Molecular, Histopathological, and Immunohistochemical Investigation of Peste des Petits Ruminants in Clinically Suspected Sheep in Wasit Province, Iraq

<b>Background and Aim:</b> Peste des Petits Ruminants (PPR) has recently become one of the most incidence and threatening viral diseases of sheep in Iraq, which affected notion economy through prevalence and mortality rates. Although there is wide availability of global data on epidemiology, diagnosis, pathogenesis, and treatment of this disease, crucial specific available information with extended prevalence in Iraq still requires specific research to cope. Therefore, this study investigates molecular phylogeny of PPR in sheep during outbreak and detection the histological and immunohistochemical changes in the lung and intestine tissue. <b>Materials and Methods:</b> A total of 182 sheep enrolled in this study that received to the private and official slaughterhouses in Wasit province (Iraq). The sheep examined clinically and subjected to sampling of venous blood that was tested serologically using the enzyme-linked immunosorbent assay (ELISA) and molecularly by polymerase chain reaction (PCR). Postslaughtering, tissue samples were obtained from lung and intestine for histology and immunohistochemistry detection. Phylogenic tree was build based on sequenced of some positive isolates which submitted to the NCBI-database and analysed phylogenetically. <b>Results:</b> Clinically, variable signs were identified in various sheep. The serological anti-PPR IgG antibodies identified 43.41% positive sheep that sequentially allied to mild, moderate and severe PPR cases included 53.16%, 27.85%, and 18.99%, respectively. Molecularly, 24.18% of sheep were infected with PPR, and distinct phylogenetic analysis displayed a close-relationship of study isolates to NCBI-BLAST Mali isolate (MT072487.1). The intestine showed atrophied villi, necrotic mucosal glands, infiltration of lymphocytes and plasma cells in lamina propria, marked diffuse edema, crypt disruption, and cellular necrosis; whereas in lung, macrophages invading alveolar wall, accumulation of inclusion bodies in intracellular and intracytoplasmic regions, infiltration of neutrophils and multinuclear giant cells, and existence of fibrin exudates were seen. Intensity of reaction was relatively ranged from mild (+) to moderate (++) in the intestine, while it was mild (+) in the lung. <b>Conclusion:</b> The displayed results represent the unique Iraqi study that targeted sheep PPR serologically and molecular phylogeny, concomitant with identification of histological and immunohistochemical alteration in the intestine and lung tissues. Therefore, further in depth qualitative and quantitative serological, molecular, and immunological studies focuses on relation of disease with sheep and goats are interesting to identify the prevalence rate, economic losses, and support the control and eradication efforts in Iraq.