Protozoans/Parasites

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Protozoans/Parasites
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What We Will Cover Parasitemias

• Flagellated protozoans (P. Mastigophora)
• Flagellated algae (C. Dinoflagellida)
• Ciliates (protozoans)
• Myxozoans (protozoans)
• Digenetic Trematodes (flukes)
• Cestodes (tapeworms)

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(1) Flagellated Protozoans

• Flagellates are protozoans simple,
  single-celled animals (over 50,000 recognized
  species)
• very small (15-30 ?M), body elongate, leaf-like
  appearance, up to 975,000/mL of blood
• flagellum arises posteriorly and can be connected
  to other parts of body, pulls animal through the
  blood
• most famous are Trypanasoma, Trypanoplasma,
  Ichthyobodo necatur

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Ichthyobodo necatur

• A Mastigophoran, but a member of Class
  Diplomonadea
• also small, but flat and ovoid when swimming
• has 2-4 flagella arising from a basal body
  (kinetosome) at anterior end
• obligate parasite, poor swimmer, attaches to
  gills, but not good at attaching
• uses a sucking organelle to penetrate host
• tissue penetrated becomes necrotic

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Icthyobodo necatur

• Largely affects young, undernourished carp and
  trout
• can also parasitize frogs/tadpoles
• wild fish/frogs serve as reservoirs, found
  everywhere
• seasonality affect resulting from salmonid
  hatchery stocking seasons (April - May)
• affects smolts by attaching to gills and not
  allowing them to adapt to seawater

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Ichthyobodo necatur

• Pathogenicity dull spots on body (blue slime),
  pale gills, hemorrhaging, fin necrosis, loss of
  appetite, flashing, moribund fish
• Control salmonids need prophylaxis with
  formalin (14000 for 1 hr) carp need 1 salt
  bath 30 minutes repeated 3-4 times

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Ichthyobodo necatur
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Ichthyobodo necatur
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(2) Flagellated algaeOodinium/Amylodinium

• Members of Subkingdom Protozoa, Phylum
  Mastigophora (flagellates), Class Dinoflagellida
  (dinoflagellates)
• Two major genera Oodinium (freshwater) and
  Amylodinium (saltwater)
• Both attach to skin and gills causing condition
  known as velvet or rust disease (from chlorophyll
  in parasite)

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Morphology of Oodinium, Amylodinium

• Parasitic stage (trophont) is spherical or
  pyriform
• cytoplasm is foamy in appearance due to presence
  of small granules or droplets
• attachment via root-like rhizoids

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Life Cycle of Oodinium/Amylodinium

• Parasitic trophont found on fish for about one
  week feeding on cytoplasm
• eventually retracts rhizoids, drops off and
  encysts
• encysted form known as tomont, hard to kill
  with chemicals
• tomont undergoes mitotic division (8), ultimately
  producing up to 256 dinospores
• one dinospore can equal 1 billion new parasites
• dinospores break out of cyst and seek new hosts

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Life Cycle of Oodinium, Amylodinium
dinospores
tomont
trophont
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Host/parasite Relationship

• Broad specificity sea bream, sea bass, mullet,
  tilapia, striped bass
• wide geographic distribution (here in Gulf of
  Mexico)
• cause little problem in nature, usually result of
  crowding
• outbreaks can be very explosive, Gulf Coast
  Research Lab lost almost all striped bass to this
  in 1976

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Pathology/Control

• Damage due to penetration of rhizoids
• Affects epithelium of skin, gills, nasal
  cavities, eyes and mouth
• Parasites produce lytic excretion causing
  inflammation, sometimes necrosis, secondary
  infections with bacteria/fungi
• Control difficult due to rapid reproduction, no
  apparent acquired immunity, can encyst
• Treatment copper (fair), metronidazole (14
  mg/L)

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Pathology lysis, necrosis of gill epithelia
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(3)Ciliates Ichthyophthirius multifilis (ICH)

• Another single-celled protozoan type
• adult is round in shape, up to 1 mm in diameter,
  known as trophont (rem? Same as Amylodinium)
• short cilia in rows over entire cell, obvious as
  free-living stages tumble through the water
• Life Cycle the trophont attaches to gills or
  skin, after 7-10 days, the trophont drops off and
  is called a tomont (same, also), tomont
  attaches to substrate and encysts, cyst ruptures
  releasing swarmers known as theronts
• theronts are the parasites (have perferatorium),
  also use hyaluronidase, only for less than 20
  hrs, displace normal tissue as they grow

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Ichthyophthirius multifilis (ICH)

• Signs white pustules in advanced cases,
  sometimes called white spot disease if found on
  gills, not found on body
• Behavioral changes fish scratch against bottom
  (flash), hide in corners, twitching fins
• death in 20-26 days, thought to be due to
  osmoregulatory failure in most cases
• Host/parasite range broad, mainly in
  catfish/salmonids

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Ichthyophthirius multifilis (ICH)

• Control prevention (once in, difficult to
  treat)
• chemotherapy requires treating water, not the
  fish (cysts, stages in fish unaffected)
• formalin around 250 ppm, goes up as temp goes
  up
• malachite green 1.25 ppm daily for 30 min
  (Nox-Ich, Ich-out)
• remove fish, raise temp to 90oF

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Ichthyophthirius multifilis (ICH)
Cell embedded in tissue
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Ichthyophthirius multifilis (ICH)
Theronts (swarmers)
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Ichthyophthirius multifilis (ICH)
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Ichthyophthirius multifilis (ICH)
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Cryptocaryon irritans

• Similar to ICH
• primarily marine
• trophozoite similar to ICH
• life cycle similar to ICH
• primarily problem for mariculture facilities and
  marine aquaria

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Epistylus sp.

• Colonial, stalked ciliate
• possess ciliary spiral around cytostome
• usually on skin
• causes flashing, which can lead to harm
• really just a bother, little apparent harm

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Trichodina sp.

• Body shaped like hockey puck
• also spiral cilia around cytostome
• makes them fly through the water like a flying
  saucer
• lives on gills, skin mainly
• have rings of chitinous teeth

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Stop here next time, myxozoans and P.
Platyhelminthes!
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(4) Myxozoans Myxobolus cerebralis

• Rather odd, exclusively endoparasites
• could be Cnidarians (Phylum Cnidaria)
• multicellular during adult life, with various
  cell types
• now dont know what to call them
• anyhow, we will discuss whatever they are in the
  context of what they cause whirling disease
  (Salmonid Whirling Disease)

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Salmonid Whirling Disease

• Important characteristic can produce spore that
  is highly resistant (15 yrs dessication),
  associated with dispersal
• Life Cycle infective stage gets into fish upon
  contact with skin, produces amoebula known as
  trophozoite, site attacked is species specific,
  most visible stage is the spore, spore released
  to environment, consumed by oligochaete, grow and
  released to environment
• fish eats oligochaete or encounters free spores

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Salmonid Whirling Disease

• Usually found in salmonids, but not a contagious
  parasite
• Pathology development in cartilage, usually
  young fish, can have carriers showing no signs,
  fish exhibits whirling (tail chasing) when
  feeding or alarmed, whirling caused by
  destruction of inner ear by spores
• can cause blacktail by controlling production
  of chromatophores in spinal column, also pugnose,
  skeletal deformities

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Salmonid Whirling Disease

• Diagnosis remove gill arch, grind and allow to
  settle, check supernatant for spores
• other methods cook head/plankton centri- fuge,
  pepsin-trypsin digestion/centrifuge
• Fluorescent Antibody Test (FAT) w/rabbit
• Transmission direct during first year, indirect
  via annelid, contamination (cyst)
• Hosts trout, salmon, char, grayling

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Salmonid Whirling Disease

• How did it get here? Came from Europe via Danish
  frozen trout in the 50s
• Control non-treatable, avoidance critical, UV
  of incoming/recirc water, filtration to less than
  10 µM
• Accomodation incubate eggs and rear fry
  separately in UV water, check new ponds with
  sentinels

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Salmonid Whirling Disease
Various forms of spores
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Salmonid Whirling Disease
mature spores
sporoblast
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Salmonid Whirling Disease
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Phylum Platyhelminthes

• Class Turbellaria (turbellarians)
• Class Monogenea (flukes)
• Class Cestoidea (tapeworms)
• S.C. Cestodaria
• S.C. Eucestoda (true)
• Class Trematoda (flukes)

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(5) Cestodes tapeworms

• Tapeworms are members of the Phylum
  Platyhelminthes which includes the classes
  Turbellaria, Monogenea, Trematoda and Cestoidea
  (tapeworms)
• the tapeworms are unique in that they have no
  digestive tract and, thus, are parasitic of many
  invertebrates
• we are concerned with the Subclass Eucestoda, the
  true tapeworms

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Cestodes

• Occur in all classes of vertebrates and some
  inverts, common in wild fish, mainly unsightly
• all have three different body regions scolex
  (attachment), neck (buds off proglotids),
  strobila (remainder)
• proglottids formed by the asexual budding of neck
• all proglottids develop both male and female
  sexual organs

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Cestode Anatomy
scolex
proglottids
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Cestodes

• Gravid proglottids are usually full of eggs,
  gonads degenerated
• Egg release apolysis (release of whole
  proglottids) or anapolysis (eggs extruded through
  a common pore)
• Morphology no gut have nervous,
  osmoregulatory, reproductive systems for both
  males and females (male develops first)

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Tapeworm Life Cycle
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Diphyllobothrium latum

• Broad fish tapeworm of humans
• has three hosts copepod, fish, humans
• fish hosts pike, perch, turbot, lake trout, eel
• distribution depends on what we eat

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Life Cycle of Diphyllobothrium latum (a zoonosis,
transmitted to man)
Canids, Felids, bear, seals, etc.
Adults in Man
Chunks of proglottids shed in feces
Eats infected flesh, liver or roe
ZOONOSIS
Incubate 5d-weeks. Hatch and release coracidium
Fish
Copepod
Pike, perch, walley, turbot, lake trout, eel
Diaptomus, Cyclops
Eaten by fish
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Diphyllobothrium latum

• Effects on humans abdominal pain, blockage of
  gut, vit B12 deficiency
• Effects on fish visceral adhesion, sterility,
  decreased market value
• Control cook fish, proper freezing

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(6) Class Trematoda flukes

• Also members of Phylum Platyhelminthes
• Class Trematoda all parasitic, mainly in
  digestive system, found in all classes of
  vertebrates
• Subclass Digenea at least two hosts in life
  cycle, first host typically a mollusc
• Subclass Aspidogastrea only one host, usually a
  mollusc, mature in fish/turtles, intermediate
  host can be lobster
• Subclass Didymozoidea tissue dwelling parasites
  of fish, no complete cycle known

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Class Trematoda
Subclass Aspidogastrea
Subclass Digenea
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Digenetic Trematodes Morphology

• Attachment Organs most have oral sucker and
  ventral sucker (acetabulum)
• Digestive System mouth, prepharynx, pharynx,
  esophagus, intestinal cecae feeding is suctorial
• Reproductive System genital pore for both
  sexes male has testes, vas def female has
  ovary, oviduct, Mehlis gland ???, ootype (egg
  shell formation), uterus, vitellaria, vitelline
  ducts, vitelline reservoir copulation generally
  by cross-fertilization

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Trematode Morphology
Notice arrangement of suckers
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Life Cycle of Trematodes

• Adult parasite sexually reproducing stage of
  the parasite
• Definitive host host of adult parasite
• Intermediate hosts all hosts in life cycle
  other than the definitive host (usually numbered,
  starting with first after definitive host)
• adults live mainly in digestive tract, but also
  in blood, gall bladder, muscle, other organs
• eggs leave adult via feces, some ready to hatch
  after entering water, most need period of
  development
• in most cases eggs must be laid in water

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Life Cycle of Trematodes

• Larval stage hatching from egg is known as
  miracidium (ciliated, free-swimming), only goal
  is to find/penetrate intermediate host
• first host is usually a snail miracidia find
  intermediate host via photoreception,
  chemoreception, tangoreception, statoreception
  snail mucus is attractive
• Asexual Reproduction occurs in first
  intermediate host as either sporocysts
  (thin-walled germinal sac) or rediae (same, but
  with pharynx and gut) browse through tissues of
  snail

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Life Cycle of Trematodes

• Goal produce large numbers of cercaria, making
  up for losses in complex life cycle
• This is the difference between monogenetic and
  digenetic trematodes monogenetic one
  offspring digenetic produce cercaria many
  offspring
• Cercariae the second free-living larval stage,
  their fate depends on species
• penetrates or is ingested by definitive host and
  develops into adult (Sanouinicola)
• penetrates or is eaten by second intermediate
  host and encysts as metacercariae
• encysts on substrate and waits to be eaten by
  definitive host

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Life Cycle of Trematodes

• Metacercariae quiescent or resting stage,
  arrested development until definitive host eats
  secondary host, morphology varies with species
• after consumption, metacercariae excyst and
  develop into adults in relatively short period of
  time

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Life Cycle of Trematodes
egg
sporocysts
miracidium
metacercaria
rediae
cercaria
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Crepidostomum

• Adults in intestines of salmonids
• can be very frequent in certain areas however,
  death unusual
• eggs passed with feces of fish
• miracidia hatch and penetrate fingernail clams
• cercariae released and penetrate mayfly nymphs or
  amphipods
• salmonids infected when they eat the above

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Sanguinicola

• Lacking suckers, ceca are X or H-shaped, numerous
  testes
• adults live in cyprinids, salmonids, etc.
• found in bulbous arteriosus, ventral aorta, gill
  vessels, kidneys
• eggs released in bloodstream, hatch in gill
  capillaries, release miracidiae
• miracidiae penetrate Oxytrema snail, produce
  sporocysts

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Sanguinicola

• cercariae released from sporocysts, directly
  penetrate fish host (no metacercaria)
• build-up of eggs in gills may obstruct flow of
  blood, signs of oxygen distress result
• many eggs washed to kidney, can become
  encapsulated, impairs flow of blood to kidney

cercaria
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Sanguinicola
Build-up of eggs in gills