Pathological lesions in the lungs of red deer Cervus elaphus (L.) induced by a newly-described Dictyocaulus cervi (Nematoda: Trichostrongyloidea).

The large lungworms of the genus Dictyocaulus are causative agents of parasitic bronchitis in various ungulate hosts, including red deer. Recently, the red deer-derived lungworm D. cervi was described and separated from D. eckerti. Little is known of the transmission patterns, epidemiology, geographical distribution and pathogenicity of D. cervi. Histological examinations were performed on 22 formalin-fixed lung tissue samples of hunted red deer. Exclusively, D. cervi adults were derived from 15 red deer and confirmed molecularly (GenBank accession: MH183394). Dictyocaulus cervi infection was associated with various degrees of lung pathology, including interstitial pneumonia, bronchitis and bronchiolitis with an influx of eosinophils, lymphocytes, plasma cells and macrophages; massive hyperplasia of lymphoid follicles within bronchiolar tissue, and hyperplasia of the bronchial and bronchiolar epithelium. Furthermore, emphysema, atelectasis and lung tissue congestion were noted. Interestingly, interstitial and subpleural fibrosis was seen in adult Dictyocaulus-negative samples, suggesting either a prepatent phase of Dictyocaulus infection or infection/coinfection with protostrongylid nematodes.