Monogenean parasites frequently infect the body surfaces of wild elasmobranchs. When sharks are brought into captivity, the infections can become intensified leading to disease and death, as has been reported from a number of public aquaria. Many of the monogeneans that infect requiem sharks, Carcharhinidae, (the family to which the lemon shark Negaprion brevirostris belongs) are microbothriids, and belong to the genera Dermopthirius, and Dermopthiriodes. These parasites attach to their hosts by a haptor which secretes cement, for adhesion to the skin.

In this report we describe the appearance and treatment of skin lesions in four captive lemon sharks from Sea World in Florida. Since it is known that there may be differences in pathogenicity and susceptibility to treatments among monogeneans, we identified the parasite to species level.

Between 1993 and 1995, all four lemon sharks developed intermittent clinical signs of microbothriid infections, characterized by a combination of some or all of the following signs: rubbing on the rocks and walls of the aquarium, irregular grey patches on the skin, a dark band of hemorrhagic skin around the mouth, and skin lesions around the eyes and on the top the head. Scraping of the skin lesions showed that numerous platyhelminth parasites were present. They were characterized by an elongate tongue-shaped body, and a narrow elongate posterior end, terminating in a inconspicuous haptor. The parasites swam actively, with a rippling motion, and frequently the haptor stuck to the glass slide. Their identify was confirmed as Neodermopthirius harkemai (Microbothriidae, Monogenea). A variety of treatments were administered with varying degrees of success, the best was copper sulfate (0.25 ppm for 85 days). At the end of this treatment period, parasites were not detected in the lesions, and the skin of the sharks was normal. Although this treatment was the most effective, the disease subsequently reoccurred.

We believe that this is the first report of disease caused by a species of Neodermopthirius. The response to treatments by this parasite is very different from that reported for other monogeneans from requiem sharks, indicating that accurate identification of the parasite may help to predict the best course of treatments.

References

1.  Cheung, P.J. 1993. Parasitic diseases of elasmobranchs. In Stoskopf, M.K. Fish Medicine. W.B. Saunders, Philadelphia. pp. 782-807.

2.  Cone, D.K. 1995. Monongenea (Phylum Platyhelminthes) In Woo, P.T.K. (ed.) Fish Diseases and Disorders. Volume 1. Protozoan and Metazoan Infections. CAB International, Wallingford, England. pp.. 289-327.