal swabs) were collected from 60 flocks from August 2022 to January 2023 in different areas of Mosul. A smear was made for microscopic examination, and Biopsies were taken from the placenta and the organs of aborted fetuses for PCR use 16S rRNA gene and OMP2 gene primers. Results indicate that the proportion of positive samples in the microscopic examination was 18.47%, showed in a large number of red dot-shaped bodies in the intercellular space, while the percentage of positive samples was 11.46% for the S16rRNA gene, while it was 4.45% for the OMP2 gene in molecular diagnostics as PCR. The Sensitivity, Accuracy, and Specificity were 78, 89, and 89%, respectively, for microscopic examination by comparison with PCR as a gold standard, and it was found that there was a moderate strength association between microscopic examination and PCR. We concluded that Chlamydia could be diagnosed using a microscopic field examination when a quick diagnosis is needed. While in Molecular Diagnostics, the 16S rRNA gene was the best for confirming the detection of Chlamydia.