Toxoplasmosis is caused by the sporozoan parasite Toxoplasma gondii and is a severe, generalized, granulomatous CNS disease. It may be either congenital or acquired and is found in humans, domestic animals (e.g., cats), and wild animals. Humans may acquire the infection through ingestion of inadequately cooked meat or other contaminated material. Congenital toxoplasmosis may cause fetal death. Symptoms of subacute infection may appear shortly after birth or much later. Complications of congenital toxoplasmosis include hydrocephaly, microcephaly, convulsions, and chronic retinitis. It is believed that one fourth to one half of the adult population is infected with no symptoms with toxoplasmosis. The CDC recommends serologic testing during pregnancy.

The IFA test helps to differentiate toxoplasmosis from IM. Toxoplasma antibodies appear within 1–2 weeks of infection and peak at 6–8 months. IFA is also a valuable screening test for latent toxoplasmosis.

• Titer <1:16: no previous infection (except for ocular infection) by IFA

• Negative by MEIA

• Negative: T. gondii DNA not detected by PCR

1. Collect a 7-mL blood serum sample in a red-topped tube. Observe standard precautions.

2. Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.

The IFA test is considered positive under any of the following conditions:

1. Titer ≥1:256 indicates recent exposure or current infection; rising titer is of greatest significance.

2. Any titer value is significant in a newborn infant.

3. Titer ≥1:1024 is significant for active disease.

4. Titer ≤1:16 occurs with ocular toxoplasmosis.

Pretest Patient Care

1. Explain test purpose and procedure.

2. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.