15: Zoonosis

Question 1

zoonoses definition (WHO)

Answer 1

infectious diseases that are transmissible from vertebrate animals to humans under natural conditions

Question 2

zoonotic spillover definition

Answer 2

event in which a pathogen jumps from animal to human
- virus/bacteria/fungi/pathogens going from one host to another

reverse zoonosis when viruses and pathogens go from humans to animals

Question 3

zoonoses as a major public health problem worldwide

Answer 3

6 out of 10 infectious diseases in people spread from animals
- huge impact on public health

3 out of every 4 new or emerging infectious diseases in people are spread from animals

significant morbidity and morality

adverse impact on regional economies

Question 4

zoonoses as a major economic problem worldwide

Answer 4

direct cost of zoonotic diseases over the last decade estimated to be more than $20B

over $200B indirect losses to affected economies as a whole

Question 5

what can zoonotic pathogens do?

Answer 5

be stably established in animal populations and transmit from animals to people with little or no subsequent person-person transmission
- endemic or sporadic emergence of the pathogen into the population

be spread efficiently between people once introduced from an animal reservoir, leading to localised outbreaks or global spread

Question 6

epidemic vs pandemic

Answer 6

epidemic: pathogen can replicate in a new host and transmit
- risk that with globalisation and higher population densities, diseases will infect more people

pandemic: epidemic which evolves into something disseminated worldwide

Question 7

range of disease pathogens which can cause zoonoses

Answer 7

viruses
bacteria
parasites
fungi
prions

Question 8

routes of transmission

Answer 8

fecal/oral (e.g. giardia)
inhalation (e.g. coronaviruses)
vector transmission (e.g. west nile virus with mosquitos/ticks)
penetrating wounds (e.g. rabies)
contact with body fluids (e.g. nipah virus)

Question 9

example of reverse zoonosis

Answer 9

pig as a mixing vessel for influenza A viruses

flu typically resides in birds, which infects pigs and humans

flu from birds and humans can infect the same pigs, and then potentially reassort

increased transmission back to humans with reasserted viruses because of pig infections

Question 10

why did we have more zoonotic events in the last few years?

Answer 10

multiple events with global changes which lead to disturbance of the natural habitat and increased contact between animal wildlife and humans

population growth
- virus entering the population can interact with more people and have more transmission effects
- increased probability of interaction with nature

industrialisation/mining which destroys natural habitats of animals which are now displaced and enter new ground where humans live or go
- e.g. ebola where vectors are being displaced and bringing it closer to the human population

Question 11

ebola virus disease outbreaks in 2013

Answer 11

linked with mining industries and the recent loss of forests

Question 12

lyme disease and projected changes in tick habitat

Answer 12

borrelia transmitted by ticks, who bite rodents and deer in the wild, transmitting the disease

prediction with global warming
- winter is less severe
- ticks survive better
- population of ticks increase
- increased density of the population

prevalence of lyme disease increasing in the US as a result of global warming

Question 13

health challenge and the solution

Answer 13

idea that you can’t just consider one thing but animal/environmental/human health as the entire solution

have to take a global approach