Shrimp Disease ( FLU UDANG )

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Both infectious and non-infectious disease has continuously plagued the various sectors of the shrimp industry. Although it is generally recognized that intensive culture systems often encounter serious disease problems, more recent experiences have shown that low-density culture systems can also be severely affected. Diseases of both infectious and non-infectious etiology have been described, but their effects on shrimp and impacts on culture activities remain poorly understood. Diseases caused by viruses, bacteria, fungi and parasites are considered very significant to shrimp culture.
PRINCIPLE CAUSES OF DISEASES IN SHRIMP CULTURE
Degradation of pond bottom and water quality.
Loss of balance in environment.
High stocking density with limited water exchange facilities.
Use of excessive artificial feed and chemicals.
Nutritional deficiency/ poor nourishment.
Accumulation of unutilized feed followed by its purrefaction by the native heterotrophic microorganisms.
Poor and inadequate management.
Inadequate aeration.
Suboptimal or heavy algal blooms in the pond.
Physical injury.
Presence of virulent pathogen in high counts.
BEHAVIOURAL, EXTERNAL AND INTERNAL SIGNS OF SHRIMP DISEASE
Change of body colour and pigmentation.
Crowding near the aerator, pond edge and water surface.
Stopping or reduced feed intake and growth.
Becoming lethargic or erratic.
Body and shell soft.
Swollen cephalothorax, abdomen and tail.
Spot on shell, muscle, and erosion of shell and appendages.
Abnormality on gills, muscle, hepatopancreas and intestine.
TYPES OF SHRIMP DISEASES
We can divide shrimp disease in many ways. Different types of shrimp disease are discussed below:
A. According to pathogen:
Viral Shrimp Disease
Bacterial Shrimp Disease
Fungal Shrimp Disease
Parasitic Shrimp Desease
B. Non-infectious disease:
Chronic Soft Shell Syndrome
Black Gill Disease
Red Disease
Cramped Tail Disease
Gas-Bubble Disease
Muscle Necrosis
A. According to pathogen:
I. Viral Shrimp Disease
At least 15 viruses are known to infect cultured and wild marine penaeid shrimp. Reported types include parvoviruses, baculoviruses, reoviruses, togaviruses and rhabdoviruses. Three systemic baculoviruses have recently been described for penaeid shrimp: yellowhead virus (YBV) (Boonyaratpalin et al., 1993), hemolymph baculovirus (Owens, 1993) and systemic ectodermal and mesodermal baculovirus (SEMBV) (Wongteerasupaya et al., 1995). YBV and SEMBV infections have caused drastic mortalities resulting in severe economic losses in shrimp culture facilities in Thailand, Indonesia and India. Also described is a rod-shaped nuclear virus of Penaeus japonicus (RV-PJ) (Inouye et al., 1994) which has been implicated in mass mortalities of cultured P.japonicus in Japan in 1993.
White Spot Syndrome Viral Disease (WSSVD) / China virus disease
Disease signs at the farm level
characterised by high and rapid mass mortality of rapid onset, mainly in farmed penaeid prawns
can occur at any stage of the grow-out period
Disease signs at the tank and pond level
prawns with white spot disease often do not show distinctive clinical signs
lethargy
cessation of feeding
a few days later, moribund prawns near surface at edge of rearing ponds

Clinical signs of disease in an infected animal
loose shell
white calcium deposits embedded in shell, causing white spots 0.5-2.0 mm in diameter for which the disease is named (but white spot disease can occur without these signs)
darkened (red or pink) body surface and appendages
heavy surface and gill fouling by external parasites
white midgut line through abdomen of severely affected larvae and postlarvae
The shell lesions range from minute spots to discs several millimetres in diameter, and may coalesce into larger plates. They are most easily observed by removing the cuticle over the cephalothorax, scraping away any attached tissue with the thumbnail and holding the cuticle up to the light.
White spots in the cuticle are unreliable even for preliminary diagnosis of white spot disease, because similar inclusions can be produced by some bacteria, high alkalinity and other infectious or environmental conditions.