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. 2021 Apr 8;72(7):1117-1123.
doi: 10.1093/cid/ciaa245.

First European Haplotype of Echinococcus multilocularis Identified in the United States: An Emerging Disease?

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First European Haplotype of Echinococcus multilocularis Identified in the United States: An Emerging Disease?

Louis B Polish et al. Clin Infect Dis. .

Abstract

Background: Echinococcus multilocularis is one of the most severe and lethal parasitic diseases of humans, most often reported in Europe and Asia. Only 1 previous case has been documented in the contiguous United States from Minnesota in 1977. European haplotypes have been identified in carnivores and domestic dogs as well as recently in patients in western and central Canada.

Methods: We used immunohistochemical testing with the monoclonal antibody Em2G11 and a species-specific enzyme-linked immunosorbent assay affinity-purified antigen Em2, as well as COX1 gene sequencing.

Results: Using pathology, immunohistochemical staining, specific immunodiagnostic testing, and COX1 gene sequencing, we were able to definitively identify E. multilocularis as the causative agent of our patient's liver and lung lesions, which clustered most closely with the European haplotype.

Conclusions: We have identified the first case of a European haplotype E. multilocularis in the United States and the first case of this parasitic infection east of the Mississippi River. Given the identification of this haplotype in Canada, this appears to be an emerging infectious disease in North America.

Keywords: Echinococcus multilocularis; Echinococcus multilocularis COX gene; alveolar echinococcus spectrum of disease; liver masses; parasitic infection.

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Figures

Figure 1.
Figure 1.
Axial T2-weighted magnetic resonance imaging of the liver showing a large hypointense hepatic mass with a central region of high signal (asterisk), suggesting fluid.
Figure 2.
Figure 2.
Coronal T1-weighted postcontrast magnetic resonance imaging through the posterior lungs shows a lobulated mass (arrow) in the left lower lobe.
Figure 3.
Figure 3.
Liver biopsy demonstrating large areas of necrosis associated with infiltrating parasitic cysts (hematoxylin and eosin stain, ×200) (left image). The cysts are lined with a thin laminated layer, which is strongly highlighted with Gomori methenamine silver (upper right image) and periodic acid-Schiff (lower right image) stains. No protoscoleces are seen, as is common for human cases of alveolar echinococcosis.
Figure 4.
Figure 4.
Portion of resected lung nodule showing similar-appearing parasitic cysts within a necrotizing granuloma (hematoxylin and eosin stain, ×400). This biopsy was obtained following albendazole therapy.
Figure 5.
Figure 5.
Immunohistochemical staining of the section shown in Figure 2 using the monoclonal antibody Em2G11, which recognizes a glycoprotein in the laminated layer of the larval stage of Echinococcus multilocularis. Strongly positive red staining is seen in association with the parasitic cysts and focally in the surrounding necrotic regions, marking shed particles of the laminated layer known as small particles of E. multilocularis.
Figure 6.
Figure 6.
Echinococcus multilocularis phylogenetic relationships and haplotype classification based on COX1 sequencing. A, Phylogenetic tree of all reported E. multilocularis COX1 sequences with > 1400 bp. Bootstrap values (trials = 1000; seed = 111) are depicted. Sequence from the Vermont patient is shown in red. B, Echinococcus multilocularis haplotype by nucleotide polymorphism location found in this patient’s isolate, compared with the most similar European (E), Asian (A), and North American (N) haplotypes. Most sequenced isolates are from wildlife, and the diversity of countries represented in the phylogenetic tree does not reflect clinical disease burden in the respective countries. The IUPAC representation of sequences is shown, with R denoting ambiguity between A and G. Dots represent identical nucleotides at the given position with this isolate. Aside from ambiguity at 822, the Vermont patient’s E. multilocularis haplotype is identical to E2, E4, and E5 by COX1 sequencing. Abbreviation: IUPAC, International Union of Pure and Applied Chemistry.

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