Recurrent ocular disease in postnatally acquired toxoplasmosis

CD8+ T-cell Exhaustion Phenotype in Human Asymptomatic and Ocular Toxoplasmosis

This work analyzed exhaustion markers in CD8+ T-cell subpopulations in 21 samples of peripheral blood mononuclear cells (PBMCs) from individuals with ocular toxoplasmosis (n = 9), chronic asymptomatic toxoplasmosis (n = 7), and non-infected people (n = 5) by using RT-qPCR and flow cytometry techniques. The study found that gene expression of PD-1 and CD244, but not LAG-3, was higher in individuals with ocular toxoplasmosis versus individuals with asymptomatic infection or uninfected. Expression of PD1 in CD8+ central memory (CM) cells was higher in nine individuals with toxoplasmosis versus five uninfected individuals (p = .003). After ex vivo stimulation, an inverse correlation was found between the exhaustion markers and quantitative clinical characteristics (lesion size, recurrence index, and number of lesions). A total exhaustion phenotype was found in 55.5% (5/9) of individuals with ocular toxoplasmosis. Our results suggest that the CD8+ exhaustion phenotype is involved in the pathogenesis of ocular toxoplasmosis.

Risk factors for recurrences and visual impairment in patients with ocular toxoplasmosis: A systematic review and meta-analysis

BACKGROUND

Ocular toxoplasmosis (OT) is caused by the parasite Toxoplasma gondii. OT is the leading cause of posterior uveitis globally; it is a recurrent disease that may result in visual impairment and blindness. This systematic review and meta-analysis aim to summarize and evaluate the risk factors for recurrences, visual impairment, and blindness described in the literature worldwide.

METHODS AND FINDINGS

We performed a systematic literature search in PubMed, Embase, VHL, Cochrane Library, Scopus, and DANS EASY Archive. All studies reporting patients with clinically and serologically confirmed OT presenting any clinical or paraclinical factor influencing recurrences, visual impairment, and blindness were included. Studies presenting secondary data, case reports, and case series were excluded. An initial selection was made by title and abstract, and then the studies were reviewed by full text where the eligible studies were selected. Then, the risk of bias was assessed through validated tools. Data were extracted using a validated extraction format. Qualitative synthesis and quantitative analysis were done. This study was registered on PROSPERO (CRD42022327836).

RESULTS

Seventy two studies met the inclusion criteria. Fifty-three were summarized in the qualitative synthesis in three sections: clinical and environmental factors, parasite and host factors, and treatment-related factors. Of the 72 articles, 39 were included in the meta-analysis, of which 14 were conducted in South America, 13 in Europe, four in Asia, three multinational, two in North America and Central America, respectively, and only one in Africa. A total of 4,200 patients with OT were analyzed, mean age ranged from 7.3 to 65.1 year of age, with similar distribution by sex. The frequency of recurrences in patients with OT was 49% (95% CI 40%-58%), being more frequent in the South American population than in Europeans. Additionally, visual impairment was presented in 35% (95% CI 25%-48%) and blindness in 20% (95% CI 13%-30%) of eyes, with a similar predominance in South Americans than in Europeans. On the other hand, having lesions near the macula or adjacent to the optic nerve had an OR of 4.83 (95% CI; 2.72-8.59) for blindness, similar to having more than one recurrence that had an OR of 3.18 (95% CI; 1.59-6.38). Finally, the prophylactic therapy with Trimethoprim/Sulfamethoxazole versus the placebo showed a protective factor of 83% during the first year and 87% in the second year after treatment.

CONCLUSION

Our Systematic Review showed that clinical factors such as being older than 40 years, patients with de novo OT lesions or with less than one year after the first episode, macular area involvement, lesions greater than 1 disc diameter, congenital toxoplasmosis, and bilateral compromise had more risk of recurrences. Also, environmental and parasite factors such as precipitations, geographical region where the infection is acquired, and more virulent strains confer greater risk of recurrences. Therefore, patients with the above mentioned clinical, environmental, and parasite factors could benefit from using prophylactic therapy.

Long-term Results of Trimethoprim-Sulfamethoxazole Versus Placebo to Reduce the Risk of Recurrent Toxoplasma gondii Retinochoroiditis

PURPOSE

To compare the effects of 1 year of treatment with trimethoprim-sulfamethoxazole (TMP-SMZ) vs placebo in reducing the risk of recurrence of toxoplasmic retinochoroiditis during a 6-year follow-up period.

DESIGN

Randomized, double-masked clinical trial.

METHODS

This cohort included 141 subjects recruited in Campinas, Brazil. The inclusion criterion was unilateral active recurrent toxoplasmic retinochoroiditis. All subjects were treated with 1 dose of TMP-SMZ (160 mg/800 mg) twice daily for 45 days, and all lesions healed after this treatment. After this initial treatment, subjects were randomly assigned to group 1 (1 TMP-SMZ dose every other day for 311 days) or group 2 (1 identical placebo tablet containing starch with no active ingredients every other day for 311 days). Between the second and sixth years of follow-up appointments, none of the subjects received treatment unless a new recurrence episode had occurred. The primary outcomes were recurrent toxoplasmic retinochoroiditis within the first year of follow-up and recurrent toxoplasmic retinochoroiditis in the 6 years of follow-up.

RESULTS

The cumulative probability of recurrence 1, 2, 3, 4, 5, and 6 years after the initial infection was, respectively, 13.0% (9/69), 17.4% (12/69), 20.3% (14/69), 23.2% (16/69), 26.1% (18/69), and 27.5% (19/69) in the placebo group and 0%, 0%, 0%, 0%, 0%, and 1.4% (1/72) in the TMP-SMZ group (P < .001; log-rank test). There were 3 cases (3/69; 4.3%) of multiple recurrences in the same individual in the placebo group. No treatment-limiting toxicity or side effects were observed in either group. New recurrences were more frequent among female subjects.

CONCLUSIONS

TMP-SMZ may be used safely for prophylaxis of recurrent toxoplasmic retinochoroiditis and may provide long-term benefits.

Clinical and Biological Factors Associated With Recurrences of Severe Toxoplasmic Retinochoroiditis Confirmed by Aqueous Humor Analysis

PURPOSE

To investigate clinical and biological factors influencing recurrences of severe toxoplasmic retinochoroiditis (TRC) confirmed by aqueous humor analysis.

DESIGN

Retrospective case series.

METHODS

Retrospective analysis of 87 subjects with severe TRC, proven by positive Goldmann-Witmer coefficient (GWC), Toxoplasma gondii (T. gondii) immunoblot, or T. gondii-specific polymerase chain reaction (PCR) in aqueous humor. Cases with immunosuppression or retinal scars without previous recorded episode were excluded. Time-dependent, clinical, treatment-related, and biological factors were explored by univariate and multivariate shared frailty survival analyses.

RESULTS

Among 44 included subjects (age, 40.4 ± 17.6 years; follow-up, 8.3 ± 2.7 years), 22 presented recurrences. There was 0.11 recurrence/patient/year and mean disease-free interval was 5.0 ± 2.9 years. The risk of recurrence was higher immediately after an episode (P < .0001). Among recurrent cases, the risk of multiple recurrences was higher when the first recurrence occurred after longer disease-free intervals (P = .046). In univariate analysis, the recurrence risk declined with higher number of intense bands on aqueous T. gondii immunoblot (P = .006), and increased when venous vasculitis was present initially (P = .019). Multivariate analysis confirmed that eyes with more intense bands on immunoblot had fewer recurrences (P = .041). There was a near-significant risk elevation after pyrimethamine/azithromycin treatment (P = .078 and P = .054, univariate and multivariate). Intravenous corticosteroid administration, oral corticosteroid administration, aqueous GWC, and T. gondii PCR did not influence recurrences (P = .12, P = .10, P = .39, and P = .96, respectively).

CONCLUSIONS

Recurrences of severe TRC are not random and may be influenced by clinical and biological factors possibly related to blood-retinal barrier alterations. These results may contribute to identifying biomarkers for TRC reactivation.

Trimethoprim-Sulfamethoxazole Versus Placebo in Reducing the Risk of Toxoplasmic Retinochoroiditis Recurrences: A Three-Year Follow-up

PURPOSE

To compare the effects of 1 year of treatment with trimethoprim/sulfamethoxazole (TMP-SMZ) vs a placebo in reducing the risk of toxoplasmic retinochoroiditis recurrences during a 3-year follow-up period.

DESIGN

Randomized, double-masked clinical trial.

METHODS

This cohort included 141 volunteers recruited in Campinas, Brazil. Inclusion criterion was unilateral active recurrent toxoplasmic retinochoroiditis. All volunteers were treated with 1 tablet of TMP-SMZ (160 mg/800 mg) twice daily for 45 days, and all lesions healed after this treatment. After this initial treatment, the volunteers were randomly assigned to Group 1 (1 TMP-SMZ tablet every 2 days for 311 days) or Group 2 (1 identical placebo tablet containing starch with no active ingredients every 2 days for 311 days). At the second- and third-year follow-up appointments, none of the volunteers received treatment unless a new recurrence episode had occurred. The primary outcomes were recurrent toxoplasmic retinochoroiditis within the first year of follow-up and recurrent toxoplasmic retinochoroiditis within the third year of follow-up.

RESULTS

The cumulative probability of recurrence at 1, 2, and 3 years of follow-up were, respectively, 13.0% (9/69), 17.4% (12/69), and 20.3% (14/69) in the placebo group and 0% (0/72) in the TMP-SMZ group (P < .001, log-rank test). There was no case of multiple recurrences in the same individual. No treatment-limiting toxicity or side effects were observed in either group. New recurrences were more frequent among female volunteers.

CONCLUSIONS

TMP-SMZ may be used safely for prophylaxis of recurrent toxoplasmic retinochoroiditis, with long-term benefits.

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.

Experimental Models of Ocular Infection with Toxoplasma Gondii

Ocular toxoplasmosis is a vision-threatening disease and the major cause of posterior uveitis worldwide. In spite of the continuing global burden of ocular toxoplasmosis, many critical aspects of disease including the therapeutic approach to ocular toxoplasmosis are still under debate. To assist in addressing many aspects of the disease, numerous experimental models of ocular toxoplasmosis have been established. In this article, we present an overview on in vitro, ex vivo, and in vivo models of ocular toxoplasmosis available to date. Experimental studies on ocular toxoplasmosis have recently focused on mice. However, the majority of murine models established so far are based on intraperitoneal and intraocular infection with Toxoplasma gondii. We therefore also present results obtained in an in vivo model using peroral infection of C57BL/6 and NMRI mice that reflects the natural route of infection and mimics the disease course in humans. While advances have been made in ex vivo model systems or larger animals to investigate specific aspects of ocular toxoplasmosis, laboratory mice continue to be the experimental model of choice for the investigation of ocular toxoplasmosis.

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.

Clinical manifestations of ocular toxoplasmosis

Clinical manifestations of ocular toxoplasmosis are reviewed. Findings of congenital and acute acquired ocular toxoplasmosis include retinal scars, white-appearing lesions in the active phase often associated with vitritis. Complications can include fibrous bands, secondary serous or rhegmatogenous retinal detachments, optic neuritis and neuropathy, cataracts, increased intraocular pressure during active infection, and choroidal neovascular membranes. Recurrences in untreated congenital toxoplasmosis occur in teenage years. Manifestations at birth are less severe, and recurrences are fewer in those who were treated promptly early in the course of their disease in utero and in the first year of life. Severe retinal involvement is common at diagnosis of symptomatic congenital toxoplasmosis in the United States and Brazil. Acute acquired infections also may be complicated by toxoplasmic retinochoroiditis, with recurrences most common close to the time of acquisition. Suppressive treatment can reduce recurrent disease.

A prospective study of Toxoplasma-positive pregnant women in southern Brazil: a health alert

We evaluated anti-Toxoplasma gondii IgM-reactive pregnant women seen at a high-risk pregnancy outpatient clinic. From March 2005 to January 2008 in Paraná, Brazil, pregnant women seen by the Brazilian Public Health System, in any gestational period, who were anti-T. gondii IgM-positive, were followed. Clinical symptoms were noted, and tests performed including IgA, IgG avidity, ultrasonogram, and amniocentesis (PCR/inoculation in mice). Of 75 patients, 8 showed low, 3 intermediate and 31 high IgG avidity. Of those who underwent the avidity test, 31 (70.5%) were in the second trimester of pregnancy. Thirty-two (42.7%) pregnant women received specific treatment. Six received triple combination treatment; in three, tachyzoites were isolated, although only one was PCR-positive, showing changes in the cerebral sonogram, borderline IgA, and the Sabin tetrad. One fetus died, and one non-reactive IgM pregnant woman showed ocular recurrence. The municipality of residence, contact with cats during adulthood, and ingestion of unpasteurized milk were shown to be important risk factors. Congenital toxoplasmosis was observed in a pregnancy referred late for treatment. Follow-up of children born to mothers with diagnosed or suspected acute toxoplasmosis is crucial in the management of the changes that toxoplasmosis may cause.

Respective roles of acquired and congenital infections in presumed ocular toxoplasmosis

PURPOSE

To analyze the roles of acquired or congenital infections in cases of ocular toxoplasmosis, and to compare their clinical manifestations.

DESIGN

Retrospective, observational case series.

METHODS

We analyzed the charts of consecutive patients with a diagnosis of ocular toxoplasmosis. Data from the French program for the prevention of congenital toxoplasmosis were used to assess the origin of infection. The data included patients' serologic status prior to their ocular manifestations and patients' mothers' serologic status before, during, and/or after pregnancy. Infections were categorized as congenital, acquired, or unknown.

RESULTS

Of 425 cases of ocular toxoplasmosis, 100 (23.5%) were acquired, 62 (14.6%) were congenital, and 263 (61.9%) were of unknown origin. At the time of the study, the mean age of the patients with congenital ocular toxoplasmosis was 9.1 +/- 8.8 years, and was 21.7 +/- 12.6 years in the patients with acquired ocular toxoplasmosis (P < .0001). Bilateral chorioretinitis was observed in 4% of acquired cases and in 43.5% of congenital cases (P < .0001). In acquired infections, mean decimal visual acuity (VA) was 1.0 (logarithm of the minimum angle of resolution [logMAR] 0.0 +/- 1 line) in the best eye and 0.4 (logMAR 0.4 +/- 5 lines) in the worst eye. In congenital cases, mean decimal VA was 0.8 (logMAR 0.1 +/- 4 lines) in the best eye and 0.25 (logMAR 0.6 +/- 7 lines) in the worst eye (P < .05).

CONCLUSION

In cases where the origin of the infection could be determined, acquired infections were a more frequent cause of ocular toxoplasmosis than congenital infections. Cases of congenital ocular toxoplasmosis were more severe than acquired cases.

Analysis of recurrence patterns associated with toxoplasmic retinochoroiditis

PURPOSE

Toxoplasmic retinochoroiditis is thought to recur randomly. We sought to determine whether there is, instead, a longitudinal pattern of recurrences and to identify risk factors for recurrence.

DESIGN

Longitudinal cohort study.

METHODS

We collected the following data for 143 patients with toxoplasmic retinochoroiditis in The Netherlands: gender, first affected eye, age at first episode, mode of Toxoplasma gondii infection (congenital vs postnatal), treatment history, and presence of retinal scars at initial examination. For each episode, we determined age, duration since first episode, and interval since previous episode. We estimated the relationship between disease-free interval after an episode and recurrence risk. The influence of host and disease factors on recurrence risk was analyzed using Cox regression with frailty modeling for correlated intrapatient recurrence times. We performed a Monte Carlo test for occurrence of clusters after prolonged disease-free intervals.

RESULTS

Follow-up ranged from 0.3 to 41 years (323 episodes in first-affected eyes). Recurrence risk was highest immediately after an episode, then decreased with increasing disease-free intervals, a pattern consistent with clustering. Relative risk (RR) of recurrence declined 72% (RR, 0.28; 95% confidence interval [CI], 0.22 to 0.36; P < .001) with each 10-year interval since first episode, and declined 15% (RR, 0.85; 95% CI, 0.71 to 1.01; P = .06) for each 10-year increase in age at first episode. Patients more than 40 years of age were at higher risk of recurrence than younger patients (RR, 1.74; 95% CI, 1.06 to 2.86; P = .03). Clusters of episodes occurred after prolonged disease-free intervals.

CONCLUSIONS

Toxoplasmic retinochoroiditis occurs in clusters over time. Recurrence risk is influenced by patient age and duration of infection.

Active ocular toxoplasmosis in Turkish patients: a report on 109 cases

BACKGROUND

To describe the clinical characteristics of active ocular toxoplasmosis in a large population of Turkish patients.

METHODS

A retrospective study of 109 consecutive patients with active ocular toxoplasmosis seen at the Department of Ophthalmology, Istanbul Faculty of Medicine, from 1995 to 2005.

RESULTS

Fifty-seven patients were female and 52 were male. The mean age at presentation was 25.7 +/- 6.8 years. All patients had positive serum anti-toxoplasma IgG antibodies, but negative IgM antibodies. Preexisting retinochoroidal scars were found in 90 (83%) patients. Central active lesions were significantly more common in eyes without previous involvement than in eyes with preexisting scars (97% vs. 59%). Active lesions were adjacent to a scar in 60 (78.9%) of 76 eyes with preexisting scars. The most common accompanying signs were vitritis (100%), anterior uveitis (49.5%), and periphlebitis (33%). All patients received antiparasitic treatment. Systemic corticosteroids were used in 86% of the patients. Kaplan-Meier survival analysis estimated the cumulative risk of recurrence as 74% at 42 months of follow-up. In 29 (80.5%) of 36 recurrent attacks, active lesions were associated with the scars of the most recent attack. After the resolution of the presenting attack, visual acuity was better than 0.5 in 90%, between 0.1 and 0.5 in 5%, and less than 0.1 in 5% of eyes. Further decrease in visual acuity occurred in only two eyes during our follow-up.

CONCLUSIONS

Most of the patients with active ocular toxoplasmosis have asymptomatic retinochoroidal scars. Proximity of active lesions to the scars, and especially to those of the most recent episode, may have implications for treatment. Although the recurrence risk is high, the visual prognosis is good in most patients with typical ocular toxoplasmosis.

Toxoplasmosis

Toxoplasmosis is the most common cause of posterior uveitis in immunocompetent subjects. The infection can be congenital or acquired. Ocular symptoms are variable according to the age of the subject. For instance, young children present with reduced visual acuity, strabismus, nystagmus, and leucocoria, while teenagers and adults complain of decreased vision, floaters, photophobia, pain, and hyperemia. Toxoplasmic retinochoroiditis typically affects the posterior pole, and the lesions can be solitary, multiple or satellite to a pigmented retinal scar. Active lesions present as grey-white focus of retinal necrosis with adjacent choroiditis, vasculitis, hemorrhage and vitreitis. Cicatrization occurs from the periphery towards the center, with variable pigmentary hyperplasia. Anterior uveitis is a common finding, with mutton-fat keratic precipitates, fibrine, cells and flare, iris nodules and posterior synechiae. Atypical presentations include punctate outer retinitis, neuroretinitis, papillitis, pseudo-multiple retinochoroiditis, intraocular inflammation without retinochoroiditis, unilateral pigmentary retinopathy, Fuchs'-like anterior uveitis, scleritis and multifocal or diffuse necrotizing retinitis. The laboratory diagnosis of toxoplasmosis is based on detection of antibodies and T. gondii DNA using polymerase chain reaction (PCR). Toxoplasmosis therapy includes specific medication and corticosteroids. There are several regimens, with different drug combinations. Medications include pirimetamine, sulfadiazine, clindamycin, trimethoprime-sulphamethoxazol, spiramycin, azithromycin, atovaquone, tetracycline and minocycline. The prognosis of ocular toxoplasmosis is usually good in immunocompetent individuals, as long as the central macula is not directly involved.

Prospective Randomized Trial of Trimethoprim/Sulfamethoxazole versus Pyrimethamine and Sulfadiazine in the Treatment of Ocular Toxoplasmosis

OBJECTIVE

To compare the efficacy of the classic treatment of ocular toxoplasmosis (pyrimethamine, sulfadiazine, and prednisolone) with a regimen consisting of trimethoprim/sulfamethoxazole (co-trimoxazole) plus prednisolone.

DESIGN

Prospective randomized single-blind clinical trial.

PARTICIPANTS

Fifty-nine patients with active ocular toxoplasmosis were randomly assigned to 2 treatment groups: 29 were treated with pyrimethamine/sulfadiazine, and 30 patients received trimethoprim/sulfamethoxazole.

INTERVENTION

Treatment consisted of 6 weeks' treatment with antibiotics plus steroids. Antitoxoplasmosis antibodies (immunoglobulin M [IgM] and IgG) were measured using an enzyme-linked immunosorbent assay.

MAIN OUTCOME MEASURES

Changes in retinochoroidal lesion size after 6 weeks' treatment, visual acuity (VA) before and after intervention, adverse drug reactions during follow-up, and rate of recurrence.

RESULTS

Active toxoplasmosis retinochoroiditis resolved in all patients over 6 weeks' treatment, with no significant difference in mean reduction of retinochoroidal lesion size between the 2 treatment groups (61% reduction in the classic treatment group and 59% in the trimethoprim/sulfamethoxazole group, P = 0.75). Similarly, no significant difference was found in VA after treatment between the 2 groups (mean VAs after treatment were 0.12 logarithm of the minimum angle of resolution [logMAR] [20/25] in the classic treatment group and 0.09 logMAR [20/25] in the trimethoprim/sulfamethoxazole group, P = 0.56). Adverse effects were similar in both groups, with one patient in each suffering from any significant drug side effects. The overall recurrence rate after 24 months' follow-up was 10.16%, with no significant difference between the treatment groups (P = 0.64).

CONCLUSIONS

Drug efficacies in terms of reduction in retinal lesion size and improvement in VA were similar in a regimen of trimethoprim/sulfamethoxazole and the classic treatment of ocular toxoplasmosis with pyrimethamine and sulfadiazine. Therapy with trimethoprim/sulfamethoxazole seems to be an acceptable alternative for the treatment of ocular toxoplasmosis.

Determinants of immunodiagnostic success in human ocular toxoplasmosis

Ocular toxoplasmosis is a local manifestation of systemic infection in which Toxoplasma spreads into the eye, affecting mainly the posterior segment of the eye. Reactivation of the initial retinal condition presumably results from the rupture of quiescent parasitic cysts lying adjacent to pre-existing scars and may secondarily involve the choroid (leading to retinochoroiditis). Although the molecular mechanisms underlying host-parasite interaction are largely unknown, toxoplasmic retinochoroiditis usually remains a local event, and does not necessarily evoke a detectable systemic immune response. Local immunotolerance mechanisms may likewise confound attempts to confirm the clinical diagnosis by serology. Aqueous humour may be analysed for the presence of parasite DNA or of specific antibodies, but the DNA burden therein is low, and a more definite confirmation would require risky puncturing of the vitreous. Laboratory confirmation of the diagnosis is also frustrated by marked individual differences in the time elapsing between the onset of clinical symptoms and the activation of specific antibody production, resulting in a high proportion of false negative results. Whether a delay in the onset of local specific antibody production reflects immunotolerance in cases of congenital - but not obviously in those of acquired - infection remains an open question, but it could account for a relatively low confirmation rate in laboratory tests for local antibody production. Against this background, current diagnostic strategies need to be re-evaluated with a view to future improvements.

The eye in systemic infection

Bacterial, fungal, viral, and parasitic pathogens all cause systemic infection and can spread to the eye. Dissemination of pathogens via the bloodstream can lead to direct involvement of the eye. Visual loss is common in bacterial or fungal endophthalmitis, and toxoplasmosis is a major cause of ocular morbidity and poor vision after congenital or acquired infection. Some infections cause intraocular damage by indirect mechanisms (eg, HIV-mediated immunosuppression), leading to opportunistic infections such as cytomegalovirus infection, periocular nerve involvement due to leprosy, and hypersensitivity reactions in tuberculosis. Eye symptoms might indicate the outcome of an underlying infection, such as development of retinal ischaemia in severe malaria, which is associated with a poor prognosis. Successful outcome for patients with ocular infection depends on close collaboration between clinicians identifying and treating underlying disease, specialist ophthalmic review, and ophthalmic interventional skills (when needed).

Frosted branch angiitis and late peripheral retinochoroidal scar in a patient with acquired toxoplasmosis

PURPOSE

To report a case of acute frosted branch angiitis associated with acquired toxoplasmosis in which a late peripheral chorioretinal scar developed.

RESULTS

A 32-year-old man without systemic symptoms presented with sudden visual loss in his left eye. Examination demonstrated frosted branch angiitis without necrotizing chorioretinitis. Serologic tests showed elevated Toxoplasma gondii-specific immunoglobulin M antibody titers. Antitoxoplasmic therapy and oral steroids healed the ocular inflammation. In a follow-up visit one year later, a peripheral chorioretinal scar was noted.

CONCLUSIONS

Acute frosted branch angiitis without focal necrotizing chorioretinitis can be a manifestation of acquired toxoplasmosis. This could be an important, and sometimes forgotten, sign of the disease.

Ocular manifestations of toxoplasmosis

PURPOSE OF REVIEW

The concepts of toxoplasmosis and its ocular manifestations in humans have thoroughly changed in the past 3 years. This review addresses new epidemiologic data, specifically the occurrence of ocular disease in postnatal infections, and puts the changed views on the frequency and pathogenesis of toxoplasmic ocular manifestations into historical perspective.

RECENT FINDINGS

Newly described clinical presentations are discussed together with their recent diagnostic possibilities. The new data on congenital or postnatal acquisition of infection and their importance for ocular involvement are presented as well as the high prevalence of 79% of recurrent disease in ocular toxoplasmosis, which cannot be prevented by short-term treatments. Recently published analyses of literature showed, unexpectedly, the lack of efficacy of short-term treatments for ocular disease as well as of the long-term prenatal treatments on fetal transmission rate and the severity of congenital disease.

SUMMARY

The recent guidelines for treatment are included together with the up-to-date recommendations for the treatment of ocular toxoplasmosis in the immunosuppressed host.

Cme review: polymerase chain reaction diagnostics for posterior segment disease

The polymerase chain reaction (PCR) is a powerful molecular biologic technique that permits detection and identification of infinitesimal quantities of DNA. It is well suited to the diagnosis of infectious posterior segment ocular inflammatory disease. In this review, the basic biochemistry of PCR, indications for its use, strengths and limitations to the technique, and examples of clinical application of PCR to posterior segment disease will be discussed. Emerging uses of PCR in linking pathogen to disease will also be outlined. After completion of this article, the reader will be able to describe the basic biochemistry and practical application of PCR in the diagnosis of posterior segment inflammatory disease, list the indications, advantages, and disadvantages of the technique, and outline the application of PCR diagnostics to individual differential diagnoses.

Ophthalmic outcomes after prenatal and postnatal treatment of congenital toxoplasmosis

PURPOSE

To describe the ophthalmologic outcomes of cases of congenital toxoplasmosis treated prenatally and postnatally.

DESIGN

Observational case series.

METHOD

Follow-up ophthalmologic examinations of 18 children born to mothers who were infected before 25 weeks gestation were performed concurrently by two ophthalmologists. The infection in these children was first suspected when their mothers seroconverted during gestation. Toxoplasmic infection of the fetus was diagnosed by fetal blood or amniotic fluid analysis. Mothers were treated by a regimen of alternating pyrimethamine-sulfonamides and spiramycin during gestation. Pyrimethamine-sulfonamides treatment was continued from birth to 1 year of age.

RESULTS

The median age of the children was 4.5 years (range 1-11), when the follow-up ophthalmologic examinations were performed. Visual acuity was decreased in only one child, who had extensive bilateral macular and peripheral lesions. A posterior pole scar was noted in four eyes (four children) for whom visual acuity remained normal. Peripheral lesions were observed in nine eyes (five children). Both eyes were normal in 11 of 18 (61%) of the children.

CONCLUSIONS

In these children at a high risk for congenital toxoplasmic retinochoroiditis, a favorable visual outcome was observed in all but one case.

An update on current practices in the management of ocular toxoplasmosis

PURPOSE

To update information that was published by the AMERICAN JOURNAL OF OPHTHALMOLOGY in 1991 about treatment practices for ocular toxoplasmosis by uveitis specialists.

DESIGN

Physician survey.

METHODS

A written questionnaire was distributed to all physician-members (n = 147) of the American Uveitis Society. The questionnaire was modeled after a similar device used to survey uveitis specialists in 1991. Information contained on 96 returned questionnaires was tabulated.

RESULTS

Among 79 respondents who evaluate and manage patients with ocular toxoplasmosis, 15% treat all cases regardless of clinical findings (in contrast to 6% in 1991). The major indications for treatment among other respondents were severe inflammatory responses and proximity of retinal lesions to the fovea and optic disk. The majority of clinical factors considered in five categories (vision, lesion location, lesion size, lesion characteristics, and vitreous inflammatory reaction) were identified to be relative or absolute indications for treatment by a greater proportion of respondents in the current survey than in the 1991 survey. A total of nine drugs (or commercially available combinations) were used in 24 different regimens as treatments of choice for typical cases of recurrent toxoplasmic retinochoroiditis, with the combination of pyrimethamine, sulfadiazine, and prednisone being the most commonly used regimen (29% of respondents).

CONCLUSIONS

Uveitis specialists appear to be more likely to treat patients with ocular toxoplasmosis in 2001 than in 1991. Although the majority of survey respondents adhere to a traditional approach to the management of toxoplasmic retinochoroiditis (a discrete course of systemic drug treatment during active disease using multiple antiparasitic drugs with or without corticosteroids), there is still no consensus regarding the choice of antiparasitic agents for treatment regimens. Survey results provide useful information for treating physicians and for clinical investigators interested in therapy.

Ocular toxoplasmosis: clinical features and prognosis of 154 patients

PURPOSE

To ascertain the clinical features, visual outcome, and recurrence rates of ocular toxoplasmosis (OT) in a large series of patients. To determine the efficacy of various treatment strategies and identify the patients at risk of visual loss.

DESIGN

Retrospective noncomparative observational case series.

PARTICIPANTS

One hundred fifty-four consecutive patients with active lesions of OT (first attack and/or recurrence) were identified in a cohort of 1300 consecutive patients with uveitis. Mean follow-up was 5.8 years.

INTERVENTION

A review of the medical records of 154 patients with active OT.

MAIN OUTCOME MEASURES

Patients were subdivided according to clinical and laboratory criteria. Numerous variables were compared per patient and group, including age and gender distribution, onset and course of infection, clinical ocular features, laboratory data, therapeutic strategies and their outcomes, number of recurrences, complications, final visual acuity, and features associated with poor visual outcome.

RESULTS

Primary retinal lesions were observed in 28% and a combination of active lesions and old retinochoroidal scars in 72% of the patients at first presentation to the ophthalmologist. Mean age at first presentation with an active OT lesion was 29.5 years. Patients with primary OT were older than those with a combination of active lesions and old scars (P < 0.001). Serologic characteristics of the acute phase of systemic infection were found in 11% of the patients. Ocular involvement in these patients was associated with advanced age at onset (P < 0.001) and was characterized by severe intraocular inflammation. Most (82%) of the patients with serologic characteristics of the acute phase of systemic infection had primary lesions (compared with 23% of OT in the chronic phase of systemic infection; P < 0.001). Extensive retinal lesions were more frequently observed during the acute phase of systemic infection (P = 0.02) and in patients with primary OT (P < 0.04). Recurrences, which developed in 79% of all patients followed for more than 5 years, were located predominantly in previously affected eyes (with old scars) in contrast to the sporadic cases of recurrence in the healthy contralateral eye (P < 0.0001). Standard short-term therapeutic modalities had no effect on visual outcome or future recurrence rates. Legal blindness in one or both eyes was confirmed for 24% of the patients. Blindness of both eyes was more frequent in patients with congenital OT (P < 0.001). Risk factors for visual loss included congenital infection, OT manifesting during the acute phase of systemic infection, central location and/or extensive retinal lesions, and the administration of corticosteroids without a shield of antiparasitic drugs.

CONCLUSIONS

Legal blindness in at least one eye developed in 24% of the patients with OT. Recurrences, which developed in 79% of the patients with long-term follow-up, were located predominantly in eyes with toxoplasmic scars. Various short-term therapeutic modalities had no effect on visual outcomes or future recurrence rates, with the exception of a poor visual outcome for patients who received corticosteroids without a shield of antiparasitic drugs.

Reconsidering the pathogenesis of ocular toxoplasmosis

PURPOSE

To review recent observations regarding the sources of Toxoplasma gondii infection and rates of ocular involvement in cases of infection acquired after birth, and to reconcile them with older observations and widely held beliefs about the pathogenesis of ocular toxoplasmosis.

METHOD

A review of pertinent reports from the medical literature.

RESULTS

There are several potential sources and routes of infection, including inhalation of spores and ingestion of contaminated drinking water, that were previously unrecognized. Ocular involvement in cases of acquired infection appears to be more common than heretofore believed. A variety of host and parasitic factors may influence rates of ocular infection and the characteristics of ocular disease.

CONCLUSIONS

The scars from which recurrent toxoplasmic retinochoroiditis arise may be the result of remote, acquired infections in many cases, rather than the residua of congenital infections, as commonly assumed. A better understanding of the epidemiology of T. gondii infection, as well as the host and parasitic factors that influence disease presentation, is important for developing strategies for prevention and management of ocular toxoplasmosis.