Call for society to be aware of Vibrio cholerae from
aquatic animals
Cholera is an ancient and widespread infectious disease, mainly
manifested as severe vomiting, diarrhea, water loss, and high mortality.
It belongs to the group of international quarantine infectious diseases,
and Vibrio cholerae is the pathogen of human cholera. Since 1817,
there have been seven global cholera pandemics, which have caused
hundreds of millions of human deaths. The cause of these cholera
epidemics is highly complex; how it spreads globally and the reason for
seasonal epidemic peaks in epidemic areas remains unclear. Most sporadic
outbreaks of cholera are related to aquatic products or related water
bodies.
V. cholerae belongs to the Vibrio family, which can be
divided into 139 serogroups. Of these, O1 and O139 can cause a human
cholera epidemic. O1 and O139 V. cholerae can cause cholera
mainly because they carry cholera toxin, which can activate adenylate
cyclase in intestinal epithelial cells, resulting in
Cl- ions’ secretion and impairment of the absorption
of Na+ ions. Water enters the intestinal cavity with
ions, causing severe watery diarrhea, eventually leading to human death.
However, non-O1 and non-O139 V. cholerae may carry other
virulence factors, which are widely distributed in the water
environment. These can cause gastrointestinal inflammation and
extraintestinal infections such as meningitis, sepsis, and wound
infection.
V. cholerae widely exists in various water bodies and has been
reported to infect aquatic animals. V. cholerae , in particular
non-O1 and non-O V. cholerae , can infect fish, shrimp, and other
aquaculture animals. However, O1 and O139 V. cholerae have also
been reported in aquatic animals, such as the O1 group found in
tilapia(Hounmanou et al., 2019) and the O139 group found in loach and
shrimp(Joseph et al., 2015; Chen et al., 2016). Therefore, V.
cholerae is an important zoonotic bacterium that can be enriched in
aquatic animals, both in the non-O1 and non-O139 groups, and the O1 and
O139 groups, which can cause cholera outbreaks. Although there have been
no reports of cholera outbreaks in humans caused by O1 and O139 V.
cholerae from aquatic animals, there is a possibility of a future
cholera outbreak. V. cholerae can cause disease in aquatic
animals, suggesting it can grow and reproduce in aquaculture water and
aquatic animals. The aquaculture water and aquatic animals may serve as
a culture medium, allowing V. cholerae to obtain the conditions
for large-scale reproduction, forming a large population, enrichingV. cholerae . This can lead to animal disease and pollute the
water body, appearing as diffusion. Therefore, aquatic animals and the
water environment are an important carrier of V. cholerae , making
these a potential source of V. cholerae transmission(Malka &
Ido, 2017). V. cholerae from aquatic animals may be transmitted
through three routes, birds, food, and environmental pollution. In
China, due to the open aquaculture mode of aquatic animals, birds eat
small fish and shrimp, resulting in birds carrying V. choleraeand causing transmission(Laviad-Shitrit, Izhaki, & Halpern, 2019).
Additionally, farmers sell diseased aquatic animals at low prices, and
people may eat aquatic animals with V. cholerae , possibly causing
infection if unripe or raw aquatic products are eaten. Third, the
treatment scheme of aquatic animal breeding wastewater is not perfect,
and wastewater is prevalently discharged directly into nature without
treatment. Water used for aquatic animal breeding and its polluted
environment may be exposed to people, leading to V. choleraeinfection.
In recent years, most of the V. cholerae infected by aquatic
animals are of the non-O1 and non-O139 groups, which also cause great
harm to humans. In fact, 42.4% of the cases are caused by eating
aquatic animals(Li et al., 2020). Although Chinese researchers detectV. cholerae in aquatic products, there is no strict quarantine
system, and there are some policy loopholes. In terms of aquaculture
wastewater, although strict discharge standards have been formulated,
due to extensive aquaculture, lax supervision results in inevitable
environmental pollution, leading to the spread of pathogens. Current
research indicates that O1 and O139 V. cholerae were found in
fish and shrimp, a dangerous signal of a highly critical situation.
Wild animals have always been considered ”natural reservoirs of
pathogens”, as many severe human infectious diseases, such as SARS and
Ebola, are transmitted from wild animals. The New Coronavirus was also
possibly derived from wild animals (Leroy, Gouilh, & Collection, 2020).
The open culture mode of aquatic animals is similar to the living
environment of wild animals. This is mostly uncontrollable and may
become a natural reservoir of pathogens. It can spread rapidly through
water sources, birds, and aquatic products, which is more dangerous than
terrestrial animals. Therefore, the public health department should pay
attention to the zoonosis, formulate corresponding prevention plans,
improve the supervision measures of aquatic products, improve the
treatment of aquaculture wastewater, and strictly implement the
discharge standard of aquaculture wastewater, to avoid disaster. We hope
that society will pay attention to the relationship between V.
cholerae and humans.
Yang Yibin 1 Ai Xiaohui1Chen Yuhua2
1Yangtze River Fisheries Research Institute, Chinese
Academy of Fishery Sciences, China
2Department of Gastroenterology, Zhongnan Hospital of
Wuhan University, China
Correspondence
Chen Yuhua, Department of Gastroenterology, Zhongnan Hospital of Wuhan
University, Wuhan 430227, China. Email: 510026437@qq.com