Intro to Zoonotic Disease

Question 1

What is zoonoses?

Answer 1

any disease or infection that is natrually transmissible from nonhuman vertebrates to humans or vice-versa

Question 2

What is zooanthroponosis? Give three examples

Answer 2

human to animal transmission
e.g. amebiasis to dogs, TB, ascaris

Question 3

What is anthrozoonosis? Give three examples

Answer 3

animal to human transmission
e.g. rabies, brucellosis, ascaris

Question 4

What are three methods of transmision of zoonotic diseases?

Answer 4

1. direct contact (animals-animals; animals-humans)
2. environmental transmission (contaminated food and water)
3. vectors

Question 5

What is pathogenicity?

Answer 5

very binary term - ability of an organism to cause disease

Question 6

What is infectivity?

Answer 6

The likelihood that an agent will infect a host, given that the host is exposed to the agent

Question 7

What is virulence?

Answer 7

Degree of disesase caused - depends on host-pathogen interactions

Question 8

What is an epidemic?

Answer 8

a widespread outbreak of an infectious disease; many poeple are infected at the same time

Question 9

What are 5 features of a pandemic?

Answer 9

A large epidemic with:

• wide geographical extension
• significant transmission –> disease movement and extension of geographic range
• highly contagious and short incubation times –> increased attack rate and explosive spread of symptomatic disease
• minimal population immunity –> disease spread
• often severe (fatal)

Question 10

Describe herd immunity

Answer 10

• vaccination/natural immunity of a portion of the population (or herd) provides protection to unvax/non-immune individuals
• the more immune individuals present in a population the less likely that a susceptible person will come into contact with an infected individual

Question 11

What is a host?

Answer 11

organism that harbors a pathogen

Question 12

What is a primary host?

Answer 12

critical to the life cycle of the pathogen

Question 13

What is a dead end host?

Answer 13

pathogen cannot be transmitted from this host

Question 14

What is a reservoir? What is the significance of reservoirs? What do reservoirs differ from?

Answer 14

• animals or inanimate sources harboring disease-causing organisms
• serve as potential sources of disease outbreaks
• differ from carries, amplifiers (agents of disease transmission)

Question 15

What is a vector?

Answer 15

an orgnaisms, often an invertebrate arthropod, that transmits a pathogen from reservoir –> host

Question 16

What is morbidity?

Answer 16

illness/clinical disease

Question 17

What is mortality?

Answer 17

Death

Question 18

What is prevelance?

Answer 18

total number of cases of the disease in the population at a given time

Question 19

What is incidence? How do you calculate it?

Answer 19

a measure of the risk of developing some new condition within a specified period of time
incidence = (new cases)/(population x time-frame)

Question 20

What is the species barrier effect ?

Answer 20

Barrier between two different species

Question 21

What is a complete barrier?

Answer 21

no transmission

Question 22

What is a partial barrier?

Answer 22

transmission after long period of time or transmission in the absence of disease

Question 23

What is adaptation/selection?

Answer 23

the ability of an agent to “evolve” in a new host

Question 24

What are serial passages?

Answer 24

pathogen modified during passage to adapt to new hosts

Question 25

What are some old vs new zoontotic diseases?

Answer 25

old = malaria, HIV-1 new = ebola, MERS, influenza strains, zika, COVID-19

Question 26

Describe the 5 different stages of zoonotic diseases and give an example for each stage

Answer 26

1. the pathogen is present in animals, but it doesn't infect humans under natural conditions (e.g. feline distemper) 2. the pathogen can be transmitted from animals --> humans, but cannot spread human --> human (e.g. Nipha virus) 3. the pathogen can be transmitted from animals --> humans and can pass between humans; however, the pathgoen is not well adapted to human and the pathogen will die out after a few cycles of transmission (e.g. ebola virus) 4. the pathogen can be transmitted from animals to humans and can pass between humans; it can adapt to living in humans for long periods of time without going back to animal hosts (e.g. cholera) 5. a pathogen exclusively infects humans; the pathogen may have co-evolved with humans or colonized humans recently and evolved into a specialized human pathogen (e.g. HIV)

Question 27

What are three modes in which an infectious disease can be defined as "emerging"? Give an example for each mode

Answer 27

1. a new agents appears in a new geographic area (e.g. avian influenza, HIV-1, SARS, H1N1) 2. a known agent or its close relative affects a new host species (e.g. MRSA, TB, chloroquine resistant malaria, HIV-1, SARS) 3. a known pathogen that increases incidence (e.g. lyme disease)

Question 28

What is an endemic zoonotic? What are they often? Why do they become endemic?

Answer 28

* present in a population for centuries to millennia * often neglected diseases * occasionally occur as epidemics * become endemic/chronic due to societal effects

Question 29

# Bioterrorism Define Class A (highest risk) agents/characteristics, give examples

Answer 29

* can easily be disseminated or transmitted from person --> person * result in high mortality rates and have the potential for major public health impacts * might cause public panic and social disruption * require special action for public health preparedness * e.g. anthrax, botulism, plague, tularemia, ebola

Question 30

# Bioterrorism Define Class B (moderate risk) agents/characteristics, give examples

Answer 30

* moderately easy to disseminate * result in moderate morbidity rates and lower mortality rates * require specific enhancements of CDC's diagnostic capacity and enhanced disease surveillance * e.g. salmonella, camplyobacter, pathogenic E coli, WNV, brucella, giardia

Question 31

Give a few examples of infectious disease that cause chronic illness

Answer 31

* h pylori --> peptic ulcers and cancer * HPV --> cervical cancer * M. pneumoniae --> chronic asthma

Question 32

What are 5 factors that affect disease transmission

Answer 32

* disease agent * vertebrate hosts * vectors * environment * climate change

Question 33

Why are birds and bats good vertebrate hosts for diseases?

Answer 33

they are quite mobile, live around humans, and there are lots of species

Question 34

How can serological tests help determine a diseases reservoir host?

Answer 34

If Abs against the agent are present, then this can implicate them as the reservoir, but could be an intermediate

Question 35

What is the dilution effect?

Answer 35

Normal conditions: high biodiversity, fewer reservoirs in a community --> fewer infected vectors --> fewer human infections Dilution: low biodiversity, more reservoirs in a community --> more infected vectors --> more human infections

Question 36

What are three sources of human exposure to zoonotic diseases?

Answer 36

1. movement of animals 2. ecological disruption 3. bioterrorism

Question 37

How is animal movement a source of human exposure to zoonotic diseases?

Answer 37

* livestock and poultry - high quantities of meat/products move between countries * exotic animals - pet trade, reptiles, zoo animals, wildlife

Question 38

How is ecological disruption a source of human exposure to zoonotic diseases?

Answer 38

humans encroaching on a new habitat

Question 39

Why are some disease under-diagnosed?

Answer 39

* pockets of infection * shared symptoms * diagnosis is complex or lack of inexpensive diagnostic tests * education of pts, MDs, vets

Question 40

Why are impovrished people more likely to contract a zoonotic disease?

Answer 40

* occupational * food safety

Question 41

What are 3 ways to surveil zoonotic diseases?

Answer 41

1. molecular biology tools - PCR and rapid genome sequencing 2. one health - doctors and vets 3. international monitoring