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.

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 water-handling equipment without causing adulteration of the product.

  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

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;

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;

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:

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

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.

Disinfectant requirements in food-handling establishment:

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:

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:

temperature pH presence of organic materials composition of the surface

Problems with the disinfectants:

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.

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:

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

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

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

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.

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

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

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

Quaternary ammonium compounds are widely used in medical facilities, in food processing and food-handling establishments, and in agricultural settings.

Sodium hydroxide

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

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

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

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.

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

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;

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;

c) the institute performing tasks of vaccine-, medicine- and 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;

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.

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

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

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.),

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,

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,

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),

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.