Two days after returning from 9 months of travel in southern India and Sri Lanka, a 45-year-old German man sought treatment at a hospital because of acute speech problems. During the previous 5 weeks, the patient had experienced a persistent headache and creeping eruptions of 5–7 cm on the left arm, which moved from the upper arm to the back of the hand. Physical examination found a tender nodule on the left hand, with a diameter of ≈2 cm, as well as signs of aphasia and apraxia. Cranial magnetic resonance imaging (MRI) indicated cortical and subcortical signal changes in the left frontal region, with signs of meningeal inflammation but no signs of acute ischemia, bleeding, or venous occlusions. Laboratory investigations showed increased cerebrospinal fluid (CSF) protein levels and increased CSF cell counts of 1,500/µL with a high proportion of eosinophils (40%), as well as increased blood leukocyte counts of 12,000/µL (9% eosinophils). Serologic testing showed high antibody titers against Dirofilaria antigen and moderate titers against Strongyloides antigen, but no significant antibody titers were found against other helminth antigens tested, including Toxocara, Cysticerca, Schistosoma, Fasciola, or Paragonimus species. Antihelminthic treatment with albendazole (400 mg 2×/d) and concomitantly with methyl-prednisolone (20 mg 2×/d) was initiated, and the patient recovered rapidly.

Figure

Figure. Images of the adult female Dirofilaria repens worm removed from a subcutanous nodule of the patient. A) Macroscopic view of sections of the worm in saline in a petri dish. Two...

Removal of the nodule 10 days after the initiation of drug therapy and subsequent histologic examination showed eosinophilic infiltrates and sections of a gravid female nematode that contained large numbers of microfilariae with obtuse cephalic ends and a filiform tail without nuclei. The adult worm showed several characteristics resembling those of D. repens (2,5,9,10) (Figure). The cuticula was 20 µm thick, multilayered, transverse-striated, and contained large numbers of external longitudinal ridges. Cross-sections showed a well-developed musculature of the coelomyarian type and a worm diameter of ≈550µm. To further confirm the diagnosis of D. repens infection, DNA of the worm was extracted (11) and panfilarial PCR was performed that targeted the mitochondrial 12S rRNA gene (11). Sequence analysis of the 509-bp PCR product and comparison with sequences deposited in GenBank showed the organism had the highest similarity of ≈97% to D. repens and of 90% to D. immitis (data not shown; the sequence has been submitted to the GenBank database with the accession no. GQ292761).

We report a human D. repens infection with concomitant meningoencephalitis. Complications associated with the central nervous system were most likely because of the worm infection as the CSF contained high numbers of eosinophilic granulocytes, the patient recovered rapidly after initiation of antihelminth and anti-inflammatory treatment, and MRI largely excluded other causes such as acute ischemia, bleeding, or venous occlusions. Other helminth infections, in particular, cysticercosis, were unlikely, according to a panel of negative serologic tests. In contrast to other D. repens infections in humans, which are usually restricted to the skin, in this case the patient showed blood eosinophilia and high antibody titers to Dirofilaria antigen, which indicate a generalized response to the parasite. Moreover, the worm removed from the skin nodule of the patient had developed to maturity and contained microfilariae. These microfilariae were likely responsible for the generalized immune response as well as for the involvement of the central nervous system. Microfilariae that cross the blood-brain barrier and cause neurologic symptoms in humans or animals have been previously described for other species such as Meningonema peruzzi and D. immitis (12,13). In the case presented here, infection was most likely acquired in India or Sri Lanka, 2 regions where D. repens is endemic (7,8,14,15). Notably, genetic analysis of the highly conserved mitochondrial 12S rRNA gene showed a 3% deviation from D. repens sequences deposited in public databases, which suggests that different D. repens strains vary considerably. Whether specific variants are more likely to develop to maturity and cause generalized disease in humans deserves further investigation.