Cats and toxoplasmosis risk in HIV-infected adults.

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.