Title: Parasitology
1Parasitology
2What 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
3General 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
4Typical 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)
5Negative 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
6Signs 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
7Major 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)
8Major 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
9Major 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
10External Protozoa
- Flagellates
- Ichthyobodo (Costia)
- Ciliates
- Ichthyophthirius multifilis (Ich)
- Trichodinids
- Epistylis
11External 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
12Internal Protozoa
- Myxobolus cerebralis (whirling disease)
- Ceratomyxa shasta
- Henneguya
13Myxobolus cerebralis
- Infects cultured and wild salmonids
- Specific tropism for cartilage
- Infection can result in axial skeleton and neural
damage
14Ceratomyxa 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
15Henneguya
- Myxosporea
- Ovoid, spherical, or lenticular spores
- Usually cysts form around spores
16General 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
17General Diagnostic Procedure
- Presumptive ID
- Wet preparation
- Histology
- Site of infection
- Spore morphology
- Confirmation of ID
- Molecular methods
- Any level of infection, all stages, definitive
18Trematodes
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
20Digenetic Trematodes
- Adult flukes reside in fish, birds, or mammals
- Flukes lay eggs that pass through the definitive
host, eggs hatch to a ciliated miracidia - The miracidia will develop to a cercariae if in
contact with a snail or mussel - If the cercariae contacts invertabrate of fish
hose it will encyst as a metacercaria
21Cestodes
- GI tract of fish, bird or Mammal
- Eggs are laid to water and are eaten or hatch
into a coracidium (C) and are then eaten by an
invertabrate host - Larval development to a proceroid or a
pleroceroid occurs invertabrate - 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).
23Nematodes
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
25Acanthocephala
- 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
26Neoechinorhynchus rutili
Adult female
Adult male
27Leeches (Hirudinea)
Leech with brood attached
Top view
28Leech 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
29Hirudinea Problems
- Hemorrhaging
- Inflammation
- Edema
- Ulceration
- Fibrosis
- Hyperplasia
- Necrosis
- Irritation
- Weight loss
- Some can be vectors of other parasistes
30Copepods
Lernaea sp.
Salmonicola sp.
31Copepods 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
32Copepoda
- 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)
33Glochidia
- Larvae attach to gills or skin
- Live as parasites then drop off and live
independently - Some modify mantle tissue to help find host
34Glochidia
Lampsilis reeveiana
Glochidia attaching to gill tissue
35Fungi
- 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
36Aphanomyces invadans
Hyphae
Germination
Sporangia
Cyst
Sporulation
1 Zoospore
2 Zoospore
1º cyst