Introduction

Diseases pose a constant threat to animal health. Surfaces contaminated by feces and body fluids contribute directly and indirectly to the transfer of microorganisms to other animals and locations. Contaminated housing areas, equipment, tools, vehicles, footwear, and other fomites all pose risks.

The cleaning and disinfection process – often referred to as C&D – inactivates or destroys these organisms. Reducing pathogen levels on surfaces reduces the potential for exposure and minimizes disease risk, protecting the health of animals and those working with them. The C&D process should be used routinely for all types of animal settings.

Properly performing C&D processes decreases pathogen levels on surfaces and reduces exposure risks. It also improves animal health and well-being, particularly in high-density settings.

• C&D is an essential component of biosecurity on farms and in other congregate animal settings (e.g., animal shelter facilities, exhibitions, and shows).
• C&D in veterinary clinics is a crucial measure for infection control and preventing disease spread.
• C&D is critical for disease containment and elimination during disease outbreaks and also serves as a layer of protection against novel or emerging diseases.

However, the C&D process is often not done correctly. When efforts are ineffective, the destruction of disease-causing organisms can be inadequate, resulting in exposure to disease agents and further spread of microorganisms.   Successful C&D involves understanding the key principles and steps for the process, choosing the best method, and recognizing any limitations. This document addresses this information as well as factors to consider when setting up a C&D program, common failures in disinfection programs, and how to address health and safety issues.

The Destruction of Microorganisms

Biocide

The general terms “biocide”, “germicide”, or “microbicide” refer to a substance or product that destroys or inhibits the growth or activity of living organisms. This includes disinfectants, sanitizers, antiseptics, and sterilants. But these antimicrobial products vary in their ability to destroy microorganisms!

Designations are often used to convey a specific action of the product against a particular group of microorganisms.

• The suffix –cide or –cidal (e.g., bactericide, virucidal, fungicide, sporicidal, tuberculocidal) reflects a killing action on a particular microorganism class.
• The suffix –static (e.g., bacteriostatic, virostatic, sporostatic) is used if the product only inhibits the growth or replication of the organism.

Depending on the goal for the C&D process, these designations can be critical!

Cleaning, Sanitizing, Disinfecting – What’s the Difference?

When discussing C&D, it is important to recognize that different processes can be used to destroy microorganisms. These terms are often used interchangeably, but their level of destruction varies.

Cleaning involves physically removing visible contamination from surfaces. Soaps and detergents bind to oils, soil, and organic material so it can be rinsed away. Some cleaners can disrupt the lipid components (e.g., cell membrane or viral envelope) of certain pathogens.

Sanitizing significantly reduces bacterial contamination on surfaces to levels considered safe from a public health standpoint. It does not eliminate all microorganisms. Sanitizers are most commonly used on food-contact surfaces.

Disinfection destroys or irreversibly inactivates most pathogens (e.g., bacteria, viruses, and fungi) on surfaces (i.e., inanimate objects).* It is generally not effective against bacterial spores. Efficacy will vary depending on the disinfectant product or method.

Sterilization destroys or eliminates all forms of microbial life, including bacterial spores. This involves the use of higher-level physical (e.g., extreme heat) or chemical (liquid or gas sterilants) processes and is generally used for medical devices/equipment.

*NOTE: Antiseptics are products applied to the surface of living organisms or tissues (e.g., skin) to destroy or inhibit the growth of microorganisms.

Some chemical products may act as sanitizers, disinfectants, or possibly sterilants, depending on the concentration or contact time used.

For example, the table below shows the required dilutions and contact times for a commonly used hydrogen peroxide disinfectant.

Table 1: Differences in dilution and contact time for an example hydrogen peroxide disinfectant.

Key Principles of C&D

Regardless of the setting or item, there are five key principles to keep in mind for a successful C&D program.

1. Clean surfaces before disinfection. Before any disinfection method is used, surfaces have to be cleaned. Cleaning removes dirt, organic matter (e.g., feces or manure, body fluids), and other debris that can hide organisms during disinfection. This material can also inactivate several disinfectants, making disinfection ineffective.
2. Use the right disinfection product or method for the situation. Disinfection methods can involve chemical or physical processes. Both disrupt the cell walls or membranes, viral envelopes, or replication processes of microorganisms, resulting in their destruction or inactivation. But no single product (or process) works for all situations. Products or methods needed for a disease situation will likely differ from those used daily. Higher concentrations or longer exposure times may be needed to destroy resistant organisms, but may increase health and safety risks or damage surfaces. 
3. Read the product label. In the U.S., products used to destroy microorganisms must be registered with the Environmental Protection Agency (EPA). The information on product labels must include the organisms the product can kill or inactivate, instructions for use (e.g., where the product can be used, the proper concentration, and the necessary contact times), and any health and safety issues. Always read and follow the label instructions for effective disinfection.
4. Give it time to work. Disinfection does not occur immediately. The process needs time to work, and times vary for each product or process. Surfaces must remain wet or exposed for the full contact time for the best results. Contact time is critical for success! 
5. Keep everyone safe. All disinfection methods have health and safety considerations for people, animals, or the environment. Read the product label for any safety measures required. Personal protection should be worn when mixing and applying disinfectants. Surfaces should be rinsed before reintroducing animals.