Introduction
Toxoplasmosis is a common infection caused by the parasite Toxoplasma gondii. The parasite is found in cat feces and contaminated food or objects. While toxoplasmosis is usually harmless in healthy adults, it can cause serious complications when a woman becomes infected for the first time during pregnancy. The parasite can be passed to the developing fetus through the placenta and cause birth defects or miscarriage (CDC). That’s why pregnant women are advised to take precautions to avoid contracting toxoplasmosis while pregnant.
What is Toxoplasmosis?
Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii (T. gondii). This microscopic parasite can infect most warm-blooded animals, but cats are the only known definitive host where the parasite can complete its life cycle (CDC, https://www.cdc.gov/parasites/toxoplasmosis/index.html).
T. gondii spreads to humans and other animals primarily through contact with infected cat feces. Cats excrete T. gondii eggs, called oocysts, in their feces. These oocysts can survive in the environment for over a year and are the primary source of toxoplasmosis infection (Mayo Clinic, https://www.mayoclinic.org/diseases-conditions/toxoplasmosis/symptoms-causes/syc-20356249).
When humans inadvertently ingest T. gondii oocysts, through contaminated food, water or soil, they can develop toxoplasmosis. The parasite can also be contracted through consuming raw or undercooked meat containing T. gondii tissue cysts.
Symptoms
Many people who are infected with toxoplasmosis don’t have any symptoms at all. When symptoms do occur, they are often similar to those of a mild flu, including swollen lymph nodes, muscle aches, headache, and fever (Mayo Clinic, https://www.mayoclinic.org/diseases-conditions/toxoplasmosis/symptoms-causes/syc-20356249). Lymph nodes may become swollen or enlarged, especially around the neck. Other general symptoms can include fatigue, sore throat, and body aches (Better Health Channel, https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/toxoplasmosis).
In rare cases, a more severe infection may cause blurred vision, confusion, loss of coordination, eye inflammation, lung problems like pneumonitis, or rarely inflammation of the heart muscle. However, most healthy adults who acquire toxoplasmosis experience either no symptoms or very mild symptoms that are not unlike a flu infection.
Effects on Fetus
If a pregnant woman contracts a Toxoplasma infection, the parasite can cross the placenta and spread to the fetus. This can cause serious birth defects and complications (CDC, Chaudhry 2014).
Some of the potential effects on the fetus include:
- Eye damage such as retinochoroiditis, which can lead to blindness
- Hearing loss
- Hydrocephalus (fluid buildup in the brain)
- Intracranial calcification (calcium deposits in brain tissue)
- Cognitive or mental disability
The earlier in pregnancy the transmission occurs, the more severe the effects on the fetus may be. Fortunately, congenital toxoplasmosis is relatively rare, occurring in less than 1% of exposed infants (Chaudhry 2014). But because the consequences can be devastating, preventing infection is critical for pregnant women.
Testing
There are two main ways to test for toxoplasmosis during pregnancy:
- Blood test for antibodies – A blood sample from the mother can be analyzed to look for antibodies against toxoplasmosis. This can determine if she has been infected recently or in the past. According to Toxoplasmosis Testing, immunoglobulin M (IgM) antibodies appear early in an infection while immunoglobulin G (IgG) antibodies remain long-term.
- Amniocentesis to test fetus – If the mother has evidence of an acute infection, amniotic fluid may be sampled by amniocentesis to test for toxoplasmosis directly in the fetus. As stated by Toxoplasmosis in pregnancy: prevention, screening, and treatment, this invasive procedure carries a small risk of complications.
These tests can determine if the mother acquired toxoplasmosis during pregnancy and if the fetus has been infected. This information guides treatment decisions to reduce transmission and severity.
Prevention
There are several key ways pregnant women can prevent toxoplasmosis infection:
- Avoid changing cat litter if at all possible. Have someone else change the litter daily. If no one else can do it, wear disposable gloves and wash hands thoroughly afterward. The parasite is found in cat feces that can be present in litter.
- Cook meat thoroughly. Meat should be cooked to a safe minimum internal temperature of 145°F to kill any parasites. Freeze meat for 24-48 hours before cooking to further reduce risk. Avoid tasting meat before it is fully cooked.
- Wash hands after handling raw meat. Scrub hands thoroughly with soap and water to remove any traces of contaminated fluid or juice from raw meat.
- Wash hands after gardening or handling soil. The parasite can live in contaminated soil and may be transferred to hands.
- Wash all fruits and vegetables thoroughly before eating.
- Avoid drinking unpasteurized milk or untreated water.
Being diligent about handwashing, thoroughly cooking meats, and avoiding contact with potential sources of infection are the best ways for pregnant women to prevent toxoplasmosis.
Treatment
If a pregnant woman is diagnosed with a Toxoplasma infection, antibiotic treatment will be prescribed to try to reduce the risk of transmitting the infection to the fetus. According to the CDC, medications such as spiramycin, pyrimethamine/sulfadiazine, and trimethoprim-sulfamethoxazole can help treat toxoplasmosis infections during pregnancy. These antibiotics do not treat an established infection in the fetus but may help reduce the risk of transmission if given early in the pregnancy (Peyron, 1999).
Along with medication, regular obstetric care and monitoring is crucial during and after pregnancy for women diagnosed with toxoplasmosis. This includes ultrasounds, amniocentesis, and fetal blood sampling to check for signs of infection in the fetus. Newborns may also need additional testing and treatment after birth if congenital toxoplasmosis is detected (CDC, 2022). Close medical supervision and prompt treatment when an infection is found gives the best chance of having a healthy baby.
Peyron, F. (1999). Treatments for toxoplasmosis in pregnancy. Clinical Microbiology and Infection, 5(9), 526-531. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8406945/
Centers for Disease Control and Prevention. (2022, January 10). Toxoplasmosis – General Information – Pregnant Women. https://www.cdc.gov/parasites/toxoplasmosis/gen_info/pregnant.html
After Pregnancy
If a woman contracts toxoplasmosis during pregnancy, the good news is that she will have immunity against future infections going forward (CDC). This means that after she gives birth, it is safe for her to be around cats again without concern about contracting toxoplasmosis. The antibodies developed from the initial infection will protect both mother and baby from reinfection.
Therefore, once the baby is born, the mother does not need to take any special precautions around cats. It is perfectly safe for her to change litter boxes, clean cat waste, or have cats as pets without risk of contracting toxoplasmosis again. The CDC affirms that previous infection confers immunity against future infection. So women infected during pregnancy can relax about toxoplasmosis risks after giving birth.
Cats vs Litter
While cats can spread toxoplasmosis, the main risk comes from exposure to contaminated feces in litter boxes, not from petting or being around cats. According to the CDC, cats only shed the toxoplasma parasite in their feces for 1-2 weeks after initial infection. After this short period, cats are not likely to continue shedding toxoplasma organisms. Therefore, the risk lies in cleaning litter boxes where infected feces may be present.
Cats who hunt or eat raw meat are more likely to acquire toxoplasmosis and shed the parasite than indoor-only cats eating commercial cat food. Kittens and young cats have the highest chance of shedding the toxoplasma parasite after first exposure. In general, mature cats are less likely to actively shed toxoplasma if they were exposed as kittens. Still, pregnant women should avoid cleaning litter boxes, since there is no way to know for sure if a cat is shedding toxoplasma.
Conclusion
Toxoplasmosis is a disease caused by the Toxoplasma gondii parasite that can be contracted by pregnant women from handling contaminated cat litter. While toxoplasmosis often has no symptoms in healthy adults, it can cause serious complications when contracted during pregnancy, including miscarriage, stillbirth, and birth defects. The main points to remember are:
- Cats are the primary host of T. gondii and spread the parasite through their feces
- Pregnant women should avoid cleaning cat litter boxes to prevent exposure
- Other potential sources of toxoplasmosis include eating undercooked meat and unwashed fruits and vegetables
- If exposed during pregnancy, antibiotics can help reduce transmission to the fetus
- All pregnant women should be tested for toxoplasmosis and monitored throughout pregnancy if infected
- Simple precautions can protect pregnant women and their babies from this preventable disease
While contracting toxoplasmosis from cats is not extremely common, pregnant women are at higher risk of complications. Avoiding cat litter and taking other basic precautions can help ensure a healthy pregnancy.