Unit 2-Parasitism Flashcards
What are the six common parasitic groups?
Protists
Nematodes
Arthopods
Viruses
Platyhelminthes
Bacteria
What is a relatively inefficent mechanism of transmission?
Direct Contact
Give examples of two key parasites with intermediate hosts
Schistomosoma
Plasmodium
How are endoparasites of body cavities transmitted?
Direct Contact
Consumption of Intermediate Host
How are ectoparasites transmistted?
Direct Contact
Give an example of an endoparasite of the body cavity
Tapeworm
Give an example of an endoparasite of the body tissue
Plasmodium
How are endoparasites of the body tissue transmitted?
Vectors
What is HIV caused by?
A virus
Define a virus
Infectious agents that can only replicate inside in a host cell
Describe what is in the structure of a virus
Antigens on the surface
Nucleic Acid (RNA/DNA)
Protein Capsid
Outer Envelope
What is a protein capside?
Protective protein coat surrounding the nucleic acid
What are the two types of nucleic acids found in viruses?
RNA and DNA
Why are viruses not classed as living?
Do not carry out any of the normal functions for life except for reproduction, which they can only do in the cell of living organisms
Describe the stages in virus reproduction
- Virus antigens to host cell surface
- Virus DNA inserted into host cell
- Virus DNA is replicated by host enzymes
- Virus genes are transcribed to RNA which is translated to make viral protein coats
- New virus particles are assembled and burst out of the host cell
Give examples of DNA viruses
Chickenpox
Herpes
Small pox
Give examples of RNA viruses
Influenza
Hepatitis
Ebola
What differs in RNA viruses replication?
Viral RNA genome is replicated directly using an enzyme from the virus
Give an example of RNA retroviruses
HIV
How do RNA retroviruses replicate?
Use the enzyme reverse transcriptase to form a DNA copy of the virus genome. When virus is reproducing, the DNA copy of the genome will be transcribed to RNA which is then translated to make new viral proteins.
What are the two type of first line defences?
Physical Barriers
Chemical Secretion
Describe the role of mucus in preventing parasite infection
Mucus in the lungs trap microbial parasites and are moved away from delicate tissues by cilia
Describe physical barriers to parasite infection
Skin acts as a tough barrier
Skin is dry so many parasites die on surface
Nasal hair trap parasites
How do tears prevent parasites?
Contain antibodies and lysosomes
When are second line responses triggered?
After the parasite has entered the body fluid
What are the three type of second line defences?
Inflammatory Responses
Phagocytes
Natural Killer Cells
Describe an inflammatory response
Some injured cells release chemicals including histamine
Cause local blood vessels to dilate
Increases blood flow to the area
Stimulating phagocytes to migrate to the area
What are phagocytes?
White blood cells which are able to migrate from the blood into tissue fluid
What do phagocytes do?
Check surface of the particles for self antigens, if not found, phagocyte engulfs and digests the object
What do phagocytes do after digestion of non self objects?
Present the fragments of the foreign antigens on the surface
What are natural killer cells?
Type of white blood cells which detect abnormal cell surface proteins
What do natural killer cells do?
Attach to cells which have abnormal surface proteins and release chemicals into them triggering apoptosis
What are specific cellular defences triggered by?
The antigens on the surface of the parasite
What are lymphocytes and where are the typically found?
White blood cells mainly found in the lymph gland
What are the two types of lymphocytes?
B and T lymphocytes
What are the two roles of T lymphocytes?
- Stimulate other T lymphocytes and cause B lymphocytes to divide rapidly
- Destroy infected cells
What do B lymphocytes do?
Produce antibodies which attach to pathogens allowing phagocytes to engulf and digest them
What is it called when some T and B lymphocytes are kept after parasite infection?
Immunological Memory
What is clonal selection?
Response of lymphocytes when they bind to their specific antibodies causing rapid replication
What is a benefit of immunological memory?
Faster and bigger response to future parasite infection of the same parasite
What are the three ways parasites evade the immune system?
- Mimic the host antigens
- Antigenic Variation
- Modify host’s immune system
What is Epidemiology?
Study of outbreak and spread of infectious diseases
What can the information from epidemiology studies can be used to do?
Plan and evaluate strategies to prevent the spread of parasites in the future
What is herd immunity?
Way to prevent the s[read of diseases by vaccinating enough members of a population to limit the spread of parasites
What is the herd immunity threshold?
Minimum density of resistant hosts required in a population to prevent the epidemic
What are the three problems associated with developing vaccinations?
- Many parasites are difficult to culture in a lab away from hosts
- Parasites have very rapid evolution and change surface antigens regularly
- Host Parasite Interconnection of Metabolism
Why is host parasite interconnection a problem in developing vaccinations?
Often vaccinations are highly linked which makes it difficult to find new drug compounds that only target the parasite
What are the benefits of improved parasite control?
- Reduction in child mortality
- Improvement in child development/intelligence
- Body is able to use more resources for growth and development
What may be the only effective control strategy for parasites?
Target the transmission stage
What two things are used to target the transmission stage of a parasites lifecycle?
Civil Engineering Projects
Co-ordinated vector control strategy
How do civil engineering projects target transmission?
All work to improve sanitation
Prevents mixing of drinking water and contaminated water
E.g. Clean water supplies, sewerage systems
