Objective: To establish the prevalence and incidence of toxoplasmosis in an adult human immunodeficiency virus (HIV) population, and to determine if cat ownership contributes to the risk of toxoplasmosis.
Design: Retrospective record and laboratory review, coupled with a patient survey.
Setting: A tertiary-care military hospital HIV program.
Patients: A total of 723 HIV-infected adults, all former or current US military personnel.
Main outcome measures: Prevalence and incidence of serologic evidence of toxoplasmosis infection.
Results: A total of 723 HIV-infected patients had serial Toxoplasma IgG antibody determinations. Seventy patients (9.7%) were positive on their initial screen; the seronegative patients were tested annually for 1 to 5 years (mean duration of follow-up, 2.1 years). Only 13 patients (2.0%) who were initially seronegative acquired antibodies to Toxoplasma gondii. None of the patients who seroconverted developed clinical disease. A pet history was available on 12 of 13 patients who seroconverted; only one (8.3%) had owned or lived in a household with a cat during the period of seroconversion. The calculated attributable risk of cat ownership/exposure for toxoplasmosis seroconversion in this population is -2.9 per 100 persons annually.
Conclusion: Toxoplasma antibody seroconversion in an adult HIV-infected population is unusual and appears unrelated to cat ownership or exposure.