Baylisascaris Procyonis Induced Diffuse Unilateral Subacute Neuroretinitis in New York City

Abstract

Diffuse unilateral subacute neuroretinitis (DUSN) secondary to raccoon roundworm (Baylisascaris procyonis) infection has been reported in rural and suburban areas of North America and Europe with extant raccoon populations. Here, we present a case of Baylisascaris-induced DUSN from the densely populated borough of Brooklyn in New York City and alert urban ophthalmologists to consider this etiology even in areas not typically thought to be associated with endemic risk factors. Infected raccoons also occur in urban settings, and urban patients may be exposed in surrounding areas. Most patients with Baylisascaris ocular larva migrans-DUSN will not have concomitant neurologic disease; this fact and larval neurotropism are both misconceptions regarding this infection.

Update on Baylisascariasis, a Highly Pathogenic Zoonotic Infection

“…They may be hard to detect, and it might take repeated examinations before they are seen. In one case, the parasite was not appreciated ophthalmoscopically but was subsequently seen in fundus photographs (31). The larvae are large (1,500 to 2,000 long by 60 to 70 m in diameter) compared with the other common types of nematode larvae that may occur in the eye, including Toxocara spp.…”

“…procyonis is not a neurotropic nematode; only a low percentage of larvae (on the order of 5% to 7%) migrate into the CNS of paratenic hosts (1,18,25). Migration of B. procyonis to brain and eye tissues is considered to be accidental, a consequence of somatic migration and dissemination (1,25,31). However, this is the most important biological aspect of clinical infections in humans and animals.…”

“…It is understood that when the burden of larvae is low, i.e., when few larvae have entered the CNS, clinical NLM does not manifest or is covert (1,2,6,7,55). In contrast, clinical OLM can occur when only a single larva migrates into the eye, based on the sensitivity of that organ (2,31,91). The majority of B. procyonis infections involve only a few larvae and remain neurologically asymptomatic (2, 6, 7).…”

“…Nematode larvae that cause DUSN are typically separated into two size ranges, "small" (500 to 700 m in length) and "large" (1,500 to 2,000 m in length), and Baylisascaris is considered the primary etiological agent of the lat- OLM-DUSN shortly after they obtained pet raccoons (74,75). Cases have occurred in residents or hunters in rural areas (22,109,112) and in suburban areas (36,38,40,105) as well as in a highly urban area (New York City) (31,114). The latter case is unique in that the patient did not present with typical DUSN lesions but instead presented with advanced granulomatous OLM with retinal detachment similar to that seen in toxocariasis.…”

“…DUSN is characterized by vison loss, papillitis, vitritis, and recurrent crops of gray-white retinal lesions. Later, progressive vison loss, optic nerve atrophy, retinal vessel narrowing, and diffuse retinal pigment epithelial degeneration develop (2,22,31,75,108). Other than the characteristic lesions, a diagnosis is established by direct visualization of the intraocular parasites, and one key aspect is their size.…”