Preliminary findings in a case of Onchocercosis in Italian wild red deer (Cervus elaphus).

Introduction: Onchocercosis is a vector-transmitted (simuliids) parasitic disease which can be caused by 28 species of Nematoda belonging to the Genus Onchocerca. It involves wild and domestic ungulates, humans (O. volvolus), and dogs (O. lupi). Red deer (Cervus elaphus) host numerous Onchocerca sp. and only few of them have been reported in European countries but never in Italy. The most important species described in European deer are O. flexuosa, O jakutensis or tubingensis and O. tarsicola. They have definite locations in the host and only two of them, O. flexuosa and O. jakutensis, live inside subcutaneous nodules. Material and methods: During the early hunting season 2007-08, between September and November, in the Pistoia Province (Tuscany, 44°00'N, 11°00'E), subcutaneous nodules were observed on both thighs of red deer. During necropsy of four subjects, four nodules were collected for histopathological study, fixed in 4% buffered formalin, paraffin-wax embedded, sectioned at 4 micron and routinely stained with haematoxilin and eosin. Ten were sampled for microbiological and parasitological observations. Results: The nodules were 8 or more per thigh, about 1.5-3.5 cm in diameter and the cut section showed a yellowish mucinous material with some long, thin, friable firmly intricated, white filamentous worms. No bacteria were isolated from the nodules. Histological examination evidenced cystic structures surrounded by a fibrous capsule, containing nematodes. Many eosinophilic and few neutrophilic granulocytes were present among the parasites, and macrophages infiltrated the fibrous capsule. In the uterus of nematodes some larval structures were evident. In the nodules females and males were irregularly interwoven. Females were longer than 19 cm. The cuticle showed superficial transversal relieves (range 44 to 57 micron) among which, in a deeper layer, 3-4 stripes were present. The tail (about 161 micron in length and 78 in thickness) showed a clublike shape with two phasmides. Males had many cuticular stripes and ended coiled up and two spiculae were present. These structures were measured in one male: the longest spicula was 310 micron and the shortest 110 micron. Moreover, the length of five microfilariae was within a range of 250-270 micron. Discussion: In red deer, back and flank nodules can be caused only by two Onchocerca species, namely O. flexuosa and jakutensis. A third, O. tarsicola presents some similarities regarding cuticular aspects and shape of the tail of females (clublike) and males (coiled up) (Bain and Schulz-Key, 1974), but differ for type of lesions (O. tarsicola does not cause nodules) and location (this species is described free in the subcutaneous tibio-tarsal and radio-carpal articular tissue). Besides, the length of the spiculae of the male and the length of the microfilariae would exclude O. tarsicola. In fact the spiculae of O. tarsicola are 200 and 130 micron long, and microfilariae are 400 to 430 micron. In the nodules described in the present study the measurements were respectively 310 and 110 micron for the longest and shortest spiculae, and 250-270 micron for the microfilariae, the same reported in the literature for O. flexuosa and jakutensis (Bain and Schulz-Key, 1974). In the progress of our study, which is the first report of deer Onchocercosis in Italy, we intend to carry on a genetic study for a molecular diagnosis and a taxonomic location of this species.