Human Impact on Zoonoses

Question 1

How does deforestation affect mosquitoes? Use examples.

Answer 1

• ·Plasmodium knowlesi: deforestation positively associated with infection rates –> more shallow pools in your backyard
• Anophelese gambiae larvae prefer well lit pools (more sunlight –> warmer –> reproduce at a higher rate)
• Anophelese durlingi have been found to bite 287X more in deforested areas (more mosquitoes present)

Question 2

Does zoonoses affect deforestation?

Answer 2

In the amazon a 1% increase in malaria incidence was correlated with a 1.4% decrease in cleared forest area (nature fighting back)

Question 3

How does deforestation affect wildlife?

Answer 3

puts wildlife in closer proximity with humans and mosquitos

Question 4

Describe the transmission cycle of hantavirus? Include hosts and mode of transmission

Answer 4

1. chronically infected rodent
2. horizontal transmission of infection between rodents
3. virus is present in aersolized excreta, particulary urine
4. human infection by inhalation of aersolized rodent excreta
5. human to human transmission is not possible

Question 5

What causes hemorrhagic fever with renal syndrome? What are some symptoms? What is the treatment?

Answer 5

• caused by hantavirus
• symptoms: headache, back and abdominal pain, fever, chills, nausea, and blurred vision
• treatment: supportive therapy (electrolytes, fluids, oxygen) and IV ribavarin

Question 6

Describe the trend that occured in china between urbanization and hantavirus infections. Why?

Answer 6

• inital urbanization –> lots of cases (lots of people living together + inadequate infrastructure)
• further urbanization –> fewer cases (better infrastructure that reduced rodent exposure as cities develop)

Question 7

Describe how urbanization affects zoonoses?

Answer 7

• income inequality plays a role (e.g. access to clean water)
• urbanization results in proliferation of many types of animals from which zoonotic diseases often emerge - birds, bats, and rodents (love living near humans)
• initial urbanization can result in more zoonotic spill over events - much to do with sanitary conditions
• more prosperity associated with urbanization helps alleviate some of the damage caused by zoonotic disease
• greater animal density can result in more pathogen diversity

Question 8

How did urbanization affect the parasitic load of macaques? Why?

Answer 8

urbanization increases parasite species in these monkeys

from eating human garbage

Question 9

Describe three ways in which alterations in ecosystems can impact zoonotic disease transmission in several ways

Answer 9

1. altered suitability for reservoir hosts
2. altered suitability for disease vectors
3. increased or decreased contact with humans

Question 10

Rank the following bodies of water in terms of area suitable for mosquitos in most to least suitable: 1km river, 100 x 100m lake, 100 x 100 rice paddy

Answer 10

rice paddy > lake > river

Question 11

Does the dilution effect or diversity begets pathogen diversity hypothesis apply better to specialist pathogens? Generalists? Why?

Answer 11

• specialists: the dilution effect –> if their host diversity decreases then they have fewer options
• generalists: diversity begets pathogen diversity –> not affected as much from biodiversity loss

Question 12

Describe how biodiversity loss of birds affected WNV transmission? Does this support the dilution effect or diversity begets pathogen diversity hypothesis?

Answer 12

more bird diversity –> less WNV infections

supports the diltution effect hypothesis

Question 13

Describe how habitiat size affects vertebrate diversity, and conversely how biodiversity loss affects the amount of LD found in ticks, and LD transmission to humans? Does this support the dilution effect or diversity begets pathogen diversity hypothesis?

Answer 13

smaller habitats tend to have less vertebrate diversity, less diversity –> more infected ticks, rodents (the reservoir for LD) live closer to humans –> more LD transmission to humans

supports the dilution effect

Question 14

Describe the pathogen that causes Q fever: type of pathogen, species name, intracellular vs extracellular

Answer 14

• bacteria
• Coxiella burnetti
• obligate intracellular parasite

Question 15

What are the two variants of C burnetti? Describe each one

Answer 15

1. SCV - small cell variant: sporelike, survives well in the environment, passively enters phagosome and blocks its fusion with lysosomes
2. LCV - large cell variant: arises from SCV in phagosome, multiplies inside macrophages

Question 16

Describe entry of C burnetti into macrophages

Answer 16

1. binds to integrins
2. phagocytosis in actin-dependent matter
3. blocks fussion with lysosome
4. acidification of phagosome
5. decreases the presence of cathepsins
6. induces expansion of the phagolysosome

Question 17

What are two common sources for Q fever outbreaks?

Answer 17

abattoirs and wool-processing plants

Question 18

How does testosterone affect the immune system?

Answer 18

immunosuppressive: energy expenditure on getting bigger and reproducing –> less energy on IS

Question 19

Describe chronic Q fever

Answer 19

• infection that persists for > 6 months
• more serious disease
• manifests as endocarditis
• incubation period depends on the number of organisms that infect the patients

Question 20

Describe the diagnostics, treatment, and control of Q fever

Answer 20

• treatment: doxycycline (inhibits 30S ribosome) and hydroxychloroquine (acidifies phagolysosome)
• diagnostics: detect serum Ab using ELISA, PCR
• control: vaccines available for high risk occupation groups, bury placenta from sheep/goats

Question 21

What was the seasonality trend of Q fever infections that occured in the Netherlands? Why?

Answer 21

trend: increase incidence during birthing season

closer proximity to goats and sheep giving birth

Question 22

Why is it important to monitor zoo and farm animals for diseases?

Answer 22

helps predict outbreaks

Question 23

What gene is responsible for conferring resistance to common antibiotics, such as penicillin?

Answer 23

extended-spectrum B-lactamase genes

Question 24

What is the reservoir host for ebola?

Answer 24

bats

Question 25

What mistake did the Dutch make when trying to control Q fever during the outbreak?

Answer 25

didn’t implement stricter policies fast enough

Question 26

Describe the human behaviours that contributed to the spread of ebola

Answer 26

1. traditional funeral practices
2. unprotected healthcare workers
3. unprotected contact with blood and body bluids

Question 27

Briefly describe how ebola enters cells (also what cells does it infect?)

Answer 27

1. taken up by micropinocytosis
2. glycoproteins removed by cathepsins
3. co-opts NPC1 to facilitate release of genetic material

infects: monocytes, MFs, DCs, endothelial cells, fibroblasts, hepatocytes, adrenal cortex cells, and epithelial cells

Question 28

How does ebola cause pathology?

Answer 28

trigger release of pro-inflammatory cytokines with subsequent vascular leak and impairment of clotting, ultimately resulting in multi organ failure or shock…usually in the spleen, liver, adrenal gland

Question 29

Describe the treatment and prevention of ebola

Answer 29

• treatment: inmazeb and ebanga (mAbs), vaccine
• prevention: proper burial of bodies, PPE for healthcare workers, burning of bedding/clothing

Question 30

Give two reasons why bats harbour so many zoonotic diseases

Answer 30

1. bats constituvely express type 1 IFNs and their associated proteins, humans do not have similar basal levels
2. bats have a greater Ig repertoire: greater repertoire of heavy chain combinations –> don’t require affinity maturation?