Exam 5: Topic 26

Question 1

Describe the characteristics of Trichomonas vaginalis as discussed in class.

Answer 1

• Sexually transmitted.
• Infects urogenital tract surfaces.
• Greater than 4.5 is optimum pH for the organism. Tends to go from asymptomatic to symptomatic when pH increades.
• Symptoms include intense itching, discharge.

Question 2

Explain how the trophozoite stage and cyst stage fit into the lifecycle of a parasitic
protist that spends some time outside of the human host.

Answer 2

• Trophozoite (vegetative body).
• Cyst (hardy form thay survives outside of the body).
• Examples: Giardia is a GI parasite. Infected with Giardia by ingesting spores. They germinate into vegatative cells.

Question 3

Describe the life cycle of Giardia lamblia. Briefly describe the disease that Giardia
is responsible for and include the major source of contamination

Answer 3

• Cyst re enters a new host, it regerminates into a trophozoite
• Cyst enter mouth, get to dogestive system, vegatate, attach to small intestine, induce infalmmatory respinse which produces the diarrhea, trophozoite die but cysts survive and persists. Then cyst gets picked up by another host and life cycle continues.

Question 4

Describe the morphology and any unusual intracellular features of Trypanosoma cells.

Answer 4

2 stained area: one for nucleus and enlarged mitochondria onown as kinetoplasts

Question 5

Outline the basic life cycle of Trypanosoma brucei, and the disease process of African Sleeping Sickness.

Answer 5

• Fly bites infected person and takes up parasite, then bites another host and parasite is injected.
• Parasite makes way to CNS and meningitis-like disease begins.

Question 6

What unusual mechanism does Trypanosoma use to evade and exhaust our immune system?

Answer 6

• Different antigens are displayed (A, B, C) and activates helper t cells and b cells. Be cells make antobodies to doffering antigens. Should activate macrophages and neutrophils to phagocytize parasite.
• Parasite alters cell membrane and change antigens (D, E,F) to evade immune system. And the cycle continues with parasite persisting and immune response is not effective.
• Parasite makes way into CNS where disease is more deadly.

Question 7

List the four stages of Plasmodium vivax, and thoroughly describe the role of each
stage.

Answer 7

1. Merozoite: “middle” of life cycle.
   
   2. Gametocyte (male and female): gamete thay participate in sexual reproduction for malaria parasite.
   3. Trophozoite: vegatative body adapted to human body.
   4. Sporozoite: tough hardy version of organism.

Question 8

Contrast Plasmodium and Trypansoma with respect to the following:

Answer 8

A. Site of infection
• Plasmodium: red blood cells
• Trypanosoma: blood, then CNS
B. Pathogenesis (how they cause death)
• Plasmodium: lyse red blood cells leading to anemia and organ failure.
• Trypanosoma: parasite enter cns and causes meningitis-like symptoms.
C. Transmission (e.g. which vector)
• Plasmodium: mosquito
• Trypanosoma: fly
D. Extracellular or intracellular
• Plasmodium: intracellular
• Trypanosoma: extracellular