Evaluation of Far Ultraviolet-C Light for Decontamination of Organisms in Whole Milk and Chicken Manure.

BACKGROUND

The dissemination of highly pathogenic avian influenza (HPAI) A(H5N1) in US poultry and dairy cows poses a public health threat. Farm workers caring for infected animals are at risk to acquire infections due to exposure to contaminated milk or poultry feces and secretions. Far ultraviolet-C (UV-C) light could provide continuous decontamination of surfaces and air in agricultural settings, but efficacy against organisms in whole milk or chicken manure is unclear.

METHODS

We examined the efficacy of far UV-C light against bacteriophage MS2 and methicillin-resistant Staphylococcus aureus (MRSA) in phosphate-buffered saline (PBS), 5% fetal calf serum, whole milk, or 5%, 10%, and 25% chicken manure, both in liquid suspension and dried on surfaces. We also compared the efficacy of 300 mJ/cm2 doses of far UV-C and 254-nm UV-C light against the test organisms in liquid droplets or droplets dried on surfaces.

RESULTS

For both test organisms, far UV-C achieved significantly smaller log10 reductions in whole milk and in chicken manure suspensions than in PBS or 5% fetal calf serum, both in liquid suspension and when dried on surfaces (P<0.0001). In whole milk, average reductions of both organisms with all doses were ≤1.2 log10 in liquid suspensions and ≤2.4 log10 when dried on surfaces. We found 254-nm UV-C was significantly more effective in reducing MRSA and MS2 dried on surfaces in whole milk or in 10% chicken manure (P≤0.02) but not in liquid droplets (P>0.05) except 5% chicken manure (P<0.001).

CONCLUSIONS

Our results suggest that in the absence of prior cleaning and disinfection far UV-C and 254-nm UV-C light technologies may have limited efficacy as an adjunctive method to reduce the risk for transmission of HPAI from surfaces in high-risk settings on farms.