Diffuse Unilateral Subacute Neuroretinitis with Visualized Ocular Larva Migrans Shane McEntire M.D., Suzie T. Nemmers M.D., Jason Sorell D.O., John D. Campagna M.D. MPHTM, Natasha Nemeth M.D. Tripler Army Medical Center, University of Hawaii The views expressed in this poster are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense or the U.S. Government. None of the authors have any commercial or financial interests.

Purpose To describe the uncommon findings of a visualized larva attributed to Toxocara canis in ocular larva migrans.

Background Human T. canis infections have been reported in nearly all parts of the world, primarily in temperate and tropical areas where dogs are popular household pets. Young children are at highest risk because of their unsanitary play habits and tendency to place fingers in the mouth. T. canis larvae secrete large amounts of immunogenic glycosylated proteins which induce immune responses that lead to eosinophilia and polyclonal and antigen-specific immunoglobulin E (IgE) production. There are 3 major clinical syndromes associated with human toxocariasis: visceral larva migrans, ocular larva migrans, and covert toxocariasis.

Background The ocular disease may appear in a number of ways, the most common being in the form of a dense white granuloma in the posterior pole or retinal periphery where the larva has encysted. Patients may have a more marked inflammation that may simulate DUSN and endophthalmitis, probably due to massive antigen release by dying organisms. The pathology of toxocariasis consists of granuloma formation with a predominance of eosinophils. The actual identification of a larva may require multiple sections of the tissue. Visualization on retinal exam is uncommon.

Case A 33 yo man who returned from Iraq noted blurred vision and photophobia in his left eye. Exam noted a uveitis with granuloma keratic precipitates, a retinal granuloma of the left eye, and choroidal retinal scars of both eyes possibly attributed to toxoplasmosis. He was treated initially with Pred-forte. Due to failure to respond, lab analysis was performed which showed a positive result for Toxocara canis, eosinophilia, and negative for toxoplasmosis. Subtenon steroid injections were initiated followed by oral steroids and albendazole 400 mg bid for five days. After regression of the retinal granuloma, a nonmotile nematode larva was visualized.

OS

Visualized larva of T. canis Overlay demonstrating location

Surrounding granuloma

Discussion Eyes that have active inflammation require treatment with systemic or periocular corticosteroids. If the eye disease is not responsive to corticosteroids, parasitic infection should be considered. Parasitic infection with Toxocara canis is uncommon and visualization of larva is difficult to discern. Toxocariasis can present as neuroretinitis thereby delaying diagnosis.

References Glickman LT, Schantz PM: Epidemiology and pathogenesis of zoonotic toxocariasis. Epidemiol Rev 1981; 3:230. Walls KW, Schantz PM, ed. Immunodiagnosis of Parasitic Diseases, Vol 1, Helminthic Diseases, New York: Academic Press; 1986: Tropical Medicine and Emerging Infectious Diseases, 8th ed. Chapter 112 Cohen & Powderly: Infectious Diseases, 2nd ed.