Eco-Epidemiology and Pathological Impact of Capillaria contorta (Capillariidae) in Semi-Captive Barbary Partridges (Alectoris barbara) in Algeria

The Barbary partridge (Alectoris barbara), an endemic game bird in Algeria, has not been systematically investigated for parasitic infections despite its ecological, economic, and conservation importance. This study provides the first eco-epidemiological and histopathological assessment of Capillaria contorta infection in birds from a semi-captive breeding center in Zeralda, Algeria. Between 2021 and 2024, 1085 pooled fecal samples and 138 postmortem examinations were analyzed using standard parasitological and histopathological methods. C. contorta showed an aviary-level overall prevalence of 32.94% and was involved in 42.02% of parasite-related mortalities, underscoring its marked pathological significance. Aviary-level prevalence varied significantly across seasons and years (p < 0.05), with higher levels recorded during environmentally favorable periods. Mixed infections with helminths, protozoa, cestodes, and ectoparasites were recorded for the first time in this host species at the aviary level, highlighting complex parasite interactions. Morphological characteristics were consistent with C. contorta. Gross examination revealed marked thickening of the esophagus and crop. Histologically, the adult nematodes were embedded within hyperplastic epithelium, with characteristic bipolar-plugged eggs and associated epithelial tunnels, accompanied by chronic inflammation and granulomatous reactions. These findings demonstrate the clinical relevance of C. contorta and emphasize the need for strengthened surveillance and control programs to reduce infection pressure and prevent potential spillover to wild populations.