Of course.

Based on the "Health Management in Aquaculture" textbook you provided, here is the
complete information organized according to your outline.

***

**I. Disease Development**

**A. Definition and impacts of Disease**

* **Definition:** Disease is defined as any abnormality in structure or function displayed by

living organisms, which can be identified through a specific or non-specific sign (symptom). The
development of disease in aquaculture involves a complex interaction between three factors:
the host (the farmed animal), the pathogen (disease-causing organism), and the environment. A
disease state occurs when a potential pathogen and a susceptible host are present under
environmental conditions that either increase the pathogen's virulence or decrease the host's
resistance.

* **Impacts:** Disease outbreaks are a major deterrent to sustainable aquaculture production.

The impacts are severe and multi-faceted, including:

* **Production Losses:** Reduced growth rates and lower harvest volumes.

* **Economic Losses:** High mortalities can lead to a total loss of investment. For example,
the textbook cites viral diseases in shrimp causing billion-dollar losses in Asia.

* **Product Rejection:** Diseased aquatic products are often rejected in markets, leading to
a loss of productivity and income.

* **Industry Collapse:** Persistent and widespread disease can cause the collapse of entire
aquaculture ventures and threaten the sustainability of the industry as a whole.

**B. Phases of Disease Development**

The development of disease, particularly under stressful conditions, occurs in three phases:

1. **Alarm Stage:** The initial phase where the fish or crustacean attempts to escape from the
stressful condition or problem.

2. **Adaptive Stage:** If escape is not possible, the animal's body attempts to react and adjust
to the environmental change to reach a new equilibrium. While the animal may survive, its
growth, reproductive capacity, and immunity are often compromised, making it more
susceptible to disease.

3. **Exhaustion Stage:** If the environmental change is too great for the animal to adapt, its
stress response finally reaches an exhaustion stage, leading to a breakdown of normal
functions and ultimately, death.

**C. Immunological and Molecular Techniques in Disease Diagnosis**

These are sensitive methods used for detecting and identifying a wide range of infectious
diseases in fish and shrimp.

* **Immunological Techniques:** These methods use antigen-antibody reactions to detect a

specific pathogen or the host's immune response to it. Key techniques mentioned include:

* **Agglutination:** One of the most common tests where particulate antigens (like bacteria)
are clumped together by antibodies.

* **Precipitation:** A reaction where soluble antigens and antibodies form a visible

precipitate. This includes single and double diffusion methods in agar gel.

* **Immunoelectrophoresis:** Combines electrophoresis to separate antigens with

immunoprecipitation for higher resolution and identification.

* **Fluorescent Antibody Technique (FAT):** Uses fluorescently labeled antibodies to

visualize and detect specific pathogens in tissue samples.

* **Enzyme-Linked Immunosorbent Assay (ELISA):** A highly sensitive technique that uses

enzymes attached to antibodies to detect and quantify antigens or antibodies.

* **Western Blot:** Separates proteins by electrophoresis and then uses antibodies to

identify specific protein antigens, offering high specificity.

* **Molecular Biology Techniques:** These methods focus on detecting the nucleic acids (DNA
or RNA) of pathogens.

* **Gene Probe Assays:** Use a labeled, single strand of DNA or RNA (a probe) to bind to a
specific target sequence of a pathogen. This includes techniques like dot blot, slot blot,
Southern blot (for DNA), and Northern blot (for RNA).

* **Polymerase Chain Reaction (PCR):** A powerful technique that exponentially amplifies a

specific target DNA sequence, allowing for the rapid and highly sensitive detection of a virus or
bacterium even from a very small sample. This includes variations like Reverse Transcription-
PCR (RT-PCR) for detecting RNA viruses and Nested PCR for increased sensitivity.

**D. Surveillance and Monitoring**

This is a critical practice for early disease detection and management at the farm or hatchery
level. It involves:

* **Regular Monitoring:** Consistently observing cultured populations, feed consumption, and

environmental parameters (like water quality) to detect any changes or abnormalities from the
norm.

* **Record Keeping:** Maintaining detailed records of the normal health status, growth, and
environmental conditions is vital. Without this baseline, deviations indicating the onset of a
problem cannot be accurately assessed.

* **Pattern Analysis:** When a disease outbreak occurs, data on the pattern of losses (e.g.,
sudden explosive die-off vs. prolonged low-level mortality), the species and sizes affected, and
the duration of the epizootic can provide crucial clues to whether the cause is environmental or
infectious.

**E. Biosecurity**

While the textbook does not use the single heading "Biosecurity," it covers its core principles
extensively under disease prevention and control. Biosecurity in aquaculture is a set of practices
designed to prevent the introduction and spread of pathogens. Key measures include:

* **Quarantine:** Isolating all new and imported stock for at least 2-3 weeks to observe for
signs of disease and prevent the introduction of pathogens into a farm or a country.

* **Water Treatment:** Using methods like filtration, UV radiation, ozonation, and chlorination
to create a pathogen-free water supply.

* **Sanitation and Disinfection:** Thoroughly cleaning and disinfecting tanks, ponds, and all
equipment (nets, pails, etc.) between culture periods. Using disinfection footbaths at facility
entrances is also recommended.

* **Use of Specific Pathogen-Free (SPF) Stocks:** Using broodstock and larvae that are
certified to be free of known, serious pathogens to minimize the risk of vertically transmitted
diseases.

* **Control of Vectors and Pathogen Sources:** Preventing the entry of wild fish, crustaceans,
and other potential carriers into the culture system.

---

**II. Bacterial Diseases**

**A. Characteristics of Bacteria**

Bacteria are unicellular, prokaryotic (lacking a nuclear membrane) microorganisms found

everywhere in the aquatic environment. They are typically 0.5 to 10 microns in size. Most
bacterial agents in aquaculture are considered secondary or opportunistic pathogens, causing
disease only when the host is stressed or weakened. They reproduce asexually by binary fission
and are classified based on cell shape (cocci, bacilli, spiral), groupings (e.g., strepto-, staphylo-),
and Gram stain reaction (gram-positive or gram-negative).

**B. Koch's Postulates**

These are four criteria used to definitively establish a causal relationship between a specific
microorganism and a disease:

1. The organism must be found in all cases of the disease, and its distribution in the body
should match the lesions observed.

2. The organism must be cultivated in a pure culture outside the body of the host.

3. The isolated organism in pure culture should reproduce the disease when introduced into
other susceptible animals.
4. The organism must be re-isolated from the experimentally infected animal.

**C. Important Bacterial Diseases in Fish**

* **Columnaris Disease:** Caused by *Flavobacterium columnare*. Affects species like tilapia,

carp, and catfish.

* **Edwardsiellosis (Edwardsiella Septicaemia):** Caused by *Edwardsiella tarda*. Affects

tilapia, catfish, mullet, and carp.

* **Vibriosis:** Caused by various *Vibrio* species (*V. alginolyticus, V. anguillarum, V.

vulnificus*). Affects grouper, rabbitfish, milkfish, and seabass.

* **Motile Aeromonad Septicemia:** Caused by *Aeromonas hydrophila, A. caviae,* and *A.

sobria*. Affects a wide range of fish including tilapia, catfish, and goldfish.

* **Pseudomonad Septicemia (Red Spot Disease):** Caused by *Pseudomonas fluorescens, P.

anguilliseptica,* and *P. chlororaphis*. Affects milkfish, goldfish, and tilapia.

* **Streptococcal Infection:** Caused by *Streptococcus sp*. Affects seabass, tilapia, and

rabbitfish.

* **Mycobacteriosis (Piscine Tuberculosis):** Caused by *Mycobacterium marinum, M.

fortuitum,* and *M. chelonae*. Affects Siamese fighting fish and other species.

**D. Important Bacterial Diseases in Crustaceans**

* **Filamentous Bacterial Disease (Bacterial Fouling):** Caused by bacteria like *Leucothrix sp.,
Thiothrix sp.,* and *Flexibacter sp.* It appears as a fine, thread-like growth on the body surface
and gills.

* **Shell Disease (Brown/Black Spot):** Caused by shell-degrading bacteria from the genera
*Vibrio, Aeromonas,* and *Pseudomonas*. Characterized by eroded areas on the cuticle.

* **Luminous Bacterial Disease:** A systemic infection caused by *Vibrio harveyi* and *V.
splendidus*. Heavily infected shrimps exhibit a continuous greenish glow in total darkness.

* **Non-luminous Vibriosis:** Caused by other *Vibrio* species like *V. parahaemolyticus* and
*V. alginolyticus*. Leads to general signs of stress, opaqueness of muscle, and high mortality.
---

**III. Viral Diseases**

**A. Characteristics of Virus**

Viruses are ultramicroscopic (10-300 nm), obligately parasitic organisms, meaning they can
only multiply inside a living host cell. A virus particle (virion) consists of a nucleic acid genome
(either DNA or RNA) enclosed in a protein coat called a capsid. The combined unit is the
nucleocapsid. Some viruses also have an outer lipid-based envelope; those without are
considered "naked" viruses. They are transmitted both horizontally (fish-to-fish) and vertically
(parent-to-offspring).

**B. Major Viral Infections in Fish**

* **Epizootic Ulcerative Syndrome (EUS):** A complex disease associated with a rhabdovirus,

the bacterium *Aeromonas hydrophila*, and the fungus *Aphanomyces invadans*. Affects a
wide range of freshwater fish like snakehead and catfish.

* **Channel Catfish Virus Disease (CCVD):** Caused by *Herpesvirus ictaluri*. Affects channel
catfish.

* **Grass Carp Hemorrhagic Disease:** Caused by an Aquareovirus. Affects grass carp and
other cyprinids.

* **Spinning Tilapia (ST) Syndrome:** Caused by an Iridovirus. Affects various tilapia species.

* **Viral Nervous Necrosis (VNN):** Also known as Viral Encephalopathy and Retinopathy
(VER), caused by a Nodavirus. Affects grouper, seabass, and a wide range of other marine fish.

* **Lymphocystis Disease:** Caused by an Iridovirus. Affects seabass (*Lates sp.*) and

rabbitfish (*Siganus sp.*).

* **Grouper Iridovirus of Taiwan Disease (TGIV):** Caused by an Iridovirus. Affects grouper

(*Epinephelus sp.*).
* **Sleepy Grouper Disease (SGD):** Caused by an Iridovirus. Affects grouper (*Epinephelus
tauvina*).

**C. Major Viral Infections in Crustaceans**

* **White Spot Syndrome Virus (WSSV) Disease:** Caused by a Baculovirus. Affects all stages
of penaeid shrimps and other crustaceans. Characterized by distinct white spots on the
exoskeleton and causes massive mortalities.

* **Yellow Head Virus (YHV) Disease:** Caused by a Rhabdovirus. Affects subadults and
broodstock of shrimp like *Penaeus monodon*. Characterized by a light yellowish, swollen
cephalothorax.

* **Monodon Baculovirus (MBV) Disease:** Caused by a *P. monodon*-type baculovirus.

Affects primarily the giant tiger prawn, causing destruction of the hepatopancreas.

* **Infectious Hypodermal and Hematopoietic Virus (IHHNV) Disease:** Caused by a

Parvovirus. Affects a wide range of penaeid shrimps and can lead to Runt Deformity Syndrome.

* **Hepatopancreatic Parvo-like Virus (HPV) Disease:** Caused by a Parvovirus. Affects

postlarvae and juveniles of many penaeid shrimp species, causing loss of appetite and retarded
growth.

**IV. Fungal Diseases**

**A. Characteristics of Fungi**

* Fungi are heterotrophic organisms (they cannot produce their own food) that lack chlorophyll.

* They are filamentous and multicellular, though some can be unicellular. Their body is
composed of filaments called **hyphae**, which can be **septate** (divided by cross-walls) or
**non-septate** (coenocytic). A network of hyphae is called a **mycelium**.

* They exhibit absorptive nutrition and can utilize almost any carbon source. Many are
**saprobes** (feeding on decaying organic matter) or **parasites**. Some are **facultative
parasites/saprobes** (can live on both living and dead matter), while others are **obligate
parasites** (can only live on living hosts).
* The group responsible for most fungal diseases in aquatic animals are the **straminipilous
organisms** (or oomycetes/lower fungi), which have cell walls made primarily of cellulose,
unlike higher fungi which have chitin.

**B. Major Fungal Diseases in Fishes**

* **Saprolegniosis (Saprolegniasis):** Caused by *Saprolegnia spp., Achlya spp.,* and

*Aphanomyces spp.* It appears as a white cottony growth on fish eggs or any area on the
surface of freshwater fish like carps and goldfish. It is generally progressive and terminal, with
affected fish becoming lethargic.

* **Epizootic Ulcerative Syndrome (EUS):** A complex disease associated with the fungus
*Aphanomyces invadans*, a rhabdovirus, and the bacterium *Aeromonas hydrophila*. It affects
over 30 species of freshwater fish, causing deep, ulcerative lesions on the body.

* **Branchiomycosis (Gill Rot):** Caused by *Branchiomyces spp.* Affects carps, goldfish, and
eels. Fungal hyphae obstruct blood circulation in the gills, leading to necrosis and making gills
appear pale with brownish areas. It can cause rapid, high-mortality outbreaks.

* **Ichthyophoniasis (Ichthyosporidiosis):** Caused by *Ichthyophonus sp.* It affects groupers,

trouts, and flounders. It causes the formation of whitish nodules in internal organs like the
spleen, liver, and kidney, leading to loss of appetite and emaciation.

**C. Major Fungal Diseases in Crustaceans**

* **Larval Mycosis:** Caused by *Lagenidium spp., Sirolpidium spp.,* and *Haliphthoros spp.*
It is a lethal, systemic infection in larval stages of shrimps and crabs, causing sudden and high
mortalities (up to 100% within 48-72 hours).

* **Black Gill Disease (Fusarium Disease):** Caused by *Fusarium solani*. This opportunistic
pathogen infects damaged tissues, especially the gills, in penaeid shrimps, leading to the
appearance of "black spots" and progressive lesions.

* **Aflatoxicosis (Red Disease):** Caused by the ingestion of aflatoxin, a toxin produced by

*Aspergillus spp.* fungi growing on improperly stored feeds. It primarily damages the
hepatopancreas in shrimp, causing necrosis, growth retardation, and a characteristic reddish
discoloration of the body.
**V. Parasitic Diseases**

**A. Characteristics of Parasites**

Parasites are organisms that live at the expense of another organism (the host). In aquaculture,
they are significant disease agents. They can be **ectoparasites** (living on external surfaces
like skin and gills) or **endoparasites** (living in internal organs). Their life cycles can be
**direct** (requiring only one host) or **indirect** (requiring one or more intermediate hosts to
reach the final host). Understanding these life cycles is crucial for prevention and control.

**B. Common Fish Diseases Caused by Parasites**

* **Protozoan Infestations:**

* **White Spot Disease ("Ich") or Ichthyophthiriasis/Cryptocaryonosis:** Caused by the

ciliates *Ichthyophthirius multifiliis* (freshwater) or *Cryptocaryon irritans* (marine). Appears as
white spots on the skin and gills.

* **Trichodiniasis:** Caused by saucer-shaped ciliates like *Trichodina*. Attaches to gills

and skin, causing irritation and excess mucus.

* **Flagellate Infestations:** Caused by flagellates like *Amyloodinium* ("velvet disease"),

*Trypanosoma*, and *Cryptobia* (blood parasites), and *Ichthyobodo*. They cause various
signs from skin lesions to anemia.

* **Monogenean Infestations:** Caused by ectoparasitic flatworms like *Gyrodactylus* and

*Dactylogyrus*. They attach to gills and skin with hooks, causing extensive damage and
affecting respiration.

* **Digenean Infestations:** Caused by endoparasitic flatworms like *Bucephalus* and

*Transversotrema*. They form cysts (metacercariae) in the skin, gills, and muscles.

* **Cestode (Tapeworm) Infestations:** Caused by endoparasitic tapeworms like

*Botriocephalus*. They live in the intestine, causing emaciation and reduced food intake.

* **Nematode (Roundworm) Infestations:** Caused by unsegmented roundworms like

*Spirocamallanus*. They parasitize the stomach and intestine.

* **Acanthocephalan (Thorny-headed worm) Infestations:** Caused by thorny-headed worms

like *Acanthocephalus*. They attach to the intestinal wall, causing ulcers.

* **Crustacean Infestations:**

* **Argulus (Fish Louse) Infestation:** Caused by the louse *Argulus*. Attaches to skin and
fins, causing hemorrhagic wounds.

* **Caligus (Sea Lice) Infestation:** Caused by copepods like *Caligus epidemicus*. Appear
as transparent patches on skin and gills.

* **Ergasilid Infestation:** Caused by the copepod *Ergasilus*. Attaches firmly to gills,

causing respiratory dysfunction.

* **Lernaeid (Anchor Worm) Infestation:** Caused by the copepod *Lernaea*. Burrows its
head into the fish's skin, causing ulcers and swelling.

* **Isopod Infestation:** Caused by isopods like *Alitropus* and *Nerocila*. These larger
parasites attach to the skin, mouth, and gills, destroying host tissue.

* **Marine Leech Infestations:** Caused by leeches like *Zeylanicobdella arugamensis*. They

attach to the skin and fins to feed on blood, causing hemorrhage and anemia.

* **Mollusc Infestation:** Caused by the larval stage of freshwater bivalves called **glochidia**,
which attach to gills and outer surfaces, destroying gill tissue.

**C. Common Crustacean Diseases Caused by Parasites**

* **Protozoan Infestation (Fuzzy Mat):** Caused by ciliates like *Vorticella*, *Zoothamnium*,

and *Epistylis*. These attach to the exoskeleton, especially the gills, causing respiratory
difficulties.

* **Sporozoans (Gregarines):** Caused by sporozoans like *Gregarines*. They attach to the

digestive tract of penaeid shrimps, interfering with filtration and causing growth retardation.

* **Microsporeans ("Milk" or "Cotton" Shrimp Disease):** Caused by intracellular parasites like

*Nosema* and *Pleistophora*. They infect muscles and ovaries, turning them opaque white and
causing sterility.

**VI. Environmental and Nutritional Diseases**

**A. Fish Diseases Associated with Physico-chemical Properties of Water**

* **Gas Bubble Disease:** Caused by supersaturation of dissolved gases (nitrogen or oxygen)

in the water. Bubbles form in the fish's blood and tissues, causing embolism and death.

* **Swimbladder Stress Syndrome (SBSS):** Associated with malfunction of the swimbladder

due to a combination of factors like handling and dense algal blooms. Larvae show a large gas
bubble and have high positive buoyancy.

* **Asphyxiation/Hypoxia:** Caused by very low levels of dissolved oxygen. Fish gasp at the
surface and show rapid opercular movement.

* **Alkalosis:** Caused by water pH becoming too high (too basic). Leads to corroded skin and
gills.

* **Acidosis:** Caused by a drop in water pH to a level that is too low. Leads to rapid
swimming, gasping, and increased mucus secretion.

* **Sunburn Disease:** Caused by excessive UV irradiation in shallow, uncovered raceways.

Causes ulcerative lesions on the top of the head and fins.

**B. Harmful and Toxic Algae**

Harmful algal blooms (HABs), or "red tides," can cause severe economic losses and public
health problems.

* **Causative Organisms:** Primarily dinoflagellates (*Pyrodinium, Gymnodinium,

Alexandrium*) and diatoms (*Pseudo-nitzschia*).

* **Types of Poisoning in Humans:**

* **Paralytic Shellfish Poisoning (PSP):** Neurotoxic; caused by saxitoxin from

dinoflagellates like *Alexandrium*.

* **Diarrhetic Shellfish Poisoning (DSP):** Gastrointestinal; caused by dinoflagellates like

*Dinophysis*.

* **Amnesic Shellfish Poisoning (ASP):** Neurotoxic; caused by domoic acid from diatoms
like *Pseudo-nitzschia*.

* **Neurotoxic Shellfish Poisoning (NSP):** Caused by brevetoxins from *Gymnodinium

breve*.
 * **Ciguatera Fish Poisoning (CFP):** Caused by ciguatoxins from dinoflagellates like
*Gambierdiscus toxicus*.

* **Effects on Fish:** Some algae are directly harmful to fish by damaging or clogging their
gills, leading to mass mortality.

**C. Nutritional Deficiency Diseases**

These occur due to a deficiency, excess (overnutrition), or imbalance of essential nutrients in

the diet.

* **Protein and Amino Acid Deficiency:** The most common sign is reduction or cessation of
growth.

* **Fats and Lipids Deficiency:** Can cause depigmentation, fin erosion, and fatty infiltration of
the liver (lipoid liver disease).

* **Vitamin Imbalances:** Each vitamin deficiency has specific signs. For example, **Vitamin C
deficiency** in shrimp causes "black death disease," characterized by melanized nodules and
poor wound healing.

* **Mineral Deficiencies:** Difficult to study, but imbalances in calcium, potassium, and

magnesium can cause spinal abnormalities.

* **Other Feed Quality Problems:** Improper feed storage can lead to rancidity and loss of
vitamins. **Aflatoxicosis**, from moldy feeds, damages the hepatopancreas.

**VII. Disease Prevention and Control Measures**

**A. Physical, Environmental, and Chemical Methods of Disease Prevention and Control**

* **Physical and Environmental Methods (Biosecurity):**

* **Proper Hatchery/Pond Design:** Ensures good water supply, independent drainage, and
protection from pollution and predators.

* **Good Water Quality:** Maintaining optimal levels of salinity, pH, dissolved oxygen, and
temperature.
 * **Sanitary Practices:** Regular cleaning and disinfection of facilities and equipment.

* **Stress Avoidance:** Minimizing handling, overcrowding, and ensuring proper nutrition.

* **Quarantine and Termination Procedures:** Isolating new stock and safely destroying
infected individuals.

* **Chemical Methods:**

* **Prophylactic Treatments:** Protective measures to prevent disease, such as disinfecting

water, feeds, and hosts.

* **Disinfecting Rearing Water:** Using chlorine or ozone.

* **Disinfecting Feeds:** Decapsulating *Artemia* cysts with chlorine or formalin.

* **Disinfecting Hosts:** Using formalin, detergent, or Treflan dips for eggs, larvae, and
spawners.

* **Chemotherapy (Treatment):** The use of drugs and chemicals as a "last resort" for
treating infectious diseases.

* **External Methods:** Applied via immersion (dip, short bath, long bath, flush) for
ectoparasites.

* **Systemic Treatment:** Chemicals added to feed to treat internal infections.

* **Parenteral Treatment:** Direct injection (intramuscular, intraperitoneal, intravenous)

for high-value fish.