Clinical, pathological, and molecular characterization of Coenurus cerebralis infection in sheep from Salah Aldeen province, Iraq

Coenurosis is a neurological ailment caused by the larval stages (Coenurus cerebralis) of Taenia multiceps, a parasite that significantly affects sheep production worldwide. This study aimed to determine the prevalence of C. cerebralis infection and to characterize it clinically, pathologically, and molecularly in infected sheep from 15 districts of Salah Aldeen Province, Iraq. A cross- sectional study extending from March 2024 to February 2025 was conducted, involving the clinical examination of 450 sheep. Sheep exhibiting clinical signs of coenurus infection were further subjected to postmortem for confirmation of the suspected disease. Molecular identification of coenurus was done by PCR amplification of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and the internal transcribed spacer 1 (ITS1) region. A total of 39 sheep were confirmed for coenurosis, resulting in an overall prevalence of 8.67% (95% CI: 6.28-11.67%). There was a wide spatial variation among the districts, with prevalence ranging from 3.33% in Fares district to 16.67% in Tikrit district. The most common clinical signs associated with infected sheep included circling behaviour (76.9%), head tilt (64.1%), blindness (43.6%), and ataxia (38.5%). The highest number of cases was recorded during winter months (December-February) with 14 cases (35.9%) followed by spring (March-May) with 11 cases (28.2%). Summer months (June-August) showed the lowest occurrence (6; 15.4%) followed by Autumn (September-November) with 8 cases (20.5%). Postmortem examination revealed that coenurus cysts were predominantly located in the cerebral cortex (48.7%) and cerebellum (35.9%) of infected sheep. In most confirmed cases, PCR successfully amplified fragments of the cox1 and ITS1 genes, confirming the morphological diagnosis. This study demonstrates that C. cerebralis infection represents a significant health concern for the sheep of Salah Aldeen province, which could potentially hinder the economic sheep production in the study area. The study highlights the importance of integrated clinical, pathological, and molecular approaches for accurate diagnosis of the disease and the data generated provides a valuable baseline epidemiological information for the development of effective and strategic prevention and control programs for coenurosis in the region.