For further molecular identification, DNA samples were extracted by using a DNeasy Blood and Tissue Kit (QIAGEN K.K., Tokyo, Japan). The rRNA gene containing 2 internal transcribed spacer (ITS) regions was amplified by PCR using primers NC5 and NC2, as previously described (5). PCR products were sequenced by using a BigDye Terminator Cycle Sequencing Kit (Applied Biosystems Inc., Foster City, CA, USA) on an automated sequencer (ABI3100, Applied Biosystems). Sequence similarities were determined by a BLAST search of DDBJ (http://blast.ddbj.nig.ac.jp/top-j.html). The GENETYX-WIN program version 7.0 (Software Development Co., Tokyo, Japan) facilitated sequence alignment and comparison. Within the 4 ITS sequences of amplicons obtained, all were 100% identical, and alignment with the other P. cattani sequence differed only in 1 nt. ITS sequences of 2 isolates are available in GenBank (accession nos. KF781284 and KF781285). All P. cattani sequences showed a previously described deletion of ≈14 bases (Table), which is not observed in other members of the P. decipiens species complex (5).

This study identified P. cattani as a parasite capable of infecting humans. The definitive natural host of this parasite is the South American sea lion, Otaria byronia. At least 4 species of coastal fish were described as intermediate or paratenic hosts, including popular Chilean food fish species, such as Merluccius gayi, Genypterus maculatus, and Cilus gilberti (6). The spectrum of species causing human pseudoterranovosis is uncertain because most cases were reported as P. decipiens (sensu lato) or Pseudoterranova sp. Only recently, 1 case of P. azarasi infection has been documented in a patient from Japan (7). Although comparative studies are lacking, Pseudoterranova larvae seem to be less invasive and cause milder symptoms than Anisakis larvae (2,8). In the cases reported here, larvae were spontaneously expelled without further symptoms, except in 1 patient who reported the typical feature of noninvasive pseudoterranovosis, also described as “tingling throat syndrome” (8), a foreign body sensation accompanied by cough and retching. In Chile, ≈30 human cases have been reported, all diagnosed as P. decipiens or Pseudoterranova sp. by morphologic criteria (9,10). Most patients described mild oropharyngeal complaints and cough. More severe manifestations similar to parasitic pharyngitis caused by Fasciola hepatica or Linguatula serrata seem to be absent, although 1 patient had symptoms of asphyxia (9). The extent to which these cases in Chile were caused by P. cattani is uncertain because molecular diagnosis was not performed. The length of stay and location within the human gastrointestinal tract of Pseudoterranova larvae are unknown, but as indicated by 1 case in our report, lack of symptoms for up to 2 weeks is possible.

These cases demonstrate that P. cattani is an incidental human parasite causing oropharygeal pseudoterranovosis. To better understand the epidemiology and clinical relevance of these emerging fishborne zoonotic infections, molecular diagnostic techniques need to be more widely applied, especially in regions where raw fish is part of the regular diet, such as in many parts of South America.