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One of the best proven ways to prevent
pathologies is to create immunity in the
animal. With more than 200 years to
back up their efficacy, vaccines have
helped to prevent and in some cases
eliminate many disorders in humans,
farm animals and family pets.
Regarding aquaculture, the evolution has
been a bit slower. If we look at fish, the
first vaccine for salmonids was licensed
in the US in 1976. Since then, the use of
immunoprophylaxis in fish has expanded
to other places and species.
In the case of penaeid shrimp things are
a bit more complicated. Unlike more
complex vertebrates, whose immune
systems depend heavily on adaptive,
antigen-specific responses such as anti-
bodies and T cell receptors, invertebrate
defenses use generic, innate immunity.
Therefore, they lack any form of immu-
nological memory similar to that found in
jawed vertebrates. Vaccinating inverte-
brates, such as shrimp, should conse-
quently be an ineffective management
strategy resulting in no more than short-
lived, non-specific immune stimulation.
The shrimp innate defense system con-
sists of cellular and humoral components
working in coordination for the detec-
tion/elimination of pathogens potentially
hazardous to the host. In both cases
hemocytes play an important role. In
cellular defense hemocytes are responsi-
ble for phagocytosis, encapsulation and
nodule formation. On the other hand,
humoral response consists on the activa-
tion and release of molecules stored
within hemocytes, such as anticoagulant
proteins, agglutinins, phenoloxidase en-
zymes, antimicrobial peptides, pattern
recognition proteins, lectins, toll recep-
AQUAFEED::ADVANCES IN PROCESSING & FORMULATION from Aquafeed.com Vol. 7 Issue 3
Feeding shrimp
FOCUS
By Àlvaro Ortiz, Product Manager, Norel
One of the biggest problems related to intensification in
animal production has been disease. Farm animals suffer
from a great variety of infectious diseases that have been
traditionally controlled by the use of pharmaceuticals. But as
zootechnology has advanced, prevention has gained more
importance, moving from a reactive to a preventive strategy.
Modulation of penaeid
shrimp immune
system as a strategy
to control disease
Ph
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tors, protease inhibitors, etc.
The first organ involved in crustacean
immune system is the cuticle, it works as
the first physical barrier, and it contains
antimicrobial substances.
If the pathogens cross the outer defense,
hemocytes participate in the inactivation
of invading organisms, and regulate
different physiological functions i.e., exo-
skeleton hardening, cuticle damage heal-
ing, coagulation, carbohydrate metabo-
lism, and protein/amino acid transporta-
tion and storage.
Three different types of hemocytes are
present in the shrimp: hyaline, semi-
granular, and granular.
Hyalinocytes (5-15% of circulating hemo-
cytes or CE) are small non-refractive
cells, with a small nucleus relative to
their cytoplasm, which have few or no
cytoplasmic granules. The primary role of
these cells is related to clotting and phag-
ocytosis.
Granulocytes (10-20% of CE) have the
smallest nucleus and a high number of
cytoplasmic granules. Granulocytes dis-
play phagocytic activity and store en-
zymes as prophenoloxidase (proPo), lyso-
zyme, phosphatase, esterase, phospho-
lipase, peroxidase, protease, etc. These
cells may be stimulated by glucans, pepti-
doglycans and lipopolysaccharides to
provoke exocytosis and enzyme release.
Activation of the proPo system results in
the production of melanin, a dark-brown
pigment responsible (among other pro-
cesses) for inactivating foreign particles,
and preventing their spread
throughout the host body, as well
as for healing cuticle damages.
Semi-granulocytes (75% CE) have a
large numbers of small granules
similar to vertebrate granulocytes.
These cells posses β-1,3-glucans
receptors and their principal func-
tion involves phagocytosis, encap-
sulation and clotting.
The modulation of the shrimp im-
munology is a key element in establishing
strategies for the control of diseases in
shrimp aquaculture.
Several different methods exist to evalu-
ate the immune system status such as
hemolymph protein concentration, total
hemocyte counts, phenoloxidase activity,
free radical production, phagocytic activi-
ty, etc.
Many different additives exist in the mar-
ket claiming to have an immunostimulant
effect.
In the FAO Fisheries and Aquaculture
Report No. 1053, probiotics were recom-
mended as a tool in the control of
AHPNS, a devastating penaeid disease
causing massive mortalities of cultivated
shrimp all over the globe.
Probiotics are known to have a positive
impact on vertebrates’ immune system.
To elucidate, if the use of a commercial
probiotic ECOBIOL AQUA® (Bacillus amy-
loliquefaciens CECT 5940) a study was
conducted by the Federal University of
Rio Grande, Brazil.
The study was conducted in 12 tanks of
1,000 L, in a greenhouse at the Estação
Marinha de Aquacultura (Aquaculture
research Center), belonging to the Feder-
al University of Rio Grande (FURG), in the
town of Rio Grande-RS-Brazil.
Liptopenaeus vannamei shrimp juveniles
(2 g) were used. The tanks were pre-
pared with biofloc from other shrimp
farms, with a density of 300 individuals
per m3. Shrimp were randomly distribut-
ed to four different treatments, with
AQUAFEED::ADVANCES IN PROCESSING & FORMULATION from Aquafeed.com Vol. 7 Issue 3
“ Many different additives exist in
the market claiming to have an
immunostimulant effect. In the FAO
Fisheries and Aquaculture Report
No. 1053, probiotics were
recommended as a tool in the
control of AHPNS ...”
Fig1: Light microscopy of hemocytes from spiny lobster, Panulirus argus:
Hyalinocytes (H), semigranulocytes (SG), and granulocytes (G). Scale bar=10µm
(C. Li, J.D. Shields / Journal of Invertebrate Pathology 94 (2007) 48–55)
30
AQUAFEED::ADVANCES IN PROCESSING & FORMULATION from Aquafeed.com Vol. 7 Issue 3
three replicates each, the probiotic was
applied directly to water. The probiotic
dose varied in each treatment: 0, 20, 40
and 80 g in 1,000 L of water per week (CO,
TA, TB and TC). The probiotic application
was performed daily.
Significant differences among treatments
were found in all immune system indica-
tors.
Total protein in hemolymph (TPC) was
higher in probiotic treated shrimp. Also
granulocyte percentage (HG) was higher in
ECOBIOL AQUA® treated animals.
Additionally, apoptosis index, a way to
evaluate infection, was higher in the con-
trol group.
Results:
The proteins present in the hemolymph,
are the mechanism by which the immune
system identifies shrimp pathogens, these
in addition to identify the type of patho-
gen, can regulate the binding of patho-
gens to hemocytes, thereby controlling its
phagocytic capacity. Therefore a higher
TPC is related to a higher capacity to de-
tect and control pathogens. The higher
granulocyte percentage also indicates a
better prepared immune system as these
are responsible for phagocytic and pro-
phenoloxidase activity.
In conclusion, the addition of ECOBIOL
AQUA® helped shrimp’s immune system
to be better prepared to fight a potential
infection. These results are consistent
with other effects observed in fish (Tilapia)
as an increased number of intraepithelial
lymphocytes or higher concentration of
lysozyme in blood.
AFΩ
More information
Àlvaro Ortiz, Product Manager,
Norel
E: info@norel.net
CONTROL TA TB TC P
TPC (mg/ml) 104 ± 7a 128 ± 4b 128 ± 4 b 124 ± 6 b <0.05
HG (%) 51 ± 7a 79 ± 5 b 81 ± 5 b 67 ± 5 b <0.05
Apoptotic cells/5µl 3 ± 1a 1 ± 1b 1 ± 1 b 2 ± 1 b
<0.05