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Parasitology 1 > 6.6 Protists 3 > Flashcards

6.6 Protists 3 Flashcards

1
Q

Haemospororid Parasites

A

-Leucocytozoon spp.
-Haemoproteus spp.

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2
Q

Leucocytozoon spp.; host, site of infection, transmission

A
  • found within erythrocytes wild or domestic birds
  • locally, domestic ducks highly susceptible
  • wild species (esp. Black ducks) are resistant
  • transmitted by simuliid flies (blackflies)
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3
Q

Leucocytozoon spp. transmission, effects

A
  • transmitted by simuliid flies (blackflies)
  • transmitted in the spring to ducklings shortly after hatch
  • may get high mortality
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4
Q

Haemoproteus spp.; host, site of infection, stages of life that cause pathogenicity

A
  • found within erythrocytes of wild and domestic birds
  • gamonts cause no pathological changes
  • asexual stages within endothelium appear to be the primary cause of pathogenicity
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5
Q

Haemoproteus spp. transmission, when they are a problem

A
  • usually transmitted by midges (no-see-ums) or hippoboscid flies
  • often seen as a problem in captive wild birds (especially raptors)
  • merogonic development may be activated by stress/brooding
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6
Q

Flagellates; General Characteristics; hosts, site of infection, type of life cycles

A
  • Found in any animal, host-specific or not
  • Some infect mucosal sites
  • Mucosal parasites generally form cysts and have direct life cycles
  • Some infect blood
  • Blood borne parasites generally use vectors and have complex, multi-host life cycles
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7
Q

Flagellates; Major Groups

A
  • Diplomonads (Giardia, Hexamita)
  • Trichomonads (Trichomonas)
  • Amoeboflagellates (Histomonas, Dientamoeba)
  • Kinetoplastids (Trypanosoma, Leishmania)
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8
Q

Giardia spp.; Site of Infection

A

Duodenum and upper small intestine

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9
Q

Giardia spp.; Morphology

A

Pyriform trophozoite with:
> 8 flagella
> 2 nuclei
> prominent ventral disc
(highly characteristic “face-like” appearance)

Cyst is a rounded up trophozoite:
> about 9 to 12 um
> containing 4 nuclei when mature

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10
Q

Giardia spp.; Life Cycle

A
  • like most mucosal flagellates, Giardia spp. have a simple, direct (monoxenous) life cycle involving the formation of cysts
  • fecal-oral contamination with encysted forms is main route of infection
  • cysts excyst in new host to form 2 trophozoites to initiate new infection

cysts passed in feces
>ingested by difinitive host
>excystation
>trophs attach to epithelial cells of intestine
>reproduce by binary fission
>trophozoite in intestine
>encystation…

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11
Q

Giardia spp.; Pathogenesis

A
  • known to cause diarrhea in a variety of hosts
  • cross-transmission between hosts is still controversial
    (strains are better adapted to particular hosts but can infect other hosts – c.f. Cryptosporidium)
  • blanket epithelium of duodenum and upper small intestine causing a malabsorptive enteritis with diarrhea
  • fat absorption affected > fatty diarrhea
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12
Q

Giardia spp.; Clinical Signs

A
  • foul smelling, fatty diarrhea
  • blood may be found in feces, especially with the chinchilla
  • lesions at site of infection consist of acute focal inflammation, increased mucus
  • may migrate to bile duct causing clinical signs
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13
Q

Giardia spp.; Diagnosis

A
  • small oval cysts can be found on standard fecal flotations using ZnS04 (NOTE: sodium nitrate collapses cysts)
  • smears can be stained using IFA for specific diagnosis–usually in human diagnostic labs only
  • trophozoites may be seen in very watery diarrhea if kept warm and examined in saline directly - floats will kill trophozoites
  • solid substrate ELISA tests now available for fecal antigen shed by Giardia spp. (e.g. ProSpecT® Giardia Rapid Assay - ~$25/test)
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14
Q

Giardia spp.; Treatment

A
  • metronidazole (Flagyl) off-label
    (50 mg/kg daily for 5 consecutive days)
  • fenbendazole (off-label) – efficacy?
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15
Q

Giardia spp.; Prevention

A
  • a vaccine was marketed that is designed to reduce cyst shedding and severity of clinical disease in dogs – limited effectiveness – no longer on market
  • Chemically-killed cultured trophozoites
  • given annually
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16
Q

Trichomonas spp.; General - Order Trichomonadida; hosts, site of infection, transmission

A
  • most animals infected, including humans
  • usually in GI tract but also in urogenital organs
  • found in crop and intestines of birds
  • no cysts formed - direct transmission
17
Q

Trichomonas spp.; Morphology

A
  • single nucleus
  • 3 to 5 flagella with one flagellum attached to body by an undulating membrane
18
Q

Trichomonas spp.; Life Cycle

A
  • divide by simple binary fission
  • direct transmission of trophozoites
19
Q

Trichomonas spp.; Pathogenesis in various species

A
  • Cattle - a venereal disease
    > cows suffer vaginitis, early abortions
    > bulls remain infected for life if not treated
  • Pigs - non-pathogenic
  • Horses - infects cecum and colon
  • Birds - many susceptible to severe infections of the crop and esophagus
20
Q

Trichomonas spp.; Diagnosis

A
  • direct smears looking for trophozoites
  • culture of swabs for 3 to 7 days
21
Q

Trichomonas spp.; Birds - Pathogenesis

A
  • oral trichomoniasis most common
  • pigeons highly susceptible because they feed their young using “crop milk” – exfoliated crop epithelial cells (and parasites)
  • oral cankers or plagues that may resemble “thrush” (oral candidiasis, a fungal infection)
22
Q

Histomonas meleagridis; Life Cycle

A
  • divides by binary fission, non sexual cycle
  • direct fecal-oral transmission rare - NO cyst
  • transmitted within Heterakis sp. (cecal nematode) eggs
  • trophozoites eaten by worms and penetrate nematode’s digestive tract
  • invades ovaries and uterus of nematodes
  • multiplies within eggs of nematodes and in the developing larvae
    +
  • use Heterakis as paratenic host
  • released when larval nematode ingested
  • establish and divide in cecae
  • invasive trophs penetrate mucosa
  • trophozoites enter blood
  • trophozoites migrate to liver
  • multiply rapidly
  • pathogenicity and invasion is host-specific – turkeys highly susceptible
23
Q

Histomonas meleagridis; Pathogenesis/Lesions/Clinical Signs (Turkeys)

A
  • turkeys severely affected, especially poults
  • cecal lesions common with edematous mucosa
  • liver lesions (up to 1 cm), yellow-green necrosis
  • numerous parasites in both ceca and liver
  • clinically, droopiness/ruffled feathers/hanging wings
  • head sometimes darkens - “Blackhead Disease”
  • yellowish diarrhea is characteristic
24
Q

Histomonas meleagridis; Treatment:

A
  • metronidazole (off label) - “Flagyl” (not in food production animals)
  • control is generally preventative > management
  • remove soil contact (what operations susceptible?)
  • anthelmintics to eliminate the intermediate helminth host
25
Q

Phylum Ciliophora
“The Ciliates”; Physical characteristics, relation to other parasites, habitat, reproductive strategy

A
  • possess cilia, usually arranged in rows
  • related to apicomplexan parasites and dinoflagellates (all are alveolates)
  • free-living with some parasitic species
  • divide asexually by binary fission but also have genetic exchange via
    conjugation some form resistant cysts
26
Q

Balantidium coli; Morphology, location, replication strategy

A
  • large ciliated protist that lives principally within the large bowel as a trophozoite
    (arrow marks the cytostome = “mouth”)
    • cyst form with obvious curved, dense nucleus and
      dense cyst wall; found in formed stool
  • replication is by binary fission
27
Q

Balantidium coli; Life Cycle, hosts

A
  • usual (and “reservoir”) hosts are swine (wild and domestic)
  • infection via ingestion of cysts shed by pig or human
  • zoonotic risk
28
Q

Balantidium coli; Clinical Signs /Treatment

A
  • persistent diarrhea, occasionally dysentery, abdominal pain, and weight loss
  • responds to tetracyclines
29
Q

Ichthyophthirius multifiliis; Morphology

A
  • common parasite of fish in aquaria usually seen as white raised spots in/on skin of fish up to 1 mm in diameter
  • ciliate is found within cyst in skin
30
Q

Ichthyophthirius multifiliis; Life Cycle

A
  • both parasitic and free-living forms are found in the aquarium
  • tomites are the infective forms and actively seek out a host

> tomont released by fish, encysys
multiple cell divisions on substrate
cyst opens, tomites released
skin penetration
trophonts grow within epithelium

31
Q

Microspora; Taxonomy

A

Kingdom Protoctista (Protozoa)
Phylum Microspora
Order Microsporidia

32
Q

Microsporidia; Site of Infection

A
  • usually digestive tract but can also be elsewhere on a mucous membrane
33
Q

Microsporidia; Morphology

A
  • single-celled spore with characteristic coiled filament
  • other forms (e.g. sporoplasm) less easily determined to be a microsporidium
34
Q

Microsporidia; how does it invade cells?

A

active penetration of host cells

35
Q

Microsporidia; Life Cycle

A
  • polar filament explosively penetrates host cells
  • asexual mitotic divisions give rise to sporoplasm that then divides into spores that mature

Parasitology 1 (8 decks)

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