Elaeophorosis in red deer caused by Elaeophora elaphi: lesions of natural disease.

This is the first study of the lesions produced by Elaeophora elaphi, a filarial worm first reported in 1986. Only the morphologic characteristics of this species have been described previously. Samples for the study were taken from 74 red deer (Cervus elaphus), 1-10 years old, slaughtered in central Spain. Grossly, filariae were observed in the transverse, left, or right branches of the portal vein of 18 animals. In addition to filariae, whitish thrombi were found in the right and left branches of the portal vein in nine animals. Thrombi of similar characteristics were also observed in 12 deer in which no adult filariae were found. Microscopic changes were observed only in the right and left branches of the portal vein and consisted of thickening of the intima with surface formation of villi. Stroma of villi contained a moderate to intense infiltrate composed mainly of eosinophils and mononuclear cells. The tunica media of affected vessels was uniformly hypertrophic and in some cases presented a moderate inflammatory infiltrate similar to that observed in the stroma of villi. Thrombi consisted of a central area containing calcified filariae or cuticle debris, surrounded by giant cells and numerous lymphoid cells forming clearly defined nodules resembling lymphoid follicles. Thrombi were externally surrounded by a strip of connective tissue and beyond by endothelial cells that were occasionally continuous with the tunica intima. Other lesions probably associated with the infestation were multifocal granulomas in the periportal areas, lymphoid tissue formations in the hepatic parenchyma, and an interstitial nephritis.