Dogs & Cats: Giardia & Cystoisospora spp. (Exam 1)

Question 1

What parasites are included in Giardia sp. and where are they found?

Answer 1

Giardia duodenalis (=Giardia lamblia, Giardia intestinalis)
Humans, mammals, birds, ruminants

Question 2

What is the taxonomy of Giardia sp.?

Answer 2

A flagellates protozoan

Question 3

What is the geographic distribution of Giardia sp.?

Answer 3

Worldwide

Question 4

What is Giardia sp.’s location in host?

Answer 4

Small intestine

Question 5

Draw out the lifecycle of Giardia sp.

Answer 5

Direct!

Question 6

What are the steps of the Giardia sp. lifecycle?

Answer 6

1. Within cysts, organism divides into two trophozoites, excystation occurs in small intestine
2. Attachment of trophozoites to epithelium and division by binary fission
3. Encystment of trophozoites occurs as organism travels down GI tract (dehydration and cholesterol deprivation may trigger encystment); cysts are passed +/- trophozoites

Question 7

What is the first step of the Giardia sp. lifecycle?

Answer 7

Within cysts, organism divides into two trophozoites, excystation occurs in small intestine

Question 8

What is the second step of the Giardia sp. lifecycle?

Answer 8

Attachment of trophozoites to epithelium and division by binary fission

Question 9

What is the third step of the Giardia sp. lifecycle?

Answer 9

Encystment of trophozoites occurs as organism travels down GI tract (dehydration and cholesterol deprivation may trigger encystment); cysts are passed +/- trophozoites

Question 10

What is the prepatent period of Giardia sp.?

Answer 10

5-16 days

Question 11

Define: Prepatent Period

Answer 11

The time from the ingestion of cysts to shedding cyst in the feces
When parasite enters body of definitive host to when it is sexually mature and can reproduce

Question 12

What is the trophozoite form of Giardia sp.?

Answer 12

Motile form in small intestine
Piriform shape, flagellated
Two nuclei (each w large endosome)
Bilaterally symmetrical, dorsoventrally flattened
Binary fission

Question 13

Define: Cyst

Answer 13

A hardy form of the parasite, often allowing it to withstand harsh environmental conditions

Question 14

What is the only way that Giardia trophozoites can be observed?

Answer 14

Wet mounts (direct smear)

Question 15

Why might Giardia be difficult to diagnose via excretion

Answer 15

Excretion of cysts in intermittent
Cyst formation and passage may be sporadic (consider testing 3 times between 5-7 days)
Often confused with other things

Question 16

What are the diagnostic tests for giardia?

Answer 16

A [modified double centrifugal] flotation using zinc sulfate or a giardia snap test may only detect 75% of cases (may consider testing on 3 consecutive days)
Immunofluorescent assays
ELISAs (Antigen test)
PCR
Wet Mounts (Iodine may kill trophozoite)

Question 17

Can giardia be detected in asymptomatic adult dogs?

Answer 17

Persistent detection of cyst wall antigen in chronically infected asymptomatic adult dogs

Question 18

What can alter the morphology of Giardia on fecal flotation analysis?

Answer 18

Appearance depends on media, magnification, and staining
May be smashed (crescent shaped) or stained (w iodine)

Question 19

In what specific environments is Giardia most prevalent? What species?

Answer 19

Infections in dogs with clinical signs averaged 15.6% in dogs in US
Animals in shelters, breeding facilities, kennels, and catteries are more likely to carry Giardia duodenalis
Increased prevalence among dogs that visit dog parks

Question 20

What are the transmission dynamics of Giardia sp.?

Answer 20

Transmission occurs through ingestion of cysts acquired from fecal-contaminated water, food, fomites, or through self-grooming
Dog strains don’t infect cats and vice versa

Question 21

What is the pathogenesis of Giardia?

Answer 21

Trophozoites attach to enterocytes in small intestine
Functional changes and blunting of intestinal villi
Maldigestion, Malabsorption, and diarrhea

Question 22

Clinical Signs of Giardia sp.

Answer 22

Highly variable
Asymptomatic
Chronic, pasty diarrhea, weight loss (may be greasy/mucoid)
Lethargy, flatulence
Failure to thrive, impacts on growth
+/- dry skin, poor haircoat

Question 23

Treatment of Giardia sp.

Answer 23

No drugs approved for treatment in US
Metronidazole (efficacy may be low)
Albendazole effective (NOT SAFE IN DOGS)
Fenebendazole approved in UK
A combination of febantel, pyrantel pamoate, and praziquantel is effective in treating giardia in dogs when administered daily for 3 days

Question 24

Describe refractory period of Giardia

Answer 24

Failures may result from: reinfection, inadequate drug levels, immunosupression, drug resistance, and Giardia sequestration in the gallbladder or pancreatic ducts

Question 25

Control & Prevention of Giardia sp.

Answer 25

Avoid contact with contaminated water
Utilize disinfectants where possible
Treatment + Bathing + Proper Feces Removal

Question 26

What parasites are found under Cystoisospora spp.?

Answer 26

Cystoisospora felis, C. rivolta, C. canis, C. ohioensis-like

Question 27

What is the taxonomy of Cystoisospora spp.?

Answer 27

Apicomplexan
Widely referred to as “coccidia”

Question 28

What is the geographic distribution of Cystoisospora spp.?

Answer 28

Worldwide

Question 29

What is the location of the host of Cystoisospora spp.?

Answer 29

Small intestine

Question 30

Describe the life cycle of Cystoisospora spp.

Answer 30

Question 31

Define: Macrogametocyte

Answer 31

Female gamete

Question 32

Define: Microgametocyte

Answer 32

Male gamete

Question 33

Define: Schizont

Answer 33

Cell that divides by shizogany, release merozoites

Question 34

Define: Merozoite

Answer 34

Infect RBCs

Question 35

Define: Sporozoite

Answer 35

Motile, spore-like stage

Question 36

What is the morphology and diagnosis of Cystoisospora spp.?

Answer 36

Sporulated oocysts are usually used to identify the various species of coccidia Cystoisospora spp.
Very host specific

Question 37

What is the prevalence of Cystoisospora spp.?

Answer 37

Ranges from 3% to 38% of dogs in North America
Infections more likely in young

Question 38

What are the transmission dynamics of Cystoisospora spp.?

Answer 38

Canine coccidia are acquired by ingestion of sporulated oocysts from contaminated environments (+/- transport hosts)
Highly host specific

Question 39

What is the pre-patent period of Cystoisospora spp.?

Answer 39

Varies by species

Question 40

What are the environmental factors for Cystoisospora spp.?

Answer 40

Development of oocysts to infective sporulated oocysts (sporulation) does not occur above 40C or below 20C
Sporulation occurs rapidly (<16hrs) at optimal temperatures
Sporulated oocysts are resistant to adverse environmental conditions and can survive as long as one year in moist, protected environments

Question 41

What are the clinical signs associated with Cystoisospora spp.?

Answer 41

Diarrhea with weight loss
Dehydration
+/- Hemorrhage
Severe: anorexia, vomiting, depression

Question 42

What is treatment for Cystoisospora spp.?

Answer 42

Sulfadimethoxine (only approved)
Ponazuril (appears to be effective)

Question 43

What are control considerations of Cystoisospora spp.?

Answer 43

Daily removal or feces can aid in preventing environmental contamination from with oocysts
Once infective, oocysts are resistant to most disinfectants and can survive months in the environment
Disinfectants containing high concentrations of ammonia can destroy oocysts
Steam and pressure washing may dislodge feces surfaces
Painting or sealing kennel floors will help prevent adherence of feces to these surfaces

Question 44

Is Cystoisospora spp. zoonotic?

Answer 44

No, highly species specific