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Transcript
Protozoal Diseases of Wildlife
• Eukaryotes
• Unicellular
• Multiple stages
trophozoite
cyst
• Complex life cycles
• reproduce asexually
• some also have a sexual reproductive stage
Phyla Important for Infectious Disease
1. Amoebozoa (amoebae)
4. Euglenozoa (flagellates)
2.
Ciliophora (ciliates)
5. Microspora
3.
Archaezoa (flagellates)
6. Apicomplexa (sporozoa)
Major differences in modes of locomotion
amoebae – pseudopodia
http://video.google.com/videosearch?q=amoeba%20mo
vement&hl=en&source=vgc&um=1&ie=UTF8&sa=N&tab=wv#
ciliates – cilia
http://video.google.com/videose
arch?q=paramecium+darkfield&
emb=0&aq=f#
flagellates – flagella
http://video.google.com/videosearch?q=flag
ellates+dancing&emb=0&aq=f#
microspora and sporozoa – intracellular
Amoeba
• The typical life cycle
involves infection of the host
with the trophozoite,
multiplication, and in some
cases, producing cysts.
Ingestion in
contaminated
food or water
Ciliates
2 examples
• Balantidium coli - a
common intestinal parasite
of man, lower primates,
and hogs.
• Ichthyophthirus multifillis agent of "ich“ - a parasite
infecting fish.
Flagellates
• Two groups
1. within Archaezoa (intestinal & urogenital)
2. within Euglenozoa (blood)
Flagellates – intestinal and urogenital
• Trichomonas spp
– agent of trichomoniasis in a
variety of animals
– transmitted sexually
• Giardia lamblia
– infects a variety of
domestic and wild animals
– the most common intestinal
parasite of people in North
America.
– transmitted fecal-oral
Flagellates - haemoflagellates
• live in blood, lymph, and tissue spaces
• transmitted from host-host by blood-feeding arthropods
• most important genera: Trypanosoma and Leishmania.
Apicomplexa
•
•
•
•
•
all members are parasitic
obligate intracellular
non motile
all have complex life cycles
The common feature of all
members is the presence of an
apical complex in one or more
stages of the life cycle.
– Acts like a drill bit, and secretes
enzymes that allow the parasite
to enter other cells
Toxoplasma invading host cell
Toxoplasma gondii
• infects humans and other
warm-blooded animals,
including birds
• found worldwide
Toxoplasma gondii
• Only felids are
definitive host - both
wild and domestic cats
serve as the main
reservoir of infection.
Definitive
host
Toxoplasma gondii
3 infectious stages of T. gondii
• tachyzoites (trophozoite)
• bradyzoites (within tissue cysts)
• sporozoites (within oocysts)
Toxoplasma gondii
• transmitted by
– consumption of sporocysts in
cat feces
– consumption of bradyzoites
within tissue cysts
– transplacental transfer of
tachyzoites from mother to fetus
Toxoplasmosis in felids
•
•
•
Mouse – infected by ingesting an oocyst
Oocysts transform into tachyzoites
shortly after ingestion. These
tachyzoites localize in neural and
muscle tissue and develop into tissue
cyst bradyzoites.
Once parasite is in tissue cyst stage it
stimulates the mouse immune system
so that only parasites within tissue cysts
will survive, in this way the infection will
not kill the mouse before the mouse gets
eaten.
Toxoplasmosis in felids
•
•
Mice lose their fear of cat smell, and
actually seek out cats.
Mouse containing tissue cysts with
bradyzoites is ingested by feline
Toxoplasmosis in felids
•
•
Bradyzoites are released from tissue cysts
during digestion, invade cat’s intestinal
epithelium, and undergo sexual replication,
passing through a tachyzoite stage,
culminating in the release of oocysts in cat
feces.
Cats generally mount a powerful immune
response to the parasite and develop
immunity after the initial infection, and
therefore shed oocysts only once in their
lifetime.
Toxoplasmosis in other animals
•
Toxoplasmosis is one of the most commonly
diagnosed causes of abortion in sheep and
goats
Toxoplasmosis in other animals
•
Recent research has shown that T. gondii is
one of the primary killers of sea otters.
•
Toxoplasmosis is a fatal disease in the
eastern bandicoot
Toxoplasmosis in other animals
•
and wombats
•
and wallaby, which can transmit to humans
Toxoplasmosis in humans
Toxoplasmosis in humans
•
Parasites form tissue cysts, most commonly in skeletal muscle, myocardium,
brain, and eyes; these cysts may remain throughout the life of the host.
hydrocephalus
Toxoplasmosis
• Domestic and wild
cats = definitive
host
• British Columbia =
cougars
Toxoplasmosis
• Intermediate hosts
–
–
–
–
–
–
–
–
–
–
Moose
Pronghorn
Mule deer
WTD
Black bear
Red fox
Skunks
Opossum
Mink
Small mammals
Neosporosis
• Neospora caninum
• Structurally/biologically
similar to Toxoplasma;
1988
• Definitive hosts =
canids (1998)
• Intermediate hosts =
livestock
• Dogs deposit feces
into pastures or food
stuffs or water
Neospora caninum
• Structurally/biologically
similar to Toxoplasma;
1988
Tissue cyst with bradyzoites (thicker wall)
Neosporosis
• Forms cysts in the tissue
and remains dormant as
bradyzoites. Dogs that
eat infected meat from
deceased cattle will
ingest the bradyzoites
and become infected,
thereby shed more
Neospora caninum
oocysts.
Neosporosis
• fetal abortions,
stillbirth, low milk
yield, reduced weight
gain, weakened
condition, premature
culling in cattle
• economic loss to
farmers
Neosporosis
•
•
•
•
•
•
•
Woodbine et al. (2008) BMC
Veterinary Research. 4:1471-8219
England: seroepidemiological study of
N. caninum antibodies from 114 herds
visited on 3 occasions, annually
94% of herds: at least 1 seropositive
cow; 12.9% of adult cattle had at least
1 seropositive test
90% of herds: seropositive at all visits
median seroprevalence in + herds was
10% (range 0.4% to 59%)
positive association between the
serostatus of offspring and dams that
were seropositive
Between-herd movements of infected
cattle enhance spread, particularly into
low seroprevalence herds
Neosporosis
• >40% of white-tailed deer
sampled from Illinois
exhibited antibodies to
Neospora caninum
• Seroprevalence in WI
wildlife species:
–
–
–
–
19.0% WTD
14.7% coyotes
11.1% foxes
0% raccoons & opossums
Neosporosis
• Transmission from
deer & cattle to dogs
& coyotes –
demonstrated
• Incidence of
Neospora higher
where high cattle
densities and high
numbers of wild
canids
* Potential for crossover
Neosporosis