Toxoplasma gondii is a common parasitic organism frequently carried by domestic and feral cats that may cause infection in humans, known as toxoplasmosis. Individuals with compromised immunity, an existing chronic condition, and women who are pregnant are at the greatest risk for developing toxoplasmosis following exposure. Treatment for infection is dependent on the overall health of the individual and, in some cases, may necessitate lifelong drug therapy.
Known as T. gondii, this common, single-celled parasite is known to infect various animals, including birds. The feral or domesticated feline is this organism's preferred host, since it can only reproduce in cats. The toxoplasma gondii life cycle begins as soon as it enters the cat’s system, usually through the consumption of infected prey, such as a mouse. Other methods of transmission of toxoplasma gondii include the ingestion of contaminated or uncooked meat or infected dirt. Once introduced into the cat's system, the parasite digs into the feline’s intestinal wall where it forms oocysts, or reproductive cells.
In most cases, the oocysts remain fastened to the intestinal walls where they mature into infectious cells that eventually shed and are passed during stool elimination. Once passed, the matured cells survive for several months in soil or litter. When infected stool is passed outdoors, the cells contained in the fecal matter often survive to be ingested by another animal, at which time the process begins anew.
If a human becomes infected with toxoplasma gondii, the organism may directly affect the functionality of the individual’s brain and muscles. When a healthy individual becomes infected with the parasite, his or her immune system neutralizes the threat and the parasite falls dormant. The inactive organism remains present in the body for life, creating increased immunity in the event of future exposure. Though infection triggered by toxoplasma gondii may not be transmitted through interpersonal contact, there are other methods.
Individuals who consume contaminated meats or unpasteurized dairy products may become exposed to the parasitic organism. Receiving blood or organ donations from an infected individual may place the recipient at risk for toxoplasma gondii infection. Handling feline feces or litter without washing one’s hands afterward can also put an individual at risk for infection. Additional risk factors for parasite transmission include consuming fruits and vegetables that have not been properly washed and using contaminated cutting utensils and boards that have not been washed following the preparation of raw meat.
Those who have contracted toxoplasmosis may experience a variety of flu-like symptoms. The presence of body aches, fatigue, and fever may be indicative of the presence of infection. Additional symptoms may include headache, sore throat, and swollen lymph nodes. Individuals who possess compromised immunity due to chemotherapy, HIV/AIDS or other conditions that weaken immunity may develop more severe symptoms that may include impaired cognition, seizures, and respiratory difficulty. Pregnant women who contract toxoplasmosis may remain asymptomatic, meaning they exhibit no symptoms, but may pass the infection on to their unborn child.
Once the organism is introduced into the human body, the immune system immediately begins producing proteins, known as antibodies, in response. If infection is suspected, blood tests may be conducted to measure antibodies and confirm the presence of toxoplasma gondii. Pregnant women who think they may have been exposed to the parasite may undergo screening to check for the presence of infection in the absence of signs or symptoms. An ultrasound scan and amniocentesis may be conducted to determine whether active toxoplasmosis infection has been passed on to a fetus. Individuals who develop a severe reaction to infection, such as toxoplasmic encephalitis, may undergo magnetic resonance imaging (MRI) to evaluate the condition of his or her brain and check for the presence of cysts or lesions.
Healthy individuals generally require no treatment for toxoplasmosis. Those who develop symptoms associated with acute toxoplasmosis may require the administration of antibiotics and antimalarial drug therapy, which may trigger side effects that can include liver toxicity and the suppression of bone marrow. Individuals with weakened immunity may require lifelong toxoplasmosis therapy to eliminate infection and prevent recurrence.
Pregnant women may be given antibiotic medications to eliminate infection and reduce risks to their unborn child. Infants with congenital toxoplasmosis may be given antibiotic drug therapy to eliminate infection and reduce the risk for reinfection. Any damage that has occurred due to the presence of infection may be permanent.
Complications associated with toxoplasmosis generally occur in those with weakened immunity and may include infection recurrence and encephalitis. Individuals may reduce their chances for infection by regularly washing their hands, thoroughly washing fruits and vegetables and cooking all meats, and appropriately cleaning all food preparation surfaces. Additionally, hands should always be washed with soap and hot water after cleaning a litter box or handling feline feces.