Transcript Life cycle of fish parasite Parvicapsula minibicornis Christopher Zielinski, Stephen Atkinson, Dr. Sascha Hallett, & Dr.

Life cycle of fish parasite
Parvicapsula minibicornis
Christopher Zielinski, Stephen Atkinson,
Dr. Sascha Hallett, & Dr. Jerri
Bartholomew
Center for Fish Disease Research
Department of Microbiology
Oregon State University
Parvicapsula minibicornis is a myxozoan
What are Myxozoans?
-Mostly fish parasites
-Multicellular organisms
-Over 1350 described species
-Infection of commercially important
species is of most concern
Salmon
Myxozoans have two life stages
Myxospore stage
Develops in fish
Myxobolus cerebralis
Actinospore stage
Develops in Aquatic
worms
Myxobolus cerebralis
Myxospore morphology
Spore valve
Polar filament
Sporoplasm
Polar Capsule
Actinospore morphology
Valves
Sporoplasm
Polar capsules
Generalized Myxozoan life cycle
P. minibicornis uncompleted lifecycle
?
Actinospore
?
Aquatic invertebrate
Myxospore
Lifecycles
Described species
27 Known freshwater life cycles
1 Known saltwater life cycles
Of the 1350 myxosporean species (fish stage) described:
 28 myxozoan life cycles are known
 26 are freshwater and involve an oligochaete worm
 1 is freshwater and involves a polychaete worm
 1 marine life cycle involves a polychaete worm
Parvicapsula minibicornis:
 First described from
sockeye salmon from
British Columbia
(Kent et al. 1997)
 Infect kidney or
urinary bladder
Myxospores
Clinical signs of infection
- swollen kidney
- anemia
Parvicapsula minibicornis in the
Klamath River
 Detected in juvenile
Chinook in Klamath
River since 1992
 Prevalence 80 -
100% during May July 2005
Parvicapsula minibicornis unknowns
What is the parasite life cycle?
Is kidney damage likely to impact juvenile
Chinook salmon survival?
Where are sites of parasite transmission?
Search for Parvicapsula
minibicornis invertebrate host
• Samples of sediment
•
and periphyton were
collected from the
Klamath River
Oligochaetes and
polychaetes were
sorted and examined
for actinospores
Developing actinospore stages seen
in polychaetes
Early actinospore
stages
(multinucleated
cells)
Developing actinospores
Mature actinospores
Released mature
actinospores
Polychaetes infected with
thousands of mature
actinospores
Actinospore characteristics
- nearly spherical
- 3 polar capsules
- 4-5 microns
Molecular evidence for life cycle
P. minibicornis-specific primers
(St. Hilaire et al. 2002)
amplified DNA from:
Actinospore from
Klamath River
polychaete
Myxospore from
Fraser River adult
sockeye salmon
Myxospore from
Klamath River
Chinook salmon
negative control
Molecular evidence….
• The 18S rDNA sequence of
the mature actinospore from
the Klamath River polychaete
was compared with the
published sequence of P.
minibicornis from the Fraser
River adult sockeye salmon
– 1710 bases sequenced
– 6 bp difference
– 99% similarity
Infection experiment
• 10 juvenile Chinook salmon
were exposed in the laboratory
to actinospores from infected
polychaetes.
– Dosage of 1000 actinospores per
fish in static water for 24 hours
• Tissue was assayed by QPCR.
• Kidneys from 3 out of 10 fish
were positive for P. minibicornis
Prevalence of P. minibicornis in Polychaetes
• Collected polychaetes from one location
• Pooled in groups of 5, 10, and 1 worm each
• Assayed worms by PCR
• Prevalence of infection is 1.8%
• Polychaete densities at collection location are 60,000100,000/mˆ2
• With a prevalence of 1.8%, 100,000 polychaetes could
produce millions of actinospores
Lifecycle of Parvicapsula minibicornis
?
Actinospore
?
myxospore
polychaete
Special Thanks To: Howard Hughes Medical
Institute for their support. Also thank you
to Dr. Sascha Hallett, Stephen Atkinson, Dr.
Kevin Ahern and Dr Jerri Bartholomew for
their guidance.