pathology

major concern for culturists

1. diseases and parasites

what happens when pathogens or parasites appear in open systems? 

1. offending organisms can be transmitted to wild individuals

what two main parts of fish immune systems break down into? 

1. protection from physical invasion

2. internal pathogen handling

form of physical protection for fish

1. scales and layers of the dermis and epidermis

what does mucus covering on fish do? 

1. contains bactericides and fungicides, adds additional physical protection

2. constantly renewed

3. sheds off debris and discourages parasites from attaching themselves to the fish

how can pathogens enter a fish's body? 

1. physical injury or the digestive tract

products in fish blood that provide general immunities

1. antiviral chemicals → interferons

2. C-reactive proteins

what are interferons? 

1. antiviral chemicals

what are c-reactive proteins?

1. products in fish blood that immediately attack bacteria and viruses

how does colder water affect the efficiency of a fish’s immune system? 

1. colder water slows down the immune system

what behavior do infected fish exhibit? 

1. “fever symptoms” → head for warmer areas 

what do white blood cells do when a pathogen is detected? 

1. attracted to the area, pick up foreign bodies, take them to the spleen and kidney for handling

what do the kidney and spleen make to help fight antigens? 

1. antibodies, specifically built to fight particular antigens

three ways antibodies attach themselves to their antigen and fight it:

1. detoxify it → white blood cells can ingest and destroy it

2. attract a compliment → another blood component that helps destroy the antigen

3. deactivate reproduction → stop the antigen proliferating

what is an antigen? 

1. toxin or other foreign substance

why do most fish respond to primary antigenic challenges by producing specific antibodies? 

1. response to secondary challenge is generally faster and of greater magnitude

why invertebrates and antibodies

1. cannot make antibodies → therefore cannot be successfully vaccinated

what is the first line of defense against pathogens that crustaceans have?

1. body covered by chitin that is largely calcified

what happens when a pathogen penetrates the chitin layer of crustaceans? 

1. minute quantities of pathogen associated molecular patterns trigger recognition by the pattern recognition receptors 

what is in the hemolymph of crustaceans?

1. prophenoloxidase activating system and associated factors are both important mediators of crustacean immunity

what is another name for the prophenoloxidase activating system? 

1. proPO-system

what is the proPO-activating system triggered by? 

1. the presence of minute amounts of compounds of microbial origins ensures the system will become active in the presence of potential pathogens

what does the proPO system lead to? 

1. melanization of pathogens that are then disabled

what organisms do mollusks share defense mechanisms with? 

1. Arthropods

how are mollusks natural immunity process formed?

1. by anatomical and chemical protective barriers that prevent damage of the underlying tissues, body fluid losses, and the infections of pathogenic microorganisms and parasites

main physical barrier of mollusks? 

1. shell and mucus which cover the soft body of mollusks

what are body coverings of mollusks supported by? 

1. blood clotting and wound healing

what are internal defense mechanisms of mollusks? 

1. cellular reactions such as: phagocytosis, nodule formation, encapsulation, pearl formation, and cell atrophy / death followed by tissue liquefaction

what is phagocytosis? 

1. cell engulfs and destroys foreign concepts

what is nodule formation?

1. cellular immune response that destroys large invaders 

what is encapsulation? 

1. isolates and walls off foreign materials

what is the most numerous active blood cell type in mollusks? 

1. granulocytes

how are small invaders eliminated in mollusks? 

1. phagocytosis

how are numerous and large invaders eliminated in mollusks? 

1. nodule formation or encapsulation

what are lectins? 

1. carbohydrate-binding proteins to bind the glycans of glycoproteins and glycolipids with high affinity

2. play crucial roles in the innate immune responses of invertebrates by recognizing and eliminating pathogens

examples of what a pathogen can be: 

1. virus

2. bacteria

3. fungi and fungi-like organisms

4. protists

5. metazoans

what are metazoans? 

1. external and internal parasites

what do true viruses contain? 

1. nucleic acid → either DNA or RNA and protein

what do nucleic acids do in viruses? 

1. encode genetic information unique for each virus

what is the infective, extracellular form of a virus? 

1. virion

what does a virion contain?

1. contains at least one unique protein synthesized by specific genes

what is a capsid? 

1. a shell around nucleic acid in virtually all viruses

what forms a capsid? 

1. protein

types of viruses

1. icosahedral

2. enveloped

3. helical

4. more complex structure 

how do viruses not grow and grow? 

1. they do not grow through cell division

2. they use machinery and metabolism of a host cell to produce new copies of themselves

what happens with a virion after a virus infects a host cell? 

1. virion uses the cell’s ribosomes, enzymes, ATP, and other components to replicate

two methods of how viruses take over host cells

1. some RNA viruses are translated directly into viral proteins in ribosomes of the host cell. host ribosomes treat the viral RNA as though it were the host’s own mRNA

2. some DNA viruses are first transcribed in the host cell into viral mRNA. the viral mRNA is translated by host cell ribosomes into viral proteins

what is the main function of ribosomes?

1. protein synthesis → translate genetic instructions from mRNA to assemble amino acids into proteins

what happens after virions form new virions? 

1. direct the production of an enzyme that breaks down the host cell wall, which allows the virions to burst out of the cell

two pathways for transmission of viruses and other pathogens:

1. horizontal transmission

2. vertical transmission

what is horizontal transmission? 

1. pathway for transmission of viruses and other pathogens

2. viruses are transmitted among individuals of the same generation

what is vertical transmission? 

1. pathway for transmission of viruses and other pathogens

2. from parent’s gametes to their offspring

what is channel catfish virus caused by? 

1. herpesvirus designated ictalurid herpesvirus 1

what does channel catfish virus cause? 

1. high mortality, reduced growth

what are channel catfish virus outbreaks often associated with? 

1. environmental stress and crowding

what time of year and temperature does channel catfish virus usually occur? 

1. warm summer months, 27℃ or higher

signs of channel catfish virus:

1. convulsive swimming → causes “head-up” posture

2. lethargy

3. swollen abdomen

4. exophthalmos (popeye)

5. hemorrhaging of fins and ventral abdomen

6. hemorrhaging of the musculature, liver and kidneys

what is the experimental antiviral agent for channel catfish virus?

1. Kaempferol 

what is the causative agent of infectious hematopoietic necrosis? 

1. rhabdovirus of the genus Novirhabdovirus 

what fish does infectious hematopoietic necrosis affect? 

1. disease of salmon and trout

visible signs of infectious hematopoietic necrosis:

1. lethargic fish, occasional bouts of frenzied activity, normally precedes death

2. exophthalmic (eyes protruding)

3. external surface of the fish appears dark, pale gills and hemorrhaging at the base of the fins

4. abdomen often swollen

internal signs of infectious hematopoietic necrosis: 

1. internally, the fish will appear generally anemic

2. mucus-like fluid found instead of food in the digestive tract

what does exophthalmic mean? 

1. eyes protruding

treatment of infectious hematopoietic necrosis: 

1. no effective treatment for infected fishes

2. early detection and removal of the infected fishes is the most common practices to contain the spread of IHNV

causative agent of viral hemorrhagic septicemia: 

1. another rhabdovirus of the genus Novirhabdovirus

what species does viral hemorrhagic septicemia afflict? 

1. over 50 species of freshwater and marine fish in several parts of the Northern Hemisphere

2. includes trout, turbot, halibut, yellow perch, sunfish, muskellunge, walleye, northern pike, and a number of minnow species

how does viral hemorrhagic septicemia virus infect fish?

1. shed in the urine and reproductive fluids (ovarian fluids, sperm) of infected fish

when do most viral hemorrhagic septicemia virus outbreaks occur? 

1. in spring when water temperatures are less than 5℃

signs of infection of viral hemorrhagic septicemia: 

1. hemorrhages on the body, eyes, gills, or at the base of the fins

2. bulging eyes

3. swollen, fluid-filled abdomens

4. darkened coloration

5. abnormal swimming behavior

6. hemorrhages may also be seen in the muscle and organ tissues

treatment for viral hemorrhagic septicemia: 

1. there are no effective treatments for VHS infected fishes

2. early detection and removal of the infected fishes is the most common practice to contain the spread of VHS

standard for detection of viral hemorrhagic septicemia

1. virus isolation in cell culture followed by virus identification

other fish viruses: 

1. infectious salmon anemia virus 

2. tilapia lake virus

3. viral erythrocytic necrosis

4. epizootic hematopoietic necrosis

5. red sea bream iridovirus

another term for infectious salmon anemia virus

1. Hemorrhagic kidney syndrome

another term for viral erythrocytic necrosis

1. Piscine erythrocytic necrosis

another term for Ostreid herpesvirus 1

1. Pacific oyster mortality syndrome

what kind of organisms are impacted by Ostreid herpesvirus 

1. oysters of the genus Crassostrea and in other bivalves

transmission of Ostreid herpesvirus occurs via: 

1. water

infection of Ostreid herpesvirus if often lethal for what organisms

1. Pacific oyster spat and juveniles

clinical signs of infection of Ostreid herpesvirus 

1. often develop within 3-4 days after spawning

2. slowed growth

3. reduced feeding; weak

4. circular swimming and / or loss of ability to swim

what time of year does the Ostreid herpesvirus tend to occur in California?

1. summer when water temperatures rise about 24℃

what organisms does gill necrosis virus affect? 

1. European flat oyster, Portuguese oyster and other oyster species

how does gill necrosis virus usually present in Portuguese oysters? 

1. stages of ulcerations of the gill and labial palps

how has gill necrosis virus impacted the culturing of the species?

1. because of the severity of the disease, it is no longer cultured commercially in many areas in Europe, has been replaced by Pacific oysters, which are more resistant to the disease

what is white spot syndrome virus? - genus and family

1. lone virus of the genus Whispovirus - in the family Nimaviridae

what organisms does white spot syndrome virus impact?

1. crustaceans, in farmed shrimp mortality is rapid

signs of white spot syndrome virus:

1. lethargy

2. reduced food consumption

3. white spots over the carapace

4. loosening of the cuticle 

5. discoloration of the hepatopancreas

what is hypertrophied?

1. thickening or enlargement of cells which leads to an increase in the size

what tissues does white spot syndrome virus occur in?

1. all tissues of mesodermal and ectodermal origin

prevention of white spot syndrome virus: 

1. maintenance of good environmental conditions and husbandry practices

2. use of specific pathogen-free post-larvae

what is taura syndrome virus?

1. icosahedral, non-enveloped virus with a single-stranded RNA genome

what family does taura syndrome virus belong to?

1. Dicistroviridae

what nursery phase is taura syndrome virus mainly seen in?

1. Penaeus (Litopenaeus)

what tissues do taura syndrome virus infect?

1. ectoderm- and mesoderm-derived tissues

what organism does taura syndrome virus affect? 

1. shrimp

signs of taura syndrome virus: 

1. irregular black spots, reddish body color

2. anorexia, lethargy, unstable swimming behavior

3. soft cuticle and flaccid body

shapes of bacteria: 

1. spherical - called cocci

2. rod-shaped, called Vibrio - shaped like slightly curved rods or comma-shaped

3. spiral shaped - called spirilla

4. tightly coiled - called spirochaetes

what should the selection of an antibiotic for disease treatment be based on? 

1. results of an in vitro sensitivity test - antibiotic test discs

what is Furunculosis?

1. serious, septicemic, bacterial disease

what fish does furunculosis mainly occur in? 

1. salmonid fishes, but also may occur in goldfish and other cyprinids

what is furunculosis caused by? (genus species)

1. Aeromonas salmonicida

symptoms of furunculosis: 

1. furuncle involving skin and / or muscle, progresses to crater-like lesions

2. hemorrhages on the skin, mouth and fin bases

3. popeye

4. lethargic swimming

5. loss of appetite

6. respiratory distress

7. jumping from the water

genus species of enteric septicaemia of catfish:

1. Edwardsiella ictaluri

what is another term for enteric septicaemia of catfish? 

1. edwardsiellosis

enteric septicaemia infection symptoms:

1. multiple hemorrhages that develop into ulcers

2. loss of appetite

3. abnormal behavior

what antibiotics can help treat enteric septicaemia infection? 

1. terramycin

2. romet

3. aquaflor

what is vibriosis?

1. many Vibrio species are non-pathogenic, however many lead to a variety of diseases

2. among the most common diseases in marine aquaculture

common clinical signs of Vibrio infection in fish:

1. skin lesions and body discoloration

2. hemorrhages

3. lethargy

4. loss of appetite

5. other symptoms depending on bacterial and fish species

prevention methods of Vibrio infection: 

1. antibiotics and probiotics

2. specific bacteriophages

3. antimicrobials from plants and other natural sources

4. vaccines

what is columnaris caused by? (genus species)

1. Flavobacterium columnare

symptoms of columnaris:

1. white to brown, grayish-white, orange-yellow sores on the gills and body

2. sores or ulcers on the fins, head, gills, and body that eventually increase in size and expose underlying muscle

3. white area of affected tissue encircling the body (called saddleback)

two other important fish bacterial pathogens (genus and species):

1. Edwardsiella tarda

2. Aeromonas hydrophila

are bacterial diseases or virus and protozoa diseases more common in crustaceans and mollusks?

1. bacterial diseases are not common - except Vibrio

filamentous bacteria that may cause infection in penaeid shrimp larvae (genus and species):

1. Leucothrix mucor

2. Thiothrix sp

3. Flexibacter sp

4. Flavobacterium sp

5. Cytophaga sp

are fungi eukaryotes or prokaryotes?

1. eukaryotes

examples of fungi: 

1. yeasts, rusts, smuts, mildews, molds, and mushrooms

how do fungi reproduce?

1. asexually by fragmentation, budding, or sexually producing spores

what are the filaments and bodies of fungi called?

1. filaments: hyphae

2. body: mycelia

what are true aquatic fungi frequently regarded as? 

1. secondary tissue invaders 

when do aquatic fungal infections occur?

1. after traumatic injuries, pathogenic agents, or environmental conditions such as poor water quality or low temperatures 

genus of cotton wool fungus

1. Saprolegnia

what is cotton wool fungus?

1. common mold infection of freshwater fish

what is cotton wool fungus characterized by? 

1. thin, cotton-like growth on the skin or gills

2. starts small, spreads quickly into lesions that are white and may turn red, brown, or green

what is the genus species of “gill rot” disease?

1. Branchiomyces sanguinis, Branchiomyces demigrans

what is another term for “gill rot” disease? why does it have this name?

1. bad-management disease

2. flourishes in poor-quality water with high levels of organic matter

signs of gill rot disease: 

1. fish may appear sluggish or gulping air at water’s surface

2. paler regions of gills indicate sick and dying tissue

compounds that can be used to treat gill rot disease: 

1. hyamine → ammonium salt

2. potassium permanganate

3. roccal → disinfectant

4. clotrimazole and clove oil have been effective treatments

what fungus-like organism (genus species) is Icthyophonus caused by? what class does it belong to?

1. icthyophonus hoferi

2. belonging to Class mesomycetozoea

what temperatures does Ichthyophonus flourish in? 

1. cool temperatures, between 36 to 68 ℉

how is Ichthyophonus spread? 

1. via cannibalism of sick fish and discharge of cysts in waste

how can Ichthyophonus be treated? 

1. potassium permanganate

2. anti-fungal ketoconazole has been effective experimentally

what organisms does larval mycosis affect? 

1. crustaceans

what are two species (genus species) that cause larval mycosis? 

1. Lagenidium spp., Sirolpidium spp

prevention of mycosis

1. hatchery water hygiene through UV treatment and filtration 

two other names for black gill disease:

1. black spot disease 

2. black death

what genus species is black gill disease primarily caused by?

1. Fusarium solani

how does black gill disease present? 

1. circular fungus attaches itself to gill nodules in shrimp

2. affected gills may exhibit crusted, surface corroding, light brown to black spots

prevention and treatment of black gill disease

1. good water quality and avoiding overfeeding

2. treatment → bathing in a concentration of furazolidone

what organisms is black gill disease most common in?

1. shrimp 

what are protists? 

1. eukaryotic organisms that do not fit into the traditional categories of plants, animals, or fungi

what are Trichodina?

1. many species are pathogenic, causes disease called trichodinosis

what organisms does Trichodina infect?

1. almost all fish species 

symptoms of Trichodina:

1. gill swelling

2. lethargic behavior

3. weight loss

4. flashing (underside of fish “flashes” in fish’s attempt to get rid of parasite)

what are Trichodina infestations typically caused by? 

1. high stocking densities and generous feeding rates

what are treatments of Trichodina? 

1. formalin

2. copper sulfate

3. potassium permanganate

what is another name for white spot disease? 

1. Ich

what parasite (genus species) causes white spot disease? 

1. Ichthyophthirius multifiliis

symptoms of fish with ich: 

1. white specks on their skin

2. large amounts of mucus

3. lethargic behavior

4. weight loss

5. flashing

what is flashing?

1. sporadic behavior where a fish tries to get parasite off them

treatments of white spot disease / ich:

1. formalin

2. combination of malachite green and formalin

3. copper sulfate

4. potassium permanganate

5. sodium chloride

6. immunization

what do metazoan parasites include?

1. myxozoans (cnidarians)

2. monogeneans, digeneans, and cestodes 

3. nematodes

4. crustaceans

what is whirling disease caused by (genus species)?

1. Myxobolus cerebralis

what area of fish body does whirling disease impact? 

1. attacks cartilage

what do whirling disease infections in spine cause?

1.  fish’s tail to turn black and spine to curve

what do whirling disease infections in head cartilage cause? 

1. create head and jaw deformities

what do whirling disease infections in auditory capsule cause? 

1. disorientation, chase their tails in a whirling motion

where did whirling disease get its name? 

1. causes disorientation, causes fish to swim in abnormal, whirling motion

prevention of whirling disease: 

1. not stocking fish in potentially infested waters until they are older than 6 months

treatments of whirling disease: 

1. Furacyn or Furan

2. Methylene Blue and sodium chloride bath

3. soak fish food with metronidazole and praziquantel

what are many species of worms to fish? 

1. internal parasites

what type of worm parasite of fish is harmful to humans if ingested?

1. anisakid nematodes can invade the stomach wall or intestine of humans if fish is eaten raw or undercooked

what is a problem in farmed salmon? 

1. sea lice - copepods

what are sea lice

1. copepods that are common on adult salmon

external crustacean parasites have been treated by:

1. freshwater

2. copper sulfate

3. natural extracts of the plant Chrysanthemum

4. emamectin benzoate

5. chitin synthesis inhibitors

what have most licensed fish vaccines been based on?

1. killed or weakened (in their ability to cause disease) microorganisms delivered through injection

what type of vaccines are more effective?

1. live vaccines, as they mimic natural pathogen infection

2. also generate a strong antibody response

what are killed vaccines?

1. inactivated vaccines

how are killed vaccines prepared? 

1. by killing the infectious agent and using it as an antigen to induce an immune response

how are attenuated vaccines prepared?

1. repeated laboratory “passage” of the organisms to lose their virulence without killing them

2. attenuated organisms replicate in the target host without any clinical signs

advancement of DNA vaccines:

1. don’t need to use the antigen as a vaccine, rather an antigen’s gene/genes that code for the suitable proteins are taken by molecular techniques and can be used as a vaccine

methods of administering vaccines: 

1. oral vaccination

2. immersion vaccination

3. injection vaccination

positive of oral vaccination:

1. easy to apply and avoids stress in fish

how can oral vaccination be given?

1. can be incorporated in the feed during production

two disadvantages of oral vaccination: 

1. may not give a uniform protection

2. requires a large dose 

how are immersion vaccinations administered?

1. applied to the surfaces of the fish

2. antigen uptake is via gills, skin, and lateral line

3. fish may be dipped for a short period of time in concentrated vaccine solution, or the vaccine solution may be sprayed onto the fish

positive of immersion vaccination

1. particularly convenient for small fish and fingerlings, which are impractical to handle for injection

2. causes minimal stress in fish

disadvantages to immersion vaccination

1. labor-intensive 

2. expensive to buy tanks 

3. specialized equipment is required

four advantages of injection vaccination

1. results in best protection

2. needing relatively minimal dose because correct dosage calculation is easy

3. multivalent vaccine can be administered

four disadvantages of injection vaccination

1. not suitable for small fishes

2. not suitable for very young stock

3. stress on fish and feed intake reduction

4. damage during injection which may cause multiple deaths in fish

Chloramphenicol

1. class of antibiotic

2. inhibits protein synthesis

Tetracyclines

1. class of antibiotic

2. inhibits protein synthesis

Erythromycin

1. class of antibiotic

2. inhibitor of bacterial reproduction, and the cytochrome P450 system

Fluoroquinolones

1. class of antibiotic

2. interferes with DNA replication by preventing bacterial DNA from unwinding

administration strategies of antibiotics

1. medicated feed (oral administration)

2. injection

3. immersion

extensive use of antibiotics may result in:

1. resistance development

2. adding drugs to the water with or without feeds results in environmental disturbance of the microbiota

chemical alternatives to antibiotics:

1. acetic acid

2. carbon dioxide gas

3. hydrogen

4. sodium chloride

5. garlic

6. onion

7. ice

what are biosecurity measured in aquaculture?

1. any management action to prevent the introduction of disease-causing agents

2. most diseases can be overcome by meticulous application of biosecurity measures

what are the most important approaches to control diseases of fish in aquaculture?

1. stocking density reduction and water treatment

farm-level biosecurity measures involve:

1. strict quarantine measures

2. sanitation of equipment 

3. disinfection of egg

4. water treatments

5. use of clean feed