Exposing the Barcoding Void: An Integrative Approach to Study Snail-Borne Parasites in a One Health Context

Abstract

Trematodes are snail-borne parasites of major zoonotic importance that infect millions of people and animals worldwide and frequently hybridize with closely related species. Therefore, it is desirable to study trematodiases in a One Health framework, where human and animal trematodes are considered equally important. It is within this framework that we set out to study the snail and trematode communities in four artificial lakes and an abattoir in Zimbabwe. Trematode infections in snails were detected through multiplex PCR protocols. Subsequently, we identified snails by sequencing a partial mitochondrial cytochrome c oxidase subunit I (COI) fragment, and trematodes (adults from the abattoir and larval stages detected in snails) using COI and nuclear rDNA markers. Of the 1,674 collected snails, 699 were molecularly analyzed, in which we identified 12 snail and 19 trematode species. Additionally, three parasite species were sampled from the abattoir. Merely four trematode species were identified to species level through COI-based barcoding. Moreover, identification of members of the superfamilies Opisthorchioidea and Plagiorchioidea required a phylogenetic inference using the highly conserved 18S rDNA marker, as no related COI reference sequences were present in public databases. These barcoding challenges demonstrate a severe barcoding void in the available databases, which can be attributed to the neglected status of trematodiases. Adding to this, many available sequences cannot be used as different studies use different markers. To fill this gap, more studies on African trematodes, using a standardized COI barcoding region, are desperately needed.

Invasive snails, parasite spillback, and potential parasite spillover drive parasitic diseases of Hippopotamus amphibius in artificial lakes of Zimbabwe

“…B Sampling sites at Lake Kariba; figure adapted from Carolus et al [ 5 ]. C Sampling site at Mwenje, a temporary puddle adjacent to the main reservoir located at S 17°14′ 47.9″ E 31°01′ 07.7″; figure adapted from Schols et al [ 41 ]. D Sampling site 13 at Lake Kariba.…”

“…Five COI sequences (~ 400 bp) were ~ 99% identical to a Diplostomidae sp. collected from the adjacent reservoir by Schols et al [ 41 ] (“GenBank: MT994279”), two did not provide sequencing results of sufficient quality and the remaining four amplicons (424 bp–428 bp, “GenBank: MT909546-MT909548 and MT909550”) showed a pairwise distance below 2% to the two adult F. nyanzae specimens from Kariba (results not shown, 408 bp). The ITS1 - 5.8S - ITS2 amplification and sequencing was successful for 10 out of the 11 Fasciola sp.…”

“…To further elucidate its phylogenetic position and identify it to species level, future research should study the morphological characteristics such as the tegumental surface and the genital pore through scanning electron microscopy [ 60 ] and transversal sections [ 57 ], respectively. Furthermore, an integrative taxonomic approach could be applied to generate reference sequences for the missing amphistome families [ 26 , 41 ]. For the Hippo stomach fluke type 2, sampled from the Asian snail R. aff .…”

Simultaneous genotyping of snails and infecting trematode parasites using high‐throughput amplicon sequencing

“…While all snails were identified to species level, the taxonomic resolution of the identification of their trematode was lower, sometimes only up to family level. This lack of specificity is mostly linked to a lack of reference sequences for African trematodes in the NCBI databases (see Schols et al, 2020). In addition, the high al., 2009), insects (Parkin & Butlin, 2004;Sword et al, 2007), anthozoans (Rodriguez-Lanetty & Hoegh-Guldberg, 2002), crustaceans (Harris & Crandall, 2000) and teleost fishes (Xu et al, 2009).…”

“…While all snails were identified to species level, the taxonomic resolution of the identification of their trematode was lower, sometimes only up to family level. This lack of specificity is mostly linked to a lack of reference sequences for African trematodes in the NCBI databases (see Schols et al, 2020). In addition, the high Radix natalensis (n = 7) 42.9 100.0 100.0 (100.0) 42.9 (14.3) molecular diversity within this group complicates the design of general primers that would amplify all trematode species (Moszczyńska et al, 2009;Vanhove et al, 2013).…”