Across the globe, a widespread disease affects sea turtle populations, causing large, obstructive growths on their bodies. This ailment presents a significant challenge to the health and survival of these marine reptiles. The sight of an afflicted turtle highlights a complex interplay between disease and environmental health, prompting questions about the underlying causes.
Understanding Fibropapillomatosis
The disease responsible for these growths is called fibropapillomatosis (FP). It is characterized by benign tumors that can develop on the soft tissues of a turtle’s body. These tumors often have a cauliflower-like appearance and can vary in color from pink and gray to black. While technically non-cancerous, the tumors become debilitating due to their size and location.
FP is found in sea turtle populations worldwide, but it most commonly and severely affects green sea turtles. Tumors can appear anywhere on the body but frequently appear on the flippers, neck, chin, and around the eyes. Fibropapillomas can also form on internal organs, including the heart, lungs, and kidneys, creating complications that are not outwardly visible.
The disease is most prevalent in warmer climates, where it can impact a high percentage of certain populations. Documented in turtles since 1938, it has become more widespread in recent decades. The tumors are most often observed in juvenile and subadult turtles, with a lower prevalence in mature adults.
Investigating the Causes
The direct cause of fibropapillomatosis is believed to be a species-specific virus, chelonid alphaherpesvirus 5 (ChHV5). This herpesvirus is found in nearly all tumor tissue from afflicted turtles, often in much higher concentrations than in unaffected tissue. The virus is thought to be transmitted between turtles through direct contact or the water column.
However, the virus alone does not appear to be the full story. Scientists have found ChHV5 in turtles without the disease, which suggests other factors are involved in triggering tumor growth. Outbreaks and higher prevalence often occur in coastal waters heavily impacted by human activity.
These impacted environments, particularly with agricultural or urban runoff, can be high in pollutants. Elevated nitrogen from this runoff can lead to coastal eutrophication, which changes local marine vegetation. Some studies suggest these conditions promote algae rich in an amino acid called arginine, which may fuel the virus and promote the cell growth that forms tumors.
Effects on Sea Turtle Survival
Large growths on the flippers can hinder a turtle’s swimming, affecting its ability to forage for food, migrate, or escape from predators. When tumors form around the mouth and jaw, they can physically block a turtle from eating, leading to starvation and dehydration.
Growths on or over the eyes are particularly damaging, as they can cause irritation, infection, and eventual blindness. This leaves the turtle unable to navigate its environment or find food. The cumulative effect of these impairments makes afflicted turtles weak and more vulnerable to secondary infections from ulcerated tumors.
Turtles with severe cases of FP are also more susceptible to other threats, such as boat strikes, because their mobility and senses are compromised. The internal tumors add another layer of danger, disrupting the function of major organs. While some turtles with mild cases have been known to experience tumor regression, for many, the disease is debilitating and ultimately fatal without intervention.
Treatment and Conservation Efforts
A turtle with severe fibropapillomatosis may be taken to a rehabilitation facility for treatment. The primary method is the surgical removal of external tumors, often using CO2 lasers to minimize bleeding and improve recovery time.
This process is intensive and requires specialized care. After surgery, turtles undergo rehabilitation to ensure they are healthy enough to be returned to the wild. The survival rate for turtles receiving this treatment can be high, showing the effectiveness of direct intervention.
While treating individual turtles is an important response, it does not address the root of the problem. Long-term conservation strategies focus on the environmental factors that contribute to FP outbreaks. Improving water quality by reducing pollution in coastal habitats is a primary step toward mitigating the disease’s impact.