Euroturtle

There has been an inexplicable increase in the frequency of the appalling and disfiguring disease of fibropapillomatosis in sea turtles. New research now suggests that human-induced environmental changes are responsible.

History of the Disease

Fibropapillomatosis (FP) has a worldwide, circumtropical distribution and has been observed in all major oceans, reaching epidemic proportions in some habitats. The disease was first documented in the early 1920s in an adult Green turtle found near Key West, Florida. Since then a significant increase of cases has been reported. Even though Fibropapillomatosis is mainly found in sea turtles that live in tropical marine ecosystem, such as Green, Loggerhead, and Olive turtles, since the 1980s, the disease was found in all species of turtles worldwide. In well-documented areas, such as Hawaii, FP cases in Green turtles range from 20 to 60 % and account for the most significant cause of mortality. The health of most turtles that become infected with the disease steadily worsens, as their tumours increase in numbers and in size. Since FP prevails mainly in immature turtles, the loss of this age group to the disease may have demographic effects for the species in the longer term. While today Fibropapillomatosis is a growing threat to Green turtles worldwide, the disease may possibly have a severe impact on the long-term survival of other sea turtle species.

Symptoms and the state of research:

The disease is characterized by the presence of non-cancerous fibrous tumors on areas of soft skin, such as the neck, chin, eyes, corners of the mouth, flippers, and the base of the tail. Tumors may be pink, white, or black in color and vary in size from less than a centimeter to the size of a football, and may weigh as much as three pounds. In some cases, the tumors may become so large as to occlude vision and obstruct feeding. Besides visible manifestations, about 20-30% of turtles affected by FP have internal tumors, most commonly in the lungs, liver, kidneys and heart, and become more susceptible to secondary bacterial infections.

Scientists have yet been able to identify the cause of the FP disease in sea turtles. Because papilloma tumors are known to be spread by a herpes virus in animals and humans, the agent was suspected to be a potential cause for FP in turtles. However, even though the herpes-like virus has been found in turtles infected with FP, scientists have not been able to determine if the virus was a primary or a secondary infection, caused by the already present disease. Other causes proposed for the disease include pollutants, blood flukes, marine toxins, ultraviolet light, and numerous viruses. Some studies suggest that environmental contaminants may suppress the turtles’ immune system, making them more susceptible to the disease. In fact, several field studies have shown that cases of FP in turtles living in near-shore habitats that are affected by industrial and/or urban developments have a higher incidence. Field observations support that prevalence of the disease has been associated with heavily polluted coastal areas, human areas of high density, agricultural run-off, and/or biotoxin-producing algae. While the disease may be caused by a combination of factors discussed, improving habitat quality in areas where the occurrence of the FP disease is high may be the first step to reducing its incidence.

Implications for Humans:

The Fibropapillomatosis disease is not zoonotic, i.e. it may not be passed to humans. However, the presence of the disease may suggest an ecological imbalance and threats to the environment that may directly or indirectly affect the human population.

Eckert, K.L, Bjorndal, K. Abreu-Grobois, F. and Donnelly, M. (1999) Research and Management Techniques for the Conservation of Sea Turtles. IUCN/SSC Marine Turtle Specialist Group Publication No. 4,

Jones, A.G. (2004) Sea Turtles: Old Viruses and New Tricks. Current Biology, Volume 14, Issue 19.