Internal Parasites

posted: 05/15/12
More Information[b]Turtles, Tortoises & Terrapins Main[/b], [b]Reptile Guide Main[/b]

Turtles and tortoises are fortunate that they are not as susceptible to as many varieties of parasites that most mammals, birds, and other reptiles are plagued with. However, there are several internal and external parasites that can cause severe problems and even death, if they are not properly treated. Most parasitic problems in turtles and tortoises occur when the animals are either kept in close captivity with other turtles or tortoises or when kept in unsanitary housing conditions.

One important note when it comes to treating turtles and tortoises concerns the use of the antiparasitic drug ivermectin. While ivermectin is one of the most effective antiparasitic drugs in the world, it should never be used on turtles or tortoises. It can be extremely toxic and cause death, if administered to turtles or tortoises. If there is any question as to the safety of an antiparasitic drug in turtles and tortoises, a qualified veterinarian should be consulted.


Nematodes are one of the most common parasites found in turtles and tortoises. These internal parasites are similar to the common roundworms that infect most mammalian species. The infection occurs when a healthy turtle ingests the tiny roundworm eggs that have been deposited in the environment through infected turtles feces. The eggs hatch, the larvae mature, and the worms set up residence in the digestive tract and will continue to reproduce and grow. Turtles and tortoises with a heavy worm load will often have symptoms of weight loss, diarrhea, and possibly vomiting of worms.

Diagnosis is either made by seeing the worms in the feces or vomitus, or more commonly, through a fecal sample examined under a microscope. Treatment is best achieved with the oral administration of the antiparasitic drug fenbendazole. The suggested dose is 23 mg per pound given once and then repeated in 14 days. Another effective drug is oxfendazole, however, this drug is sometimes more difficult to find in the United States.

Tapeworms and Flukes

Tapeworms and flukes can infect aquatic turtles, but are rare in tortoises. These parasites need to go through an intermediate host and are not much of a problem in most well-cared-for captive turtles. If the small worms are seen in the feces or diagnosed through a fecal exam, they can be successfully treated with praziquantel (Droncit) or oxfendazole.

Flagellate Organisms

Flagellate organisms are present in many healthy tortoises and turtles, however, if they are present in high numbers, they can cause severe intestinal problems. Flagellates are protozoans with the most common genus being Trichomonas. These small, highly motile, whip-like organisms live in the intestinal tract and can be easily identified through a microscopic fecal exam. Severe infestations of Trichomonas can lead to diarrhea, dehydration, weight loss, and the passage of undigested food. The presence of these organisms in the feces does not always indicate an infection, and the veterinarian needs to determine if they are actually causing a problem before initiating treatment. The common drug used for treatment is metronidazole. While metronidazole is an effective drug, caution must be used to avoid killing off all of the good organisms in the intestinal tract resulting in a sterile intestine. Feeding yogurt, or in more severe cases, the feces from a healthy tortoise, may be necessary to re-seed the intestine after metronidazole treatment.

Dietary deficiencies or excesses, such as an excessive intake of high sugar-fruit, are often a common cause of increased levels of flagellate organisms. Diets that are too low in dietary fiber can also be a cause. Keeping tortoises of different species together in the same enclosure or overcrowding is another factor, which significantly increases their likelihood of developing problems with flagellate organisms. Another cause of outbreaks in tortoises is associated with excessively high overnight temperatures or unrestricted access to heat lamps. Tortoises that are fed a natural diet and those that are allowed to graze under more natural conditions rarely develop flagellate problems. Allowing tortoises an appropriate cooling period at night will often greatly diminish their risk of developing a problem with trichomonas.


This is just a small listing of some of the common parasites that can infect turtles and tortoises. Good housing, proper nutrition, and regular physical exams including fecal checks can go a long way in preventing parasitic problems. If you suspect that your turtle or tortoise is harboring a parasite, contact your veterinarian immediately.

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Turtles and tortoises should NEVER be treated with ivermectin.

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