Lecture 22

Question 1

What is a disease?

Answer 1

An abnormal condition that negatively affects the structure or function of part or all of an organism, and that is not due to an external injury.

A disease may be cause by external factors (e.g. pathogens) or by internal factors (e.g. autoimmune disorders).

Question 2

What are the types of causes of diseases?

Answer 2

1. Airborne (pathogens transmitted through air).
2. Food borne (foods w/pathogenic bacteria, viruses, or toxins).
3. Lifestyle (industrialized countries, unhealthy foods).
4. Non-communicable (can’t spread b/w ppl).
5. Infectious (presence and growth of pathogen in a host).

Question 3

What is the difference between contagious and communicable diseases?

Answer 3

They are both an infectious disease.

Contagious: infection that spreads commonly from one person to another (e.g. common cold).

Communicable diseases: does not necessarily spread through everyday contact (e.g. ringworm).

Question 4

What is the difference between a parasite and a pathogen?

Answer 4

1. A parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host.
2. Pathogens are organisms that causes diseases within their host.

A parasite can cause a disease in the host therefore a parasite can be a pathogen.

Question 5

What is an epidemic?

Answer 5

A widespread occurrence of an infectious disease in a community at a particular time.

Question 6

What explains a driver of diseases for humans?

Answer 6

Community structure - explaining patterns of biodiversity.

Humans constantly created new ways of living and eating, and genetic changes evolved to minimize the effects of these diseases.

Question 7

Explain aboriginal people and the arrival of Europeans.

Answer 7

When Europeans arrived, the diseases they brought with them set off one of the largest depopulations in human history.

Before Europeans, diseases like measles or yellow fever did not exist —> aboriginal populations reduced by epidemic disease.

Question 8

Explain the planned extinction of small pox.

Answer 8

Highly contagious and destructive human disease.

Worldwide immunization program - first use of a vaccine to treat a viral disease.

Question 9

Explain the black plagues and its origins.

Answer 9

Caused by a bacterium that circulates among wild rodents (e.g. rats) where they live in great numbers and density.

Thought to originate in Asia. Due to climate fluctuations, rodents began to flow the dried out grasslands to more populated areas, spreading the disease.

Question 10

Explain life after the Black Plague.

Answer 10

Rising standards of living after the epidemic.

• food prices dropped and labor wages increased
• more resources available
• higher proportion of older adults, lower mortality risks (skeletal samples)

Question 11

Why was the 1918 Influenza pandemic so bad?

Answer 11

It was not more agressive than previous influenza, but that the special circumstances of the epidemic (malnourishment, overcrowded medical camps and hospitals, poor hygiene) promoted bacterial superinfection that killed victims.

Occurred during WW1 - close quarters and massive troops movement fuelled the disease.

Prevention and treatment methods for flu were limited.
- no vaccine, no antiviral drug, no antibiotics.

Question 12

What were the impacts of the Spanish flu?

Answer 12

Virus disproportionately affected young men = labor shortage and more women in the workforce, which helped advance women’s rights.

Question 13

Explain malaria.

Answer 13

Mosquito-borne infectious disease that affects humans and other animals - not spread from person to person.

Caused by eukaryotic microorganism (not bacteria) that is parasitic to insects.

Mosquito bite introduces the parasite from mosquito’s saliva to person’s blood - the parasites travel to the liver where they mature and reproduce.

Prévenant in tropical or subtropical regions. Mosquito larvae mature and better breeding grounds.

Question 14

Explain malaria and the Panama Canal.

Answer 14

Isthmus of Panama was an ideal environment for mosquitos. The control of malaria was vital for the construction of the Panama Canal.

Big sanitation campaign to rid the isthmus of mosquitos. Death rate and yellow fever reduced.

The barrier of disease had even removed and the Panama Canal was competed in 1914.

Question 15

What is virulence?

Answer 15

A pathogen’s ability to infect or damage a host.

More virulent = less transmission.
Less virulent = more transmission.

Question 16

Explain sexually-transmitted pathogens.

Answer 16

These pathogens will be selected against if they immobilize their host too soon, before the host has the opportunity to find a new sexual partner and unwittingly pass on the pathogen.

Question 17

Explain the link between climate change and diseases.

Answer 17

Because of rising temperatures and changing rainfall patterns, climate change is expected to have a substantial effect on the burden of infectious diseases.

Humans and animals are forced to compete for dwindling habitat and resources.

Insect vectors tend to be more active at higher temperatures.

Question 18

Explain the threat that mosquitos have on native hawaiien birds.

Answer 18

Rising temperatures allowed for mosquitoes to expand into birds’ high elevation ranges - native birds are no longer safe from diseases (they are very susceptible due to isolation).

Some birds retreated to higher grounds where its too cold for mosquitoes.

With climate change and rising temperatures, the birds are no longer safe.

Question 19

How could we solve the avian malaria solution?

Answer 19

Protects birds from malaria by killing mosquitoes with chemicals.

But mosquitoes breed in less than a teaspoon of water and can do so anywhere in Hawaii; their eggs are inaccessible, hidden.

Poison that kills mosquitoes often kills plants and animals that surround them.

Planned extinction is a possibility.

Question 20

How is Ebola linked to climate change?

Answer 20

1. Increase in weather events plays a role in Ebola outbreaks. Dry seasons followed by heavy rainfalls produce an abundance of fruit. Fruits = bats and apes eat together, which provides opportunities for the disease to jump between species (fruit bats carry diseases). Humans can contract the disease by eating or handling the infected animals.
2. Climate change increases severe dry spells that hit agricultural yields and drive humans into the forest for food (bushmeat).
3. Deforestation leads to habitat loss and more people entering the forest, which forces animals like bats to find new habitats and hunt for food near humans.