Given the importance of angiostrongyliasis as an emerging infectious disease of humans, companion animals, and wildlife, the current study focused on the transmission dynamics of first- and third-stage larvae of the parasitic nematode, Angiostrongylus cantonensis. The migration of infective larvae and their subsequent distribution within the Lymnaeidae snail, Bullastra lessoni, were investigated over time using microscopic examination of histological sections and fresh tissue. Snails were divided into four anatomical regions: (i) anterior and (ii) posterior cephalopedal masses, (iii) mantle skirt and (iv) visceral mass. The viability of free-swimming third-stage larvae, after their release from snail tissues, was evaluated in vitro by propidium iodide staining and infectivity by in vivo infection of Wistar rats. Snails were sequentially dissected over time to assess the number and anatomical distribution of larvae within each snail and hence infer their migration pathway. Herein, ongoing larval migratory activity was detected over 28 days post-infection. A comparison of infection rates and the larval distribution within the four designated snail regions demonstrated a significant relationship between anatomical region and density of infective larvae, with larvae mostly distributed in the anterior cephalopedal mass (43.6 ± 10.8%) and the mantle skirt (33.0 ± 8.8%). Propidium iodide staining showed that free-swimming third-stage larvae retained viability for between 4 and 8 weeks when stored under laboratory conditions. In contrast to viability, larval infectivity in rats remained for up to 2 weeks only. Knowledge gained from the current work could provide information on the development of new approaches to controlling the transmission of this parasite.

Poster session 3, September 23, 2022, 12:30 PM - 1:30 PM Presently, long-read high-throughput sequencing technology has been started applying in the medical mycology field instead of common Sanger sequencing. With its capability to sequence nucleic acid among the large region compared to Sanger sequencing, this technology can detect and analyze both inter- and intra-species sequence variation in internal transcribed spacer (ITS), a fungal house-keeping region, resulting in high accurate fungal identification. However, to set up the long-read high-throughput sequencing technology for fungal identification is quite challenging because of several factors related to the accuracy including the variation position error. So, in this study, we summarize the tip to correct the variation position error in applying long-read high-throughput sequencing technology for fungal identification that we have learnt in the preliminary laboratory setting using the 8 clinical isolates of yeast: Candida albicans (n = 2), C. tropicalis (n = 1), C. glabrata (n = 1), Trichosporon asahii (n = 2), Pichia kudriavzevii (n = 1), Cryptococcus neoformans var. grubii (n = 1). Based on the recruited strains, we found that self-assembling reference sequence generated from raw data of reading by using an auto-program named Canu causes the size-inflated sequence, a larger size calculated as 22.83 ± 7.56% than it should be, resulting in the shift of variation position. This error can be corrected by the alignment process of the reference sequence with the known sequence, both size and position, prior to doing the raw read alignment. The advantage of this process could correct not only for position shifting caused by the analysis process but also the random error generated from nanopore system. To validate this correction protocol, more samples are needed for further study.