Serological study of Toxoplasma gondii in kidney recipients.

Toxoplasma gondii IgG antibodies were determined in 200 kidney recipients by the Sabin-Felmand dye test. Twenty-two (11%) cases were positive for antibody detection. There was a statistically significant difference in the history of taking under-cooked meat, between the number of sero-positive cases and that of sero-negative subjects (63.6% vs 28.8%, p = 0.02). No such significant difference was evident regarding cat ownership (13.6% vs 22.0%, p = 0.3). Sixteen (72.6%) of the 22 subjects with positive Tgondii antibody had undergone kidney transplantation less than one year ago during which a high dose of immunosuppressive drugs were prescribed. The remaining six (27.3%) cases had had transplantation more than one year ago and were on a lower dosage of immunosuprresants. Toxoplasma reactivation seemed to be higher in the former group, which should thus be closely followed-up. Preventive chemoprophylaxis should be considered if there is any indication of toxoplasma reactivation. Since there have been occasional reports of donor-to-host transmission of toxoplasmosis in kidney transplant recipients, serological screening of toxoplasma antibody in kidney donors is advisable. Potential donors with positive toxoplasma antibody should be rejected; but if that is unavoidable, 6-week prophylactic treatment of primary infection in kidney recipients should be administered.

Predictive value of latex agglutination test in serological screening for Toxoplasma gondii.

The predictive value of commercial latex agglutination kit (Toxo-Screen DA, bioMerieux) was assessed for use as screening test for Toxoplasma IgG antibody. The sensivity and specificity were also compared with those of the reference standard Sabin-Feldman dye test. Five hundred serum samples were collected from 200 blood donors and 100 each from pregnant women, kidney recipients and HIV infected persons. Eighty (16.0%) out of 500 subjects were positive for Toxoplama IgG antibody by Toxo-Screen DA (bioMerieux) compared with 57 (11.4%) by Sabin-Feldman dye test. The sensivity and specificity of Toxo-Screen DA (bioMerieux) were 100% and 94.8 % respectively which were similar to previous reports from the area of high prevalence of Toxoplasma infection. In present study the positive predictive value of Toxo-Screen DA (bioMerieux) was only 71.3%. The latex agglutination test should be considered as a screening test for Toxoplasma antibody, especially by small laboratories in remote area due to its availability, simplicity, sensitivity and specificity. However, because of its moderate positive predictive value, the test should be used with caution in screening immunocompromised patients and pregnant women living in areas with low prevalence of Toxoplasma infection. Since the number of false seropositive cases would be relatively higher than in a highly prevalent area, confirmation by the dye test would be needed.

Toxoplasma gondii antibody in HIV-infected persons.

Toxoplasmosis in an immunocompromised host was not documented in Thailand until 1992 when HIV/AIDS infection became pandemic. Patients with toxoplasmic encephalitis and cerebral abscess were recorded, particularly from the northern part of the country. However, data on the prevalence of the disease in HIV/AIDS patients is not yet available. In this study the authors determine the prevalence of T. gondii antibody in HIV persons. During a two-year period 312 serum samples of which 190 were HIV positive and the remaining samples were negative for HIV were tested. In the HIV positive group, 44 samples (23.2%) were positive for toxoplasma IgG antibody, whilst in the HIV negative group 36 samples (29.5%) were positive. All antibody titres found were not higher than 1:64. There is no significant difference of toxoplasma IgG antibody in HIV positive and HIV negative persons (p = 0.25). Among the HIV positive and T. gondii antibody positive group, 19 out of 44 persons (43.2%) had symptoms and signs of acute toxoplasmosis involving the eye and/or the central nervous system. Due to the high reactivation rate, the authors propose that all HIV-infected persons should be tested for T. gondii antibody and prophylactic treatment of opportunistic infection from T. gondii should be considered in those with positive results.

Toxoplasma gondii antibody in pregnant women with and without HIV infection.

One thousand two hundred pregnant women were examined for Toxoplasma gondii antibody with the objective of identifying the prevalence and risk factors of the disease. By using Sabin-Feldman Dye test, the prevalence of IgG to Toxoplasma gondii was 13.2%. In this study 19 cases (1.6%) were anti-HIV seropositive. Between HIV-seropositive and HIV-seronegative pregnant women, antibody rates to T. gondii were 21.1% and 13.1% respectively, however, the statistical comparison could not be done due to the very few subjects in the former group (n=4). Concerning the risk factors, among those who had no cat in their house, the prevalence of T. gondii antibody were significantly different between under-cooked and properly-cooked meat consumers (19.5%; and 9.6%; odds ratio=2.28, 95% confidence interval). And when under-cooked meat consumers were excluded, the antibody to T. gondii between two groups (having and not-having cat in the house) were also found the significantly different (31.8% and 19.3%; odd ratio=1.96, 95% confidence interval). In conclusion, consuming under-cooked meat and having a cat in the house, both are risk factors of transmission of toxoplasmosis. Further study with more subjects in HIV-infected pregnant women who had antibody to T. gondii, will be helpful for confirmation of the difference with respect to the non HIV-infected group.