Don't Let the Fomites Get You Down
You may have had a hand in cross-infection in the past—without even knowing it
You may have had a hand in cross-infection in the past—without even knowing it
They exist in our eyelashes, on our skin, in our hair, and everywhere in between. In the grand scheme of the biological universe, we and the animals in our care are veritable breeding grounds for parasites—and we exist at their pleasure more than we’d like to admit.
Read all the articles from the July-August 2003 issue on cleaning and disinfecting your facility:
The Product Claim Game
Defining the Terms
The Bleach Niche
Great Points in the Fine Print
Being Chemically Balanced Is No Guarantee
Resistance Is Futile If You Clean Properly
It’s not a pretty picture. Unless, of course, you’re a mad scientist who finds critters at the molecular level life-affirming—the kind of person who examines these things for a living, as researchers in the human health care setting have been doing for years in their quest to learn more about the process of disease transmission.
In fact, the existence of germs on inanimate objects—or “fomites,” as those objects are called—has been the subject of much debate. Examining everything from pagers to stethoscopes to determine what lives on the surface of things, medical researchers have gleaned results that are not for the faint of heart. In one hospital study, two species of infectious bacteria lived on countertops for about a week, on bed rails for about 24 hours, and on phone handpieces and gloved and ungloved hands for an hour.
And that’s nothing compared to parvovirus, which has been known to live for a year or more on surfaces. But as Kelly Pyrek points out in the August 2002 issue of Infection Control Today (“Fomites’ Role in Disease Transmission is Still Up for Debate”), figuring out the role of these surface dwellers in disease transmission is a chicken-and-egg scenario. Are the microorganisms that are found on surfaces after human hands shed them no longer as viable as those that remain on the hands themselves, or do human hands pick up the fomites from those surfaces and go on to infect a live being?
One thing is certain, according to the Centers for Disease Control: there’s nothing quite like washing your hands to help prevent the spread of infection. In a fact sheet about its new “Hand Hygiene Guidelines” released last October, the CDC advised, “Improved adherence to hand hygiene (i.e. hand washing or use of alcohol-based hand rubs) has been shown to terminate outbreaks in health care facilities, to reduce transmission of antimicrobial resistant organisms ... and reduce overall infection rates.”
Disinfecting Those Dirty Digits
Alcohol-based hand rubs “significantly reduce the number of microorganisms on skin,” according to the CDC, which decided to recommend the use of such products because they are powerful, fast-acting, and convenient for health care workers on the go. In the animal care field, alcohol is not active against parvovirus, but a gel made of 70-percent alcohol inactivates some caliciviruses, says Kate Hurley, director of the Maddie’s Shelter Medicine Program at UC Davis. Ethanol has been found to be the most effective of the alcohols against calicivirus, she says.
But like hospitals, shelters often have trouble persuading staff and visitors to make use of hand-sanitizing dispensers designed to be used between the handling of each animal. Running across the room to a dispenser on the wall might indeed take a prohibitively long time when you’re moving cats into carriers or clean cages during the morning routine. But pocket versions may alleviate the problem; they are small enough to whip out whenever needed and save valuable time.
Just as with surface disinfectants, though, hand rubs can be inactivated by the presence of organic material; when hands are covered in dirt, saliva, or other debris, there’s no substitute for washing them with soap and water. “Just for people to be aware, [hand sanitizers] are certainly better than nothing,” says Hurley. “ But they shouldn’t give you a false sense of security, and mechanical washing of hands with soap and water is still preferable—or using gloves when you’re handling something like a known parvo or ringworm animal.”
Hand washing is considered “one of the mainstays” for controlling cross-infection in the hospital environment, write Brenda C. Love and Dwight C. Hirsh in “Disinfectant and Antiseptic Use in Small Animal Practice” (Kirk’s Current Veterinary Therapy, Volume XIII): “However, some studies have shown that hand washing itself may contribute to the spread of infections ... because mechanical scrubbing of the skin results in the shedding of squames, which carry with them the resident bacteria. Also, frequent hand washing can result in irritation, which can change the ecology of the skin, resulting in an increase of gram-negative bacteria.”
The authors therefore recommend a combination approach that involves using an antimicrobial soap when trying to control the spread of infection, followed by the use, between patients, of alcohol-based solutions— products that proponents say are generally less irritating to the skin than soap anyway.
Beyond disinfecting their “dirty digits,” healthcare workers should keep nails trimmed, wrote infection control consultant Nancy B. Bjerke in the July 2002 issue of Infection Control Today (“Disinfecting Those Digits Is Critical to Good Handwashing”). Artificial nails or nails more than a quarter-inch long can serve as a reservoir for germs, so the CDC recommends against them in the healthcare setting. “The most noted link of these adornments and their accompanying nail extension to a major Pseudomonas aeruginosa outbreak was published by the ... CDC in February 2000, where the causal links to 16 neonate deaths were a nurse with long natural nails and a nurse with long artificial nails,” wrote Bjerke.
Taking a Bite Out of the Fomite
Avoiding transmittal altogether is practically impossible in most shelters; for some, it’s simply not realistic to change disposable gloves or wash hands between the handling of every cat, says Hurley. During an outbreak or in the isolation room, such measures are critical, but in routine situations, there are other ways to at least reduce the levels of cross-contamination without losing too much time in the process.
For one thing, you can start by examining how you remove and replace cage and kennel items. In the picture Hurley paints of a normal routine, imagine you have the eagle eyes to see even the smallest particles: “You pick up a cat and put it in a carrier and then pull out its litter box and then dump that and pull out the dirty newspapers and dirty towels and bedding and whatever else. By the time you’ve done that with a few cats, you’re very coated with germs,” she says. “And with all the cats that you subsequently handle and pull out, you’re going to be transmitting the germs from all the previous cats, including all the stuff that sort of becomes airborne when you’re cleaning litter boxes—and you get coated with a fine dusting of coronavirus.”
While there’s no way to prevent partial contamination in these situations, it’s certainly possible to reduce the levels—and that’s something to aspire to, since some germs need to be present in a fairly sizable number to infect a new host. If two people are cleaning, one can pull out all the dirty materials from each cage and the other can insert clean materials into clean cages. If only one person is handling the job, she can remove all the dirty items first and then change smocks before replacing clean items. “It’s not ideal,” says Hurley. “There’s still some potential for disease transfer in taking the cats out and putting the cats in, but it’s going to be much less so when you haven’t also then coated your hands and arms and front with litter.”