Discovered in 1908, toxoplasmosis is an intracellular parasitic infection caused by the protozoan known as toxoplasma gondii. It infects multiple of warm-blooded including humans, livestock, birds etc., however, cats are the definitive hosts to toxoplasma gondii. This means that the parasite is only able to sexually reproduce in cats (both wild and domesticated).Most people have heard of toxoplasmosis due to the risks infections pose to pregnant women. If infection occurs during pregnancy it can cause abortion and congenital defects to the fetus. Toxoplasmosis infection in humans is extremely common and approximately 30 – 50% of the population have been exposed to it. 
What are the symptoms of toxoplasmosis?
Most healthy adults are asymptomatic, that is they don’t have any symptoms, others have only mild symptoms such as:
Enlarged lymph nodes
Flu like symptoms
Muscle aches and pains
Severe toxoplasmosis in humans can sometimes occur and cause damage to the eyes, brain, and other organs. This is more likely to happen in immunocompromised individuals such as people with HIV, organ transplant recipients and patients undergoing some forms of chemotherapy.
How is toxoplasmosis diagnosed?
Toxoplasmosis is diagnosed by a blood test to check for antibodies IgG and IgM.
How is toxoplasmosis treated?
If a pregnant woman is diagnosed with toxoplasmosis, she will be treated with antibiotics to help prevent transmission to the fetus. The earlier treatment starts the better.
If upon testing the fetus is shown to be infected also, you may be treated with two antibiotics.
How do I know if my fetus has been infected?
Amniocentesis – Testing of amniotic fluid.
Cordocentesis – Testing of blood from the umbilical cord.
Fetal ultrasound may be able to detect fetal abnormalities caused by the infection.
How does the fetus become infected and what effect does it have?
Fetal infection occurs via the placental transmission. The earlier in the pregnancy, the lesser chance of transmission, but the effects are more severe. The later in the pregnancy, the greater chance of transmission, but the effects are less severe.  When a fetus becomes infected in the uterus it is known as ‘congenital toxoplasmosis’. Not all women who become infected will pass it on to their fetus.
Symptoms may be overt, that is they are visible at birth and include
Low birth weight
Chorioretinitis (inflammation of the choroid and retina of the eye)
Swollen lymph nodes
Hepatosplenomegaly (enlarged liver and spleen)
Hydrocephalus (accumulation of cerebrospinal fluid in the ventricles of the brain)
Many infants display no symptoms at birth (subclinical infection) but may develop disabilities later in life. This includes:
Blindness or visual impairment
Infants with congenital toxoplasmosis should be treated for the first year with antibiotics and carefully monitored past infancy.
How can I avoid becoming infected?
Cats aren’t the only source of infection to humans. They can also become infected via improperly cooked meat, improperly washed vegetables, drinking untreated water (from a stream or river for example) and gardening.
Avoid cleaning the litter trays, if this is not possible wear gloves and a mask.
Ensure litter trays are scooped at least once a day.
Ensure your meat is cooked thoroughly. This means it is no longer pink in the middle, the juices run clear and it has been cooked at 160F.
Wash your hands after handling animals.
Wear gloves in while gardening.
Wash fruit and vegetables thoroughly before eating.
Wash your hands after handling raw meat, fruit and vegetables.
Wash your hands before eating.
Don’t let your cat(s) hunt.
Cover sandboxes to prevent cats defecating in them.
Don’t drink unpasteurised milk.
Thoroughly cleaning chopping boards and utensils. Use separate boards for fruit/vegetables and meat.
Keep the litter tray away from the kitchen and other eating areas.
Should a pregnant woman rehome her cat?
No, this isn’t necessary. If you have a cat and become pregnant it is strongly recommended that you speak to your doctor, midwife or obstetrician about this, they may recommend a blood test which will check for antibodies to toxoplasmosis. If you have antibodies, you have been exposed to toxoplasma gondii at some stage in your life. This means your immune system has already built up a resistance, therefore, you are very unlikely to become re-infected. My own obstetrician tested me multiple times during my two pregnancies as I was negative and he wanted to ensure I remained negative.
What else can I do to avoid toxoplasmosis?
If you are planning to become pregnant, it is recommended you speak to your doctor and request to be tested to see if you have been exposed to toxoplasmosis. If you are pregnant and think you may have possibly been exposed to toxoplasmosis, seek medical advice immediately.
 Cornell University College of Veterinary Medicine