Lecture 7: Emerging and re-emerging bacterial disease

Question 1

What is an emerging disease?

Answer 1

“An emerging disease is one that has appeared in a population for the first time, or that may have existed previously but is rapidly increasing in incidence or geographic range.” (WHO, 2015)

Question 2

What type of factors are attributed to the emergence of infectious disease?

Answer 2

• Human activity and habitat encroachment
• Environmental change (human drivers)
• Microbe change (human drivers)

Question 3

What is a re-emerging disease?

Answer 3

“A re-emerging infectious disease is a disease whose incidence has increased in a defined time period and location” [after a significant period of decline].

Question 4

What disease was re-emerging and on the increase up tp 2012?

Answer 4

Tuberculosis

Question 5

What is a Multidrug-resistant (MDR) pathogen?

Answer 5

resistant to three or more classes of antibiotics

Question 6

What is an Extensively drug-resistant (XDR) pathogen?

Answer 6

esistant to at least one agent in all but one or two antimicrobial classes.

Question 7

What is NOT a re-emerging disease?

Answer 7

an outbreak or seasonal variation. e.g when there are peaks in flu cases in the winter months. A re-emerging disease has to be sustained.

Question 8

Define Transmission

Answer 8

The mechanism in which a disease is spread i.e. faeco-oral, vector borne, etc.

Question 9

Define Incubation period

Answer 9

The time between infection and symptom onset.

Question 10

Define carrier

Answer 10

A person or animal without apparent disease who harbours a specific infectious agent and is capable of transmitting it to others.

Question 11

Define Infectivity

Answer 11

The proportion of persons exposed to a causative agent who become infected by an infectious disease.

Question 12

Define reservoir

Answer 12

The habitat in which an infectious agent normally lives, grows and multiplies; can include human reservoirs, animals reservoirs, and environmental reservoirs.

Question 13

Define zoonoses

Answer 13

An infectious disease that is transmissible from animals to humans.

Question 14

Define endemic

Answer 14

A disease which is constantly present in a population or geographical area.

Question 15

Define Epidemic

Answer 15

The occurrence of more cases of disease than expected in a given area or population over a particular period of time.

Question 16

Define Pandemic

Answer 16

Worldwide epidemic, affecting a large, widespread population simultaneously

Question 17

Is lyme disease an example of an emerging infectious disease?

Answer 17

Yes

Question 18

WHat family does lyme disease belong to ?

Answer 18

Spirochaetaceae

Question 19

What species does lyme disease belong to?

Answer 19

Borrelia burgdorferi

Question 20

What is the structure of the lyme disease bacteria?

Answer 20

spirochete (coiled, double membrane)

Question 21

What is the growth of lyme disease?

Answer 21

microaerophilic

Question 22

How is lyme disease transmitted?

Answer 22

vector borne transmission (black legged tick) with a zoonotic reservoir.

Question 23

What are the virulence factors of lyme disease?

Answer 23

flagella;

motile;

exploiting immune system;

OspC lipoprotein expression.

Question 24

What is the danger risk of lyme disease?

Answer 24

Danger: High – debilitating life-long disease.

Question 25

Describe the pathogenesis of lyme disease

Answer 25

- Erythema Migrans (EM) rash - Arthritis - Facial palsy - Radiculoneuropathy - Meningitis - Carditis

Question 26

Is it true that B. burgdorferi enters vertebrate host epithelium & migrates into tissue & joints ?

Answer 26

Yes

Question 27

How does B. burgdorferi attach to the tick?

Answer 27

By expressing Outer surface Protein A (OspA)

Question 28

Describe the 3 host tick cycle of lyme disease Check facts!

Answer 28

- Tick's go through Malt stages and as they grow, they change the type of animals that they feed on. - When they'e adults, they continue to feed on larger vertebrates and lay eggs that will last over the winter. - They will then feed on smaller vertebrates, who will pick up the infection again.

Question 29

Is it hard to remove the lyme ticks once bitten?

Answer 29

Yes, as they bite and then remain stuck in place in situ

Question 30

Is there a human vaccine for lyme disease?

Answer 30

No

Question 31

How can people reduce their exposure to tick bites?

Answer 31

- Personal protection - deer and land management - acaricides - education

Question 32

What can lyme disease be treated with if caught early?

Answer 32

doxycycline

Question 33

At wha ttime of the year are there the most cases of lyme disease?

Answer 33

The summer, when people typically go on long tick-infested walks

Question 34

What type of people are at a higher risk of contracting lyme disease?

Answer 34

The young, the elderly, men

Question 35

Are TB and HIV co-infections?

Answer 35

Yes, and they're prevalence has been increasing simultaneously

Question 36

What is the causative agent of cholera?

Answer 36

Vibrio cholerae O1 or O139 toxigenic strains.

Question 37

What are the characteristics of cholera?

Answer 37

Gram negative, facultative anaerobe, comma shaped rod, flagellated.

Question 38

How is cholera transmitted?

Answer 38

faeco-oral from contaminated water (or food).

Question 39

What are the virulence factors of cholera?

Answer 39

cholera enterotoxin; adherence factors (Hemagglutinins)

Question 40

What is the danger of cholera?

Answer 40

Danger: Very high – highly contagious, extreme dehydration within hours if untreated.

Question 41

is cholera an emerging or a re-emerging disease?

Answer 41

Re-emerging

Question 42

How does the cholera endotoxin cause sudden and dramatic ‘rice water’ diarrhoea?

Answer 42

- Cholera toxin causes Cl- ions to be excreted from cells of the intestine and reduces the re-absorption of NaCl - Osmotic pressure draws water into the lumen of the gut which manifests as watery diarrhoea

Question 43

What results in death from cholera?

Answer 43

Death can occur due to excretion of 0.5 to 1l/h of diarrhoea, leading rapidly to tachycardia, hypotension, and vascular collapse due to dehydration.

Question 44

Is it true that cholera is endemic in many countries?

Answer 44

Yes

Question 45

How many global pandemics did cholera lead to?

Answer 45

Led to 6 global pandemics, killing millions.

Question 46

How many cases of cholera are there annually worldwide?

Answer 46

1.3-4.0 million cases annually worldwide (but only 140,000 reported).

Question 47

What can high cholera cases in a particular area be an indicator of?

Answer 47

Can be an indicator of lack of socio-eco development and sanitation.

Question 48

What is the reemergence of cholera linked to ?

Answer 48

Re-emergence linked to increasing size of vulnerable populations living in unsanitary conditions (Displaced persons ; Infrastructure breakdown)

Question 49

What can help to prevent cholera?

Answer 49

Safe water and sanitation, and the cholera vaccine

Question 50

What can be used to treat cholera once it's contracted?

Answer 50

- Rehydration therapy (Oral or intravenous; salts and mineral replacement). - Antibiotic treatment - Zinc treatment -

Question 51

Are surveillance and rapid responses to outbreaks required to prevent the mass transmission of cholera?

Answer 51

Yes

Question 52

Does the world health organisation give out cholera outbreak response kits?

Answer 52

Yes

Question 53

Describe the Haiti cholera epidemic of 2010

Answer 53

- Case fatality rate = ~5%, which is high for a preventable and treatable disease. - Had an earthquake and response team from Nepal spread cholera to Haiti. - Impacts of the disease weer worsened by the fact that the earthquake had disrupted and weakened the healthcare system.

Question 54

Is shigella an emerging or reemerging disease?

Answer 54

Shigella is a re-emerging disease

Question 55

What family does shigella come from?

Answer 55

Family: Enterobacteriaceae

Question 56

What are the characteristics of shigella?

Answer 56

Gram negative, facultative anaerobe, non-motile.

Question 57

How can shigella be transmitted?

Answer 57

faeco-oral, (sexually transmitted).

Question 58

What are the virulence factors of shigella?

Answer 58

invasion of epithelial cells, shiga (vero) toxin production.

Question 59

What is the danger level of shigella?

Answer 59

Danger: Moderate – self limiting infection in most cases, life threatening for vulnerable (young, old, immunocompromised).

Question 60

Is shigella an invasive intestinal infection that induces a mass inflammatory response ?

Answer 60

Yes

Question 61

What types of inflammatory responses are induced by shigella?

Answer 61

watery or bloody diarrhoea

Question 62

What type of person does shigella mostly target?

Answer 62

Children

Question 63

How many deaths does shigella cause annually?

Answer 63

Causes 200,000 deaths annually.

Question 64

Shigella may be caused by any of the 4 Shigella species, which are....

Answer 64

S. dysenteriae, S. boydii, S. sonnei and S. flexneri.

Question 65

Why is shigella difficult to treat with antibiotics?

Answer 65

Because all the species are highly multi-drug resistant, most recently to ciprofloxacin