Anti Antibiotics

Cabello, F. (2006) Heavy use of prophylactic
antibiotics in aquaculture: a growing problem for human and animal health and for
the environment. Environmental
Microbiology 8 (7), 1137–1144 doi:10.1111/j.1462-2920.2006.01054.x

This paper says that a reduction of the use of antibiotics
in aquaculture must be enforced globally to include the large industry in other
countries such as China, Japan and Chile. Prophylactic antibiotics have been
used extensively in aquaculture because the fish in aquaculture are prone to
disease. The manipulations to increase production are stressors that lower the
immune system. The increased population densities, crowding of farming sites in
coastal waters, lack of sanitary barriers increases the spread of disease.

A number of studies have shown that there are an increased
number of antibiotic resistant bacteria around aquaculture sites. Horizontal
gene transfer from these areas is occurring, passing on resistant determinants
onto terrestrial animal and human pathogens! High concentrations of viruses in
seawater could mean that transduction is one of the transfer mechanisms. Human
and animal bacteria come into contact with the aquaculture bacteria through
untreated sewage and agricultural and industrial wastewater being dumped in the
sea. The use of manure and other agricultural residues as fish feed is
widespread and this amplifies the problem.

Studies
have shown that these transfers can and do happen. For example molecular
epidemiology studies on A. Salmonicida have shown that plasmids,
that contain class 1 integrons found in human pathogenic bacteria, and are able
to transfer with high frequency to E. Coli and Salmonella, are
responsible for the resistance to trimethoprim, sulfonamide and streptomycin in
this bacterium. Antibiotic resistance of Salmonella entericas type
caused several outbreaks of salmonella in humans and animals in Europe and the
USA, and probably originated in aquaculture settings of the Far East.
This
pathogen could have been spread by fishmeal as has happened with the Salmonella
Agona that originated in Peru several years ago. V. cholerae of the
Latin American epidemic of cholera that started in 1992 appeared to have
acquired antibiotic resistance as a result of coming into contact with
antibiotic-resistant bacteria selected through the heavy use of antibiotics in
the Ecuadorian shrimp industry. Also a quinolone-resistant
determinant has been recently detected in Japan and in Chile in the emergent
human pathogen Vibrio parahaemolyticus, a marine bacterium transmitted
to humans by the ingestion of raw shellfish and that is most likely able to
exchange genetic information with other bacteria of the marine environment.

An
additional effect of the excessive use of antibiotics in aquaculture is the
presence of residual antibiotics in the product. This will cause
antibiotic-resistant selection in the consumers gut and alter their gut
microbiota in a potentially bad way. Consumers may also get allergic reactions
to the toxic antibiotic residuals. Another problem is the antibiotics in the
environment having an effect on the microbes present altering the ecosystem at
its base with potential big consequences. Situations that impact fish and human
health may be promoted such as algal blooms and anoxic environments.

It has been
economically feasible to develop a productive aquaculture industry without
excessive use of prophylactic antibiotics. Sanitary measures and the use of
vaccines or probiotics keep the fish healthy. The use of quinolones has been totally

restricted in aquaculture in industrialized countries. However China and Chile

for example continue to
use tones of these antibiotics a year. This will impact the globe since these
antibiotics get carried in water currents for huge distances and the resistant
diseases will spread as people travel between countries.