The Role of Wildlife in Zoonotic Outbreaks

Question 0

What was the link between animals and HIV outbreak?

Answer 0

Started in chimpanzees which were hunted by people for years without any outbreak, few isolate diseased individuals but no explosion
1920s = first time HIV spread through the population
1980s = first time AIDS was noticed

Question 1

Which species did Ebola originate in?

Answer 1

Fruit bats carry virus asymptomatically

Question 2

What HIV control programme might have spread the disease further?

Answer 2

Vaccination program that didn’t use proper sterilisation methods

Question 3

How many people have been infected with HIV? How many people have died of HIV?

Answer 3

75 million people infected with the virus

36 million people have died of HIV

Question 4

What is a spillover event?

Answer 4

When disease jumps from wildlife to humans

Question 5

Why should pathogens in wildlife concern you?

Answer 5

Transmission to humans has an impact on human health
Transmission to domestic animals
Cost of control
Conservation
Legal obligations
Unpredictability of emergence
Ability to move long distances

Question 6

What are some examples of zoonoses that originated in wildlife?

Answer 6

SARS (bats?)
MERS (camels,bats?)
Influenza (birds)
Rabies (bats, terrestrial carnivores)
Ebola (bats, others)
HIV (primates)
West Nile Virus (birds)
Nipah virus (bats)

Question 7

What is the most common tick-borne infectious disease in the UK, Europe and North America?

Answer 7

Lyme disease (Borrelia buurgdorferi)

Question 8

What was identified as the cause for increase in the USA?

Answer 8

At first was attributed to increase in deer population.
On further investigation was actually found to be due to reduction in number of small mammal predators so more mice were around for the tick larvae to attach to resulting in more surviving and so more Lyme disease

Question 9

Define spillover host

Answer 9

An animal in which infection is sporadic or can only persist if external sources of infection are present
Often domestic animals especially livestock/horses
Develop severe disease themselves and are capable of shedding virus in large quantities (amplifier hosts)
Pass infection to people

Question 10

Define maintenance hosts

Answer 10

An animal in which infection can persist via horizontal transmission in the absence of any other source of infection

Question 11

What are reservoir hosts?

Answer 11

Smallest number of animals needed to maintain infection and can be a mixture of species

Question 12

What is the general process of a spillover event?

Answer 12

Infection in wild animal population -> spillover host (amplifier) -> human infection -> fizzle out/pandemic

Question 13

What was the process of spillover for Hendra virus?

Answer 13

Hendra virus was first identified in fruit bats endemically and asymptomatically (took a long time to identify)
Horses were the spillover host
Horses infected people resulting in a pandemic

Question 14

What was the spillover event for avian influenza?

Answer 14

Avian influenza virus present in wild birds endemically and asymptomatically
Poultry were the spillover host
Poultry infected people and it became a pandemic before fizzling out

Question 15

What was the spillover event for Nipah virus?

Answer 15

Nipah virus found endemically and asymptomatically in fruit bats
Pigs were the spillover host
Humans were infected from the pigs resulting in a pandemic

Question 16

How did fruit bats infect pigs with Nipah virus?

Answer 16

Deforestation for pig farms -> fruit bats on outskirts would fly over pig pens and drop fruit and faeces/urine which the pigs would eat and become infected

Question 17

How was Nipah virus transmission to people more complicated than it first seemed?

Answer 17

Bats also found to urinate into cups collecting palm sap for local alcohol production which was also found to infect people

Question 18

What are the clinical signs of Nipah virus in people?

Answer 18

Encephalitis, fever, vomiting, coma and respiratory issues