Manatee research leads to new questions

Over the past three years, an interdisciplinary team of veterinarians and physicians studying an emergent papillomavirus in manatees have sequenced the genome of the virus, developed an experimental vaccine, and created a new diagnostic test. Some of their discoveries have led to new questions about the origins of the disease, and the environmental factors causing it to emerge.

The emergence of a papillomavirus in a population of manatees at the Homosassa Springs State Wildlife Park has generated concern from conservationists who fear it could compromise the future of this already endangered species. It has also sparked the interest of researchers studying papillomaviruses in humans and other animals. The wartlike growths seen on infected manatees are similar in some aspects to the tumors that lead to cervical cancer in women. It is hoped that by understanding the pathogenesis of papillomaviruses in manatees, researchers can help manatees and better understand papillomaviruses in other species.

For that reason, physicians Alfred Bennett Jenson, a papillomavirus expert, and Partha Basu, the head of gynecologic oncology at the National Cancer Institute of India, joined a research team that already included Dr. Gregory Bossart, a veterinarian, comparative pathologist, and the director of marine mammal research and conservation at Harbor Branch Oceanographic Institution in Fort Pierce, Fla.; and Dr. Mark Lowe, the staff veterinarian at Homosassa Springs State Wildlife Park, Homosassa, Fla. Their research was originally highlighted in the Nov. 1, 2002 issue of JAVMA News, and is available online. 

The biggest surprise for researchers has been discovering that the virus is not a new variant; in fact, it is primitive.

"I would have thought, as an emerging disease, it would have come off the top of the (phylogenetic) tree," Dr. Bossart said. "It brings up a whole new list of questions."

The discovery suggests that the disease has long been latent, but only recently emerged. Climatic change caused by human activities is likely a factor, because manatees are exquisitely sensitive to temperature changes, Dr. Bossart said.

"(Global warming) is likely selecting for new pathogens," he said.

The development of an ELISA test for detecting antibodies to the papillomavirus has allowed the team to begin testing free-ranging manatees. So far, none of the free-ranging manatees has tested positive, Dr. Bossart said.

To prevent the spread of the disease, Dr. Bossart and his colleagues will be moving some of the infected manatees from the Homosassa Springs State Wildlife Park to a new marine mammal teaching hospital being built at Harbor Branch. A vaccine trial will begin later this summer at Homosassa Springs and Harbor Branch. A postdoctorate fellowship position dedicated to studying the manatee papillomavirus has recently been created at Harbor Branch, and the fellow is expected to start work later this year.