Therapy for Ocular Toxoplasmosis – The Future

The Role of Corticosteroids in Treating Acute Ocular Toxoplasmosis in an Immunocompetent Patient: A Case Report

Background

This study aimed to report a case who was treated with corticosteroids and anti- parasitic agents for ocular toxoplasmosis, but who progressed to acute retinal necrosis, and finally retinal detachment.

Case Presentation

A 42-year-old man presented to the ophthalmology clinic with a 1-month history of progressive blurred vision and floaters in his right eye. His best visual acuity (VA) was 20/20 in both eyes. The anterior segment was unremarkable. Funduscopic examination of the right eye revealed active lesions of whitish foci of chorioretinitis with surrounding edema along the superonasal vessels, and retinal vasculitis with perivascular sheathing. Serologic testing was positive for Toxoplasma gondii IgM and IgG, but negative for other virus- and syphilis infections. Ocular toxoplasmosis was diagnosed. Corticosteroids and anti-parasitic agents were given simultaneously, but his right eye VA became 20/100. Funduscopic examination revealed retinal necrosis with localized retinal breaks. We immediately performed focal photocoagulation, however, his right eye progressed to retinal detachment and required vitrectomy.

Conclusion

Early administration of systemic corticosteroids in patients with acquired acute ocular toxoplasmosis may lead to complications that impair vision. Intensive observation should be arranged after corticosteroid use.

Congenital Toxoplasmosis: The State of the Art

Infection with the protozoan parasite Toxoplasma gondii occurs worldwide and usually causes no symptoms. However, a primary infection of pregnant women, may infect the fetus by transplacental transmission. The risk of mother-to-child transmission depends on week of pregnancy at the time of maternal infection: it is low in the first trimester, may reach 90% in the last days of pregnancy. Inversely, however, fetal disease is more severe when infection occurs early in pregnancy than later. Systematic serologic testing in pregnant women who have no antibodies at the beginning of pregnancy, can accurately reveal active maternal infection. Therefore, the risk of fetal infection should be assessed and preventive treatment with spiramycin must be introduced as soon as possible to reduce the risk of mother-to-child transmission, and the severity of fetal infection. When maternal infection is confirmed, prenatal diagnosis with Polymerase Chain Reaction (PCR) on amniotic fluid is recommended. If fetal infection is certain, the maternal treatment is changed to a combination of pyrimethamine-sulfonamide and folinic acid. Congenitally infected newborns are usually asymptomatic at birth, but at risk for tardive sequelae, such as blindness. When congenital infection is evident, disease include retinochoroiditis, cerebral calcifications, hydrocephalus, neurocognitive impairment. The diagnosis of congenital infection must be confirmed at birth and management, specific therapy, and follow-up with multidisciplinary counseling, must be guaranteed.

Promising Drug Targets and Compounds with Anti-Toxoplasma gondii Activity

Toxoplasmosis is a parasitic disease caused by the globally distributed protozoan parasite Toxoplasma gondii, which infects around one-third of the world population. This disease may result in serious complications for fetuses, newborns, and immunocompromised individuals. Current treatment options are old, limited, and possess toxic side effects. Long treatment durations are required since the current therapeutic system lacks efficiency against T. gondii tissue cysts, promoting the establishment of latent infection. This review highlights the most promising drug targets involved in anti-T. gondii drug discovery, including the mitochondrial electron transport chain, microneme secretion pathway, type II fatty acid synthesis, DNA synthesis and replication and, DNA expression as well as others. A description of some of the most promising compounds demonstrating antiparasitic activity, developed over the last decade through drug discovery and drug repurposing, is provided as a means of giving new perspectives for future research in this field.

Treatment Strategy in Human Ocular Toxoplasmosis: Why Antibiotics Have Failed

Background: There is currently no clear evidence of the effectiveness of antibiotic therapy in acute ocular toxoplasmosis (OT), but its effect as a secondary prophylaxis is undisputed. The majority of uveitis specialists advocate treatment. This meta-analytic review aims to critically analyze determinants of treatment success and to update current treatment strategies for OT in order to explain this discrepancy. Methods: A systematic literature search was performed in NCBI/PubMed, Clinical Trials, Google Scholar and ScienceDirect to retrieve pro- and retrospective studies using the key terms “ocular toxoplasmosis” or “retinochoroiditis” and “immunocompetent” and “treatment” or “therapy” and “human.” Of these, larger case series and prospective clinical studies and cross references identified from meta-analyses were selected by a manual search, and primary and secondary outcome parameters were extracted. Results: Ten case series and clinical trials reported success parameters for treatment outcomes, and four additional for recurrence prophylaxis. Five treatment studies were randomized clinical trials, three comparative and two noncomparative case series. Though several outcome parameters were reported, five of them defined time to healing, four visual gain and one lesion size as primary and secondary outcome parameters, recurrence rate as a secondary outcome parameter was reported once. No conclusive evidence was found for an antibiotic treatment effect. Four prophylaxis studies addressed the prevention of recurrences after treatment. The primary outcome in all studies was the effect of treatment and prophylaxis on recurrences, and all four found a significant effect on the risk of and time to recurrences. Conclusions: Antibiotic treatment of OT aims at controlling parasite proliferation. The absence of an effect on visual acuity and time to healing is thus not surprising. The fact that time to and number of recurrences respond to recurrence of prophylaxis proves the antibiotic effect on parasite activity.

Ocular toxoplasmosis: adverse reactions to treatment in a Brazilian cohort

Background

The purpose of this study was to estimate the frequency and describe the adverse drug reactions (ADRs) associated with the classic treatment of ocular toxoplasmosis (OT), namely sulfadiazine, pyrimethamine, corticosteroids and folinic acid.

Methods

We performed a descriptive study of a prospective cohort of patients with OT treated with the classic therapy. Data were collected during medical consultations and treatment.

Results

Of the 147 patients studied, 85% developed one or more ADR. Women presented more ADRs than men (95% vs 77%). Of the total reactions (n=394), 82% were mild, but we found one life-threatening event (Stevens-Johnson syndrome). The most frequent types (71%) of ADRs were gastrointestinal, skin and neurological or psychiatric. The majority of ADRs (90.3%) occurred before the second week of treatment. A third of the patients were treated for the ADR and 10% dropped out of OT treatment. Most (70%) of the ADRs were characterized as being probably caused by the drugs and may be associated with prednisone, sulfadiazine and sulfadiazine/prednisone. Six percent of ADRs were not previously described, such as taste alteration, constipation/bloating, dyspnoea, sweating and somnolence.

Conclusions

Our results suggest a high rate of ADRs to OT classic treatment, which requires careful follow-up in order to identify and treat ADRs early.

Effectiveness of Treatments for Ocular Toxoplasmosis

Purpose: To evaluate the effectiveness of treatments for ocular toxoplasmosis (OT).Methods: A review of charts was conducted from patients who experienced an active episode of OT treated at the Federal University of São Paulo and associated sites. OT charts were reviewed to determine treatment effectiveness based on clinical judgment, taking clinical course and outcome into consideration in addition to change in best-corrected visual acuity. Treatment emergent adverse events (TEAEs) were used to assess safety.Results: Overall, 451/1200 patient charts met the inclusion criteria. The most commonly prescribed treatment was trimethoprim + sulfamethoxazole (52.3%) followed by pyrimethamine + sulfadiazine (28%). Treatment was successful in 96.9% of patients. Irrespective of the treatment, active lesions were resolved in 63.9% of patients within 6 weeks. Vision improved in 56.3% of patients. The incidence of TEAEs was low (10%).Conclusions: All treatments were effective for active episodes of OT, with few side effects.

Congenital toxoplasmosis: An overview of the neurological and ocular manifestations

Toxoplasma gondii is an obligate intracellular parasite which is known to infect one-third of the total world population chronically though it is asymptomatic in immunocompetent patients. However, in an immunocompromised patient or an infected fetus, it may cause devastating effects. The parasite may cross the placenta of an infected pregnant woman and probably infect the fetus congenitally. The severity of the infection depends on the gestational age at which the infection has occurred i.e., if it has occurred in the early phase, the rate of transmission is low but the severity is high if the fetus is infected and if it has occurred in the later phase then transmission rate is higher while the severity would be low. Congenital toxoplasmosis may result in non-specific consequences like abortion, intra-uterine growth restriction, jaundice, hepatosplenomegaly or even intra-uterine death. It may also result in neurological or ocular manifestations like intracranial calcifications, hydrocephalus or retinochoroiditis. The diagnosis may be done by serological screening of anti-Toxoplasma antibodies (IgM and IgG) while PCR of the amniotic fluid or the placenta is the confirmatory test. Acute or chronic infections may be differentiated by IgG avidity tests. The treatment regimens include spiramycin to prevent congenital transmission from an infected mother, pyrimethamine, sulfadoxine and folinic acid to treat the infected fetus, CSF shunting for the treatment of hydrocephalus and a combination of pyrimethamine, azithromycin, and corticosteroids for treating ocular toxoplasmosis.

Ocular Toxoplasmosis in Tropical Areas: Analysis and Outcome of 190 Patients from a Multicenter Collaborative Study

PURPOSE

To describe clinical findings and outcomes for ocular toxoplasmosis in an international multicenter collaborative study.

METHODS

Retrospective analysis of 190 patients diagnosed with ocular toxoplasmosis from three study sites (Brazil, India, and Singapore).

RESULTS

There were 93 (48.9%) females with a mean age of 32.8 years. The most common symptoms were isolated blurring of vision (36.8%), followed by blurring of vision with floaters (21.1%). Treatment regimens varied largely from monotherapy to multiple combination therapies. Final visual acuity of ≥20/40 was achieved in 106 (74.2%) patients. In a median follow-up period of 31 weeks (range 12-749 weeks), 83/190 (43.7%) patients suffered a relapse.

CONCLUSIONS

There appears to be geographical variation in the presentation of ocular toxoplasmosis. Compared to previous studies, we did not observe the '"dual peak" phenomenon of chronic and active disease based on age at presentation, and there was less bilateral and macular involvement (but more peripheral involvement).

Recent Developments in the Diagnosis and Treatment of Ocular Toxoplasmosis

Ocular toxoplasmosis, a chorioretinal infection with Toxoplasma gondii, is the most common etiology of posterior uveitis in many countries. Accurate diagnosis depends heavily on the characteristic clinical features of this disease, but atypical presentations, especially in immunocompromised patients, may create diagnostic challenges and lead to misdiagnosis and inappropriate treatment. Molecular biology techniques to diagnose ocular toxoplasmosis have been available for many years and are now accessible as standard laboratory tests in many countries. Aqueous humor or vitreous evaluation to detect parasite DNA by polymerase chain reaction or specific antibody may provide definitive evidence for rapid diagnosis. Oral pyrimethamine and sulfadiazine plus systemic corticosteroids are an effective therapy for ocular toxoplasmosis. Recent data supports the use of other treatment approaches, including intravitreal antibiotics. The aim of the present review is to discuss briefly the new diagnostic tools and treatment options for ocular toxoplasmosis.

Current Practices in Ocular Toxoplasmosis: A Survey of Brazilian Uveitis Specialists

PURPOSE

To describe treatment practices for ocular toxoplasmosis among members of the Brazilian Uveitis Society.

METHODS

An online questionnaire sent to specialists, between October 2014 and March 2015.

RESULTS

Most respondents (67.9%) treat all active cases. Most specialists consider visual acuity <20/200 (88.2%), severe vitreous inflammation (94.1%), and ocular disease during acquired infection (88.2%) as absolute indications for treatment. Systemic steroids are associated with anti-toxoplasmic therapy in most cases by 50.9% of the respondents. For immunocompetent individuals, 57.4% of the respondents chose trimethoprim/sulfamethoxazole. Classical therapy (sulfadiazine/pyrimethamine) is preferred most for patients with central lesions (70.4%), immunosuppression (68.4%), acquired infection (70.4%), and atypical forms (74.1%). For patients with frequent relapses, 84.9% of the respondents preferred antibiotic prophylaxis.

CONCLUSIONS

Treatment patterns of ocular toxoplasmosis are not uniform among Brazilian specialists. Most specialists treat all cases of active retinochoroiditis. Typical cases are more frequently treated with trimethoprim/sulfamethoxazole. However, classical therapy is the regimen of choice when lesions are considered more severe.

The Impact of Short-Term, Intensive Antifolate Treatment (with Pyrimethamine and Sulfadoxine) and Antibiotics Followed by Long-Term, Secondary Antifolate Prophylaxis on the Rate of Toxoplasmic Retinochoroiditis Recurrence

PURPOSE

To assess the impact of intensive antifolate treatment, followed by secondary antifolate prophylaxis (A-SP) on the recurrence rate of toxoplasmic retinochoroiditis (TRC). To investigate whether there are any other factors potentially predisposing for recurrence.

MATERIAL AND METHODS

A total of 637 medical records of TRC patients, who had been treated in the years 1994-2013 were reviewed. All patients were treated with pyrimethamine /sulfadoxine one 25mg/500mg tablet daily (P/S 25/500mg) for 21 days with a double loading dose for the first two days. From Day 2 the patients also received prednisone at a starting dose of 40mg and spiramycine 3 million IU three times daily, given for 10 days followed by azithromycin 500mg once daily for another 6 days. The analysis of the recurrence rate involved 352 patients who had completed 6-month secondary prophylaxis (P/S one 25 mg/500mg tablet twice a week).

RESULTS

When secondary antifolate prophylaxis (A-SP) was instituted immediately after the treatment for TRC, the probability of 3-year recurrence-free survival after the first course of A-SP was 90.9%. A recurrence was most likely approximately 3.5 years after the first treatment. A univariate Cox regression model demonstrated that a risk for recurrence was 2.82 times higher (p = 0.02) in patients with retinal scars. In the multivariate analysis, the risk for recurrence was 2.41 higher (p = 0.06). In patients with haemorrhagic lesions the risk for recurrence was lower, aRR = 0.17 (approaching borderline statistical significance p = 0.08).

CONCLUSIONS

With the institution of A-SP of immediately after the intensive treatment for TRC, i.e. when a reactivation was most likely, there was no recurrence during A-SP. Following A-SP the recurrence rates were low and recurrence-free periods tended to be longer. The treatment regimen employed had a beneficial effect on the recurrence interval as it reduced and delayed the highest probability of recurrence.

Toxoplasmic Retinochoroiditis: Clinical Characteristics and Visual Outcome in a Prospective Study

Purpose

To ascertain the clinical features and visual outcome of toxoplasma retinochoroiditis in a large series of cases.

Subjects and Methods

Two hundred and thirty subjects diagnosed with active toxoplasma retinochoroiditis were prospectively followed for periods ranging from 269 to 1976 days. All patients presented with active retinochoroiditis and positive IgG T. gondii serology at the beginning of the study and received a standardized drug treatment for toxoplasmosis, both in the first episode and in the subsequent recurrences.

Results

The group involved 118 (51.3%) men and 112 (48.7%) women, with ages ranging from 14 to 77 years, mean of 32.4 years (SD = 11.38). Primary retinochoroidal lesions were observed in 52 (22.6%) cases and active retinochoroiditis combined with old scars in 178 (77.4%) subjects at the beginning of the study. A hundred sixty-two recurrent episodes in 104 (45.2%) patients were observed during follow-up. New subclinical retinochoroidal lesions were detected in 23 of 162 (14.2%) recurrences episodes during the follow-up. Posterior segment complications were observed in 73 (31.7%) subjects. Retinochoroidal lesions adjacent to the optic nerve and in the macular area were observed in 27 of 40 (67.5%) cases of severe visual impairment (VA = 20/200 or worse).

Conclusion

Toxoplasma retinochoroiditis in this population had a high recurrence rate after an active episode. Severe visual impairment was associated with location of the retinochoroidal scar, recurrences and posterior segment complications. It is crucial to consider the location of the lesion in studies analyzing visual prognosis as a measure for treatment effectiveness and prevention strategies.

Ocular toxoplasmosis affects millions of people worldwide and is a cause of severe vision loss. Prospective studies on the disease are rare and require long and expensive follow-ups. A network of intricate host and parasite factors can influence its evolution and its treatment is still subject of discussion and controversy. This article describes clinical features in a series of cases prospectively followed, confirming findings of previous studies conducted in other continents, despite the probable genetic variability of the evaluated populations and parasite. In addition, brings insights into the course of the disease and causes of visual impairment that may help future studies on strategies for treatment and prevention.

Ocular toxoplasmosis: background and evidence for an antibiotic prophylaxis

PURPOSE OF REVIEW

The purpose of this review was to provide an overview of current data on antibiotic prophylaxis in ocular toxoplasmosis.

RECENT FINDINGS

Studies showing the prophylactic effect of long-term antibiotics are discussed. Prophylaxis seems to be justified in patients with a high risk of recurrence because of antibiotic's potential side-effects. Therefore, predisposing factors leading to a higher risk of recurrence and the time period during which an antibiotic prophylaxis is most appropriate are reviewed. Finally, a patient-individualized treatment recommendation is summarized.

SUMMARY

In the current literature, two prospective, randomized case-control studies exist, which show the protective effect of an antibiotic prophylaxis. Hematologic, gastrointestinal and dermatologic complications are potential side-effects. Especially during the first year after suffering a recurrence, an antibiotic prophylaxis seems to be justified. The risk of a recurrence is inter alia influenced by the duration of the disease, the immune status of the host and the patient's age. Therefore, an antibiotic prophylaxis should be considered for patients who have recently been infected with ocular toxoplasmosis, for middle-aged and elderly patients and patients with a compromised immune system. This should be discussed with each patient individually, especially if the lesion is close to the macula.

Current Therapy of Acquired Ocular Toxoplasmosis: A Review

Caused by the parasite Toxoplasma gondii, ocular toxoplasmosis (OT) is the most common form of posterior infectious uveitis. Combined antiparasitic therapy is the standard treatment for OT, but several other schemes have been proposed. The purpose of the present study was to review the literature on the treatment of OT and provide ophthalmologists with up-to-date information to help reduce OT-related visual morbidity. In conclusion, no ideal treatment scheme was identified; currently prescribed therapeutic schemes yield statistically similar functional outcomes.

Interleukin-6-driven inflammatory response induces retinal pathology in a model of ocular toxoplasmosis reactivation

Ocular inflammation is one of the consequences of infection with the protozoan parasite Toxoplasma gondii. Even if lesions are self-healing in immunocompetent persons, they pose a lifetime risk of reactivation and are a serious threat to vision. As there are virtually no immunological data on reactivating ocular toxoplasmosis, we established a model of direct intravitreal injection of parasites in previously infected mice with a homologous type II strain. Two different mouse strains with variable ability to control retinal infection were studied in order to describe protective and deleterious reaction patterns. In Swiss-Webster mice, which are already relatively resistant to primary infection, no peak of parasite load was observed upon reinfection. In contrast, the susceptible inbred strain C57BL/6 showed high parasite loads after 7 days, as well as marked deterioration of retinal architecture. Both parameters were back to normal on day 21. C57BL/6 mice also reacted with a strong local production of inflammatory and Th1-type cytokines, like interleukin-6 (IL-6), IL-17A, and gamma interferon (IFN-γ), while Swiss-Webster mice showed only moderate expression of the Th2 cytokine IL-31. Interestingly, rapid intraocular production of anti-Toxoplasma antibodies was observed in Swiss-Webster but not in C57BL/6 mice. We then localized the cellular source of different immune mediators within the retina by immunofluorescence. Finally, neutralization experiments of IFN-γ or IL-6 demonstrated the respective protective and deleterious roles of these cytokines for parasite control and retinal integrity during reinfection. In conclusion, we developed and immunologically characterized a promising mouse model of reactivating ocular toxoplasmosis.