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Parasitology

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Title: Parasitology


1
Parasitology
2
What is a parasite?
  • Definition
  • An animal which lives in (endoparasite) or on
    (ectoparasite) another animal (the host).
  • Is almost always a different species from the
    host
  • Depends on the host for food an causes some
    degree of injury

3
General characteristics
  • Tremendous reproductive capabilities
  • Have physical adaptations that enhance attachment
    to the host (i.e. suckers, hooks or clamps)
  • Possess various mechanisms for avoiding the
    hosts immune response
  • Exhibit complex life cycles often with multiple
    hosts

4
Typical Indirect parasite life cycle
Primary Host Adult stage parasite infects host
Egg/Spore Stage Transmission and spread into the
environment
Infective larvae Able to infect primary host
Intermediate host Growth and developmental stage
(may not cause damage to the host)
5
Negative affects on the host
  • Direct damage to host
  • inducing tissue and organ damage
  • Indirect effects
  • Stress causes an increase susceptibility to
    secondary infections
  • Direct damage can act as a portal for secondary
    infection
  • Parasite may serve as a carrier/vector for
    another viral/bacterial pathogen

6
Signs of Parasitic infections
  • Fish at surface gulping or piping
  • Suggests parasites on gills
  • Fish rolling/flashing
  • suggests protozoan or worm infestation (internal
    or external)
  • Lethargy or listlessness
  • Suggests gill parasite
  • Fish at bottom
  • Suggests gill parasite, especially Ich
  • Fin erosion/Lesions
  • Indicative of external parasite
  • Flared gills
  • Indicative of gill parasite
  • Excess mucus, fish shimmies/quivers, or is off
    feed
  • General indication of disease

7
Major Groups of Fish Parasites
  • Protozoa single celled animals
  • Monogenetic Trematodes Flukes (flatworms) with
    haptor (posterior attachement organ) an have
    simple life cycle (no intermediate host)
  • Digenetic Trematodes Flukes (flatworms) with
    oral/ventral suckers and exhibit complex life
    cycles (involve intermediate hosts)

8
Major Groups of Fish Parasites
  • Cestodes (Tapeworms) worms with
    flattened/segmented bodies, head usually has
    suckers/hooks/suctional grooves
  • Nematodes (Roundworms) Thin elongated worms with
    cylindrical bodies covered by a rigid cuticle
  • Acanthocephala (Spiny-headed worms) bodies
    cylindical or fattened with anterior end bearing
    elaborate hooked proboscis

9
Major Groups of Fish Parasites
  • Copepods crustaceans (sea lice) that may appear
    louse, worm, or grub like
  • Leeches flattened or cylindrical, body segmented
    with anterior/posterior suckers
  • Glochidia larval freshwater clams
  • Fungi either as spores or as fungal hyphie

10
External Protozoa
  • Flagellates
  • Ichthyobodo (Costia)
  • Ciliates
  • Ichthyophthirius multifilis (Ich)
  • Trichodinids
  • Epistylis

11
External Protozoa
  • Common and usually occur in low numbers
  • Dense populations can cause serious epizootics
    (usually caused by some form of stress)
  • Symptoms include
  • -Irritation (flashing) -Erosion of scales
  • -Erythema (reddening) -Hemorrhaging
  • -Excess mucus production -white spots on skin
  • Control by chemical treatment

12
Internal Protozoa
  • Myxobolus cerebralis (whirling disease)
  • Ceratomyxa shasta
  • Henneguya

13
Myxobolus cerebralis
  • Infects cultured and wild salmonids
  • Specific tropism for cartilage
  • Infection can result in axial skeleton and neural
    damage

14
Ceratomyxa shasta
  • Myxosporea
  • Found in marine and freshwater environments
  • Only infects salmonids
  • Susceptibility varies
  • Clinical signs vary among infected salmonid
    species
  • Identified by spore size, shape, and location

15
Henneguya
  • Myxosporea
  • Ovoid, spherical, or lenticular spores
  • Usually cysts form around spores

16
General Myxosporidean lifecycles
  • landmark discovery by Wolf Markiw in 1984
  • a fish myxosporean alternates with an
    actinosporean from an oligochaete worm
  • both spore types represent alternate lifecycle
    stages of the one organism
  • morphologically distinct spores are genetically
    identical

17
General Diagnostic Procedure
  • Presumptive ID
  • Wet preparation
  • Histology
  • Site of infection
  • Spore morphology
  • Confirmation of ID
  • Molecular methods
  • Any level of infection, all stages, definitive

18
Trematodes
19
  • Monogenetic
  • Gyrodactylus sp.
  • Digenetic
  • Bolbophorus damnificus
  • is often referred to as the catfish trematode
  • Misnomer because there are about 30 trematodes
    found in the channel catfish and because it is
    also found in the fathead minnow

20
Digenetic Trematodes
  1. Adult flukes reside in fish, birds, or mammals
  2. Flukes lay eggs that pass through the definitive
    host, eggs hatch to a ciliated miracidia
  3. The miracidia will develop to a cercariae if in
    contact with a snail or mussel
  4. If the cercariae contacts invertabrate of fish
    hose it will encyst as a metacercaria

21
Cestodes
  1. GI tract of fish, bird or Mammal
  2. Eggs are laid to water and are eaten or hatch
    into a coracidium (C) and are then eaten by an
    invertabrate host
  3. Larval development to a proceroid or a
    pleroceroid occurs invertabrate
  4. Final host becomes infected by ingesting
    invertebrate

22
  • A. colex of Bothriocephalus acheilognathii from
    carp, Transvaal, South Africa (by courtesy of
    J.G. Van As).
  • B. B. acheilognathii, whole worm (living) from
    farmed carp, Israel.
  • C. Embryonated eggs of b.
  • D. Ligula sp. from Rastrineobola argenteus from
    L. Victoria. Infected fish are recognized by
    their inflated abdomen (top fish) and may
    accommodate even three worms (bottom group).

23
Nematodes
C. philippinensis egg
C. philippinensis adult
24
  • Unembryonated eggs are passed in the stool (1)
    and become embryonated in the environment (2)
    after ingestion by freshwater fish, larvae hatch,
    penetrate the intestine, and migrate to the
    tissues (3).  Ingestion of raw or undercooked
    fish results in infection (4).  The adults reside
    in the human small intestine mucosa (5).  The
    females deposit unembryonated eggs (can become
    embryonated) (6).  Also infects fish eating birds
    (7).

Capillaria philippinensis
25
Acanthocephala
  • A) GI tract of Fish, Acanthor larva released
  • B) Eaten by invertabrates and produces a
    cystacanth (C)
  • If eaten by suitable host, the cystacanth will
    develop into an adult

26
Neoechinorhynchus rutili
Adult female
Adult male
27
Leeches (Hirudinea)
Leech with brood attached
Top view
28
Leech Characteristics
  • Primarily occur in freshwater
  • Most are predators or scavengers which feed on
    fluids or soft tissues of live or dead
    invertebrates
  • Generally have 34 body segments and an anterior
    and posterior sucker
  • Parasitic leeches attach temporarily
  • Cause little noticeable harm

29
Hirudinea Problems
  • Hemorrhaging
  • Inflammation
  • Edema
  • Ulceration
  • Fibrosis
  • Hyperplasia
  • Necrosis
  • Irritation
  • Weight loss
  • Some can be vectors of other parasistes

30
Copepods
Lernaea sp.
Salmonicola sp.
31
Copepods are a subclass of Crustaceans
  • Sexes are usually separate with sexual
    dimorphism present
  • Heavy infections can cause severe damage to skin,
    muscle, and gill tissues
  • Can also lead to secondary infections, anemia,
    emaciation, and mortality

32
Copepoda
  • Mature copepods release eggs (B) that hatch to
    larvae (C)
  • D) After molting a copepod stage is formed and
    may attach to a host (E)

33
Glochidia
  • Larvae attach to gills or skin
  • Live as parasites then drop off and live
    independently
  • Some modify mantle tissue to help find host

34
Glochidia
Lampsilis reeveiana
Glochidia attaching to gill tissue
35
Fungi
  • Saprolegnia water molds
  • Worldwide in freshwater
  • Appear as whitish cottony-like growths
  • Considered secondary invaders
  • Can attach to eggs and fish
  • Can be controlled with chemicals

36
Aphanomyces invadans
Hyphae
Germination
Sporangia
Cyst
Sporulation
1 Zoospore
2 Zoospore
1º cyst
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