Fish as Hosts of Vibrio cholerae

Abstract

Vibrio cholerae, the causative agent of pandemic cholera, is abundant in marine and freshwater environments. Copepods and chironomids are natural reservoirs of this species. However, the ways V. cholerae is globally disseminated are as yet unknown. Here we review the scientific literature that provides evidence for the possibility that some fish species may be reservoirs and vectors of V. cholerae. So far, V. cholerae has been isolated from 30 fish species (22 freshwater; 9 marine). V. cholerae O1 was reported in a few cases. In most cases V. cholerae was isolated from fish intestines, but it has also been detected in gills, skin, kidney, liver and brain tissue. In most cases the fish were healthy but in some, they were diseased. Nevertheless, Koch postulates were not applied to prove that V. cholerae and not another agent was the cause of the disease in the fish. Evidence from the literature correlates raw fish consumption or fish handling to a few cholera cases or cholera epidemics. Thus, we can conclude that V. cholerae inhabits some marine and freshwater fish species. It is possible that fish may protect the bacteria in unfavorable habitats while the bacteria may assist the fish to digest its food. Also, fish may disseminate the bacteria in the aquatic environment and may transfer it to waterbirds that consume them. Thus, fish are reservoirs of V. cholerae and may play a role in its global dissemination.

Virulence‐associated factors in Vibrio cholerae non‐O1/non‐O139 and V. mimicus strains isolated in ornamental fish species

“…They therefore maintained that ornamental fish served as vectors of these microorganisms. Also Halpern and Izhaki () confirmed the role of marine and freshwater fish to disseminate these bacteria in the aquatic environments. Our results showed that there is no evidence as to whether any ornamental fish species is a better reservoir or vector of one of the two sister species compared to another, but it is clear that fish species originating from Asia were more likely to serve as vectors of field strains carrying virulence factors than the ones isolated during diagnostic testing.…”

Wild waterfowl as potential vectors of Vibrio cholerae and Aeromonas species

“…regarding a fish disease in the ponds next to where we collected the waterbirds. V. cholerae O1 and non-O1 have been isolated from different fish species (reviewed in [32]). V. cholerae and Aeromonas are inhabitants of fish and chironomids [4,18] consumed by waterbirds, which may be how V. cholerae and Aeromonas enter the waterbirds' intestine.…”

The Vibrio cholerae type VI secretion system can modulate host intestinal mechanics to displace gut bacterial symbionts

“…V. cholerae can form biofilms on chitinous substrates, such as the exoskeleton of crustaceans (8), and can colonize the gut of birds and fish, which may promote transmission in aquatic environments and perhaps contribute to human disease outbreaks (9,10). Within a human host, a complex set of signaling systems and external cues regulate colonization and disease factors, such as biofilm formation, chemotaxis-guided flagella, toxin-coregulated pili, several adhesins, and cell shape features, to ensure access of the microbe to the intestinal surface (11,12).…”