Vibriosis is a prevalent bacterial disease affecting marine fish caused by Vibrio anguillarum. It occurs worldwide in cultured and wild fish, especially salmonids and perch-like fish, during late summer in shallow waters. Clinical signs include red spots, skin lesions, hemorrhaging, and inflammation. Diagnosis involves isolating the bacteria from lesions on agar plates and identifying it biochemically or through serological tests. Treatment involves antibiotics in feed but the disease often reappears after treatment. Prevention focuses on maintaining good water quality and husbandry practices.

2. Vibriosis is one of the most prevalent fish diseases caused by
bacteria belonging to the genus Vibrio.
Vibriosis (vibrio
anquillarum complex)
in milk fish –
hemorrhage and
inflammation of skin.

3. Vibriosis caused by Vibrio anguillarum
Fish species affected:
Mainly in marine culture of Salmonid and Perciformes fish
Vibriosis occurs in cultured and wild marine fish in salt or brackish
water,
Seasonal occurrence:
particularly in shallow waters during late summer
Vibriosis (vibrio
anquillarum complex) in
red grouper –
inflammation and loss of
scales.

4. Etiology
Vibrio anguillarum (mainly serotype I).
Family: Vibrionaceae.
Gram negative bacterium,
 appearing as a slightly curved rod with
round edges
polarly flagellated,
bipolar staining.
Motile in fresh suspensions in sterile saline
0.9%

5. The causative agent, of this Vibriosis
disease:
V. anguillarum, was first described in
1909 as the aetiological agent of the
'red pest of eels' in the Baltic Sea.
An earlier report from the early 1800's,
describing epizootics in migrating
eels (Anguilla vulgaris) implicated a
bacterium named Bacillus anguillarum.
The pathology of the disease and the
characteristics of the bacterium in
these two reports suggested that the
etiological agents were the same.
Vibriosis was not reported in North America until 1953, when V.
anguillarum was isolated from chum salmon (Oncorhynchus keta).
Vibriosis in salmonids
(vibrio anguillarum
complex) in chinook
salmon with lesion on
body.

6. Vibrio anguillarum belongs to one
of the halophilic groups of
Vibrios and survives at different
salinities.
it is able to survive in sea water
for more than 50 months.
More than twenty different serovars
of V. anguillarum (designated O1
to O23) have been described
(Pedersen et al., 1999).
Serovars O1 and O2 occur
world-wide and are those most
often found in connection with
diseases in fish particularly in
salmonids and species of cod
fish

7. All age classes are susceptible.
Mortality is higher among the young fry. Obviously, the
economic damage is greater when larger growing bass are
lost.
Age/size of fish mostly susceptible:

8. External & Internal Signs
Clinical Signs
The characteristic clinical signs of Vibriosis include
red spots on the ventral and lateral areas of the fish
 swollen and dark skin lesions that ulcerate,
 releasing a blood exudate.
There are also corneal lesions, characterized by an initial opacity,
followed by ulceration and evulsion of the orbital contents.
However, in acute and severe epizootics, the course of the infection
is rapid, and most of the infected fish die without showing any clinical
signs.
Vibriosis disease
occured in snapper

9. External haemorrhagic
appearance of skin and fins,
distended belly,
 inflamed anus
 exophthalmus of diseased
fish.
Pale liver with petechiae, splenomegaly
distended intestines filled with yellowish
transparent fluid comprise typical necropsy
findings of vibriosis.
Often there is excessive visceral fat due
to chronic overfeeding.
 The swim bladder is frequently
distended hence many of the moribund
and dead fish float on the surface

10. Sometimes sea bass fry
suffering vibriosis exhibit deep
necrosis of the trunk of the tail
peduncle and the caudal fin.
Cannibalistic activity against the sick
fish by their cage-mates may
predispose to such lesions
Necropsy findings

11. Diagnosis
clinical symptoms,
necropsy findings,
isolation of the bacterium on agar
plates (usually TSA or TCBS) and
identification either biochemically
(Biomerieux API system) or
serologically by means of rapid
agglutination test kits.
On TSA medium, incubated at room
temperature (about 25°C), pale
round colonies of about 1-1.5mm
in diameter, develop within 24-36
hours.

12. A drop of the antiserum is
placed on the dark field of the
test card.
A bacterial colony is taken
from the agar plate with the
loop and homogenised for 30
sec. with the antiserum.
A positive agglutination is
characterised by the
formation of a multitude of
small spherical agglutinates,
whereas a negative test shows
either no agglutinate
formation, or irregularly
shaped, cloudy agglutinates

13. Mono-Aqua diagnostic kit:
It comprises a kit complete with reagents
and necessary cards in order to perform a
quick (30 sec) sero-agglutination test on
bacterial colonies that have been isolated
on agar plates from the tissues of sick or
suspect fish in the laboratory.
Thus, it provides a fast and accurate
identification of the pathogen bypassing
the need to perform biochemical profiling.
.
The kit's main novelty lies in the fact that it provides an additional
"negative control antiserum", that is, an antiserum that reacts
against bacteria with close antigenic properties
with Vibrio anguillarum

14. Abreviation ofmic
rotube substrate Bacterial strain's biochemical
attributes
Result Triad code
OPNG:
ADH:
LDC:
ODC:
CIT:
H2S:
URE:
TDA:
IND:
β-galactosidase production
Arginine dihydrolase production
Lysine decarboxylase production
Ornithine decarboxylase production
Citrate utilisation
H2S production
Urease production
Tryptophane deaminase production
Indole production
+
+
--
--
Variable
--
--
--
+
3
0 or 2
4

15. Prevention and Control
General Methods
Control of furunculosis and vibriosis is best achieved by maintenance
of water quality, good husbandry and low stocking densities.
This is not, however, always possible, and where outbreaks occur,
treatment with antibiotics is the only option .
In areas where a disease is not endemic it is possible to exclude the
causative agents by a legislative policy such as
•1) restrictions on importation/movement of live fish/eggs and
2) slaughter and disinfection in infected fish

16. Treatment:
Daily administration of antibiotics,
mixed in the feed, for 10 days is
usually effective to eliminate
mortalities (oxytetracycline at
100mg/kg biomass per day,
flumequine at 80mg/kg biomass,
oxolinic acid at 60mg/kg biomass) and
potentiated sulphonamides
(trimethoprim + sulfadiazine) at
70mg/kg biomass per day.
However, the disease often
reappears in about 2-3 weeks post a
seemingly successful therapy.