As we encounter more infections caused by antibiotic-resistant bacteria (e.g. MRSA), we need to explore treatment options other than antibiotics. While we usually focus on "new" treatments, sometimes we can look back in time for ideas to treat infections. An old treatment method that is getting increasing attention these days is the use of honey. Honey may be a safe, effective and affordable treatment option in many cases. Click on the picture below to view a video by Dr. Karol Mathews, a critical care specialist at the Ontario Veterinary College.
An MRSA prevalence study was recently performed at the American College of Veterinary Surgeons (ACVS) conference in San Diego, CA. As per the study protocols, results are being made available through the Worms&Germs website. Click here to download the results file. This file contains code numbers for all positive results. If your number is not there, we did not isolate MRSA from your swab.
If MRSA was isolated from your swab, please do not panic! MRSA can normally be found in a small percentage of healthy individuals. Rates of MRSA carriage are higher in some groups, such as veterinarians. Most people that are carrying MRSA do not have any problems. In most situations, people in the general population that are carrying MRSA are not treated to eliminate colonization. However, if you are concerned about your result, we recommend that you contact your physician.
We appreciate your participation in this study. Analysis of the results is ongoing to look for factors associated with MRSA colonization. Further testing of MRSA isolates to characterize them is also ongoing. If there are any problems or questions, please contact Scott Weese at firstname.lastname@example.org.
As we see more and more infections caused by antibiotic-resistant bacteria, we have to re-think our approach towards antibiotic therapy. This often involves using new drugs, but sometimes it also involves considering the use of older drugs that we haven't used very much for a long time.
One such drug is chloramphenicol. Years ago, this antibiotic was widely used, and is still used in people and animals in some situations. In some respects, it is a very good antibiotic - it is often effect against many bacteria including those that are resistant to many other drugs, such as MRSA. Chlormaphenicol can also be given orally, and it's relatively cheap. Unfortunately this drug can also be very toxic, both to the animals being treated with it and to people that come in contact with with it in the process. In some animals, chloramphenicol can cause suppression of the bone marrow, where red and white blood cells are produced. This is more of a concern with long term use, but if the bone marrow does become suppressed, stopping treatment with the chloramphenicol typically resolves the problem. Unfortunately, this bone marrow suppression is much more of a concern in people - the supression is very severe, and can occur with exposure to even a very low dose (or probably single dose) of chloramphenicol. This results in a condition known as aplastic anemia, which it typically fatal. Fortunately this reaction is very rare in people, but there is no way to predict who might develop this condition, and since it is usually fatal, we obviously need to be cautious about using this drug. In some countries, chloramphenicol use in banned in all animals. In many others, it cannot be used in food animals, but can be used in pets.
- Chloramphenicol should only be used as a drug of last resort. There are situations where it is useful and may be life-saving, but the human health risks cannot be overlooked.
- If chloramphenicol is being considered, it is critical that people who would need to handle the drug understand the risk and how to safely handle the drug to avoid exposure.
- Chloramphenicol tablets should not be crushed or otherwise processed at home because of the potential for breathing in the drug when it is in powder form.
Direct contact with pills or liquids should be avoided by use of gloves or other safe handling practices.
- If a liquid form is used and is squirted onto food, the food bowl should be handled as if it is contaminated.
- If pills are being used, the animal should be observed to ensure that the pill is ingested and not spit up and left on the floor.
- Contact with the mouth and face and animals that are being treated with chloramphenicol should be avoided in case drug residues are present.
If people are unable or unwilling to follow safe handling recommendations, they should not use this drug.
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!
It's clear that methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a problem in dogs, both in terms of dog health and in terms of dogs as a potential sources of infection for people. It is thought that MRSA in pets is often (if not usually) acquired from people. Until recently, it has been unclear what makes individual dogs more likely to infected by MRSA compared to other bacteria. A study by Dr. Meredith Faires from the University of Guelph has provided some important new information in this regard. The study compared dogs with MRSA infections to dogs with infections caused by methicillin-susceptible strains of S. aureus (also called MSSA), from three large veterinary hospitals. Here are some key findings from Dr. Faires study:
- Animals that received fluoroquinolones were significantly more likely to develop an MRSA versus an MSSA infection. Fluoroquinolones are a specific class of antibiotics that includes drugs such as enrofloxacin, orbifloxacin and marbofloxacin.
- In both groups (MRSA and MSSA), most of the infections were skin and ear infections, with no significant difference in types of infection between the groups.
- There was no difference in the proportion of animals that survived their infections between the two groups: in both groups, over 90% of the animals survived. However, it is important to bear in mind that the majority of the infections were skin and ear infections, which are not usually life-threatening. Further study of more serious types of infection is needed to determine if MRSA is associated with a greater risk of death in dogs and cats.
This study provided more evidence that MRSA is an important problem in dogs and cats, and that the use of antibiotics is likely an important factor in the development of MRSA infections, compared to infections caused by MSSA. It also showed that the survival rate for common types of MRSA infections is high, if the infection is properly diagnosed and managed. Hopefully the information provided by this study can be used in future studies to help evaluate more risk factors, and to identify things that can be done to reduce the impact of MRSA in dogs and cats.
More information about MRSA in pets can be found on the new MRSA information sheets posted on the Worms & Germs Resources page.
Picture: Gram stain of Staphylococcus aureus
If you are looking for an interesting website to play around with, you should try HealthMap. This is a website created by the Harvard-MIT Division of Health Sciences and Technology that maps infectious disease reports from various sources. You can search by region and see what disease problems have been reported recently, or select specific diseases and find out where they've been reported. Some examples are shown below. The top image shows all disease reports worldwide (in the last 30 days), while the bottom image shows reports of Salmonella in North America during the same time period. The site relies on reports of diseases (many cases of various diseases occur but are never reported), so it focuses mainly on outbreaks or high profile cases , but it is still quite interesting.
Above: All reported disease outbreaks/cases worldwide in the last 30 days.
Below: Reported outbreaks/cases of Salmonella in North America in the last 30 days.
See the HealthMap site for more details.
Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant S. pseudintermedius (MRSP) are important causes of infection in pets, and are resistant to many different antibiotics. It's therefore very important that these bacteria are cultured and tested in a lab to determine what antibiotics may be effective. Even then, choosing an effective medication can be difficult due to the limited number of potentially effective drugs.
Treatment selection is further complicated by problems that can occur when methicillin-resistant staphylococci are tested against certain drugs in the lab - problems that are not readily apparent unless extra testing is done. One "problem" drug is the antibiotic clindamycin. Clindamycin can be an effective treatment for MRSA or MRSP infections, but some MRSA strains may be resistant to it despite appearing to be susceptible based on normal laboratory testing. This is because the bacteria can have "inducible resistance". Inducible resistance can be detected by a special test called a D-test (see picture), but this test is not widely performed in veterinary laboratories.
In recent study presented by Dr. Meredith Faires (University of Guelph) at a conference last week, 55% of MRSA from dogs and cats that were reported to be resistant to erythromycin and susceptible to clindamycin were actually inducibly resistant to clindamycin. But no MRSA that were susceptible to erythromycin were inducibly resistant to clindamycin. In contrast, inducible resistance to clindamycin was not identified in any MRSP. Therefore, in the absence of specific testing for inducible resistance (i.e. a D-test), it is wise to consider all erythromycin resistant MRSA to be clindamycin resistant as well, regardless of the results of traditional antibiotic susceptibilty testing.
Even though MRSA in pets probably originated from people, now that it is in the pet population, pets can spread it to other animals and back to people. It is unclear how frequently this occurs - most people are still more likely to encounter MRSA from another person than from an animal.
The emergence and spread of MRSA in humans was largely driven by extensive antibiotic use in people. Once MRSA crossed over to pets, antibiotic use in these animals almost certainly played a role in helping MRSA spread in the pet population. Antibiotic treatment has been identified as a risk factor for development of MRSA infection in dogs, and for MRSA carriage in horses.
Prudent antibiotic use is likely the most important factor in reducing the risk of MRSA in individual pets. Using antibiotics prudently means doing things like:
- Only using antibiotics when they're really necessary
- Using the most basic antibiotic possible (instead of the fanciest or most powerful antibiotic)
- Finishing every prescription completely and as directed)
Various bacteria can cause hot spots. Most commonly, Staphylococcus pseudintermedius is involved. Hot spots are quite low risk for transmission to other animals or to people, although it is possible for concerning bacteria like methicillin-resistant S. aureus (MRSA) to be involved. Only a culture of the infected site can determine the bacterium that is involved.
- Most hot spots are easily treated. This typically involves clipping the hair around the infected site and scrubbing the area with antibacterial soap. Sometimes, antibiotics and/or anti-inflammatories are also needed. The infected site should be kept as clean and dry as possible.
- While most hot spots are not caused by bacteria that are a major concern for transmission to people or their animals, any infected site should be handled with care. Direct contact with the hot spot should be avoided.
- If the infected site needs to be touched, gloves should be used if possible, and hands should always be thoroughly washed after touching the site.
- Care should be taken when touching hot spots because they can be very painful, and touching them could make some dogs bite.
- Prompt examination by your veterinarian will help ensure your pet gets the treatment it needs as soon as possible, and ultimately helps speed recovery.
- Always follow your veterinarian's recommendations closely and completely. Stopping treatment too early can lead to recurrence of the infection, which may be more difficult to treat.
In many cases (particularly in people but also in pets), a variety of focal skin lesions, including volcano lesions, may be diagnosed as a "spider bite" without any further testing. This is even done in areas where brown recluse spiders don't live! Another possible cause of a volcano lesion that may be mistaken for a spider bite is methicillin-resistant Staphylococcus aureus (MRSA). It is clear that many MRSA infections in people are being misdiagnosed as spider bites, but I have also talked to various pet owners whose dogs had MRSA infections that were originally diagnosed as spider bites. Most of these were from areas where brown recluse spiders would never be found. If an MRSA infection is diagnosed initially as a spider bite, the delay in starting proper treatment can lead to more prolonged and potentially more serious disease.
In addition to MRSA, the related bacterium methicillin-resistant S. pseudintermedius (MRSP), which is more common in dogs and cats than in humans, could be involved in similar skin infections. This is just as serious for the pet, but less of a concern for people in contact with the pet. For more information about MRSA versus MRSP, check out our blog on Methicillin-Resistant Staph: What's in a Name?
- MRSA, MRSP and other infectious agents should be considered as potential causes for focal skin lesions, particularly if they form deep open wounds or an abscess containing pus.
- Volcano lesions should not be assumed to be spider bites unless a bite from a brown recluse spider was observed. Such lesions should definitely not be diagnosed as spider bites in regions where the brown recluse spider does not live.
- Wash your hands if you touch any unusual skin lesion on a person or a pet.
- Do not encourage your vet to prescribe antibiotics when they are not necessary. Vets (and physicians) often feel pressure to prescribe 'something', even though they have no clear evidence of a bacterial infection. Antibiotics do not work for viral infections.
- Never give antibiotics to your pet without the direction of your vet.
- Always give the full antibiotic course, as prescribed. Do not stop early. Your pet may look better but the infection could still be there.
- Never save antibiotics for 'future use'. If your pet develops another infection, you need to have your pet evaluated by a vet to determine if antibiotics are needed, and what antibiotic would be best.
Methicillin-resistant S. aureus (MRSA): This species is the big concern. MRSA is an important cause of disease in people and an increasing problem in pets. It can cause serious infections and be transmitted between animals and people (in both directions).
Methicillin-resistant S. intermedius (MRSI): Actually, what most laboratories still call S. intermedius appears to be a related species called S. pseudintermedius. Regardless, MRSI (or MRSP) can cause a variety of infections in pets - usually skin and ear infections. While it can be spread from animals to people, this is likely rare and there is much less concern about MRSI compared to MRSA in terms of risk to humans from infected pets.
Methicillin-resistant S. schleiferi (MRSS): This species is closely related to (and often misidentified) as S. intermedius. It is most commonly found in skin and ear infections. There is no information about the risk of transmission to people from pets. It is probably possible but very unlikely.
Methicillin-resistant coagulase-negative staphylococci: This is a large group of staphylococcal species that are usually lumped together. They are commonly found in or on healthy dogs and cats as part of the body's normal bacterial population. They are less common causes of disease. There is currently minimal concern about transmission to humans.
MRSA is the main concern with regard to staph infections, and warrants particular attention when it causes infection in a pet. In these cases, important precautions to take include washing your hands frequently, avoiding contact with the infected part of the animal's body (plus the nose, where MRSA often hangs out), keeping the infected site(s) bandaged (if possible), keeping infected pets off the bed, and restricting contact with high risk people (e.g. young children, elderly, immunocompromised). For the other staph species, the risks to people are much lower, but it is still reasonable to implement these measures to further reduce the risks.
Here are some important points from the Canadian guidelines for management of community-associated MRSA in people.
- Testing of pets for MRSA carriage should only be considered when there is recurrent MRSA in the household and transmission is ongoing despite the implementation of household infection control measures.
- Testing of pets should only be done as part of an overall investigation of the household. Testing of pets but not human household contacts is not indicated.
- Removal of the pet should only be considered in exceptional circumstances, and removal should be temporary. Such circumstances could include households where controlling contact with the pet is not possible and/or when people in the household are being treated to eliminate MRSA carriage. The beneficial effects of pet contact should be considered in any discussion about removal of the pet from the household.
Many people in the horse world have heard the hype about methicillin-resistant Staphylococcus aureus (MRSA) in horses. MRSA can cause infection in horses, just like it can in people, dogs, cats and many other animals. It’s usually what we call an “opportunistic” pathogen, meaning it usually takes advantage of a person or an animal that is already sick or injured, like someone who’s in the hospital and has just had surgery. And because MRSA is resistant to many different antibiotics, the infection can be difficult to treat. The big concern with MRSA in recent years is that infections are now sometimes occurring in people who aren’t sick, and who don’t have wounds or incisions, which is where MRSA usually likes to move in. It’s very important to find out from the start if an infection is being caused by MRSA, so that it can be prevented from spreading to other people and animals, and so that it can (if necessary) be treated with the right kind of antibiotic.
Horses are a bit of a special case when it comes to animals and MRSA. When researchers look at the DNA of MRSA from a dog or a cat, it usually turns out to be one of the common human MRSA strains (usually called a “clone”) from the same area. This means that the dog or cat probably picked up the MRSA from a person somewhere. When researchers look at the DNA of MRSA from horses, however, they often find a different clone, which seems to be more common in horses and people who work with horses than in people in general. A very similar situation has also been discovered in pigs. The worry is that this “horse MRSA clone” can survive in and be transmitted between horses better than the human MRSA clones. That means that in order to control MRSA, just controlling it in the people won't do the trick - we need to take steps to stop the spread of MRSA in horses specifically as well.
Here are some key points to help reduce the risk of your horse (and you!) getting MRSA:
- Always wash your hands with soap and water (or use an alcohol-based hand sanitizer) after handling a horse, and before handling another horse.
- This is especially important if you have touched a horse’s nose, or any cuts or wounds that the horse may have.
- Don’t go down the row of stalls in the barn and pet every horse on the nose! They love the attention, but this is a great way to spread MRSA if it’s there!
- New horses coming into the barn, or animals coming back from a hospital, should be kept separate from all the other animals and only dealt with after all the other horses, for 3-4 weeks.
- This is an important measure for controlling many infectious diseases, not just MRSA.
- If your horse has a cut that looks infected, cover it with a bandage of some kind and contact your veterinarian. Your veterinarian can culture the wound to determine if it is an MRSA infection.
If your pet has MRSA:
- Talk to your veterinarian about how to handle the infection
- Avoid contact with the infected site. If you have to touch it, use gloves and wash your hands immediately afterwards.
- Wash your hands regularly after contact with your pet
- Avoid contact with your pet's face...MRSA often lives in the nose, in addition to the site of infection
- Try to limit overall contact with your pet until the infection has resolved. Close, prolonged contact such as letting the pet sit on your lap or sleep on your bed should be avoided
- Follow your veterinarian's instructions closely. Always complete the full course of treatment, even if your pet looks better
- Talk to your physician if you have concerns about your health, particularly if you or someone in the household has a compromised immune system
Current recommendations are that there is no indication to test people or pets for MRSA carriage when there is an infected pet (or person) in the household. Testing might be reasonable in some circumstances where uncontrolled transmission of MRSA appears to be occurring in a household, but there does not seem to be a reason to test with single incidents of MRSA infection.
Studies are currently underway looking at transmission of MRSA in households where pets have an MRSA infection. Better information will likely be available in the future as a result of these studies.
More information on MRSA in pets will be available soon in our Resources section. Another good source of information is the Bella Moss Foundation, a charitable foundation dedicated to MRSA in animals.
Recently, a story about a man who brought a horse into a hospital to visit his father was widely reported. The horse apparently made it to the man’s room, which included a trip in an elevator. The son, who appeared intoxicated, was eventually asked to leave (and take the horse with him). Said a hospital spokesperson “We do have a pet visitation policy, but it does not include a horse”. Strangely, the horse that was brought to the hospital apparently wasn’t even the father’s horse (which supports suspicions of the son’s lack of sobriety).
There are guidelines about which animals are appropriate for hospital visits, although it shouldn’t take an expert to figure out that a horse is not an appropriate candidate. Kicks, bites, and trauma from being crushed or run over are among the most obvious concerns. Horses can also carry a variety of bacteria that are potentially dangerous, especially to people in hospitals. These include Salmonella and methicillin-resistant Staphylococcus aureus (MRSA). There also aren’t that many house-trained horses out there.
So, while I can easily see how someone in a hospital would like to see his or her horse, there’s no way this should even be considered.
Some closing thoughts
- Would you like to ride in an elevator with a horse?
- Would you like to be stuck in an elevator with a horse?
- Do you think the horse was house trained?
- Do you think any of the healthcare personnel washed their hands after touching the horse?
This isn't the first time a horse has been in hospital, and some even get invited. The picture is from a story in Veterinary Practice News that described a program where horses were brought into hospitals!
While it is certainly true that any healthy animal (and person) can carry infectious diseases, and that prudence is reasonable, there is simply no evidence supporting this recommendation for the average household. Any contact with pets carries a very slight risk of disease transmission, just like any contact between people. There is currently no evidence, however, that sleeping with a pet in the bed increases the risk of disease. For your average pet and average household, this is probably exceedingly low risk and the recommendation is very difficult to justify. It is a reasonable recommendation when the pet is known to be carrying something that is transmissible to people (such as MRSA or Salmonella) or when a person has a compromised immune system. Banning pets from the bedroom completely doesn’t make any sense.
Personally, my dog is not allowed in my bed. However, that’s not because of disease concerns, it’s because she’s a large dog that snores and certainly can be a bed-hog. I have no problems with my cat on the bed. Life is never completely free of risk. If you enjoy having your pet in the bed, and you’re both healthy, I don’t see a reason to stop.
Unfortunately, this Letter may lead to unnecessary treatment of pets that carry MRSA or over-assumption of the role of pets in human infections. It also meant that I was stuck doing rounds and rounds of interviews with reporters wanting comments. The key take-home messages from this are:
- Pets are part of the household and should be considered if a household disease investigation is undertaken.
- While pets may sometimes be involved in transmission of MRSA, simply finding MRSA in a pet does not mean that it has infected anyone.
- There is currently no indication that we should be using antibiotics to get rid of MRSA colonization in pets because they almost invariably get rid of it on their own.
INFORMATION SHEETS specifically for KIDS, for VETERINARIANS and for PHYSICIANS are also available on the Worms & Germs RESOURCES page!
Click on the highlighted topics below for information sheets. Topics that are not highlighted are in development and coming soon. Sheets for other animal species and diseases are also under development and will be added when they are available.
- Your veterinarian and physician are your ultimate resource for information about the health of your pets or your family.
- Information provided here is accurate to the best of our knowledge, but infectious diseases can be unpredictable and these sheets are for general information purposes only.
- There can be great variation in disease risks in different geographic areas. The information provided was developed for Ontario, Canada, but most of the information is relevant for other regions as well.