DISEASE E&E (Introduction)

Question 1

Infection:

Answer 1

-invasion of an organism’s body tissue by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce

Question 2

Infectious disease:

Answer 2

-also known as transmissible disease or communicable disease
-illness resulting from an infection

Question 3

What common words do we use for infectious agents?

Answer 3

-pathogens
-vector
-parasites

Question 4

Pathogen:

Answer 4

-anything that can produce disease

Question 5

Parasitism:

Answer 5

-a relationship between species where one organism (parasite) lives on or in another organism (host) causing it harm and is adapted structurally to this way of life

Question 6

Parasite:

Answer 6

-any organism that decreases the fitness of its host by infecting it
-ecological definition includes both micro-parasites (ex. viruses and bacteria) and macro-parasites (ex. worms)

Question 7

Examples of parasites:

Answer 7

-tape worm
-mites
-parasitoid wasp
-cuckoo
-ticks
-HIV

Question 8

What is NOT an infectious disease?

Answer 8

-genetic (or hereditary) diseases (hemophilia)
-environmentally-caused diseases (scurvy)
*most disease have both genetic and environmental origins

Question 9

Ecology:

Answer 9

-study of spatio-temporal distribution of infectious diseases
-reflects the interactions of host populations with pathogen (or parasite) populations in the environment over time
*emphasizes infectious diseases of animals

Question 10

Epidemiology:

Answer 10

-branch of medicine
-deals with incidence, distribution and possible control of diseases and other factors relating to health
-includes non-infectious disease (smoking, addictions, obesity, etc.)
*human medicine and includes non-infectious diseases

Question 11

The disease triangle:

Answer 11

-for a parasite to cause pathology, need:
>parasite
>susceptible host
>environmental conditions must be sufficient to result in disease
*3 critical elements

Question 12

Importance of infectious diseases:

Answer 12

-cause morbidity and mortality in their hosts, reduce productivity of farm animals (cattle, sheep)
-stop trade and travel across international borders (BSE)
-threaten food security for people in developing world
-spillover of pathogens from wildlife to domestic animals

Question 13

SARS-CoV-2:

Answer 13

-originated in wildlife (bats) before spilling over into humans
-maybe racoon dog was intermediate host?

Question 14

Study of pathogens and infectious diseases in animals:

Answer 14

-domain of veterinarians and disease ecologists

Question 15

2001 Foot-and-mouth outbreak in the UK:

Answer 15

-viral disease that affects cloven-hoofed animals
-no risk to humans (not zoonotic)
-over 2000 farms recorded cases
-highly contagious and difficult to stop
-economic cost to farming and tourism was $16billion USD
*example of how infectious disease can have devasting economic consequences

Question 16

Rinderpest in Africa:

Answer 16

-highly infectious viral disease of cattle
-close cousin of Measles virus
-was brought to Ethiopia in 18880s by Italian colonists who imported infected cattle from India
-spread rapidly through eastern and southern Africa
-killed more than 90% of domestic cattle and huge numbers of wild ungulates (multi-host pathogen)
-1/3 of Ethiopians and 2/3 maasai in Tanzania starved to death
*how infectious diseases of livestock threaten food security

Question 17

Multi-host pathogen:

Answer 17

-it can affect many different host species
-cattle and buffalo have mortality rates of ~100%
-sheep and goats less serious
-pigs and deer have asymptomatic disease

Question 18

Host factors:

Answer 18

-species
-genotype/breed
-sex
-age
-nutritional condition
-immune status

Question 19

2 types of cattle:

Answer 19

1. Taurine (Bos Taurus)
2. Zebu (Bos Indicus)

Question 20

Taurine cattle:

Answer 20

-temperate climates (Europe, northern Asia, West Africa)
-European taurine: high milk yields, meat quality, etc

Question 21

Zebu cattle:

Answer 21

-hot arid and semi-arid regions of Asia and Africa
-larger sweat glands and resistance to ticks
-lower water and fodder requirements
-stronger herding instincts
-different vocal sounds
-meat is tougher

Question 22

Cattle breed and TB pathology:

Answer 22

-chronic disease
-most common mode of transmission: inhalation of droplets in aerosols and from ingestion of contaminated food and water
-infected taurine (Holstein) vs. Zebu (Boran) cattle with M. bovis and scored the lungs
>lung pathology higher in taurine vs. zebu

Question 23

Covid mortality rate:

Answer 23

*depends on age
-increases as get older
-higher in males

Question 24

Pathogen or parasite factors:

Answer 24

-pathogen species
-pathogen genotype/strain/isolate/variant
-infectivity/transmissibility
-burden/load/abundance
-infectious dose
-pathogenicity/virulence
-immune evasion

Question 25

Infectivity:

Answer 25

-probability that pathogen will establish infection in host following exposure

Question 26

Burden:

Answer 26

-number of pathogen units in host tissues

Question 27

Pathogenicity:

Answer 27

-pathogen-induced damage or pathology in the host

Question 28

Immune evasion:

Answer 28

-pathogen ability to avoid clearance by the host immune system

Question 29

SARS-CoV-2 variant waves:

Answer 29

-multiple waves caused by different variants of concern (VOCs)
-many were short lived
-changes what you need in vaccine
-increased transmissibility

Question 30

Why do we care about SARS-Cov-2 variants?

Answer 30

-variants with higher transmissibility will cause more cases
-variants with higher pathology will cause more severe disease
-vaccines based on older variants may not protect against newer variants