Acids (acetic acid, citric acid) — Acids are used to precipitate proteins. They can be caustic and toxic if they reach high concentrations in the air. Their activity is dependent on the pH of the substances they come in contact with. They have limited use in most swine cleaning and disinfecting programs.

Alcohols (ethanol, isopropanol) — Alcohols denature (break down) proteins and are non-corrosive. They are highly flammable and need to be in concentrations of 70-90% to be effective.

Aldehydes (formaldehyde, glutaraldehyde) — These chemicals are non-corrosive and denature proteins. Formaldehyde is carcinogenic, but glutaraldehyde is considered much safer for humans and animals. Glutaraldehyde can be slightly effective in the presence of some organic material.

Alkalis (lye, ammonium hydroxide) — Alkalis saponify (make into soap) fats in enveloped organisms. Activity increases with temperature. They are very corrosive.

Biguanides (chlorhexidine) — Biguanides alter cell membrane permeability. They are easily inactivated by detergents and hard or alkaline water. They are toxic to fish, but relatively nonirritating to tissues.

Halogens (chlorine or iodine compounds) — Halogens denature proteins but loose potency with time, organic matter, sunlight and some metals. Bleach (sodium hypochlorite) is probably one of the cheapest and most common disinfectants used. Iodine compounds can be irritating to skin at higher concentrations. Both iodine and chlorine are readily inactivated by organic material.

Oxidizing agents (hydrogen peroxide, peracitic acid) — Oxidizing agents denature proteins and lipids, are moderately corrosive and can be irritating at higher concentrations.

Phenols — Phenols denature proteins and change cell membrane permeability. They have a milky or cloudy appearance when added to water. They are usually not effective against non-enveloped viruses, but are effective in the presence of organic matter, and are therefore good options for foot baths; they have residual activity.

Quaternary ammonium compounds (quats) — Quats also denature proteins and change cell membrane permeability. They are usually not effective against non-enveloped viruses, are toxic to fish and inactivated by organic matter, detergents and hard water.

These general characteristic are helpful in understanding the differences between products. Product labels should always be read to better understand the specific characteristics or effectiveness of a particular product, which may be different than the general characteristics we have described here.

One other important part of the disinfection process is to know your target organism. As a rule of thumb, different classes of disinfectants are more likely to be effective against a particular type of pathogen. Bacteria can be grouped into gram-positive or gram-negative bacteria based on the ability of the organism to pick up special staining. These staining characteristics relate to properties of their cell wall, and therefore can be used to decide which type of products may work best for the different groups of bacteria.

Table 1 identifies some of the common bacteria of interest in swine operations as either gram-positive or negative. In regards to viruses and disinfection, classification is based on whether they have an envelope or not. Generally, non-enveloped viruses tend to be hardier, survive longer periods in the environment and require special disinfectants to be effective.

Table 2 (page 35) helps organize some of the common swine viruses into categories as well as identify them as either being a DNA (deoxyribonucleic acid) or RNA (ribonucleic acid) virus. Although from the perspective of cleaning and disinfecting this characteristic is not relevant, it is important from the overall perspective of biosecurity. RNA viruses tend to mutate often, and therefore are more difficult to control through vaccination compared to DNA viruses. The porcine reproductive and respiratory syndrome (PRRS) virus is an example of an enveloped RNA virus. This means that it should be relatively easy to disinfect (envelope) and it mutates often (RNA).

On the other hand, porcine circovirus Type 2 (PCV2) virus is a DNA virus (low mutation rate) and does not have an envelope (hard to disinfect).

The Center for Food Security and Public Health at Iowa State University has free resources on their websites on disinfectants at: www.cfsph.iastate.edu/BRM/disinfectants.htm. Table 3 lists the general characteristics of the different classes of disinfectants. Tables 1 and 2 can be used to select the target pathogen. Then refer to Table 3 to decide what class of disinfectants you want to use.

For example, if PRRS is your target pathogen (enveloped virus), then you would know as a general rule that the aldehyde class of disinfectants would be a better choice than phenolics or quats. Companies may add specific pathogens to their labels if they have done laboratory testing (standard test established by EPA) to demonstrate effectiveness of their product against that particular pathogen. The three tables serve as general guidelines; fully read the specific labels for all products to be sure they are effective against your target pathogens.

Generally, differences in pathogen strain don't change the organism's susceptibility to a particular disinfectant. A good example of this is the novel H1N1 influenza strain. The Centers for Disease Control and Prevention recommend that any product labeled effective against influenza (avian, swine or human) viruses could be used to disinfect surfaces.

There is also no evidence that swine pathogens develop any type of resistance to a particular class of disinfectants, as is the case for some bacteria and antibiotics. Therefore, rotating disinfectants is not necessary unless rotated to broaden the scope of target pathogens.

Another key element of the disinfection process is contact time. In general, most disinfectants need at least 10 minutes of contact time to be effective. Read the label to make sure proper contact time is provided.

Inadvertently, farrowing processing crews are probably the biggest violators of this rule. For effective disinfection of processing equipment, each operation should have two or three different sets of equipment, so that while one set is being used, the other sets are having plenty of contact time for the disinfectant to do its job.

Many of today's disinfectants are labeled for use in foaming equipment. Foaming has two great advantages. First, it allows one to visualize where the product has been applied, assuring a more even and complete application. Second, it dramatically increases contact time of the disinfectants with the different surfaces, especially vertical surfaces (walls, dividers, etc.). Both of these advantages are worth the investment.

Continue on Page 3