Because a PCR was available, histopathologic analysis was not conducted. Morphologic features or sex could not be determined. The worm specimen was subjected to multiplex PCR for D. repens and D. imitis using an equimolar combination of general and species-specific primers: Diro_12S_F (5′-GTTCCAGAATAATCGGCTA-3′), Diro_12S_R (5′-ATTGACGGATGGTTTGTACC-3′), D. immitis_F (5′-TTTTTACTTTTTTGGTAATG-3′), and D. repens_R (5′-AAAAGCAACACAAATAAAA-3′). The cytochrome c oxidase subunit 1 (COX1) region was amplified by using primers Fil_COX1F (5′-GCTTTRTCTTTTTGGKTTACTTTT-3′) and Fil_COX1R (5′-TAGTRTCATAAAAAGAAGTATTAAA-3′) (5).

Although the specimen was identified as a D. repens worm, Sanger sequencing of the COX1 and 12S rDNA PCR products was performed by using the BigDye Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems, https://www.thermofisher.com) and the Genetic Analyzer 3130XL (Applied Biosystems). Sequences of 12S rRNA and COXI genes obtained were deposited in GenBank (accession nos. MT984272 and MT984209).

Phylogenetic analysis of the 12S rRNA (MT984272) and COX1 (MT984209) sequences obtained from the isolate was performed by using the maximum-likelihood method with 1,000 bootstrap replications and MEGA X version 7 (https://www.megasoftware.net). Both the 12S rRNA and the COX1 sequences obtained from the human isolate were in the same cluster with Dirofilaria sp. genotype Hongkong and were separated from other Dirofilaria species (5,6) (Appendix Figure 2). Peripheral blood smears were negative for microfilaria. Symptoms of the patient resolved slowly after worm extraction and initiation of treatment with steroids.

Migrating worms in humans might cause a variety of clinical problems, which could be caused by mechanical effects or immune responses. Intraocular parasites might induce severe damage to various structures in the eye. Literature on eosinophilic meningitis and concomitant ocular parasites is limited. Clinical manifestations of eosinophilic meningitis are usually attributed to the severe inflammatory response incited by migrating worms, even though they are rarely demonstrated in vivo. Eosinophilic meningitis caused by Angiostrongylus cantonensis worms has been frequently reported in the Asia–Pacific region (7). Dirofilaria infection rarely results in eosinophilic meningitis (1,2).

Poppert et al. reported a case of D. repens infection, which was subsequently identified as Dirofilaria sp. genotype Hongkong, which caused subcutaneous infection and concomitant eosinophilic meningoencephalitis in a traveler returning from Kerala, India, and Sri Lanka to Germany (8). Subconjunctival infection with Dirofilaria sp. genotype Hongkong has also been reported in a patient returning to Austria after a 7-week stay in India (9). A recent study from Kerala, India, suggested that most of D. repens infections reported from southern India have the Dirofilaria sp. Hongkong genotype (10).

Demonstration of a live, intraocular worm and its subsequent identification as Dirofilaria sp. genotype Hongkong by using sequencing added a new dimension to this case of eosinophilic meningitis. Infection with the Dirofilaria sp. Hongkong genotype, blood eosinophilia, and eosinophilic meningitis are the 3 strikingly similar features between our case-patient and Poppert et al. (8), suggesting that Dirofilaria sp. genotype Hongkong might induce a more systemic eosinophilic reaction than D. repens.

Sequencing using panfilarial primers might help characterize most filarial species. Such an approach might clarify the etiopathogenesis of eosinophilic meningitis, leading to newer therapeutic and preventive strategies.