What is Congenital Toxoplasmosis?
Toxoplasmosis is a kind of parasitic infection that can affect both humans and animals. In healthy adults with a strong immune system, it often doesn’t show any symptoms about half the time. However, it can also lead to a mild, short-term sickness with nonspecific symptoms like fever, feeling unwell, a rash, headache, fatigue, and swollen tender lymph nodes. For those with weakened immune systems and newborn babies, toxoplasmosis can result in a severe infection with serious consequences. If a pregnant woman is infected, she may pass the parasite to her baby (known as congenital toxoplasmosis), which can result in significant health problems and even death in fetuses, newborns, and children as they grow. Because toxoplasmosis often doesn’t show symptoms, it’s important to be proactive in detecting the infection. A blood test can easily confirm a diagnosis.
What Causes Congenital Toxoplasmosis?
Congenital toxoplasmosis is a condition caused by a parasite named Toxoplasma gondii, that gets into the body and lives within cells.
Looking at its life cycle, this parasite has cats as its main hosts, but it can affect a variety of other animals as well. In cats, it goes through two cycles – one inside the intestine and one outside of it. Other animals only experience the cycle outside the intestine. The parasite’s life cycle contains three infectious stages: the tachyzoite, the bradyzoite, and the oocysts or sporozoites. The tachyzoite and bradyzoite stages multiply slowly and fast in the host’s tissues, especially in the brain and muscle. Oocysts are formed in the cat’s intestine from the sexual cycle of the parasite. Cats catch the parasite by eating other animals infected with bradyzoites or by consuming contaminated soil or water that contains oocysts.
In the early days of infection, cats can excrete millions of oocysts in their feces over a week or two. These oocysts can grow in damp environments and pollute the soil, grass, and garden veggies. If cat litter is disposed of regularly, within a day or two, the risk of infection is reduced. Other animals like humans, sheep, cattle, birds, pigs, and mice can become infected at this stage. Over time, the oocysts change into tachyzoites, which are characteristic of early infection. The change into oocysts only happens in cats. In other animals, they develop into cysts, known as bradyzoites, which cause latent infection and can stay lifelong in the brain, heart, skeletal muscle, and some other organs.
The ways of transmission in pregnant women include eating undercooked meat or food or water contaminated with oocysts, or if they have a severely weakened immune system due to something like a human immunodeficiency virus infection. The parasites can be transferred via the placenta to the growing fetus. The infection takes about 4 to 21 days to show up. The exact time of transmission isn’t well known. How severe the effects are on a fetus or newborn depends on when the infection happened during the pregnancy, how much of the parasite is present, how virulent the infecting strain is, and the state of the mother’s immune system.
Risk Factors and Frequency for Congenital Toxoplasmosis
In the United States, more than 40 million people carry the toxoplasma parasite. Most of them don’t show any symptoms. This issue is quite common globally too, and over 60% of people in some parts of the world are infected with toxoplasma. The rate of people who have this parasite can vary from place to place, and it’s especially common in tropical areas. This infection is considered the most widespread parasite-related infection among humans.
- The number of people with this parasite tends to increase as they age, regardless of where they live.
- The rate of infection is higher in hot, humid areas and lower altitudes because the parasite grows and survives well in these conditions.
- The rate of babies born with toxoplasmosis depends on when the mother got the infection during her pregnancy and whether or not she had been previously infected before exposure.
- Among the infections that can be passed from mother to baby during pregnancy, only congenital cytomegalovirus (a common virus that can infect people of all ages) is more common than toxoplasmosis.
- In the United States, between 1 in 3,000 and 1 in 10,000 live-born babies are affected by toxoplasmosis.
Signs and Symptoms of Congenital Toxoplasmosis
Congenital toxoplasmosis is a medical condition that can present in different ways in newborns. Some babies might show no symptoms at birth, but others may have severe neurological and eye-related problems. Surprisingly, about 75% of babies with this condition don’t show any clear signs when they are born. The condition is usually discovered during routine newborn and maternal checks done in some countries. It can cause neurological issues like brain calcifications or eye problems such as retinal scars. In a few cases, it can even cause miscarriages, premature births, or stillbirths.
Full-term newborns, when affected, usually have milder symptoms which could include an enlarged liver and spleen, and swollen lymph nodes. On the other hand, preterm newborns can have severe symptoms. However, only a small number of infected newborns show the classic signs of congenital toxoplasmosis which include inflammation of the back of the eye, water on the brain (hydrocephalus), and brain calcifications. These symptoms are mostly seen and quite severe in babies whose mothers got infected during the first three months of pregnancy and did not receive any treatment. In some severe scenarios, babies may pass away in the womb or shortly after birth.
The severe form of this disease may show the following signs and symptoms:
- Neurological problems, such as an unusually small or large head, seizures, uncontrolled eye movements, hydrocephalus, brain calcifications, inflammation of the brain and spinal cord
- Eye problems, such as inflammation of the back of the eye, small eyes, inflammation of the retina and choroid of the eye, misalignment of the eyes
- Being small for their gestational age
- Enlarged liver and spleen
- Generalized swollen lymph nodes
- Yellow skin and eyes (jaundice)
- Low platelet count, anemia, and purplish spots on the skin (petechiae)
- Spots on the skin that are flat or slightly raised (maculopapular rash)
In addition, babies with a mild or unnoticed infection are at risk for later complications, which may include:
- Repeated inflammation of the back of the eye, potentially leading to loss of vision
- Delays in motor skills development
- Learning disorders
- Intellectual disability
- Loss of hearing
- Endocrine abnormalities due to disruption of the hypothalamus and pituitary gland
Currently, only Massachusetts and New Hampshire carry out newborn screening for congenital toxoplasmosis.
Testing for Congenital Toxoplasmosis
When there’s a chance that a baby could have congenital toxoplasmosis – a disease passed from an infected mother to baby during pregnancy – certain tests can be taken to confirm or rule it out. This might be when the mother is confirmed to have an infection, or if specific symptoms such as changes in brain structure, are spotted on a prenatal ultrasound scan.
A test that looks for T. gondii (the parasite responsible for toxoplasmosis) DNA in the amniotic fluid surrounding the baby can confirm the diagnosis. After birth, a baby should be tested for this condition in a few specific situations. These include if the mother got a toxoplasmosis infection for the first time while she was pregnant, if the mother has a weakened immune system and a prior toxoplasmosis infection, if the baby has symptoms potentially pointing to congenital toxoplasmosis, or if toxoplasma is detected during newborn screening examinations.
There are also several blood tests which can help in diagnosing this condition. Doctors would look for antibodies, which are proteins the immune system uses to attack foreign substances like the T. gondii parasite. The antibodies you’d test for in cases of suspected toxoplasmosis are called immunoglobulin G (IgG) , immunoglobulin M (IgM), and immunoglobulin A (IgA). If there are concerns about false positives – when a test incorrectly indicates the presence of a disease – it’s wise to re-test 10 days after birth. It’s also possible to look for T. gondii DNA in samples of the baby’s cerebrospinal fluid, urine, or peripheral blood.
Confirmed infection is typically based on one or more of the following tests: toxoplasma-specific IgM or IgA antibodies appearing 10 days after birth, ongoing or increasing levels of IgG without treatment in infants one year or older, or T. gondii DNA or specific toxoplasma antibodies found in the cerebrospinal fluid.
Keep in mind that even if the IgM and IgA tests come back negative, the baby could still have the infection. Sometimes, if the mother gets infected late during her pregnancy, there may be a delay in the baby’s production of antibodies. In these cases, it’s recommended to repeat the antibody tests every 2 to 4 weeks up until the baby is at least 3 months old.
Interpreting these test results can be complicated, so it helps to send them to a dedicated toxoplasmosis laboratory for analysis. Two notable labs in the United States for this include the National Reference Laboratory for Toxoplasmosis and the Toxoplasmosis Center in Chicago.
Additionally, imaging of the head via ultrasound scan or computed tomography (CT) scan can provide further information by looking for specific abnormalities such as changes in brain structure. Other tests may indicate high protein levels in the cerebrospinal fluid and a slight increase in specific white blood cells. Blood tests could show low levels of red blood cells or platelets, and tests checking the liver and kidneys could also inform whether other organs are affected by the disease.
Treatment Options for Congenital Toxoplasmosis
Despite more than a century of research on the parasite T. gondii, scientists have not yet agreed on a standard treatment plan for congenital toxoplasmosis, which is passed from infected mother to child during pregnancy. Various opinions circulate about which drug combinations and duration of treatment are most effective.
One of the challenges is that most medications only act against T. gondii when it’s actively dividing in a form called tachyzoites and not when it’s in a dormant cyst-like form known as bradyzoites. The most common treatment plan for babies born with the infection involves a combination of several drugs: pyrimethamine, a sulphonamide class drug (either sulphadiazine or sulphadoxine), and folinic acid, given for 1 year. Babies with more severe infection, indicated by symptoms like multiple brain calcifications or eye abnormalities, often receive higher doses and treatment for up to 2 years.
Newer drugs, including azithromycin and atovaquone, are also effective against T. gondii, but we need more research to find out how well they work. When toxoplasmosis is identified in an expectant mother, she should be treated immediately before giving birth, usually with a drug called spiramycin, to prevent the infection from passing to her baby.
Babies who test positive for the infection but aren’t showing symptoms usually receive treatment for 3 months. Some doctors recommend adding steroids to the treatment plan if the baby has high protein levels in spinal fluid or severe eye inflammation that hurts vision. Steroids continue until these signs have cleared up. These babies need regular check-ups to monitor their development and to spot any late effects of the infection.
Long-term treatment can have side effects, including suppressed bone marrow activity leading to fewer white blood cells, kidney problems, and allergic reactions. So these infants need regular blood tests and occasional liver and kidney function tests to ensure there’s no adverse impact from the treatment.
What else can Congenital Toxoplasmosis be?
When a baby is born with toxoplasmosis, it’s crucial to distinguish this condition from other infections that they might have been born with. These could include:
- Cytomegalovirus (CMV)
- Rubella
- Lymphocytic choriomeningitis virus, a type of illness that can cause complications in the nervous system
- Varicella, also known as chickenpox
- Herpes simplex virus
These other infections can sometimes have similar symptoms, so it’s important to perform the right tests to make sure that the baby receives the correct treatment.
What to expect with Congenital Toxoplasmosis
Treating toxoplasmosis during pregnancy can minimize the risk of severe symptoms and long-term neurological effects. Without treatment, toxoplasmosis can have serious implications, including vision problems, neurological issues, and severe developmental delays.
We still need more research to understand the outcomes in patients who receive treatment. However, some studies show that starting treatment early can greatly improve eye-related problems caused by the disease. Despite this, patients need to be closely monitored by eye doctors until their early adulthood.
Higher gestational age, which is the duration of pregnancy, is usually associated with better results.
Possible Complications When Diagnosed with Congenital Toxoplasmosis
Untreated congenital toxoplasmosis, a disease passed from an infected mother to her child during pregnancy, can lead to serious complications:
- Loss of vision
- Deafness
- Intellectual disability
- Severe developmental delays
