5 - Important Zoonotic Diseases Flashcards
WHO’s definition of a zoonosis
an infectious disease that has jumped from a non-human animal to humans. The pathogen may be bacterial, viral or parasitic, or may involve unconventional agents and can spread to humans through direct contact or through food, water or the environment.
How many organisms are known to be pathogenic to humans? How many are zoonotic? Emerging?
1415 known
868 (61%) zoonotic
175 emerging
Stages of a zoonosis
Stage 1: agent only in animals
Stage 2: primary infection
Stage 3: limited outbreak
Stage 4: long outbreak
Stage 5: exclusive human agent
Slide 4** examples
Examples of important human diseases that no longer require animal reservoirs
- measles (Cattle)
- dengue (Monkeys)
- malaria (Gorillas)
- HIV (Chimps)
HIV-1 origin story
Comes from cross species transmission of related Simian Immunodeficiency viruses (SIVs) which are nonpathogenic in their natural hosts (chimps)
Transmission likely through bushmeat hunting
Lineages of HIV and which is most important
Groups M, N, O, P
HIV-M from SIVcpz in SE Cameroon: worldwide spread
HIV-M origin story
Emerged in Kinshasa
Infected blood/tissue of the residents dated back to 1959
Connects to SE Cameroon by river; likely went downriver
Yellow fever origin, reservoir and how it got to the new world
Africa, Monkeys
Slave trade caused dissemination of its primary vector, Aedes aegypti, into the new world
Describe yellow fever in the USA
150 000 people died
New York (1668), Boston (1691), Philly (1793)
How did Yellow fever impact the first world war?
Critical role in haitian independence, 2/3 mortality among 40,000 Napolean’s army
What is interesting about yellow fever in Brazil?
Not a typical urban outbreak (not Ae aegypti vectored): was in non-human primates and spilt over into humans living at edge of forest
Types of influenza, their differences
A: most severe human infection, is the type that is zoonotic
B and C: restricted to humans
How does influenza undergo genetic change?
Mutation and gene reassortment affecting the ability to attach to mucosa of specific species
The rapid genetic change in influenza results in…
- antigenic drift (minor genetic change)
- and antigenic shift (emergence of a very different virus)
How do birds affect influenza
Shorebirds are a key reservoir for influenza viruses
Migration flyways pass through densely populated human areas
They stopover and defecate, infect ducts/other waterfowl, which affect mammals which affect humans
Slide 15
Different cases of pandemic influenza
- H1N1 Spanish influenza in 1918 (direct from avian host)
- H1N1 Swine influenza in 2009 (viral reassortment in pigs)
MERS CoV stands for… Its host? Mortality? Outbreak?
Middle Eastern Respiratory Syndrome Coronavirus
Dromedary camels primary animal host
Outbreak in Saudi Arabia in 2012
35% mortality
Transmission of SARS-CoV-2
Can be infectious before symptoms are present
By air: large droplets 1-2meters
Fomites: contaminated inanimate objects?
Two steps in new SARS-CoV-2 variants
1: Mutation (highly mutable RNA virus)
2: Natural selection, mainly in favour of spike proteins that are more transmissible (more infectious virus outcompetes earlier strain)
Why is there potential for emergence of new coronaviruses from animals?
- 9% of bats from Asia, Africa, Latin America carry at least one coronavirus
- genetic recombination
Effects of West Nile Virus on humans
80% asymptomatic
20% West Nile Fever
<1% neuroinvasive disease
Vector and host of WNV. Describe them
Mosquito vector
Birds are amplifying hosts (jays, crows; minimal clinical infectious, high viremia)
Many vertebrates (including humans) are dead end hosts (low viremia; do not infect mosquitoes)
Where did WNV emerge? In the western hemisphere?
Uganda 1937
WH 1999 (NYC) through migratory birds and mosquitoes
Describe WNV in New York
Human encephalitis outbreak
High number of dead crows
Exotic birds at Bronx zoo developed encephalitis, vets identified WNV
