A parasite is an organism that derives nourishment by feeding on or within another animal. The most noted parasite in tortoises are worms. But worms are only part of the parasitic picture, however, as many non-worm parasites exist as well. Common parasites include ticks, mites, as well as worms, and other intestinal parasites; such as protozoa.
All parasites of concern can result in serious health damage and are a common cause of death among tortoises. It is not uncommon for keepers not to recognize this risk because tortoises die from complications associated with parasitic infections. In the wild, tortoises do indeed carry parasites, but because they are not confined to small areas parasites do not normally pose a risk to the animal. However, when captured and placed in a captive environment, the stress of overcrowding, improper environmental conditions, human handling, and being with mixed species the animal is susceptible to a proliferation of parasites of pathogenic proportions. The results can be quite serious and the effects range from acute diarrhea, dehydration, and in chronic cases the destruction of the normal digestive-tract system. With this the animal becomes malnourished and consequently causes damage to the immune system.

Life Cycles of Parasites

There are generally two types of life cycles. In the direct life cycle, the immature form of the parasite can infect the same host in which it came from. For example, the adult parasite lives in the host’s intestine, lays eggs, which are passed in the stool, and then the eggs can infect the same host over again. Hookworms are an example of a parasite that has a direct life cycle.
In the indirect life cycle, the immature form must pass through a different type of host before it can re-enter and infect the host it came from. An example here would be roundworms. The adult worm lives in the tortoise. The immature form cannot re-infect the tortoise unless an intermediate host picks it up, and then it is reintroduced into another tortoise where it develops into the mature adult and the cycle starts all over again.
Many parasites have life cycles that include a phase of migrating through the body, often from the digestive system to the lungs or other organs such as roundworms. Others, including hookworms, migrate from their entrance through the skin to other organs.
Most parasites are host-specific, which means they only infect and live in certain animals. If they enter the wrong animal, or host, they may not survive or may migrate abnormally. When a parasite enters the wrong host it is said to be aberrant. Often, aberrant parasites will cause an over-reaction in the body of this wrong animal and serious disease can result.
Infections that can be passed from animals to man are called Zoonotic Disease. There are many parasites that fit this category and include roundworms and hookworms.

Classification of Parasites

Nematodes: Generally, Nematodes are round in cross-section, are longer than wide, and are unsegmented. They come in many sizes, from microscopic to a yard in length. Nematodes are a significant cause of disease in tortoises. For every organ system in the body, there is probably a Nematode that lives there, or at least passes through. Though, they are in the same Class, Nematodes have extremely varied life cycles. Some require intermediate hosts, while others are facultative parasites. Some lay eggs, and others bear live larvae.
It is quite common to refer to the Class of Nematodes as Roundworms. This is a bit confusing since the term roundworm is used when referring to spaghetti-like intestinal worms. As a matter of fact, there are over 500 kinds of Roundworms or Nematodes, mostly infecting the intestines and stomach, but can migrate into the lungs and other body tissue.

Hookworms: Hookworms are small, thin worms and are difficult to see in the tortoise’s feces. They also have a direct life cycle, which poses significant danger to the animal. Hookworms latch onto the intestinal wall and live on blood, contributing to anemia, weakness, wasting away, and bloody diarrhea. The tortoise may die due to blood loss and shock where heavy infestations are present.
Roundworms: Roundworms are long, spaghetti-like worms and can also cause serious problems in tortoises. They have an indirect life cycle. They can cause the tortoise to appear fat, when in fact the animal may be malnourished, and can cause acute diarrhea. Roundworms can cause death if enough worms are present as they can cause an intestinal blockage.

Arachnids: Often the term Arachnid is associated with spiders. Yes spiders are Arachnids, but so are ticks, and mites. As a Class, Arachnids are carnivorous animals. Some feed on the tissue fluids of animals through a sucking apparatus. While others eat portions of other animal’s body through the use of their front legs that may have latches or hooks.

Protozoa: Protozoa are one-celled organisms and are microscopic. There are over 45,000 species of protozoa. Some protozoa are flagellates. Flagella are long, hair-like structures that can whip back and forth rapidly, propelling the organism. Other protozoa are ciliates. Cilia are much shorter, hair-like structures that often cover the organism. Although both these types of protozoa have been found in tortoises, the most commonly found are flagellates.
Although Flagellates may not be pathogenic and may aid in the digestive system; they can easily reach pathogenic proportions in a captive environment. This parasite is easily spread by the animal drinking contaminated water and being kept in poor hygienic conditions, as is often the case when the animal suffers the consequences of the pet trade. Protozoan infections can cause acute diarrhea, dehydration, and in chronic, severe cases, the passing of undigested food because the infection can contribute to the destruction of the normal intestinal flora.

Hexamita parva: Hexamita parva is a highly contagious flagellate organism that invades the renal-urinary system. This organism poses a serious life-threatening risk to the animal. When the animal is suffering from this infection they void highly concentrated, ammonia-smelling urine, and the urine may be tinted with blood. In chronic cases, the animal will appear to be wasted, and debilitated and may lose the ability to retract hind limbs. Any tortoise suspected of having this infection should be isolated and immediate veterinary care should be sought. If this infection is left untreated the organism will destroy the kidneys, causing renal failure and eventual death.

Entamoeba infections: Entamoeba is a water-borne pathogen that can cause acute diarrhea or more serious invasive liver abscesses. This parasite is a single-celled eukaryote. They have a simple life cycle that consists of an infective cyst stage and a multiplying trophozoite stage. Transmission of this infection occurs when cysts in contaminated water are consumed. Infection can lead to amoebic dysentery, resulting from trophozoites invading the intestinal wall, and amoebic liver abscess, resulting from the spread of trophozaites from the intestine via the bloodstream. Generally, aquatic turtles are carriers of this parasite, but it can be highly pathogenic when a tortoise contracts this infection.

In conclusion: Parasites pose a significant health risk to tortoises in a captive environment. Preventing parasitic infections is done by maintaining scrupulous hygienic conditions. When acquiring a new animal it is advised to quarantine this animal for at least three months before introduction into established collections. There are effective treatment for parasites, but it is important to recognize symptoms early on to successfully treat. Failure to recognize symptoms can often lead to the animal’s death.