AUTHOR=Hounmanou Yaovi Mahuton Gildas , Mdegela Robinson H. , Dougnon Tamegnon Victorien , Madsen Henry , Withey Jeffrey H. , Olsen John E. , Dalsgaard Anders 

TITLE=Tilapia (Oreochromis niloticus) as a Putative Reservoir Host for Survival and Transmission of Vibrio cholerae O1 Biotype El Tor in the Aquatic Environment

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01215

DOI=10.3389/fmicb.2019.01215

ISSN=1664-302X

ABSTRACT=<p>Studies have reported the occurrence of <italic>Vibrio cholerae</italic> in fish but little is known about the interaction between fish and toxigenic <italic>V. cholerae</italic> as opposed to phytoplankton, which are well-established aquatic reservoirs for <italic>V. cholerae</italic>. The present study determined the role of tilapia (<italic>Oreochromis niloticus</italic>) as a reservoir host for survival and transmission of <italic>V. cholerae</italic> in aquatic environments. Three experiments were performed with one repetition each, where <italic>O. niloticus</italic> (∼2 g) kept in beakers were inoculated with four <italic>V. cholerae</italic> strains (5 × 10<sup>7</sup> cfu/mL). Firstly, infected tilapia were kept in stagnant water and fed live brine shrimp (<italic>Artemia salina</italic>) larvae daily. Secondly, infected tilapia were kept without feeding and water was changed every 24 h. Thirdly, infected tilapia were fed and water was renewed daily. Infected tilapia and non-infected controls were sacrificed on days 1, 2, 3, 7, and 14 post-inoculation and <italic>V. cholerae</italic> were enumerated in intestinal content and water. Another experiment assessed the transmission of <italic>V. cholerae</italic> from infected to non-infected tilapia. The study revealed that El Tor biotype <italic>V. cholerae</italic> O1 and <italic>V. cholerae</italic> non-O1 colonized tilapia intestines and persisted at stable concentrations during the second week of the experiment whereas the Classical biotype was undetectable after 1 week. In stagnant water with feeding, <italic>V. cholerae</italic> counts dropped to 10<sup>5</sup> cfu/ml in water and from 10<sup>7</sup> to 10<sup>4</sup> cfu/intestine in fish after 14 days. When water was renewed, counts in water decreased from 10<sup>7</sup> to 10<sup>3</sup> cfu/ml and intestinal counts went from 10<sup>6</sup> to 10<sup>2</sup> cfu/intestine regardless of feeding. All strains were transmitted from infected to naïve fish after 24 h of cohabitation. Tilapia like other fish may play an essential role in the survival and dissemination of <italic>V. cholerae</italic> O1 in aquatic environments, e.g., the seventh pandemic strains mostly. In this study, tilapia were exposed to high concentrations of <italic>V. cholerae</italic> to ensure initial uptake and follow-up studies with lower doses resembling natural concentrations of <italic>V. cholerae</italic> in the aquatic environment are needed to confirm our findings.</p>