Fibropapillomatosis of Marine Turtles

History: First described in captured adult green turtles (Chelonia mydas) in the 1930s (Lucke 1938; Smith and Coates 1938). It was also identified in mariculture-reared green turtles at Cayman Turtle Farm, Grand Cayman, B.W.I. in the late 1970's (Jacobson et al, 1989). In the 1980's the prevalence started increasing at multiple sites including Florida and Hawaii where more than 50% of certain populations were found to be affected (Balazs and Pooley 1991).
Host: Green turtles were the first marine turtle identified with fibropapillomatosis. Similar tumors have been found in loggerhead (Caretta caretta) and olive ridley (Lepidochelys olivacea) sea turtles.
Distribution: Worldwide; prevalence ranges from 0% to 92% in some areas. High prevalence areas are shallow near-shore waters with relatively restricted water turnover. Many (but not all) of these marine habitats are near areas of heavy human use.
Ages Affected: Juveniles, subadults, and adults. Not documented in hatchlings or posthatchlings.
Etiologic Agent: Transmissible sub-cellular particule (virus; Herbst et al, 1995). While the specific identity is unknown, a herpes-like virus has been identified in wild (Jacobson et al, 1991) and tumor induced captive green turtles (Herbst et al, 1995). However, this virus will need to be isolated and injected into naive turtles to reproduce the disease in order to establish a causal relationship.
Clinical Signs: Multiple benign cutaneous (skin) fibroepithelial tumors (Figure 1; Figure 2) which may be found at almost any site including soft and hard tissue parts (Jacobson et al, 1989). Tumors of the periorbital (Figure 3; Figure 4) and orbital tissues are commonly seen (Brooks et al, 1994). Tumors have been seen in the oral cavity of certain populations of green turtles in Hawaii (Balazs, pers. comm.). Affected turtles may be extremely emaciated, weak, depressed, and anemic. Affected turtles may have flotation problems resulting from fibrous tumors in the lungs. Fibrous tumors may be seen in multiple visceral sites [lung (Figure 5), liver (Figure 6), kidney (Figure 7), gastrointestinal tract] resulting in flotation problems, bowel obstruction, renal failure, and pressure necrosis of affected tissues (Herbst 1994).
Pathology: Externally, small to large multiple areas of minimal to mild epidermal hyperplasia, supported by a broad fibrovascular stalk (Jacobson et al, 1989). There seems to be a progression from proliferating, arborizing early tumors (Figure 8) to those which are primarily fibrous (Figure 9) having a relatively less verrucous surface, with a minimal to moderate amount of folding and a more significant dermal component. In some cases, spirochid trematode eggs can be seen with small vessels in the dermis of fibropapillomas (Figure 10). Although at one time considered to be a possible etiologic agent of GTFP, recent transmission studies have failed to implicate these ova as a cause of GTFP. Internal nodules may be found at multiple visceral sites [liver (Figure 11), kidney (Figure 12), lung, and gastrointestinal tract] and consist of areas of fibroplasia. In what is interpreted as the earliest lesions, vacuolar change (Figure 13) of epidermal cells in the stratum basale have been seen. In tumors of several stranded green turtles, focal areas of ballooning degeneration (Figure 14) of epidermal cells containing intranuclear inclusions (Figure 15), have been seen. Electron microscopic examination of these inclusions revealed a herpes-like virus (Figure 16). Similar inclusions and herpes-like virus have been seen in experimentally induced tumors.
Transmission: Exact route in wild unknown. Can be experimentally transmitted by skin scarification or cutaneous injection (Herbst et al, 1995).
Diagnosis: By light microscopic appearance of characteristic tumors. No diagnostic test is currently available to detect subclinical or latent infections.
Control: No current methods of managing the disease in wild populations. Avoid iatrogenic (caused by man) transmission by spreading the agent from turtle to turtle through handling and use of contaminated instruments such as calipers and tagging equipment. Wear gloves, change gloves, and disinfect instruments and equipment between turtles. When possible, handle healthy turtles before affected turtles. Prohibit transport and release of turtles from areas where disease occurs to "clean" areas. Treatment of individual turtles (surgery) may be attempted for individual animals but impractical as a means of control.
Current and Future Research:

  • Development of molecular and immunologic diagnostic tests.
  • Isolation and purification of the fibropapilloma associated herpesvirus.

References - please click link
For More Information Contact:
Dr. Larry Herbst
Institute for Animal Studies
Room 1005 Ullman
Albert Einstein College of Medicine
1300 Morris Park Ave.
Bronx, N.Y. 10461 USA
e-mail: herbst@aecom.yu.edu
Dr. Paul Klein
Box 100275
Department of Pathology and Laboratory Medicine
College of Medicine
University of Florida
Gainesville, Florida 32610-0275 USA
e-mail: paklein@college.med.ufl.edu
Dr. Elliott Jacobson
Box 100126
Department of Small Animal Clinical Sciences
College of Veterinary Medicine
University of Florida
Gainesville, Florida 32610-0126 USA
e-mail: jacobsone@vetmed.ufl.edu
Additional Links:
• The Archie Carr Center for Sea Turtle Research
• CTURTLE