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Protozoan Parasites:
Flagellates, Amoebae, Ciliates & Apicomplexans
Spencer Greenwood
BSc, MSc, PhD, DVM
Dept. of Biomedical Sciences
Office: 2332N AVC-North Annex
Phone: 566-6002
Home: 892-4686
E-mail: [email protected]
http://people.upei.ca/sgreenwood/index.htm
Protozoa or Protists
• Single-celled eukaryotes
• Heterogeneous group
• Reproduction - asexual but some
have sexual stages
• Locomotion - flagella, cilia,
pseudopods or gliding
• Life style - free living & parasitic
forms
Parasitic Protozoa
• All vertebrates & invertebrates
are infected by protozoa
• Life cycles:
– simple & complex
• Transmission:
– Direct
– intermediate or paratenic hosts
– resistant stages (cysts)
Parasitic Protozoa
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Taxonomy - major groups
Flagellates
Amoebae
Ciliates
Apicomplexa
Microsporida/Myxozoa
Parasitic Protozoa
Eimeria
Giardia
Isospora
Cryptosporidium
Toxoplasma
The Father of Protozoology
Giardiasis
• Zoonotic species - “Beaver Fever”
• Giardia duodenalis = intestinalis = lamblia
– mammals - dogs, cats, cattle, sheep & humans...wildlife
– Not all assemblages are zoonotic...
• Host Adapted species
• G. muris
– rodents
• G. microti
– muskrats & voles
• G. ardeae & G. psittaci
– birds
• G. agilis
– amphibians
Giardia morphology - 2 life stages
Axostyle
Cyst
Trophozoite
The cyst is
immediately
infectious
Giardia - Site of infection
http://www.stanford.edu/class/humbio103/ParaSites2003/G
iardia/GIARDIA2_files/image006.jpg
http://www.snow.edu/~kevins/giardia.jpg
http://www.deltagen.com/target/histologyatlas/atlas_files/digestive/duodenum_20x.jpg
http://www.cdfound.to.it/i mg/giardia-04-250x.jpg
http://www.cdfound.to.it/img/giardia-08-1000x.jpg
Giardia Life cycle – simple & direct
• Fecal-oral
• Waterborne
• Cysts highly resistant
– 106 / gram of feces
• Cyst = infective stage
• Trophozoite = non-infectious
• Prepatent period
– 7-10 days
Transmission
Transmission
Prevalence
• Worldwide - found everywhere
• Most common in young animals
– Barnyards, kennels, catteries, shelters, puppy mills,
daycares...
– Stress
– crowded, confinement
– poor hygiene/sanitation
• Dogs:
– > 1 year = 4%
– < 1 year = 36%
• Kittens 11%
• Livestock up to 100%
– in calves > 30 days
• Pet birds up to 60%
Pathogenesis
• Variable
– Severity dependent on
dose of infection...
• Diffuse shortening of
microvilli
• Villus atrophy
• Malabsorption
• Increase G.I. motility
Clinical Signs
• Gastro-intestinal signs:
• Most asymptomatic
• Acute to chronic small bowel diarrhea
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Signs last ~ 1-2 weeks to months
Watery explosive,
Steatorrhea, pale
foul smelling
• Abdominal discomfort -> pain
• Vomiting & anorexia
http://www.petservice.com/libraries/pictures/coron_pict.html
Clinical Signs
• Extra-intestinal signs
– Allergic response urticaria, pruritus in dogs &
humans
– Feather picking in birds
ww w.geo citie s.com/.../ Bluffs/1 958 /pluck.h tml
http://education.vetmed.vt.edu/Curriculum/
VM9144/PRURITUS/pruritus.htm
Diagnosis
• Gold Standard:
• Centrifugal Fecal Flotation
– Zinc sulphate or sucrose
– with or without Lugol’s iodine stain
– Scan microscope slide at 10X but
confirm Dx by observation at 40X
– “Osmotic artifact”- causes
trophozoites in cysts to collapse
• Often has a refractile edge which makes
it easier to see
– cysts
• Intermittent shedding
• Perform 3 fecal exams in 7days
Osmotic
artifact
Refractile
edge
Diagnosis
• Direct Fecal Smear
– Fresh feces
– Saline smear
• Trophozoites
• “falling leaf” movement
• May also see cysts
Diagnosis
• Antigen Detection
– Fecal ELISA
– IDEXX SNAP®
• Giardia
– Based on cyst
wall protein
• No test 100%
• Use combination
– flotation & antigen
to increase
accuracy
Treatment & Control
• No licensed products
– Fenbendazole, metronidazole “extra-label”
– Azithromycin?
– Resistance is an emerging issue?
• Vaccination - Giardia Vax®
Treatment & Control
• Good hygiene
– Cysts stick to fur...
therefore remember to
bathe infected pets
(daily?)...
– Disinfect fouled
areas...long contact times
• Proper sanitation
• Reduce Stress
Poop & Scoop Barbie
Giardia in the news
Hexamitosis
• Hexamita meleagridis
– Turkeys & game birds
• Hexamita columbae
– Pigeons
Morphology - Hexamita
• Trophozoite
– oval shaped, bilaterally
symmetrical with 8
flagella
– binucleate with
prominent nucleolus
– 6 -12 um long
• Cysts
– “rarely formed”
Wood & Smith 2005, Avian Diseases
Life cycle
• Direct transmission
– fecal-oral, contamination of
feeders & waterers
– Trophozoite is infectious stage
• Trophs colonize small intestine
• Young birds most susceptible
– 1 - 9 weeks
• Asymptomatic carriers (adults)
• “A problem in every commercial turkey producing area”
• Heavy losses reported in
outbreaks of farmed ringnecked pheasants
Pathogenesis & Clinical signs
• Catarrhal enteritis & atony
– Swollen, bulbous, liquid filled small intestine
• Diarrhea
– Greenish-yellow watery & foamy
• Listless, inappetence, anorexia, dehydration
– convulsions & coma
• Survivors - stunted
Diagnosis
• History
– Mixing of young birds with
asymptomatic carriers
• Clinical signs
• PM - scrapings from
duodenum
– Trophs – fluid
– Cysts - mucus/squash prep
– Stain both with Hemacolor®
• Beware confounding
flagellates in cecum
Control & Treatment
• Segregation
– Remove carriers, separate adults /
poults
– All-in / All-out strategy
• Sanitation
– Remove litter with fecal matter
– Disinfect building, feeders & waterers
• Biosecurity
• Antibiotics for secondary infections?
– Food animals: chlortetracycline,
tetracyclines & oxytetracyline
– Pet birds: metronidazole & ronidazole
VPM-122 Midterm Exam # 3
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Thursday, March 25, 2015
Lecture 286ABC/287N
0930-1020H
Covers my lectures (#16-21)
Protozoan Parasites lecture notes pages, 1-57.
Format
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Multiple choice, short answer & essay
Point form is okay for answers...including the essay!!!!!
Say no to drugs & no drug names on exam either!
No prevalence numbers
Trichomonosis