Melba C. Caldwell1; David K. Caldwell1; Stephen G. Zam2
This is a preliminary report on the appearance of the nematode lung worm, Halocercus sp., in Atlantic bottlenose dolphins, Tursiops truncatus, captured in northeast Florida and maintained at Marineland of Florida.
Severe health problems that have arisen at Marineland since this finding justify the making of such a preliminary report, particularly in view of the fact that Andersen (1966) attributed 8 out of 12 deaths in captive harbor porpoises to parasitic bronchitis. We must emphasize that the finding of the lung worms and the appearance of the health problem are very likely coincidental, however. As pointed out elsewhere in this volume (abstract by Woodard), lung worms seldom cause death in other animals, whereas Marineland of Florida has had many deaths from an undetermined cause during the first quarter of 1968. The true cause of this totally new problem in an establishment maintaining dolphins of this species since 1938 has not been determined, but to date appears to be a severe liver damage related to some toxic substance of an unknown type or origin.
Lung worms of the genus Halocercus are reported from cetaceans in Europe and Asia (Baylis and Daubney, 1925; Wu, 1929; Yamaguti, 1958) and in the Gulf of Mexico, both in the northeast Gulf (J. B. Siebenaler, Florida's Gulfarium, Ft. Walton Beach, pers. comm.) and in Texas (T. Whitman, Sea-Arama of Texas, Galveston, pers. comm.).
Our first contact with Halocercus came on 21 July 1967 when we did a postmortem examination of a 2 1/2--month-old male Tursiops truncatus and found its air passages virtually clogged with the parasites. The infant had been conceived in the wild, and was born at Marineland one month after the capture of his mother in the vicinity of St. Augustine. The infant had never developed normally, the posterior region particularly was poorly developed and his overall size small for his age. At birth he had appeared perfectly normal in all respects and his behavior was good.
Nothing has been published concerning the life cycle of this parasite, and inasmuch as the infant had never taken food other than its mother's milk and had been born and reared in copper-treated water (which should have destroyed any available invertebrate intermediate hosts for the parasite) containing no live fish, the mother was immediately suspected of being the carrier--passing the parasite on either through the fetal blood in utero or the milk. She was isolated immediately.
Fortunately at that time we had a group from the University of Florida School of Medicine working at Marineland on an unrelated project. They brought in others, among them John C. Woodard (see separate abstract in this volume) and one of us (Zam) who had experience with parasites and who were more qualified to examine the problem than the Marineland staff. The mother was examined for evidence of parasites or eggs in blowhole swabs, blood, milk and feces. All such tests were negative, but the animal was kept in isolation and watched. As of the summer of 1968, she has shown no evidence of sickness; in fact she apparently is one of the healthiest animals at Marineland.
After this first lung worm case, which apparently was the primary cause of death in the infant, a number of autopsies of Tursiops truncatus of various ages and of both sexes have been performed at Marineland, some on captive animals dying from the unknown problem and others captured and sacrificed to determine more of the natural biology for establishing norms. Either active lung worms or evidence of their past presence in the form of calcified and encysted worms were found in each case. Most of the animals that died after a time in captivity had been on antibiotics for other reasons, but a low grade pneumonia was found in association with the active parasites in most cases.
In the recent health situation at Marineland, the first indications of illness in the animals were a loss of appetite and lethargy. The blood picture was an initial elevated white count which often reversed itself into a severe neutropenia in terminal cases. Eosinophil counts in wild-caught and apparently-healthy cetacea are inexplicably much higher than the human norms which cetacean blood usually follows (Slijper, 1962: 174; Ridgway, Simpson and Patton, this volume). Our findings in wild-caught and healthy captive animals from both the Atlantic and Gulf coasts of Florida confirm this. The eosinophils decreased in our sick animals and disappeared from the peripheral blood in terminal cases.
Aside from the lung worms, the one real common denominator in the extremely puzzling picture has been severe liver damage which probably has been the ultimate cause of death in all but one case. The severity of the liver damage is indicated in the SGPT values (as high as 350 Karmen units) in several animals. These high readings dropped just prior to death apparently when the liver essentially stopped functioning completely.
Lung worms were possibly the precipitating cause of death in one animal in addition to the infant noted above. This was a 21-year-old female, born at Marineland. She had been in poor physical condition for over a year, and the parasites had gained a strong foothold.
Indications are that the parasites do not cause death per se except in infants or weakened adults approaching old age, but they may act as carriers for viruses or possibly secrete toxins which may precipitate or help to precipitate other medical problems.
Blowhole swabs made from the 21-year-old female, both five days and one day prior to death, showed eggs and live lung worm larvae. Material washed from these swabs was put in about 5 cc of seawater which was unaerated and kept at room temperature. Live larvae were still present in the tube after four days, but 12 days following their recovery from the animal all were dead. During the autopsy of this adult female Tursiops, swabs were made at several sites along the respiratory tract. These showed the presence of lung worm eggs and live larvae at all sites including the blowhole and nasal sac system of the head. The number of eggs and larvae increased materially at the posterior end of the larynx, and swabs taken from the trachea after the first bifurcation contained great numbers of eggs and both motile and non-motile larvae.
The lungs of both the infant and the old female contained huge numbers of eggs, larvae and gravid adult worms. It appears from this that no intermediate host is necessary and that the larvae may be transmitted from blowhole to blowhole, either directly by inhalation of infected spray or taken in alive from infected water. The behavior of bottlenose dolphins, especially mothers and young or family groups including all ages is such that their normal close proximity to one another would make either form of infectious transfer easily possible and even likely. Having made the first discovery of these worms in an obvious case like the infant, especially careful examination of other dolphin lungs since has led us to the conclusion that lung worms are more the rule than the exception in Tursiops, and may reach 100% as in Phocaena (Andersen, 1966).Most animals seem to be able to keep them under control, however, to the point where at times one would easily miss them in an autopsy unless special care was taken to look for evidences of them.
Ray (1961:52) reported parasitic roundworms associated with pneumonia in the lungs of the pilot whale (Globicephala melaena), the beluga (Delphinapterus leucas) and the harbor porpoise (Phocoena phocoena) .
We know of no recognized cure for lung worms, although diethy1carbamazine is administered orally or by injection to incoming cetaceans in Europe and given prophylactically to dogs in northeastern Florida.
Andersen, Soren 1966. The physiological range of the formed elements in the peripheral blood of the harbor porpoise, Phocaena phocaena(L) in captivity. Nord. Vet.-Med. 18:51-65.
Baylis, H. A., and R. Daubney 1925. A revision of the lung worms of Cetacea. Parasitology, 17:201-216.
Ray, Carleton 1961. A question in whale behavior. Nat. Hist., 70(6): 46-53.
Slijper, E. J. 1962. Whales. London: Hutchinson, 475 p.
Wu, Hsien Wen 1929. On Halocercus,pingi n. sp., a lung worm from the porpoise, Neomeris phocoenoides. J. Parasitology, 15:276-279.
Yamaguti, G. 1958. Systema helminthum. 3:516-522, pls. 78-84. Interscience.