Fish Disease Collection
Causes of infectious diseases include:
Biological factors such as microbial flora present in the pond and its water are responsible regarding the susceptibility of shrimp to pathogens.
A. Viral Shrimp Disease
Penaeus vannamei is mainly caused by viral diseases, and the losses are also the largest, so prevention should be the priority.
a. Vitiligo Syndrome:
Vitiligo virus infection. The sick shrimp have an empty stomach, and the carapace and plastron are easily peeled off.
After the carapace is peeled off, white spots (different from bacterial white spots) can be seen when the carapace is peeled off, and dirt adheres to the body surface.
The disease may also be caused by bacteria (Vibrio) or other causes such as stress caused by nutritional deficiencies.
The symptoms are slightly different: after the carapace of bacterial leukoplakia is peeled off, the carapace is intact when looking at the light
After the carapace of viral leukoplakia is peeled off, white spots can be seen facing the light. Although the two may occur simultaneously, the lesions rarely overlap.
b. Erythroid disease (taola virus disease)
The body surface is light red, the tail fan turns red, and the swimming feet are light red (some are not red); the stomach is empty, the carapace becomes soft, and most of them die during molting. In the chronic stage, multiple damaged black spots appeared on the surface of the shrimp legs, and they could feed normally.
c. Yellow head disease
Yellow head virus infection. Swimming irregularly on the water surface, the carapace is yellow or whitish, swollen, the gills turn yellowish to brown, and the hepatopancreas turns reddish. This disease is more common in juvenile shrimp and 50-70-day-old shrimp.
d. Baculovirus Disease
Infection with baculovirus in prawns. Slow growth, anorexia, not shelling, gills with dirt, hepatopancreas turns white.
e. Infectious subcutaneous and hematopoietic necrosis disease
Infectious subcutaneous and hematopoietic necrosis virus infection. Sick shrimp float or hang on the surface of the water, swim slowly, have anorexia, the shrimp body is turned over, the abdomen is upward, the carapace of the body surface appears white or brown patches, the muscles are opaque, and most of them die after molting or molting. In the chronic stage, the forehead and sword of the diseased shrimp are deformed and bent, and dirt adheres to the body surface and gills.
B. Bacterial shrimp disease
a. Red leg disease
Vibrio parahaemolyticus, Vibrio eel infection. The appendages turn red, especially the swimming feet are red, the carapace and gill area are yellow, and they mostly swim or spin around the pool, anorexia.
b. Gill rot disease
Vibrio or C. columnar infection. The gill filaments are gray-white, swollen and broken, and then fester from the base of the tip, the necrotic part shrinks or falls off, and it is difficult to breathe and die.
c. Rotten eye disease
Non-group 01 Vibrio cholerae infection. Slow movement, often dormant, the eyeball first swells, turns from black to brown, then festers and falls off, leaving only the eye stalk.
d. Fluorescent disease
Vibrio infection. In the early stage of the disease, the gills, cephalothorax, and abdominal muscles of the sick shrimp fluoresce in the dark, the tentacles are broken, the feeding is less or stopped, the pool side swims slowly, and the response is slow.
Infection caused by Aeromonas hydrophila or ingestion of certain algae poisoning. The digestive tract is obviously thickened and red, the stomach is empty, and there is liquid or yellow pus.
f. Brown spot (crust appendix ulcer disease)
Vibrio or monas infection. There are black-brown ulcer spots on the body surface and carapace, the ulcer edge is white, and the center is sunken. In severe cases, it can erode into the tissue under the carapace.
g. Filamentous Bacteriosis
Caused by the invasion of filamentous bacteria. Many filaments protrude from the body surface or gill surface of the diseased shrimp.
h. Muscle turbidity
Caused by high water temperature, low dissolved oxygen or Vibrio invasion. The diseased shrimp has white spots on the abdomen, or the entire abdomen is white, and behaves abnormally, moving or jumping out of the water.
C. Fungal shrimp disease
a. Black spot:
Caused by fungal and bacterial infections. The gills caused by fungi are dark black, highly infectious, and die in large numbers; the gills caused by bacteria are yellow or bright brown, and then gradually turn black.
b. Saprolegnia (white hair disease)
Mostly due to injury infection of water mold. Body surface with raw white hair, into cotton wool.
The larval stage of multiple freshwater prawns. Initially, opaque white dots appear on the base of the tail and appendages, which gradually expand to the whole body. Morbidity is high and death is severe.
D. Parasitic diseases
Common parasites, except the shrimp wartworm and the cut head worm, which belong to crustaceans and flat animals, are all single-celled protozoa.
a. Shrimp wartworm
Crustacean, dioecious, the female is slightly flat oval, the male is several times smaller than the female, and the female is attached to the abdomen.
Shrimp and crab are susceptible to infection, parasitic in the gill cavity, so that the gills bulge like warts, open the gill cover to see the parasite.
b. Cutting head worms
Flat animals, parasitic shrimp on the slits of the abdominal grooves and somites, sometimes parasitic gills.
At low magnification, the 5 antennae, testis and sucker of the parasite can be seen, which can be stretched and retracted when moving, and are linear or crescent-shaped when elongated, and become shorter when they are adsorbed by attachments. This worm mainly parasitizes freshwater prawns and crayfish, which fall off when exposed to salt water.
c. Microsporidia (white turbidity)
The spores are spherical, oval or eggplant-shaped, parasitic in blood, muscle tissue, and internal organs, making the diseased shrimp milky white and opaque, commonly known as milk shrimp and cotton shrimp.
d. Bodou worm
Flagellates, the body is nearly triangular or nearly spherical, parasitic on the whole body of juvenile shrimp.
e. Shrimp cluster worms
Common protozoa, many species, mainly nematode cluster worms and head leaf cluster worms, generally not harmful.
Often parasitic in the digestive tract, the intestinal tract becomes white, and the worm body can be seen under a high-power microscope.
f. Pseudomonas aeruginosa:
Ciliates, the worm body is sunflower seed-shaped, the front end is pointed, the back end is blunt and round, and the hemolymph of the multi-parasitic overwintering broodstock makes the hemolymph milky white and turbid.
g. Straw worms and lotus worms
Both are ciliates. The straw worm is wide in the front and narrow in the back, the middle of the front edge is concave, and a bunch of transparent straws protrude from the left and right corners;
h. Other Ciliates
When other sessile ciliates, such as polycondensed worms, branch worms, single condensed worms, bell-shaped worms, etc., are parasitized in large numbers, the gills, body surfaces, appendages, etc. of shrimps are black, and the body surface is gray-black fluffy thing.
E. Filamentous algae (proliferative algae, hair algae, water clouds, etc.) attachment disease:
Filamentous algae adhere to the body surface, and in severe cases, the whole body surface (including the eyeball) is covered with algae.
Cyanobacteria poisoning: Microcystis overproduces, the water transparency drops below 20 cm, and the algae die to produce toxins.
H. Nutritional diseases
a. Molting disorder
Lack of calcium, phosphorus, magnesium and B vitamins, caused by excessive water transparency. The trunk of the sick shrimp is bent, the back is arched, stiff, and unable to bounce.
c. Soft shell disease
Insufficient feeding amount and water exchange, lack of phosphorus and calcium, abnormal molting. The carapace is thin and soft, the body color is gray, and the activity is poor.
Illustration of 8 common diseases in shrimp farming, shrimp farmers should not miss
I. Swollen Shrimp Liver
Diagnosis: Shrimp liver is swollen and pale, the shrimp intestine has no food or is broken, the shrimp shell is soft, and the mortality rate is high.
The pathogen is a special kind of highly virulent Vibrio parahaemolyticus.
White shrimp shows signs of hepatopancreatic necrosis, pale in color; stomach and intestine without food.
Panels are healthy shrimp showing normal-sized HP with a slightly dark orange tinge, with the stomach and intestines filled with food.
Shrimp infected with EMS/AHPND are dark in color, grow slowly, and have atrophied livers.
Disease prevention: Choose high-quality and healthy shrimp fry. Check the Vibrio density in the pond to make sure the Vibrio density is always at a safe level.
Stabilizing the algal phase and bacterial phase through polyculture and rotation is conducive to controlling the growth of Vibrio.
If you want to engage in shrimp farming for a long time, you should try to avoid the use of antibiotics!
II. Vitiligo (WSSV)
Cause: The disease can be caused by a virus, bacteria, or the environment. For viruses, the disease is caused by the white spot syndrome virus (WSSV).
Bacterial white spot syndrome (BWSS) is caused by bacteria.
Environmental vitiligo is caused by high water hardness (Ca2+ and Mg2+), and shrimp absorb too much Ca2+ and Mg2+, causing vitiligo to appear on the shell.
Diagnosis: The first task of finding vitiligo is to quickly identify the cause and deal with it in time.
The PCR test results are quick and accurate and should be performed as soon as the shrimp develops spots.
If the PCR result is WSSV positive, harvest it immediately; on the contrary, if it can continue to breed, and take action according to the situation.
White Shrimp gets infection with WSSV White Spot Virus.
Penaeus monodon gets infection with white spot virus WSSV.
Microscopic examination of the sample under the microscope reveals rounded edges with many black dots in the middle.
In severe cases, molting is slow, growth is slow, and sporadic deaths occur, but not mass deaths.
Bacterial vitiligo caused by bacteria (Wang et al., 2000). Under the microscope, it is in diffuse form, hollow and rounded around.
Prevention of disease: In order to prevent disease well, the following principles must be well implemented:
1. Choose shrimp fry with good quality, especially without WSSV
2. Choose the appropriate breeding season
3. The water in the pond cannot directly enter the pond and must be filtered
4. Set up purse seine to prevent the entry of pathogens such as birds and crustaceans
5. Strictly manage and monitor the pond water environment
III. Infectious hypodermic and hematopoietic necrosis (IHHNV)
Reason: It is the smallest type of shrimp virus particle, which mainly causes necrosis of hematopoietic organs and epithelial organs.
Diagnosis: Infected Penaeus vannamei is bent or deformed, with abnormal head appearance, deformation, and shrimp growth rate is reduced by 10-30%.
Shrimp infection with IHHNV reduces yield and causes economic losses, as infected shrimp are often small, non-uniform, and varied in shape.
Typical signs of IHHNV infection in P. vannamei, such as deformed head, deformed tail.
Signs of IHHNV disease in P. vannamei: head deformity.
Signs of IHHNV disease in Penaeus white shrimp: deformation of the shrimp body.
Disease Prevention: The most effective way to prevent disease is still to use high-quality, clean shrimp.
IV. Yellow Head Disease (YHV)
Cause: The pathogen is caused by a complication of yellow head virus (YHV) and associated syndrome virus (GAV). Currently, there are 6 different genotypes of YHV.
Diagnosis: Infected shrimp are yellow or brown in gills, head, thorax, swollen intestines, extremely high mortality, reaching 100% mortality 3 to 5 days after infection. PCR results were positive for YHV/GAV.
Disease Prevention: Prevent the spread of this disease by testing before planting and treating water quality and surroundings accordingly.
V. White stool disease (WFD/WFS)
Cause: The exact cause has not been determined, but there are many studies that suggest that white stool is caused by bacteria of the genus Vibrio, and others that suggest it is caused by a parasite called Vermiform.
More studies have shown that many different pathogens are present in infected shrimp, such as bacteria (Vibrio), parasites, viruses.
Diagnosis: Diseased shrimp produce white feces, often with a soft shell. A few days after infection, the shrimp will weaken and die.
We should take the following aspects to determine the exact cause of the disease so that appropriate measures can be taken.
First, the easiest way to do this is by cutting the shrimp's intestines and looking under a microscope to see if there is a parasitic infection.
If the shrimp are not infected with parasites, check the pond for total Vibrio, if the Vibrio density is too high, it may be caused by Vibrio.
Clinical signs of WFS:
(a) White feces floating on the water surface
(b) White feces on the feed table
(c) The stomach is white
(d) The intestines are yellow-brown
(e) The state of the feces under the microscope
Shrimp hepatopancreas tissue observed under a microscope:
(a) low magnification image showing 3 worms in hepatopancreatic cells
(b) high magnification image showing worms with spore-like structures
(c) stained parasites at high magnification showing cell membrane structure.
Hepatopancreas after H&E staining of the hepatopancreas shows worm-like morphology and spore-like structures.
Cells are isolated from diseased shrimp intestines.
Preventing disease: Because there are many causes of white stool disease, targeted preventive measures should be taken.
Thai experts recommend that shrimp farmers should reduce the breeding density in hot weather. This has the benefit of reducing the amount of organic matter at the bottom of the pond and reducing the growth of Vibrio. In addition, some shrimp farmers have successfully controlled the disease by using probiotics containing Bacillus subtilis to limit the growth of Vibrio.
Polyculture of tilapia and shrimp is also very effective in controlling Vibrio growth in ponds. In order to control bacterial infection, good effect can be obtained by using garlic at a dose of 5-10g/1kg feed.
VI. Taura Syndrome (TSV)
Cause: A disease caused by the Taura Syndrome Virus (TSV).
Diagnosis: Infected P. vannamei are red, especially the tail. In addition, shrimp have other signs such as a soft shell and an empty gut.
Taura Syndrome is highly lethal (usually 40% to 90% fatal) and spreads rapidly.
Prevention of disease: Use general prevention methods, similar to the prevention of WSSV and yellow head disease, in selecting pathogen-free seedlings by PCR testing, or selecting seedlings without SPF (Specific Pathogen Free).
VII. White tail disease, the muscles are opaque
Causes: There are many reasons for the white tail and opaque muscles. A common symptom of this disease is the whitish tail of the tail and the opacity of the whole or part of the shrimp body.
Diseases caused by stress: For example, when the feeding table is placed in the pond at high temperature, the body bends.
All the aerators are turned off, and then the aerator is turned on, which will cause the shrimp to be stressed, and the body will bend and turn white, so farmers should keep 1-2 aerators when feeding or at other times.
Diseases due to transport: After boarding the transporter after harvest, the shrimp are usually stressed, some or all of the muscle is white, or occasionally there is an abnormal combination of white and dark color, most of these shrimp die, and a few shrimp also recover It is relatively slow and takes a few days to return to normal.
Diseases due to low dissolved oxygen: When oxygen levels are low, most shrimp show signs of whitening of the muscle tissue, and some shrimp also have white legs.
Disease due to infection: In addition to the above, shrimp may also have opaque muscles due to pathological reasons.
Currently, there are many studies identifying the cause of opaque disease in P. vannamei due to shrimp diseases such as bacterial spores or viruses, Vibrio infections (“bacterial whitetail” of Vibrio harvey infection).
In farming areas with relatively high salinity (25-35‰), shrimp will turn white in some parts of the body, but not due to stress, but usually caused by microsporidia.
Prevention of disease: So far, there is no treatment, but comprehensive preventive measures are the mainstay.
Clinical signs of whitetail disease in Penaeus vannamei:
(a) Signs of white-tail disease in a pond
(b) Symptoms of white-tail disease after shrimp infection with Vibrio harveii in the laboratory.
White prawn muscles are due to bacterial spore infection.
VIII. Black spot disease (NHPB)
Cause: It is a disease caused by bacteria.
Diagnosis: The disease occurs due to harsh environmental conditions, especially dirty bottoms of ponds with high levels of toxic gases such as NH3, NO2 in the water.
If ponds are not treated immediately, mortality rates of up to 95% occur within 15 to 30 days from the date of discovery.
Black spots appear on white shrimp.
White prawns recover after molting.
Education: MBBS, MD
Occupation: Medical Doctor
Specialization: Community Medicine, General Surgery, Natural Treatment
Experience: 18 Years as a Medical Practitioner
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