1. Emerging diseases in Tilapia: Future prevention methods will alleviate the economic threat
C. Komar*, L. Labrie, J. Ng, B. Sheehan, W. Enright and Z. Tan Intervet Norbio Singapore
Good afternoon to everyone and thanks to the organizers and to phil Klesius
During the last few years, diseases in tilapia have become a threatening reality
20 minutes is a short time, and I want to take the opportunity of this talk to expose you the concept of fish vaccination without going into too much details.

2. Outline One observation: diseases are now a reality in tilapia farming
One piece of advice: identify and understand diseases present in your fish farm
One important question: what should be farmer’s expectation to a fish vaccine
A few practical aspects of vaccination in tilapia
First illustrate some of the many diseases causing problems in tilapia

3. Streptococcosis

4. Columnaris

5. Francisella spp.

6. Iridovirus

7. Parasitic diseases
monogenean
Oodinium sp.

8. Tilapia used to be considered as a hardy or disease-resistant fish But this is changing…

9. Major Diseases Affecting Tilapia during the Farming Cycle
Phase
Hatchery
Sex-reversal
Nursery
Pre-grow-out
Grow-out
0 g
1 g
10 g
100 g
1 kg
Nodavirus?
Flavobacterium columnare
Saprolegnia & Branchiomyces
Pathogen
Trichodina & Dactylogyrus
Edwardsiella tarda
After several years of sampling all over the world, here is a table of major diseases we have found in tilapia
This is a general table and presence of such or such disease might vary from one farm to the other
Therefore , it is very important that one’s be very aware of diseases present in his farm
Francisella spp.
Iridovirus
Streptococcus spp. (Sa; Si)
Nocardia seriolae
Note: importance of the disease is roughly in proportion to the size of the arrow bars

10. Outline One observation: diseases are now a reality in tilapia farming
One piece of advice: identify and understand diseases present in your fish farm
One important question: what should be farmer’s expectation to a fish vaccine
A few practical aspects of vaccination in tilapia

11. Know your enemy : how to evaluate the health status of your farming operation
In other words, it is critical to know and understand your enemy in order to avoid to get killed

12. Random sampling is not the ideal method to study disease
If a disease causes 30% mortality over 12 months
The probability to find 1 sick fish in a random sample of 10 fish is <1%
At any given moment and even in an outbreak situation, most of the fish are healthy and it is virtually impossible to isolate any pathogens from most of the population.

13. How to get an accurate picture of the diseases present in your farm?
Even during a disease outbreak, most fish in the population are healthy
Sample moribund fish with clear external signs
Samples should be processed by a professional laboratory
Therefore, it is critical to have a good sampling of the diseased population. Only this type of sampling will give a good understanding of what type of disease is present in the farm

14. Bacterial isolation
Bacterial isolation from internal organs is an important part of diagnosis

15. Bacterial identification and antibiogram
Antibiotic
Mar 05
Chloramphenicol R
Nitrofurantoin S
Tetracycline
Flumequine
Neomycine
Trimethoprim - sulfamethoxazole
Ampicilline
AMoxicilline
Gentamicine
Rifampicine
Kanamycine
Perfloxacine
Norfloxacine
It allows bacterial id that can be used for vaccine development or antibiogram and antibiotic selection

16. PCR Analysis for Viral Disease
Nodavirus
positive at 426 bp
Iridovirus positive at 568bp
For common virus, PCR is an easy and rapid method of diagnosis

17. Electromicroscopy Iridovirus 500 nm
Electromicroscopy is necessary for novel virus or virus for which pcr primers are not avalaible
500 nm
Iridovirus

18. Histopathology H&E x20: lateral muscle H&E x400: eye H&E x200: brain
Histopathology can give a clue on pathologies that can not be diagnosed by other methods
H&E x400: eye
H&E x200: brain

19. Factors in disease expression
Nutrition
It is important to keep in mind that diseases are rarely caused by one cause only
They are multifactorial and clearly depend on the environment of the fish
For instance, nutrition (quality and quantity) plays a clear role in the expression of diseases

20. Factors in disease expression
Fish density
Micro-organisms
Fish density and micro-organisms present in the water are other important factors to consider
An interesting parabol that can be drawn is the one of SARS: this disease first started in HK where the population density is 6,000 inhabitants per sqkm and not in

21. Factors in disease expression
Fish density
Micro-organisms
In Mississippi where there are only 3!

22. Factors in disease expression
Biosecurity
Water quality parameters
Stress level
Living in a confined environment is a stressful.
Diseases such as cholera which are considered to be rare in developed country will reappear if standard of living suddenly decrease, water become contaminated and people have to live in a confined environment.
We have to keep in mind that similar patterns will happen to our fish and diseases are a consequence of the intensification of the system

23. Factors in disease expression
Stress level
Critical level of stress not reached: system ok
Feeding
As long as we keep all parameters related to the fish in some kind of equilibirum, the system is ok and we can be relatively free from diseases..
Fish: density/quality/size/handling
Micro-organisms
Water quality

24. Factors in disease expression
Stress level
Critical level of stress reached: system suboptimal
Feeding
Fish
However, if there is disrupture in one or more of the parameters, the system becomes suboptimal
Micro-organisms
Water quality

25. Factors in disease expression
Stress level
Critical level of stress breached: situation of “disease”
Feeding
Fish
And we can enter in a situation of diseases
Micro-organisms
Water quality

26. Fish health management
Therapeutic treatment
Antimicrobials
Antibiotics
Antiparasitics
Antifungals
Prevention – good health management
Biosecurity/quarantine/exclusion
(Responsible movement of live AA)
Selection
Sanitation
Nutrition and feed management
Vaccination
Clearly, fish health management depends on a number of factors that include biosecurity, etc…

27. Outline One observation: diseases are now a reality in tilapia farming
One piece of advice: identify and understand diseases present in your fish farm
One important question: what should be farmer’s expectation to a fish vaccine
A few practical aspects of vaccination in tilapia
Vaccination is one of these parameters, what shall we expect from that?

28. The concept of vaccination
“Vaccines are preparations of antigens derived from pathogenic organisms, rendered non-pathogenic by various means, which will stimulate the immune system in such a way as to increase the resistance to disease from subsequent infection by a pathogen.”
A.E. Ellis, 1988
Feeding
Fish
Micro-organisms
Water quality

29. The concept of vaccination
Pathogens (bacteria, viruses…)
Vaccination
Infection
Diseased
Resistance to
infection
Vaccination does not eradicate diseases, it does not solve problems of biosecurity and water quality parameters and if we reach the limits of the system, disease will still be present. However it gives more freedom in the system if we know what are its limits.
Feeding
Fish
Mortality
Treatment
Healthy
Micro-organisms
Water quality

30. The salmon industry is an excellent example of the benefits of vaccination:
95% survival

31. Development of Fish Vaccines Epidemiology and disease investigation
Disease Information
Epidemiology and disease investigation
Aetiology of Disease
Characterization of Isolates
Definition of Disease
Challenge Model Devel.
Laboratory phase
Vaccine Development
Vaccine Production
Lab Vaccination Tests
Normally 5 – 8 years in R&D
Pre-Licensing Studies
Field and licencing
phase
Licensing
Marketing Preparation
Product Introduction

32. Outline One observation: diseases are now a reality in tilapia farming
One piece of advice: identify and understand diseases present in your fish farm
One important question: what should be farmer’s expectation to a fish vaccine
A few practical aspects of vaccination in tilapia

33. Intervet Norbio Singapore Pte. Ltd.
(operated January 2000)
Seriola spp.
Marine fish
Tilapia
Dedicated to disease research and product development for aquatic animal health in the warmwater environment

35. Norvax®Strep Si Onset and duration immersion

36. Norvax® Strep Si Onset and duration injection
Data from the field have shown full protection for 14 months

37. Sea bass: S. iniae infections
Immersion (0.5 – 10 g)
Injection
(15 – 100 g)

38. Choice of application Comparison of application methods

39. Vaccination window Phase Pathogen Vaccination window Nodavirus?
Hatchery
Sex-reversal
Nursery
Pre-grow-out
Grow-out
0 g
1 g
10 g
100 g
1 kg
Nodavirus?
Flavobacterium columnare
Saprolegnia & Branchiomyces
Pathogen
Trichodina & Dactylogyrus
Edwardsiella tarda
Francisella spp.
Iridovirus
Streptococcus spp. (Sa; Si)
Nocardia seriolae
Vaccination window
Note: importance of the disease is roughly in proportion to the size of the arrow bars

40. Important aspects of vaccination
Vaccination window: fish must be vaccinated before to be in contact with the disease
Vaccine stimulates the specific immune system: no cross-protection between S. iniae and S. agalactiae in laboratory challenges

41. 1 skilled person can inject 1,000 fish in one hour
A team of 4 injectors working 8 hours a day can vaccinate 30,000 fish per day

42. Take home message Prevention is better than cure
Vaccination is a tool for better health management and not a substitute for other important health management measures (biosecurity, good husbandry practices, etc…)
It has been a successful disease management method in the salmon industry for the last 15 years.
Vaccination in tilapia will help the sustainable development of this industry
Vaccination works like an insurance:
You pay an insurance policy in case that you will get sick.
Fish must be vaccinated before they are in contact with the disease
As for an insurance policy, vaccination is specific to certain pathogens
Vaccination against Streptococcus iniae will protect against this specific disease only

43. Acknowledgements Support from the Intervet team and many collaborators throughout the world is highly appreciated.
Thank you!