Risk of reactivation of toxoplasmic retinitis following intraocular procedures without the use of prophylactic therapy.

BACKGROUND/AIMS: Toxoplasmic retinochoroiditis is the commonest known cause of posterior uveitis worldwide and reactivation is unpredictable. Based on results from one study, the authors proposed that antitoxoplasmic therapy should be initiated as prophylaxis for intraocular surgery in patients with toxoplasmic scars. The aim of this study is to analyse the risk of toxoplasmic retinochoroiditis reactivation following intraocular procedures. METHODS: Retrospective analysis of the medical records of a total of 69 patients who underwent intraocular surgery and presented with toxoplasmic retinochoroiditis scars. RESULTS: No patient received prophylactic antitoxoplasmic therapy. Reactivation following the surgical procedure occurred in four cases, with one at 3 months and the others respectively at 13, 14 and 17 months. CONCLUSIONS: Our study shows that intraocular surgery did not result in a significant reactivation rate of toxoplasmic retinochoroiditis in the absence of preoperative prophylactic antitoxoplasmic therapy.

Toxoplasmosis ocular / Ocular toxoplasmosis

La toxoplasmosis ocular es una enfermedad producida por el parásito toxoplasma gondii. Es la causa más frecuente de uveítis posterior, es una enfermedad de distribución universal, al menos 500 millones de personas están infectadas en todo el mundo, ocasionando disminución de la visión y ceguera en muchas de ellas. Por tal motivo, realizamos una revisión actualizada sobre, la situación actual a nivel mundial, la historia de la enfermedad, la prevención, formas clínicas y el control de la toxoplasmosis. Se tratan otros aspectos de interés como el modo de transmisión, los hospederos (definitivos e intermediarios) y las manifestaciones clínicas más notables

The ocular toxoplasmosis is an illness caused by Toxoplasma gondii parasite. It is the most frequent cause in posterior uveitis, and it spreads worldwide since at least 500 million people are infected in the entire world, causing decrease of vision and blindness in many of them. This is the reason why we made a literature review, the current situation worldwide, the history, the prevention, the clinical forms and the control of toxoplasmosis. Other interesting aspects were the channel of transmission, the hosts (intermediary and final) and the most remarkable clinical manifestations

Azithromycin reduces ocular infection during congenital transmission of toxoplasmosis in the Calomys callosus model.

Toxoplasma gondii is a widely distributed obligatory intracellular parasite that causes severe disease to the fetus when transmitted during pregnancy. Drugs used to avoid congenital transmission have shown side effects, and their efficacy is controversial. The most widely used treatment for acute toxoplasmosis during pregnancy is pyrimethamine plus sulfadiazine, which has several side effects. In this work, we tested the efficacy of azithromycin in reducing congenital transmission of T. gondii in the large vesper mouse, Calomys callosus, a rodent. Females of C callosus were inoculated perorally with 20 cysts of ME49 strain of T. gondii on the day of fertilization, and fetuses were collected from the 15th to the 19th day of gestation. Azithromycin (300 mg/kg), in association with pyrimethamine (100 or 50 mg/kg) plus sulfadiazine (100 or 75 mg/kg) and folinic acid (15 mg/kg) (SPAf), or vehicle, were administered orally on different days after infection. Brain and ocular tissues were removed and processed for immunohistochemistry using a polyclonal antibody against T. gondii, or were processed for parasite DNA quantification. Toxoplasma gondii was detected in the brains of all females and in fetuses' eyes of C. callosus treated with SPAf. On the other hand, in females treated with azithromycin, there was a reduction of T. gondii in the brains of mothers, and no parasites were detected in eyes of fetuses, indicating that azithromycin may represent an alternative treatment for toxoplasmosis during pregnancy.

Experimental ocular toxoplasmosis in genetically susceptible and resistant mice.

Genetic factors determining the pathogenesis and course of ocular toxoplasmosis are poorly understood. In this study, we explored the development of experimental ocular pathogenesis in genetically dissimilar mice infected with either the RH strain, the PLK strain, or the immunodominant surface antigen 1 (SAG1 [P30])-deficient mutant of the RH strain of Toxoplasma gondii. At 11 days postinfection, ocular infection of C57BL/6 mice with all of the strains of parasites resulted in severe inflammatory lesions and high numbers of parasites in eye tissue; less severe ocular lesions at earlier histopathology and prolonged survival were observed in this mouse strain infected with either the major surface antigen 1-deficient SAG1(-/-) strain or the less virulent PLK strain compared with RH infection. In contrast, both BALB/c and CBA/J mice had less severe lesions and low numbers of parasites in their eye tissue, and infection developed into the chronic stage in these mice. There were significantly higher serum levels of gamma interferon and tumor necrosis factor alpha in C57BL/6 mice than in BALB/c and CBA/J mice following ocular infection. These observations confirm earlier reports on systemic immunity to these parasites that the route of Toxoplasma infection markedly influences survival of mice. Our data indicate that genetic factors of the host as well as the parasite strain are critical in determining susceptibility to experimental ocular toxoplasmosis in murine models.

Prophylaxis for ocular toxoplasmosis.

The protozoan parasite Toxoplasma gondii is an important cause of ocular disease. Ocular toxoplasmosis (OT) can be a progressive and recurring disease that can threaten visual function. We present 2 cases of recurrent OT in immunocompetent patients for whom prophylaxis prevented recurrence of disease.

Reactivation toxoplasmic retinochoroiditis in patients undergoing bone marrow transplantation: is there a role for chemoprophylaxis?

The objective of this study was to report the occurrence of reactivation ocular toxoplasmosis in bone marrow transplant (BMT) recipients and to propose guidelines for identification and chemoprophylaxis of high-risk patients. The study design was a series of cases from the tertiary care university hospital which has an active BMT program. The patients were two recipients of autologous BMTs with past histories of toxoplasma retinochoroiditis who developed symptomatic reactivation of ocular toxoplasmosis as documented by formal opthalmologic examination in the early post-transplant period. Opthalmoscopic examinations in the two patients with non-Hodgkin's lymphoma who received autologous transplants and then developed decreased visual acuity in the first week after transplant revealed recurrent retinochoroiditis adjacent to old toxoplasma lesions. Pre-transplant eye examinations in both patients had demonstrated only inactive chorioretinal scars. Therapy with sulfadiazine, pyrimethamine and prednisone ultimately led to resolution of retinitis in both patients. BMT recipients who are seropositive for antibody to T. gondii and have findings consistent with previous toxoplasma retinochoroiditis on pre-transplant ophthalmologic examination appear to be at risk for reactivation of ocular toxoplasmosis in the early post-transplant period and may warrant preventive chemoprophylaxis for toxoplasmosis.

[Cost-benefit analysis of screening for congenital toxoplasmosis]. / Kosten-Nutzen-Analyse des Screenings auf kongenitale Toxoplasmose.

A comprehensive cost-benefit analysis of possible screening strategies for congenital toxoplasmosis is necessary as a basis for the decision whether or not screening is efficient and socially desirable. The total costs of the disease in Switzerland were calculated for the year 1990. Direct costs (all diagnostic and therapeutic interventions, including care of handicapped children) and indirect costs (partial and total work losses in the future) were taken into account. Today, the direct costs amount to approx. SFr. 20 mio per year (i.e. approx. SFr. 2.8 mio per million population). The indirect costs were calculated at SFr. 4 mio per year. Moreover, the costs incurred with three possible screening programs (1 test with all pregnant women, with 1, 2 or 5 additional tests, depending on the strategy) were estimated, together with the concomitant cost savings. The financial resources needed for the screenings would amount to SFr. 7 mio-18 mio per year, depending on the strategy chosen. However, the possible savings would be in the range of SFr. 4 mio-12 mio only. The possible savings are, in any case, of the same order of magnitude as the costs for screening. Screening would become cost-efficient if costs for the serological tests could be lowered.

Effect of immunization with attenuated Mycobacterium bovis on experimental toxoplasmic retinochoroiditis.

Administration of attenuated Mycobacterium bovis (Bacillus Calmette-Guérin or BCG) provides nonspecific resistance to a variety of microbial infections and tumors. This is associated with a state of augmented immunologic responsiveness. Mustering defenses against intracellular parasites, such as Toxoplasma gondii, presents a special problem that can be met only by measures that alter the intracellular environment. Our study was designed to evaluate the effect of prior immunization of rabbits with BCG on experimental toxoplasmic retinochoroiditis. One group of rabbits was immunized by the intravenous administration of BCG, another group by the retrobulbar injection of BCG, and a third group, unvaccinated, served as a control. Intravenous immunization provided significant protection against Toxoplasma organisms injected into the suprachoroidal space. In the immunized rabbits, the onset of Toxoplasma retinochoroiditis was delayed and the severity of the disease reduced. Although Toxoplasma was isolated from the chorioretinal tissues of both BCG-immunized and control rabbits, Toxoplasma antibody was not (with one exception) detected in the sera of BCG-immunized rabbits. While vaccination by the retrobulbar route produced little or no effect, intravenous administration of BCG provided nonspecific resistance to Toxoplasma retinochoroiditis in rabbits.