Morphological and molecular characterization of Ascaridia columbae in the domestic pigeon (Columba livia domestica) and the assessment of its immunological responses.

Parasitism is a divesting problem that is frequently overlooked and may result in severe prominent clinical manifestation. This study aimed to investigate the seasonal and sexual prevalence of the gastrointestinal nematode Ascaridia columbae (A. columbae) infection among domestic pigeons in Giza governorate, Egypt, during the period from 2020 to 2021. One hundred and sixty suspected pigeons were clinically investigated. Blood & tissue samples were collected from infected birds to estimate serum zinc concentration, malondialdehyde (MDA), and nitric oxide levels. As well as tumor necrosis factor-alpha (TNF-α), interleukin 1β (IL1β) activity, and histopathological examination were estimated; also, worms were collected for morphological identification using electron microscope (SEM) and molecularly identified using polymerase chain reaction (PCR), further sequenced, and submitted in GenBank with accession number MZ343369. The average ascarid (length × breadth) were 72.4 ± 3.3 µm (70.5 - 79.9 µm) × 39.9 ± 2.5 µm (37.6 - 42.3 µm). The distinguishing morphological characteristics that have been noticed in ascarid worms were creamy white, cylindrical worm with triradiate lips with wide cephalic alae extending on both the lateral sides and filariform esophagus. In males, spicules were almost equal with the presence of precloacal chitinous-rimmed sucker. The prevalence of A. columbae infection was (63.1%) with a higher incidence in females (79.2%) than males (46.1%). The highest seasonal prevalence was observed in winter (92.5%), followed by summer and spring (87.5% and 55%), respectively while, the lowest prevalence was observed in autumn (17.5%). The intensity of worms in the infected intestine varied from 5 to 120 adult worms. The histopathological examination revealed the presence of chronic diffuse moderate catarrhal enteritis with roundworms in the lumen. Infected birds showed a significant increase in nitric oxide and MDA levels while serum zinc levels were lowered in infected pigeons. Infected pigeons revealed a marked increase in IL1-β and TNFα than apparently healthy ones.