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Background: Human toxocariasis, caused by Toxocara canis, T. cati, and T. vitulorum of dogs, cats and ruminants respectively, is recognized as an important zoonotic infection worldwide. The typical clinical syndromes of toxocariasis in humans are ocular larva migrans (OLM) and visceral larva migrans (VLM). The most commonly affected sites of OLM are the peripheral retina and/or vitreous humor. In Sri Lanka, there is a dearth of information on prevalence of ocular infection in our population. Therefore, the present study was carried out to determine the prevalence of Toxocara antibodies in suspected OLM patients and to describe demographic factors and clinical manifestations of seropositive patients. A total of 250 clinically suspected ocular toxocariasis cases referred by consultant eye surgeons to the Department of Parasitology, University of Peradeniya were studied between the years 1995 to April 2015., Methods: Data (age, sex, fundoscopic findings) were gathered from the referral letters. Each serum sample was subjected to Toxocara excretory - secretory antigen ELISA (TES - ELISA)., Results: Out of the 250 cases, 155 (62%) were seropositive. The age range of the seropositive cases was 1 to 78 years with the mean age of 27 years. The highest seropositivity (25/155) was observed within the age group of 10 to 14 years. The most frequent clinical presentation of seropositive OLM cases were unilateral reduced vision and red eye. The other symptoms include tearing, photophobia and leukokoria. A high proportion of seropositive OLM cases had uveitis (34.19%) followed by reduced vision (21.94%), vitritis (12.9%) and choroiditis (7.74%). However none of these clinical manifestations were significantly associated with TES-ELISA seropositivity except vitreits (X 2  = 8.557, p = 0.003)., Conclusion: In conclusion, the results of this study showed high seroprevalence of toxocariasis among clinically suspected OLM cases confirming the toxoplasmic etiology. This high rate of Toxocara seropositivity in ocular patients should alert ophthalmologists in Sri Lanka to include toxocariasis in the differential diagnosis of ocular diseases presented with the symptoms and signs stated above.

Survival of parasitic helminths within a host requires immune evasion and excretory/secretory (ES) proteins may contribute to this process. Eosinophils are important effector cells in immunity of mice to the nematode Nippostrongylus brasiliensis and eosinophilic interleukin-5 transgenic (IL-5 Tg) mice are highly resistant to the earliest stages of primary infections. In contrast, Toxocara canis is largely resistant to eosinophils, with viable larvae encysted in tissues often surrounded by these and other leucocytes. The aim of this study was to investigate whether T. canis ES (TES) proteins inhibit eosinophil-dependent resistance to N. brasiliensis . Mouse serum pre-treated with TES had reduced capacity to mediate the adherence of leucocytes to N. brasiliensis infective-stage larvae (L3) and this correlated with reduced complement C3 deposition on the parasite. TES did not inhibit eosinophil survival or eotaxin-dependent eosinophil migration in vitro . Cellular inflammation and eosinophil degranulation in the skin in response to injection of L3 was also not impaired by TES. However, when TES was included with L3 in an inoculum given to IL-5 Tg mice, a greatly increased number of parasites migrated to the lung. This suggests that the early eosinophil-dependent resistance in these mice was suppressed, by mechanisms yet to be determined. [ABSTRACT FROM AUTHOR]