Parasitology

Question 1

What is a parasite?

Answer 1

= an organism that lives on or in a host organism and gets its food from or at the expense of its host eg. Skin or intestine or blood

Question 2

What are the 3 main classes of parasites?

Answer 2

1. Protozoa
2. Helminths
3. Ectoparasites

Question 3

Describe protozoa parasites

Answer 3

• Microscopic, single celled and can be free-living or parasitic in nature
• Able to multiply in humans allowing serious infections to develop from a single organism
• Transmission:
  
  • eg. Living in the human intestine and transmitted by faecal-oral route.
  • Living in blood or tissues are transmitted by an arthropod vector

Examples of infections:

• Entamoeba histolytica - invades intestine and form ulcers
• Giardia lamblia
• Trichomonas vaginalis - STI
• Malaria
• Toxoplasma gondii

Question 4

Describe helminths parasites

Answer 4

• Large, multicellular organisms (worms) visible to naked eye
• In adult form cannot multiply in humans
• 3 main groups:
  
  • Nematodes - roundworms
    
    • Soil-transmitted helminths - hookworm
    • Filarial parasites
  • Trematodes - flukes
  • Cestodes - tape worms

Question 5

Describe ectoparasites

Answer 5

Blood-sucking arthropods - fleas, ticks, lice and mice that attach or burrow into the skin

Question 6

What does parasite infections depend on?

Answer 6

Mode of transmission and opportunities for transmission:

• Faeco-oral
  
  • due to household sanitation or acess to clean water
• Food
  
  • sureillance
  • regulations and government control
  • animal husbandry
• Complex life cycles
  
  • distributions of vectors and hosts present
• Education
• Country-level and regional control programmes
• Availbility of cheap and efficacious treatments
• Environmental sanitation

Question 7

Describe the disease Chagas

Answer 7

• Transmitted through faeces
• Acute illness 1-2 weeks after bite. Mild/asymptotic, last 8-10 weeks. Local swelling, fever, anorexia. 1-2% diagnosed. Caused by tissue damage due to inflammatory response to parasites. Parasites kill antibodies
• Chronic: lifelong infection, parasites at very low levels in tissues - can be seen from parasite DNA.
• Determinate chronic disease: 10-30 years after infection. Heart (invest in the pykrunie fibres) and intestinal tract are affected - constipation, ulceration, obstruction

Question 8

Describe Leishmaniasis

Answer 8

• Tissue damage caused by inflammatory response to presence of parasites in macrophages
• Occurs in rural areas
• Carried in dogs and rodents
• Ulcers, scars, lesions
• Latency - parasites remain present long-term - balance between regulatory response and inflammatory response