one health Flashcards
1
Q
concepts and principles of one health
A
2
Q
what is one health?
A
a multi-sectoral approach that aims to improve the health of people, plants, and the environment.
-recognises that the health of these different components is closely linked and interdependent
an integrated, unifying approach that aims to sustainable balance and optimise the health of people, animals and ecosystems. It recognises the health of humans, domestic and wild animals, plants and the wider environment (including ecosystems) are closely linked and inter-dependent. The approach mobilises multiple sectors, disciplines and communities at varying levels of society to work together to foster well-being and tackle threats to health and ecosystems, whyle adressing the collective need for clean water, energy and air, safe and nutritious food, taking action on slimate change and contributing to sustanable development.
3
Q
what are specific examples of the application of one health approaches
A
4
Q
what are the opportunities and challenges in one health?
A
5
Q
what approach do we need to move torwards for health?
A
ecological.
we need to move towards a more ecological approach to health.
6
Q
what term describes what often drives illness and poor health?
A
anthropogenic.
(originating in human activity)
although drivers of illness and poor health are often anthropogenic, our solutions should not be anthropocentric.
7
Q
what are examples of interfaces across which one health scopes?
A
> zoonoses
food systems, food security
international health and development
natural resources, biodiversity and conservation
antimicrobial resistance
environment, animals and mental health
human-animal bond
*zoonoses (pathogens transmitted animals to people), emerging infectious diseases; endemic zoonoses and neglected diseases
*food systems, food security (agricultiral production, land use, climate change, food safety)
*international health and development (sustainable development goals)
*natural resources, biodiversity and conservation (ecosystem health, water/soil quality, carbon dynamics
8
Q
what are the sustainable development goals (SDGs)? key areas?
A
UN 2030 agenda for sustainable development (adopted in 2015)
expanded the aims of the millennium development goals.
key areas:
1. food security
2. poverty alleviation
3. climate change
4. social justice
5. peace
6. environmental protection
7. health
9
Q
discuss food, health and the planet (regional realites).
A
per capita consumption of animal source foods has declined in sub-saharan africa over past few decades.
220 million in sub-saharan africa are under nourished
levels of stunting are high, often associated with low consumption of animal-source foods.
high intake of anumal source foods has been associated with improved gorwth, cognitive performance, motor development and increased activity in children.
10
Q
what is animal source food high consumption and low consumption associated with ?
A
low: stunting
high: improved growth, cognitive performance, motor development and increased activity in children
11
Q
discuss livestock in terms of food security and issues around livestock diseases
A
> over 1 billion people rely on livestock for food security and livelihoods
important for crop production (traction, manure), social capital and social protection
issues around livestock diseases:
- food security, food safety, malnutrition
- incomes, livelihoods, expenditure on health and education
- zoonotic disease problems
- unsupervised use of antimicrobials
- implications for land-use and rangeland health
- mental health problems
12
Q
how many people rely on livestock for food security and livelihoods?
A
over 1 billion people
13
Q
name three things which livestock are important for.
A
- crop production (traction, manure)
- social capital
- social protection
14
Q
what are 6 issues around livestock diseases?
A
- food security, food safety, malnutrition
- incomes, livelihoods, expenditure on health and education
- zoonotic disease problems
- unsupervised use of antimicrobials
- implication for land-use and rangeland health
- mental health problems
15
Q
what is an example of a livestock disease in Tanzania?
A
foot and mouth
16
Q
what is the momentum behind one health?
A
epidemics
17
Q
what are three key priorities of one health?
A
- origins of emerging diseases
- drivers of spillover and disease
- zoonotic disease surveillance
18
Q
describe some characteristics of emerging human and animal pathogens
A
61% of human pathogens and 75% of emerging human pathogens are ZOONOSES
viruses- particularly RNA viruses- are over-represented among human, livestock and domestic emerging diseases.
Generalist pathogens that can infect a wide range of host species are over-represented in human and livestock emerging diseases.
*wildlife represent important reservoirs of emerging pathogens
19
Q
what represent important reservoirs of emerging pathogens ?
A
wildlife
20
Q
what term is used to decribe a large percentage of human and emerging human pathogens?
A
zoonoses
*infections aquired from animals
21
Q
what are zoonoses?
A
infections acquired from animals
22
Q
what are over-represented in human, livestock and domestic carnivore emerging diseases?
A
viruses (particularly RNA viruses)
23
Q
what type of pathogens are over-represented in human and livestock emerging diseases?
A
generalist pathogens that can infect a range of host species
24
Q
RNA virus
A
characterised by a ribonucleic acid genome
25
discuss land-use change with examples
- numerous case studies show associations between land use and zoonotic disease risk
1. irrigation-based agriculture and Japanese encephalitis
2. deforestation and plasmodium knowlesi
3. agriculture practices and emergence of nipah visus
4. leptospira infections and rice fields
5. lyme disease and forest fragmentation
COVID-19; gowing global awareness of need for mechanisms and policies to mitigate the role of land use change in emerging disease risk
26
discuss nipah virus in terms of changing land-use
(human behaviour and virus emergence)
agricultural intensification of pig farms adjacent to bat-attracting mango plantations in Malaysia provided the conditions for Nipah virus emergence in pig populations after spillover from fruit bats.
27
who is burdened the most by endemic zoonotic diseases?
highest burden in poor and disadvantaged communities
livestock zoonoses often affect livestock health and productivity; impose a burden on livestock-dependent communities
28
what are the factors contributing to the 'invisibility' of endemic zoonoses?
lack of disease burden date
diagnostic challenges
- limited diagnostic capacity
- non-specific clinical signs
affect disadvantaged and neglected communities
- limited investment in prevention and control
29
epidemiology of human febrile illness in low and middle income countries
> fever is one of the most common symptoms among people in low and middle income countries
> management of disease represents a clinical challenge
> multiple causes (aetiologies) considerable local variation
30
what is a term for multiple causes of a disease/illness?
aetiologies
31
what are the benefits of interventions at source of one health? (targeting animals, protecting people)
1. reducing the disease burden in people and animals
2. preventative interventions at the animal source provide a broader 'safety net' than reliance on clinical management of human cases alone
3. necessary for elimination of infections involving animal reservoirs
32
what are examples of animal vaccines which are available?
brucellosis
Q fever
leptospirosis
Rift valley fever
toxoplasmosis
rabies
(interventions and tools exist for prevention and control of many zoonoses at source; many animal vaccines available ^^)
33
discuss rabies and rabies management
1. post-exposure prophylaxis (PEP) delivered as a medical intervention when people bitten
2. mass dog vaccination to prevent transmission from animal reservoirs
the disease is an acute progressive encephalomyelitis;
highest case fatality of any disease;
caused by viruses in the genus LYSSAVIRUS;
all mammals can be affected (>90% of human deaths are caused by domestic dogs usually through bite transmission)
*30 million people receive PEP /year ($1.7billion/year)
the most vunerable families face enormous challenges in accessing and affording PEP
as a result ~60,000 people die of rabies every year
34
what genus of viruses cause rabies?
lyssavirus
35
what disease has the highest case fatality?
rabies
36
how many people die of rabies a year and why?
~60,000 people/ year
the most vulnerable families face enormous challenges in accessing and affording PEP (30 million people receive PEP every year= $1.7 billion/year)
every hour more than 3,000 people in rabies-endemic countries are faced with life-threatening emergencies when bitten by dogs.
**there are great inequalities in access to life-saving PEP
37
where does rabies mostly affect?
primarily affects people in poor, rural communities in Asia and Africa.
*99% of human cases of rabies are from dog bites
38
what areas does human rabies only occur in?
human rabies only occurs in areas where dog vaccination coverage is low
39
what is given to people who have been bitten by a rabid dog?
post-exposure prophylaxis (PEP) delivered as a medical intervention when people bitten
40
what is a One Health approach to the prevention of rabies?
1. under status quo > 1 million human rabies deaths from 2020-2035 in 67 endemic countries
2. fewest deaths occurs when PEP access is improved alongside scaling up of dog vaccination
3. dog vaccination acts as a safety net to protect the most vulnerable
41
what does the united against rabies forum state?
' we have a bold vision; the global elimination of rabies by 2030. None of us can do it alone. But together we can make rabies history.'
42
discuss issues faced with investment in rabies prevention and allocation of resources across sectors.
the global vaccine alliance has approved investment in human vaccines
BUT parallel investments in mass dog vaccination prove to be challenging.
in africa and asia only 4-6% of funds for rabies control and prevention are allocated to dog vaccination
43
rabies vaccination vs polio vaccination
charging for interventions
both immunisations aim to protect childhood health and prevent deaths; childhood immunisation delivered free of charge; charging fees is only invoked for animal interventions
44
where do challenges to health, livetstock production and biodiversity arise from?
from growing pressures on land in the face of human population growth, climate change and economic development.
45
discuss Tanzania in terms of livestock-based livelihoods and optimising health, food security and biodiversity
Tanzania:
38% land comprises protected areas.
Tanzania has among the largest livestock populations in Africa.
A large proportion is dependent on livestock.
46
discuss MCF
malignant catarrhal fever.
A fatal viral disease of cattle transmitted from wildebeest. Transmission risk highest during wildebeest calving season. Up to now, no treatments or vaccines have been available. Prevention has relied on avoidance of high-quality grazing lands during wildebeest calving season.
47
when is the transmission risk of MCF highest?
malignant catarrhal fever; transmission risk highest during the wildebeest calving season
*prevention has relied on avoidance of high quality grazing lands during the wildebeest calving season
48
what are the consequences of avoiding MCF?
(malignant catarrhal fever)
1. 90% of cattle herds moved away from principal family residence.
2. 64% milk unavailable for sale or consumption (loss of up to 8% annual household income)
3. cattle re-gain body condition more slowly
49
what are the environmental consequences of poor livestock productivity? (*MCF)
1. conversion of rangeland to crop-based agriculture
2. mechanised agriculture associated with major declines in wildlife
3. wildebeest populations strongly declined when wheat cultivation expanded in the serengeti-mara ecosystem
50
discuss MCF vaccination (including pros and cons of vaccine)
(malignant catarrhal fever)
A new vaccine has been developed that provides partial protection against MCF.
(How are pastoralists in Tanzania likely to want to use the vaccine?)
what would the vaccine impact?
- food security and livelihoods
- cattle movements and management
- wildebeest movements
- pasture quality
potential benefits:
- improved pastoral livelihoods and nutrition (particularly children)
- reduced land use conflict
- counteracting sub-division of land
- maintaining ecological integrity of the ecosystem
potential problems:
- increasing livestock numbers resulting in land degradation
- increasing human-wildlife conflict
- negative impacts on the wildebeest migration
51
discuss some challenges in one health (5)
1. interdisciplinary and intersectoral challenges (different 'languages' issues of trust, control and influence
2. community engagement recognised as a priority but One Health still largely driven by 'top down' initiatives
3. challenges in funding for and implementation of preventive measures
4. large teams (costly, communication challenges, transaction costs)
5. professional recognition and career progression
52
what are three opportunities in one health?
1. recognition of the need for more integrated and ecological approaches to tackling global challenges including infectious diseases, epidemics, antimicrobial resistance, food security, environmental degradation.
2. ecologists and evolutionary biologists have critical expertise and are ideally placed to contribute to one health interdisciplinary teams.
3. funding available- but subject to change- currently targeted towards pandemic prevention and response, and antimicrobial resistance
53
what are some of the multiple benefits of pastoral livestock systems?
1. high levels of biodiversity at moderate livestock grazing intensity
2. mobile pastoral systems are a productive form of land-use in arid and semi-arid rangelands
3. pastoralism evolved in response to environmental uncertainty and climate variability
4. pastoral livestock systems can be carbon neutral
**but in many parts of the world pastoral systems are under threat
54
impacts of FMD in uganda
(food and mouth)
1. reduced household milk consumption
2. reduced income from sale of milk, poultry, eggs and bananas
55
hendra virus
- causes a fatal disease of horses and people
- virus transmitted from flying fox species
- habitat destruction = displacement of bats to new habitats in agriculture and urban areas
- winter food shortages = high levels of virus shedding from flying foxes; closer contact with horses
- increasing risk of spillover transmission
56
what is spillover transmission?
Viruses can occasionally, but quite rarely, move from one species to another. This is called a spillover event but can also be known as a spillover infection or a pathogen spillover.
57
understand how viral vaccines have been used to reduce diseases
58
understand the biological nature of currently licensed vaccines and how they are used
59
appreciate the approaches used to create vaccine candidates
60
what is a vaccine?
boost the immune system to protect against an infection
prophylactic vaccination
- prevention
- develop immunity in susceptible host
therapeutic vaccination
- post-exposure
- augments/accelerates immunity in someone previously infected
61
prophylactic vs therapeutic vaccination
prophylactic vaccination
- prevention
- develop immunity in susceptible host
therapeutic vaccination
- post-exposure
- augments/accelerates immunity in someone previously infected
*ultimate aim is eradication
62
what is the ultimate aim of vaccination?
eradication
63
what goes into a vaccine?
- active ingredient
- water
- preservatives and stabilisers
- residual traces
- adjuvants
64
what is the active ingredient in a vaccine?
a very small amount of a harmless form of the bacteria/virus you are immunising against
65
what is the adjuvant in a vaccine?
create a stronger immune response to the vaccine; pose no significant risk to health in the very small quantities
e.g. aluminium (naturally found in drinking water at higher levels)
66
what are the residual traced in a vaccine?
substances that have been used during vaccine manufacture, measured as parts per million/billion in the final vaccine
e.g. formaldehyde (naturally found in human body)
67
discuss immunisations in the UK
for uni you are advised to have:
- the MenACWY vaccine (can ask GP for this until 26th bday)
- 2 doses of MMR vaccine
68
what are the 'risk groups' which require extra vaccines (UK)?
> underlying medical conditions
> pegnant
> infants born to HepB infected mothers
> infants born in high TN incidence areas
69
explain and discuss herd immunity
when a large proportion of a population is vaccinated, it is harder for an infectious disease to spread.
protection for communities; in particular those who cannot be vaccinated
doesn't offer high level of protection to individuals.
decreases unnecessary deaths: breaks chain of transmission.
percentage of population to achieve herd immunity varies with each disease.
70
what is the percentage of population which must be vaccinated to achieve herd immunity?
varies with each disease
71
what is the reproduction number?
ratio/rate (basic reproduction number)
- epidemiologic metric used to describe the contagiousness/transmissibility of an infectious agent
- estimated with complex mathematical models
- affected by several factors (biological, sociobehavioural, environmental)
an ourbreak is expected to continue if R0 has a value of >1 and to end if R0 if <1
72
what factors affect the reproduction number?
biological
sociabehavioural
environmental
73
what is the R0 value for when and outbreak is expected to continue vs end?
an outbreak is expected to continue if R0 has a value >1 and to end if R0 is <1
74
describe the history of vaccination
> attempts to vaccinate date from 1695
> 'with the exception of safe water, no other modality, not even antibiotics, has had such a major effect on mortality reduction and population growth'
alternative?:
The nose was plugged with powdered smallpox scabs laid on cotton wool;
Powdered smallpox scabs were blown into the nose;
A healthy child wore the undergarments of an affected child for several days;
A piece of cotton containing contents of smallpox vesicle was stuffed into the nose;
White cow fleas were ground into powder and made into pills (first oral vaccine?)
75
how was smallpox eradication achieved?
*factors favouring smallpox eradication through vaccination
1. effective and safe vaccine (cheap, heat stable and 1 dose)
2. lifelong natural immunity induced
3. short period of communicability (transmission easily curtailed)
4. highly characteristic clinical syndrome (distinctive rash)
5. easy and reliable means of diagnosis
6. no nonhuman/or environmental reservoir (key for eradication)
7. genetically stable causative agent
8. seasonality of occurrence
76
what was key for the eradication of smallpox?
no nonhuman or environmental reservoir
77
what were the highly characteristic clinical symptom of smallpox?
distinctive rash
78
polio vs measle vs rubella transmission
(candidates for global eradication)
polio; transmitted via person-person contact
measles; transmitted via direct contact/droplet spread
rubella; transmitted via direct contact/droplet spread
79
advantages and disadvantages of non-replicating (non-living) viral vaccines
advantages;
no risk of infection (safe!)
can be quicker to produce
disadvantages;
may be less immunogenic (induce a less efficient cytotoxic T cell response)
may require adjuvants
often require boosters
may not stimulate a local IgA mucosal response
80
what conclusion can be made about vaccines in terms of safety/effectiveness, eradication and various strategies?
safe and effective; boost the immune system to defend against infectious agents
eradication;
ultimate goal of vaccination (but so far smallpox is the only human pathogen to be eradicates)
various strategies;
one size does not fit all and there can be challenges to overcome
81
what is the only human pathogen to be eradicated?
smallpox
82
understand the disease pathology of cholera and the virulence factors of the causative bacterium
symptoms, toxins, mechanism of action
83
recognise the role the environment plays in cholera
water/food contamination, copepods
84
understand methods of predicting future cholera outbreaks
chlorophyll, sea height/temperature
85
what bacterium causes cholera?
bacterium: VIBRIO CHOLERAE
86
what are the symptoms of cholera?
acute diarrhoeal infection in healthy individuals, but can become severe.
symptoms:
- profuse, watery diarrhoea; 'rice water stools' up to 1L/hour
- leg cramps
- vomitting
- poor skin elasticity
- severe dehydration leads to >100,000 deaths annually
87
how do people get cholera?
ingestion of contaminated food/water, normally in areas with poor sanitation
88
how quickly do cholera symptoms present?
can present from 3h - death within hours
89
what does the cholera bacterium release in the intestine?
Cholera toxin (CT):
V. cholerae (vibrio cholerae) rapidly increases in the intestine releasing a toxin- cholera toxin (CT)
90
what does CT cause?
CT (cholera toxin) prevents intestine from absorbing water from food, resulting in diarrhoea and severe dehydration
91
what is the cholera toxin composition ?
CT/CTX:
- AB toxin similar to labile toxin found in E. coli
- complex is made up of 6 protein subunits
1. 1xA subunit (enzymatic)
1. 5xB subunits (binding)
92
explain the action of CT
(cholera toxin)
AIM: increase levels of cAMP inside host cells
1. CT binds to host cells via B subunit and forms a toxin-containing vacuole
2. on route to the ER, a subunit is cleaved and A1 relocates to the cytoplasm
3. CT binds to G protein, constant stimulation of adenylate cyclase -cAMP produced
4. High cAMP activates ion channels (CFTR) produced
5. escaping water enters the intestinal lumen, resulting in diarrhoea
93
how does CT bind to host cells and what does this form?
cholera toxin (CT) binds to host cells via B subunit and forms a toxin-containing vacuole
94
how is cAMP produced in the cholera toxin mode of action?
CT (cholera toxin) binds to G protein; constant stimulation of adenylate cyclase -cAMP produced
95
what does high levels of cAMP activate?
ion channels (CTFR) produced.
*escaping water enters the intestinal lumen, resulting in diarrhoea
96
discuss the bacterium vibrio cholerae.
> gram-negative, comma shaped bacterium
> facultative anaerobe
> has a pilus and flagellum
> pathogenesis due to toxin pilus
toxin co-regulates pili (TCP)
- formation of microcolonies
- colonisation of intestine
- receptor to CTX
97
what is TCP?
toxin co-regulated pili (TCP)
- formation of microcolonies
- colonisation of intestine
- receptor to CTX
98
what can CTX bacteriophage do?
cholera toxin filamentous phage (CTX) can infect non-pathogenic VIBRO species with virulence genes, encoding for cholera toxin
- horizontal transfer of genes can confer pathogenicity
99
how many serogroups of V. cholerae are there? how many are toxigenic?
>150 serogroups of V. cholerae but only 2 are toxigenic
100
serotypes
a way of grouping cells or microorganisms, such as bacteria or viruses, based on the antigens or other molecules found on their surfaces.
101
when was the first cholera pandemic?
1817
*almost all countries in Asia affected
102
describe the history of cholera
1st pandemic (1817); almost all countries in Asia affected
2nd pandemic (1826); north america/europe due to trade advances
5th pandemic (1881)
6th pandemic (1899)
7th pandemic (2010); haiti outbreak, the most deadly modern outbreak, 9,500 deaths
103
what disease was the most deadly modern outbreak?
bacterial disease; cholera
most deadly modern outbreak (Haiti 2010)
9,500 deaths
104
who was the first to isolate V. cholerae bacterium? (when?)
Filippo Pacini (1854)
(vibrio cholerae)
105
who was credited for the discovery of the cholera causing organism? (when?)
Robert Koch (1883)
*Vibrio cholerae
106
describe the epidemiology of cholera in the 3rd pandemic of 1849
- during the 3rd pandemic (1849), a series of cholera outbreaks lead to >10,000 deaths in London
- suspected water, unwashed hands and shared food was the source of infection
- mapped the location of those infected and found they all used a water pump on Broad Street
- removal of the handle resulted in a decline of infections
*contaminated water was identified as the source of cholera outbreak
107
what are the incidences of cholera?
~ 80% cases are not reported
estimates to be 1.3-4.0 million cases of cholera every year, with up to 143,000 deaths annually
58 countries reporting outbreaks
*Haiti, Dominican republic
108
epidemic vs endemic vs pandemic
epidemic;
an outbreak of disease that spreads quickly and affects many individuals at the same time
endemic;
A disease outbreak is endemic when it is consistently present but limited to a particular region.
pandemic;
occurs if the disease spreads to multiple areas or the entire globe
109
epidemic
an outbreak of disease that spreads quickly and affects many individuals at the same time
(sudden unexpected outbreak affecting many people)
110
endemic
A disease outbreak is endemic when it is consistently present but limited to a particular region.
(repeated occurence)
111
pandemic
occurs if the disease spreads to multiple areas or the entire globe
112
explain cholera incidences in terms of endemic and epidemics
Many countries reporting cholera are endemics for the disease (repeated occurrence).
Epidemics can also occur (sudden unexpected outbreak affecting many people).
113
what is the treatment for cholera?
Severe cases need to be treated with oral rehydration, therefore delivery clean water and sanitation is essential for controlling cholera.
(844 million people lack even a basic drinking water service)
114
how many people still lack even a basic drinking water service?
844 million people
115
what is the role of the environment in cholera?
V. cholerae is a natural inhabitant of the aquatic environment making cholera one of the most prevalent water-related infections.
Vast majority of cholera outbreaks originate from coastal locations, linking the environment to disease.
The Bay of Bengal has been describes as the 'native homeland of cholera'; sequencing of strains from the 7th pandemic revealed they all arose from a single source in the Bay of Bengal
116
where has been described as the 'native homeland of cholera'?
The Bay of Bengal
(sequencing of strains from the 7th pandemic revealed they all arose from a single source in the Bay of Bengal)
117
what environment is V. cholerae a natural inhabitant of?
the aquatic environment
*making cholera one of the most prevalent water-related infections
118
where can v. cholerae also survive for extended periods of time?
coastal waters.
V. cholerae is not just a human pathogen spread by oral-faecal route; it can survive in coastal waters for extended periods of time
119
what can be said about the Vibrio Cholerae life cycle?
V. cholerae has a complex life cycle where it can exist in various states and associate with other organisms
120
what organism play an important role in the transmission and survival of V. cholerae?
copepods
121
what is the relationship between copepods and v. cholerae?
Vibrio cholerae colonises the gut and egg masses of copepods, establishing a commensal association and utilising chitin as a carbon source.
Copepods feed on algae and therefore the population of these zooplankton is strongly associated with algae blooms.
- V. cholerae forms biofilms within copepods
- protective environment from external stresses
- copepods exoskeleton is made up of chitin (insoluble), bacteria break this down to provide useful carbon source in seawater
*this association with copepods is crucial for the epidemiology of cholera
122
what is a commensal relationship?
a type of relationship between two living organisms in which one organism benefits from the other without harming it.
123
what part of copepods does v. cholerae colonise?
V. cholerae colonises the gut and egg masses of copepods (establishing a commensal association)
124
what does V. cholerae use as a carbon source when in a commensal association with copepods?
CHITIN
[copepod exoskeleton is made of of chitin (insoluble), bacteria break this down to provide useful carbon source in seawater]
125
what is the population of the zooplankton, copepods, strongly associated with?
algae blooms.
Copepods feed on algae and therefore the population of these zooplankton is strongly associated with algae blooms.
126
biofilm
A biofilm is defined as a community of microorganisms attached to an inert or living surface by a self-produced polymeric matrix or an assemblage of microbial cells associated with a surface and enclosed in a matrix of primarily polysaccharide material.
127
was old cotton/nylon sari more efficient at removing copepods?
old cotton sari was more efficient at removing copepods than new nylon sari
128
discuss the prediction of cholera
several environmental conditions create a favourable habitat for cholera.
SATELLITE BASED REMOTE SENSING;
Satellite sensing can allow the detection of microbes by the use of space-based sensors, (providing a new view of or oceans).
Direct- microbes can be seen by sensors, identifies on optical properties (bioluminescence from blooms).
Indirect- identification and quantification by physical or physiological properties (chlorophyll in cyanobacteria).
*V. cholerae can be estimated based on sea temperature and phytoplankton abundance
129
what are the benefits of predicting cholera?
- morbidity and mortality
- mitigate wide range of socioeconomic factors that are consequences of epidemics
- longer term health burdens from malnutrition (stunted growth) are decreased; rapid intervention of treatment
130
vibrio abundance
sea surface temp + phytoplankton abundance
sea surface height = flooding + increased human exposure
131
satellite based remote sensing of cholera
sea surface temp/height and chlorophyll levels were examined as potential environmental parameters for the prediction of cholera outbreaks.
cannot relay on a single factor.
most studies have focussed on the Bay of Bengal area, with other studies showing regional differences require different models of prediction; tidal intrusion and river flow.
Satellite sensing can allow the detection of microbes by the use of space-based sensors, providing a new view of our oceans.
DIRECT; microbes can be seen by sensors, identified on optical properties (bioluminescence from blooms)
INDIRECT; identification and quantification by physical or physiological properties (chlorophyll in cyanobacteria)
*V. cholerae can be estimated based on sea temperature and phytoplankton abundance
132
what is another model of prediction of cholera apart from satellite based remote sensing?
tidal intrusion and river flow.
*regional differences require different models of prediction
133
what does direct satellite based remote sensing measure?
Microbes can be seen by sensors, identified on optical properties; bioluminescence from blooms (algae)
134
what does indirect satellite based remote sensing look at?
identification and quantification by physical or physiological properties; chlorophyll in cyanobacteria
135
what is the relationship between climate change and cholera?
Recent studies have shown climate change creates a favourable environment for V. cholerae to grow.
Sunlight, temperature, nutrient-> growth of algae, copepods, V. cholerae.
(increasing need to understand the potential outcomes on human health)
136
discuss the Haiti cholera outbreak of 2010
The cholera epidemic in Haiti claimed 7000 lives in 18 months, being one of the largest outbreaks in recent history.
The first cases of cholera were confirmed 10 months after the earthquake, with all 10 provinces of Haiti impacted within weeks.
(was v. cholerae present in the estuaries? was it imported to the shipping port? was a human source the origin?)
In July 2010, an epidemic was declared in Nepal while UN peacekeepers were on a training programme.
Reports of sanitation problems began in October 2010 from the UN camp; overflowing septic tank, poor drainage system.
It took 6 years for the U.N. to accept responsibility and apologise for their role on the cholera outbreak in Haiti.
- following negative testing in Nepal, troops remained in there for 10 days prior to leaving for Haiti, with no further testing performed
- initial reports from the base camp stated 'no severe diarrhoea' and did not mention acute cases
- argued there was no need to investigate the source of the outbreak
- no independent investigators were allowed access to the samples
137
what is the WHO cholera control plan?
aims:
reduce cholera deaths by 90%
up to 20 countries could be cholera free by 2030.
1. water, sanitation, hygiene
2. healthcare systems
3. surveillance and reporting
4. use of oral vaccine
5. community engagement
138
explain the biology of Mpox virus disease
139
understand that mpox virus is a zoonotic infection and explain how it spreads
140
understand the molecular technologies used to diagnose the infection and describe the clinical symptoms
141
appreciate the vaccine and treatment options available
142
what was Mpox disease previously called?
monkeypox virus
143
when was Mpox first discovered?
1958.
two outbreaks of pox-like disease in monkeys kept in research colonies.
144
when was the first documented human case of Mpox? (where?)
1970.
in what is now the Democratic Republic of Congo (DRC)
145
describe the Mpox virus. (MPXV)
- linear double-stranded DNA
- Genus: orthopoxvirus
- Family: poxvirdae
- brick-shaped virion
- enveloped
- host cell-derived membrane
146
what is the poxvirus replication cycle?
1. binding/attachment
2. fusion/entry
3. nucleocapsid release
4. transcription
5. translation
6. replication
7. lysis/budding
8. release/egress
147
MPXV clade I and clade II
Clade I:
- responsible for the current rise of cases in central and eastern africa
- incidence (2040); 16,000
- fatality rate of 3.6%
Clade II
- caused the global outbreak that began in 2022
- incidence (2022); 92, 167
- fatality rate 0.03%
*Clade I is endemic to central africa whereas Clade II is endemic to west africa
*historically, clade I causes more severe disease than clade II
148
where are clade I and clade II endemic to?
Clade I: Central Africa
Clade II; West Africa
149
discuss the outbreaks of MPXV
(discovered in 1958)
- initial case of mpox were misdiagnosed as chickenpox
- WHO began actively monitoring human mpox cases in Congo in the 1980s
- cases remained largely endemic to Africa with some cases exported internationally
- in 2022, over 60, 000 cases of mpox had been reported in over 105 countries (WHO declares mpox a public health emergency of international concern)
150
discuss the may 2023 and aug 2024 mpox outbreaks
May 2023;
The spread of clase II mpox has reduced by 90% between Feb-May 2023 in comparison to previous 3 months.
Therefore, after more than 87,000 cases and 140 deaths reported in 111 countries the PHEIC was ended.
Aug 2024;
The more deadly clade Ib began to spread across borders.
Concerns are heightened by increasing evidence of mpox-HIV co-infection.
Mirroring the historical spread of HIV on the continent via transport corridors and sexual networks, raising the risk of infection among women and children.
151
describe mpox transmission
First spreads to people from animals (zoonotic infection)
Mpox virus can infect various mammalian species (rodents, gazelles, hedgehogs, prairie dogs, non-human primates and humans).
Specified method by which MPXV spreads to humans is unknown; direct transmission (touch, bite, scratch), indirect transmission (blood, body fluids, cutaneous lesions, or mucosal lesions)
The virus enters the body through:
Skin breaks; some of which are not apparent
Eyes, moth, nose and other regions of respiratory tract.
*Animal reservoir species UKNOWN (problem for eradication)
152
what is a reservoir?
A reservoir is usually a living host of a certain species, such as an animal or a plant, inside of which a pathogen survives, often (though not always) without causing disease for the reservoir itself
153
what is a problem for the eradication of mpox?
the animal reservoir species is unknown
154
direct vs indirect methods of transmission
direct: touch, bite, scratch
indirect: blood, body fluids, cutaneous lesions, mucosal lesions
155
what are mpox (MPXV) symptoms? when do the begin?
Can cause a rash that may look like pimples or blisters, anywhere on the body, including the hands, feet, chest, face, or mouth, and sometimes on or near the genitals or anus.
(Usually begin within 7 days but can take up to 21 days; typically last 2-4 weeks; may last longer in those with weakened immune systems)
156
what are the 5 visual stages of mpox?
1. MACULE; the rash starts as flat, red spots (lasts 1-2 days).
2. PAPULE; the spots become hard, raised bumps (lasts 1-2 days).
3. VESICLE; the bumps get larger, they look like blisters filled with clear fluid (lasts for 1-2 days).
4. PUSTULE; the blisters fill with pus (lasts 5-7 days).
5. SCABS; the spots crust over and become scabs that eventually fall off (lasts for 7-14 days).
157
what is the mpox diagnosis?
real-time PCR tests
- gold standard for MPXV diagnostics
- highly sensitive and fast diagnostics
- multiple different targets available
- important for determining which clade is present
- highly important techniques for determining seroprevalence of MPXV within a population
- integral to vaccine efficacy studies
- limited use of MPXV diagnostics
- potential cross-reactivity with other circulating orthopoxviruses
- IgM maybe more informative than IgG tests
*lateral flow device as a point of care diagnostic
158
what diagnostic technique of MPXV is used in addition to real-time PCR?
- used in addition to traditional diagnosis
- due to high reagent and infrastructure costs as well as requirement for specialist training makes this unsuitable for clinical use
- therefore, only a small proportion of clinical samples are being sequenced
- to combat this, new approaches such as MinlON sequencers are being used to increase the number of sequences available
- like COVID-19, these sequences are crucial to public health decision making
159
what is the treatment for MPXV?
no proven effective antiviral therapies for mopox.
Three drugs commonly used in clinic;
- tecovirimat
- cidofovir
- brincidofovir
*often prescribed as combination therapy to avoid drug resistance
Supportive care:
- oral/intravenous fluids
- treat the symptoms
- treat other infections as necessary
160
what 3 drugs are commonly used in clinic to treat mpox?
1. tecovirimat
2. cidofovir
3. brincidofovir
(often prescribed as combination therapy to avoid drug resistance)
*no proven effective antiviral therapies for mpox
161
is there a vaccine against MPXV?
Smallpox vaccination protects against MPXV.
Two approved vaccines against MPXV
> third-generation smallpox vaccines
> both vaccines are live-attenuated
> MVA-BN and LC16m8
effective against both clades I and II
*people born after 1971 are at higher risk of infection
162
what are the two approved vaccines against MPXV?
1. MVA-BN
2. LC16m8
third generation smallpox vaccines; both are live-attenuated; effective against both clades I and II.
163
what type of vaccine are the vaccines used against MPXV?
live-attenuated
164
discuss preparedness in terms of mpox
community engagement is key!
> similarities to the COVID-19 pandemic community prevention
> large emphasis on getting vaccinated where possible
> strong advocacy presence from MSM community
165
what conclusions can be made to summarise mpox?
mpox; formally monkeypox and related to smallpox- a persistent public health threat worldwide
zoonotic; transmitted from animals- but reservoir is still unknown
community engagement is key; outbreak control relies on suitable prevention and control methods- vaccination is key
166
live-attenuated vaccine
Live-attenuated vaccines contain live pathogens from either a bacteria or a virus that have been "attenuated," or weakenedLive-attenuated vaccines contain live pathogens from either a bacteria or a virus that have been "attenuated," or weakened
167
inactivated vaccine
Inactivated vaccines use the killed version of the germ that causes a disease. Inactivated vaccines usually don't provide immunity (protection) that's as strong as live vaccines
168
be able to define emerging diseases and know the differences between them
169
understand the risks of emerging disease and the main categories they fall into
169
be able to provide examples of the risk factors
170
understand the importance of one health and the need to be ahead of the game
171
what is the greatest threat to global health?
the spread of uncontrolled epidemics.
- especially those that cross border
- have social and economic impact
- Ebola in west Africa was an alarm call to highlight this need
- needed forethought and pre-emptive action
172
what 3 major conclusions can be drawn about disease epidemics?
1. response is not enough- preparedness for outbreaks requires increased readiness and building resilient health systems
2. technologically advanced tools are required to anticipate the emergence and amplification of infectious disease outbreaks
3. new risks in the context of big cities and intense mobility of globalised world- better public health interventions
'effectively anticipating epidemics will contribute to reinforcing global health security mechanisms including assessment of infectious disease risk... it is expected that the outputs of this consultation will inform and guide preparedness efforts in the future'
173
newly emerging disease
disease recognised in humans for the first time
174
re-emerging disease
diseases that have historically infected humans and continue to reappear in new locations or as resistant forms
175
deliberately emerging disease
diseases associated with intent to harm, includes bioterrorism
176
accidentally emerging disease
diseases created by humans that are released unintentionally
177
3 risks of emerging infectious diseases
1. disease factors
2. human factors
3. ecological factors
(highlights why the One Health approach is vital)
178
discuss the disease factors in emerging infectious diseases
Evolution and adaptation happens quickly, especially in viral diseases.
Most are RNA viruses with high mutation rates, rapid evolution and environmental adaptability.
Happens through point mutation by recombination and reassortment.
HOWEVER...
Genetic evolution of viruses does not seem to be the major cause of virus emergence.
Viruses are more stable within their particular ecological niches.
Human factors are the most potent factors driving disease emergence.
179
what factor is the most potent in driving infectious disease emergence?
human factors.
(viruses are more stable within their particular ecological niches; things strive for stability)
180
what are examples of human factors which drive the emergence of infectious diseases?
- POPULATION GROWTH
- urbanisation
- human population moement
- human travel
- vector travel
- hunting
- pasturage practices
- expanding agriculture
- deforestation/land development
- dam construction
181
discuss human travel in terms of emerging infectious diseases (human factors)
We can reach any part of the world in less than 24 hours.
Travel allows us to carry anything (within reason) with is.
Including diseases.
Previously diseases would be more contained and/or take longer to reach a global level
This alone is the BIGGEST reason for an increase in emerging diseases
182
what is the biggest reason for an increase in emerging diseases?
human travel
183
discuss vector travel in terms of emerging diseases (human factors)
vector travel
> as we move around the world we also pick up hitchhikers
> vectors can be transported by aircrafts
> outbreak of west Nile virus in New York (1999) via mosquitoes (culex pipiens) from the Middle East- via aircrafts
> further enhanced survival due to climate changes allowing vectors in areas that they otherwise previously could not
184
discuss hunting and pasturage in terms of emerging diseases (human factors)
60% of known pathogens of humans have a zoonotic origin.
75% of emerging infectious diseases are from zoonotic pathogens.
Wildlife play a key role as reservoirs of diseases.
Crossing the species barrier is when issues arise.
Disease adapt and become human-human transmission.
(how pandemics start)
HUNTING:
Traditional hinting in Africa can mean that humans come into close contact with nonhuman primates frequently; HIV originated in Africa in the late 1940s, earliest case known in 1959 in DRC; HIV is not a zoonotic disease but was zoonotic in origin; SIV (simian immunodeficiency virus) found in nonhuman primates
PASTURAGE PRACTICES:
Monoculture practices promote susceptibility to infections; In developing countries the close proximity of animals and humans causes viruses to merge; China, as an example, wildlife trade is illegal, but wild animals are commonly sold in live-animal markets (wet-markets); Chinese culture fresh food from wild animals are considered great delicacies, but animal housing conditions are often poor; Zoonoses can transmit from animals to food handlers- often the simplest explanation for cross-species contamination
185
what percentage of known pathogens of humans have a zoonotic origin?
60%
186
what percentage of emerging infectious diseases are from zoonotic pathogens?
75%
187
SARS-CoV-2
(severe acute sespiratory syndrome coronavirus -2)
> a new strain of coronavirus that was not previously identified in humans before- hence it is often referred to as novel
> bats are a common host to coronaviruses
> generalist virus circulating in horseshoe bats- evolutionary analysis- lineage from which SARS CoV 2 emerged has been present in bats for several decades.
> generalist viruses do not need an intermediate host for evolution but it does help for host switching
> pangolins get sick so are not a natural reservoir but could act as transmitters between humans
188
what did SARS-CoV-2 make us consider?
(severe acute respiratory syndrome coronavirus -2)
- deadly addition to emerging infectious diseases
- forced us to consider how we interact with each other and the natural world
- need for us to adapt quickly
- devastating wake up call; should force us to think more collectively/globally
- a very strong need to take the whole picture into consideration
189
how does global warming affect emerging infectious diseases (ecological factors)?
> small increase can trigger an explosion of insect populations
> insects are known vectors of EIDs
(West Nile virus in New York became more established due to: mild winter, dry spring, reduction in predators, mosquito to bird transmission established a wildlife reservoir)
190
summarise emerging infectious diseases
Threats of EIDs and the impacts that they have take many forms;
- disease dynamics (morbidity/mortality)
- social impacts including mental health
- economic impacts
Risk factors;
- disease factors
- human factors (largest impact is human travel)
- ecological factors
HAS to be a One Health approach; need a strong strategy in place for the 'just in case' with worldwide backing
191
reminder of what one health and zoonoses are
192
How do we eradicate diseases and what does it actually mean?
193
recent 'news worthy' tropical diseases, and what makes a disease news worthy?
194
Differences in how countries tackle one health diseases
195
A positive case study on eradication
196
what is one health?
One health recognises that the health of humans, animals and ecosystems are interconnected.
It involves applying a coordinated, collaborative multidisciplinary and cross-sectoral approach to address potential/existing risks that originate at the animal-human-ecosystem interface.
(Many of the diseases within the One Health framework are linked to human-animal health interactions, they are all part of a group labelled as zoonotic diseases)
197
what are zoonoses?
Diseases and infections where the agents are transmitted between vertebrate animals and humans.
(Interactions of agent, host and the environment they share determines whether or not transmission of the agent will be successful)
Carrier hosts are important in the persistence of many zoonotic agents.
- fungi, bacteria, viruses, protozoa, helminths, arthropods all include some zoonotic agents
198
what are important in the persistence of many zoonotic agents?
carrier hosts
199
what are the reservoirs of zoonoses?
vertebrate animals
(animals with a backbone/spine)
*vertebrate animals are the reservoirs of zoonoses and the agents may be transmitted directly/indirectly by fomites/vectors
200
what are some of the ways by which eradication can be defined?
Control of an infection at which transmission ceased within a specified area.
Elimination of the occurrence in the absence of all preventive measures.
Reduction/eradication of the worldwide incidence of a disease to zero as a result of deliberate efforts.
Extinction of disease pathogen.
201
eradication; control
the reduction of:
- disease incidence
- prevalence
- morbidity
- mortality
(to a locally acceptable level)
as a result of:
- deliberate efforts
- continued intervention measures
e.g. diarrhoeal diseases
202
eradication; elimination of disease
reduction to zero of:
- the incidence of a disease
- in a defined geographical area
as a result of:
- deliberate efforts
- continued intervention measures
e.g. neonatal tetanus
203
eradication; elimination of infections
reduction to zero of:
- the incidence of a disease
- infection caused by a specific agent
- in a defined geographical area
as a result of:
- deliberate efforts
- continues measured to prevent re-establishment
e.g. measles
204
eradication; reduction/eradication
permanent reduction to zero of:
- the worldwide incidence
- infection caused by a specific agent
as a result of:
- deliberate efforts
- intervention methods are no longer needed
e.g. smallpox
205
eradication; extinction
the specific infectious agent no longer exists:
- in nature
- in the laboratory
e.g. none...
206
what are the 5 differing levels of eradication and how achievable are they?
1. control (achievable)
2. elimination of disease (achievable)
3. elimination of infections (achievable)
4. reduction/eradication (hard, but manageable)
5. extinction (probably almost impossible)
207
what are 3 ways to eradicate?
1. effective intervention to interrupt transmission of the agent
2. practical tools with sufficient sensitivity and specificity
3. humans are essential for the life cycle of the agent, which has no other vertebrate reservoirs and does not amplify in the environment
208
comment on the different approaches to tackling one health across countries
- health investment doesn't relate to health equality
- prevention is better than a cure but not easy, especially on a global effort
209
toxocara ssp
- first discovered in humans in 1950
- toxocara larvae detected in ocular granulomata in children with suspected retinoblastoma
- further clinical symptoms have been described in humans
- however, the significance of human toxocariasis as a disease entity remains enigmatic as symptoms can be generalised, multifaceted and cryptic
problematic issues for control of toxocara:
- complex more of transmission
- multiple sources of infection
- variation in exposure levels
- complex symptoms that are multifaceted, general and diverse
one health provides a framework for understanding the epidemiology of complex parasitic diseases:
- one health provides a framework for this
- veterinarians
- medical clinicians
- parasite epidemiologists
- environmental health experts
- wildlife biologist
it it worth it?
- is the focus in the wrong place as it affects wealthy countries?
210
why is toxocara problematic for control?
- complex more of transmission
- multiple sources o infection
- variation in exposure levels
- complex symptoms that are multifaceted, general and diverse.
211
how does tapeworm attach to organ?
with hooks and suckers
212
taenia solium; pork tapeworm transmission
get from eating uncooked pork
213
would eradication of taenias (pork tapeworm) achievable? and how?
should be achievable with these 'simple' targets;
1. mass drug administration (treatment)
2. identification and treatment of cases
3. health education
4. improved sanitation
5. improved livestock husbandry
6. vaccination of livestock
7. improved meat inspection
214
why is eradication of taenias (pork tapeworm) so far a failure?
- disconnect between medical and veterinary responsibilities; not the best example of one health
- lack of funding
- mapping of taenias *1985-2014)
- only 141 reports from 476 districts in 29 countries = neglected
- strong links as a socially determined disease
- sub-saharan africa is heavily affected
215
what is the achievable outcome of eradication of toxocara and taenias ?
toxocara could be controlled whereas taenias would be reduced/eradiated
216
discuss eradication of guinea worms
(dracunculus medinesis)
- no drugs/vaccines available to cute/prevent infections
- no wild animal reservoirs known, is a zoonoses, wildlife hosts of dogs and baboons
- slow painful extraction (up to two week)
- damages worms can lead to secondary infections
*since eradication efforts started, the incidence of Guinea worm has reduced by 99.99%
>eradication so far successful: first example of human parasitic disease to be eradicated without the use of vaccines/medicines
>smallpox was first success, certified as eradicated in 1980
eradication measures taken:
- mapping, using community-based surveillance systems
- effective case containments measures
- safe water, health education, community mobilisation, filters, and control of vector
- regular reporting
- management of certification process for eradication (country-by-country)
certification process lead by WHO;
1. interruption of transmission; zero indigenous cases over a complete calendar month- move to 2
2. pre-certification; zero indigenous cases via active surveillance for at least 3 consecutive years- move to 3
3. certification; international certification team (ICT) visit the country to verify the national report
217
what is the eradication certificate process lead by WHO?
certification process lead by WHO;
1. interruption of transmission; zero indigenous cases over a complete calendar month- move to 2
2. pre-certification; zero indigenous cases via active surveillance for at least 3 consecutive years- move to 3
3. certification; international certification team (ICT) visit the country to verify the national report
218
explain the animal reservoir causing doubt in guinea worm eradication.
eradication measures taken:
- finding the remaining cases are the most difficult and expensive
- lack of access to areas and the security of them
- canine infections with D. mendinesis is a big challenge
- the detection, prevention and containment of canine cases is a priority
- this means that the current methods of surveillance need to be increased to incorporate animal reservoirs
- should not underestimate the importance of a communities based approach
219
summarise eradication
One health: health of humans is connected to the health of animals and the environment
Zoonoses: diseases and infections, the agents of which are transmitted between vertebrate animals and humans
Needs to be a clear definition of what eradication actually means to make sure everyone is working towards the goal.
Understand the different levels of eradication and how the eradication process can work on both local and larger scale.
Provide examples of One Health tropical diseases and understand their life cycles.
1. toxocara (ex. Dog roundworm)
2. taenia species (tapeworms)
3. dracunculus medinesis (guinea worm)
Understand how different countries tackle one health diseases and the nature of their international position/standing.
220
how can you go about eradicating disease?
1. mapping/surveillance; comprehensive community-based network with a timeframe
2. stop contamination; promote management to halt the spread and provide solutions to the source of contamination
3. education; the disease, prevention, solutions and having a collective responsibility (includes training local people)
4. certification by WHO; phase 1 (interruption of transmission, phase 2 (pre-certification), phase 3 (certification)
221
be able to recognise different types of surveillance strategies
222
give examples of (re)emerging diseases
223
describe how genomic data can contribute to infectious disease surveillance and understanding patterns of spread and emergence
224
what is surveillance?
continuous, systematic collection, analysis and interpretation of health-related data needed for the planning, implementation and evaluation of public health practice.
continuous- keep doing it
systematic- not haphazardly
analysed and interpreted
dissemination of findings- to inform action
225
what is monitoring?
- routine collection of information on disease
- often a defined population and time period
- more descriptive and less systematic than surveillance
- doesn't necessarily lead to action
226
how does monitoring compare to surveillance?
its more descriptive and less systematic
227
why do surveillance?
1. monitoring variants (e.g. drug resistance)
2. inform policy and practice
3. tracking interventions (assess impact)
4. gaining basic understanding of epidemiology
5. early warning system (detect outbreaks)
228
disease eradication and elimination
eradication:
permanent and global (only happened twice- smallpox, rinderpest)
elimination:
restricted to a specific geographic area
229
why are there challenges in confirming elimination?
no cases for >10 years
- true absence? or lack of detection?
230
what are the types of surveillance?
1. active surveillance
> of notifiable disease, targeted surveillance
2. passive surveillance
3. syndromic surveillance
231
active surveillance
- health department (or other authority) proactively contacts health care providers or laboratories requesting information about specific diseases
- more costly and labour-intensive
- tends to provide a more complete estimate of disease frequency
232
notifiable diseases
- legal duty to report
- within 24-72 hours, depending on level of urgency
- diseases with high public health or economic implications
- often 'exotic' (transboundary diseases)
233
give an example of a notifiable disease
bovine tuberculosis
endemic; scotland officially free since 2009; transmission can occur through nose-nose contact and also through contact with saliva, urine, faeces and milk; exotic-not normally present in UK
234
targeted surveillance
- directed at particular at-risk individuals (e.g. cancer screening for those with family history)
- helps improve health outcomes (early detection~ more effective treatment options)
235
passive surveillance
- regular reporting of observed cases but no active search
> minimum standard, present in most countries
> relatively cheap
> expect underreporting
- in contrast to active surveillance; which aims to determine true incidence
- includes 'ad-hoc' reporting (e.g. citizen science)
236
what is the challenge of passive surveillance?
under-ascertainment and under-reporting
(don't seek healthcare vs aren't reported but have sought medical care)
237
what is an example of under-reporting/under-ascertainment of a disease?
anthrax in northern Tanzania
~400 cases confirmed in 3 years of active case investigation and sampling vs <10 in previous years
*number of cases greatly affected by completeness of reporting
238
what can be used as sentinels of zoonotic disease risk?
wildlife.
Reports of dead crows were useful in defining the geographic and temporal limits of a west nile virus outbreak in north-eastern US (1999).
Health department received over 17,000 dead bird reports in 2nd half of year.
Suggestion: surveillance system based on bird deaths may deaths may provide sensitive method of detecting WN virus
239
what are the particular challenges with wildlife disease surveillance?
(observing and reporting of cases)
- remoteness
- scavengers
- topography (landscape)
240
discuss mobile phone reporting in terms of surveillance
In 2011, already 87% of global population used mobile phones.
As of January 2023, almost 7 billion people have access to smartphones (85% of global population).
Potential to reach large proportion of the population; works in almost any country- most people globally have access to mobile phone.
advantages:
low cost
high temporal resolution (e.g. daily info)
very fast and current data (data available immediately)
disadvantages:
privacy concerns (data can often be stored at coarser spatial resolution)
low specificity (recorded symptoms may not be specified to just one disease)
may not be very representative (only get data from those who choose to participate)
potential concerns:
- personal data and privacy
- non-specific symptoms
- non-representative sample (bias)
241
what is syndromic surveillance?
- look for rise in the number of people reporting particular types of symptoms, e.g. febrile illness (fever)
- monitor trends on web or other data collection platforms => 'nowcasting'
Syndromic surveillance systems monitor data from school absenteeism logs, emergency call systems, hospitals over-the-counter drug sale records.
Problem of being highly non-specific.
Monitor evolution of epidemic in real-time
- some methods make use of social media
242
laboratory-based surveillance
- diagnostic confirmation of aetiology (cause) of disease
- more specific than syndromic surveillance
- can detect; pathogen (culture), nucleic acid (PCR), antibodies (ELISA) -> exposure
*one of the goals of epidemiology is determining the etiology/cause of disease
243
what is the risk of syndromic surveillance?
risk of mis-diagnosis
e.g. malaria uncommon over-diagnosed. invasive bacterial, mycobacterial, fungal infections high.
- bacterial zoonoses common yet unrecognised
- mismatch between clinical diagnoses with actual diagnosis; implications for patient care
244
tracking the spread of infections using genetic data
Changes in virulence, transmission patterns, patterns of drug resistance.
e.g. Glycoprotein found on the surface of influenza viruses is integral to its infectivity; responsible for binding influenza virus to surface of target cells.
Neuraminidase enzyme facilitates cell entry.
Reassortment of gene segments of virus circulating in North American swine that combined gene segments from avian, human H£N2 and classical swine influenza lineages; started in April 2009; first observed in Mexico and is likely true source; multiple seeding events in US in April.
245
what type of protein found on the surface of influenza viruses is integral to its infectivity? what does it do?
Glycoprotein
- responsible for binding influenza virus to surface of target cells
246
what enzyme facilitates cell entry of influenza viruses?
Neuraminidase.
(glycoprotein found on the surface of influenza viruses is integral to its infectivity; responsible for binding influenza virus to surface of target cells; neuraminidase enzyme facilitates cell entry)
247
Ebola outbreaks in West Africa
(Zaire evolavirus; 12 genomes)
The 2021 lineage is nested within a clade that predominantly consists of genomes sampled from Guinea in 2014.
= new outbreak was not the result of a new spillover from an animal reservoir.
The branch by which the 2021 cluster diverges from the previous outbreak exhibits only 12 substitutions, which is far fewer than would be expected from the evolution of EBOV during 6 years of sustained human-human transmission.
=suggests a persistent infection with reduced replication/a period of latency
248
where do our own pathogens come from? (disease origins)
what are the two hypotheses?
1. co-evolution: pathogens inherited from our ancestors
2. cross-species transmission: more recent introductions from other species
*for most human infectious disease, genetic data support the second hypothesis
249
what is mumps?
a contagious upper respiratory infection
250
what large virus family includes some of the most significant human and livestock viruses?
Paramyxoviridae.
includes viruses such as measles, distemper, mumps, parainfluenza, Newcastle disease, respiratory syncytial virus and metapneumovirus
251
what are examples new emerging diseases of likely zoonotic origin?
SARS- bats
MERS- camels
Zika- apes/monkeys
252
source of major human diseases (malaria and HIV)
Great apes.
Plasmodium falciparum; the cause of malaria in humans, is of gorilla origin.
Pandemic from human immunodeficiency virus type 1 (HIV-1)- cause of acquired immune deficiency syndrome (AIDS0 stems from lentivirus infection of chimpanzees.
253
what are the 5 stages of zoonotic disease emergence?
1. agent only in animals
2. primary infection
3. limited outbreak
4. long outbreak
5. exclusive human agent
254
what are the 2 fundamental approaches to predicting zoonotic disease emergence?
1. cataloguing all wildlife pathogens and identify the ones most likely to emerge
2. better surveillance systems (especially in high-risk regions) to detect emergence as it happens
255
integrating genomics into surveillance
It is 2027, and our planet's changing climate and land-use patterns have meant that new emerging infectious diseases (EIDs) are spilling over into humans from wildlife reservoirs with increasing frequency.
Building off EID hotspot maps developed in 2008 (Ref. 55), a global public health consortium has implemented an online surveillance tool that scans the digital output of citizens, news organizations and governments in those regions, including data from local retailers on key health-related products, such as tissues and over-the-counter cold remedies.
In one such region, the syndromic surveillance system reports higher-than-average sales of a common medication used to relieve fever.
Spatial analysis of the data from the pharmacies in the region suggests that the trend is unique to a particular district; a follow-up geographic information system (GIS) analysis using satellite data reveals that this area borders a forest and is increasingly being used for the commercial production of bat guano.
An alert is triggered, and the field response team meets with citizens in the area. Nasopharyngeal swabs are taken from humans and livestock with fever as well as from guano and bat tissue collected in the area.
The samples are immediately analysed using a portable DNA sequencer coupled to a smartphone. An app on the phone reports the clinical metagenomic results in real time, revealing that in many of the ill humans and animals, a novel coronavirus makes up the bulk of the microbial nucleic acid fraction.
The sequencing data are immediately uploaded to a public repository as they are generated, tagged with metadata about the host, sample type and location and stored according to a pathogen surveillance ontology. The data release triggers an announcement via social media of a novel sequence, and within minutes, interested virologists have created a shared online workspace and open lab notebook to collect their analyses of the new pathogen.
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summarise infectious disease surveillance
Gathering information; importance of surveillance for prevention and control
- range of approaches, differing in time/cost and in accuracy/completeness of data
Animals as potential sources of new disease (zoonoses)- possible to predict emergence?
- early warning systems: how accurate? how sensitive?
Pathogen genetics offers way to track transmission, resistance and adaptation.
- incorporate into surveillance
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define and apply key terms in epidemiology
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provide examples of the impacts caused by infectious diseases
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recognise different modes of transmission and the importance of carriers and reservoirs of infection
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discuss a range of public health measures taken to reduce infection
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what is epidemiology?
The study of the distribution and determinants of disease frequency...and the application of this to control health problems.
Considers infection at the population-level rather than the individual.
How a disease is distributed in populations and the factors that influence it.
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who was the founder of modern epidemiology?
John Snow
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citizen science
In citizen science, the public participates voluntarily in the scientific process to address real-world problems.
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one health and zoonoses
One health: recognises the interconnectedness between animal and human health within a shared environment
Zoonoses: diseases transmitted to humans from other vertebrates
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the impact of infectious diseases on humans
Responsible for 16% of human deaths each year.
Main cause of mortality in low income countries.
Main killers:
- diarrheal diseases
- malaria
- tuberculosis
- HIV/AIDS
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what are the 4 main killers (infectious diseases) ?
1. diarrheal diseases
2. malaria
3. tuberculosis
4. HIV/AIDS
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what is the impact of infectious diseases on livestock?
1. Massive economic impacts
- direct loss
- costs of control
- trade restrictions
2. Important link to people's livelihoods
3. Relevance to human health (zoonotic diseases)
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what is the impact of infectious diseases on wildlife?
1. threat to rare and endangered species
2. disease-induced mortality can regulate host populations
3. wildlife reservoirs of infection
- zoonotic diseases
- livestock diseases
*transmissible cancers known as devil facial tumour 1 (DFT1) and devil facial tumour 2 (DFT2); both cancers spread by biting
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what is an infectious disease which impacts wildlife?
transmissible cancers known as devil facial tumour 1 (DFT1) and devil facial tumour 2 (DFT2); both cancers spread by biting
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what is morbidity?
frequency of disease within a population- measured by incidence/prevalence
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what is incidence?
the number of new cases per unit time
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what is prevalence?
the proportion of a population that has the disease at a given moments
- seroprevalence; proportion of serum samples reacting positively (containing antibody)
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what is seroprevalence?
Proportion of serum samples reacting positively (containing antibody).
*prevalence; proportion of a population that has the disease at a given moment
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Case fatality
proportion of those with clinical disease that die
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Mortality rate
relative number of deaths within the population per unit of time
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case fatality rate vs mortality rate
case fatality rate: proportion of those with clinical disease that die
mortality rate: relative number of deaths within the population per unit of time
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incidence vs prevalence
incidence: number of new cases per unit time
prevalence: proportion of a population that has the disease at a given moment
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give 5 causes of infectious diseases
1. viruses
2. bacteria
3. parasites (micro and macro)
4. fungi
5. prions, transmissible cancers
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transmission
Critical process; required for nay infectious agent to persist
-> no infection without transmission
Wide range of transmission mechanisms.
Linked to pathogen fitness: traits determining transmission are under selection and this might evolve.
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how is transmission linked to pathogen fitness?
traits determining transmission are under selection and this might evolve
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what are the 2 modes of transmission?
1. vertical: parent to offspring
2. horizontal: to nay other individual in the population
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give 3 types of horizontal transmission
1. close contact/body fluids
- ebola, smallpox
2. sexually transmitted infections (STIs)
- HIV/AIDS, syphilis
3. Aerosol/respiratory
- influenza, measles, tuberculosis
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give 3 types of indirect transmission
1. vector-borne
- malaria, Lyme disease, dengue fever
2. food-borne
- E. coli, staph aureus endotoxins
3. environmental contamination
- anthrax, cholera
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what is an example of multi-host pathogen?
influenza viruses
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explain multi-host pathogens
Majority of emerging infectious diseases are caused by multi-host pathogens: able to infect more than one species.
Transmission might involve wildlife, domestic animal and human populations.
(A multistate outbreak of HPAI A(H5N1) bird flu in dairy cows was first reported on March 25, 2024. This is the first time that these bird flu viruses had been found in cows.
On April 1, CDC confirmed one human HPAI A(H5N1) infection in a person with exposure to dairy cows in Texas that were presumed to be infected with the virus. This is thought to be the first instance of likely mammal to human spread of HPAI A(H5N1) virus. In May 2024, CDC began reporting additional, sporadic human cases in people who had exposure to infected dairy cows. )
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what does a reservoir do?
Maintains the pathogen independently of the target community
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what is a carrier?
Infected with limited/no clinical symptoms
e.g. staph aureus (~1/3 of people)
taenia multiceps- canine tapeworm that causes 'ormilo' (neurological disease) in sheep but no signs in dogs
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give examples of diseases with common carriers
staph aureus (~1/3 of people)
taenia multiceps- canine tapeworm that causes 'ormilo' (neurological disease) in sheep but no signs in dogs
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what factors affect infection outcome?
1. host (varying levels of susceptibility-breed, immunity)
2. environment (determines whether host/pathogen interact, impacts on both other factors)
3. pathogen (virulence factors, resistance)
(epidemiological triad)
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how did Venezuelan encephalitis evolve?
emergence of Venezuelan encephalitis in horses/humans required a single point mutation in the virus envelope gene.
(pathogen evolution)
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predicting probability of anthrax
Anthrax occurs mostly in areas characterised by low organic matter and in proximity to water bodies.
This suggests that the transmission of B. anthracis to animals likely drives the risk of disease, more than factors that favour the survival of spores in the environment.
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what properties of an infectious organism determine its ability to spread in a population?
R0 (basic reproductive number).
The average number of secondary infections caused by a single infected host in a completely susceptible population.
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what is an outbreak in terms of number of infections?
outbreak; number of infections is growing exponentially
R0>1
if affecting populations on a large geographic scale (i.e. globally) PANDEMIC
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endemic vs epidemic in terms of R0 value
endemic disease; numbers of infections remaining more or less stable through time (R0~1). Transition from epidemic to endemic might take some time.
epidemic/outbreak; number of infections is growing exponentially (R0>1) = pandemic on a global scale
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emerging infectious diseases
Disease with growing number of cases following its introduction into a host population.
Growing number of cases in existing population due to changes in epidemiology.
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prevention (breaking transmission chains)
1. hygiene
2. isolation (quarantine)
3. social distancing
4. personal protective equipment
5. drugs, antibiotics
6. vaccination
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protecting population vs. protecting the individual
HERD IMMUNITY
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summarise the principles of epidemiology
1. epidemiology (of infectious diseases) aims to understand why disease occur where/when thy do, and how infections spread through populations
2. transmission as the critical process
- many different mechanisms
- transmission efficiency might change through pathogen evolution
3. ability to spread is measured by R0, which determines,
- speed at which epidemic grows
- proportion of population that needs to be vaccinated
4. infectious diseases have major impacts on human/animal health, but also much more widespread impacts (e.g. economy, animal welfare, food security, conservation etc)
5. options for preventing transmission
- reduce probability of contact
- reduce probability of infection
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what are the wider spread impact that infectious diseases have other than the major impacts on human/animal health?
economy
animal welfare
food security
conservation
300
how might transmission efficiency change?
through pathogen evolution
301
what are the two options for preventing transmission?
1. reduce probability of contact
2. reduce probability of infection
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how is the ability of an infectious disease to spread measures?
by the R0 value
which determines the speed at which epidemic grows and the proportion of population that needs to be vaccinated
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what determines the proportion of the population which needs to be vaccinated?
the R0 value
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