Dog in back yard
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Canine parvovirus is a highly contagious virus. Young, old, unvaccinated, or immune-compromised dogs are particularly susceptible. Parvo, as it is typically called, or CPV, lives well in the environment, both indoors and outside. It is a non-enveloped virus, which means it lacks a membrane often called the envelope that is stronger than enveloped ones. It can survive indoors for months and outdoors it can live for months to years, especially in dark, moist environments.
Parvo can be easily spread by fomites, which are objects such as a doorknob or pet fur that can be contaminated by a virus. Dog-to-dog contact is not required for susceptible dogs to become infected. Dogs can become infected from contact with the remaining virus where an infected dog has been, or on objects an infected dog has used, or even from shoes and clothing carrying the virus. To make matters worse, non-enveloped viruses are not easily killed by most common household disinfectants and antibacterial soaps do not kill it. If you have had a dog with canine parvovirus in your home or yard, you need accurate information about what you can do to decrease or eliminate the risk of exposing other dogs while understanding that you cannot completely eliminate parvovirus from your home; it's simply not possible.
First, Remove Organic Material
Sanitizing is a two-step process that involves both cleaning and disinfecting. Some surfaces and substrates are easier than others to sanitize. For instance, carpet and grass are difficult to properly sanitize, whereas sealed cement is easier.
Before disinfecting, you need to clean since many disinfectants do not work well on organic material, such as stool or urine. Clean up any organic material from the yard and in the house. Bedding and toys that are not heavily soiled can be washed through a soap/bleach cycle and dried on a hot setting. It is best to discard anything heavily soiled. All areas and items still need to be properly disinfected, but the first step is to mechanically clean them.
Water can also be used to spray down outside areas to help remove any dried poop or vomit. Diluting an area such as a lawn by spraying with water may also help, but only if drainage and temperature allow the yard to thoroughly dry afterward.
Bathe any dogs using regular dog shampoo who were exposed or infected and recovered, as well as other dogs who had contact with the infected dog or area. This will help to decrease the risk of fomite transmission from their fur.
Use an Effective Virucidal Disinfectant
When choosing a disinfectant, make sure it has been proven to kill parvovirus. A label claiming to kill viruses does not mean it kills all viruses, such as the hearty, non-enveloped parvovirus. Additionally, any disinfectant must be mixed to the proper dilution and remain saturated for the proper contact time to be effective against parvovirus. Independent studies or FDA approval backing label claims are the most reliable means of determining a disinfectant's effectiveness.
Types of Disinfectants
Quaternary Ammonium Disinfectant
Despite its popularity for many years and label claims of efficacy against parvovirus, independent studies have shown this disinfectant to be unreliable against parvovirus. The label claims are based on diluting at 18 ounces per gallon, which is four times the typical concentration. Despite repeated reformulation and label claims, this is not seen as a reliable disinfectant against parvovirus and is not endorsed by independent studies or label-approved by the FDA. It must be rinsed off.
5% Sodium Hypochlorite (Bleach)
Bleach can kill parvovirus when it is used properly. It is readily available and relatively inexpensive but has some drawbacks. It can discolor or even ruin surfaces. The fumes can be irritating to the nose, eyes, and skin. Bleach is most effective on non-porous surfaces from which organic material has been thoroughly removed. For areas where you can safely use bleach, dilute household bleach (5% sodium hypochlorite) using 1 part bleach to 32 parts water (that's 1/2 cup per gallon of water). The diluted bleach must have ten minutes of contact time with the surface, which means saturating the area or continually spraying for ten minutes. It must be rinsed off.
Potassium Peroxymonosulfate Disinfectant
This disinfectant has some detergent properties, meaning it is effective for mechanically removing organic matter, such as vomit and feces. It can be irritating to the skin and eyes. The label claims efficacy against parvovirus at 1% dilution, even when mixed with hard water or organic material. It can be used in carpet cleaners to clean carpets and furniture (spot test for staining first) and can also be sprayed on yard surfaces. The area must remain saturated for ten minutes. It can be left to dry and does not need to be rinsed.
Accelerated Hydrogen Peroxide (AHP) Disinfectant
This disinfectant has become widely used in animal shelters, where CPV is not uncommon. Its detergent properties make it effective even when there is some organic matter. It can be used in one step for mechanical cleaning and to kill the virus. As in the other disinfectants discussed, proper dilutions and contact time are crucial to ensuring it kills the virus. It should be diluted using one part AHP to 32 parts water (1/2 cup per gallon of water) with a ten-minute contact time. This can be irritating to breathe but is less corrosive to surfaces and mucous membranes than bleach. It can be used in carpet cleaners and sprayed on grassy surfaces as well. It can be left to dry and does not need to be rinsed.
Careful and repeated removal of all visible feces is important. If possible, flush the yard with water and allow it to dry. Then apply a disinfectant that is effective with organic material, such as AHP or potassium peroxymonosulfate. These can be used with a pesticide sprayer or hose-end sprayer at the proper dilution to saturate the outside area. Diluted bleach may also be somewhat effective, but since it does not perform as well with organic matter it is less effective than the others. Bleach is also more dangerous to plant life and other surfaces. If your yard has dirt and grass, rather than just cement, there is no guarantee any disinfectant will be 100% effective. It is best to thoroughly clean, dry, disinfect with the proper contact time and dry at least twice. When possible, maximize exposure to sunlight and allow the area to dry completely.
In most home yard situations where there is grass and dirt, it is not possible to completely disinfect a yard. Out of an abundance of caution, you may want to avoid having unvaccinated dogs come to your yard for 6 to 12 months, even after cleaning and attempting to disinfect.
It helps to understand the difference between porous and non-porous surfaces. Water can go through porous materials. Non-porous materials include stainless steel, glass, metals, rigid plastics, and painted or varnished surfaces. Granite countertops are porous, but quartz is not. Porous materials include unpolished wood, laminate, granite, drywall, carpeting, ceiling tiles, and unsealed cement.
As mentioned, the first step is thoroughly cleaning the house and removing any feces or vomit that can be seen. Once all areas have been mechanically cleaned, you are ready to disinfect. Non-porous surfaces can be disinfected with diluted bleach or AHP or potassium peroxymonosulfate. Make sure you follow the manufacturer's instructions for the proper dilution and contact times for parvovirus.
For carpets and porous surfaces, AHP or potassium peroxymonosulfate disinfectants can be used in carpet cleaners to steam clean carpets and furniture. Understand that these areas are sometimes impossible to disinfect and heavily soiled items should be discarded if possible. Make sure you read the carpet cleaner instructions and spot-test any porous surfaces for possible discoloration. These surfaces will need to remain saturated for ten minutes to ensure the proper contact time. After disinfecting, the areas need to dry thoroughly.
Bedding, Porous Items, or Toys
Bedding and other fabric or porous items should either be thrown away, especially if heavily soiled, or washed thoroughly with detergent, hot water, and bleach and run through a hot dryer cycle if possible. If it is not possible to bleach the items, you could steam clean them with disinfectant as recommended for carpet and furniture. Consider if it is worth the risk to keep porous items such as bedding and toys that can't be bleached, or if it is better to throw them away.
Exposed Bowls and Non-Porous Items
Metal or ceramic bowls and non-porous toys should be washed thoroughly with a detergent, rinsed well, and then disinfected using an effective disinfectant. Throw away any plastic bowls that have any signs of wear, scratches, or teeth marks, which create porous areas. Proper dilution and contact time are important. This can be achieved by soaking the cleaned items in the diluted disinfectant for ten minutes, then allowing the items to dry. After disinfecting, thoroughly rinse the items with water and allow them to dry.
When is my Home Safe?
Unfortunately, there is no guaranteed time frame. There has not been any research that definitively states canine parvovirus can be eliminated from a home or yard environment in a specific number of days. There are many factors that affect whether cleaning and disinfecting efforts will be effective inside the house and outside in the yard. After a parvovirus-positive dog has been in your home or yard, it is safest to only have animals visit who have completed their vaccination series.