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Examples of shrimp disease recognition for farm technicians through Level 1 diagnostics
Celia R. [email protected]
FMM/RAS/298: Strengthening capacities, policies and national action plans on prudent and responsible use of antimicrobials in fisheries Workshop 2
in cooperation with Malaysia Department of Fisheries and INFOFISH7-9 August 2017, Kuala Lumpur, Malaysia
Shrimp Culture Timeline: Daily monitoring and status analysis is a must!
Investigation of Problems and Mortality in Shrimp Culture
MORTALITY SHOULD NOT BE USED AS THE ONLY INDICATOR OF A PROBLEM
Farm technicians need to:
1. Know what is NORMAL.2. Recognize and analyze
situations.3. Find trending sampling data 4. Know optimum water
parameters; what was off during the event?
RECORD KEEPING IS VERY IMPORTANT.
Cameron, 2000
Making Sense of Farm and Laboratory Data
Pond-side Disease Diagnosis:
1. Slow Growth and Wide Size Variation
The definition of slow growth is relative and is a function of individual farm goals.
Factors that Affect Growth of Shrimp
o Shrimp Breed• Fast-growing shrimp vs. wild, inbred, etc.; SPF, SPT or SPR
• Growth is assessed based on standard curve, ABW or ADG• Accepted growth standard is based on company target
o Shrimp Feed• Nutritional content = how much protein, carbohydrates, vitamins, minerals, etc.• Digestibility of ingredients like fish meal and substitutes, binders, etc.• Freshness and storage condition = old feed, old raw materials, rancid fat components, aflatoxin,
etc.• Feeding management = number of rations, time of day, pellet size and distribution, territorial
behavior of shrimp (production staff should pay close attention)o Shrimp Environment
• Causes “off-feed” behavior; shrimp doesn’t eat (comparable to dirty and smelly dining table)• Sub-optimum environmental conditions• High salinity = requires more energy to maintain physiological equilibrium• If problem with environment persists, transfer to new pond; early detection important
• What’s the difference between stocking density and biomass?o Abnormality and Disease
• Damage in the hepatopancreas = partial or total stoppage of HP function• Malnutrition or parasitisim• Delayed molting or failure of molting• Infectious (EHP, Vibrio) or non-infectious (toxins) pathogens
The Shrimp Hepatopancreas
The shrimp HP is a delicate organ that is open to outside environment through the mouth.
- A good indicator of shrimp health
Main Functions:
DIGEST food
ABSORB food
STORE food
SLOW GROWTH happens when any of the above functions is impaired.
Diagram of Shrimp HP Development from Larva to Adult
Side View Top View Ventral/Bottom View
The Shrimp Hepatopancreas (histological sections)
High Lipid Storage Low Lipid Storage
SPOT THE DIFFERENCE
Malnutrition and Parasitism
Malnourished child = food not enough or not suitable (ex. Milk is not digested; diarrhea)
Child with intestinal parasites = parasites take away food from child
EHP is an infectious disease affecting shrimpo EHP does not directly cause mortality, but the parasite can potentially cause severe
growth retardation and can affect farm production.
o Presence of parasites and severity of parasitism need to be correlated with growth performance and feed convertion ration (FCR) to be properly managed.
Example of on-farm microscopic findings of shrimp hepatopancreas condition
There is more to slow growth than EHP. In this case, diagnosis by microscopy is more important than PCR.
Granulomas and strangulations in HP tubules are not caused by EHP
Granulomas in HP
• Indicate chronic bacterial infection due to various species of Vibrio (harveyi, parahaemolyticus, other species)
• The presence of vibrios is associated with accumulation of organic matter within the pond
• Direct effect of chronic vibriosis is slow growth• Slow growth is directly proportional to degree of
HP damage and extent of granuloma formation• Granuloma formation is a slow process• Long-term effect is chronic mortality• Diagnosis can be done by wet mount and
microscopy (or use your smart phone cameras!)
çGranuloma
çGranulomas è
Wet Mount
èêè
Granulomas in the hepatopancreas (arrows)
Davidson’s fixed samples
Pond-side Disease Diagnosis:
2. Gill Discoloration and Shell Fouling
Celia R. Lavilla-PitogoiAqua Malaysia
Animals are good groomers!
Why do crustacean gills change in color?
When grooming stops, appearance changes!
Causes of gill discolorationo Infectious pathogens – fungus, bacteriao Exposure to harmful chemicals = polluted water sourceo Mechanical injury resulting to melanizationo Turbid water = too much sedimentso Plankton crasho Others?
The Gill Structure
Preening in crustaceans will get rid of fouling: presence of fouling organisms on shell and gills indicate weak shrimp or rapid environmental deterioration.
Treat the cause and not the symptom!
Important reminders!
o Part of the shrimp’s day-to-day activity is spent cleaning its body.o If it is not feeling well, it will not preen or groom itself.o Even if the shrimp grooms itself, its normal preening behavior will not
be enough if the environment is dirty. o The energy it spends on grooming will have an effect on its growth.o Let’s grow well-groomed and healthy shrimps.o The answer is in good water quality.
Pond-side Disease Diagnosis:
3. Water quality and environment
Celia R. Lavilla-PitogoiAqua Malaysia
Water quality and feeding scenarios in the shrimp pond
Where is food?
I can’t smell my
food.
My food is not
enough.I can’t go near the
food.
I don’t like to eat!!!
The pellets are
too big/small.
Our standard for hygiene should be the same for shrimp
Loose shell and/or soft meat are manifestations of sub-optimum feeding. What to do?
o Check if shrimp are eating wello Examine feed record, supply, quality, feeding frequency, etc. What change
happened?• Change feed or adjust amount• Give supplementary diet• Supplement pellets with vitamins, minerals, etc.
o Examine water quality record• Change water to improve quality• Apply mitigation measures like probiotics and other acceptable products
o Examine stocking density, biomass, and pond carrying capacity – thin out or do partial harvest
o When above strategies fail, HARVEST while shrimp quality is still at its best.
Table of Water Quality Parameters (on-farm alert system)
Parameter Standard/Optimum Value Yellow Flag Red Flag
pH AM/pH PM 6.5 – 8.5 ? ?pH difference Less than 0.2 Above standard Above standard
Temperature 28 – 33 Celsius Above/below standard
DO > 4 < 4 ? Paddle wheel aerator breakdown
H2S < 1 ppm ? ?Alkalinity 80 – 100? ? ?Nitrite ? ?Transparency Depends on culture system (ex. Biofloc method ponds would have low
transparency
Hydrogen sulfide – the silent killer?
Fine tuning of water quality measurements and values is very important.
Pond-side Disease Diagnosis:
4. Loose Shell/Soft Meat
Celia R. Lavilla-PitogoiAqua Malaysia
It’s all about body mass and muscles!
Weight loss in humans is easily seen:
• Loss of fat in specific body parts
• Loss of muscle mass
Did not eat -anorexia
Indicators of weight loss in crustacean
CRAB = large shell, light weight; no muscles inside
SHRIMP = loose shell, soft meat = weight loss
After weight loss:• People can change the
size of their clothes
• Shrimps cannot reduce the size of their shell and the outcome is loose shell.
Possible Causes of Weight Loss in CrustaceansFor large shrimpo Underfeeding o Change in quality of feedo Shrimp stopped eating due to stress from:
• Water quality and environment (high salinity, non-optimum temperature, etc.)
• Toxic factors in feed, water and environment
For small shrimpo Pathogens or abnormalities in the HP (EHP, vibrios, granulomas,
strangulations)o Malnutrition during larval rearingo Underfeeding and all other factors that affect large shrimp
Assessing Pond Problems Based on Sizes of Affected ShrimpWhat two disease events can you see in the photo?
Shrimp with full meat
Shrimp with soft meat
Assessing Pond Problems Based on Sizes of Affected Shrimp
Shrimp with full meat
Shrimp with soft meat
- Shrimp are eating- Guts are full- Muscles firm
- Shrimp not eating- Guts are empty- Muscles watery
Histology of Shrimp with Soft Meat/Loose Shell
Hepatopancreaso Absence of stored lipids (HP is pale)o Bacterial infection in HP = secondaryo EHP varying from Grade Trace to 4
Muscleso Watery o Nuclei are abnormal
Thank you for your attention!