Worms and Germs Blog : Animal Health & Diseases : University of Guelph : Ontario Veterinary College : Zoonotic Diseases : Guelph, Hamilton, Ontario

A Kitchener, Ontario family is dealing with a household outbreak of ringworm, likely contracted from a new pet guinea pig. Ringworm is a fungal infection cause by a few different types of fungi. Some ringworm fungi are able to infect both people and animals, and those can be spread in households from direct contact with an infected person or pet. In this case, the Gross family purchased a new guinea pig from a local pet store, and unfortunately, ended up bringing ringworm home as a bonus.

As is common, the new pet was the centre of attention when it got home, and the Gross' three children, ages 8, 5, and 2, had very close and frequent contact with it. The next day, the family noticed an area of hair loss on the guinea pig, at which point they took it back to the store. Ringworm was subsequently diagnosed, though there's no mention of how this was done, nor is there any mention of what actually happened to the little critter afterward.

The big problems started a week later, when a red lesion was seen on their youngest child's back. This was also diagnosed as ringworm, though again there's no mention of how, or whether it was definitively confirmed as ringworm. The newspaper report goes on to say "More spots kept appearing on Matthew’s skin as Gross was given different steroid creams to try and contain the infection." You always need to take media descriptions of medical issues with a grain of salt.  Hopefully, the child was treated with anti-fungal cream, not steroid cream, as the latter not only won't treat ringworm, they may make it worse if used alone. Steroid creams are often prescribed for non-specific skin issues (particularly if the skin is very itchy, which can certainly happen with ringworm), but in a case like this where there was known contact with an animal with ringworm, I have to hope that the physician was treating with an antifungal cream instead of, or in addition to, a steroid cream. 

Anyway, whether despite or because of the treatment, more skin lesions kept appearing on the child. Then skin lesions were found on the family dog, and both the dog and cat ended up being treated for ringworm.  The treatment for dogs and cats is relatively straightforward, but it's still a hassle and can be somewhat expensive, and often takes several weeks.

The family has contacted the pet store about paying for cleaning supplies, air purifiers and veterinary bills, but the company did not respond to the newspaper reporter's inquiries, citing an ongoing investigation. It's hard to say whether the company should be held responsible. It largely depends on the measures they take to reduce the risk that they are selling pets at increased risk of transmitting infectious diseases. There's always a chance of picking up something from a pet, so an infection does not necessarily indicate incompetence or liability. If a store had reasonable practices in place, it's probably the purchaser's responsibility to take proper precautions when they take the pet home, and it's an example of why prompt veterinary examination of new pets is always a good idea. It's rarely done, particularly for species that cost less than the price of a veterinary exam, and you never know whether it would have helped prevent anything in this case, but in many instances it can help identify potential issues and address them before problems occur.

Preventing outbreaks like this can be difficult. Ringworm can be found on animals in the absence of any skin disease, so you can't always tell an animal is infected by looking at it. (However, in this case if a large patch of hair loss was noticed by the owners the day after the guinea pig came home, it's likely that something was evident the day before). Ringworm is spread by direct contact, which is common between pets and kids, especially new pets that often get smothered with attention in the first few days. Good hygiene practices, particularly attention to handwashing, can certainly help, but some degree of risk will remain.

Overall, guinea pigs are relatively low risk for zoonotic diseases, but this report shows that even "low risk" pets can be sources of infection. Fortunately, while controlling ringworm outbreaks can take time and be frustrating, it's not a serious disease and it is controllable.

More information about ringworm can be found on the Worms & Germs Resources page.

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The more we look, the more we find when it comes to MRSA (methicillin-resistant Staphylococcus aureus). As people start looking for it in different animal species, it's often found. We've found it in many species already, including dogs, cats, rabbits, pigs, walruses, dolphins and alpacas, so it's not a big surprise to see a recent paper in the Journal of Clinical Microbiology (Ferreira et al 2011) about suspected MRSA transmission between a human and a hamster.

The case report describes a person with advanced cystic fibrosis who had undergone a lung transplant and had various other medical problems. Prior to another surgical procedure, MRSA was identified through routine pre-operative screening. Nasal and rectal swabs were then collected from the person's three pet hamsters, one of which was positive. The MRSA isolates from the human and hamster were the same, supporting transmission from one to the other. Given the person's underlying health problems, frequent contact with the healthcare system, the typical human origin of the strain that was found, and limited contact of hamsters with other animals or people, it is most likely that MRSA was transmitted from human to hamster in this case.

The paper concludes with: "Should testing of the pets of MRSA-positive patients be recommended? At this point, we recommend that MRSA-positive patients be informed that their companion animals can be potential sources of infection or reinfection. In the presence of a MRSA-positive human or animal, heightened hygiene practices should be instituted and unnecessary close contact should be avoided. Screening of household pets might be indicated in situations of recurrent MRSA infections despite adequate treatment or when immunocompromised patients live in the household."

That's consistent with our standard recommendations and hits most of the key points:

• Awareness is critical. People need to know what the risks might be and what they can do about them so that they can make informed decisions and realize why recommendations are being made.
• Testing of pets is rarely useful, particularly in the absence of a recurrent MRSA problem.
• Good hygiene practices are critical.

I don't really agree with the comment that testing of pets might be indicated when immunocompromised people are in the household (although the comment is properly hedged by saying "might be indicated"). A large percentage of the population has some degree of immunocompromise, and there's a huge spectrum from minimal risk to tremendous risk. Even in high-risk patients, screening is questionably useful to me because it doesn't really change what I'd do.

• If I screened a hamster from a high-risk person and found MRSA, I'd say that it probably came from the person, that it's possible it could be transmitted back to the person, that good hygiene practices should be followed and close contact should be restricted. There's no indication (or ability, in reality) to treat the hamster.
• If the hamster was negative, I'd say it was possibly negative because screening is not 100%, that the hamster could be exposed to MRSA from the owner at any time, and so to manage unknown colonization and reduce human-hamster transmission, I'd recommend good hygiene practices and restriction of close contact.
• If I'm going to do the same thing with a positive and negative result, I don't do a test.

This paper should be yet another reminder that we live in a complex relationship with our pets, including microbiologically. While we need to consider the role of pets in human infection (and the role of humans in pet infection), and we need to balance that with the positive aspects of pet ownership in order to maximize the benefits while minimizing the costs.

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A Montreal pediatrics resident has expressed concern about rat bite fever in kids. Dr. Karine Khatchadourian described three cases of this bacterial infection in a paper called "The rise of the rats: a growing paediatric issue," published last year in the journal Paediatrics and Child Health. The article didn't really present any evidence that this is a "growing" issue, but it is a disease of concern.

Rat bite fever is a bacterial infection most commonly (but not exclusively) associated with bites from rats. Healthy rats often carry the bacterium that causes the disease (Streptobacillis moniliformis in North America), and infection can occur when the bacterium is inoculated into the body by a bite, or when it's spread to mucous membranes like the mouth through direct mouth-mouth contact with pet rats (yes, some people kiss their rats).

The disease can be serious, and even fatal, if not properly diagnosed and treated. It's also a classic example of why physicians need to ask their patients about pet contact and why people need to take bites from pets seriously. Knowing that a rat is in the house, and particularly if a bite has occurred, is a key factor in helping make the diagnosis. If the physician doesn't ask the question, this critical piece of information may be missed, along with the diagnosis.

Being concerned about rat bite fever (and other zoonoses) is good, and ways to educate pet owners and physicians about such diseases are needed. However, extrapolating "rat bite fever is bad" to "rats are bad" is a stretch. The statement in the paper "Should we, as health care professionals, advocate to have rats banned from being sold in pets stores?" is over the top.

Every animal carries many microorganisms that can cause disease in people, given the right circumstances. Similarly, every person you meet is carrying something infectious. The key things to consider are:

• What is the likelihood of infection?
• How severe is the disease that may occur?
• What can be done to reduce the risk of infection?
• What is the cost-benefit, i.e. how do the potential risks compare to the potential benefits?

How can the risks be reduced?

• Rat owners need to be aware of the disease.
• Good handling practices are needed to reduce the risk of bites.
• Any bites that occur should be promptly cleaned and a physician contacted if there are concerns.
• Contact of rat saliva with broken skin or mucous membranes (e.g. kissing the rat) should be avoided.
• Physicians need to know whether their patients own pets, including rats, and know what diseases may be associated with those types of animals.

With this type of approach, the risk of infection can be reduced and the ability to properly and promptly diagnose the disease, in the odd case that it occurs, can be maximized.

I don't want to downplay rat bite fever. It certainly can cause illness, particularly in children under the age of 12.  A recent paper reported a fatal case in a 14-month-old boy, however in that case the infection was associated with ferrets, not a rat.

Parents of small children need to think about the risks of zoonotic diseases, as well as injuries (e.g. bites) when deciding whether to get a pet, and what type of pet to get. If people like rats, take care of them properly and communicate well with their physician (and if their physician is aware of the issues), then the risks of serious disease are quite low.

Dr. Khatchadourian suggests that parents "should stick to cats and dogs, and steer clear of rats." However, that's no assurance that a zoonotic infection will not occur. There's no evidence indicating the risk of disease is less with those species. It doesn't even eliminate the risk of rat bite fever, since Streptobacillus moniliformis can be found in the mouths of dogs too.

Rather than banning rats from pet stores, we should focus on educating pet owners, veterinarians and physicians about zoonotic diseases.

(click image for source)

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Cowpox virus is an example of a virus with a misleading name. It's place in history is from Jenner's observation that milkmaids who had been infected with cowpox were resistant to smallpox, leading to the use of cowpox (which causes very mild disease) to protect against smallpox (which is very, very bad). While cattle can be infected, they are not the true host of this virus, and infections in cattle are actually quite rare.

Various rodents are the true reservoir of cowpox. Other species can be infected from contact with infected rodents, including people and pets. Among pets, cats are most commonly infected, with most reports coming from central Europe. Cats may be infected more often because they may more often have close encounters with rats, but they are probably also inherently more susceptible to the disease than dogs.

Cowpox infections in dogs are very rare, but a case was recently described in Veterinary Dermatology (von Bomhard et al 2011). It involved a five-month-old Rottweiller from Germany that developed a very mild case of cowpox, with a single nodule on its muzzle. The dog recovered uneventfully, but it was an interesting case of a rare disease in a dog, and one that has some human health considerations.

People can be infected with cowpox from pets. In particular, infections from pet rats have been a problem in central Europe over the past few years. Outbreaks of human infections have been identified associated with widespread dissemination of infected rats from infected breeding or distribution facilities. Infections have also been reported from cats, and cats are a significant concern because of their ability to be a bridge between wild rodents and people, and because of the close contact they tend to have with people.

It's not surprising that disease was so mild in this Rottweiller puppy, and the risk to people in contact with the dog was probably limited because of the mild nature of the infection. No human cases were reported associated with this dog. Human infections from dogs have not been reported, largely because the disease is so rare in dogs and perhaps because when they are infected, dogs tend to have very mild disease. Cowpox is of minimal concern for most pet owners, but it something to be aware of when obtaining a new rodent, especially in regions where cowpox is an issue, and when dealing with cats in areas where cowpox is endemic in wild rodents. Some basic preventive measures include:

• Pet rodents and cats (especially newly obtained rodents) that develop skin lesions should be handled with care and be examined promptly by a veterinarian.
• Wild rodents should never be caught and kept as pets (for various other reasons, as well).
• Contact between domestic pets (particularly pet rodents and cats) and wild rodents should be prevented.

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Never a dull moment...

This morning the Toronto Star published an article about the intended euthanasia of 350 animals at a humane society in Newmarket due to an ongoing ringworm outbreak.  This was quickly followed by another article about the same event that gave a few more details, including some comments from the OSPCA chief executive officer Kate MacDonald, who confirmed that the euthanasias had begun.  A "very aggressive strain" of ringworm and "human error" (related to a breakdown in protocols) are currently being blamed for this morning's actions.  A lot of people are (understandably) very upset.  No one ever wants to see an infectious disease outbreak come to something like this.

I’m hesitant to comment too much at this stage, because we still don’t have all the facts - apparently even the duration of the outbreak is unknown.  No one has said if all 350 animals are infected (or what percentage of them are), nor how many other animals are present at the shelter. We also don’t know what’s already been tried in terms of controlling the outbreak.

A few facts about ringworm (dermatophytosis) that people need to remember:

• Ringworm is a skin infection that can be caused by several species of fungi.  It is not a "worm" at all.  It is also very easily transmitted by direct or indirect contact with infected animals - their fur, their cages, their blankets, or anything else that may be contaminated with infected skin cells or hair.  Such infectious material can even be spread over short distances (e.g. room to room) in dust that is stirred up into the air.
• Ringworm is transmissible to people, so with a large outbreak there are also issues with staff safety, and concerns with adopting out infected animals.  For most people ringworm infection may cause itchy, uncomfortable skin lesions, but for higher-risk people (e.g. very young children, the elderly or immunosuppressed individuals) the infection can be much more serious.
• There are also a lot of animals (particularly cats) that carry ringworm without showing any signs of infection. If the Newmarket shelter has 350 animals with clinical signs of ringworm (a detail about which we have no information right now), that’s pretty bad, but even the animals who don't appear to be infected may be carrying the fungus and could spread it to others.
• Crowding, close contact and warm, humid environments are all factors that increase the risk of ringworm transmission. These are also all factors that are very hard to control in a crowded animal shelter.
• Ringworm is treatable, but it is not cheap or easy. Animals typically require systemic therapy (usually oral medication, which can be very expensive particularly in large dogs) as well as whole-body topical therapy (e.g. dips, shampoos, sprays), and they need to be treated for several weeks. Decontamination of the environment at the same time is critical to prevent reinfection.

Cleaning up a ringworm outbreak at a shelter with at least 350 animals is no small undertaking.  The second article in the Star also describes personnel at the shelter this morning wearing "white hazardous material suits, latex gloves and plastic covers over their shoes", which would be considered reasonable precautions for entering a highly contaminated environment.

I'm sure we'll hear more about this in the days to come, and hopefully that will include more details about why the mass euthanasia was deemed necessary by the OSPCA.

For more more information about ringworm, download the information sheet from the Worms & Germs Resources page, or check out our archives.

Photo source: yorkregion.ontariospca.ca via www.thestar.com

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Urine from healthy animals is typically considered to be of little to no risk to people. This is generally true, at least for the otherwise healthy human population, but like with most things in infectious diseases, there are exceptions. An interesting one in rabbits is a bug called Encephalitozoon cuniculi. This microorganism (now classified as a fungus, but previously considered a protozoal parasite) is very common in healthy pet rabbits. In fact, the majority of rabbits have antibodies against E. cuniculi and may have it living in their bodies, particularly in the kidneys. It can cause infection of the brain, and is an important cause of neurological disease in rabbits, but more often than not it lives within the rabbit without causing any problems. Rabbits can shed spores of this organism is their urine, although they mainly do this only in the first few weeks after they've become infected, and shedding after that may be intermittent.

E. cuniculi is one of a group of microorganisms that became much more important when the HIV/AIDS epidemic hit. While rarely a cause of disease in people in the pre-HIV era, E. cuniculi is recognized as a potential cause of infection in people with compromised immune systems, particularly people with AIDS. Infections of people with normal immune systems are extremely rare.

It's always a challenge deciding what to do with a microorganism that can be shed by a large number of healthy animals. One reference "strongly advises" routine testing of rabbits, but that makes no sense to me. Here's why:

• Screening always comes down to a question of what you would do with the results. If you get a positive antibody test, it means that the rabbit has been exposed sometime in its life, but that does not mean that it is necessarily still infected or shedding spores - so it's not really convincing.
• Tests can be done to detect spore shedding but they are not particularly reliable. Since infected animals shed spores intermittently, a negative result here isn't convincing either.
• If the animal is positive, what would you do? If the household has no immunocompromised people, I'd say do what you've always done, and pay attention to good hygiene.
• If the animal was "negative," I'd say do what you've always done, and pay attention to good hygiene... same as for a positive rabbit.
• If there is an immunocompromised person in the house, I wouldn't say to get rid of the pet, since there's no evidence that's necessary. There is also no evidence that treatment is useful to eliminate E. cuniculi shedding rabbits. If the animal is positive, immunocompromised persons should avoid contact with urine and feces, and use good personal hygiene... just as they should do if the rabbit is negative!

More information about E. cuniculi in rabbits can be found in our archives.

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It seems like whenever a hit TV show or movie features an animal, there's concern about the "101 Dalmatians effect," whereby there's a mad rush to get the animal for a pet. When 101 Dalmatians was a hit movie, there was a huge spike in sales of this rather unusual breed - a breed which is certainly not for everyone. This results in unqualified breeders and puppy mills churning out marginal or poor quality pets and people getting a pet that really doesn't suit them. The end result can be a lot of disappointment, heartache and abandoned pets. This pattern has been repeated with various other breeds and animal species, and there is concern that the same will happen with guinea pigs as a result of the new Disney movie G-Force.

In terms of human health, guinea pigs are relatively benign. Bites and scratches are probably the biggest concern, and are often the result of improper handling. Bites can become infected from bacteria in the guinea pig's mouth or from bacteria on the person's skin. Allergies are also a potential problem. The number of diseases that are known to be transmitted by them is relatively small, and the risk of disease transmission is rather low.

Lymphocytic choriomeningitis virus (LCMV) is a concern with all rodents. It typically only causes disease in people with compromised immune systems, but can result in fatal infection. The risk of a guinea pig carrying this virus is likely greatest in animals from large rodent breeding facilties and when there is contact with wild rodents.

Ringworm is perhaps the most common infection that people get from guinea pigs (apart from infections following bites). Even healthy guinea pigs can carry the fungus that causes this disease.

Guinea pigs can carry Salmonella, but they are quite susceptible to infection and usually get quite sick. The risk of a healthy guinea pig shedding Salmonella, especially for a prolonged period, is pretty low. The risk is presumably greatest shortly after purchase.

Rabies is always a potential problem in mammals but the risk is very low with small rodents such as guinea pigs. (Very low isn't zero though, since hamsters have been sources of potential rabies exposure).

There are other potential problems too, but they are all quite rare.

The keys to reducing the risk of infection are:

• Purchase a guinea pig that looks healthy, is eating well, has no skin lesions or diarrhea, and is active and alert. Ideally, purchase an animal from a local breeder as opposed to a store that might have obtained the animal from a large breeder, via an animal warehouse, hundreds or thousands of miles away.
• Learn how to properly handle a guinea pig to reduce the risk of bites and scratches, as well as injury to the animal.
• Keep pet guinea pigs away from wild rodents.
• Use good general hygiene. Wash your hands after handling the guinea pig and after contact with bedding.
• Thoroughly wash any bites or scratches.
• Take particular care in the period shortly after purchase.
• Even though the cost of the guinea pig is less than the cost of a vet visit, a veterinary examination is important when the animal is sick. Apart from our ethical responsibility to take care of our pets, it's important to make sure that illness isn't caused by a disease that can be transmitted to people.

More information about the diseases mentioned above is available on the Worms & Germs Resources page. While we don't have a specific guinea pig info sheet yet, much of the information on the hamster information sheet also applies to guinea pigs.

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One more post about illogical and dangerous activities associated with animals and young children and I'll hopefully get off the subject for awhile. I came across this daycare's website today. Keep in mind (again) that the the Centers for Disease Control and Prevention (CDC) recommends that children less than 5 years of age not have contact with reptiles, and that the  Compendium of Measures to Prevent Disease Associated with Animals in Public Settings published by the National Association of State Public Health Veterinarians states that wild or exotic animals may not be appropriate in school settings. The photo gallery from this particular daycare included some great pictures of things that you should NOT do with young children. Some of the more striking example are below:

1) Letting a large snake wrap its body around the neck of a young child.

 2) Letting a young child kiss a snake.

3) Letting a child touch a turtle.

4) Letting a young child pet a pygmy hedgehog. (Like reptiles, hedgehogs very often carry infectious pathogens, including Salmonella.)

I wonder...

• whether anyone made sure these children immediately washed their hands after they touched the animals.
• how may kids but their hands in their mouths before they washed their hands. (Probably almost all of them, considering the "animal visit" probably went on for quite a while.)
• whether this activity took place in the same area where the children later ate lunch or a snack.
• whether the parents knew that this was going to happen.

I'm not against young children having contact with animals. I think pet contact can be very rewarding for young children. However, these individuals are at higher risk for infection and it is our responsibility to protect them. Putting them in high risk situations like these is inappropriate. Animal visitation in daycares is not necessarily a bad thing, if it involves animals that are a low risk species (e.g. dogs and cats), that are healthy, and that have been temperament tested (to show they are at low likelihood of biting).  It is also important that parents provide consent for their children to participate, that good hygiene practices are used (and enforced), and that the people bringing in the animals know what they are doing.

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Cowpox is a disease caused by cowpox virus. This virus is most famous for being used by Edward Jenner to vaccinate people against smallpox (which is caused by a related virus). However, despite the name, rodents are the natural host of cowpox virus, not cows. Most human cases of cowpox are associated with contact with rodents. Cats are another important source of human cowpox infection in some areas.

Cowpox infections in people are uncommon.  Most cases occur in Europe, western parts of the former Soviet Union and parts of Northern and Central Asia. Outbreaks of cowpox can be associated with infection of pet rats at central breeding or large housing facilities, which results in large numbers of infected rats that are then shipped to many different places. Recently, outbreaks of rodent-associated cowpox have been reported in Germany and France. It is suspected that these infections are associated with a large rat breeder in the Czech Republic, however this has not been confirmed.

Cowpox causes typical "pox" lesions, like those that are seen with chickenpox. Only a single lesion is present in most cases, but multiple lesions can develop. Flu-like symptoms such as fever and fatigue, as well as enlarged lymph nodes, are also common. Severe, even fatal, disease can occur in individuals with a weakened immune system, but in most people cowpox infection causes only mild illness and resolves without treatment.

Cowpox is not a concern in many areas of the world. In regions where it is present, basic, common-sense  precautions can reduce the risk of infection.

• Contact with infected animals should be avoided. Cats are an important source, and cowpox should be considered in any cat with appropriate skin lesions in an endemic area. The same should apply to rats with skin lesions.
• Gloves should be worn when handling cats and rats with skin disease, and hands should be washed immediately after glove removal.
• If skin lesions are identified on a rat, particularly over the feet, ears or tail, the animal should be examined promptly by a veterinarian.
• Don't buy any rat with skin lesions, and if possible, avoid buying rats that were bred and/or housed in facilities with a very large number of other rats.

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If your veterinarian suspects your pet may have ringworm, there are several different ways he or she may test for the causative fungus (a dermatophyte) on your animal's fur and skin.  Some of these techniques are more useful than others in different situations.

• Wood's lamp:  A Wood's lamp is simply a special ultraviolet light.  Approximately half of all Microsporum canis strains (the most common species of dermatophyte that causes ringworm in cats and dogs) will fluoresce blue-green under such a light. This type of testing is obviously very easy to perform.  However, other debris in an animal’s hair coat may fluoresce as well, and other species of fungus that cause ringworm do not fluoresce, so this test is not useful by itself in most cases.
• Microscopy: Sometimes ringworm fungus can be seen on hair shafts from an infected pet when examined under a microscope.  However, it is easy to confuse other debris and structures for dermatophytes.  Also, not every hair on an infected animal will carry the fungus, so it's possible to miss the infected hairs altogether with this test.
• Fungal culture: The best way to diagnose ringworm is to culture the fungus from the infected individual (person or animal). In animals, one of the best ways to collect a sample for culture is to comb over all the fur and skin with a new toothbrush, and then try to grow dermatophytes from the toothbrush. This allows the fur from all over the animal to tested, rather than just one little clump of fur plucked from one area.  It can also make it easier to get a sample from the face and paws of cats, which is where these animals often carry the fungus.  Although fungal culture is the best way to diagnose ringworm, remember that fungal culture takes much longer than bacterial culture – instead of days, it may take up to three weeks to grow some dermatophytes.

It's also important to remember that dogs, and more often cats, may carry dermatophytes on their fur even when they look healthy.  A positive fungal culture from an animal with skin disease, particularly a cat, does not necessarily rule out other diagnoses, so your veterinarian may still recommend other tests as well.  However, any animal with ringworm should be treated to prevent spreading the infection to other animals and people.

More information about ringworm is now available on the Worms&Germs Resources page, and in our archives.
 

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For more information on ringworm, see the Worms & Germs post Ringworm: Skin fungus by any other name.  The photos here show ringworm lesions on a person's arm and on a cat's face, respectively.  (Photo credits: A. Yu, Ontario Veterinary College)

Over the past several years, studies have shown that many environmental disinfectants sold and labeled for use against the fungi that cause ringworm (which are called dermatophytes) in animals and people are, in fact, not effective when used in households and veterinary clinics.  The problem is the chemicals are typically tested against a suspension of the organisms in a test tube, but in the “real world” the fungi are usually found on small fragments of infected hairs.  Its possible that the hair shaft protects the fungus from the actions of some disinfectants.

There are a few disinfectants that have been shown to be effective against dermatophytes even when they are found on infected hairs and skin cells in the environment.  The most readily available one is household bleach, used at concentrations of 1:10 to 1:100.  Other effective products include Virkon-S® (a detergent-peroxide based product) and Peroxigard® (an accelerated hydrogen peroxide product) . An environmental spray containing enilconazole (an antifungal agent that is also found in the topical medication Imaverol®) was also found to be very effective. This product is not approved for household use, but it is approved for use in catteries. It is also licensed as a topical treatment for dogs and horses in most of Europe and Canada.

Eliminating ringworm from the household or clinic environment can be difficult, because the fungus can be found anywhere that an infected animal (or person) sheds hair or skin cells.  Here are some guidelines for environmental disinfection of dermatophytes:

• All bedding, brushes, combs, rugs, cages, etc. should be vacuumed, scrubbed, and washed with hot water, detergent, and 1:100 chlorine laundry bleach, or another effective disinfectant (see above). It is best to throw out any items that cannot be thoroughly disinfected.
• Walls, floors, lamps, etc. should be scrubbed and cleaned in a similar manner.
• Carpeted areas may be impossible to effectively decontaminate. If possible, remove the carpet and either wash in hot water and bleach, or discard it. Otherwise, frequent vacuuming with immediate disposal of the collection bag is necessary.
• Vehicle interiors should be decontaminated as much as possible in a similar manner.
• Curtains can be “dry-cleaned” at a professional cleaner.
• Clean heating vents (from the house furnace) as well as possible. If the house is heated by hot air, change the furnace filter once weekly throughout the decontamination process.
• Cleaning and disinfection of the environment should be repeated at least once every 4-6 weeks (the more often, the better) until all affected animals and people have eliminated the fungal infection.

Obviously, environmental clean-up for ringworm is quite an undertaking.  If infection can be identified early, lesions can potentially be kept covered and movement of pets can be restricted to reduce the extent and amount of environmental contamination.

Special thanks to Dr. Anthony Yu (one of the veterinary dermatologists at the Ontario Veterinary College) for providing much of the information in this post, as well at the photos.

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You may notice a recurring theme in many of our posts and on virtually all of the information sheets on the Worms & Germs Resources page: an emphasis on handwashing. There is increasing emphasis on hand hygiene (i.e. hand washing and use of alcohol hand sanitizers) education in hospitals because the hands of healthcare workers are a major (if not the most important) means of disease transmission between patients. Despite hand hygiene being easy, cheap and effective, people rarely wash their hands as often as they should, and they often don't do it properly.

Most of the research about hand hygiene that has been published has focused on its use and impact in human hospitals, but this area is now also being studied more with regard to animals and veterinary medicine. A study published earlier this year in Veterinary Microbiology provided more evidence that hand hygiene is a critical infection control measure when dealing with animals. The study, coordinated by Dr. Maureen Anderson (of Worms&Germs fame) looked at MRSA carriage rate in veterinarians who work with horses. In addition to finding a high rate of MRSA carriage among these veterinarians (which was consistent with other reports indicating that equine vets are at higher than average risk for exposure to MRSA), the study looked at factors associated with MRSA carriage. Vets that reported routinely washing their hands between farms and those that reported washing their hands after contact with potentially infectious cases had a significantly lower rate of MRSA carriage. That should come as absolutely no surprise, but it's one more piece of evidence that we need to pay more attention to this routine infection control measure, in human hospitals, in veterinary environments and in households.

Remember, the 10 most important sources of infection are the fingers on your hands!

Click here for instructions on how to wash your hands properly.

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• Direct contact with animal blood should be avoided whenever possible.
  • In particular, avoid getting animal blood on any cuts, scrapes or other broken skin, and avoid getting the blood in your mouth, nose or eyes.
• If you do get animal blood on your skin, wash it off as soon as possible.
• While it is extremely unlikely for a person to get sick from touching animal blood, make sure you tell your physician about the incident if you do become ill.

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2011 ASM-ESCMID Conference on Methicillin-resistant staphylococci in animals

• Miconazole susceptibility of MRSA and MRSP
• Livestock associated MRSA in community hospitals in Ontario
• Equine hospital MRSA surveillance
• Biofilm production by S. pseudintermedius
• Methicillin-resistant staphylococcal pyoderma in dogs, and impact of treatment on colonization rates
• Surgical site infections in a small animal hospital

2011 University of Guelph Centre for Public Health and Zoonoses Symposium

• Pet ownership, interactions and animal-associated disease risks in Canadian households
• Metagenomic investigation of the oral microflora in healthy dogs

2011 Canadian Animal Health Laboratorians Conference

• Metagenomic investigation of the equine gastrointestinal microflora

2011 Canadian Association of Clinical Microbiology and Infectious Diseases

• MRSA contamination of the environment in 3 Ontario community hospitals

Coming soon

• 2011 American College of Veterinary Internal Medicine Forum, June
• 2011 ASM-ESCMID conference on methicillin-resistant staphylococci in animals, Sept

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