What is toxoplasmosis, symptoms, causes and how to treat the disease


The Centers for Disease Control and Prevention has described "Toxoplasma" as a "neglected parasitic infection" and a public health goal

One in three people has a potentially harmful parasite inside their body, in tiny cysts that the immune system cannot eliminate or antibiotics can affect. But new research reveals clues about how to stop it: interfere with its digestion during this latent phase.

If the discovery, made in the University of Michigan, in the United States, leads to new treatments, could help prevent a parasitic disease called toxoplasmosis that makes people around the world sick. For many people, the parasite 'Toxoplasma gondii' causes only flu-like symptoms, often from food poisoning and after that initial infection, it usually enters the cystic phase and remains in the person's body for rest of his life

But in people with weak immune systems or pregnant women, the infection can cause problems immediately or after the cysts become active, damaging their brain, eyes or the fetus they carry. Even healthy people can suffer repeated retinal damage if the parasite is located in their eyes. Some evidence even links it to mental illness.

A team from the University of Michigan School of Medicine has just published its findings on the recently discovered vulnerability of ‘Toxoplasma’ tissue cysts in ‘Nature Microbiology’. They report that a molecule called ‘cathepsin protease L’, or CPL, is crucial for the parasite’s ability to survive the cystic phase and cause disease in mice. By interfering with CPL on a genetic level, and also with a drug, they stopped toxoplasmosis.

These experts show for the first time that a form of parasite digestion - called autophagy and directed by CPL - is crucial for Toxoplasma's ability to persist. It is the first time it has been demonstrated in ‘Toxoplasma’ under normal conditions, according to the authors of the research.

"The greatest unmet need in toxoplasmosis is to deal with the stage of chronic infection, which is the source of potentially serious disease through the reactivation of the cyst parasite," explains the leader of the research team, Vern Carruthers, professor. of Microbiology and Immunology at the UM.

“Although there are reasonably good treatments for acute infections and the immune system does a good job in healthy people when it comes to keeping it under control, there are no options to eliminate the cyst form in order to protect immunocompromised people and those who they had a previous eye infection, ”he adds.

Carruthers and his team discovered the crucial role of CPL and the importance of autophagy in the course of several experiments on cysts, which contain forms of parasites called bradyzoites.

CPL is a protease, or protein digestion molecule that can help the ‘Toxoplasma’ cysts survive by digesting the parasite’s own bowels or by digesting materials that can enter the cyst outside. When CPL was disabled, the vacuolar compartment that serves as the “stomach” of the parasite experienced an accumulation of materials that disabled the entire cyst.

For the new document, the team temporarily opened holes in the parasite's membrane and removed the existing copy of the CPL gene, or added a modified gene to make an altered form of CPL. This "gene therapy" approach allowed them to study the impact of altered or absent CPL activity.

An unattended parasitic infection

The Centers for Disease Control and Prevention has described ‘Toxoplasma’ as a “neglected parasitic infection” and a public health goal. In addition to a high infection rate worldwide, the CDC estimates that about one in ten Americans carry the parasite.

In addition to undercooked meat that can spread the bradyzoite cysts of ‘Toxoplasma’, the parasite is often transmitted to humans through cat feces that contain another form of cyst. That is why public health authorities advise pregnant women not to change cat litter boxes and that everyone who eats meat consumes it completely cooked.

The main danger of ‘Toxoplasma’ is that it is one of the few infections capable of crossing the blood-brain barrier, which means it can enter the nervous system, including the retina, spinal cord and brain. It can also hide in the muscle tissue of both humans and animals.

Carruthers' group used a drug to deactivate the parasite in infected human cells, but that drug cannot cross the blood brain barrier, so it will not be useful for treatment. However, he is working with the team led by Scott Larsen, in the Department of Medicinal Chemistry of the UM School of Pharmacy, to look for other drugs that can inhibit CPL.

"This document is the proof of principle that protein digestion is important for the cyst stage of the parasite's life cycle, although we still don't know if it digests them to generate energy or to eliminate unnecessary materials," says Carruthers. We still have a lot to learn about ‘Toxoplasma’, how the cyst membrane acts as a barrier and if we can inhibit it from the outside. ”

If the parasites in the cysts are not taking 'food' from outside themselves, the process of autophagy can be a self-preservation effort, similar to staying in the bones of the starving humans as their bodies consume muscle. To stay alive

Therefore, blocking this process would cause the cyst to starve faster. Or, if the food is manufactured in the cysts, incapacitating CPL could lead to a microscopic "intestinal obstruction" where waste and unused food accumulate to a lethal level.

Carruthers, whose team has studied the parasite for years, notes that any future drug directed at the stage of tissue cyst would have to travel through the cystic membrane and also the blood brain barrier.

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Toxoplasmosis is an infectious disease caused by the parasite ‘Toxoplasma gondii’. Only rarely can it be serious. The specific causes of the infection are frequently eating contaminated meat or touching infected cat feces. It is also transmitted from mother to child during pregnancy.

Causes of toxoplamosis

Very common parasite

‘Toxoplasma gondii’ is a very common parasite in the world. It is found in the feces of cats. The most frequent causes of the infection are:

- Touch cat feces.

- Eat infected food or drink infected water.

- Receive a transplant from an infected organ.

The most common is that the infection remains in nothing, since the immune system is enough in many cases to restore normalcy to the body and the parasite is resident in the body, but without activity. This means that the patient is immunized and will never be infected again. But sometimes the infection affects various organs such as the brain or the heart because the immune system is weak. It can even affect the eyes and in extreme cases cause blindness.

There are some factors that increase the chances of infection: having AIDS, having a weakened immune system because of chemotherapy or taking steroids on a regular basis.

Symptoms of toxoplasmosis

There are usually no symptoms

Most of those infected with toxoplasmosis have no obvious symptoms, but sometimes some appear as fever, feeling tired, headache and nausea. If the patient has a weak immune system, then he may have seizures and blurred vision.

How it spreads

People can get toxoplasmosis:

  • by touching or coming into contact with infected cat feces (or poops). Cats can get the infection by eating rodents, birds or other small animals infected
  • when eating raw or undercooked meat from infected animals (especially lamb, pork or deer)
  • when ingesting raw and unwashed fruits, vegetables or vegetables, which have come into contact with manure
  • at birth infected with the disease (a woman with a toxoplasmosis infection can transmit the parasite to the fetus through the bloodstream)
  • by ingesting (or swallowing) the parasite's eggs without knowing it, which can remain in the hands after touching the earth without wearing gloves or handling uncooked or washed food
  • when drinking contaminated water

Although this infection is not normally spread from one person to another, excluding cases of maternal-fetal transmission, rarely, toxoplasmosis can contaminate blood transfusions and donated organs for transplants.

Toxoplasmosis diagnosis

To know with certainty if there is infection by toxoplasmosis it is necessary to carry out specific analyzes for this issue. It is also usual for pregnant women to perform this type of analysis to prevent the spread of the baby. Two usual tests are amniocentesis and ultrasound.

Signs and symptoms

Toxoplasmosis is transmitted from animals to humans, sometimes without causing any symptoms. When children have symptoms, they vary depending on the age of the child and the response of their immune system to the infection. (Both humans and infected cats do not usually show any signs of a toxoplasmosis infection.)

Toxoplasmosis in children

Toxoplasmosis in children can be one:

  1. congenital toxoplasmosis (when the child becomes infected before birth).
  2. Mild toxoplasmosis that affects healthy children (similar to infection in pregnant women).
  3. symptomatic toxoplasmosis, when it affects children with weakened immune systems.

Congenital toxoplasmosis

When a woman contracts toxoplasmosis (even if she has no symptoms) during pregnancy and receives no treatment, there is a possibility that she will transmit the infection to the fetus she carries in her belly. Babies who become infected during the first trimester of pregnancy are those who tend to have more severe symptoms.

It is very unlikely that a woman who contracted toxoplasmosis before becoming pregnant transmits the infection to her baby, because both she and the baby will have become immune to the infection. But toxoplasmosis could be reactivated, which means it could again affect a previously infected pregnant woman whose immune system was weakened. In general, it is much better to wait for a pregnancy until at least six months have passed after a toxoplasmosis infection.

Up to 90% of children born with congenital toxoplasmosis have no symptoms during initial breastfeeding, but a significant percentage of these children will show signs of infection several months or several years later. Premature and very young children show obvious signs of infection at birth or shortly thereafter.

Signs and symptoms, if they appear, include the following:

  • fever
  • swollen lymph nodes
  • jaundice (yellow or yellow skin and eyes) caused by an excessive concentration in the blood of a liver substance called bilirubin
  • abnormally large or small head
  • eruption
  • bruising or bleeding under the skin
  • anemia
  • enlarged spleen or liver

Some babies with congenital toxoplasmosis have abnormalities in the brain and nervous system that can cause:

  • seizures
  • sagging muscle
  • feeding difficulties
  • hearing losses
  • mental deficiency

These children are also at high risk for developing eye lesions that affect the retina (the photosensitive layer of the back of the eye responsible for vision) and cause serious visual problems.

If a child is born with congenital toxoplasmosis and is not treated during the stage of breastfeeding, he will almost always show some sign of this infection (often eye damage) in early childhood or adolescence.

Toxoplasmosis in healthy children

A healthy child who gets a toxoplasmosis infection may not have any symptoms of the infection, or just a few swollen lymph nodes, that:

  • they are usually those of the neck
  • can be touch sensitive
  • may increase and decrease in size over several months

Most children with these symptoms do not need any medical treatment unless the infection worsens.

Toxoplasmosis in children with weakened immune systems

Those children whose immune systems are weakened (for example, from suffering from AIDS, cancer or having received medication after an organ transplant) are more exposed to serious toxoplasmosis infections. Especially in children with AIDS, toxoplasmosis can attack the brain and nervous system, causing toxoplasmic encephalitis (an inflammation of the brain), whose symptoms include the following:

  • fever
  • seizures
  • headache
  • psychosis (a type of serious mental illness)
  • vision, speech, motor, or thinking problems

Although toxoplasmosis parasites can grow and multiply within a week after entering a person's body, the symptoms of the infection can take weeks or months to appear (if they appear).

Once a person gets a toxoplasmosis infection, the infection remains in their body for life, usually latent (or inactive) and without causing injuries or side effects. But the infection can be reactivated if the person suffers an immunosuppression due to an HIV infection or cancer treatment.

In a child whose immune system is healthy, mild symptoms of toxoplasmosis (swollen lymph nodes) usually subside within a few months, even if the child receives no treatment. But children with severe congenital toxoplasmosis may have permanent problems in the visual system and / or mental deficiency. And in those children whose immune system is weakened, toxoplasmosis can become deadly.


Unless the infected person has a weakened immune system or is pregnant, it is usually not necessary to treat them for suffering from a toxoplasmosis infection. Symptoms (such as swollen lymph nodes) usually disappear on their own in a few weeks or months. Anyway, a child should always see a doctor, because swollen lymph nodes can be a sign of other diseases.

If a pregnant woman gets a toxoplasmosis infection, her doctor and an infectious disease specialist will work together to develop her treatment program. Research indicates that treating the mother can help reduce the severity of the disease in the infant, although it does not always prevent the transmission of toxoplasmosis to the baby.

Children born with congenital toxoplasmosis are treated with different combinations of toxoplasmosis medications, usually throughout the first year of life. A specialist will decide which medications to use and for how long.

In older children who develop severe toxoplasmosis infections, treatment usually lasts 4 to 6 weeks (or a minimum of 2 weeks after the remission of symptoms). Children with weakened immune systems usually require hospitalization when they develop a toxoplasmosis, and those who suffer from AIDS may have to take toxoplasmosis medication for life.

When to call the doctor

Call your child's doctor immediately if he develops symptoms of toxoplasmosis and:

  • have been treated for AIDS or cancer
  • suffer from a condition that affects the immune system
  • have been taking medications that weaken the immune system

Also call the pediatrician if your child, who previously had good health, develops any of the symptoms of toxoplasmosis.

If you are pregnant, call your doctor immediately until it seems like you only have a swollen lymph node, especially if you have been in contact with cats or have eaten raw or undercooked meat.


If your family's cat lives indoors and has never been fed raw or undercooked meat, it is likely that it has a very low risk of contracting and spreading toxoplasmosis. However, it can also be contracted by eating raw meat or uncooked and contaminated food.

To help prevent toxoplasmosis in your family, follow these tips.

Food related tips

Wash your hands with soap and water after handling raw meat or unwashed vegetables or vegetables.

Wash all fruits, vegetables and vegetables before serving. You may also want to peel them.

Freeze the meat for several days before cooking, which, according to the CDC, helps reduce the chances of infection by toxoplasmosis.

Never wash raw chicken. Washing the meat and chicken when they are still raw can spread the germs through the kitchen. Germs are destroyed in cooking when the chicken reaches an internal temperature of 74 ° C (or 165 ° F). Therefore, washing does not help.

Thoroughly wash all cutting boards, all utensils and all kitchen surfaces (especially those that come in contact with raw meat) using hot water and soap after each use.

  • Cook all meats completely (their juices should be transparent and should not contain red or pink areas).
  • Tips related to cats

    If you are pregnant, have another person change the cat droppings drawer every day. Ask him to wash it with hot water and detergent and wash his hands afterwards. If you are responsible for changing the excrement drawer, wear gloves when you do so and wash your hands thoroughly next.

    Try that the cat is always inside the house so that it cannot get toxoplasmosis when it comes into contact with the earth or with the small infected animals that it tries to hunt and / or eat.

    In the event that your child has a sandbox outside, cover it, especially at night, to prevent the surrounding cats from using it to make their needs.

    Do not feed the family cat with raw meat.

    Stay away from stray cats.

  • Do not acquire a new cat if you or your partner is pregnant.
  • General advice and related to the domestic environment

    • Put on gloves for gardening and wash your hands well when finished.

    Use mosquito nets to try to prevent your house from containing bugs. Cat feces are one of the foods that most attract flies and cockroaches. And these insects can get feces, and also toxoplasmosis, to food.

  • Do not drink untreated water, especially if you travel to underdeveloped or developing countries.
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