Veterinary Public Health- disease control

Question 1

interventions to control infection

Answer 1

prevent or reduce transmission (movement restriction, exclusion zones, social distancing, biosecurity, social distancing, remove infected individuals (culling, treatment, isolation), reduce ability to transmit (vaccination, herd immunity))
reduce the susceptible population (vaccination, geneetic resitance, make individual harder to infect, reomve a susceptible population))

Question 2

2 salmonella serovars

Answer 2

salomenalla enterica thyphimurium (ceca chciken, lower intestinal tract of others), salmonella enterica enteriditis (chicken repro and caeca, lower intestinal tract others)

Question 3

2 types of campylobacter

Answer 3

c. jejuni, c.coli. ceace, lower intestinal

Question 4

types of E.coli

Answer 4

EHEC/STEC/VTEC inc. o157. distal colon and rectum

Question 5

reasons for epidemic of salmonella enteritidis

Answer 5

internationalism of poultry indistry lead to import from asia/eastern europe via eggs or breeding stocks
exploited a niche due to eradication of antigenically similar gallinarum

Question 6

why was there a fall in salmonella?

Answer 6

underpining legislation for control, implementation of improved hygiene and biosecurity of hatcheries, improved farm biosecurity, introductions of vaccines, heat treatment of feed

Question 7

when did salmonella control-hygiene regulations and voluntary controls come into place? what was the biggest change?

Answer 7

1988-1998- lion mark scheme, voluntary scheme of hygiene and biosecurity standards coupled to routine surveillance, biggest cange was vaccination for hens

Question 8

when did national controls for salmonella come in?

Answer 8

1999 onwards. EU zoonoses directive 2003 and EU zooonoses regulation- set down requirements for national control plans (NCP), standards for biosecurity, controls and surveillance, for breeders in 2007/8, layers 2008 and broilers 2009. reduce salmonella in broilers to below 1%

Question 9

current salmonella surveillance in UK-NCP

Answer 9

broilers- 2 boot swabs per flock/house within 3 weeks of slaughter
layers- chick boxes and any dead chicks sampled, hens 2 boot swabs or pulled faeces at 22-26 weeks, then every 15 weeks
lab ID- accredited labs, MRSV agar and enrichment, serotyping and phage typing

Question 10

levels of salmonella in eahc type of chicken

Answer 10

breeder then most (0.07), then layers (0.17) then broilers (0.01)

Question 11

vaccination for salmonella?

Answer 11

started 1998, injeted killed bacteria followed by live attenuated vaccines delivered in drinking water
multiple for enteridits and typhimurium (injected to water spray), all layers and breeding vaccinated under NCP
production broilers not vaccinated (not eough of immune response before slaughtered)

Question 12

describe introductions fro high biosecurity at hatcheries

Answer 12

well designed and clean
indoors
barrier entry and vermin proof, vehicle wheels washed, concrete/gravel around buildings, effective ventilation
all in, all out system- allow disinfection between laying flocks and broiler crops
dedicated equipment and clothing between houses and avoid sharing equipment

Question 13

danish system

Answer 13

dsirobe, wash and don santitised clothing and boots before going into chickens, no vegetationagainst houses to keep out bacteria-carrying rodents and insects

Question 14

what is the most likely breakdown of biosecurity for campylobacter?

Answer 14

thinning birds - birds are overstocked then partially depopulated by teams of catchers who move between flocks
also fomite transmission via boots, clothing and flies may occur

Question 15

describe how intensive production, transport and processing is an oppurtunity for infection spread of campylobacter

Answer 15

caceca (and liver and muscle) infected during production
feed withdrawel and transport (up to 8hrs) - leads to stress and increases shedding from infected birds
automated plucking, eviceration and use of scald and wash tanks lead to frequent cross- contamination on the lines (200 birds a minute)
rapidly growing modern broiler breeds have low immune systems and more susceptible

Question 16

contact, exclusion zones and movement restrictions

Answer 16

less usueful in enteric bacterial infections in livestock (more for viruses e.g. avian influenza)
inc. bans on movement, gathering and exclusion zones around infected premesis
valuable tool in many viral infections -limited contact between animals
avian influenza- indoor housing and bans on poultry shows

Question 17

culling

Answer 17

remove infected population and reduce transmission
2001 FMD
welfare
not used for enteric but used to eradicate fowl typooid in 190s
outbreaks of S. gallinarum rrsult in flock culling
S. enteriditis often culled as not economically viable as eggs cannot be sold as table eggs

Question 18

role of welfare and housing in decreasing host susceptibility

Answer 18

better welfare and housing reduce stress and susceptibility - stress hormones increase faecal shedding in cattle and chickens
poor house design can increase shed in herds - common in pigs where housing is variable (faecal channeled)- plays a role in salmonella transmission

Question 19

selective breeding for resistance

Answer 19

genetic traits encoding for increased genetic resistance or immunity are known
chcikens have a stronger ssociation between genome and disease resistance as immmune system is less polymorphic than mammals
rapid generation time for breeding
broier breeding porgramme
detailed mapping and id of usueful traits

Question 20

what gene is edited and modiefied for resistance

Answer 20

CRISPR-cas9 is a bacterial defence mechanism
ca be exploited to edit a gene - remove one form and replace with another
edit defective genes but also to replace a gene where the gene product is a target in infection

Question 21

competeitive exclusion

Answer 21

CE= microflora to animals that excludes or competes with pathogens- occupying niches for colonisation or producing metabolites that promote gut health and inhibit pathogens (butyrate)

Question 22

probiotics

Answer 22

single bacteria species (lactobacillus), that promote gut health/inhibit pathogens

Question 23

prebiotics

Answer 23

feed additives that promote a good microbiome- frimucates that rpoduce butyrate, lower enterobacteriaciae

Question 24

what to CE and probiotics do?

Answer 24

promote immunological dveelpment in the gut. CEonly at intervals, probiotics need regular consumption

Question 25

what does use of antibiotics do?

Answer 25

prolonge levels on infection, ineffective if resistance and can exacerbate disase (e.coli toxins)

Question 26

bacteriophages

Answer 26

viruses that infect bcateria
often considered as a therapuetic in livestock or for post slaughter reduction in bacteria- but have specific host ranges and resistance may develop

Question 27

care in slaughter and processing

Answer 27

gut/faecal associated- processes in slaughte and processing should avoid gut/faceal contamination
hides - should be free of gross faecal contamination
care taken in removing the intestinal tract- to avoid spillage and cross contamination
challengin for poultry (200 birds/min)

Question 28

post slaughter controls

Answer 28

reduce levels on meat products by treatment of a carcass or porcessed product
more in US
gamma irradiation- also kills spoilage bugs (prolongs shelf life) as well as redcing food bourne pathogens.safety risks
only spices in EU
cholrination of chicken carcasses employed in US to reduce salmonella

Question 29

reducing camplyobacter

Answer 29

FSA (food standards agency)- targets but no underpinning legislation
target - from 27% to 10%
controls don’t address internal contamination of muscle or liver

Question 30

post slaughter camplyobacter control

Answer 30

legal and effective treatments
lactic acid treatment, rapid surface chilling (blast chilling), rapid steam treatment, washes in electrolsyed, ozonated or chlorinated water, UV treatment, bacteriphage treatment
some effect but ineffective for internal contamination and less successful than salmonella on farm controls

Question 31

future

Answer 31

EU- regulations and imports- allowing meat inport from US or cholirnation/irradtion etc.
genomics and gene editing
microbiome affecting the host control to enteric pathogens
welfare and management- to decrease disease transmission