A new worm infiltrating the human cornea: A report of 3 cases

Authors: MCBURNEY-LIN, S. - Duke University; KHORRAM, D - Marianas Eye Institute; GEE, S. - Steven Gee, Md Inc; Hoberg, Eric; KLASSEN-FISCHER, M.K. - The Joint Pathology Center (JPC); NEAFIE, R.C. - The Joint Pathology Center (JPC)

Submitted to: Journal of Ophthalmology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2017
Publication Date: 1/5/2018
Citation: Mcburney-Lin, S., Khorram, D., Gee, S., Hoberg, E.P., Klassen-Fischer, M., Neafie, R. 2018. A new worm infiltrating the human cornea: A report of 3 cases. Journal of Ophthalmology. 9:124-130. doi:10.1016/j.ajoc.2018.01.013
DOI: https://doi.org/10.1016/j.ajoc.2018.01.013

Interpretive Summary: A diverse assemblage of zoonotic parasitic nematodes (parasites transmissible from animals to humans) has been documented in ocular infections in people, and involve both fully developed nematodes or larval stages. Ocular parasites -- including protozoa, nematodes, cestodes, and trematodes -- are well-documented, and ocular parasitosis has been found to be significantly more common in regions with favorable environmental factors and poor sanitary conditions. In these regions, ocular parasitosis can be endemic in the canine and feline populations, as well as in a range of wildlife species including other mammals or birds, providing a breeding ground from which arthropod vectors can transmit parasites to humans. In a collaboration linking expertise of medical professionals, federal pathologists, and the APDL, we report 3 patients from the island of Saipan, in the southwestern Pacific, who presented with corneal stromal nematodes between 1997 and 2009; it is unusual to discover live worms in introcular locations. The nematodes we describe do not match any previously reported corneal worms or metazoan parasites that trigger uveitis and may represent a new species or a previously undescribed zoonotic infection. Most of the species in encompassing those reported in ocular infections, belong to the Family Onchocercidae. There are many vertebrate parasites in the Onchocercidae that have not yet been shown to cause zoonotic eye infections in humans, but which may have the potential to do so. Overall there are about 70-80 genera of onchocercids partitioned across 8 subfamilies including the Onchocercinae which contains the greatest taxonomic diversity for species circulating in birds or mammals. For example, species of at least 16 genera of filarioid nematodes, in addition to those of Pelecitus, have been described as parasites of wild birds alone. Because of the rarity of this infection and the fact that it has not been described previously, it is likely a zoonotic infection. The mode of transmission is unknown. Resolution of the source and identity of these nematodes can be based on early recognition of infection, and collection of archival specimens from the Southwest Pacific suitable for detailed comparative morphological study and comparative molecular-based analyses. We provide new and potentially critical information that should be of importance in the medical and parasitological communities in recognizing the occurrence of these nematodes and the potential for human infection.

Technical Abstract: Purpose: To characterize a new species of parasitic nematode that triggers uveitis. Observations: Three previously healthy, relatively young people each contracted a corneal stromal nematode that, upon surgical removal and examination of one of the worms, did not match any known nematodes. Clinical ocular findings included corneal opacification, visible corneal worms, conjunctival injection, and uveitis. Conclusions: The three patients presented here represent a previously undescribed parasitic infection of the cornea by an unidentified nematode. These findings may represent a previously unrecognized zoonotic infection from wildlife sources and potentially a newly documented nematode requiring description. Future clinical findings regarding this newly described nematode are needed to further develop our understanding of the disease.