What is Toxoplasmosis?
Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii (CDC). This single-celled parasite can infect most mammals and birds. It is found worldwide and is one of the most common parasitic infections.
In humans, toxoplasmosis often causes mild flu-like symptoms like swollen lymph nodes and muscle aches. For most healthy people, the infection goes away on its own. However, the parasite remains dormant in body tissues and can reactivate. (Mayo Clinic)
Toxoplasmosis is more dangerous for those with weakened immune systems, such as people with AIDS. It can also cause serious birth defects if a woman becomes infected while pregnant. For these groups, toxoplasmosis needs to be treated right away.
How is Toxoplasmosis Spread?
Toxoplasmosis is primarily spread through infected cat feces. Cats get infected by eating infected rodents, birds, or other small animals. Cats only shed the parasite in their feces for 1-3 weeks after initial infection, according to the CDC https://www.cdc.gov/parasites/toxoplasmosis/epi.html. The parasite doesn’t become infectious until 1-5 days after being shed. Humans can become infected through inadvertent ingestion of infected cat feces, either through poor hygiene after emptying the litter box or ingesting contaminated soil, water or food.
Another way toxoplasmosis spreads is by eating undercooked infected meat. Any meat that is contaminated can harbor Toxoplasma, including pork, lamb and venison. Proper cooking and freezing techniques can kill any parasites in meat before consumption.
Finally, toxoplasmosis can spread from a mother to her fetus during pregnancy if the mother becomes infected for the first time while pregnant. This can lead to miscarriage, stillbirth or potentially severe illness in the newborn. For this reason, pregnant women are advised against changing cat litter and should take care to avoid undercooked meat.
Only Some Cat Poop Contains Toxoplasmosis
While the parasite that causes toxoplasmosis, Toxoplasma gondii, is relatively common in cats, only a small percentage of cats actively shed infectious oocysts in their feces at any given time. Cats typically only shed oocysts for approximately 1-3 weeks after being initially infected (https://www.wormsandgermsblog.com/files/2008/04/M4-Toxoplasma-Owners.pdf). After this brief period, most cats will develop immunity and no longer shed oocysts.
Indoor cats are much less likely to be infected with T. gondii compared to outdoor cats or feral cats. One study found the prevalence in pet cats kept exclusively indoors to be only 1.5%, compared to 11.5% in semi-domesticated cats with outdoor access (https://bmcvetres.biomedcentral.com/articles/10.1186/s12917-021-02965-z). This is because indoor cats are not exposed to many potential sources of infection like hunting or contaminated soil.
Additionally, even if a cat is actively shedding oocysts, they do not immediately become infectious. Oocysts require 1-5 days after being shed to sporulate and become infectious (https://www.wormsandgermsblog.com/files/2008/04/M4-Toxoplasma-Owners.pdf). So fresh feces from an infected cat pose little risk.
Reducing Risk of Exposure
There are several ways to reduce your risk of being exposed to toxoplasmosis when handling cat litter or gardening:
- Wash your hands thoroughly with soap and warm water after touching cat litter, soil, or raw meat. This removes any oocysts that may be present. According to the CDC, handwashing can help prevent transmission. (CDC)
- Keep cats indoors and feed them commercial dry or canned food to prevent them from hunting birds and rodents that may carry the parasite. Stray and outdoor cats have a higher risk of infection. (CDC)
- Thoroughly wash fruits and vegetables, especially if eaten raw, since they may have contacted contaminated soil. (Mayo Clinic)
- Cook meat thoroughly to temperatures high enough to kill any parasites present. Undercooked meat poses a high risk. (CDC)
Taking simple precautions like these can greatly reduce your chances of contracting toxoplasmosis from cats or contaminated food and environments.
Who is Most at Risk?
According to the CDC, certain groups of people are at an increased risk for toxoplasmosis infection https://www.cdc.gov/parasites/toxoplasmosis/epi.html:
Pregnant women – If a woman becomes infected with toxoplasmosis for the first time during or just before pregnancy, she can transmit the infection to her unborn child through the placenta. This can lead to miscarriage or severe illness in the newborn.
Those with weakened immune systems – People with weakened immune systems, such as those with HIV/AIDS, cancer, or who are receiving immunosuppressant medications, are more susceptible to severe toxoplasmosis infection. The parasite can cause damage to the brain and other organs.
Fetuses infected through the placenta – If a pregnant woman becomes infected, the parasite may be transmitted through the placenta to the fetus. This congenital toxoplasmosis can cause severe illness in the newborn, including eye damage, hearing loss, and developmental delays.
Symptoms in Humans
Most cases of toxoplasmosis in healthy individuals are mild and often show no symptoms at all. In the cases where symptoms do manifest, they are usually flu-like [https://www.mayoclinic.org/diseases-conditions/toxoplasmosis/symptoms-causes/syc-20356249]. Common symptoms of toxoplasmosis include:
- Swollen lymph nodes, especially in the neck
- Muscle aches and pains throughout the body
- Fatigue and overall feeling of malaise
- Fever and chills
- Headache
Rarely, some individuals may experience more severe symptoms such as blurred vision, confusion, and loss of coordination. These require prompt medical attention [https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/toxoplasmosis].
In most healthy people, symptoms of an initial toxoplasmosis infection typically last for 1-2 weeks before improving on their own as the immune system fights off the infection. However, the parasite cysts can remain dormant in tissue for life.
Diagnosing Toxoplasmosis
Toxoplasmosis is typically diagnosed through blood tests that detect antibodies produced by the immune system in response to the infection. The main blood tests used are:
- IgG antibody test – detects whether a person has ever been infected with toxoplasmosis
- IgM antibody test – detects whether a person has an active infection, as IgM antibodies are produced early in infection
- IgA antibody test – can help determine if an infection was acquired recently
These antibody tests are the primary method for diagnosing toxoplasmosis (1). If an active infection is suspected, polymerase chain reaction (PCR) testing may also be done to detect Toxoplasma gondii DNA in the blood, which confirms an active infection. PCR can also be performed on amniotic fluid to check for congenital toxoplasmosis in a fetus (2).
Sources:
(1) https://www.cdc.gov/parasites/toxoplasmosis/diagnosis.html
(2) https://www.mayoclinic.org/diseases-conditions/toxoplasmosis/diagnosis-treatment/drc-20356255
Dangers to Pregnant Women
Toxoplasmosis can pose serious risks for pregnant women and their unborn babies. According to the Centers for Disease Control and Prevention, toxoplasmosis is considered one of the TORCH infections, a group of infections that can cause severe illness in a fetus or newborn
If a pregnant woman becomes infected with toxoplasmosis for the first time during or just before pregnancy, the parasite can be transmitted to the developing baby. This congenital toxoplasmosis can cause the following risks:
- Miscarriage
- Stillbirth
- Premature delivery
- Birth defects, such as eye and brain damage, that can result in vision loss or intellectual disabilities (CDC)
The earlier in pregnancy the transmission occurs, the higher the likelihood of serious effects. Thankfully, congenital toxoplasmosis is relatively rare, affecting only about 1 infant per 10,000 live births in the United States (March of Dimes).
If a woman has been infected with toxoplasmosis prior to pregnancy, the dormant parasite is unlikely to be transmitted to the fetus. However, a prior infection could reactivate during pregnancy, so doctors still recommend precautions.
Treatment Options
The most common treatment for toxoplasmosis involves a combination of anti-parasitic medicines and antibiotics like pyrimethamine and sulfadiazine: https://www.cdc.gov/parasites/toxoplasmosis/treatment.html
Pyrimethamine (Daraprim) and sulfadiazine stop the growth of T. gondii parasites, while folinic acid helps reduce side effects. This combination is usually prescribed for 4-6 weeks, depending on the type of infection.
If a pregnant woman becomes infected, it is crucial to seek prompt treatment. This may significantly lower the risk of passing the infection to her baby. Pyrimethamine, sulfadiazine, and folinic acid are considered safe in pregnancy. Treatment can continue for the remainder of the pregnancy.
People with weakened immune systems may need to take pyrimethamine and sulfadiazine for an extended time to prevent the infection from reactivating. Lifelong treatment may be required in some AIDS patients or transplant recipients.
Prevention Tips
There are several ways to help prevent toxoplasmosis infection:
Cook meat thoroughly to an internal temperature high enough to kill any Toxoplasma parasites that may be present. According to the CDC, freeze meat for several days at subzero temperatures before cooking to greatly reduce any parasites (Toxoplasmosis: General FAQs). Use a food thermometer to ensure meat reaches safe internal temperatures.
Wash hands thoroughly with soap and warm water after touching raw meat, gardening or playing in the dirt, cleaning a litterbox, or touching anything that could be contaminated. According to the Minnesota Department of Health, toxoplasmosis can be killed by thorough handwashing (Preventing Toxoplasmosis – MN Dept. of Health).
Wash fruits and vegetables thoroughly before eating them raw. Peeling them adds an extra layer of protection.
Clean litter boxes daily to remove feces before the parasite has time to sporulate and become infectious. Wear gloves while cleaning litter boxes and wash hands afterwards.
Keep cats indoors to prevent them from eating infected prey or coming into contact with other cats’ feces. An indoor cat is unlikely to be a source of toxoplasmosis.