Protozoas/Helminths (complete)

Question 1

Define parasite

Answer 1

• An organism

- Lives upon or w/in another living organism at whose expense it obtains some advantage

Question 2

Explain the importance of parasitic diseases for human health from a global perspective

Answer 2

• Prevalent worldwide
• Impact morbidity, DALYs, and mortality
• Primarily in developing countries (uncommon in US)
• These diseases can be prevented!!!

Question 3

Why are the life cycles of parasites important for the geographic distribution, diagnosis, and control of parasitic disease?

Answer 3

• Ability of parasites to infect specific tissues (tropism) is essential for their life cycles
• Geographic distribution of parasites limited by host availability
• A detailed h/o travel and activities is essential for diagnosing most parasitic diseases

Question 4

What are the different groups of helminths that cause parasitic diseases in humans?

Answer 4

1) Roundworms
2) Flatworms (Flukes)
3) Tapeworms

Question 5

What are the different groups of protozoan parasites that cause parasitic diseases in humans?

Answer 5

1) Amebas
2) Flagellates
3) Ciliates
4) Sporozoa
5) Microsporidia

Question 6

Explain the pathogenesis of schistosomiasis a paradigm of important diseases caused by metazoan and protozoan parasites

Answer 6

• Transmitted via contaminated fresh water
• Causes acute problems => chronic disease affecting intestinal or urinary system
• Affects 200-300 million people per year
• 200,000 deaths per year

Question 7

What type of parasite is schistosomes?

Answer 7

A flatworm

Question 8

What is the geographic distribution of schistosomes?

Answer 8

Developing countries

Only seen in US in immigrants or recent travelers (GET THAT HISTORY!)

Question 9

Describe the life cycle of schistosomes

Answer 9

• Eggs shed in feces/urine of infected humans => hatch in fresh water => release miracidia (infecting snails)
• Snails then develop sporocytes then released into water => infects humans

Question 10

Describe the major strategies to control schistosomiasis

Answer 10

• Public health ed (avoid water, wells, latrines)
• Molluscicides => control spred
• Drugs (praziquantel) in infected ppl

Question 11

General info on malaria

Answer 11

• Affects >1 billion people, 1-3 million deaths per year
• Many types
• Eliminated from US, Canada, Europe, Russia

Question 12

Describe the life cycle of malaria parasites

Answer 12

• Infected mosquitos bite humans => inject sporozoites in blood
• Asexual develops occurs in humans (specifically liver cells)
• Merozoites eventually released into blood => infect erythrocytes => can infect unaffected mosquitos

Question 13

Describe the pathogenesis of malaria

Answer 13

• Symptoms associated with rupture of infected erythrocytes and release of merozoites
• Fever, anemia, jaundice, hypotension, tachycardia, hepatosplenomegaly

Question 14

How is malaria diagnosed?

Answer 14

• Gotta detect asexual forms of parasites in blood => via thick/thin blood films
• Blood smears

Question 15

What are some genetic diseases that produce resistance to malaria?

Answer 15

• Sickle cell
• Ovalocytosis
• G-6-P deficiency
• Thalassemia

Question 16

Describe some principles for malaria control

Answer 16

• Limit breeding grounds from mosquitos (no standing water)
• Avoid exposure (repellent, bed nets, insecticide sprays)
• Use of anti-malarial drugs for chemoprophylaxis and treatment
• Develop vxs (not available yet)

Question 17

Describe acquired immunity against malaria

Answer 17

• Prevents high-level disease — doesn’t eradicate infection
• immunity is species and strain specific (mechanisms of protection poorly understood)
• Immunity declines when an individual lives outside an endemic area for several months
• No vaccines