Hypolobocera guayaquilensis (Decapoda: Pseudothelphusidae): A New Crab Intermediate Host of Paragonimus mexicanus in Manabí Province, Ecuador

Abstract

To determine that Paragonimus sp. is actively transmitted in a tropical area of the Pacific region of Ecuador where human cases of pulmonary paragonimiasis have recently been documented, a total of 75 freshwater crabs were collected from 2 different streams in the Pedernales area of Manabí Province, Ecuador. All collected crabs were identified as Hypolobocera guayaquilensis based on morphological characteristics of the male gonopods. The hepatopancreas of each crab was examined by compressing it between 2 glass plates followed by observation under a stereomicroscope. Excysted Paragonimus metacercariae were detected in 39 (52.0%) crabs and their densities varied from 1 to 32 per infected crab. There was a positive relationship between crab size and metacercarial density. Sequences of the second internal transcribed spacer region of the ribosomal RNA gene of the Paragonimus metacercariae obtained in this study were identical to those of Paragonimus mexicanus deposited in the DDBJ/EMBL/GenBank database. Thus, the present study is the first to confirm that the crab species H. guayaquilensis is the second intermediate host of P. mexicanus in Manabí Province, Ecuador. Because this crab might be the possible source of human infections in this area, residents should pay attention to improper crab-eating habits related with a neglected parasitic disease, i.e., paragonimiasis.

General overview of the current status of human foodborne trematodiasis

“…One from Ecuador could be assigned as P. ecuadoriensis Voelker and Arzube, 1979 (once synonymized with P. mexicanus by Vieira et al in 1992), and two possible new species (or subspecies) groups included one from Chiapas, Mexico and San José, Guatemala and the other from Veracruz, Mexico (Iwagami et al, 2003;López-Caballero et al, 2013). Freshwater crabs, Hypolobocera aequatorialis, H. chilensis and H. guayaquilensis, Pseudothelphusa dilatata, P. nayaritae, P. propinqua and P. terrestris carry the metacercariae (Blair et al, 1999a;Calvopiña et al, 2018). Raw crabs with vegetables and lemon juice is the main infection source for Peruvians (Nakamura-Uchiyama et al, 2002), and ceviche that contains uncooked crustacean meat is an important source for Mexicans (Procop, 2009).…”

Liver fluke infections by Amphimerus sp. (Digenea: Opisthorchiidae) in definitive and fish intermediate hosts in Manabí province, Ecuador

“…Given the morphological similarities of metacercariae of the Opisthorchiidae and Heterophyidae [10,35] and the lack of studies of liver or intestinal fish-borne trematodes in Ecuador, we only analyzed metacercariae with appropriate morphology (see above). We followed a similar approach as described by Calvopiña et al 2018 [37], including DNA extraction, polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (RFLP), and DNA sequencing. In brief, we extracted DNA from individual metacercariae using the QIAamp DNA Micro Kit (Qiagen, Stanford, California, United States).…”