Module 4 : Protozoa

what are protozoa?

single-celled, eukaryotic microorganisms belonging to the animal kingdom "protista"

what are the two primary locations where protozoa may be found in a host?

feces (intestinal protozoa), blood (hemoprotozoa)

how are intestinal protozoa classified?

by their type of movement within the host

what are the three primary methods of movement used by intestinal protozoa?

pseudopodia, flagella, gliding movement

describe trophozoites

the motile stage in the protozoan life cycle that is capable of feeding & movement

why are trophozoites difficult to recognize in fecal floatation solutions?

because they lack rigid cell walls, they collapse when exposed to fecal flotation solutions

what is the recommended testing method for observing live trophozoites in feces?

a thin direct fecal smear performed using saline

describe cysts

the dormant stage in the protozoan life cycle that is incapable of movement

what can be used to stain or preserve protozoan cysts?

Lugol's iodine

in what types of specimens are cysts typically observed?

stained specimens from tissues or feces

describe the durability of cysts in the feces

they have a protective wall that enables the parasite to survive in the outside environment for a period of time ranging from days to a year

how are hemoprotozoa identified?

on stained blood smears using 100X (oil immersion)

blood parasites seen between RBCs are called…

extracellular blood parasites

blood parasites seen within or on RBCs are called…

intracellular blood parasites

what is the standard procedure for blood donors prior to transfusion?

screening for infectious diseases

what disease is caused by Entamoeba histolytica?

amoebic dysentery

which hosts are primarily affected by Entamoeba histolytica?

humans & non-human primates

what is the pathogenesis of Entamoeba histolytica infection?

colitis & liver abscesses

where is Entamoeba histolytica most common?

countries with poor sanitary conditions

how is Entamoeba histolytica transmitted?

fecal-oral contact; contaminated food & water sources

what testing methods are used to identify Entamoeba histolytica?

direct fecal smear or fecal float (on 40x)

what form(s) are Entamoeba histolytica identified in?

trophozoite or cyst forms

Trichomonas spp. belong to a group of ___________ protozoans

primitive

how do Trichomonas spp. trophozoites move?

flagella & undulating membranes

T/F: Trichomonas spp. have a trophozoite & a cyst form

false - no cyst form

where do Trichomonas spp. live?

warm, moist, anaerobic environments such as: the oral cavity, the GI tract, and the genital tract

how are Trichomonas spp. transmitted?

directly from host to host

how are Trichomonas spp. identified?

direct fecal using saline, view on 40x; look for movement pattern - jerky, spinning motion

T/F: all Trichomonas spp. are pathogenic

false

what is Tritrichomonas foetus in cattle?

a venereally transmitted parasite of the reproductive tract

what reproductive complications can Tritrichomonas foetus cause in cattle?

abortion & infertility

how is Tritrichomonas foetus treated in cows?

it is self-limiting; sexual rest for 3 months is the only treatment necessary to eliminate the parasite from the female

how is Tritrichomonas foetus treated in bulls?

bulls are permanently infected; slaughter is used to prevent the spread of infection

what practice has largely eradicated Tritrichomonas foetus in cattle?

artificial insemination (AI) using uninfected bulls

what is the pathogenesis of Tritrichomonas foetus in domestic cats?

colitis

how do cats affected with Tritrichonomas foetus present?

with chronic, intermittent large-bowel diarrhea (may contain blood or mucus) that is copious & foul-smelling

where is there a high prevalence of Tritrichomonas foetus in cats?

animal shelters, catteries, pet shops, other multi-cat environments

what is the primary route of transmission for Tritrichomonas foetus in cats?

fecal-oral route

what behaviors increase the risk of Tritrichomonas foetus transmission in cats?

sharing litter boxes and / or grooming themselves

what diagnostic methods are used to identify Tritrichomonas foetus in cats?

observation of live organisms in a direct fecal (using saline), fecal culture, or PCR testing

what is the typical prognosis for a Tritrichomonas foetus infection in cats?

the infection will resolve spontaneously (can take months to years)

do all cats infected with Tritrichomonas foetus show clinical signs?

no, some cats may serve as asymptomatic carriers

a protozoan that affects the oral cavity of pigeons, doves, poultry, and birds of prey

Trichomonas gallinae

which bird species are typically affected by Trichomonas gallinae?

pigeons, doves, poultry, birds of prey

what is the common name used by falconers for the disease caused by Trichomonas gallinae?

frounce

describe frounce

cheesy, necrotic lesions (“canker”) in the mouth, esophagus, and crops of pigeon swabs

what is the fatality rate of frounce?

80-90%

the most common flagellated intestinal protozoan infecting mammals (including people) & birds

Giardia spp.

what clinical sign does Giardia spp. typically cause in the host?

chronic diarrhea

what is the life cycle of Giardia spp?

direct

how is Giardia spp. transmitted?

fecal-oral route by ingesting infective cysts in contaminated food, water, fomites, or through self-grooming

what happens once the Giardia spp. cysts are ingested?

the open (excyst) & the trophozoites attach to the intestinal mucosa

describe giardiasis

the trophozoite motile form attaches to the epithelial cells in the upper third of the small intestine of its host; the trophozoites multiply rapidly & form a cyst that is excreted in the host animal’s feces

describe the Giardia spp. cyst

has a tough, protective wall around it that allows the protozoa to survive in the environment

how is Giardia spp. identified?

by observing motile, flagellated teardrop-shaped trophozoites in a direct fecal using saline; view on 40x

what movement pattern & appearance are characteristic of Giardia spp. trophozoites?

a “falling leaf” movement pattern & a “monkey-faced” appearance (when stained)

which solution is recommended for recovering the cyst stage of Giardia spp?

zinc sulfate

because Giardia spp. cysts are shed in the feces intermittently, what should you do?

at least 3 separate NPS fecal samples should be examined in-house over the course of a week before ruling out Giardia spp.

what are 3 reasons Giardia spp. infections are difficult to identify?

1. misidentification of Giardia spp. cysts

2. cysts are shed intermittently & readily deteriorate in fecal flotation solutions

3. trophozoites are only found in very fresh diarrhea

pet birds infected with Giardia spp. usually have what kind of diarrhea?

voluminous, chunky, “pea-soup”

what disease process is commonly associated with Giardia spp. infection in cockatiels?

an allergic skin condition resulting in feather picking

what are the primary control measures for Giardia spp. in birds?

good sanitation & preventing access to contaminated food/water sources

T/F: heavy Giardia spp. infections in birds are usually non-pathogenic

false - they can be fatal

What is the recommended protocol for treating a confirmed Giardia spp. infection?

Follow the DVM treatment protocol.

what two genera are commonly called coccidia?

Eimeria spp. & Cystoisospora spp.

coccidia are __________ parasites of the __________ epithelium

intracellular; intestinal

what factors are known to be associated with coccidiosis infection?

stress, overcrowding, improper ventilation, poor sanitation

coccidiosis caused by Eimeria spp. affects which species?

ruminants, poultry, rabbits, pigs, horses, rodents

coccidiosis caused by Cystoisospora spp. affects which species?

dogs, cats, pigs

regardless of the animal species, coccidiosis is most serious in…

young animals

what is the pathogenesis of coccidiosis?

destruction of infected intestinal epithelium

what are the clinical signs of coccidiosis?

diarrhea, anorexia, weakness, dehydration, occasionally bloody stools

how are coccidia transmitted?

by the ingestion of infective (sporulated) oocysts

the term ________ is reserved from all members of the class coccidia

oocyst

what is the infective stage of coccidia (that is ingested by the host)?

sporulated oocyst

the sporulated oocysts of Eimeria spp. can be differentiated from those of…

Cystoisospora spp.

How many sporocysts does Eimeria spp. contain?

4 sporocysts

coccidiosis caused by Eimeria spp. is most important in which animals?

poultry, ruminants (especially young sheep & goats), rabbits

what are the clinical signs of Eimeria stiedae?

wasting, diarrhea, ascites, polyuria, death

Eimeria spp. that infects horses (primarily foals)

Eimeria leukarti

what testing method is used for Eimeria leukarti oocysts recovery?

fecal sedimentation

T/F: the oocysts of Eimeria leukarti will NOT float

true - they are much larger & heavier than other coccidian oocysts

T/F: in foals, Eimeria leukarti is highly pathogenic

false - it is of minor pathogenicity in foals & infections are asymptomatic & self-limiting

coccidiosis in piglets is caused by what genus & species?

Cystoisospora suis

Cystoisospora suis causes…

severe enteritis, diarrhea (scours), and decreased weight gain (economic problem)

what is the prepatent period of Cystoisospora suis?

two weeks

what protozoa (genus & species) causes coccidiosis in puppies & kittens?

puppies = Cystoisospora canis; kittens = Cystoisospora felis

what are the clinical signs of coccidiosis in puppies and kittens?

diarrhea, weight loss, dehydration, and (rarely) hemorrhage

Cystoisospora canis & Cystoisospora felis causes…

anorexia, vomiting, depression, and death

what is the prepatent period for Cystoisospora spp. in dogs & cats?

1 - 2 weeks

what are 3 primary methods for controlling coccidiosis?

1. good husbandry (caging, sanitation, ventilation, nutrition)

2. eliminate overcrowding / other stressors

3. treatment per DVM

are Eimeria spp. and Cystoisospora spp. zoonotic?

no, they do not have any effect on humans

what type of parasites are Cryptosporidium spp?

coccidian parasites

what is the site of infection of Cryptosporidium spp?

small intestine

in which industry is Cryptosporidium spp. considered a significant parasite?

the dairy industry

which animals are most susceptible to cryptosporidiosis?

very young (nursing) animals or immunocompromised people or animals

how is Cryptosporidium spp. infection transmitted?

ingestion of infective oocysts

what is the most common clinical sign of cryptosporidiosis?

diarrhea

what is the prognosis of cryptosporidiosis in adult, immunocompetent animals & people

tends to be self-limiting

Cryptosporidium _______ has occasionally been associated with diarrhea in cats & neonatal puppies

Cryptosporidium parvum