A Swine Health Information Center funded working group report on ultraviolet light, a type of electromagnetic energy invisible to humans, provides guidance on how it can be used on farms to exclude pathogens from being introduced into a herd, a process known as bio-exclusion.
When utilized and maintained properly, UVC light germicidal chambers can be an effective component of comprehensive biosecurity programs. However, proper construction and use of the chambers is necessary to obtain the full benefit UVC bio-exclusion.
Ensure UVC lights are working properly to provide the intensity of light exposure or dose necessary to inactivate the micro-organism. Place items for maximum exposure in the chamber and time in a way the light can impact all surfaces of the items. In addition, safety should be a top priority when utilizing UVC chambers.
The working group involved in this project examined UVC properties, related equipment, practices and pathogens resulting in best practices for use of ultraviolet light for bio-exclusion on the farm.
Chambers, which may be commercial or homemade, are usually constructed so items to be disinfected are passed through from the dirty side (entry/hallway) to the clean side (office/break room). UVC germicidal chambers are mostly used for small to medium items like lunch boxes, cell phones, small tools and medications. Food and semen bags can also be passed through the chamber without negative effects. Repeat exposure of plastics to UVC light may lead to a change in the color or smell of the object. Paper and cardboard cannot be disinfected in a UVC germicidal chamber. Larger UVC chambers, or UVC rooms, can be built for larger items.
The full report contains detailed information on the physics of UVC including wavelength details and how it inactivates pathogens. Information on dose calculations is incorporated along with specifics on measurement of UVC with a UV meter, factors affecting effectiveness, light system componenents and a discussion of different light bulbs. In addition, detailed maintenance and safety requirements are included for optimum results using UVC in germicidal chambers. The report concludes with a section on best practices in the field as well as extensive tables and resources on inactivation results. A fact sheet on UVC use has been developed as well.
To start using UVC disinfection on the farm, follow these steps:
Step 1. Set up UVC germicidal chamber and choose UV lamp
The UVC germicidal chamber is composed of four parts.
1. Chamber (fixture): contains the UV lamp and sleeve; must be lined with a reflective surface like stainless steel or aluminum to enhance the effect of UVC light.
2. UVC lamps: select to fit producer needs; low-pressure germicidal UVC commonly used. Bulbs should be labeled as germicidal (not fluorescent). Options may include power consumption (watts), bulb size (diameter), ozone level, base type, connection type and length of lamp.
3. Quartz sleeve for UVC lamp: optional to seal and protect the UVC lamp.
4. Controller unit (ballast): used to adjust voltage or current output to the UVC lamp.
Step 2. Estimate the necessary UVC dose for target pathogens
Published information on UV dose is available only for porcine reproductive and respiratory syndrome virus, porcine epidemic diarrhea virus and foot-and-mouth disease virus. For PRRSV and PEDV, studies showed the UVC dose required for a 3 log10 reduction was well below the range delivered by a commercially available chamber (150–190 mJ/cm2, BioShift Pass-Through UV-C Chamber, OnceTM). For FMDV, the UVC dose required for a 5 log10 reduction was also below the range delivered by a commercially available chamber (150–190 mJ/cm2, BioShift Pass-Through UV-C Chamber, OnceTM).
For other swine pathogens, UVC dose must be extrapolated from members of the same genus (bacteria) or family (virus). Most pathogens are inactivated at 190 mJ/cm2, but some require doses greater than 150 mJ/cm2. A significant gap in the literature exists for many swine pathogens.
Step 3. Use and naintain the UVC germicidal chamber properly
Follow these guidelines when using a UVC germicidal chamber on the farm. Remember, items to be disinfected must have direct exposure to UVC light.
• Remove organic matter (dirt) from items by wiping the surface prior to disinfection.
• Place items in single layer with space between them.
• Check for shadows and adjust item placement/spacing if necessary.
• Do not use secondary containers such as Tupperware or plastic baggies to contain items in the chamber; UVC light cannot penetrate these even if they are transparent.
• Rotate items in the chamber after the first cycle if needed to ensure that all sides are exposed to UVC light, or use a grid shelf.
• Cycle UV lamps prior to first use for disinfection on cold days to bring bulb energy up.
Maintenance of a UVC germicidal chamber involves cleaning and monitoring. Follow these guidelines to maintain your chamber.
• Clean the chamber interior with a non-abrasive cleaner when dirty.
• Check and clean the UV lamps every three months; make sure to wear gloves and use an alcohol-based disinfectant on a soft cloth or gauze.
• Monitor UVC lamp intensity with a light meter (radiometer); place face-up in chamber for five minutes and record, then place face-down and record a second time in the same spot.
• Change UVC lamps and ballast once per year or after 1000 cycles (minimum).
• Check intensity after installing new lamps.
In addition, develop a checklist for farm personnel to ensure they know how to operate the chamber. Run time and UVC intensity should be recorded. Item placement within the chamber can be monitored through the window or via cell phone video from within. Regular audits are recommended.
Step 4. Train staff on safety precautions
UVC light is mutagenic and carcinogenic; however, UVC germicidal chambers are safe when operated and maintained properly. Follow these recommendations to keep farm personnel safe.
• Install warning labels and properly train all personnel.
• Do not expose skin or eyes to UVC light; make sure the chamber is completely enclosed.
• Use a radiometer to ensure that UVC light cannot penetrate the chamber windows or seams.
• Connect a hard-wired safety shutoff to doors and latches.
• Discontinue use and contact manufacturer if there is any malfunction in the safety controls.
• Consider use of personal protective equipment including goggles or face shields designed for UV exposure, clothing and sunblock..
As the world deals with the COVID-19 pandemic, SHIC continues to focus efforts on prevention, preparedness and response to novel and emerging swine disease for the benefit of U.S. swine health. SHIC is funded by America's pork producers to fulfill its mission to protect and enhance the health of the U.S. swine herd.