[Catalyst 2017]

GREEN SEA
TURTLES
A SHELL OF WHAT
THEY ONCE WERE
KIRA CHEN
Sea turtles appear in many cultures and
myths, and are often beloved symbols of
longevity and wisdom. However, in spite of
the cultural respect shown towards them,
green sea turtles have gradually become
endangered due to factors such as nesting
habitat loss, pollution, egg harvesting, climate
change, and boat strikes. Now, there’s a
new, even more dangerous threat on the
block: herpes. And no, it’s not the herpes
you’re thinking of - this kind, known as
fibropapillomatosis (FP), is much, much worse.
FP has been observed across all species of sea
turtles for years, but it has recently become
especially widespread among green sea turtles
(Chelonia mydas). The alarming incidence of
FP is exacerbating the decline of this already
vulnerable population. Among green sea
turtles, the number of cases of FP increased
6000% from the 1980s to the mid-1990s, with
FP becoming so globally pervasive that the
outbreak has been classified as “panzootic,”
the animal equivalent of “pandemic.” Now,
you might think, “That sounds bad, but
why are these turtles dying?” In humans,
herpes is unpleasant, but it is seldom lifethreatening.
Unfortunately, in green sea
turtles, the outlook isn’t nearly as optimistic.
FP causes the development of tumors on the
soft tissues, the shells, and even the eyes of
infected turtles. When these growths are left
untreated, they can grow to immense sizes,
impairing the animal’s vital activities, such
as breathing and swallowing. So, while the
tumors aren’t directly lethal, they invite hordes
of secondary infections and pathogens that
ultimately result in death.
To make matters worse, treatment for FP
is still in development. A landmark study
identified the specific pathogen responsible
for FP as Chelonid herpesvirus 5 (ChHV5), a
close relative of human genital herpes. 1 This
discovery was the first step to a cure, but it
raised an important question - how had this
variant of herpesvirus become so prevalent?
Until recently, the answer to that question was
elusive.
Fortunately, several recent discoveries
offered new explanations for FP’s rise.
One study reported a significant positive
correlation between serum concentrations
of heavy metals and the severity of FP, as
well as a significant negative correlation
between serum cholesterol concentrations
and FP. 2 In a related find, a team at the
University of São Paulo discovered that
many green sea turtles have been exposed
to organochlorine compounds, which are
known to have carcinogenic effects. 3 Further
research could potentially determine a
direct causal relationship between the
development of FP and exposure to heavy
metals or organochlorine compounds. If such
a relationship were found, projects that strive
to decrease the prevalence of said compounds
in the turtles’ habitats could prove effective in
mitigating the spread of FP.
So what’s the prognosis for the green sea
turtle? Unfortunately, even knowing what we
now know, it may not be good. A study by
Jones et al. found almost all of the infected
turtles are juveniles, potentially creating a big
problem for the population. 4 Jones believes
the most optimistic explanation for this
trend 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. In a heartbreaking aside, 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.”
Eradicating such a devastating disease will no
doubt take many more years of specialized
research, and significant efforts are needed
immediately to rehabilitate the green sea
turtle population. Luckily, conservation groups
such as The Turtle Hospital, located in the
Florida Keys, are making an active effort
to save infected sea turtles. They perform
surgeries that remove FP tumors, rehabilitate
the turtles, and then release them back into
the wild. In addition, they collaborate with
universities to study the virus and educate the
public on sea turtle conservation. To date, the
Turtle Hospital has successfully treated and
released over 1,500 sea turtles. 8 Through the
hard work of conservation organizations and
researchers across the globe, we may still be
able to save the green sea turtle.
WORKS CITED
[1] Jacobson, E. R. et al. Dis. Aquat. Organ. 1991, 12.
[2] Carneiro da Silva, C., et al. Aquat. Toxicol. 2016, 170,
42-51.
[3] Sánchez-Sarmiento, A. M. et al. J. Mar. Biol. Assoc. U.
K. 2016, 1-9.
[4] Jones, K., et al. Vet. J. 2016, 212, 48-57.
[5] Borrowman, K. Electronic Theses and Dissertations.
2008
[6] Monezi, T. A. et al. Vet. Microbiol. 2016, 186, 150-156.
[7] Herbst, L. H. et al. Dis. Aquat. Organ. 1995, 22.
[8] The Turtle Hospital. Rescue, Rehab, Release. http://
www.turtlehospital.org/about-us/ (accessed Oct. 4, 2016).
DESIGN BY Vidya Giri
EDITED BY Tejus Satish
40 | CATALYST