Disease and Pathogens

Photo: Chris Johnson,
www.turtleimages.org www.floridaleatherbacks.com

“These tumored turtles are telling us that something is happening to the oceans and we need to pay attention to the consequences of our actions.”

Dr. Alonso Aguirre, Vice President, Conservation Medicine at Wildlife Trust

The environment that sea turtles live in prediposes them to different stresses that then can influence their susceptibility to health and disease problems. The different stresses can be environmental (salinity, pollution, temperature etc.), nutritional or physical (trauma or injury). Both wild and captive (sea turtles held in oceanariums, commercial farms, research instituions and head-start programmes

These can include the following:
• Nutritional problems (malnutrition/ iron deficiency/ metabolic bone disease)
• Bacterial
• Mycotic (Fungal infections)
• Viral
• Fibropapillomatosis (FP)
• Parasitic Conditions
• Environmental Health problems (injuries/hypothermic stunning)
• Anthropogenic Problems (entanglement/ingestion of debris/chemical pollutants)

Nutritional Problems

In wild sea turtles, nutritional deficiencies are usually in combination with other chronic diseases and/or a heavy parasitic burden. Captive sea turtles are fed a variety of diets that, if inappropriate, can cause gastrointestinal obstructions and malnutrition and even metabolic bone disease. Metabolic bone disease is due to improper calcium and phosphorus levels in food given in captivity. While juvenile captive turtles that are regularly fed diets consisting solely of squid and fish can develop life-threatening anemias, or iron deficiencies. Adjusting the diet and iron supplements can rehabilitate the condition.


Bacterial infections of the dermis (two main layers of tissue that make up the skin) are both common and highly visible in captive sea turtles. The symptoms on the turtle include leisons (sores), ulceration and discolouration of the dermis. Bacterial infections that affect sea turtles include: focal errosive dermatitis (FED); septicemia ulcerative cutaneous disease (SCUD), papillary dermatitis (PD); bacterial encephalitis and chylamydial infections. Treatment includes topical (on the skin) and systemic (into the blood stream) antibiotics, improvement in water quality, isolation of sick individuals and frequent water changes.

Mycotic (Fungal infections)

As sea turtles are solitary creatures, wild turtles are less vulnerable to mycotic infections. However in captive turtles in crowded conditions this can be a problem as fungi can spread from turtle to turtle very quickly. The symptoms are leisons (sores) that can be located both dermal (superficially on the skin) and systemic (infection of internal organs). Treatment for the less serious dermal infections includes improvement of water quality, topical iodine oitment and free-flowing not static water input. The treatment for the systemic infections are much more difficult and the mortality rate is very high as it can affect vital organs such as the lungs and liver.


There are only two viral infections known to affect sea turtles, these are herpesvirus respiratory disease and gray-patch disease (GPD). Another disease- Fibropapillomatosis (FP) may have a viral etiology (cause of the disease) but shall be discussed seperately as it has such a significant impact on sea turtles. Symptoms of herpesvirus respiratory disease include leisons in the mouth, conjunctivitis, tracheitis (infection in the trachea leading to the lungs). This disease can then trigger GPD especially juevinile green turtles. High temperatures, rapid changes in temperature, overcrowding and poor water quality are all stressors that induce this infection. This causes death in young turtles (2-6 weeks old) but older turtles can survive and become naturally innoculated (resistant) to the virus.

Fibropapillomatosis (FP)

As the incidence of sea turtles with FP have increased so rapidly in the past few years there is a serious concern that pollution causes vulnerability to contracting this unsightly disease.
Please see the section Fibropapillomatosis (FP) in Sea Turtles for more information.

Barnacle on a turtle shell
Parasitic Conditions

Sea turtles are affected by a range of parasitic conditions both internally and externally, if there is a serious infestation sea turtles can be severely affected. These parasites include leeches; barnacles; endoparasites; protozoans and helminths (parasitic worms). Leeches can occur in small or large numbers and use oral suckers to obtain blood from their host; these can be easily removed from captive turtles by a 90 minute bath in fresh water. Several varieties of barnacles can be found on sea turtles and can either do minimal stress such as increase surface drag or more serious with damage to shell causing bacterial or fungal infections to enter. Helminths such as flukes can affect sea turtles causing a range of symptoms from minor damage, irritation to leisons forming on the brain, lungs, liver, kidney and intestines.

This is a juvenile loggerhead turtle that was found as a "cold-stun" in winter in North Carolina, and was brought into captivity for rehabilitation before eventual release. © 2003 Matthew Godfrey
Environmental Health problems

Environmental problems can have an impact on sea turtles with either traumatic injuries or hypothermic stunning (or cold stunning). Traumatic injury can occur from bite wounds from sharks, birds, fish and during mating. Hypothermic stunning is from long-term exposure in cold water it causes the turtle to be lethargic and unable to function normally. They float on the waters surface and are unable to dive and feed. In severe cases they may die. Often they appear to be dead but are actually stunned, when treating these cases it is the goal to raise the body temperature slowly by immersion in warm water. Sometimes their salt gland is affected and requires to be maintained in fresh water until it has returned to normal.

Anthropogenic Problems

The impact of human pollution or ‘small garbage’ has serious implications for the health of sea turtles and causes the death of thousands every year. For more information about the impacts of humans on sea turtles click here. Link to EUROTURTLE-THREATS-SMALL GARBAGE


George, R. (1996) Health Problems and Diseases of Sea Turtles in Lutz, P. and Musick, J. (1996) The Biology of Sea Turtles. CRC Press. USA.