White fecal disease (WFD) is one of the most serious problems in shrimp culture.
WFD on L. vannamei shrimp farming is currently causing lower productivity.
WFD becomes apparent when the digestive system of shrimp malfunctions and feces turns from normal (brownish color) to pale white color.
WFD has caused significant economic losses to shrimp farmers, because of high FCR, slow growth, and variable sizes of shrimp at harvest.
White faeces syndrome usually occurs after 60 days of culture (DOC) and it may be accompanied by high shrimp mortality.
2. What are the causes of White Fecal Disease?
Poor water quality, Unhealthy seed, High vibrio loads, Gregarines Protozoa, Anti-nutrional factors present in the feed, High Temperature, High water pH, High organic load and Bad pond bottom are some of reasons for causes of the disease.
3. What are the symptoms of WFD?
White faecal strings floating on the pond surface
White/golden brown intestine
Reduced feed consumption
Growth retardation and often associated with loose shell.
Mortality during molting
Reducing the shrimp survival by 20–30 percent.
4. What are the preventive remedies of WFD?
Cause of white faeces syndrome and treatment is uncertain. However reduced stocking density, proper water exchange together with better management practices will be helpful in evading WFS.
White spot disease (WSD) is the most serious threat faced by the shrimp farming industry worldwide.
The disease transmission is both vertical and horizontal. The disease is transmitted vertically from infected brood stock to larvae and horizontally either by ingestion of infected organisms or through carrier organisms.
All the life stages of shrimp may get infected by this virus.
2. What are the Causes of WSSV?
White spot disease is caused by a virus called as White Spot Syndrome Virus (WSSV). It is a rod shaped double-stranded DNA virus of 120-150 x 270-290 nm size, assigned to a new virus family, whispoviridae.
3. What are the Symptoms of WSSV?
The virus severely damages the stomach, gills, antennal gland, heart and eyes.
Affected shrimp are lethargic show reddish body discolouration and during the advanced stage of disease, characteristic 1-2 mm diameter white spots could be seen on carapace, appendages and inside surfaces.
Mortality of shrimp may start 2-3 days after infection and reach 80-90 percent within 5-7 days of onset of first mortalities, necessitating emergency harvest.
4. What is the Diagnostic measures?
WSD may be diagnosed based on gross signs such as the presence of the characteristic white spots, and rapid mortalities.
WSSV can be detected using polymerase chain reaction (PCR), or with molecular tools such as dot-blot and in situ hybridisation (ISH) tests.
5. What is the Preventive measure of WSSV?
Good biosecurity and healthy seed
It is always better to harvest the pond as soon as the disease is confirmed to prevent the spread of the disease.
Acute hepatopancreatic necrosis disease (AHPND) earlier known as early mortality syndrome (EMS) or acute hepatopancreatic necrosis syndrome (AHPNS) has been causing significant losses in shrimp farms in China, Vietnam, Malaysia and Thailand since 2009.
The disease affects both black tiger shrimp and Pacific white shrimp and is characterized by mass mortalities during the first 20-30 days of stocking.
2. What are the Causes of AHPND?
The disease is caused by a unique strain of Vibrio parahaemolyticus, that can produce toxins responsible for the primary pathology in affected shrimp.
3. What are the Symptoms of AHPND?
Atrophy of the hepatopancreas
Pale to white hepatopancreas
Visible black spots or streaks within the hepatopancreas
Hepatopancreatic microsporidiosis (HPM) is caused by enteric fungi, Enterocytozoon hepatopenaei (EHP). EHP is an yeast-like fungus belonging to a group called “microsporidia”, which are obligate intracellular parasites.
It was first reported as an unnamed microsporidian from growth retarded black tiger shrimp Penaeus monodon from Thailand in 2004.
It also has smaller spores (approximately 1 μm in length) and is currently known to infect both P. monodon and P. vannamei.
2. What are the Causes of EHP?
Shrimp become infected by ingesting spores from the water, from sediment. from eating EHP-infected live feeds (Polychaetes, molluscs, frozen artemia biomass etc) or by cannibalism and cohabitation.
3. What are the Symptoms of EHP?
Severe growth retardation
High size variation
Atrophy of hepatopancreas
Loose shell
Anorexia
Chronic mortality
4. How to check EHP?
nfections can be checked by microscopic examination of the hp and the gut of the shrimp.
Also confirmed by molecular testing of the hp by PCR
5. What is the Prevention measure of EHP?
The best approach for maturation and hatchery facilities to avoid EHP is not to use wild, captured, live animals (e.g., live polychaetes, clams, oysters, etc.) as feeds for broodstock.
Vibriosis is a bacterial disease caused Vibrio spp. These bacteria from part of the natural microbiota of wild and cultured shrimp and the marine environments. Vibrio infections have become a major constraint o the production and trade in shrimp aquaculture. They are responsible for several diseases and mortalities of up to 100% and cause crop loses globally. Vibrio species such as Vibrio harveyi and Vibrio Parahaemolyticus identified as primary pathogens in shrimp farming.
2. What are the Clinical signs of vibriosis?
Redness of body
Antennae cut
Atrophy of hepatopancreas
White faeces
Delayed hemolymph
Luminescence in dark
Anorexia
Lethargy
Melanization
White patches in the abdominal muscle
Expanded chromatophores
Luminescence and necrotic areas in the uropods
Mortality (heavy to chronic)
3. Shrimp diseases associated with vibriosis?
Vibrio can remain in the environment without causing disease, but can very easily switch from opportunistic and commensal to pathogenic when conditions change. Thus, its ability to cause disease or increase in virulence, is a complex process affected by many variables, including host, vibrio species, developmental stage, physiological conditions, environmental stress and infection method.
They are several diseases associated with Vibriosis.
V.harveyi - Luminous disease
V.Parahaemolyticus – EMS/AHPND
Vibro sp. - WFD
4. What is the diagnostic measure of Vibriosis?
Isolation of vibrio on selective media
qPCR (species specific and Genus specific)
5. What is the preventive measure of Vibriosis?
Vibrios are difficult to eradicate because they adopt well to different environment conditions and can adopt state when facing adverse conditions. Pond Management and robust gut health are important strategies to control vibrio, together with frequent sampling to monitor their levels in the shrimp gut and pond ecosystem.
They are several strategies to prevent diseases caused by vibriosis:
Biosecurity
use of natural antimicrobials and Probiotics
Bacteriophage application
Strict Feed management
Reduction of Organic Load
Rigorous water management and sanitation
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