More Flagellated Protozoans

Question 1

Describe the appearance of the Giardia duodenalis parasite

Answer 1

Rounded anteriorly and pointed posteriorly. Have adhesive disks (adhesive microtubules) on ventral side to stick to host cells and 2 prominent nuclei. Have 8 flagella in 4 pairs . Dorsal is convex, ventral is concave

Question 2

Describe the flagella of the Giardia parasite

Answer 2

1st pair anchors in kinetosome at anterior. Posterior pair runs through more of the cytoplasm and exist near the posterior portion. Caudal flagella run entirely through flagella and run through cytoplasm and come through point at the end of the trophozoite. Ventral flagella come out of the ventral side.

Question 3

Describe the Giardia cyst. What stage of the life cycle is this?

Answer 3

HAve a thick wall, 4 nuclei. IS the desiccation-resistant transmissible stage

Question 4

Most Giardia infection occurs in the _____

Answer 4

Duodenum

Question 5

How does a Giardia infection build up?

Answer 5

They divide through binary fission so populations can build up rapidly to the point where trophozoites can infect almost every cell in the small intestine.

Question 6

At what point to Giardia form cysts?

Answer 6

When stools dry out in the colon, cysts form.

Question 7

How do Giardia produce symptoms?

Answer 7

They may cause watery diarrhea, loss of weight, fatty stools, interference with fat/nutrient absorption (ex. Vitamin B or A) - this may be because of large number of parasites on intestinal epithelium

Question 8

Are symptoms always present with Giardia infection?

Answer 8

Asymptomatic infections do exist, but they are still transmissible. This varies by strain of parasite/host immunity. The disease can also go in stages, with intermittent symptomatic and asymptomatic stages

Question 9

A Giardia infection is referred to as ____

Answer 9

Giardiasis

Question 10

In what areas are Giardia infections common?

Answer 10

Areas with poor water filtration, near beaver ponds, downstream from livestock operations

Question 11

How is Giardiasis treated?

Answer 11

With metronidazole, nitroimidazoles, quinacrine

Question 12

The parasite Spironucleus meleagridis affects many turkeys. Describe how it is similar to Giardia. How is it controlled?

Answer 12

Morphology is similar except it has no median bodies, no sucking disk, different flagella arrangement. This parasite is controlled by separation of young birds from parasitized survivors.

Question 13

What is the most important feature of the Trichomonadida

Answer 13

Do not produce a cystic stage - must be transferred via direct contact of fluid

Question 14

Briefly describe the basic structure of Trichomonadida trophozoites

Answer 14

Have a complex flagellar system consisting of a undulating flagellum/membrane over 1/2 of body. They have a very small cytostome. The Costa is a bar running along the base of the undulating membrane. They have axostyles (median rods) running through the middle of the body

Question 15

Where does Trichomonas tenax live? Why is this important?

Answer 15

In gaps between gums and teeth in the mouth. It is harmless and feeds on bacteria. They cannot infect you as they do not form cysts and will not survive your stomach. They are passed by kissing.

Question 16

Where does Trichomonas vaginalis live?

Answer 16

In reproductive tracts of both sexes

Question 17

What symptoms does T. vaginalis infection cause?

Answer 17

Increased blood flow to vagina, cheesy-smelling yellowish “exudate”

Question 18

What does T. vaginalis look like?

Answer 18

LArger than T. tenax, produced pseudopodia

Question 19

How can T. vaginalis be transferred, outside of sexual contact?

Answer 19

Via moist towels that are shared

Question 20

Does T. vaginalis have a 100% infection rate?

Answer 20

No, the natural acidic pH of the vagina should be hostile to it, but feminine hygiene products may affect pH enough to make infection easier

Question 21

How is T. vaginalis infection diagnosed?

Answer 21

Microscopic identification of flagellates in scrapings/from discharge

Question 22

How is T. vaginalis infection treated?

Answer 22

With Flagyl, but there is some resistance documented

Question 23

What does Histomonas meleagridis attack and what does it cause?

Answer 23

Attacks birds such as domestic turkeys. Causes “black head”, infectious enterohepatitis. Black pigments accumulate in the head. Causes liver/metabolic dysfunction.

Question 24

What does Histomonas meleagridis look like?

Answer 24

Reduced flagella, have no cysts but the trophozoites have many possible forms, They are amoeboid and reproduce by binary fission

Question 25

How is Histomonas meleagridis transmitted?

Answer 25

Via nematode eggs (Histomonas survives in nematode gut, infects egg, and nematode eggs act as a cyst wall)

Question 26

How does Histomonas meleagridis infection occur?

Answer 26

Cause lesions in caecum and liver of birds.