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. The green sea turtle is an herbivore and feeds primarily on seagrass and macroalgae. Two toxins which are suspected to be associated with FP are found epiphytically on these plants. First, the toxic compound lyngbyatoxin from the cyanobacterium Lyngbya majuscule, and second the toxin okadaic acid – a documented tumour-promoting toxin - from the dinoflagellate "Prorocentrum". 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. Turtles with FP are found to have a compromised immune system. 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. This further supports the hypothesis of the herpesvirus as a causative agent. 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. Surgical removal of tumors caused by FP is the most common treatment method. Photodynamic therapy and electrochemotherapy are also used, as is CO2 laser surgery. FP affects green sea turtle populations all over the world, making it a panzootic. 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. Epidemiological links are seen between FP rates, nitrogen footprints, and invasive macroalgae. 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. 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. 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, 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.