How do turtles get herpes? Nobody knows for sure, but this particular strain of herpesvirus creates cauliflower-like tumors that may end up costing the turtle’s life.
Fibropapillomatosis (FP) is a disease that has been observed across all species of sea turtles, but it has become especially widespread among green sea turtles (Chelonia mydas) at an alarming rate. The benign tumors that are characteristic of FP develop on soft tissues, shells, and even eyes of infected turtles, and when left untreated, they can grow to immense sizes, impairing the animal’s movements and vitals such as breathing and swallowing. So while these tumors are by no means directly lethal, they invite hordes of secondary infections and pathogens that may ultimately result in fatality. A study published in the journal, Disease of Aquatic Organisms, by Elliott R. Jacobson et al., of the College of Veterinary Medicine, University of Florida, found that the likely agent of this disease is a herpesvirus, and subsequent research has narrowed it down to the Chelonid herpesvirus 5 (ChHV5), which shares the same family as human genital herpes.
Green sea turtles are already endangered due to factors such as nesting habitat loss, pollution, egg harvesting, climate change, and boat strikes; the alarming prevalence of FP serves to only exacerbate the marginalization of the species. The number of cases of FP have experienced up to a 6,000% increase from the 1980s to the mid-1990s, with FP spreading all around the world for specifically green sea turtles. FP is so globally pervasive that the outbreak has been classified as “panzootic,” the animal equivalent of “pandemic.” Yet, whether warmer waters or pollution, it is still unclear what exactly has caused this virus to spiral out of control in just one or two decades.
Although there has been no conclusive evidence pointing to the exact factors that had catalyzed the unfortunate ubiquity of this disease, a study published in Aquatic Toxicology by Cinthia Carneiro da Silva of the Federal University of Rio Grande discovers a “significant and positive correlation” between concentration of heavy metals in blood and the severity of FP, as well as a significant and negative correlation between cholesterol concentrations and FP (2016). Additionally, Angélica María Sánchez-Sarmiento of the University of São Paulo discovered that many green sea turtles have been exposed to organochlorine compounds, which are known to have carcinogenic effects.
Sea turtle with FP tumors on its eyes and soft tissue, which may affect its locomotion and survival chances
Surprisingly, almost all of the infected turtles are juveniles, raising questions about why this is the case. Karina Jones of James Cook University, who published a comprehensive, up-to-date review of FP in The Veterinary Journal, offers possible explanations. Her most optimistic one is that current adults and hatchlings have never been exposed to the disease, so only one generation (the juveniles) has been infected. Another optimistic possibility is that once infected turtles recover from the disease, they will simply acquire immunity as adults. However, there is another devastating possibility: all of the affected juveniles will perish before they reach adulthood, leaving only the unaffected alive and dooming the species. Jones reported that FP “grows on their [the turtles’] eyes, they can’t see predators, they can’t catch food, so sometimes they slowly starve to death — it’s not a nice thing for the turtles to experience… Severely affected turtles are quite skinny and have other pathogens affecting them – that’s why they die” (2016).
On a more positive note, conservation groups such as The Turtle Hospital, located in the Florida Keys, make an active effort to save infected sea turtles. They perform surgeries that remove FP tumors, subsequently rehabilitate the turtles, and then release them back into the wild. In addition, they collaborate with state universities such as the University of Georgia College of Vet Medicine to study this virus and educate the public on sea turtle conservation. Through hard work and dedication, the Turtle Hospital has successfully treated and released over 1,500 sea turtles since they opened!
Eradicating such a devastating virus will take many more years of specialized research, but that shouldn’t dissuade anyone from trying to help. Just because there is no definitive cure yet doesn’t mean that the entirety of the green sea turtle population is doomed. If people learn about FP and actively participate in efforts to combat other factors affecting the sea turtle population such as pollution, egg harvesting, and boat strikes, green sea turtles as a species will surely find their way onto a road to recovery!
Jones, Karina, et al. “A review of fibropapillomatosis in Green turtles (Chelonia mydas).” The Veterinary Journal, vol. 212, 2016, pp. 48-57. http://www.sciencedirect.com/science/article/pii/S1090023315004529
Carneiro da Silva, Cinthia, et al. “Metal contamination as a possible etiology of fibropapillomatosis in juvenile female green sea turtles Chelonia mydas from the southern Atlantic Ocean.” Aquatic Toxicology, vol. 170, 2016, pp. 42-51. http://www.sciencedirect.com/science/article/pii/S0166445X15300904
Borrowman, Kelly, “Prevalence And Severity Of Fibropapillomatosis In Juvenile Green Turtles (chelonia Mydas) In Three Habitats On Florida’s Eas” (2008). Electronic Theses and Dissertations. Paper 3449. http://stars.library.ucf.edu/cgi/viewcontent.cgi?article=4449&context=etd
Monezi, Telma A. et al. “Chelonid herpesvirus 5 in secretions and tumor tissues from green turtles (Chelonia mydas) from Southeastern Brazil: A ten-year study.” Veterinary Microbiology, vol. 186, 2016, pp. 150-156. http://www.sciencedirect.com/science/article/pii/S0378113516300463
Sánchez-Sarmiento, Angélica María et al. “Organochlorine pesticides in green sea turtles (Chelonia mydas) with and without fibropapillomatosis caught at three feeding areas off Brazil.” Journal of the Marine Biological Association of the United Kingdom, 2016, pp. 1–9. http://dx.doi.org/10.1017/S002531541500226X
Herbst, Lawrence H. et al. “Experimental transmission of green turtle fibropapillomatosis using cell-free tumor extracts.” Diseases of Aquatic Organisms, vol. 22, 1995. http://www.int-res.com/articles/dao/22/d022p001.pdf
Jacobson, Elliott R. et al. “Herpesvirus in cutaneous fibropapillomas of the green turtle Chelonia mydas.” Diseases of Aquatic Organisms, vol. 12, 1991.
“The Turtle Hospital. Rescue, Rehab, Release.” The Turtle Hospital Rescue Rehab Release. 2014, http://www.turtlehospital.org/about-us/.