Download poster Vibrio 2007

A temperature dependent disease : impact of
Vibrio harveyi on the abalone Haliotis tuberculata
Agnè
ès Travers1,2*, O. Basuyaux2, M. Garnier3, J.L.
Agn
Agnès
Nicolas3, M. Koken1, S. Huchette4 and C. Paillard1
1
3
IUEM, Plouzané, France, 2 SMEL,Blainville sur mer, 3 Ifremer Brest
France Haliotis, Plouguerneau, France. * [email protected]
Introduction:
Wild abalone stocks are declining worldwide due to over-exploitation or diseases
affecting several Haliotis species, including the ormer Haliotis tuberculata, the most
commercially-important abalone in Europe [1].
Vibrio carchariae has been isolated in H. tuberculata during the mass mortality
that occurred in 1998, in France [2]. Mortalities seems to be directly link to
seawater temperature (>16,5°C, Figure 1). This vibrio is a synonym of Vibrio harveyi,
already known to be pathogenic for shark, shrimp and prawn [3].
Figure 1: Distribution
of H. tuberculata
summer
mortalities
along France coast
and
isotherm
of
summer temperature
maximum. Red abalone
correspond
to
witnessed mortalities
The goal of this new research topic is to highlight direct implications of this
bacterium in ormer mortalities and to elucidate mechanisms of interaction between
Vibrio harveyi and Haliotis tuberculata.
Huchette and Clavier [1]
1. Pathogenesis: Clinic signs
Mortalities have been reported in the field and in
hatcheries in Brittany and Normandy (France). Mortalities
are associated with loss of muscular motility, pericardial
inflammation and white pustules on the foot
(corresponding to bacteria clumps, as shown by histology,
bacterial isolation and PCR identification).
Bacteria were principally found in muscle and
haemolymph.
a
b
Figure 2: Macroscopic and
microscopic characteristics of
mortalities associated with V.
harveyi.
a)
Pericardial
inflammation, b) White pustule,
c) Hematoxilyn Eosin coloration
of muscle section.
c
2. Modulation of the interaction
1. Pathogenicity of different
V. harveyi strains
Different V. harveyi (isolated in field
as in hatcheries during mass mortalities)
were compared with collection strains.
Their pathogenicity was tested in vivo.
vivo
:
As temperature seems to be
determinant for disease development in
the field, experimental inoculations were
performed at different temperatures on
hatchery abalone.
3.
Host
physiology
maturation effects
100
Spawn just before infection
Spawn 2 months before infection
Immature abalone
90
80
60
40
20
0
15°C
17°C
18°C
19°C
20°C
Temperature
29 species , 808 sites (global gap removal)
Neighbor Joining Method
Jukes and Cantor distance
Figure 4:
500 bootstrap replicates
Figure 3: gyrB. Pathogenic V. harveyi are in yellow.
29 species , 808 sites (global gap removal),
Neighbor Joining Method, Jukes and Cantor
distance, 500 bootstrap replicates.
01_021 to 05_043 correspond to abalone isolated V. harveyi.
→ Pathogenic strains cannot be
differentiated from non pathogenic ones
on the basis of gyrB or rpoA sequences.
Percentages of dead abalone 5 days after
introduction of V. harveyi strain 02_001 into
the surrounding water. (106 bact./ml during
24 hours, triplicate tanks, 20 abalone/tank).
→ Significant mortalities due to V.
harveyi occurred only over 18°C.
and
As mortalities occur in the field
simultaneously with spawning, effects of
gonad maturation on susceptibility to V.
harveyi was investigated on adult abalone
at 19°C.
Cumulative mortalities %
P e rce n ta g e o f a b a lo n e
d e a d a fte r 5 d a ys
100
in
100
V. harveyi
0.063
01_022
01_021
02_001
04_165
S20
S35
05_055
02_109
05_043
LMG19114
LMG10948
LMG16863
dq499007
IFO15634
LMG7890T
LMG11755
LB5
V campbelli ab01495
LMG10946
LMG10948
dq345719
LMG10947
dq499009
V pelagia_ab014954
V alginolyticus
V splendidus
V hollisae
V aestuarianus
V diazotrophicus_ab0
2. Pathogenicity
Temperature effect
80
70
60
50
40
30
20
10
0
-10 0
5
10
15
Time (days)
20
25
Figure 5: Evolution of mortalities after
introduction of the pathogen V. harveyi strain
02_001 into the water (105 bact./ml during 24
hours at 19°C, triplicate tanks, 20 abalone/tank).
→
Mature
abalone
(spawning
immediately before infection) are
more sensitive than abalone that
spawned 2 months before. Immature
abalone, independently of their size
and age, appeared insensitive to
infection.
Conclusion and perspectives:
H. tuberculata mortalities associated with V. harveyi depends on V. harveyi strain, abalone age, gonad maturation level and
water temperature. Abalone are affected by temperature for sexual maturation or growth. Temperature may also increase
their sensitivity to bacteria. But it may also affect bacterial growth (optimum 28°C) and virulence.
Results highlight the importance of 1°C variation on disease development (17°C vs 18°C). Thus, in view of the current global
warming, the impact of temperature on V. harveyi growth and virulence, and on abalone immunity should be investigated further.
Moreover, differentiating virulent and avirulent strains should be one of our priority.
Useful references :
1. Huchette, S. M. H. and J. Clavier (2004). "Status of the ormer (Haliotis tuberculata L.) industry in Europe." Journal of Shellfish Research. 23(4) 951-5.
2. Nicolas, J. L. et al. (2002). "Vibrio carchariae, a pathogen of the abalone Haliotis tuberculata." Diseases of Aquatic Organisms 50(1): 35-43.
3. Austin, B. and Zhang, X.H. (2006) “Vibrio harveyi: a significant pathogen of marine vertebrates and invertebrates”. Letters in applied microbiology 43: 119-24.