Cancer Initiation: A wave of cancer has (again) hit the sea turtles of Florida

Thursday, March 30, 2017

A wave of cancer has (again) hit the sea turtles of Florida

Introduction


   Today we go on a Spring Break trip to the Gumbo Limbo Nature Center in Boca Raton, Florida. I was pleasantly greeted by the wonderful volunteers there, but all is not well. Getting right to the point, we (I) are informed that about 70 percent of green sea turtles (Chelonia mydas ) that come into the facility arrive with varying degrees of fibropapillomatosis. As the link shows, this is the name given to cancerous growths, or tumors that arise on sea turtles. Within the facility, infected turtles are referred to as "FP" infected.

 Welcome to Gumbo Limbo Nature Center  of Boca Raton!
The  exact cause of the tumors is not yet known. The local research center in Boca Raton is Florida Atlantic University, and they have provided a report on FP as long ago as 2001 [1].  It is now regarded to be at the intersection of a few factors. One of them is a herpes virus that is specific to sea turtles [2]. Although a viral vector is known to be driving tumor growth, that is not the whole story. The virus is thought to be ancient, and like many other members of the herpes virus family, it has co-evolved with the sea turtle, so it is species specific. So then, healthy turtles have immune systems that make them resistant to this virus. On the other hand, when infected turtles are discovered and recovered, during the process of rehabilitation, they have found to be immune-suppressed.[1]. Sea turtles have a family of white blood cells that is much like humans, and cell counts of these leukocytes have found them to be below normal.. For the sake of this article, that is the definition of immune-suppressed.


 A plastic model of FP ( with cotton balls representing neoplasms )  on display

 

The Mystery


  So then, the mystery is what causes the immuno-suppression that leads to the turtles inability to defend itself from the virus? Unfortunately, there are many potential causes, and most likely, it is not a single cause but a combination or summation that may in fact be different for each turtle. Known causes of turtle stress are, abnormal weather, ( reptiles are at the mercy of the environment for their temperature regulation ), nutrient runoff, heavy metal accumulation ( mercury, lead, arsenic ) , and pesticides and herbicides.

 This is Jade. notice that there is a melon sized growth on his port stern. Jade is currently awaiting surgery

Turtles as a model system.


 We have previously discussed the interaction between environmental factors such as nutrition and exposure to toxins and the immune system. Because we have many of the same factors here, the case of the sea turtle cancer epidemic is relevant, at least in a research sense, to cancer epidemics in humans.  As a model system, the exact causes of this epidemic could probably be easily found if the proper resources were applied.  Although, the turtles are merely wild life, the lessons learned from solving this problem would be easily translatable to humans. We are really no better at addressing human cancer epidemics than we are addressing wildlife epidemics.


According to their status chart, Gumbo Limbo currently has 3 turtles that are infected with FP. Jade is labeled in the upper right hand corner.

As a close up of the key shows, red dots mean FP ( fibropapilloma ) positive


A close up view of the melon sized tumor on Jade.

 

Discussion


   The story of the green sea turtles plight is actually very relevant to issues facing humans. Viral vectors are also responsible for some  tumors in humans, and we are in most cases, reliant upon our immune systems to protect us. The study of how these causative factors interact to create cancer would ultimately help our understanding of medical issues facing humans.

 Acknowledgments


  Thanks to the volunteers at the Gumbo Limbo Nature Center for their dedication and the time they spent with me to explain their operation, and even take some close up pictures for me.  The most profoundly affected turtles are off limits to the general public.

 

References


[1]Lutz, P. L.; Cray, C.; Sposato, P. L. . Studies of the association between
immunosuppression and fibropapillomatosis within three habitats of Chelonia mydas

(Report). Southwest Fisheries Science Center. [pdf]

[2]Lackovichl et. al Association of herpesvirus with fibropapillomatosis of the green turtle Chelonia  mydas and the loggerhead turtle Caretta caretta in Florida  Diseases of Aquatic Organisms Vol. 37: 89-97, 1999 l  [pdf]


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