Tuesday, 18 March 2014

FP

Picture from http://fullspectrumbiology.blogspot.it
Not long ago (that is relative to my age...) I came across a picture of a very very sick sea turtle. I was horrified by it and I started researching about it. I discovered that the turtle was affected by fibropapillomatosis (FP), a tumour disease affecting marine turtles globally. But ... what do we know about it? Well, a few things:
  1. It seems to affect mainly green turtles, olive ridelys and loggerheads. 
  2. It doesn't affect humans.
  3. It was first observed and described in the late-1930s in Florida on green turtles by two biologists: Smith and Coates (1938).
  4. It's a chronic disease, and its affliction varies. Some turtles may have multiple massive tumours that affect their ability to swim or eat, leading to slow death, while others may have minimal tumours with little or no observable effect on the animal’s lifespan.
  5. Because marine turtles are largely out of sight and difficult to access, FP remains something of an “orphan disease” — off on its own, little studied, even dismissed as old news.
A Selective Disease
The FP are essentially a form of cancer and it almost exclusively affects green turtles and, to a lesser extent, olive ridleys and loggerheads. Turtles with FP typically get tumours on the skin of the flippers and neck, eyes, corners of the mouth, cloaca, and internal organs. Some tumours can exceed the size of a cantaloupe. Oral tumours are particularly nasty because they prevent the trachea from closing, and affected turtles often aspirate debris and rubbish, leading to infections and inflammation of the lungs leading to death. Fibropapillomatosis affect sea turtles through a variety of other mechanisms. Skin tumours can become abraded, thereby opening portals to bacterial infections in affected animals. Some tumours are so large that they can lead to blindness or an inability to eat (leading to starvation).

What is the cause?
Early research suggested that FP might be associated with flatworms, or blood flukes, a parasite that live in the turtle’s circulatory system. To support this, 100 percent of turtles with FP are infected with these worms. It is difficult to study because we do not know its life cycle. However, a high prevalence of turtles unaffected by FP are also infected with the blood flukes. It is more likely that a virus is involved with this disease, as both epidemiology and physical observations point to an infectious cause of FP. Captive, tumour-free green turtles in Florida, for example, have developed FP after contact with seawater from a tank that housed a turtle with a tumour. And microscopy has revealed the presence of herpesvirus particles in some tumours. This particular herpes virus has been named chelonid fibropapilloma herpes virus (CFPHV) to reflect the virus type (herpes), the disease with which it is associated (FP), and the hosts affected (Cheloniidae). Molecular studies suggest that CFPHV has existed in sea turtle populations for millions of years. Researchers have been exploring how CFPHV may be transmitted between turtles. Among the theories:
  • Tumours are more numerous in the front of the animals, so perhaps turtles come into contact with infected material as they explore their environment (therefore the virus can remain infectious in seawater).
  • Virus DNA has been found in leeches that cling to tumours of some turtles, suggesting the leeches may act as a vector.
  • Sea turtles commonly hang out in portions of the reef called “cleaning stations,” where they allow cleaner fish to "clean" them. Such cleaner fish have been observed biting tumours, and CFPHV DNA has been detected in some species of cleaner fish, so perhaps cleaner fish transmit the disease. We aren’t yet certain.
Human Complicity?
The prevalence of FP appears to be stable or increasing in most regions of the world, and human action may lie at the root of the expansion. For example, FP in Brazil is particularly prevalent in Espirito Santo Bay surrounded by heavy industry or in areas where invasive algae are prominent in Hawaii suggesting that a dietary or other environmental co-factor may be involved. Unfortunately, it's impossible to manipulate the virus in the lab and this has prevented researchers from developing a blood test to detect FP. So human complicity cannot be proved.... yet.

Thank you to The Wildilife Society News

Other sources:
The Wildlife Society News: http://news.wildlife.org/twp/2013-fall/tumors-in-sea-turtles/

Full Spectrum Biology: http://fullspectrumbiology.blogspot.it/2013/06/turtle-tumors-fibropapillomatosis-and.html

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