1. Failure to clean adequately: This is the most common failure. Leaving large amounts of organic matter in a building will lead to a carry-over of pathogens and disinfectants will be less able to kill them through the organic matter. Common reasons for this failure include inadequate pre-cleaning, not getting material out of inaccessible areas, and not cleaning ledges or under fixtures not closely attached to the floor.
Debris left in food troughs after washing
Obviously a difficult area is the slurry pit. If this is a deep pit it will usually not be drained, cleaned and disinfected, but if this is part of major disease eradication it will have to be done. Design and maintenance can have large impacts on the ease of removal of material throughout the building.
In previous articles we have covered the need to use heavy duty detergents and show why these are essential for good cleaning. This is demonstrated by introduction of a good detergent leading to much lower levels of piglet diarrhoea in many farrowing houses, something I have seen many times.
2. Recontamination: This is the second most common reason for failures in cleaning and disinfection. It can occur at any stage from cleaning right through to the re-introduction of pigs. A common failure is moving items or equipment that have not been cleaned, or poorly cleaned back into the house. This equipment can be recontaminated by splash back during its own cleaning. Recontamination via operatives is also common, especially on dirty boots or overalls. The use of a good foot dip outside each house will help control this, but boots must be clean when dipped. Animals can reintroduce contamination. This includes rodents, birds, cats and even pigs entering when they are not supposed to. Finally recontamination can also occur from inadequately cleaned and disinfected water or feed systems.
3. Incorrect use of agents: It is very common to find that detergents and/or disinfectants are used incorrectly. This may be due to the wrong choice of agent, for example using a disinfectant for control of a pathogen for which it is not active. Next is failure to dilute the agents at the correct rate. Operatives need to follow instructions, but some manufacturers supply dilution testing dip sticks which allow some certainty that the correct dilution is achieved.
Application of agents can also be a problem. They need to be applied at the correct rate. This can be checked by comparing calculated and actual usage for a known area. Surfaces must be evenly covered and adequately wetted. Contact time must be correct as per the manufacturers recommendation. Administration as a foam helps all these areas.
4.Other agent problems: Some agents are incompatible with water with high limescale contents and this will reduce their activity. Check this in problem areas. Disinfectant activity can be significantly reduced in low temperatures, especially if using Quaternary Ammonium – Glutaraldehyde mixtures, so if it is very cold use the right agent. Sometimes antifreeze is used to prevent disinfectant solution from freezing, and care must be taken that this does not interfere with activity. Detergents and disinfectants used must be comparable and not interfere with each other’s activity. Incorrect storage of agents can be a problem. Pay attention to manufacturers’ instructions and use by dates.
5. Resistance to disinfectants: There is mounting evidence that resistance to disinfectants can occur. This can be innate or acquired. Good examples of innate resistance are Parvoviruses which are highly resistant to many disinfectants including quaternary ammonium compounds, but not to formulated peroxygen based disinfectants.
A group of studies have looked at the development of resistance to disinfectants following repeated exposure to QACs, Glutaraldehyde/QAC mixtures, phenolics and a peroxygen based oxidising disinfectant1. They found that Salmonella exposed to disinfectants responded by increasing the efflux pumps in the bacterial cell. These are pumps which actively pump the disinfectant out of the cell and therefore, make it less susceptible to the disinfectant. Importantly, they found that Salmonella exposed to the peroxygen based oxidising disinfectant did not readily demonstrate this effect and that it’s not likely to be pumped out of the cell2. What this means is that repeated exposure to an oxidising disinfectant is much less likely to lead to acquired disinfectant resistance than other disinfectants
6. Biofilms and limescale: Biofilms are complex communities of bacteria and other pathogens in a polysaccharide matrix. They occur commonly on pig units, especially in water systems. Limescale deposits occur where water with high lime content is used and can occur on all surfaces exposed to this water. Both can interfere with good cleaning and disinfection by masking and protecting pathogens. It has been shown that E.coli bacteria in a biofilm are 3000 times more resistant to chloride within that water than free floating E.coli.
Although there are ways of reducing the formation of biofilms, these are not practicable on a pig farm. Control in a house is helped by dryness. If there is a problem, washing using a heavy duty detergent must be followed by an oxidising disinfectant to reduce them. Within water systems the use of a safe oxidising disinfectant is the main control.
If limescale is a problem it can be prevented by using treated water, but this is expensive at a commercial level. Where it builds up a rotation of acid and alkali detergents in washing is the best control measure.
7. Time, training and compliance: The final area where cleaning and disinfection fails relates to the people doing the job. First they must receive adequate training and instruction on how to do it. If you do not tell them how to do it how can you expect it to be done properly? Once staff are trained and doing the job it is necessary to check it is done correctly. Cleaning and disinfection is a repetitive tedious job and standards will fall unless adequately supervised. In theory checking with systems such as the RODAC or Lighting testing can be undertaken and used to give incentives, but this is rarely done on pig farms.
In full programmes wash the outside of buildings
The last and often most common cause of failure of cleaning and disinfection is inadequate time. This can be time to do the job, time for the agents to work or time to rest the buildings after cleaning and disinfection. Time may cost money but failure to allow time can cost much more!
To finish this series of articles, we can summarise that good cleaning and disinfection are an integral part of good health and production on a pig farm. As such they influence the costs of production on that farm. To be successful it is necessary to clean properly using heavy duty detergents. Then disinfect using appropriate disinfectants. The choice of agents must be correct, as must their application. Attention to detail is vital. Management and operators must be aware of why cleaning and disinfection fails and take precautions to prevent this.
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