Sea Turtles: Old Viruses and New
Tricks
Dispatch
Adam G. Jones
Recent years have seen an inexplicable increase in
the frequency of an appalling disease in sea turtles:
fibropapillomatosis, which is likely caused by a
herpesvirus and causes tumors to grow throughout
the turtle’s body. New research has led to the
disturbing conclusion that recent, human-induced
environmental changes are responsible.
Emerging diseases seemed to enter the nightmares of
mainstream culture with the ebola and hantavirus
scares of the 1990s. Since then, emerging diseases
have become a major health concern in human
populations, with such diseases as severe acute
respiratory syndrome (SARS), avian influenza and
West Nile virus disease sickening and scaring people
around the globe.
Most people do not realize that emerging diseases
are also a problem for wildlife and may be a major
threat to endangered species [1]. In the last decade,
there has been an increase in the number of cases of
a wide spectrum of diseases in populations of diverse
species of plants and animals [1,2]. Emerging
diseases in wildlife are important for the obvious
reason that they can cause population declines in the
susceptible species. But these diseases in wildlife are
important from a human health standpoint too,
because many of the emerging diseases in humans
have been linked to wildlife species that serve as
reservoirs of the pathogen. Furthermore, the study of
emerging diseases in wildlife may well provide general
insights that help us to understand the dynamics of
emerging diseases in human populations.
As reported in a paper just published in Current
Biology, Herbst et al. [3] investigated the cause of the
recent outbreak of marine turtle fibropapillomatosis by
examining the evolution of the virus that causes the
disease. This disease affects mainly the green sea
turtle (Figure 1), but cases have also been docu-
mented in loggerhead, olive ridley and now Kemp’s
ridley sea turtles. The fibrous growths typical of
fibropapillomatosis were first described in 1938 and
reports of the disease were relatively rare until after
1980 [4]. Now, fibropapillomatosis occurs around the
globe and in one recent sample from the Hawaiian
Islands more than 90% of green turtles showed symp-
toms of the illness [4].
From the standpoint of a wildlife enthusiast, fibropa-
pillomatosis is a heinous disease, marring the usually
noble appearance of the beloved sea turtles. The
growths associated with the disease occur mainly on
the soft skin of the turtle, but they can appear internally
as well. The growths can be so large that they interfere
with normal mobility, vision, feeding and organ func-
tion. In addition to these gross mechanical effects, the
disease appears to result in suppression of the
immune system and a susceptibility to bacteremia
[5,6]. Consequently, death is the ultimate outcome for
many of the turtles affected by the disease.
All the current evidence suggests that marine turtle
fibropapillomatosis is caused by a herpesvirus that
has been shown to be associated with the growths [7]
(although definitive experiments involving cultured
virus particles have not yet been possible). But why
does the virus causes so much harm now compared
to 50 years ago? Two non-exclusive hypotheses can
explain the sudden increase in frequency of
fibropapillomatosis (and most other emerging
diseases in wildlife for that matter). One possibility is
that a change in the environment caused the host
species to become extremely susceptible to a
previously harmless strain of virus, for example, as a
consequence of immune suppression, a new vector
and so on. The other possibility is that the disease is
Current Biology, Vol. 14, R842–R843, October 5, 2004, ©2004 Elsevier Ltd. All rights reserved. DOI 10.1016/j.cub.2004.09.038
Department of Biology, Texas A&M University, 3258 TAMU,
College Station, Texas 77845, USA.
E-mail: adam.jones@biology.gatech.edu
Figure 1. The green turtle, Chelonia mydas.
Images of uninfected green turtles (courtesy of Jack Lenz).