Fibropapillomatosis

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Fibropapillomatosis
Turtlewithfptumors0149026.jpg
Hawaiian green turtle with severe fibropapilloma tumors. Cleaner wrasses avoid feeding on the tumours.
Specialty Veterinary medicine

Fibropapillomatosis (FP) is a disease specific to sea turtles. The condition is characterized by benign but ultimately debilitating epithelial tumours on the surface of biological tissues. [1] A herpesvirus, Chelonid alphaherpesvirus 5 , is believed to be the causative agent of the disease, [2] while turtle leeches are suspected mechanical vectors, transmitting the disease to other individuals. [3] The disease is thought to have a multifactorial cause, including a tumour-promoting phase that is possibly caused by biotoxins or contaminants. [4] FP exists all over the world, but it is most prominent in warmer climates, affecting up to 50–70% of some populations. [1]

Contents

Description

A green sea turtle with significant fibropapilloma tumours basking on a beach north of Haleiwa, HI Green turtle with fibropapillomatosis.jpg
A green sea turtle with significant fibropapilloma tumours basking on a beach north of Haleiwa, HI

Fibropapillomatosis is a benign tumour disease of marine turtles, predominantly in the green sea turtle, Chelonia mydas, but it has also been reported in the loggerhead sea turtle Caretta caretta, olive ridley Lepidochelys olivacea, Kemp's ridley Lepidochelys kempii, and leatherbacks Dermochelys coriacea. [1] This neoplastic disease causes proliferation of papillary cells (hyperplasia) and gives rise to excess fibrous connective tissue in both epidermal and dermal skin layers – or more specifically, proliferation of dermal fibroblasts and epidermal keratinocytes. [5] [6] This causes tumorigenesis in sizes less than 1 cm up to more than 30 cm in diameter. [1] FP is most often found externally around the armpits, genitals, neck, eyes, and tails of turtles, but also occur in and around the mouth, and rarely in internal organs or on the carapace. This, in turn, impedes vision, feeding, and movement. [1] Around 25–30% of turtles with external tumours also have internal tumours, primarily in heart, lungs and kidneys. [1]

FP incidence is highest among immature and juvenile green turtles, while it is rare in adults. [6] The suggestions for this pattern include the tumours can regress and be cured, which has been documented in some individuals, even when tumours were severe. [7] However, the responses that cause these tumour regressions is unknown. Secondly, the juvenile individuals with FP might die before reaching adulthood. [7]

Prognosis

The tumours appear to be benign and can be present for many years, but if large, can mechanically hamper sight, swallowing, and swimming, which may ultimately be fatal. [1] While external tumours hamper movement and sight, internal tumours interfere with system functioning, another potentially fatal factor. [1] As the tumours progress, individuals with large numbers of tumours may become anaemic, have a lack of proteins and iron, and in more advanced stages even suffer from acidosis caused by imbalanced calcium/phosphorus ratios and severe emaciation. [1]

Other species

Fibropapillomas are present in other animal groups, but are caused by different viruses, for example the bovine papillomavirus. [5]

History

The first documented case of the disease was in 1938 in Key West, Florida. [1] Long-term studies found no signs of the disease on Florida's Atlantic coast in the 1970s, but during the 1980s FP was recorded in incidences varying from 28–67%. [1] Today, incidences as high as 92% have been reported in Kaneohe Bay, Oahu, Hawaii. Generally, FP is most prominent in warmer climates. Recent research has found that FP is caused by stress and tumours have been observed in turtles that are part of turtle tourism tours. It is thought that the presence of tourists causes the turtles stress [1]

Cause

The FP is an infectious disease with horizontal transmission. [1] An alphaherpesvirus called fibropapilloma-associated turtle herpesvirus (FPTHV) is believed to be the causative agent of the disease, though no real proof of its causality exists. The reason for this belief is because nearly all tissue samples tested from turtles with lesions carry genetic material of this herpesvirus, varying between 95 and 100% depending on different studies and locations. [1] [2] [4] The DNA loads of the herpesvirus in tumour tissue are 2.5–4.5 logarithms higher than in uninfected tissue. [8] The FPTHV herpesvirus has been found in turtles free from FP and this suggest that the FP progression is multifactorial and might even involve some sort of tumour-promoting phase. [4] The global prevalence of the disease also suggests a multifactorial cause, rather than single factors or agents. [4] [9] Possible factors include some parasites, bacteria, environmental pollutants, UV-light, changing water temperatures and biotoxins. Even physiological factors such as stress and immunologic status appear to be associated with FP. [1]

The leech genus Ozobranchus is thought to be the mechanical vector of the herpesvirus, transmitting the virus from one turtle to another. These leeches are common turtle ectoparasites that exclusively feed on turtle blood, and some leeches have been found carrying more than 10 million copies of the herpesvirus DNA. [3] The green sea turtle is an herbivore and feeds primarily on seagrass and macroalgae. [4] [6] Two toxins which are suspected to be associated with FP are found epiphytically on these plants. [1] [4] First, the toxic compound lyngbyatoxin from the cyanobacterium Lyngbya majuscule, [4] and second the toxin okadaic acid – a documented tumour-promoting toxin - from the dinoflagellate Prorocentrum . [1] Again, causality has not been concluded, but an association seems to exist between the distribution of especially the dinoflagellates and the occurrence of FP, and as they are found on weeds, they can be ingested by foraging green sea turtles. [1] [4] Turtles with FP are found to have a compromised immune system. [6] They have higher phagocytic leucocyte counts (especially heterophils) compared to healthy individuals, which seems to be an effect of FP, as it is mostly evident in individuals with severe tumours. [6] [10] This further supports the hypothesis of the herpesvirus as a causative agent. [10] Immunosuppression is strongly correlated with FP, but does seem to be a consequence of the development and growth of FP rather than a prerequisite, which is similar to other virus-induced tumour diseases in other species, such as Marek's disease in poultry. [1] [6]

Treatment

Surgical removal of tumors caused by FP is the most common treatment method. Photodynamic therapy and electrochemotherapy are also used, [11] as is CO2 laser surgery. [12]

Epidemiology

FP affects green sea turtle populations all over the world, making it a panzootic. [1] It is especially found in warmer climates, such as the Caribbean, Hawaii, Japan, and Australia, where up to 70% of individuals in a population have FP. [1]

Epidemiological links are seen between FP rates, nitrogen footprints, and invasive macroalgae. [13] The strongest association with FP is with habitat type, especially increased anthropogenic activity causing high-nitrogen footprints in a surrounding environment where green sea turtles are found. [4] [6] [13] Sea turtles do live in very complex ecosystems, with both near-shore habitats and several years in the open ocean, which makes study of ecosystem associations difficult. [6] Even so, observations support the hypothesis that near-shore habitats have a strong correlation with the disease, as newly recruited individuals from the pelagic life phase have never been found with tumours, [4] and when migrating to more shallow ocean zones, such as the neritic zone, individuals still remain free from FP, but when entering lagoon systems, turtles may become infected. [13] The high prevalence of FP is also associated with habitats’ poor quality, while FP is absent in some habitats of good quality. [13]

Turtles are known to be robust to physical damage, but are surprisingly very susceptible to biological and chemical contaminants caused by anthropogenic activity. [13] As the turtles forage on invasive macroalgae in nutrient-rich waters, they can ingest environmental nitrogen in the form of arginine, which is known to regulate immune activity, promote herpesviruses, and contribute to tumorigenesis. [13]

Related Research Articles

Sea turtle Reptiles of the superfamily Chelonioidea

Sea turtles, sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the green sea turtle, loggerhead sea turtle, Kemp's ridley sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle, and leatherback sea turtle.

Soft-tissue sarcoma human disease

A soft-tissue sarcoma(STS) is a form of sarcoma that develops in connective tissue, though the term is sometimes applied to elements of the soft tissue that are not currently considered connective tissue. There are a number of types.

Cheloniidae family of turtles

Cheloniidae is a family of typically large marine turtles that are characterised by their common traits such as, having a flat streamlined wide and rounded shell and almost paddle-like flippers for their forelimbs. The six species that make up this family are: the green sea turtle, loggerhead sea turtle, olive ridley sea turtle, hawksbill sea turtle, flatback sea turtle and the Kemp's ridley sea turtle.

Kaposis sarcoma-associated herpesvirus species of virus

Kaposi's sarcoma-associated herpesvirus (KSHV) is the ninth known human herpesvirus; its formal name according to the International Committee on Taxonomy of Viruses (ICTV) is Human gammaherpesvirus 8, or HHV-8 in short. Like other herpesviruses, its informal names are used interchangeably with its formal ICTV name. This virus causes Kaposi's sarcoma, a cancer commonly occurring in AIDS patients, as well as primary effusion lymphoma, HHV-8-associated multicentric Castleman's disease and KSHV inflammatory cytokine syndrome. It is one of seven currently known human cancer viruses, or oncoviruses. Even after so many years of discovery of KSHV/HHV8, there is no known cure for KSHV associated tumorigenesis.

Loggerhead sea turtle Species of marine reptile distributed throughout the world.

The loggerhead sea turtle, also commonly called Caretta Caretta, is a species of oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the family Cheloniidae. The average loggerhead measures around 90 cm (35 in) in carapace length when fully grown. The adult loggerhead sea turtle weighs approximately 135 kg (298 lb), with the largest specimens weighing in at more than 450 kg (1,000 lb). The skin ranges from yellow to brown in color, and the shell is typically reddish brown. No external differences in sex are seen until the turtle becomes an adult, the most obvious difference being the adult males have thicker tails and shorter plastrons than the females.

Green sea turtle Species of large sea reptile of the family Cheloniidae

The green sea turtle, also known as the green turtle, black (sea) turtle or Pacific green turtle, is a species of large sea turtle of the family Cheloniidae. It is the only species in the genus Chelonia. Its range extends throughout tropical and subtropical seas around the world, with two distinct populations in the Atlantic and Pacific Oceans, but it is also found in the Indian Ocean. The common name refers to the usually green fat found beneath its carapace, not to the color of its carapace, which is olive to black.

A passenger virus is a virus that is frequently found in samples from diseased tissue, such as tumours, but does not contribute to causing the disease.

Primary effusion lymphoma Primary effusion lymphoma (PEL) is a large B-cell lymphoma located in the body cavities, characterized by pleural, peritoneal, and pericardial fluid lymphomatous effusions and that is always associated with human herpes virus-8 (HHV-8)

Primary effusion lymphoma (PEL) is a B-cell lymphoma, presenting with a malignant effusion without a tumor mass.

Human herpesvirus 6 Informal grouping of viruses which caused human herpesvirus 6 Infection

Human herpesvirus 6 (HHV-6) is the common collective name for Human betaherpesvirus 6A (HHV-6A) and Human betaherpesvirus 6B (HHV-6B). These closely related viruses are two of the nine herpesviruses known to have humans as their primary host.

Feline viral rhinotracheitis upper respiratory or pulmonary infection of cats

Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection of cats caused by Felid alphaherpesvirus 1 (FeHV-1), of the family Herpesviridae. It is also commonly referred to as feline influenza, feline coryza, and feline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide. The other important cause of feline respiratory disease is feline calicivirus.

Kaposis sarcoma connective tissue cancer

Kaposi's sarcoma (KS) is a type of cancer that can form masses in the skin, lymph nodes, or other organs. The skin lesions are usually purple in color. They can occur singularly, in a limited area, or be widespread. It may worsen either gradually or quickly. Lesions may be flat or raised. Human herpesvirus 8 (HHV8) is found in the lesions of all those who are affected. Risk factors include poor immune function, either as a result of disease or specific medications, and chronic lymphedema.

Spirorchiidae is a family of digenetic trematodes. Infestation by these trematodes leads to the disease spirorchiidiosis. Spirorchiids are mainly parasites of turtles. It has been synonymised with Proparorchiidae Ward, 1921, Spirorchidae Stunkard, 1921, and Spirorchiidae MacCallum, 1921.

Threats to sea turtles

Threats to sea turtles are numerous and have caused many sea turtle species to be endangered. Of the seven extant species of sea turtles, six in the family Cheloniidae and one in the family Dermochelyidae, all are listed on the IUCN Red List of Endangered Species. The list classifies six species of sea turtle as "threatened", two of them as "critically endangered", one as "endangered" and three as "vulnerable". The flatback sea turtle is classified as "data deficient" which means that there is insufficient information available for a proper assessment of conservation status. Although sea turtles usually lay around one hundred eggs at a time, on average only one of the eggs from the nest will survive to adulthood. While many of the things that endanger these hatchlings are natural, such as predators including sharks, raccoons, foxes, and seagulls, many new threats to the sea turtle species have recently arrived and with

Turtle leech genus of leeches

Turtle leeches are a genus, Ozobranchus, of leeches (Hirudinea) that feed exclusively on the blood of turtles. Only two species – Ozobranchus margoi and Ozobranchus branchiatus – are found in the Atlantic coast of the United States and the Gulf of Mexico. Little is known about these leeches due to difficulties in studying their sea turtle hosts.

Chelonitoxism is a type of food poisoning from eating marine turtles. It is considered rare.

Cape Byron Marine Park is one of four Marine Parks in New South Wales, Australia, and is the most recently sanctioned. The Cape Byron Marine Park is located in Northern NSW and extends 37 kilometres (23 mi) from the Brunswick River to Lennox Head. The Marine Park extends out to 3 nautical miles which dictates the border between state and federal jurisdiction. The marine park covers the area of 220 square kilometres (85 sq mi) and includes a variety of marine terrain including beaches, rocky shores, open ocean and the tidal waters of the Brunswick River and its tributaries, the Belongil creek and Tallow Creek. The Cape Byron Marine Park was declared in 2002 and the zoning plan was implemented in April 2006. Of the 15 distinct marine ecosystems identified within the Tweed-Moreton bioregion, the Cape Byron Marine Park supports 10 of these.

Platylepas hexastylos is a species of barnacle in the family Platylepadidae. It is native to the Indo-Pacific Ocean where it lives as a symbiont of such large marine creatures as the dugong, the green sea turtle, the olive ridley sea turtle, or the loggerhead sea turtle.

<i>Chelonibia testudinaria</i> species of crustacean

Chelonibia testudinaria is a species of barnacle in the family Chelonibiidae. It is native to the Atlantic Ocean, Mediterranean Sea and Gulf of Mexico where it lives as a symbiont on sea turtles, being particularly abundant on the loggerhead sea turtle.

Ozobranchus branchiatus is a species of leech in the family Ozobranchidae. It is found in the Atlantic Ocean and is a permanent parasite of sea turtles, mostly the green sea turtle.

<i>Chelonid alphaherpesvirus 5</i> species of virus

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References

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