Fibropapillomatosis: Global Disease Plaguing
Endangered Sea Turtles

by Christine Banks

“Wildlife Trust is taking a proactive approach in assessing the health of not only sea turtles but other species that serve as sentinels of the health of ecosystems. These tumored turtles are telling us that something is happening to the oceans and we need to pay attention to the consequences of our actions.”
Dr. Alonso Aguirre, Vice President, Conservation Medicine at Wildlife Trust

For Dr. Alonso Aguirre and his research team, a morning cruise in Kaneohe Bay isn’t for whale watching or soaking up rays along the coast of Oahu; they are on a mission: to search near-shore areas for sea turtles. When a turtle is spotted, a team member eases into the water, quickly grabs the turtle, and lifts it into the boat for evaluation. These juvenile green turtles are still small enough to be easily lifted by one person. Once the team examines the turtle, they often find what they are searching for: fibropapillomas.

Fibropapillomatosis (FP) is a complex and disfiguring disease plaguing sea turtles worldwide that causes tumors on the skin. These tumors can inhibit a turtle’s ability to swim, eat or see, depending upon where the tumors grow; the tumors can also grow internally, causing other health problems. Incidence of FP has increased significantly over the past 20 years, causing concern in the global conservation community.

FP was first recorded in the 1930s in green turtles near Key West, FL, but it wasn’t widespread. Unfortunately, the distribution of the disease has increased steadily since 1985, and it is now found in all seven species of sea turtles. In some areas of the world, it has received epidemic status. This is especially worrisome, as all species of sea turtles are endangered on a global scale, and continued threats to their health will seriously damage the remaining populations.

“We have been monitoring FP in several parts of the world, including Hawaii, Australia, Mexico, Venezuela, Brazil, Chile, Argentina and Gabon,” explains Aguirre, vice president for Conservation Medicine at Wildlife Trust and a renowned expert on fibropapillomatosis. “We’ve observed that green turtles are the species most affected by FP, and we sometimes see that nine out of ten turtles in an area have tumors, which is extremely discouraging from a conservation viewpoint.”

The tumors, called fibropapillomas, tend to appear on the skin, flippers, near the eyes and on the shell. They can also develop internally on organs such as the heart and lungs. Some of the tumors grow quite large, over 12” in diameter. When tumors grow so large, they can interfere with the turtles’ ability to survive and can ultimately cause fatalities due to starvation, predation due to decreased mobility or internal organ failure. In addition, some turtles’ internal tumors are diagnosed as cancerous with a low-grade malignancy, complicating the attempts to understand the causes of these tumors.

The exact cause of FP is still unknown, but several factors are suspect, including decreased immune response and exposure to a virus. Studies have linked a high prevalence of tumors to environmentally disturbed ocean habitats. These areas are usually heavily polluted coasts, with high human population density, agricultural runoff and even red tide events. One theory is that sea turtles may contract FP during their juvenile years, which are spent in near-shore benthic (at the bottom) habitats. Long-term studies have shown that turtles arriving at such feeding areas are free of FP. After spending time in these ecosystems, FP establishes in the external tissues and spreads to the internal tissues in 25-30% of those turtles.

It is difficult to identify the causes and origin of a disease, and laboratory work on FP has been ongoing for years. Two herpesviruses, a papillomavirus and a retrovirus have been associated with tumors using electron microscopy and molecular techniques; however, no single responsible virus has been found.

“Since I began working with this disease fifteen years ago,” Aguirre says, “a lack of funding has compromised efforts to tackle the true cause of this disease. Much of the work that has been done is a result of scientists donating their time and money to this research to help sea turtles. National Marine Fisheries Service is one of the few institutions funding this type of cutting edge research.”

Attempts have been made to treat the tumors through different types of surgery, such as laser surgery, cryosurgery (using liquid nitrogen to freeze them off) and the injection of Dermex (a zinc-hydroxyquinoline based mix) that has been used to treat warts in humans. Dermex seems promising, but is quite expensive and is not a practical treatment for wild populations.

Surgical treatment has been used on turtles brought into labs/clinics for rehabilitation, but they have been released back into the wild with no follow up studies on the released animals. Until the cause of FP is found and identified, it is very difficult to develop effective treatments.

A ray of hope has been observed in recent years: after a point, some tumors appear to regress in a few turtles. If a sea turtle can survive long enough with the tumors, the tumors begin to shrink. More research is being conducted to confirm this and determine why the regression takes place.

Of special note: turtles are migratory and have recently been found to have extremely large ranges, making it difficult to determine where they may have picked up FP.  For example, juvenile loggerhead turtles (Caretta caretta) that forage along the coasts of the Baja California peninsula will eventually nest in Japan. There is also a population of loggerheads being studied in Chile that appears to be nesting in Australia. The home range and migratory patterns of this species represent one of the widest known for a marine organism. This highlights the importance of international collaborations in working with migratory species and their diseases.

Wildlife Trust is monitoring the health and FP status of sea turtles in many parts of the world. Our Conservation Medicine program has a large initiative in Mexico to monitor sentinel species, including sea turtles, as indicators of environmental health.  Increased tumor prevalence, along with other indicators, can signal a decrease in environmental quality.  On the Baja Peninsula there are many current and proposed ecotourism and coastal development initiatives, such as the large-scale Escalera Nautica (Nautical Ladder) project that proposed 24 marinas with accompanying hotels and golf courses, which would continue to pressure the relatively pristine ecosystems that many marine species inhabit.  The Baja sea turtle population is currently being sampled every month in our health assessment project; it is important to have a monitoring program in place to track the changes in health that occur as a result of development and the consequent increases in boat traffic, run-off, pollution and other effects.

Juvenile sea turtle health is also monitored for early evidence of FP, including the Peconic Bay on Long Island, New York, where many juvenile turtles, including the loggerhead turtle, Kemp's ridley turtle, green turtle and leatherback turtle,migrate each year from July to November to feed on algae, crabs and mollusks.

The epidemiology of FP can also serve as an effective tool to monitor ecosystem health in local warm-water, near-shore marine habitats.  Dr. Aguirre notes, “Wildlife Trust is taking a proactive approach in assessing the health of not only sea turtles but other species that serve as sentinels of the health of ecosystems. These tumored turtles are telling us that something is happening to the oceans and we need to pay attention to the consequences of our actions.”