Death of a neonated porpoise at Marineland of Florida was attributed to infestation with lung worms, Halocercus sp. Necropsy of two other adult animals which died spontaneously also revealed heavy pulmonary nematodiasis. Verminous pneumonia was associated with bacterial infection, and Pasteurella multocida was cultured from one of the adults. Histologic examination showed adult parasites within various segments of the bronchial tree. A mucopurulent exudate surrounded the parasites, and the lamina propria of the affected bronchus was infiltrated with plasma cells and eosinophils. Complete plugging of bronchioles with parasites and necrotic debris was accompanied by atelectasis, pulmonary edema, and suppurative inflammation.

Necropsy of adult animals has shown chronic centrolobular congestion of the liver; however, gross and microscopic examination has failed to reveal any cardiac involvement. The relationship of the liver lesions or the verminous pneumonia to the disease problem at Marineland is uncertain at this time. Since past necropsy records do not indicate previous lung worm infestations, it is important to determine whether confinement within an aquarium might predispose to this disease.

Previous studies of pulmonary parasitism in other animal species indicate that lung worms are seldom responsible for death. Parasites of the genera, Halocercus give birth to live larva which pass up the trachea, and are expelled via the blowhole. The life cycle is probably direct because copper treatment of the aquarium water kills most invertebrates which could serve as intermediate hosts. Infestation in neonatal animals raises the possibility of transplacental or intra-local transmission to the young. In this regard, larva could not be isolated from the mother's milk; however, colostrum was not examined. A knowledge of the natural incidence of this disease within newly captured animals would be beneficial in determining the significance of pulmonary parasitism in porpoises maintained in aquariums.