Toxoplasmosis is a disease caused by the parasite Toxoplasma gondii, a microscopic organism that can infect most species of warm-blooded animals, including humans. The infection is widespread globally, though it often causes no symptoms in healthy individuals. While much attention focuses on the serious risks of infection acquired during pregnancy (congenital toxoplasmosis), the parasite can also be acquired by a baby after birth. This postnatal acquisition occurs through environmental exposure and is distinct from transmission across the placenta during gestation. Understanding the routes of postnatal infection, its signs, and management is important for parents and caregivers.
How Toxoplasmosis is Transmitted After Birth
Babies can, in fact, acquire toxoplasmosis after they are born. The primary route of postnatal acquisition is through the ingestion of the parasite’s infectious form, known as oocysts or tissue cysts. This oral exposure happens when an infant encounters and consumes contaminated materials from the environment.
The consumption of undercooked or raw meat (pork, lamb, and venison) is a major source of tissue cysts for older children and adults. Infants can be exposed if they consume solids or unpasteurized milk products. More commonly, transmission occurs through contact with soil or water contaminated by the feces of infected cats, the parasite’s definitive host. Oocysts shed by cats become infective in the environment after one to five days.
An infant’s tendency to put objects and hands into their mouth creates a risk for fecal-oral transmission from contaminated objects or surfaces. This includes playing with dirt or sand in areas where cat feces may be present. Rarely, transmission has been reported through infected blood transfusions or organ transplantation, though this is primarily a concern in immunocompromised patients.
Recognizing Symptoms of Acquired Infection in Infants
The signs of acquired toxoplasmosis in an infant can vary significantly. Unlike the severe, immediate symptoms associated with congenital infection, postnatal acquisition in a healthy infant is frequently asymptomatic or presents with very mild, non-specific symptoms.
When symptoms do appear, they typically resemble a mild flu-like illness. Parents might notice a persistent low-grade fever or general malaise. The most common noticeable sign is lymphadenopathy, which is the swelling of lymph nodes, particularly in the neck area.
In a small percentage of cases, the infection can cause more serious complications. The parasite can affect the eyes, leading to an inflammatory condition called retinochoroiditis, which can cause blurred or reduced vision. Although less common in acquired infection than in congenital cases, neurological involvement such as seizures or developmental delays can also occur in severe, untreated instances.
Medical Confirmation and Management
Medical confirmation of suspected postnatal toxoplasmosis requires specific laboratory testing to detect the parasite or the body’s immune response. Diagnosis relies on serological blood tests that measure Toxoplasma gondii-specific antibodies, specifically Immunoglobulin M (IgM) and Immunoglobulin G (IgG). The presence of IgM antibodies suggests a recent, acute infection.
Polymerase Chain Reaction (PCR) testing may also be performed on bodily fluids, such as cerebrospinal fluid or blood, to directly detect the parasite’s genetic material. Confirming postnatal acquisition versus a previously undetected congenital infection often requires a comparison of the infant’s antibody levels with the mother’s, and serial testing over time as maternal antibodies fade.
Treatment for symptomatic or severe acquired toxoplasmosis in infants involves a combination of antiparasitic medications. The standard regimen includes pyrimethamine and sulfadiazine. These potent drugs are often prescribed alongside folinic acid (leucovorin) to mitigate potential side effects, such as bone marrow suppression. Prompt treatment is important to prevent or limit long-term damage, and infants require ongoing follow-up, including regular eye examinations, to monitor for late-onset ocular complications.
Reducing the Risk of Postnatal Exposure
Caregivers can take several steps to minimize an infant’s risk of acquiring Toxoplasma gondii from the environment. Strict hand hygiene is the most effective preventive measure, as the parasite is primarily transmitted orally. Caregivers should wash their hands thoroughly after handling raw meat, gardening, changing diapers, or touching anything soiled outdoors.
Since contaminated soil is a major risk factor, infants should be prevented from playing in unsupervised areas where outdoor cats may defecate, such as sandboxes or garden beds. If an infant is old enough to eat solid foods, all produce should be washed thoroughly before preparation, and meats must be cooked to a safe internal temperature to destroy any potential tissue cysts.
For households with cats, management should focus on reducing the cat’s exposure and minimizing human contact with feces. Keeping cats indoors prevents them from hunting infected prey. The litter box should be changed daily, as oocysts only become infectious after about 24 hours. If possible, a non-caregiver should handle the litter box, or the caregiver should wear gloves and wash hands immediately afterward.