Questions and Answers
Which of the following are zoonotic diseases? (Select all that apply)
What is zoonosis?
Diseases that transfer from animals to humans.
What are the three categories of zoonotic diseases?
Spillover, emerging, and re-emerging.
Why was eliminating or eradicating polio and smallpox easier than Lyme disease and AIDS?
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What is a reservoir host?
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Which disease spilled over in Australia in 1994?
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Hendra was caused by which type of virus?
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What is the case fatality rate for humans infected with Hendra?
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How is Hendra transmitted to humans?
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What type of exposure leads to transmission of Hendra to horses?
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How many horses were infected with Hendra from 1994 to 2016?
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What supportive treatments are being developed for humans infected with Hendra?
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Of bat carers, how many people showed signs of Hendra exposure?
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What was the amplifying host for Hendra?
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What is foot and mouth disease?
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What proportion of zoonotic diseases originate in wildlife?
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What is bushmeat?
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Which of the following are major emerging infectious diseases?
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Study Notes
Zoonotic Diseases
- Zoonotic diseases include swine flu, bird flu, SARS, AIDS, yellow fever, dengue, ebola, and plague.
- These diseases transfer from animals to humans, posing significant health risks.
Zoonosis
- Zoonosis is the term for diseases that transfer from animals to humans.
- Since 1981, zoonotic diseases have resulted in approximately 30 million deaths.
- Hundreds of millions of deaths have been attributed to zoonotic diseases since the 20th century.
Categories of Zoonotic Disease
- Spillover: A new zoonotic infection emerging from animal hosts.
- Emerging: A surge of new disease cases in a new population.
- Re-emerging: Increasing cases of disease in previously affected populations.
Challenges in Disease Eradication
- Polio and smallpox elimination was easier due to the lack of zoonotic transmission.
- Lyme disease and AIDS lack vaccines, complicating eradication efforts.
Reservoir Host
- A reservoir host is a species where a pathogen can live and multiply without causing significant harm.
- Reservoir hosts are crucial for the survival of various pathogens.
Hendra Virus
- First identified in Australia in 1994 as Hendra virus, formerly known as equine morbillivirus.
- Caused by the paramyxoviridae Henipavirus family.
Hendra Infection Statistics
- Between 1994-2016, around 70 horses were infected, primarily in Queensland and New South Wales.
- Approximately 7 humans were infected with a 57% case fatality rate, experiencing flu-like symptoms and respiratory issues.
- The incubation period for Hendra virus ranged from 9 to 16 days.
Transmission
- Hendra virus is transmitted to humans through exposure to infected horse fluids.
- No known human-to-human transmission has occurred.
- Horses acquire the virus from contact with infected flying foxes' urine, which acts as a natural host.
Dogs and Hendra
- A dog tested seropositive for Hendra in 2013 but showed no significant symptoms.
- Horses are considered the amplifying hosts.
Disease Spectrum
- The progression of zoonotic diseases includes exposure, infection, pathogenicity, serious disease, and mortality.
Infectivity and Mortality
- Infectivity measures a microorganism’s ability to infect hosts.
- Mortality is assessed based on the number of deaths in relation to exposed individuals.
Serious Disease and Mortality Causes
- Both race horses and humans experience significant disease and mortality from Hendra infection.
Flying Foxes and Hendra Outbreaks
- Flying foxes were expected to be the reservoir due to their presence in outbreak areas and large group migrations.
Treatment and Prevention for Humans
- Supportive treatment is offered, while research is ongoing for passive immunity treatments.
- Preventive measures include vaccinations for horses and early recognition of the disease, especially for veterinarians.
Infection Rates Among Bats and Carers
- Zero bat carers showed signs of Hendra exposure, while 50% of bats assessed showed signs of infection.
Amplifying Hosts
- Horses serve as the amplifying hosts for the Hendra virus.
- Pigs are identified as amplifying hosts for foot and mouth disease.
Foot and Mouth Disease Insights
- Sheep act as asymptomatic carriers; pigs amplify the virus, while cows experience the largest pathogenic effects.
- A single outbreak of foot and mouth disease could cost the U.S. economy $27 billion in a year.
Hendra as an Emerging Infectious Disease
- Initially viewed as a spillover incident, Hendra virus is now recognized as an emerging infectious disease due to increased cases.
Historical Emerging Infectious Diseases
- Notable recent emerging diseases include HIV/AIDS, Ebola, and Zika.
- The Spanish flu pandemic of 1918/1919 caused around 50 million deaths, believed to have originated from ducks.
Zoonotic Disease Statistics
- Zoonotic diseases make up about 60% of infectious diseases in humans.
- 75% of emerging or re-emerging infectious diseases are zoonotic in nature.
Future Epidemic Concerns
- The next major infectious disease epidemic is likely to originate from wildlife, with 70% of zoonotic diseases emerging from wild sources.
- Bushmeat is a common term for meat sourced from wild animals, relevant to zoonotic disease spread.
Ebola and Its Links
- Ebola outbreaks are closely associated with bushmeat consumption and wildlife contact.
Studying That Suits You
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Description
Test your knowledge on zoonotic diseases with this quiz based on Chapter 1 of Spillover. Explore key terms and their definitions related to the transmission of diseases from animals to humans. Perfect for students and anyone interested in epidemiology.
