Vector-Borne Infectious Diseases

Question 1

what are infectious diseases?

Answer 1

• illnesses caused by bacteria, viruses, parasites, and fungi
  
  • can be transmitted from an infected host to a susceptible individual of the same or another species

Question 2

what is an agent?

Answer 2

infectious microorganism or pathogen (virus, bacterium, parasite, or other microbes

Question 3

what is a host?

Answer 3

• human who can get the disease
  
  • various risk factors can influence that individual’s level of exposure, susceptibility, or response to an agent

Question 4

what is a vector?

Answer 4

living organism that can transmit infectious pathogens between humans or from animals to humans

Question 5

what is a reservoir?

Answer 5

• habitat in which the infectious agent normally lives, grows, and multiplies
  
  • reservoirs include humans, animals, and the environment

Question 6

what are pathogens?

Answer 6

organisms (bacteria, viruses, parasites and fungi) that cause disease in human beings

Question 7

what is endemic?

Answer 7

when the infection is regularly found among particular people or in a certain area

Question 8

what is transmission?

Answer 8

the process whereby an agent leaves its reservoir or host through a portal of exit

Question 9

what is a mode of transmission? what are the different types?

Answer 9

• when an agent is transmitted from its natural reservoir to a susceptible host in different ways
  
  • Direct - direct contact or droplet spread
  • Indirect - airborne, vehicle, or vector-borne

Question 10

what is the chain of infection?

Answer 10

is usually a cycle, no clear start or end
1. susceptible host
2. pathogen
3. reservoir
4. portal of exit
5. mode of transmission
6. portal of entry
back to susceptible host

Question 11

what is a vector-borne disease?

Answer 11

a disease carried and transmitted by vectors (living organisms that can transmit infectious pathogens between humans, or from animals to humans)

Question 12

what are vector-borne diseases caused by? what are some examples of vector-borne diseases?

Answer 12

• Caused by parasites, viruses and bacteria transmitted by vectors
• Carry and transmit an infectious pathogen into another living organisms
• Examples include: Malaria, Dengue, Chikungunya, Zika, West Nile Virus

Question 13

what are zoonotic diseases? how are they spread? what are some examples?

Answer 13

• Diseases/infections that are transmitted from vertebrate animals to humans
• Bacterial, viral, or parasitic
• Can spread through both direct contact or via food/water/environment
• Examples include: Rabies, Ebola, supposedly Covid-19

Question 14

what is the process of zoonotic diseases?

Answer 14

• microbes are a part of wildlife diversity
• land degradation causes microbe communities to be altered
• habitat loss causes increased interaction among animals and humans
• zoonotic spillover among wildlife, livestock, and people

Question 15

what are the four main drivers of zoonotic disease emergence?

Answer 15

1. land-use change
2. wildlife trade
3. intensified livestock production
4. climate change
   - drivers are interconnected and often overlapping

Question 16

what is malaria?

Answer 16

• malaria is a vector-borne disease
• caused by protozoan parasites and is transmitted by mosquitos
• parasite is present in tropical and subtropical regions

Question 17

how does malaria progress and how prevalent is it?

Answer 17

• individual is bit by an infected mosquito → incubation period (7-30 days) → symptoms occur
• in 2022, a total of 249 million cases of malaria were measured worldwide
  
  • 608,000 deaths occurred
  • most cases occur in African Regions (i.e. in 2022 → 94% of cases)

Question 18

what is dengue fever?

Answer 18

• dengue fever is a vector-borne disease
• caused by Dengue Virus (DENV) and is transmitted by mosquitos
• found in tropical and subtropical urban/semi-urban areas

Question 19

what are the symptoms of dengue fever? can it be treated? how prevalent is it?

Answer 19

• may be mild, acute flu-like illness, or severe
• no specific treatment
• ½ world’s population is now at risk
  
  • estimated 100 – 400 million infections/year

Question 20

what is lyme disease? why is it increasing?

Answer 20

• lyme disease is a vector-borne diseases
• cause by the bacteria Borrelia burgdorferi and is transmitted through ticks
• ticks used to hibernate and die during winter months during frost/freezing
  
  • less frost = ticks are surviving and spreading further

Question 21

what are the two types of ticks that can spread lyme disease in Canada?

Answer 21

• backlegged tick (deer tick) (in Southeastern and Southcentral Canada)
• western blacklegged tick in BC

Question 22

what are some other mosquito related diseases?

Answer 22

• Yellow Fever - we have a vaccine now, it is most prevalent in African regions
• West Nile virus (WNV) - increasing in Canada, mostly in the US, spread indirectly from birds that were bit by mosquito
• Zika virus fever - no vaccine, seen in tropical/subtropical regions, can affect the brain
• Chikungunya fever (CHIKV) - seen in tropical/subtropical regions, has increased with malaria and dengue, comes with extreme body pain
• Japanese encephalitis (JEV) - related to dengue and yellow fever, common in asia, permanent brain damage, there is a vaccine

Question 23

how are ancient pathogens becoming more prevalent? what are some incidents?

Answer 23

• melting permafrost exposes ancient pathogens
• much older bacteria and viruses → no immunity in human populations
• Alaska: 1918 Influenza
• Norway: Anthrax from reindeer

Question 24

how can we avoid harm from vector-borne diseases?

Answer 24

Behaviour changes will help reduce the spread of infectious diseases

• checking for ticks after enjoying the outdoors
• wearing long sleeves and pants to avoid bug bites
• washing your hands after coming in contact with wildlife, farm animals or pets