Wednesday, June 12, 2013
Turtle Tumors: Fibropapillomatosis and Green Sea Turtles
In the last few decades, a crippling infection has been appearing in increasing amounts on sea turtles around the world called Fibropapillomatosis (FP). This disease causes external and sometimes internal tumor growth on the face, flippers, and skin of sea turtles (see photo) and is afflicting the endangered Green Sea Turtle in much higher numbers than any other species of marine turtle. Although these tumors are usually not cancerous, they can be large in size and in number and can greatly impact a turtle’s movements, eyesight, and physical ability, which is alarming since all species of Marine Turtles are considered threatened or endangered according to the Endangered Species List. The cause of this disease has yet to be determined, but research has shown that it is most likely a result of a turtle herpes virus, although the data is not yet clear how the disease is spread or why it is expressed. However, studies have suggested that a contributing factor to the rising rates of FP could likely be environmental pollution and climate change.
According to research by the Florida Sea Turtle Stranding and Salvage Network, “22.2 percent of dead or debilitated (i.e. stranded) green turtles (sample size=6027) found in Florida between 1980-2005 had FP tumors. FP prevalence is low among strandings of Kemp's ridleys (Lepidochelys kempii), and loggerheads (Caretta caretta) in comparison to the rate of FP in green turtles” (Florida Fishand Wildlife Conservation Commission). The reasons for this disproportionate species occurrence is unknown, but the implications are significant as the Green Sea Turtle is listed as endangered by the Endangered Species Act and research has shown a 48-50% decline in the amount of mature nesting females in the past 150 years (NOAA Fisheries). One difficulty in studying Green Sea Turtles and Fibropapillomatosis is the fact that as juveniles, turtles travel and live in the open ocean for many years and current tracking technology is unable to monitor their activity for this portion of their lives. One study suggested that these juvenile turtles only express FP after returning from offshore into coastal areas, which supports the idea that the disease may be passed through skin lesions (Patricio et al). Research has also suggested that the disease may be waterborne or from a marine leech that carries the DNA associated with the herpes virus. (Greenblatt et al).
Many studies have proposed that the increase in FP prevalence may be due to climate change and environmental changes in the turtles’ habitats. One study that researched the turtle associated herpes virus thought to cause FP found that the virus has been present for 3 million years, and since the disease was shown to be more common in polluted habitats, the environment could be a major factor in the infection (Greenblatt et al). Another study in in the Hawaiian Islands showed that there are more diseased turtles in areas with a high amount of nitrogen runoff from urbanization and agriculture. The researchers suggested that the arginine produced from nitrogen rich seaweed triggers the growth of tumors from the dormant herpes virus in turtles (National Geographic). More research found that the virus is present in a large percent of non-diseased turtles, and that both infected and healthy turtles may release this virus into the environment. They also discovered that the virus was present not only in epidermis (outer skin) cells, but in dermis (inner skin) cells as well, implying that this disease is more than just a skin infection (Page-Karijian et al). However, it is still not certain that the virus is the cause of Fibropapillomavirus, so more research should be conducted to determine the true origin of this debilitating infection.
Since the cause of this disease is currently unknown, so are the treatment and prevention methods. According to The Turtle Hospital in Marathon Florida, a charitable corporation that treats injured and diseased turtles and returns them to the wild, almost all of the marine hospitals in Florida cannot accept turtles with FP because of its infectious nature. The protocol for treating the infected turtles involves first checking for internal tumors -which if present call for euthanasia of the turtle- but when absent, the external tumors are removed with a CO2 laser. The turtle is kept for one year and if no tumors grow back, they are released into the wild. However, many times the tumors regrow and this process is repeated until they do not, which could take many years. (The Turtle Hospital).
So why should we care? The disease is not spreading to humans or affecting us directly. However, it could very well affect us indirectly in the future if it goes unchecked. Fibropapillomavirus is an incapacitating and mysterious infection that is contributing to the already steep decline of marine turtles around the world. Along with certain countries harvesting Green Turtle eggs and adults, and accidental capture in fishing nets, this disease is a significant threat to these endangered species and more efforts in research and conservation should be pursued to protect them. Sea Turtles have been on Earth for over a hundred million years and they are one of the only species that eats sea grass, so their presence is important in maintaining sea grass beds and the biodiversity the beds provide. The eggs they lay also contribute to the nutrients of the beach sands, which are then able to grow vegetation and provide a more stable and biologically diverse ecosystem on the shore as well (Sea Turtle Conservancy). Sea turtles play a vital role in maintaining marine and shore ecosystems, and if their declining numbers and this disease is not addressed, it would mean a loss of biodiversity and a possible imbalance in marine ecosystems, which would affect all species on Earth, including us.
Although the research is not entirely conclusive on the cause of FP, there is evidence that a contributor is marine pollution and other environmental changes caused by humans. Along with further research on the disease, other efforts are being implemented to protect sea turtles from negative human activity. One way to reduce the amount of turtles killed in fishing nets is the use of safe netting gear called a TED or Turtle Excluder Device, which allows turtles and other large creatures to escape through the bottom while smaller fish and shrimp are caught (NOAAFisheries). Since FP can debilitate a turtle’s movement and ability to escape fishing nets, this device is important in conserving the endangered species. Other legislative efforts like boat speed limits in turtle rich areas and government funded conservation programs are also helpful and should be encouraged and enforced if we want to protect these ancient reptiles that contribute so much to the biodiversity of our oceans and world. There is obvious evidence that humans are largely responsible for marine turtles’ shrinking numbers and possibly this crippling disease, so it is our responsibility to do our best to educate others, protect, and research these ancient reptiles for our future and for theirs.
TED: Turtle Excluder Device
"Green Turtle (Chelonia Mydas) - Office of Protected Resources – NOAA Fisheries." Green Turtle (Chelonia Mydas) - Office of Protected Resources - NOAA Fisheries. NOAA Fisheries, 5 Dec. 2012. Web. 29 May 2013.
Greenblatt, R. J. et al. "Genomic Variation of the Fibropapilloma-Associated Marine Turtle Herpesvirus across Seven Geographic Areas and Three Host Species." Journal of Virology 79.2 (2004): 1125-132. Journal of Virology. American Society for Microbiology, Jan. 2005. Web. 28 May 2013.
Kessler, Rebecca. "Sea Turtle Herpes Tumors Linked to Sewage?" National Geographic. National Geographic Society, 09 Nov. 2010. Web. 28 May 2013.
Page-Karjian et al. "Presence of Chelonid Fibropapilloma-associated Herpesvirus in Tumored and Non-tumored Green Turtles, as Detected by Polymerase Chain Reaction, in Endemic and Non-endemic Aggregations, Puerto Rico." SpringerPlus 1.35 (2012): n. pag. 17 Oct. 2012. Web. 28 May 2013.
Patricio, A. R. et al. "Global Phylogeography and Evolution of Chelonid Fibropapilloma-associated Herpesvirus." Journal of General Virology 93.5 (2012): 1035-045. Journal of General Virology. Society for General Microbiology, 18 Jan. 2012. Web. 28 May 2013.
"The Turtle Hospital." The Turtle Hospital. N.p., n.d. Web. 29 May 2013.
"Why Care About Sea Turtles?" Sea Turtle Conservancy. Sea Turtle Conservancy, 2011. Web. 29 May 2013.