Tilapia () as a Putative Reservoir Host for Survival and Transmission of O1 Biotype El Tor in the Aquatic Environment.

Studies have reported the occurrence of in fish but little is known about the interaction between fish and toxigenic as opposed to phytoplankton, which are well-established aquatic reservoirs for . The present study determined the role of tilapia () as a reservoir host for survival and transmission of in aquatic environments. Three experiments were performed with one repetition each, where (∼2 g) kept in beakers were inoculated with four strains (5 × 10 cfu/mL). Firstly, infected tilapia were kept in stagnant water and fed live brine shrimp () 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 were enumerated in intestinal content and water. Another experiment assessed the transmission of from infected to non-infected tilapia. The study revealed that El Tor biotype O1 and 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, counts dropped to 10 cfu/ml in water and from 10 to 10 cfu/intestine in fish after 14 days. When water was renewed, counts in water decreased from 10 to 10 cfu/ml and intestinal counts went from 10 to 10 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 O1 in aquatic environments, e.g., the seventh pandemic strains mostly. In this study, tilapia were exposed to high concentrations of to ensure initial uptake and follow-up studies with lower doses resembling natural concentrations of in the aquatic environment are needed to confirm our findings.