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This study shows the connection between the high bacteria settlement of
breed systems for sea products (aquaculture) and the preventing use of
antibiotics in these systems. Different groups of researchers could again
and again prove in their investigations the settlement of aquaculture
through disease-causing bacteria for humans. Among other things thereby
also Cholera bacteria and Salmonella were discovered.
In order to hold these bacteria under check, in intensive breed systems -
in particular with Shrimps and salmon - numerous antibiotics are used. The
materials are used not only due to their preventing effect but also due to
them charged the growth promotion.
Over the quantities of the used antibiotics there are hardly official
numbers. Also the knowledge is extremely limited over their effects to
health and its influence on the environment.
Antibiotic arrears in aquaculture products were proven already several
times. So for instance in shrimps imported to Great Britain, which
different studies prove. In Japan the import of shrimps brought up in
Thailand was even provisionally forbidden at the beginning of the nineties
because of antibiotic arrears. Also in sea organisms from the environment
of commercial fish farms, partly superelevated, antibiotic arrears could to
be proven. Beyond that also bacterial loads in frozen fish were determined.
Potential with antibiotic arrears connected dangers for humans are among
other things allergies, toxic effects and the infestation with resistant,
disease-causing bacteria. The most important antibiotics used in the
aquaculture are used also with humans, which can become a problem because
of the potential formation of resistances. For this reason a set of
antimicrobial medicines are not certified in Europe in that livestock
production. So for instance the antibiotic chloramphenicol can cause anemia
and Stomatitis with humans and lead fast to resistance formation.
The World Health Organization (WHO) admits the fact that the resistance
formation against antibacterially effective materials represents a large
world-wide health problem and recommended therefore already 1997 the use of
all antibiotics, which are used also in the human-medicine, to terminate in
animal breeding.
Also the environmental damage resulting from the application of antibiotics
in the aquaculture is various: E.G. the resistance formation and damage of
organisms belong to these. Also a damage of those organisms, which should
be protected with antibiotics, could be proven in different cases.
Compared with fish from the marine environment the risk of unfavorable
health effects can be increased with aquaculture products under certain
circumstances. In some sections of the world the sales and the use of
antibiotics are not regulated. Imported goods are controlled into the most
important importing countries - with max. a sample per 100 ton the
appropriate error-potential is however relatively high.
Aquaculture - a paradies for bacteria
Important, for humans pathogen, i.e. disease-causing bacteria's groups are
a natural part of the bacteria settlement in the Shrimp aquaculture. This
conclusion is drawn in different studies, in those both during the raising
and after the harvest Salmonella, Vibrio spp. (under it Vibrio cholerae1),
and Listerien2 in Shrimps could be proven. To all three groups belong for
humans pathogen types (BHASKAR belong et aluminium, 1998; BHASKAR et
aluminium, 1995).
v
Thus BHASKAR et al. (1995) determined Salmonella in all during the buildup
and with the harvest pulled Shrimp samples. In Shrimp cultures in Southeast
Asia different trunks of Vibrio cholerae in up to 33% of the examined
samples were determined (DALSGAARD aluminium et, 1995).
Use of antibiotics in the aquaculture
In an executed investigation of the Asian development bank and the NACA
(network OF Aquaculture Centres in Asia Pacific) of 11.000 aquaculture
farms in 1995 there was determined a increased frequency of the antibiotic
use (FAO / NACA / WHO, 1999) in intensive Shrimp farms.
In order to get the bacteria buildup into the grasp, the preventing use of
antibiotics is a widespread method in tropical countries (BATICADOS, &
PACLIBARE, 1992). It is e.g. the only method, to prevent infections with
Vibrosis3 (MORE BECHTELER & HOLLER, 1995).
Antimicrobial substances are often used however not only preventation, but
as growth promoters during the production of animals for the human
consumption (WILLIS et aluminium, 1999). Thus the Malaysian new Strait
Times writes in an article in the year 2000: In order to be able to produce
approximately as large breed salmon as they normally grow in nature and in
order to prevent disease epidemic within the breed cages the aquaculture
industry must feed a set of hormones and antibiotics.
Official numbers over the given antibiotic quantities are hardly available.
In different scientific publications one proceeds from strongly deviating
quantities. And in a research report on behalf of UN, WHO and FAO one
admits: There is a lack of quantitative data over the quantities of the
chemicals used in aquacultures. The only country, for which quantitative
data are available, is Norway (GESAMP, 1997).
No sufficient scientific knowledge
The present knowledge of health and environmental influences of antibiotics
used in aquaculture is small (REILLY & BEETLE KAEFERSTEIN, 1997). When the
aquaculture industry expanded, it took over chemicals, which were
originally developed for the use in other industrial areas, in particular
the agriculture. As a consequence many chemicals, which are commonly used
now in the aquaculture, were never specifically evaluated concerning their
effect on the aquatic environment, in particular the territorial waters,
(GESAMP, 1997). Also most studies over necessary waiting periods after the
use of medicines in the aquaculture were made at types of the moderate
climate zone (GESAMP, 1997).
Scientists even write in a report over the effects of assigned chemicals in
aquaculture: Most of the chemicals mentioned in the report are used
world-wide in the aquaculture, but there is still few or no scientific
information available about the potential environmental effects. (GESAMP,
1997)
Similar largely is the knowledge gap in the area of bacteriological load of
sea products: For the export of Shrimps there prevail strict
bacteriological standards which were imposed by the import nations. These
standards were developed however for sea products of our climate zone. The
microbial populations of products of tropical aquaculture are however
clearly different (BHASKAR et aluminium, 1998).
Import stop because of antibiotic arrears
Antibiotic arrears in aquaculture products were proven again and again:
Between 1993 and 1994 204 to Great Britain imported tiger Shrimps samples
were investigated on antibiotic arrears. In 18 samples antibiotic arrears
were determined (VETERINARY MEDICINE DIRECTORATE, 1994). Also WILLIS et
aluminium (1999) examined imported Shrimps to Great Britain. They even
found antibiotic arrears in 23 from 98 examined samples. Beyond that they
determined bacteria with a significantly higher antibiotic resistance in a
part of the loaded Shrimps. And WILLIS et aluminium (1999) close:
"Therefore it seems reasonable to assume that the presence of antibiotics
in shrimp samples could be correlated with the increased resistance against
these medicaments in of the microflora." This assumption is affirmed by
other aforementioned investigations.
Into Japan one went even so far that the sales of Shrimps drawn up in
Thailand were forbidden because of determined high arrears of
Oxytetracyclin and Oxolin acid in 1990 (PRIMAVERA, 1993; SRISOMBOON &
POOMCHATRA, 1995). Due to this the Japanese government installed a
obligating inspection program for Southeast Asiatic Shrimps (ROSENBERRY,
1991). Thailand developed as reaction guidelines and a monitoring program,
which resulted in significant reductions of antibiotic arrears in exported
Shrimps (MACINTOSH & PHILLIPS, 1992). This new precaution in Thailand
unfortunately did not stretch on the native market. 8,4% of 1461 shrimp
samples, which were bought between October 1990 and 1991 on the Thai
market, were tested positively on Oxytetracycline and Oxolin acid. Among
other things concentrations situated over the prescribed limit values were
determined (SAITANU et aluminium, 1994).
Also in frozen Shrimps from Latin America arrears such as Oxytetracyc LINE
and Oxolin acid were already discovered (BROWN & HIGUERA CIAPARA, 1992).
Not only in the Shrimp breed, but also in the pisciculture antibiotics are
used. Thus arrears were determined by antibiotics also in game fish, which
got caught near European fish farms. In one case the concentrations of the
determined medicine arrears exceeded the maximum limits certified for the
human consumption. Also in crabs, snails and shells which got caught near
fish farms medicine arrears were determined (et aluminium SAMUELSEN, 1992;
LUNESTAD, 1991; BJORKLUND aluminium et, 1990).
On the other hand also bacterial loads in frozen fish were determined,
among them also dangerous types for humans such as Salmonella, E. coli4 and
Staphylococcen5 (IYER & SHRIVASTAVA, 1989).
Effects on humans
The potential dangers connected with antibiotic arrears in food are among
other things:
with antibiotic-resistant bacteria two potential risks for humans are
connected:
The most important antibiotics used in the aquaculture are applied also
with humans. If resistances against these medicines are however formed on
pathogenen bacteria for humans, then they are omitted for the application
with people struck with resistant bacteria. Notes make it reasonable to
assume that human infections with medicine resistant bacteria double the
risk of serious diseases (CROSS-BEAM MOUNTAIN et aluminium, 1987).
For this reason a set of antimicrobial medicines are not certified in
Europe and the USA in livestock production. Apart from the resistance
formation also the assessably and not assessably dangerous effects on
humans and environment are responsible for it. So are e.g. Furazolidon (and
other Nitrofurane) chloramphenicol forbidden in livestock production in the
EU (EEC, 1994).
Reason for it are karzinogen and genotoxic effects (EEC, 1995).
Chloramphenicol can also cause Anaemie6 and Stomatitis7 with humans
(SCHNICK, 1991). With chloramphenicol resistance formation comes very fast.
This is particularily serious, because chloramphenicol is the last
possibility of treatment in the human medicine for acute Salmonella typhi
infections (GESAMP, 1997). Chloramphenicol is ranked therefore among a
group of chemicals used in the aquaculture, which represent inherently a
high level of danger (GESAMP, 1997). For this reason the EU also did
completely without the definition of maximum limits for chloramphenicol
arrears in food of animal origin: The administration of chloramphenicol to
animals, which are used for food production, is completely forbidden in the
entire EU. Because chloramphenicol is however an extremely effective
antibiotic, and it is still used preventative as a disease check in the
aquaculture (MUNNS et aluminium, 1994).
Also against the wide-spread oxytetracyclin resistances already develop, so
that the handlings (in the aquaculture) are ineffective in many cases
(GESAMP, 1997).
It was stated that Oxytetracycline, Furazolidione, Erythromycin and
Kanamycin represent human health risks and can release intestine infects
and allergies (SCHNICK, 1991). Those far spread used Quinolone and
sulfonamide are toxic for humans and can cause serious allergic reactions
(CLEGG et aluminium, 1997).
REILLY & BEETLE KAEFERSTEIN (1997) call arrears of antibiotics caused by
irresponsible sales and abuse of veterinarian medicines in intensive and
semi-intensive aquaculture systems therefore a first-rate problem of food
security.
Also the WHO (World Health Organisation) admits that the resistance against
anti bacterially effective materials is a large world-wide health problem,
which continues to become larger, since these materials lose increasingly
their effectiveness (WHO, 1995). The WHO does therefore not only recommend
controlled and adjusted sales and use of antibiotics, but also the
guarantee that anti-microbial substances are not as a back-up for adequate
hygiene in animal husbandry and in aquaculture. The WHO recommends further
the prohibition of the use of any antibiotics used in the human therapy as
a growth promoter [in animal breeding] (WHO, 1995). 1997 the WHO even
recommended to terminate the use of all antibiotics in animal breeding
which are used also in the human-medicine (from KNIGHT, 1999).
Also many human-scientists regard the uncontrolled application of
antibiotics in the aquaculture industry as a large threat, since thereby
the selection of effective antibiotics in the human-medicine gets reduced
(new Strait Times, Malaysia, 2000).
Effects on the environment
Effects of antibiotics on the environment are:
The toxicity of materials such as Oxytetracycline, Nitrofuran and a number
of others can be shown as their application on the Philippines caused
deadly consequences and morphologic deformations in exactly those Shrimp
larvae, it should prevent (PRIMAVERA, 1993). Also it was shown that the use
of synthetic medicines, in particular from chloramphenicol and Oxolin acid,
can reduce larva growth in the breeding station and set natural defense
mechanisms out of strength (KAMONPORN SHARKSHARK SHARK, 1995).
Also for Quinolon-Enrofloxacin an impairment of marine organisms was
proven: Although even apparent from small toxicity, it increases the
toxicity of other contamination, in particular PCBs8, for fish (WILLIAMS
aluminium et, 1997).
Oxytetracycline are diminished rather slowly in the fish body. Their
so-called radioactive half-life is at 125-144 days (et al. SAMUELSEN,
1992). They arrive therefore with the fish excrement in the sea water and
settle on the bottom of the sea. There they remain - separated from
sunlight - long time preserved, without disintegrating. Thus it is
relatively probable for Oxytetracycline that they return into the food
cycle (et al. HEEKTOEN, 1995).
The wide-spread use and abuse of antibiotics, in particular in breed
systems, led to the development of multiple resistances at microbe
populations, which have connections with the Shrimp farming (BROWN, 1989).
In general these resistances cover a larger area and exist for a much
longer time than provable concentrations of the antibiotics themselves
(HUSEVAG et aluminium, 1991).
Result
REILLY & BEETLE KAEFERSTEIN (1997) determine recapitulatorily: Compared
with fish from the marine environment the risk of unfavourable health
effects can be higher with aquaculture products under certain
circumstances. The reason for this is their origin from inland and coastal
ecological systems (REILLY & BEETLE KAEFERSTEIN, 1997).
The naturally high bacteria load of the intensive aquaculture ponds makes
the use of antibiotics essential. Reason for it is that so far still no
vaccines were developed for many diseases occurring in the tropical
aquaculture. In particular the immune system of the Shrimps is understood
only insufficiently, what obstructs the development of vaccines (GESAMP,
1997).
Although there are laws, which forbid the administration of antibiotics
during periods before the harvest in order to avoid arrears in the Shrimp
bodies, they are continued to feed often up to the harvest (MORE BECHTELER
& HOLLER, 1995). Still 1995 KAMONPORN SHARKSHARK SHARK wrote that there is
no specific legislation for the use of therapeutic medicines and chemicals
in Thailand. And CHOO states that in some sections of the world the sales
and the use of antibiotics are not regulated (1994).
There are import controls to important consumer regions like the EU, the
USA and Japan. These are however afflicted with numerous problems: Thus
until recently salmon was examined only for arrears of Oxolin acid when
imported into the USA and Shrimps only on chloramphenicol (WESTON, 1996).
With each arrears-investigation program however the most urgent problem is
the trade volume with aquaculture products. Most import monitoring programs
analyse at a maximum one sample per 100 tons. "Such an inspection frequency
is not adequate, in order to guarantee that sea products with arrears
values in heights without permission do not reach the consumer (GESAMP,
1997)."
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