Great cormorants (Phalacrocorax carbo) as potential vectors for the dispersal of Vibrio cholerae

Abstract

Vibrio cholerae is the cause of cholera, a devastating epidemic and pandemic disease. Despite its importance, the way of its global dissemination is unknown. V. cholerae is abundant in aquatic habitats and is known to be borne by copepods, chironomids and fishes. Our aim was to determine if fish-eating birds act as vectors in the spread of V. cholerae by consuming infected fish. We determined the existence of V. cholerae in the microbiome of 5/7 wild cormorants’ intestine. In three of these V. cholerae-positive wild cormorants, the presence of a gene for cholera toxin (ctxA) was detected. We subsequently tested eight captive, hand-reared cormorants, divided into two equal groups. Prior to the experiment, the feces of the cormorants were V. cholerae-negative. One group was fed exclusively on tilapias, which are naturally infected with V. cholerae, and the other was fed exclusively on goldfish or on koi that were V. cholerae-negative. We detected V. cholerae in the feces of the tilapia-fed, but not in the goldfish/koi-fed, cormorants. Hence, we demonstrate that fish-eating birds can be infected with V. cholerae from their fish prey. The large-scale movements of many fish-eating birds provide a potential mechanism for the global distribution of V. cholerae.

Wild waterfowl as potential vectors of Vibrio cholerae and Aeromonas species

“…cholerae from their tilapia fish prey, which is naturally inhabited by V . cholerae . Jubirt et al .…”

“…Pathogenic strains of V. cholerae serogroup O1 were identified from two waterfowl species: Ardea herodias (great blue heron) and Larus delawarensis (rige-billed gull); the authors could not explain these findings, and the article was forgotten for more than 20 years [9] until Halpern et al [10] suggested that waterbirds might be vectors for V. cholerae. Recently, we have demonstrated that great cormorants (Phalacrocorax carbo) can be infected with V. cholerae from their tilapia fish prey, which is naturally inhabited by V. cholerae [11]. Jubirt et al [12] fed great egrets (Arda alba) with catfish contaminated by highly virulent A. hydrophila and then isolated it from the great egrets' faeces.…”

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).…”

Environmental Reservoirs of Vibrio cholerae: Challenges and Opportunities for Ocean-Color Remote Sensing

“…Aquatic birds, especially migratory ones, play a significant role in the transportation of V. cholerae via two main routes. In the first route, birds may eat contaminated fish or other contaminated organisms in one pond and shed the pathogens in another area, as demonstrated by the presence of pathogenic V. cholerae in intestinal and fecal samples of aquatic birds [73,[87][88][89]. In the second route, chironomids and copepods, which are known to be reservoirs of V. cholerae, attach externally to the feather and feet of birds and facilitate the transport of pathogens [73].…”