Prevention of infectious diseases

Question 1

how is prevention of infectious disease best achieved

Answer 1

by eliminating or isolating the source of infectious organism, prevention transmission and reducing host susceptibility

Question 2

before prevention of disease, have to assess

Answer 2

risk
feasibility
cost
effectiveness

Question 3

risk assessment definition

Answer 3

deals with probability for potential disease exposure
use epidemiological studies or analysis of surveillance data

Question 4

information for assessing risk

Answer 4

history of arriving animal
contact with other animals?
lab tests and clinical exam
physical findings

Question 5

risk adjustments

Answer 5

require collection of information (environment, prevalence of disease, surgery site infections etc) about total population being monitored so that objective data can be used to help decisions about risk assessment

Question 6

feasibility

Answer 6

dependent on sociodemographic factors and operating needs of the facility
eg horse dealers may accept risk of stangles as the norm as they have too many horses to isolate and test
consider staff, time and finances

Question 7

cost

Answer 7

adequate staffing - understaffing leads to poor adherence of biosafety measures
trained personnel with appropriate supervision
single use equipment, cleaning, disinfection etc

Question 8

effectiveness

Answer 8

control strategies have to be elevated for effectiveness

Question 9

cost-effective models

Answer 9

used in making recommendations for prevention, control and population based vaccine programmes

Question 10

each source of infection can be

Answer 10

eliminated or isolated

Question 11

elimination

Answer 11

disinfection or sterilisation

Question 12

isolation

Answer 12

aim to prevent direct or indirect contact of ANY source of infection and susceptible animal until one of them no longer exists
inanimate source can be isolated for a period of time longer than longest known survival time of microorganism/shedding period
susceptible animal can be immunised in the meantime

Question 13

list primary sources of infection

Answer 13

1. sick animal
2. carrier animal
3. man - sick or carrier
4. animal products from sick or carrier
5. animal by products from sick or carrier
6. animal carcasses
7. wild animals (vertebrates)
8. arthropods

Question 14

list intermediate sources of infection

Answer 14

1. excretions and secretions of sick animals
2. excretions and secretions of carrier animals

Question 15

list secondary sources of infection

Answer 15

1. soil
2. water
3. air
4. food
5. contaminated objects
6. contaminated spaces
7. contaminated means of transport

Question 16

preventing infection - sick or carrier animals

Answer 16

can be isolated or killed and destroyed depending on disease and situation
animal can shed microorganism before signs appear (incubation), whilst sick, be subclinically infected or after recovery (reconvalescent shedding)

Question 17

incubation period

Answer 17

period between infection and occurrence of clinical signs of disease

Question 18

quarantine

Answer 18

isolation of healthy animal that may be shedding during incubation period as a means of prevention
have to know incubation period - length of quarantine should be longer than length of incubation period

Question 19

categorisation of sick and carrier animals

Answer 19

1. sick animal - need to be isolated and treated or killed
2. suspected of disease - disease confirmed or ruled out via diagnostic methods
3. suspected of infection - may have had contact with 1 or 2 group and may be infected but not skewing clinical signs yet. stay in this group for longest known incubation time then claimed healthy and moved to group 4 (be aware of subclinical infection)
4. healthy - animals that had no contact with animals from previous groups

Question 20

convalescent shedding

Answer 20

after resolution of clinical signs, in some diseases animal may be a carrier for a certain period of time or for life eg herpes
means that for some diseases, quarantining new arrivals may not be enough to prevent introduction of disease

Question 21

prevention infection from animal products

Answer 21

heat treatment is an effective way of killing most pathogens
if outbreak, procedures of decontamination/elimination of pathogen from animal products will depend on pathogen/disease
eg liquids like milk cannot be disposed without without inactivation of pathogen

Question 22

animal by products and disease prevention

Answer 22

they must be destroyed or pathogen in them inactivated if possible
may be really expensive or impossible - BSE

Question 23

carcasses and disease prevention

Answer 23

must be buried, burned, rendered or composted followed by thorough disinfection of premises

Question 24

wild animals and disease prevention

Answer 24

difficult to control movement. mostly controlled by
- depopulating wildlife (foxes for rabies)
- immunising wild animals (foxes PO vaccine for rabies)
- prevention of contact with domestic animals (eg for swine fever)

Question 25

arthropods and disease prevention

Answer 25

control of insects - repellents, destroying nesting places, covering slurry, keeping animals indoors during highest insect activity

Question 26

intermediate sources fo infection and disease prevention

Answer 26

intermediate sources depend on portal of exit from host and contaminate the environment creating secondary sources isolate shedding animal to minimise emergence of secondary sources importance of secondary source depends on capability of pathogen to survive under environmental conditions

Question 27

soil and disease prevention

Answer 27

depending on pathogen, soil can be decontaminated by resting (pastures), removing the surface, incinerating, heat treating and chemicals soil is a permanent source of the most resistant pathogens - eg Bacillus anthracis spores disease caused by pathogens found in soil prevented by injury prevention, hyperimmune sera use and immunisation

Question 28

water and disease prevention

Answer 28

water is a source when it becomes contaminated with pathogen from primary and intermediate sources or contaminated from reservoirs eg urine of rodents - lepto) pathogens concentrate in stagnant water prevention = not having too many animals drinking from same source and use clean water sick, healthy, carrier and suspected should all have own source of water small volumes of stagnation water can be decontaminated by cooking or chemicals (efficacy/practical?)

Question 29

air and disease prevention

Answer 29

in confined spaces, prevent transmission by keeping animals in separate rooms/buildings/barns good aeration of space can keep pathogen concentration down, ideally below infectious dose herpes, calici, corona and influenza can spread metres foot and mouth can spread for miles

Question 30

food and disease prevention

Answer 30

food can be contaminated by intermediate sources from animal involved in outbreak or excretions from wildlife contaminated in preparation or storage can be a source when meat from infected animal fed to other animal - BSE, Aujeskys decontamination sometimes possible sometimes not depending on pathogen

Question 31

contaminated objects, spaces and transport and disease prevention

Answer 31

cleaning and disinfection objects - dont share between animals premises - thoroughly mechanically cleaned and disinfected vehicles - thoroughly decontaminated between transportation of different group of animals

Question 32

transplacental transmission and disease prevention

Answer 32

house pregnant animals separately good husbandry there are many infectious causes of abortion - for some immunoprophylaxis is available (herpes) so vaccinate during gestation to lower transmission and abortion transplacental transmission by not be recognised immediately because newborn may appear healthy - BVD

Question 33

trade and disease prevention

Answer 33

trade is mostly regulated by law - supervised by vet inspector and origins of products have to be known

Question 34

intensive farming and shelter and disease prevention

Answer 34

all sources of infection present and all ways of transmission are supported non physiological living and bad husbandry make animals highly susceptible prevention = biosafety measures (all in all out), quarantining new arrivals and immunoprophylaxis

Question 35

extensive farming and disease prevention

Answer 35

best = quarantining and vaccinating new arrivals, only introducing animals from herds of known health status and testing for disease

Question 36

shows and competitions and disease prevention

Answer 36

set requirements for participants - government or organiser etc animal has to be vaccinated or tested for disease adhere to biosafety measures

Question 37

wars and natural disasters and disease prevention

Answer 37

post event, emergence of infectious disease is inevitable due to non existence biosafety, no surveillance etc, changed living conditions for people and closer contact with wild animals