Toxoplasma gondii

Toxoplasma gondii, also called T. gondii, is a protozoan parasite that inhabits most warm-blooded mammals. It is most commonly found in felines, from which the parasite spreads to other organisms. T. gondii feeds on organic tissue, disrupting the functions of the body. It can be found in contaminated food, soil, and the litter boxes of infected domesticated cats. T. gondii can also spread from a mother to an unborn child.

T. gondii causes a disease called toxoplasmosis. In most cases, toxoplasmosis is asymptomatic. Most people who contract the disease are entirely unaware of it. However, in some cases, it can cause flu-like symptoms. In extremely rare cases, toxoplasmosis can cause organ damage.

Because toxoplasmosis is usually asymptomatic, it is often very difficult for doctors to detect. If doctors suspect that a patient has contracted toxoplasmosis, they may send the patient to a lab that specializes in the disease. Once the disease is diagnosed, doctors may recommend that the patient wait for symptoms to subside. If symptoms are severe, doctors may use a variety of specialized medications to help kill the parasites.

Background

Toxoplasma gondii, also called T. gondii, is a protozoan parasite that is capable of infecting most species of warm-blooded animals. Toxoplasma are special types of disease-forming parasitic single-celled organisms. They feed on other microorganisms and organic tissues.

T. gondii's life cycle is composed of three stages: oocyst, tachyzoites, and bradyzoites. Oocysts are cysts containing zygotes. T. gondii oocysts are commonly found in feline fecal matter. From there, they can be spread by felines or anyone that has contact with the feces. It is not uncommon for T. gondii oocysts to make their way into waterways, soil, or food. In many cases, oocysts may be spread by birds and rodents that come into contact with infected food, water, soil, or fecal matter. These animals are called intermediate hosts.

Oocytes gradually develop into tachyzoites, the trophozoite form of T. gondii. During this stage, the tachyzoites begin to grow, stealing nutrients from their host. The T. gondii tachyzoites also begin rapidly multiplying, spreading throughout the body of their host. The parasites tend to cause tissue damage as they spread. If the infected person is pregnant, they may also spread to the fetus by traveling through the bloodstream.

As the life cycle of T. gondii advances, the infection tends to localize in both muscle tissue and the body's central nervous system. Once they arrive, the tachyzoites gradually transform into bradyzoites. Bradyzoites are a type of hardened cyst that can exist within muscle tissue for a prolonged period. However, in certain circumstances, bradyzoites can revert back to tachyzoites. This can cause a resurgence in the infection, or can cause an organism that has consumed bradyzoites by eating infected meat to contract the infection.

Overview

When T. gondii enters the human body, it results in an infection called toxoplasmosis. Humans can contract a T. gondii infection in the same ways as other warm-blooded animals. They might eat infected meat or shellfish, including food prepared by someone who had touched a contaminated object and not washed his or her hands. Infections may also result from ingesting contaminated soil, or from contact with the litter box of a cat that is infected. In rare cases, toxoplasma can be contracted through organ transplants from an infected donor.

Most people who contract toxoplasmosis do not show any symptoms. For this reason, they are entirely unaware that they carry the disease. However, when toxoplasmosis symptoms do appear, they can cause a variety of problems in afflicted individuals. Many people experiencing toxoplasmosis feel as if they have contracted the flu. They may experience long-term muscle aches and unexplained pains throughout the body. They may also notice swollen lymph nodes.

Should the infection become more severe, infected individuals may notice additional symptoms. Acute toxoplasmosis can result in gradual damage to numerous organs, including the brain. Should acute toxoplasmosis affect the eyes, it can cause pain, redness, tearing, and blurred vision. However, acute toxoplasmosis is extremely uncommon. It most often occurs in individuals with an otherwise compromised immune system. Should a child be born with a toxoplasmosis infection from his or her mother, the child is usually asymptomatic.

People concerned about contracting toxoplasmosis can avoid infection by ensuring that all food they consume is safely prepared. When cooking food, especially in an area near a cat’s litter box, anyone who handles food should make sure to wash their hands prior to cooking. Food should always be cooked to a safe temperature before eating. Some foods, such as pork and ground beef, may need to be cooked more carefully than others. A food thermometer can be used to check that any meat has been safely cooked before serving. Additionally, pregnant women who test negative for toxoplasmosis may want to be careful around rodents or litter boxes.

In most cases, toxoplasmosis does not require treatment. If a patient is experiencing symptoms, doctors normally advise that those symptoms are temporary, and will fade with time. Because most patients are asymptomatic or only experience mild discomfort, doctors tend to only recommend treatment if the patient is experiencing severe discomfort. Doctors may also request that the patient get tested at a lab that specializes in toxoplasmosis, ensuring that the symptoms they report are not caused by another recurring illness, before beginning to treat the disease.

Toxoplasmosis is traditionally treated through medication. In some cases, doctors recommend the uses of Pyrimethamine, a medication traditionally used to treat malaria. Though effective, it may cause folic acid deficiency, bone marrow suppression, and liver toxicity. Should that medicine fail, doctors may supplement it with Sulfadiazine.

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