Study of toxoplasmosis and toxocariasis in patients suffering from ophthalmic disorders using serological and molecular methods

Abstract

Introduction: Toxoplasma gondii is an intracellular protozoan parasite that can cause ocular toxoplasmosis with most complications such as retinal detachment. Toxocara parasite, round worm, found in dogs and cats appears as larva migrans in humans can cause serious ocular complications such as debilitating vision loss.In Khuzestan province, southwest of Iran, T. gondii infection has been reported to be significant but toxocariasis was rare. However, the frequency of ocular toxoplasmosis and toxocariasis has not been studied in this area. The aim of this study was to evaluate the ocular toxoplasmosis and ocular toxocariasis using serological and molecular methods.

Method: In this case control study, 310 patients were identified by ophthalmologist as ocular toxoplasmosis and then 5 cc of venous blood samples were taken from each of them. Serum samples and buffy coat were prepared and ELISA was used to detect IgG and IgM anti-Toxoplasma antibodies and the molecular PCR was used to detect Toxoplasma DNA parasite in buffy coats. ELISA test was used to detect of IgG anti-Toxocara antibodies.

Results: Totally, for ocular toxoplasmosis, 130 (41.93%) of 310 patients were positive by ELISA, of them 121 (39%) IgG positive and nine (2.9%) IgM positive were diagnosed. Of 121 cases with IgG⁺, 119 (98.35%) were diagnosed with high IgG avidity indicating chronic phase of the infection. For ocular toxocariasis evaluation, antibodies against Toxocara were not detected in any of the samples. By PCR molecular method, 11 out of 310 patients (3.54%) had T. gondii DNA in the blood. In control, in total, 21 cases were detected positive by serology method, which showed a significant difference with the results of the case group(P < 0.05).By PCR method, only three cases showed positive which also indicated significant difference with result of case group (3 vs 9) (P < 0.05). In the control group, also no anti-toxocara antibodies were found.

Conclusion: It can be concluded that T. gondii in Khuzestan province as the etiologic agent of ocular toxoplasmosis and physicians should consider diagnostic methods for identifying the infection when they visit the patients.

Keywords: ELISA; Ocular; PCR; Toxocariasis; Toxoplasmosis.

Fig. 1

B1 nested-PCR analysis of seropositive samples from ocular toxoplasmosis. Lane 1, DNA size marker; Lanes 1–3, Clinical samples; Lane 4, Positive control