Emerging Infectious Diseases Flashcards
1
Q
How many emerging pathogens are zoonotic?
How many emerging zoonotic pathogens are vector transmitted?
How many emerging/re-emerging diseases affecting humans have originated in animals (21st century)
A
- 75%
- 70%
- 75%
2
Q
What are emerging infectious diseases
A
= diseases that have recently
~ increased in incidence
~ spread geographically - e.g. due to climate change, mosquitos survive in more contries due to rise in temperature
~ infected a new species or population
- diseases caused by new varients assigned to known pathogen e.g. avian influenza
- pathogens newly resistant to antibiotics
3
Q
Why are their more EID in developed countries
A
- more people/livestock so more human-animal contact
- building people areas in close quarters to animals
- pasture next to arable crop (maximising land space, little gap between areas) - ecotones allow for lots of wildlife to live between different crops and spread disease
4
Q
What are the biggest problems that cause EID
A
vectors and wildlife
5
Q
Major global health threats
A
- pandemic risks and other EIDs in humans and animals
- pathogens turning more virulent = infect more easily and have bigger impact on individual affected
- existing pathogens moving into novel areas and hosts
6
Q
Global challenges to health maanegment
A
- increased productivity demand
- education (lack)
- increase population
- land use
- anthropogenic effect on nature (human impact e.g. deforestation)
- globalisation
- poverty
- increase demand for food
- natural disasters
- climate change
- movement over boarders
- gov one healthlack cooperation
- increase no. companion animals
antibiotic resistance
7
Q
Major drivers of EIDs (3 catagories and dirvers)
A
- drivers that enhance disease spread by existing pathogens into new areas
(increase animal pop, land use, climate change, increased pop density, globalisation, natural resource management challenges) - drivers that increase pathogen virulence
(mass-rearing, use of antibiotics) - drivers of emergance of novel pathogens
(increase human-animal contact, globalisation)
8
Q
Modelling the rate of EIDs
A
- the SIR model
- susceptible, infectives and removed
- necessary to determine:
~ factors that increase susceptability (compromised immune system, increase stocking density
~ factors that increase risk of exposure (movement)
~ factors that increase how infectious individual is (e.g. ringworm = only pass by direc contact, TB = aerosol, airborn = very transmissible
~ rate at which susceptible organisms get infected
~ rate at which infected individuals recover or die
9
Q
Factors that increase susceptability
A
- new pathogen in previously uninfected area (trade, infected vector or contaminated products)
- movement of naieve individuals where pathogens exist (migration, expanse of agriculture, exploitation of natural resources)
- if existing population are immunosuppressed (aging, poor vaccination program, poverty, undernutrition)
10
Q
Factors that increase the risk of exposure
A
- climate change
- high animals density and population
- increased no. of vectors
- industrilisation of animal production
- reduced food safety
11
Q
Factors that impact infectivity
A
- compromised immune system (aging, polution, malnutrition, water scarcity)
- inadequate access to veterinary/medical care (lack of funding, remote areas)
- ## excess use of antibiotics = resistant pathogens
12
Q
Bluetongue Virus - about
A
- non-contageous vector borne virus
- 27 strains
- emerged from east asia over 1000 years ago
- transmitted via midgies on the wind = Culicoides spp
- host to host transmission = biting midgies
- historically confined to tropical and subtropical areas
- goats ancestral host
- climate change and trade patterns lead to outbreaks on tempret regions
- 9 strains in europe
- UK BT free but risk of midgies
13
Q
Bluetongue - epidemic 2006-2008
A
- 2006 ~ BT virus serotype 8 (BTV-8) invaded areas substantially further north than previously
- 2000 cases confirmed end 2006
- queit until June 16th 2007 in germany (virus overwintered)
- rapid spread nov 2007 = 45000 cases
- sept 15th 2007 = first case in UK suffolk (came with animal in fleese = low temperature)
- dec 2007 = 66 cases in east england
14
Q
Analysis if BTV-8 in france 2007-2008 - 5 themes, 16 variables
A
- Host availability (density dairy, density of beef cattle, sheep density,)
- Vaccination (No. of vaccinated animals)
- Elevation (metres above sea level) may affect vector abundance
- Landscape-related variables (proportion of area covered by pastures, arable land or forests)
- Meteorological-related variables (average rainfall and temperature 1 month, and 2 months prior to first outbreak)
15
Q
Analysis if BTV-8 in france 2007-2008 - factors affecting disease emergance and spread (velocity)
A
- elevation reduced velocity the most followed by vaccination = 4.3km/day
- weather lag increased velosity (spread) the most = 5.3km/day
- average velosity = 4.9km/day
16
Q
Analysis if BTV-8 in france 2007-2008 - impact of land related variables
and impact of climate
A
- 10% increase in % of pastures or arable land increased velocity by 0.04km/day
- highest BTV spread in areas with:
~ highest % of pastures or arable land
~ highest edge densities between forest-pasture or forest-arable
(Pioz et al 2012)
- ecological variables related to Culicoides vectors (elevation temperature and rainfall) were the main factors influencing velocity
- velocity lowest = high rainfall (84.5-324mm/month) and low temperature (4.5-19 degrees)
- velocity highest = low rainfall (13.1-42.8mm/month) and high temperature (23.1-25.8 degrees)
17
Q
Blue tongue threat 2018
A
- germany
- outbreak 17th dec 2017
- 28 cases by 3rd wk of jan 2018
- 28 cases SW germany
- 28 cases north (luxembourg, netherlands, belgium at risk)
- large scale vaccination in 2006-08 controlled BTV-8 outbreak
- outbreak re-emerged = large no. unvaccinated animals
- require >95% vaccination of susceptible animals for 5 years to eliminate virus in N.europe
- new cases emerging at time when vector populations low
- vector season = late spring/summer so season has ended and cold in germany
- likly an effect of movement of cattle
- advised vaccination (not manditory)
- at least 80% vaccination required to prevent outbreak
18
Q
Bluetongue threat 2019 and 2020
A
- dec-mar 2019 = 50 outbreaks in germany
- 1 in belgium feb 2019, 3 in march
- march-july = 4 outbreaks in germany
- macedonia = 404 sheep infected
- greece first reported case in 2020 (277 total)
- 118 cases italy
19
Q
Buetongue threat 2021 and why five fold increase on numbers compared to same 5 months of 2020
A
- 140 cases from 1st jan - 31st may 2021
- 83 italy
- 1 germany
- risk to UK via importation
- uk farmers must vaccinate agaist BTV-8/4 if transporting animals to infected zones and traveling back to BTV free zone
20
Q
Challenges in management strategies - Global Public Good concept
A
- the increase in population and more people shifting from poverty to middle class cause increase in food demand and causes increased globalisation
- refers to goods whose benefits extend to all countries
- depend on each other around animal disease control
21
Q
Management strategies to reduce impact on EID on animal health - European Union and Animal Health Law
A
- common market in European union huge challenge for animal health policy = eliminates trade barrier for goods and labor, allows free movement of animals and people without restrictions, increase risk of disease spread
- new laws move away from finatial losses by animal disease and focuses on funding ways to prevent
(e. g. increase biosecurity, managing diseases control) - introduction of the Animal Health Law in 2016
~ greater use of new technology for animal health activities such as survalence of pathogens
~ earlier detection and control of emerging diseases
~ flexibility to adjust rules to local circumstance (outbreaks)
~ legal basis to monitor animal pathogens resistnt to antimicrobial agents
22
Q
Neglected zoonotic diseases
A
- dont cross international boaders easity but spread localy
- affect poor/disadvantaged people
- neglected by research
- considerable impact on morbidity/mortality
(e. g. bovine tuberculosis) - diseased under control in most parts of world but remain in developing world
- impacts livestock owners and families through infection of animals, diminishing productivity which contributes to circle of poverty
23
Q
Bluetongue - vaccines
A
- live attenuated vaccines introduced in early 1900s but genetic diversity continued to peak
- indroduced recombinant vaccines in 1990s = substancial decline in genetic diversity
- but still continuous emergance of new strains = vaccine development barely keeps up
24
Q
Bluetongue - migration of disease
A
- migration between asia and austrailia = started mid 1500s
- migration between asia and europe = late 1700s
- Europe primary source of BTV into Africa in 17/1800s = colonisation and export of livestock
25
Why is geography and climate strong influence on spread/transmission
(Pioz et al 2012)
- many Culicoides life cycle parameters related to temperature, humidity and windspeed
- temp influences activity, survival and development of Culicoides
- flying activity inhibited by heavy rainfall = decreased velocity
- elevation = found lowest velocities at highest elevation range
- dairy cattle density = higher density meant slower velocity
~ housed in buildings so discontinous host pattern, limited active dispersion of Culicoisdes, spread less to cattle compared to through diffusion ouside
~ less exposed to biting midges (milked in afternoon and housed all night)
26
Global drivers of disease emergence - Globalisation
= the spread of products and people across national boarders
- millions animals transported anually, affect wildlife and trade with exotic/pet animals = one of causes behind spread of amphibian chytridomycosis
- brings in new pathogens and vectors to naieve populations
- pathogens dont need dont need to be transported within host (e.g. ballast water = cholera)
- facilitates world wide spread of disease
- essential for trade and economies and desired for part of population for traveling
27
Global drivers of disease emergence - Deforestation and reforestation
- deforestation creates more larval habitats = incrase no. vectors
- most mosquitos oppertunistic, adapt to new hosts in these new areas = introduction of new disease cause other animals to be resevoirs
- increases risk of viral transmission = require long time to prob and salivate more which is how they spread the disease, spread more pathogen
- reforestation in suburban/rural areas lacks the high biodiversity in natural forests
- increased transmission of vector borne pathogens due to disaperance of hosts, not amplifying virus = reduce dilution effect cased by non- reservoir animals eng infected by vectors
- reforrestation associated with increased wildlife but less predators
- dominated by wild animals that benefit from fragmented habitats (e.g. squirrels, mice)
- reduction in species non-competent (not infectious) hosts for lyme disease and increase in resevoires = caused lyme disease to increase with increased reforestation
28
Global drivers of disease emergence - Hunting and bushmeat
- increases interface between humans and wildlife
- expose humans to wildlife vectors
- impact biodiversity = decrease disease resevoirs
or increase resevoirs in predator removed
- wild meat consuption risk factor for disease transmission
- improtant food source (proteins)
- trade involves direct contact with multiple people alongside pathogens of wild animals
-
29
Global drivers of disease emergence - Population growth and urbanisation
- >50% pop live in urban areas
- migrate to better job/lifestyle
- cities higher temperatures and less varied seasons = increase risk of disease
30
Global drivers of disease emergence - Irrigation and dams
= agricultural process of applying controlled amounts of water to land to assist in the production of crops
- contributed to 40% global crop production, increased outputs and crops beneficial to health
- association between increased irrigation and increased incidence of disease = Japanese encephalitis virus
~ density of rice fields shown to be positively associated with Culex tritaeniorhynchus ( main vector for JEV
31
Global drivers of disease emergence - livestock intensification and extensification and adv/dis for both in terms of disease management
- increasing demand for production of animal products in developing countries
- more animals kept in commercially, highly productive envrironment
- demand for organic products and higher animal welfare in developed countries = extensification
- increased indoor pig keeping reduced Toxoplasma gondii parasites compared to free range fams which showed re-emergance
- intensified production causes increased contactbetween animals, many that are geneticly similar, bred for other purposes rather than disease management and kept in stressful environments = increase risk of disease spread, high no.s carrying zoonotic pathogens
- intensive systems lack ventilation and safe disposal of manure
- industrialised systems cause increase segrigation of animals and their vectors
- extensive systems associated with disease risk
~ avian influenza outbreak in southeast asia dependant on rice production, duck densities and human pop density
~ backyard poultry keeping in poor/rural areas as well as small flocks in urban areas = biosecurity measures/awarness limited
