Prevention of infectious diseases Flashcards
how is prevention of infectious disease best achieved
by eliminating or isolating the source of infectious organism, prevention transmission and reducing host susceptibility
before prevention of disease, have to assess
risk
feasibility
cost
effectiveness
risk assessment definition
deals with probability for potential disease exposure
use epidemiological studies or analysis of surveillance data
information for assessing risk
history of arriving animal
contact with other animals?
lab tests and clinical exam
physical findings
risk adjustments
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
feasibility
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
cost
adequate staffing - understaffing leads to poor adherence of biosafety measures
trained personnel with appropriate supervision
single use equipment, cleaning, disinfection etc
effectiveness
control strategies have to be elevated for effectiveness
cost-effective models
used in making recommendations for prevention, control and population based vaccine programmes
each source of infection can be
eliminated or isolated
elimination
disinfection or sterilisation
isolation
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
list primary sources of infection
- sick animal
- carrier animal
- man - sick or carrier
- animal products from sick or carrier
- animal by products from sick or carrier
- animal carcasses
- wild animals (vertebrates)
- arthropods
list intermediate sources of infection
- excretions and secretions of sick animals
- excretions and secretions of carrier animals
list secondary sources of infection
- soil
- water
- air
- food
- contaminated objects
- contaminated spaces
- contaminated means of transport
preventing infection - sick or carrier animals
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)
incubation period
period between infection and occurrence of clinical signs of disease
quarantine
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
categorisation of sick and carrier animals
- sick animal - need to be isolated and treated or killed
- suspected of disease - disease confirmed or ruled out via diagnostic methods
- 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)
- healthy - animals that had no contact with animals from previous groups
convalescent shedding
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
prevention infection from animal products
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
animal by products and disease prevention
they must be destroyed or pathogen in them inactivated if possible
may be really expensive or impossible - BSE
carcasses and disease prevention
must be buried, burned, rendered or composted followed by thorough disinfection of premises
wild animals and disease prevention
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)
arthropods and disease prevention
control of insects - repellents, destroying nesting places, covering slurry, keeping animals indoors during highest insect activity
intermediate sources fo infection and disease prevention
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
soil and disease prevention
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
water and disease prevention
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?)
air and disease prevention
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
food and disease prevention
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
contaminated objects, spaces and transport and disease prevention
cleaning and disinfection
objects - dont share between animals
premises - thoroughly mechanically cleaned and disinfected
vehicles - thoroughly decontaminated between transportation of different group of animals
transplacental transmission and disease prevention
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
trade and disease prevention
trade is mostly regulated by law - supervised by vet inspector and origins of products have to be known
intensive farming and shelter and disease prevention
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
extensive farming and disease prevention
best = quarantining and vaccinating new arrivals, only introducing animals from herds of known health status and testing for disease
shows and competitions and disease prevention
set requirements for participants - government or organiser etc
animal has to be vaccinated or tested for disease
adhere to biosafety measures
wars and natural disasters and disease prevention
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
