Parasitic Diseases of Fish

Question 1

important pathogens of cultured fish

Answer 1

Parasites with direct life cycles

*indirect life cycles frequently use fish as intermediate hosts.

Question 2

.

most common parasites of fish

Answer 2

protistans

*direct life cycles

Question 3

most common external parasites of fish.

Answer 3

Ciliates

• divide by binary fission.
• motile, attached, or found within the epithelium.

*Ichthyophthirius multifiliis

Question 4

I multifiliis

• cannot survive without the presence of living fish.
• transmitted horizontally via direct exposure to infected fish or via fomites (nets, etc).
• invades epithelial tissue of gills, skin, or fins, leaving a small wound and visible white spot or nodule where each parasite encysts.

Answer 4

cause
Ich” or “white spot disease
*Fish that survive serve as a source of infection to previously unexposed individuals

Question 5

It is large (0.5–1 mm), round, covered with cilia, and has a characteristic horseshoe-shaped macronucleus.

Its characteristic movement varies from constantly rotating to ameboid-like.

Answer 5

1. Ciliates:

a. “Ich” or “white spot disease

Question 6

DOC fo “Ich” or “white spot disease

Answer 6

Formalin or copper

26ocevery 2-3 days

Question 7

hundreds of immature parasites
released by adults i multifiliis

find host for sp time frame
days - warm water fish
weeks - cold water fish

Answer 7

tomites)

Question 8

commonly known as “slimy skin”

• lose condition
• copious mucous secretions

Answer 8

Chilodonella spp
*Has a marine counterpart,Brooklynellaspp

• If gills are heavily infested show signs of respiratory distress, including rapid breathing and coughing.
• Infected fish may be irritated as evidenced by flashing (scratching) and decreased appetite.

Question 9

can be easily identified from fresh biopsies of infected tissues
*0.5–0.7 mm, are somewhat heart-shaped with parallel bands of cilia, and move in a characteristic slow spiral

Answer 9

chillodonella

*

Question 10

move along the surface of infested tissue and appear as little saucers or,
from a lateral view, as little bubbles.

Answer 10

Trichodinids collective term peritrichius cilate

• body of the organism may be cylindrical, hemispherical, or discoid.
• characterized by an attaching disc with a corona of denticles on the adoral sucker surface
• poor sanitation and/or overcrowding,

Question 11

pear-shaped and 10–20 μm long, with longitudinal rows of cilia and inconspicuous cytostomes.

• motile and surface dwelling
• found also skeletal muscle and ocular fluids.
• develop extreme exophthalmos

Answer 11

Tetrahymena corlissi
eliminated with chemical tx and sanitation
- established internally - not treatable

Question 12

teardrop-shaped ciliates (scuticociliates) that, although primarily found on external tissues, can be very invasive.

Answer 12

UronemaandMiamiensis

Question 13

sessile peritrichs that do not feed on the fish host; instead, they attach to the fish, which is often debilitated, and use their cilia to filter and ingest bacteria and small microorganisms in the water column.

Answer 13

Ambiphyra,Apiosoma, andEpistylisspp - 
*low numbers, they cause little harm
*high numbers they can cause irritation
*presence on a fish 
 indicates a rich, organic environment
*Salt can also be used to help control

Question 14

colonial stalked peritrichs

Answer 14

Epistylis,Vorticella, andCarchesium

Question 15

some of the most common and smallest (~15 × 5 μm) flagellated protistan parasites of the skin and gills.

Answer 15

Ichthyobodospp

• kinetoplastid protist, they are flattened, pear-shaped organisms with two flagella of unequal lengths.
• broad geographic range

Question 16

move in a jerky, spiral pattern

*Once attached, the organism can be difficult to see, but movement typical of a flickering flame

Answer 16

Ichthyobodo
*skin often has a steel-gray discoloration due to copious mucus production (“blue slime disease”), and gills may appear swollen.

Question 17

Ichthyobodois readily controlled with

Answer 17

salt, formalin, copper sulfate, or potassium permanganate baths

Question 18

parasitic dinoflagellate and one of the most serious health problems of captive marine.

Answer 18

Amyloodiniumspp
*produce a disease been
called “velvet,” “rust,” “gold-dust,” and “coral disease” because of the brownish gold color they impart to

Question 19

The pathogenic stages of the organism Amyloodiniumspp

Answer 19

are pigmented, photosynthetic, nonflagellated, nonmotile algae that attach to and invade the skin and gills during their parasitic existence.

Question 20

When mature, these parasites give rise to cysts that contain numerous flagellated, small, free-swimming stages that can initiate new infections

Answer 20

Amyloodiniumspp

*problematic in clownfish.

Question 21

TX:Amyloodiniumspp

Answer 21

Copper sulfate is the only therapeutic option for food

*treatment of choice in ornamental fish ischloroquine, delivered at 10 mg/L as an indefinite bath.

Question 22

freshwater counterpart of Amyloodinium and is less common but can also result in high mortality.

Answer 22

Piscinoodiniumspp

Question 23

share some morphologic traits with the true fungi, but more closely related to diatoms, opalinids, and labyrinthulomycetes.

Answer 23

Oomycota: oomycetes (water molds)
*associated with disease in freshwater fishes;
A. Saprolegnia
B. Aphanomyces

Question 24

commonly infects fish eggs and traumatized external tissues of live fishes.

Answer 24

. Saprolegnia

Question 25

agar is acceptable for primary isolation of oomycetes, including the genusSaprolegnia.

Answer 25

Sabaroud’s dextrose agar

Question 26

treatment for external saprolegniasis

Answer 26

potassium permanganate,
formalin, or
hydrogen peroxide, and
malachite green

Question 27

Causes Epizootic ulcerative syndrome (EUS) - a reportable disease and endemic to much of the USA.

Answer 27

Aphanomyces invadans

Question 28

1. Flagellates
   common, small (~9 μm), bilaterally symmetric, flagellated (four pairs) diplomonad protists most frequently found in the intestinal tract of finfish.

Answer 28

Spironucleusspp -

Cichlids are highly susceptible

metronidazole(use only in ornamental species),

Question 29

slender, elongated (6–20 μm), actively motile, biflagellated kinetoplastid protistans easily detected in fresh blood and tissue smears of both marine and freshwater finfish.

Answer 29

Cryptobia and Trypanosomaspp

Cryptobia iubilans - associated with granulomatous disease in African cichlids and discus.

CS: severe weight loss and cachexia.

Clinically affected fish should be culled.

Question 30

Hematozoic forms are generally described asTrypanosomaand have a well-developed undulating membrane

Answer 30

*Trypanosoma;
transmitted by leeches and have been associated with anemia in blue-eyed plecostomusPanaque suttoniand other wild-caught loricariids.

Question 31

Species of the genera Coccidiosis

Answer 31

Cryptosporidium,
Eimeria, and
Goussia

Question 32

Eimeriaspecies are found in

Answer 32

skates and rays.

Question 33

has caused high mortality in cownose rays (Rhinoptera bonasus), although it has been reported in other species of rays

Answer 33

E southwelli

*: toltrazuril 10 mg/kg/day, PO, for 5 days may help control but not eliminate infection.

Question 34

has been associated with high mortality in comet goldfish (Carassius auratus).

Answer 34

Goussia:

*Clumps of cells in the intestine can be visualized

Question 35

. Metazoan Parasites – common in both wild and cultured include

Answer 35

. Myxozoans,
2. Helminths, and
3. Crustaceans
as intermediate or transport hosts for larval parasites of many animals, including people.

Question 36

multicellular and closely related to Cnidaria.

Answer 36

Myxozoans

• use invertebrates as definitive hosts and fishes for multiplication.
• host- and tissue-specific

Question 37

Metazoan Parasites

Two groups infective to fishes

Answer 37

. Myxosporea - usually have an indirect life cycle, with oligochaete or polychaete worms used as a definitive host
2. Malacosporea - bryozoans are used as a definitive host

Question 38

Two important myxosporean infections of ornamental fish

Answer 38

Renal dropsy of goldfish” - caused by the myxosporeanSphaerospora auratus.

Question 39

myxosporean occasionally found in ornamental fish

Answer 39

. Henneguya

*: white nodular lesions that are usually found in gill tissue and may be grossly visible

Question 40

Myxosporean diseases significant in aquaculture include ;

Answer 40

Whirling disease and proliferative kidney disease of salmonids

2. Proliferative gill disease (“hamburger gill disease”) of channel catfish.

Question 41

Whirling disease - caused by

Answer 41

Myxobolus cerebralis

• Fish are infected as fingerlings when the parasite infects cartilage in the vertebral column and skull, resulting in visible skeletal deformities.
• Recovered fish remain carriers

Question 42

have direct life cycles and are common, highly pathogenic, and obligatory parasites most commonly seen on skin and gills.

Answer 42

. Monogeneans
The preferential location of some species is in internal organs such as the esophagus, stomach, posterior kidney, or urinary bladder.