Diffuse Unilateral Subacute Neuroretinitis Syndrome: Probable Cause

To the Editor. —In a recent article in theArchivesGass and Braunstein¹presented evidence that diffuse unilateral subacute neuroretinitis (DUSN) is caused by at least two different nematodes, neither of which isToxocara canis. Unidentified intraocular nematodes in the size range 400 to 1,000 μm long were associated with the disease in 12 patients primarily from the southeastern United States, and nematodes 1,500 to 2,000 μm long were seen in six patients from the upper midwestern United States. The largest diameters of the worms were stated as approximately 1/20 their length, or about 20 to 50 μm and 75 to 100 μm, respectively. Both size measurements, but especially those of the larger nematodes, match the size range of larvae ofBaylisascarissp, common intestinal roundworms of lower carnivores, including raccoons and skunks. In our opinion,Baylisascarislarvae, especiallyBaylisascaris procyonisfrom raccoons, are a probable cause of many