Human Infections with Pseudoterranova cattani Nematodes, Chile

Abstract

To the Editor: Anisakidosis is an emerging foodborne zoonosis caused by nematode larvae of the Anisakinae subfamily, which includes the genera Anisakis, Pseudoterranova, and Contracecum (1). In natural cycles, anisakid larvae are transmitted to marine mammals or piscivorous birds when they eat raw saltwater fish or squid. In the human incidental host, larvae attach to the mucosa of the gastrointestinal tract, causing clinical features ranging from asymptomatic carriage to severe abdominal pain with complications, such as gastric perforation (2). Microscopical diagnosis is hampered by the lack of distinguishing morphologic characteristics in larval stages (1). Recently, molecular genetic techniques have shown that the main species, Anisakis simplex and Pseudoterranova decipiens, are in fact species groups with distinct geographic and biologic characteristics (3,4). The P. decipiens complex consists of at least 6 sibling species (Technical Appendix Table). We report 4 human infections with P. cattani diagnosed during 2012–2014. The case-patients were adults 22–59 years of age; 2 were female, and all lived in Santiago, Chile. Additional anamnestic and clinical data were available for 3 patients: all spontaneously regurgitated the parasites without having other gastrointestinal complaints. All 3 reported eating ceviche, a dish made of raw marine fish marinated in lemon juice. One patient reported a tingling sensation and coughs before the expulsion of a highly motile larva (Video). This patient was awaiting oral surgery after a bicycle accident and had eaten the last raw fish dish 2 weeks previously. Initially, parasites were identified by morphologic criteria. Larvae were 20 mm long, were of whitish to reddish color, and had 3 anterior lips (Technical Appendix Figure 1). Because of the presence of an anteriorly directed cecum (Technical Appendix Figure 2), they were assigned to Pseudoterranova species.

To the Editor: Anisakidosis is an emerging foodborne zoonosis caused by nematode larvae of the Anisakinae subfamily, which includes the genera Anisakis, Pseudoterranova, and Contracecum (1). In natural cycles, anisakid larvae are transmitted to marine mammals or piscivorous birds when they eat raw saltwater fish or squid. In the human incidental host, larvae attach to the mucosa of the gastrointestinal tract, causing clinical features ranging from asymptomatic carriage to severe abdominal pain with complications, such as gastric perforation (2). Microscopical diagnosis is hampered by the lack of distinguishing morphologic characteristics in larval stages (1). Recently, molecular genetic techniques have shown that the main species, Anisakis simplex and Pseudoterranova decipiens, are in fact species groups with distinct geographic and biologic characteristics (3,4). The P. decipiens complex consists of at least 6 sibling species (Technical Appendix Table). We report 4 human infections with P. cattani diagnosed during 2012–2014. The case-patients were adults 22–59 years of age; 2 were female, and all lived in Santiago, Chile. Additional anamnestic and clinical data were available for 3 patients: all spontaneously regurgitated the parasites without having other gastrointestinal complaints. All 3 reported eating ceviche, a dish made of raw marine fish marinated in lemon juice. One patient reported a tingling sensation and coughs before the expulsion of a highly motile larva (Video). This patient was awaiting oral surgery after a bicycle accident and had eaten the last raw fish dish 2 weeks previously. Initially, parasites were identified by morphologic criteria. Larvae were 20 mm long, were of whitish to reddish color, and had 3 anterior lips (Technical Appendix Figure 1). Because of the presence of an anteriorly directed cecum (Technical Appendix Figure 2), they were assigned to Pseudoterranova species.