Transcript DISINFECTION Disinfection

DISINFECTION
Disinfection means the operation, after thorough cleansing, destined to
destroy the infectious agents of animal diseases, including zoonoses
this applies to animals, premises, vehicles and different objects which
can be directly or indirectly contaminated by animals or animal
products.
Before applying disinfectant, thorough cleaning must be performed.
Sterilizing agents are used to produce total destruction of microorganisms
under controlled industrial, laboratory or hospital conditions. Heat,
chemicals and irradiation are the most commonly-used sterilizing
agents.
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Sanitizers combine cleaning and disinfection functions on
surfaces which are relatively free of gross contamination. They
are used to reduce bacteria to safe levels on food- or waterhandling equipment without causing adulteration of the product.
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Antiseptics inhibit the growth of microorganisms on living
tissue. They are used in wound treatment and in preparing the
skin for surgery. Antiseptics are usually the weakest and least
toxic of the surface antimicrobials.
General recommendations
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The choice of disinfectants and of procedures for disinfection
should be made taking into account the causal agents of
infection, the nature of the premises, vehicles and objects
which are to be treated.
Disinfectants and insecticides should be authorised only after
thorough tests have been carried out under field conditions.
The following should be considered:
 few universal disinfectants exist;
 whereas hypochlorite, which is very often used, may
be regarded as a universal disinfectant, its
effectiveness is diminished by prolonged storage
and it is therefore necessary to check its activity
before use. A concentration of 0.5% active chlorine
appears necessary for satisfactory disinfection;
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foot and mouth disease virus is easily
destroyed by a high or low pH but the
disinfectants used may be caustic or
corrosive in concentrated form;
tubercle bacillus is very resistant to
disinfectants and a high concentration is
required to destroy the organism, as well as
prolonged action;
no matter what substances are used,
disinfection techniques should comprise the
following:
 thorough soaking of bedding and litter as well
as faecal matter with the disinfectant;
 washing and cleaning by careful brushing
and scrubbing of the ground, floors and
walls;
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then further washing with the disinfectant;
washing and disinfecting the outside of vehicles; these
procedures will be carried out, if possible, with liquids
applied under pressure and the washing, disinfecting or
destroying of articles used for tying up the animals
(ropes, reins, etc.) should not be omitted;
if the suspected contaminating organism is exotic or has
zoonotic potential, or if the disinfectant has toxic, irritant
or corrosive properties, then protective clothing, masks
and rubber footwear must be worn.
The basic steps to be followed in
cleaning are as follows:
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all manure and bedding materials should be taken
away and disposed of in an appropriate manner
(incinerated, buried or ploughed into the earth)
earth and sand flooring must be scraped down to the
uncontaminated soil, all contaminated soil should be
removed and subsequently sterilized, buried or
ploughed under
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any material - such as wooden planks and
boards - which cannot be thoroughly
sanitized must be removed and incinerated
or buried
all interior surfaces (e.g. ceilings, floors and
walls) must be thoroughly cleaned with a
powerful detergent
all machinery and tools used in the removal
of soiling (e.g. manure loaders, shovels,
brushes and scrapers) must be thoroughly
sanitized.
The selection of detergents is important. A
product which could interfere with or
neutralize the chemical action of the
disinfection agent should not be used.
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Disinfectant requirements in foodhandling establishment:
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suitable for typical food factory applications;
non-toxic in the product;
safe for cleaning operatives;
non-tainting;
effective.
Disinfection of animal housing usually
involves the following steps:
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remove all animals, utensils and tools
scrub, scrape and flush away all gross organic material
using a cleaner/sanitizer or detergent compound
rinse thoroughly
apply the chosen disinfectant and leave this in contact
with surfaces for as long as possible
rinse thoroughly
leave the facility free of animals for an effective time
interval
Factors influence the efficacy of
disinfection:
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temperature
pH
presence of organic materials
composition of the surface
Problems with the disinfectants:
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carcinogenic
teratogenic
damage the environment (at least kill
beneficial microbes)
Causes of disinfection failure
Possible causes of disinfection failure include the
following:
 over-dilution of disinfectant during pre-mixing or
application
 incomplete or inadequate cleaning
 poor disinfectant penetration or coverage
 insufficient contact time on surfaces
 inadequate temperature and humidity while the
material is being applied.
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Failure can also result from inactivation or neutralization
of the disinfectant, due to the presence of residual
cleaning liquids which were not adequately flushed away
before the disinfectant was applied.
A common mistake is to select a product which is
ineffective against the contaminating organisms.
The entire process must be repeated if examination of
sentinel animals or laboratory tests on environmental
samples indicate that pathogens have survived the
procedure.
Needs in the field of disinfection:
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disinfectants which damage only the target
organisms
disinfectants which leave no harmful residue when
used in animal production or human food-processing
facilities
disinfectants which will not damage structural
materials, especially those used in aircraft, ships,
trucks and electronics
disinfectants which will not contaminate ground
water or pollute air
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disinfectants which are proven without doubt to be
non-carcinogenic and non-teratogenic
application methodology to assure uniform wetting of
surfaces to be disinfected without excessive use or
wastage of chemicals which may effect the
environment
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application of principles of risk analysis in making
decisions with regard to the need for application of
disinfectants and the methods of application, to
ensure (as far as possible) that no more
disinfectants are used than are actually needed
alternative disinfectants, such as synthetic
formulations, which are biodegradable, and harmless
to humans and the environment.
Chlorine disinfectants
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Chlorine has bleaching and germicidal properties and is
commonly used in disinfection, sanitizing and water
purification. In high concentrations, chlorine is used for
sewage treatment. Chlorine disinfectants and sanitizers
are readily available, inexpensive, have a broad
antimicrobial spectrum and present minimal
environmental hazards.
Chlorine disinfectants are very effective in the absence of
organic material. Other factors affecting the efficacy of
chlorine-based disinfectants are concentration, pH,
presence of natural proteins and presence of ammonia.
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Hypochlorites are still commonly used in animal
health programes. Hypochlorites have broad
spectrums of antibacterial and antiviral action. These
substances are corrosive, easily neutralized by
organic material and decompose readily. Chlorinated
lime — a hygroscopic white powder containing a
variety of calcium and chlorine compounds — is
frequently sprinkled in barnyards and on piles of
manure, the released chlorine serving as a general
disinfectant.
Iodine and iodine-based
disinfectants
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Many forms of iodine find common use in animal health and
food processing disinfection. Aqueous iodine (Lugol's solution)
or alcoholic iodine solutions (tinctures of iodine) are commonly
used as antiseptics.
Iodophors are disinfectants formed by combinations of iodine
with various carrier compounds. These release iodine in an
acid medium and have disinfectant properties which affect
bacteria, viruses and some spores. Iodophors are used for
general disinfection and cleaning bovine teat dips, and surgical
scrubs. Hard water and the presence of large amounts of
organic material reduce the activity of iodophors, but these
disinfectants can function effectively in the presence of traces
of organic material.
Chlorhexidine
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Chlorhexidine and its analogs are commonly
used at concentrations below 4% as skin
cleaners, teat dips and antiseptics. They are
also used for cold sterilization of surgical
instruments and for disinfecting equipment,
barns and buildings. Chlorhexidine has broad
applications in cleaning dairy equipment and
in aquaculture.
Quaternary ammonium
copmpounds
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Quaternary ammonium compounds are
widely used in medical facilities, in food
processing and food-handling
establishments, and in agricultural settings.
Sodium hydroxide
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in a 2% solution of sodium hydroxide is effective
against many viral and bacterial diseases. It has
been largely replaced with less corrosive and less
irritating modern disinfectants. However, in
emergencies sodium hydroxide can still be an
option, as it is readily available and extremely
effective.
It should be used with extreme caution and under
well-controlled conditions, due to the corrosive and
irritating properties, and potential dangers to the
environment and to workers.
Inorganic and organic acids
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The inorganic acids most commonly used in animal disease
control are sulfuric acid and hydrochloric acid. Both of these are
effective against FMD virus but are also highly toxic if
swallowed, highly irritating to the skin and eyes, and very
corrosive to metals. Thus these acids are used only in very
limited situations.
A number of organic acids with bactericidal and mild viricidal
properties have disinfectant applications in animal health and
food processing, as they are less toxic and less corrosive than
the inorganic (metallic) acids mentioned above. Acetic, citric,
lactic, formic and propionic acids are sometimes used in meat
and poultry packing plants, and in calf and pig barns. These
acids have also been added to animal feeds to reduce levels of
Salmonella contaminations.
Calcium oxide
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When mixed with water, calcium oxide (quicklime)
becomes lime wash, which has biocidal effects on some
bacteria and viruses but is not very effective against FMD
virus. Sometimes, quicklime is spread on the ground after
depopulation of infected premises, but the value of
quicklime under these conditions has been questioned.
Quicklime has also been used to retard putrefaction of
buried carcasses after depopulation. In these situations, it
probably has little direct effect on FMD virus.
Formaldehyde
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The natural form of formaldehyde is a gas. However,
formaldehyde is more readily available as a 40%
aqueous solution called formalin. Gaseous
formaldehyde is used for the fumigation of buildings,
rooms or vehicles which can be sealed. Fumigation
with formaldehyde is effective against most viruses
and bacteria, including Mycobacteria.
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Formaldehyde gas is relatively unstable and can sometimes
explode. For formaldehyde fumigation to be complete, the
temperature must be above 13 0C and relative humidity must
be above 70%. Spraying with hot water is sometimes
necessary to achieve these conditions. For fumigation
purposes, formaldehyde gas can be produced by oxidizing
formalin with potassium permanganate.
A 1-5% formalin solution is sometimes used to disinfect
buildings or as a prophylactic and therapeutic foot bath for foot
rot in sheep and cattle. The use of formaldehyde in disinfectant
situations is declining, due to the strong, irritant odour,
corrosiveness, fibrolytic properties and toxicity.
VETERINARY LABORATORIES
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a) public veterinary laboratory,
b) veterinary laboratory of a holding,
c) veterinary (clinical) laboratory.
Public laboratories are:
1. institutes and laboratories established or approved by the
Minister of agriculture, which belong into the frame of
state veterinary service and are divided according to the
fields of work (diagnostics, food-investigation and fodder
control):
 a) veterinary institutes functioning with national or
regional competence perform the diagnostic and
examinations for the prevention of epidemics prevention
connected with reduction in production, infections,
diseases, death of animals;
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b) the institute performing tasks of food examination
adopts the international methods of food examination and
makes them general, operates residuum, radiological and
toxicological monitoring systems (system of food control)
adequate to the international and national regulations,
carries out international and national reference laboratory
activities, also, performs institutional expert tasks
concerning similar activities of the laboratories of the
stations;
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c) the institute performing tasks of vaccine-, medicineand fodder examination: contributes to procedures of
permission concerning products of veterinary
therapeutics (vaccines, diagnostics, medicines) as well as
to fodder containing medicine as an expert institute;
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d) laboratories operated by the regional veterinary
authority: the task of the laboratories is making a
microbiological examination of food and fodder;
e) the laboratory of reproduction biology of the
authority of animal breeding, in the competence
provided in the law;
2. state veterinary or other laboratories, laboratories of
public bodies not listed in point 1 (e.g. universities,
research institutes);
3. non-state laboratories but which are approved and
suitable for performing a part of the tasks.
Laboratory activities establishing official decisions shall be
performed only by laboratories named in point 1.
Examinations connected with notifiable animal diseases
shall be performed, until the official confirmation, only by
laboratories named in points a) and c) of point 1.
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Should a suspicion of a notifiable animal disease
arises in the examination material of a public
laboratory as stated in points 2 or 3, the laboratory is
obliged to inform immediately the veterinary authority
competent in the region and to act as ordered by it,
and to send simultaneously the examined material to
the competent diagnostic institute.
Veterinary Laboratories of
Holdings
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Any organisation keeping animals or any economical
organisation may maintain a non-public veterinary
laboratory exclusively for exploratory surveying the
veterinary state of his own livestock, for development
of his own products, an inter-production or final
control and for other inner tasks.
Veterinary laboratories of a holding, shall not make
diagnostic examinations concerning a notifiable
animal disease, even as regards to their own
livestock.
Veterinary Clinical Laboratories
 Veterinary (clinical) laboratories are laboratories
making supplementary clinical diagnostic
examinations connected with veterinary servicing
activity, they function within the frame of veterinary
university hospitals (animal clinics), veterinary
hospitals, veterinary surgeries.
GENERAL RULES OF TAKING SAMPLES
FOR LABORATORY EXAMINATIONS
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To diagnose serious notifiable animal diseases and
to perform other special diagnostic tasks, apart from
some exceptions for very good reason, (e.g. rabies,
or sending large animals) it is advisable to send the
whole carcass (or sick animal) into the laboratory.
In case of diseases presenting risk to human health,
or in case of its suspicion a live animal may be sent
into a laboratory exceptionally and only under
circumstances preventing the spreading of infectious
materials during transportation.
1. The aim of the animal health laboratory examination
is the interpretation and completion of the diagnosis
of a disease, the epidemiological data, clinical signs,
results of production, by applying laboratory
instruments.
2. Their tasks are:
 finding the cause(s) of a disease (death), infection by or
freedom from certain agents of the livestock, animal
health factors influencing the production,
 animal health and food hygienic qualification of basic and
additional materials of food (raw-, semi-processed and
finished products),
 qualification of feedingstuff (basic materials,
concentrates, premixes, additive materials) with a view to
animal health and fodder hygiene.
3. The material of examination sent for laboratory
examination is the sample which can be:
 carcasses, parts of carcasses, organs of animals,
 aborted foetus and the foetal membranes,
 different fluids and secretion of animals (blood, urine,
excreta from the uterus, vagina or from the respiratory
tracts and other secretions, sperm, contents of the
stomach and the bowels, etc.),
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feedingstuff used for the feeding of animals, raw and
processed products and products submitted to
different procedures of animal, vegetable, mineral or
other origin intended for the feeding of the animals,
drinking water,
medicines used for treatment of animals, vaccines,
diagnostics, disinfectants,
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materials derived from the environment of the
animals, suspected of being infectious, objects
contaminated with poison,
food, raw, semi-processed and finished products of
animal origin, industrial raw materials (bone, hair,
skin, wool, etc.).
4. Laboratory examination shall be carried out only on
samples which are appropriate for the aims of the
examinations, and which arrived at the laboratory in
a suitable state for performing the examinations.
The examinations with the aim of diagnosing notifiable
diseases and diseases presenting risk to human
health must always be tried to carry out by using the
material sent into the laboratory.
5. Materials for examination with the aim of diagnosing a disease
shall only be sent to the laboratory by a veterinarian. However,
the public laboratories must accept the material for examination
without conditions in case of suspicion of a notifiable disease or
a disease presenting risk to the human health. In this case, the
institute must immediately inform the competent official
veterinarian. In case of ruling out the suspicion the official
veterinarian must be informed as well. The copies of all findings
must be sent to the competent station according to the origin of
the samples.
6. For laboratory examinations presenting the basis of
an official decision, in case of domestic farm animals
(food producing animals) samples shall only be
taken from animals which are marked individually
and permanently and/or identified by the
veterinarian. Only the laboratory results can be
accepted as the basis of an official decision/measure
from which the performed examination and its result
related to the individuals can be ascertained without
any doubt.
7. Samples with the aim of testing may be taken only
by a veterinarian or person having animal health
qualification in accordance with the safety
regulations.
Accompanying document to
material for examination
1. To all material for examination an
accompanying document must be enclosed.
To samples sent for different examinations,
separated accompanying document must be
enclosed, even when the samples are put
into the same parcel.
2. The accompanying document must include, according to the
type of the requested examination,
 name (marking) of the material for examination,
 place of origin, the holding, and the administrative location, the
name and address of the owner of the animal, in case of a
refundable examination, name and the address of the person
paying the costs,
 name and exact address (telephone, telex, fax) of the
veterinarian sending the samples,
 reasons, direction and aim of the examination,
 data of the anamnesis (results of the examination carried out on
the spot and the opinion based on it).
3. The accompanying document must contain further
data connected with the requested examination,
especially:
 information about samples sent to other laboratories
and the results of the examinations performed there,
 number, age and use of the affected animals (group
of animals), the keeping and feeding circumstances,
possibly their transport to a stable or to a holding,
their movement within it, their re-grouping,
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time of the occurrence of the disease, characteristic
clinical signs, the course of the disease, the number
of infected and dead animals, the daily mortality rate.
The changes found in the dissected carcasses or in
the emergency slaughtered animals (in case of
sending organs or parts of organs, the changes
observed in them and in organs which were not
sent),
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results of examinations performed previously,
treatments, if applied, name of the medicines used, their
dose, the time of their application, the results,
time of the preventive immunisation(s), name and dose of
the vaccine used,
status of the stock (infected, suspected or confirmed
freedom).
in case of zoonotic diseases (e.g. rabies), name and
exact address of the persons contributed in taking
samples, dissection or in transport of the samples, etc.