How effective is personal protective equipment (PPE) on the farm? Is the discomfort of wearing PPE worth the reward? As influenza season rages in full force for humans and pigs, Montse Torremorell, DVM, professor in the College of Veterinary Medicine at the University of Minnesota, says it’s a question worth answering.
“Influenza can be transmitted indirectly through the contamination of fomites and the air,” she said during the American Association of Swine Veterinarians (AASV) annual meeting in San Francisco on March 4. “Secretions and excretions of pigs can contaminate fomites, and farm workers can act as fomites as their clothes, boots and personal objects may be contaminated with influenza.”
It may be stating the obvious, she says, but if farm workers don’t pay attention to it, the likelihood of transmission is very high. Not only can this result in workers getting sick, but it can also result in spread in pigs whether that’s from group to group or farm to farm.
She shared results from two studies conducted at the University of Minnesota looking at the use of PPE to help prevent the spread of influenza virus.
Do Face Masks Work?
Face masks are recommended for people working with pigs because masks help decrease aerosol exposure. Influenza is easily transmitted through the air, so researchers took a look at how well face masks prevent the spread of virus to workers.
“Type N-95 respirators are considered the standard for preventing exposure to viral aerosols since 95% of airborne particles are captured in the respirator,” she says. “However, a tight fit of the respirators to the face is necessary for particles to be removed and not bypass the seal. Unfortunately, N-95 respirators are difficult to keep in place when performing common farm chores and environmental conditions with elevated temperatures and humidity make wearing the N-95 respirators particularly uncomfortable for people.“
Other masks such as dust masks and surgical masks may also be used in farms. However, there is limited information available regarding their effectiveness for protecting workers from influenza at pig farms. The study collected samples from workers on influenza-positive farms wearing no masks, dust masks, surgical masks and N-95 respirator masks for four weeks. Workers alternated which mask type they were wearing.
After working with pigs, about 25% of the workers who did not wear face masks had nasal swabs that tested positive for influenza. For the other masks, the differences weren’t statistical, but the N-95 was the most protective at 5.77% positive detections; 8.65% positive detections with a dust mask and 10.78% positive detections with a surgical mask, Torremorell reports.
“I’m not sure how well workers wore their masks, but we think this represents how farmworkers would wear them in working conditions,” she adds. “A mask was protective and beneficial. Wearing one is better than not.”
Understanding which face mask is more comfortable to swine workers should increase compliance and the likelihood of wearing masks, Torremorell says. They asked the workers to score each mask on comfort. Of course, no mask was the highest rated from a comfort standpoint, followed by surgical masks, N-95 masks and dust masks were found to be the least comfortable.
Do I Need to Wash with Soap?
Detection of influenza virus on the hands of workers handling infected pigs should not come as a surprise, Torremorell says. In an experimental setting, 100% of hand wipes tested positive for influenza after researchers interacted with infected pigs for 15 minutes. Under farm conditions, a study reported 46 % of the instruments used when handling piglets and 58 % of farmworkers’ hands testing positive.
“Properly sanitizing hands is crucial to prevent disease transmission and exposure to workers,” she says. “But what’s the best way to get that done?”
Her team assessed the effectiveness of four hand sanitation protocols in decreasing or removing influenza virus from hands in an experimentally infected pig setting.
The treatments assessed included:
Soap and water: rinse 5 seconds, soap 10 seconds, rinse 10 seconds, wipe dry
Water only: rinse 10 seconds, wipe dry
Alcohol-based sanitizer (70% ethyl alcohol): sanitizer 10 seconds, air dry
Wearing disposable gloves: remove gloves
All participant’s hands became readily contaminated with influenza after handling infected pigs. Viable virus was found through virus isolation in 7 out of 84 samples after handling pigs.
“The alcohol-based hand sanitizer and wearing disposable gloves were the most effective treatments at reducing a larger amount of virus from hands,” she explains. “In fact, wearing disposable gloves prevented the hands of workers from becoming contaminated in the first place. Hand washing with water only and washing with soap and water reduced the amount of detectable virus, but did not eliminate it. Overall, results from this study emphasized the importance of using a hand sanitation protocol to prevent the transmission of influenza between pigs and farm workers.”
Torremorell adds that in addition to hands, clothing worn on farms to perform chores has a high likelihood of being contaminated with flu virus, too.
“Wearing farm dedicated clothing and showering in and out of swine facilities is also recommended to remove influenza-laden particles from the workers’ skin,” she says. “Face masks should be considered during periods of outbreak, especially when pigs are housed in enclosed buildings. This may need to be done if H5N1 infections are detected in swine where exposure through aerosols is likely to occur. Ultimately, it is the collection of measures applied comprehensively, including mechanical controls in farms and PPE usage, that will help decrease the risk of transmission to farm workers.”
The use of hand sanitizer between sites is also something to look at adopting if you don’t already, she adds.
“The risk of transmission between pigs and people is real,” Torremorell says. “A comprehensive flu control program must consider biosecurity measures that address indirect transmission routes. Now is the time to strengthen our biosecurity measures.”
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