WO1998041243A1

WO1998041243A1 - Method of thermally reducing the contamination with pathogenic organisms in animal environments

Info

Publication number: WO1998041243A1
Application number: PCT/DK1998/000101
Authority: WO
Inventors: Klaus Nielsen
Original assignee: Micro Clean A/S
Priority date: 1997-03-17
Filing date: 1998-03-17
Publication date: 1998-09-24
Also published as: AU6611298A; EP0973555A1

Abstract

A method of reducing the contamination with pathogenic organisms associated with a material surface in an animal environment, the method comprising at least partially inactivating said organisms by applying onto said surface thermal energy initially contained in water vapour at a pressure exceeding 1 bar. The thermal energy is applied by releasing pressurized water vapour onto the surface whereby the thermal energy is derived from a transition of the state of the water vapour from the gaseous to the liquid state at a temperature in the range of 90-110 °C.

Description

METHOD OF THERMALLY REDUCING THE CONTAMINATION WITH PATHOGENIC ORGANISMS IN ANIMAL ENVIRONMENTS

FIELD OF THE INVENTION

The present invention pertains to the reduction or elimi- nation of pathogenic organisms in the environment of animals by thermally inactivating such organisms present in the environment of the animals such as on building material surfaces, including surfaces which are hidden, i.e. not readily visible or accessible, or on any other construction element surface.

TECHNICAL BACKGROUND AND PRIOR ART

The presence of animal pathogens including bacteria and viruses in the environment of animals represents a source of infectious agents which can cause diseases among the animals present in that environment and/or which may be transmitted from the animals to humans either by direct contact with infected animals or with the animal environment as such or indirectly by contamination of edible products derived from the animals. Examples of such food-borne, indirect route transmissions of disease from animals to humans are salmonellosis which can be derived from poultry, pigs and cattle, and infections with Listeria monocytogenes .

The currently available methods of reducing the contamination with pathogenic organisms in animal environments include mechanical and/or physical removal of contaminated matter from the animal environment and/or cleaning with water, optionally containing a detergent, which, if desirable, is followed by applying disinfection agents or biocidally active agents such as e.g. hypochlorite . It is also possible to obtain a reduction of the load of pathogens by applying biocidally active hot air or gases, i.e. a fumigation treatment . However, all of these current methods involve certain drawbacks which restrict their applicability: high pressure treatment is known to cause damages to the construction elements of the environment and the application of biocidally active agents involve health hazards to those applying them and their application may involve that the animals must be -^~ removed from the environment prior to the chemical treatment .

The climatic conditions including the moisture content in such animal environments or premises are frequently such that good conditions for survival or even growth of pathogens are provided which may result in the build-up of a high contamination level of such pathogens in these premises resulting in a substantial risk that healthy animals or humans become directly or indirectly infected.

A need therefore exists to provide an alternative method of removing and controlling contamination with pathogenic organisms in animal environments as a means of reducing the risk of transmitting diseases from animals to other animals or to humans which is effective, non-damaging to materials, non- toxic and cost-effective.

It is known to use steam generating apparatuses for conventional cleaning purposes in relatively clean indoor human environments of a normal hygienic standard including residential and industrial buildings such as e.g. food production facilities. However, it has not been suggested that the use of water vapour-derived energy provides a useful and effective means of controlling the presence of pathogenic organisms in animal environments which, relative to human environments, are substantially more dirty and soiled e.g. with faecal matter, soil and dust.

It has now surprisingly been found that an alternative, cost- effective and safe method of controlling such contamination of animal environmental structures can be provided which is based on applying a high amount of thermal energy derived from water vapour under pressure onto microbially contaminated material surfaces for a short period, i.e. seconds or few minutes whereby effective inactivation of pathogenic organisms is obtained without damages to the building materials and without any of the above drawbacks associated with presently used methods.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method of reducing the contamination with pathogenic organisms in an animal environment, the method comprising at least partially inactivating said organisms associated with a material surface in the environment by applying onto said surface thermal energy initially contained in water vapour at a pressure exceeding 1 bar, in an amount which is sufficient to at least partially inactivate said organisms.

DETAILED DISCLOSURE

The method according to the invention has been developed with the objective of reducing the risk of transmitting animal pathogens associated with animal environments to animals and/or humans.

In the present context, the term "environment" refers to any physical location to which animals may be confined, i.e. the term includes any building where farm animals are kept, such as stables, cowsheds, studs, barns and premises for keeping pigs and poultry. The term also includes the immediate animal environment within such buildings such as pens, pig sties, kennels, cages including cages for confining zoo animals, and fittings and devices used in the construction of such immediate environments.

As used herein, the term "animal" include mammals, birds, fish, reptiles and amphibian animals. In particular, the method according to the invention is useful in the environ- merit of farm animals including ruminants such as cattle, sheep and goats, pigs and poultry, but the method is also applicable in environments of fur animals including mink and foxes and environments of pet animals such as dogs and cats.

It is a widespread problem in the production of farm animals-- that pathogenic organisms are transmitted from infected animals via contaminated environmental material surfaces to other animals in the environment . This may cause the spreading of serious infectious diseases in a particular environ- ment to which a number of animals are confined. It is therefore a well-known hygienic measure in current animal husbandry to reduce the level of pathogen contamination using one of the above currently available methods.

Another serious problem associated with contamination of animal environments is the risk that pathogenic organisms which are also pathogenic for humans are transmitted from the animal environments to humans, which can take place via contamination of edible products derived from the animals or by direct contact with contaminated environments.

Several species of gram negative and gram positive bacteria, parasitic organisms, protozoa and viruses which are pathogenic for animals are also pathogenic for humans. Diseases which are transmissible from animals to humans are also referred to as zoonoses . Well-known zoonoses include salmonellosis which is the designation of infections caused by a large number of Salmonella species of the gastroenteritis group including Salmonella typhimurium, Salmonella enteri tides and Salmonella dublin . During recent years, the prevalence of animal farms infected with Salmonel - la species including poultry and pigs has been increasing resulting in an increased frequency of infections in humans. Other examples of such zoonotically transmitted bacterial diseases are infections with enteropathogenic E. coli , liste- riosis caused by Listeria species, tuberculosis, infections OJ C*J NJ t H H

LΠ o Lπ o LΠ O LΠ

P 3 Hi 3 H- if TJ CQ <! P TJ rt C-. td 3 μ. Tj TJ cn en rt P P P rt Hi 0 3 -, 0 H CO 32 if Φ if P P Φ Φ P μ- P Hi 0 μ- X P P PJ P TJ TJ Hi P TJ Hi if if 0 Hh μ- μ- Hi ft TJ μ-

0 P φ rt H{ H Hi eo μ- P Hi CQ P CO CQ ft φ Φ 0 μ- TJ φ φ μ- P CQ Φ rt

< rt Φ rt Φ en Hh μ- 3 Ω ^ φ 3 rt ft rt if Ω Ω H-¹ 3 Ω 3 μ- CQ M P μ- Ω p-

Φ 3 Hi tr 0 μ- P if P rt P TJ μ- if CD 0 μ- μ- P μ- Hi P if Φ 3 μ- P cn μ-

0 Φ μ- Φ Hi en Ω μ- P CQ H-¹ rt Φ C CQ φ Φ φ Ω Φ P P TJ 0 Hi μ- Φ Co if Hi rr P rt Φ φ Ω P φ Φ μ- H{ φ en en CQ P 3 μ- P rt Hi P Φ 3 φ en rt μ- if μj μ. if φ Φ P P- CQ CQ Hi CD P tr 0 3 H-¹ 0 • CQ P < μ,

P. tr 0 CQ P Φ P 3 CQ P < • Φ μ- μ- ≤ tr P <! P Φ < P μ- P α CD o P. rt Ω Ω P P <! CQ μ- 0 CQ μ- Ω if tr ^ Hi Φ Φ • μ- H-" P TJ

Φ rt Φ 0 φ *< Hi μ- ^ P H Hh TJ P μ- P Φ Pi CQ P CQ P Ω ft TJ φ P- rt

P if P μ, 3 Hi Hi CQ P μ- if Ω Ω rt μ- P • CQ Ω P P 0

Ω Hi φ 0 P P 0 P rt CQ TJ μ, tn P ' rt if TJ P Hi μ- μ- O μ- rt rt o 0

Φ P- Ω P Hi P Ω P P Hi - P P TJ Ω Φ Φ H{ 0 P 3 tr rt Hi P if P 0

P μ- 0 Ω Ω P- Φ 3 ^ O rt rt φ rt P Hj Φ rt Hi P ^■ ; if 0 rt

Hi Hi φ φ μ- TJ if 0 Ω Φ Hi μ- a 0

< φ 0 <! 3 cn p- φ Φ μ- P CQ if T n μ- φ P μ- Hi 0 P CQ P P 0 Hi μ- Hi φ P φ φ Φ CQ • CQ P P Φ P ^ c

Hi Ω μ- tr rt P Hi rt P rt Hi CQ ^ φ μ- rt P H-¹ CQ TJ if CQ Hi P rt μ- CQ

0 rt P Φ P if P Hi Φ < Φ CQ P TJ if rt P P • if TJ Φ * φ μ- 0

P cQ rt 3 TJ P Ω Hh cn 0 P CQ H-¹ P en 0 • P P P * P

< μ- ^ P ft TJ Pi μ- CQ P < ^><: H-' ^ Pi Ω P tr CQ

3 ^ => μ- Φ TJ 0 P rt P P TJ φ rt Φ P Hi if P Ω μ- μ- Ω CQ P CQ P" φ H 3 if Φ H- rt Ω O 3 o φ

P P 0 Φ P 3 o μ- CO Φ P Hi rt P- TJ 0 Ω 0 if P rt P if rt Φ Hi Φ rt Ω rt Ω P rt μ- TJ p, rt P P < Φ φ CQ μ- Hi Φ Φ μ- tr CQ tr P- cQ rt CD μ-

P Ω rt Φ Ω Hi P Hi 0 CQ μ- 3 trj Ω Φ φ Hi rt Φ Ω Φ P if μ, Φ

Φ if tr H; μ- Φ P Hi Φ Hi 0 μ- P CQ rt P Φ μ- rt Φ ft 0 Hj P 0 CQ en Φ P 0 P P Ω rt CQ P P Hi Φ μ- - if P P P Φ P if P TJ μ- μ- Pi en cn cn μ- tr rt *» rt rt Hi ^ H-¹ P 0. CQ Ω φ μ- <! iQ Hi φ P- H{ cn cn TJ

P μ- μ- H-¹ 3 μ- Φ μ- if P Cb CD TJ 3 μ- • Hi μ- Φ ?r 3 Φ to

Hi tr P P- μ- P P 0 φ Ω <l CQ rt μ- Hi Hi μ- P Hi 0 Φ 3 rt CQ CQ Φ Ω rt

Hi < μ- Ω Ω 0 P rt μ- TJ to CD P 0 0 P μ^j 0 tn Hi 3 Φ μ- φ o P μ- P

P φ Φ P Hi 0 rt 3 en Hi Φ rt μ- Ω Hi ft <! P 0 0 rt 0 P Hi μ- P. Φ T

Ω P Q 0 0 P P P Ω Hj μ- μ-¹ 0 Φ TJ 3 TJ <! if P rt P μ- cn tr

Φ _*—. rt tr H{ P- μ- z rt P CQ μ- $> PJ P P ESJ P P Φ Φ μ- Φ 0 en μ- P . ^

CQ 0 μ- 3 μ- CQ μ- 3 if Φ P Φ Φ T P- P 0 rt rt P < cQ P- P- 3 P rt cQ μ-

. P 0 P P P rt 3 Φ Hi P, CQ en rt CQ φ μ- P μ- if rt Φ cn 0 Φ rt if 0 rt P rt P μ- φ rt μ- 0 TJ 3 H-¹ 0 0 Hi CQ μ- Hh rt Φ Φ rt o tn Φ Φ μ- 0 P- if P CQ rt μ- 0 φ tς P P CQ P - O P P if Hi 0 0

0 H^ μ- Hj CQ CQ P μ- Φ H-" if P 0 Ω CD CQ Φ P Hi Ω P 0 Φ 0 cn μ- H{ 3 en P Hi CQ μ- P Ω n μ- a en TJ μ- P α ft r P P P- P P P o

Φ P 0 CQ rt P rt 0 φ o . φ P CQ Φ if P P μ- P <! c

< en CQ S TJ Φ μ- Ω φ P c CQ T Ω Ω Hi Φ P 3 μ- μ- μ- H{ CQ

Φ P P CQ rt 0 φ H-¹ rt 0 μ- P. CQ tr td μ- Ξ Hi CQ φ P CQ 3 Hi φ

Hi Hi μ- if Hi Hi *< P Hh P φ Ω μ. X φ P ^* Ω 3 P P 0 P- CQ

Hh rt P 3 μ- CQ Φ Hi CQ P μ- P CQ Pi μ- 0 φ 0 μ- < cn P P P TJ

P P P 3 Φ μ- P CQ rt <! φ Hi TJ P c 3 φ Ω P rt Ω CQ μ- CQ 3 Ω φ μ- Ω tr P- P < rt Ω μ- φ Ω 0 Φ CQ en TJ P if P- p- ΪY HS μ- Φ Cb Φ rt Ω rt Φ H-¹ ^ Φ rt Ω P rt Hi ft 0 Ω μ- P P μ- 0 rt 0 P Hh μ- P μ- μ- en φ Ω P μ- Φ P rt μ- P CQ φ P- P Ω rt P- 0 " P P CQ rt 0 φ

2^> 0 P P CQ rt < ft φ CQ TJ en ^><; P μ- Hh φ 3 rt H φ P CQ μ- P Hh <! TJ CQ CQ μ- μ- μ- if P CQ Φ TJ P 0 μ- φ P" P 0 _^

P 0 φ en Hi μ- Hj P Φ P μ- Ω 0 P < P CQ TJ Ω P Φ P en Hi μ-

H-¹ P- Hi Hi 0 0 rt tr Φ CQ P P Ω P μ- Hi Hi H- tr en 0 P rt μ- CQ φ P μ; μ- TJ if H Ω CQ Hi P Hi φ P Hi Φ P P CQ Hj P CD tr rt rt P 0 P Φ Φ rt rt • Φ 3 P Φ CQ P cn P Z Φ Hh P rt P CQ μ,

Φ t H Q Ω CQ if CQ 0 CQ Ω ^ P μ- CQ Ω if CQ rt Hi φ Hi μ- Φ CQ φ Φ Ω P ^ Φ TJ P μ- rt μ- rt 0 Φ 0 Hi -^• 0 P 3 P 3 P μ.

P P rt μ- ft P μ- 3 φ P Hj ^ if 3 <! Φ P P Φ P rt Hi μ- Hi if CQ 0 P Φ Φ μ- P en Hi μ. 0 P P H-¹ P P 1 CQ P P P cn CQ H-¹

ω t t H H o LΠ o LΠ σι cn cn Ω tr P rt rt 0 Φ P

P P P P. rt rt CQ Hi φ

Φ φ rt Φ μ,

Hi Λ CQ

P 0 P P rt rt Hi Ω μ- 0 ft Hj 0

P rt μ- Φ Cb if 0 i rt Φ P rt

Φ rt if

3 52 3 0 P

TJ P P rt

Φ rt rt Hi

Hi Φ Φ Φ μ-

P Hj Hi 3 P rt μ- 0

P < P <! Ω μ P H-¹ Φ P φ TJ CQ CQ

0 Ω Φ μ- P P 0

P Hi CQ < o

Φ Hi rt Hh CQ Hi if Hi P μ- tr

Φ o Ω P μ-

3 if cQ

Hj CQ i

P rt rt ~. Φ

P if 0 P

CQ φ Hi

Φ Φ H-¹ cn

CQ X 0 P

0 P TJ 0 Hi

Hi en 0 Hi Hi φ CQ μ- P

0 φ P Ω o P CQ φ en ft CQ en

H if μ> rt Φ 0 o 0 Hj μ- o 3 rt n rt μ- ft if Ω tr

Φ z

Hi φ μ- o h-¹ tr tr H-" μ- μ- P

& P μ- CQ

P * H Φ μ- P- P ; μ- Φ

P Hi cQ P

H

μ- rt HH φ -2 P it-. ft en 0 H P Hi P rt if Hi 3 P P P rt μ- < rt TJ tr rt rt tr <

P 0 rt X P μ- TJ o 0 if P P P tr P i tr P if Φ o P CQ tr P P P HJ Φ P ^ P

N φ τ3 P

P Ω ft rt TJ P Φ Hi Φ P Φ < Φ P μ- φ TJ tr Φ P P TJ

Ω rt if Φ φ Hi P l_J. H-¹ Hi 0 ; CQ P Φ P N 3 rt rt rt 0 μ- en rt ? μ- 3 0 P rt if P CQ Hi Φ Hi 0 Φ Hi P z P Φ en Hi rt cn Φ O 0 tr P P en μ- Ω φ P Ω μ- Φ CQ CQ CQ P P cn P Ω if φ tr rt P P P Φ P 0 P φ Hi CQ P P rt P P Hi Ω

<! ft rt H-¹ \ P Φ Φ Φ 0 P P P cn rt Hi TJ rt Hi Q 0 μ-¹ P 0

P μ- φ 0 Φ P P Φ Ω CQ φ Hh tr CQ Ω ? P Φ HJ H-¹ Hi rt 0 φ cn Ω Hi rt P < Hh 3 P CQ CQ 3 Φ μ- Φ Hi μ- φ P Ω s2 rt 0 φ 0 0 Hi 3 Ω P- P P- μ- < φ T ' — _ t CQ μ- Hi P H Φ tr 0 if φ μ- μ- rt Hi < Φ 0 φ 0 P P

0 φ P to Φ tr Ω \ 0 P Φ 0 μ- Hi 3 rt 3 μ- 3 P 3 P P P CQ Hi P

P P Hi P P 3 cn Hi μ- Ω rt H rt Hi Ω P φ tr φ Pi P φ P rt μ- Ω Ω rt tr tr P <J t φ P rt rt if o 0 Ω CQ P • φ μ- 0 rt < CQ P cQ P 0 Φ

0 μ- Φ P rt if μ- ^_^ Ω LΠ tr μ- Φ to Ω 0 rt P 3 Hh 0 P Φ μ- P P

P 0 Φ Hi P Φ P CQ • rt φ < if TJ 0 P tr H Hi φ P H-¹ CQ P CQ Ω <; 52

P P Hi P Q Φ cn tr Φ Hi P Hi H-> P rt Hi Ω TJ rt Φ P P rt 3 P •« 0 Φ μ-

P Φ rt Ω > o Φ φ P Hi 0 O ft P P P μ- CQ H-¹ 0 Φ Ω Z P P rt

P μ- Hh μ- P en P Φ P • <; φ μ- CQ P φ 3 φ μ- P Φ Hi P if P en <! μ- tr

Φ CQ 0 0 P Ω μ. Φ 3 CQ μ- r-¹ P P tr Ω P P 0 0 rt P rt P φ φ

< P Hi CQ Ω P P 0 P Hi tr Φ H3 Pi μ- rt φ Φ CQ Φ ^ en P N P CQ P Φ Ω P P rt

Φ if P 0 P P P P cQ 0 if φ rt Hi CQ P φ CQ N 0 CQ Hi if ft rt tr

P μ- Pi P Φ P Q ^ P- 0 φ Hi μ- • μ- 0 tr Hi Hh rt μ- μ^j Φ

CQ tr ft tr φ Φ Φ μ- Hi CQ φ P Hi rt Hh Φ 0 o Φ H-¹ 0 if P P 0 ^

P tr ft 0 φ P φ <! cn P 3 φ P en O P Hh Hh rt Φ Φ P TJ P 3

P tr P 3 μ- P \ 0 TJ φ μ> Hi μ- • rt Hi if Hi P Φ tr X 0 P P- TJ P tr Φ

Pi "< P rt φ P P 3 Ω Hh TJ P o Hi rt if H-¹ P P- P rt h-¹ φ μ- tr rt φ P H-¹ Φ rt rt P Φ TJ TJ 3 μ-¹ rt o Φ P H Φ Hi ^ tr <! if Φ tr rt μ- Hi HJ if μ- Φ μ» rt Hi TJ to μ> μ- o Ω tr if Φ Hi P Cb φ 3 rt P P P <! P 0 ii Hi rt t Φ ^_^ Φ 0 ft H-¹ Φ Hi Ω tr μ- P φ φ P φ μ- CQ TJ rt P TJ

Hi Hi if o Φ -2 μ- - en μ> Hi ft Φ P Φ Φ Ω rt CQ P P tr P Hi P TJ TJ φ Φ φ o Hi μ- φ φ o O 0 TJ P μ- P μ- 0 rt μ- 3 Φ φ en 0 0

CQ Ω O Hi rt P- P Ω o rt rt Hi TJ μ. CQ < TJ Φ CQ H; N • P P rt H- CQ φ P μ- Hi

P ft rt Φ if P 0 tr H Hi Φ Φ μ- Hi P Φ Φ N CQ rt tr Φ CQ cn Hi Φ μ- tr Ω z cn φ O ft Φ CQ P o Ω 0 Pi H-¹ - Φ Φ 3 P P- rt

P φ μ- rt P if P P 0 rt •- if CQ CQ O cQ <! P P Φ rt Hi φ Hi Ω CQ tr

Hi φ H{ . φ 3 Ω P tr μ- o φ CQ P Hi μ- cn CQ P Z μ- P- P Φ 0 Φ rt Φ

3 Φ 0 Ω P 0 if φ P o P Hi rt C μ- 3 Φ Z if P Φ rt ~ 3 P O cn -2 P • Hi P P Φ <! o if Hi Φ H if φ P rt 0 μ- μ- H-¹ CQ CQ TJ Φ μ-

P μ- if P P P CQ tr Φ Φ Φ Φ Pi c 0 P Φ Ω μ- TJ Hi Hi rt P

Hi rt P t μ- rt cn \ P P s: P <! σι P 3 H-" if rt Hj 0 Hi μ- P if <!

Hh if rt ft Ω <; Ω μ- rt • rt H-¹ P o -2 Z rt TJ ft φ 0 φ Hi 0 en rt φ φ

P Hj O P G P 3 μ- μ- Φ P μ- if Hi P tr P P- <l φ μ- P

Ω Hi Φ P O Ω TJ Hh rt t C 0 P <! < H-¹ ft rt Φ 0 0 rt φ TJ Ω tr μ- P 3 rt

Φ Φ P o 0 \ μ- P CQ φ φ μ- Φ if < Hi TJ 0 < φ Pi P CQ P μ- cn CQ rt TJ -3 P P Φ CQ P •- rt Hi P μ- Ω P Hi P P P φ ft 0

•• P 3 Hi ft Hi P Φ Φ CQ 3 CQ 3 Hi 0 0 b ft P P 0 P- TJ rt Pi Ω P Φ P

Hi Φ φ μ- φ Φ P Ω rt φ Φ φ 3 rt N Φ tr P Pi TJ P 0 μ- 0 TJ Hi

P Pi P CQ CQ P CQ Hi cn ^ 3 if P CQ P CQ P tr rsi φ φ H| Ω P P -2 P TJ μ-

CQ rt CQ rt Φ CQ rt P Φ P P P ^>< φ rt tr Hi μ- rt Hi cq μ- rt P P rt

CQ rt P P P "< μ- rt CQ Ω CQ en Hi φ if <! Φ cn P rt P Hi tr

P 0 P Hi CQ 0 Φ μ> P Φ

Hi 3 if P cn Φ P rt rt rt TJ Ω if μ- P Φ

3 Ω Φ φ Hh 0 σ Ω Hi φ Ω CQ Ω P Ω 0 TJ < 0 φ " Hi 0 P rt en μ- 3 Ω P. P Hh H μ- rt P P tr tr μ- H-¹ Hi P 0 P 0 μ^j Φ φ μ- Φ φ P P z

P μ- 0 μ- P rt P P if P CQ 0 rt Φ 0 P Hi - a ^>< CQ H-ⁱ Hi en Hi P cQ Ω Hi P P tr μ- P P o P P P P rt N Hi μ- Z CQ CQ Φ . Hh rt

Hi ft 0 P tr μ- Pi cn μ- CQ if P tr N φ rt 3 P P ^ Ω 0 P Φ

^>< 0 μ- P cQ o P P P Pi μ- φ TJ P- tr P rt Hi rt H{ H Ω Hi tr P P rt P Q μ- μ- μ- φ P Φ φ P ^ Φ Φ Hi P Φ

P- μ- cQ ft cn rt rt tr P CQ Hi en rt H{ μ- P CQ

P P n tr Φ 0 tr ! Ω

Φ Φ Φ P

to an ability of the condensed vapour to penetrate into cracks and fissures on such surfaces.

In accordance with the method of the invention, the distance between the vapour outlet nozzle element and the contaminated surface to be treated should be relatively short, such as in^~ the range of 0-10 cm. In preferred embodiments the distance should be less than 5 cm and in more preferred embodiments the vapour outlet is in contact with the surface.

The appropriate period of time where the vapour is applied to the material surface depends on several factors, including the level of microbial contamination, the type of material and the surface structure hereof and the initial temperature of the vapour. Evidently, a rough surface may require a more prolonged treatment than a smooth surface, which treatment, however, should not be prolonged beyond the point where damages of the material in question occur. In suitable embodiments of the invention the thermal energy is applied to the surface for a period of time which is in the range of 0.01-60 sec/cm² including a range of 0.125-10 sec/cm². However, it is envisaged that particularly contaminated or particularly rough surfaces may require a more prolonged treatment, i.e. in excess of 60 sec/cm².

Preferably, the thermal treatment parameters should be selected so as to inactivate or kill essentially all pathogenic organisms. Accordingly, the present method is preferable one which results in killing of at least 50%, preferably at least 75% and in particular at least 90% of one or more pathogenic species initially present on the material surface .

An example of a practical means of determining the efficacy of the present thermal treatment is the application of a predetermined amount of suspension of a pathogenic organism such as a Salmonella species or appropriate dilutions hereof onto a given surface e.g. providing areas of the surface being

to add to the water in the vapour generating apparatus one or more additives which can contribute to the inactivation of fungal materials. Such possible additives include as examples, surface active substances including soap and deter- gents, environmentally acceptable biocidally active compounds, alcohols and salts.

The invention is further illustrated by the below non- limiting example .

EXAMPLE

Reduction of Salmonella contamination of surfaces

Surfaces of concrete, wood and metal, respectively were contaminated with suspensions of two species of Salmonella, i.e. S. typhimurium and S. enter i t ides . Each suspension was spread in undiluted form and as 10^"2, 10^"4 and 10^"6 dilutions, respectively onto the surfaces to provide calculated contamination levels of 10⁶, 10⁴, 10² and 10° per cm², respectively.

The above surfaces were subjected to a contamination reduction treatment as described above and the surfaces were then examined for presence of surviving Salmonella organisms.

From each material surface triplicate cotton swab samples of each contamination level were taken. The samples were examined qualitatively for the presence of surviving Salmonella organisms using a modified ISO 6570 method comprising as the essential steps, a pre-enrichment step in buffer prior to a selective growth step in Rappaport medium, followed by selective culturing on Rambach agar plates. Colonies which on this medium were suspect for Salmonella were subjected to conven- tional confirmation procedures. The results are summarized in the below Table 1.

Table 1. Reduction of Salmonella contamination. + indicates positive finding of surviving bacteria, 0 indicates that no surviving organisms could be detected

No. of Salmonella per cm² 10^< 10 10' 10

Concrete

S. ty 1 0 + + + S. ty 2 + + + + S. ty 3 + 0 + +

S, ent 1 + + + 0 S. ent 2 + + + + S, ent 3 + + + +

Wood

S. ty 1 0 0 + + S. ty 2 0 0 0 0 S. ty 3 0 0 0 +

S . ent 1 0 0 0 0 S. ent 2 0 0 0 0 S. ent 3 + 0 0 0

Metal

S. ty 1 + + 0 0 S, ty 2 + 0 0 0 S. ty 3 + + + 0

S, ent 1 + + 0 0 S. ent 2 0 0 0 0 S. ent 3 + 0 0 0

No . of samples without Salmonella 7/18 10/18 10/18 11/18 Abbreviations: S. ent: Salmonella enteri tides, S. ty. Salmonella typhimurium

It appears from these results that the present method is capable of reducing the level of contamination with pathogenic species of Salmonella on commonly used building materials in animal environments. Thus, in 7 out of 18 samples collected from surfaces at the highest contamination level no surviving Salmonella organisms could be detected.

Claims

1. A method of reducing the contamination with pathogenic organisms in an animal environment, the method comprising at least partially inactivating said organisms associated with a material surface in the environment by applying onto said "^" surface thermal energy initially contained in water vapour at a pressure exceeding 1 bar, in an amount which is sufficient to at least partially inactivate said organisms.

2. A method according to claim 1 wherein the thermal energy is applied by releasing pressurized water vapour onto the environmental material surface whereby the thermal energy is derived from a transition of the state of the water vapour from the gaseous to the liquid state at a temperature in the range of 90-110┬░C.

3. A method according to claim 1 wherein the energy applied to the environmental material surface is at least 10 joules/cm²/sec .

4. A method according to claim 3 wherein the energy is applied to the environmental material surface by releasing the water vapour to the surface at a distance from said surface which is at the most 10 cm.

5. A method according to any of claims 1-4 wherein the thermal energy is applied to the surface for a period of time which is in the range of 0.01-60 sec/cm².

6. A method according to claim 1 wherein the material surface is selected from a roof construction surface, a ceiling, a floor, a wall surface and a surface which is not immediately accessible .

7. A method according to claim 6 wherein the building material is provided with a surface covering including a covering comprising an organic substance.

8. A method according to claim 1 which results in killing of at least 90% of pathogenic organisms initially present on the material surface.

9. A method according to claim 1 which comprises as a pre- treatment of the environmental building material surface a step whereby contaminated matter is at least partially removed from said surface .

10. A method according to claim 1 which comprises the further step of removing from the thermal energy treated building material surface droplets of condensed water vapour entrapping pathogenic organisms.