Histological and morphological characteristics of Onchocerca flexuosa in red deer

Abstract

In the province of León, Spain, the presence of Onchocerca flexuosa was investigated in 110 red deer (Cervus elaphus). They were shot by the technical staff of the Regional Hunting Reserve of Riaño, in selective hunting and their hides were collected. Nodules containing O. flexuosa were located in the dorsal region and flanks of the animals. They were collected and measured and some nodules were fixed in 10% neutral buffered formalin, embedded in paraffin, sectioned and stained with heamatoxylin and eosin. In other nodules, several female and male nematodes were removed intact and preserved in 80% ethanol. Subsequently they were cleared in lactofhenol and identified. Morphologically, the adults are filiform, with a thin cuticle. The following results were found: total length (mean ± SD) was 62.33 ± 6.59 mm (range: 52-71) and the width of the anterior end 0.18 ± 0.03 mm (0.14-0.20). The total length of the esophagus was 7.88 ± 0.20 mm (7.66-8.04) and its muscular part 0.70 ± 0.14 mm (0.55- 0.96). Males have a distinctive corkscrew-shaped end, with caudal alae, post-cloacal caudal papillae and two unequal spicules, the left one 0.63 ± 0.08 mm (0.54-0.77) with narrow lateral alae and the right one 0.20 ± 0.02 mm (0.16-0.23), which is distinguished from that of other species by a prominently recurved spicule hook. Histologically, the worms were found in several compartments separated by an infiltrated fibrous tissue. They were inhabited by several females and males, surrounded by a fibrous capsule. There were inflammatory infiltrates of eosinophils, lymphocytes, plasma cells and macrophages with strong fibroplasia giving rise to a granulation tissue around them all. Amorphous eosinophilic material (Splendore-Hoeppli reaction) was observed on the surface of some worms. Degenerate worms are surrounded by a granulomatous reaction. In older nodules degeneration of the tissues and calcification of the worms takes place.