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Cholera, a devastating diarrheal disease that caused several global pandemics in the last centuries, may share some similarities with the new COVID-19. Cholera has affected many populations in history and still remains a significant burden in developing countries. The main transmission route was thought to be predominantly through contaminated drinking water. However, revisiting the historical data collected during the Copenhagen 1853 cholera outbreak allowed us to re-evaluate the role of drinking-water transmission in a city-wide outbreak and reconsider some critical transmission routes, which have been neglected since the time of John Snow. Recent empirical and cohort data from Bangladesh also strengthened the dynamic potentiality of other transmission routes (food, fomite, fish, flies) for transmitting cholera. Analyzing this particular nature of the cholera disease transmission, this paper will describe how the pattern of transmission routes are similar to COVID-19 and how the method of revisiting old data can be used for further exploration of new and known diseases.

Studies have reported the occurrence of Vibrio cholerae in fish but little is known about the interaction between fish and toxigenic V. cholerae as opposed to phytoplankton, which are well-established aquatic reservoirs for V. cholerae. The present study determined the role of tilapia (Oreochromis niloticus) as a reservoir host for survival and transmission of V. cholerae in aquatic environments. Three experiments were performed with one repetition each, where O. niloticus (∼2 g) kept in beakers were inoculated with four V. cholerae strains (5 × 107 cfu/mL). Firstly, infected tilapia were kept in stagnant water and fed live brine shrimp (Artemia salina) 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 V. cholerae were enumerated in intestinal content and water. Another experiment assessed the transmission of V. cholerae from infected to non-infected tilapia. The study revealed that El Tor biotype V. cholerae O1 and V. cholerae 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, V. cholerae counts dropped to 105 cfu/ml in water and from 107 to 104 cfu/intestine in fish after 14 days. When water was renewed, counts in water decreased from 107 to 103 cfu/ml and intestinal counts went from 106 to 102 cfu/intestine regardless of feeding. All strains were transmitted from infected to naive fish after 24 h of cohabitation. Tilapia like other fish may play an essential role in the survival and dissemination of V. cholerae O1 in aquatic environments, e.g., the seventh pandemic strains mostly. In this study, tilapia were exposed to high concentrations of V. cholerae to ensure initial uptake and follow-up studies with lower doses resembling natural concentrations of V. cholerae in the aquatic environment are needed to confirm our findings.

Paper presented at the 4th Strathmore International Mathematics Conference (SIMC 2017), 19 - 23 June 2017, Strathmore University, Nairobi, Kenya. Cholera is a highly infectious disease caused by the bacterium Vibrio cholerae. Its spread is a product of both social and environmental factors. Past and recent cholera outbreaks in Kenya haveled to deaths and hospitalisation. In this study, we investigate the impact of media coverage on the spread of cholera using a mathematical model whose formulation is based on a system of ordinary differential equations. Positivity and boundedness of solutions are established to ensure that the model is well posed. The basic reproduction number is derived using the next generation matrix approach and used in analysing the local stability of the disease free equilibrium. sensitivity analysis of the basic reproduction number with respect to the model parameters is carried out to access the relative impact of each parameter on the spread of the disease. The results show that increasing the efficacy of media coverage is vital in controlling the spread of cholera.

The human pathogen Vibrio cholerae exhibits two distinct lifestyles: one in the aquatic environment where it often associates with chitinous surfaces and the other as the causative agent of the disease cholera. While much of the research on V. cholerae has focused on the host-pathogen interaction, knowledge about the environmental lifestyle of the pathogen remains limited. We recently showed that the polymer chitin, which is extremely abundant in aquatic environments, induces natural competence as a mode of horizontal gene transfer and that this competence regulon also includes the type VI secretion system (T6SS), a molecular killing device. Here, I discuss the putative consequences that chitin-induced T6SS activation could have on intestinal colonization and how the transmission route might influence disease outcome. Moreover, I propose that common infant animal models for cholera might not sufficiently take into account T6SS-mediated interbacterial warfare between V. cholerae and the intestinal microbiota.