No spleen + dog bite = beware
A report from Seattlepi.com is a textbook example of what can happen to certain people after dog bites. Mike Moore tried to break up a fight involving his two dogs and received a minor bite. It barely broke the skin. No big deal, eh? Well, perhaps for most people, but unfortunately not for Mr. Moore.
He cleaned the wound and didn't think much about it. Two days later, he thought he had the flu. The next day, he was worse and went to the hospital. By the time he arrived, "his face and body had a bluish tint" ...never a good sign. When he was being examined, he was asked about the scar on his abdomen and he told the hospital staff it was from his spleen having been removed. They then asked about the bandage on his hand and he mentioned the dog bite. (Insert big ringing bells here!) The article says that the medical staff couldn't pinpoint the problem right away, but hopefully Capnocytophaga was a leading thought. Mr. Moore was critically ill by this point with multiple failing organs. He was admitted to ICU, became septic (overwhelming infection in his bloodstream) and was put on a ventilator. His hand had to be amputated, as did both legs below the knee and three fingers on the remaining hand. But he survived. (Despite the obvious long-term problems, he's very lucky to be alive after such a severe infection).
People that have had their spleens removed or who have non-functional spleens are at much greater risk for various infections, such as Capnocytophaga infections. No one should be allowed to leave a hospital after having their spleen removed without a letter saying, among other things, if you are bitten by a dog, get thee to a physician (pronto)! If you don't have a functioning spleen, make sure you know the risks and how to protect your health.
More information about Capnocytophaga and bites can be found on the Worms & Germs Resources page and in our archives.
News flash: You can't sue a dog
A lawsuit against various parties, including a dog, has been tossed out by a Michigan judge. Inez Starks sued the city of Warren, several police officers and Liberty, a police dog, after being bitten during some sort of confrontation in 2007. I don't have any details about the bite, but "unprovoked attack" and "police dog" don't tend to go together. Police dogs can and will bite in certain situations, but these are extremely well-trained and well-handled dogs. Most people that are bitten by a police dog probably have themselves to blame more than anyone else. Inadvertent bites could potentially result from being an innocent party in the middle of a confrontation, I guess, but there is no indication this person was merely an innocent bystander.
Anyway, the suit was tossed out by the judge. As a good example of sanity in the legal system, the judge fined Starks' lawyer for naming the dog in the suit.
Dog bites are a big deal and the cause of many lawsuits. Dog owners need to take their responsibilities seriously to reduce the risk of bites (and consequently being sued). At the same time, people need to take responsibility for themselves to reduce the likelihood of being bitten when confronted by a dog. Usually, that's focused on "be a tree" training in kids, but not upsetting police dogs is probably another good rule of thumb.
So you've been bitten by a dog....
Recently, a relative was bitten by a dog, and the incident emphasized that you need to take such things seriously and pay attention to making sure things get taken care of properly.
So what should you do if you've been bitten?
1) Identify the dog.
- You need to know who the dog is, and who owns it. If you can't identify the dog, you have to assume it's rabid (even though it's extremely unlikely) and get treated with a series of vaccinations.
2) Get medical care as needed.
- Bites can be associated with significant trauma and risk of infection. Getting to a doctor is particularly important if the bite is severe, occurs at a high risk body site (e.g. over the hands, joints, tendons and nerves, groin, prosthetic devices) or if you are at higher risk of infection (e.g. immunocompromised, don't have a functional spleen, very young or very old, pregnant). If in doubt, go to a doctor to be on the safe side.
Once you've done this, it's important to make sure that the offending dog actually doesn't have rabies. If you go to a doctor, they will (in most regions) report the bite directly to public health. Public health inspectors will investigate the rabies vaccination status of the animal and ensure that it is quarantined for 10 days. If the dog has rabies and is infectious, it will develop signs of infection within this 10 day period. If the dog is healthy after 10 days, it did not have rabies at the time of the bite.
Seems pretty simple, eh?
Unfortunately, there are a few places where this process can break down.
Reporting: All bites need to be reported. Bites that do not result in people going to the hospital may be missed. You don't need a serious bite to contract rabies (or another serious infection).
Public health follow-up: This is hopefully not an issue, but you should make sure that public health has investigated, and done so promptly. Don't be afraid to call to find out the status of the investigation, and make sure information has flowed quickly from the physician to a public health inspector. Hopefully they'll be in touch with you, but don't be afraid to initiate contact. The main issue with follow-up relates to the next point:
Prompt euthanasia of the dog: Sometimes, people will decide to euthanize a dog after a bite, because it's done it before, because they consider any bite unacceptable, and/or they fear for family members or legal liability. Dogs (or cats) that have bitten someone must not be euthanized before the 10 day quarantine period is over. If the dog is euthanized and the body is not available for testing, you have to consider the dog rabid and undergo post-exposure treatment. Veterinarians are required to ask whether a dog has bitten someone in the preceding 10 days prior to performing euthanasia, but it's possible that this could be missed, or people may not tell the truth because they want to have the dog put down ASAP. This is why public health inspectors need to investigate promptly - to provide another level of assurance that the animal is not euthanized inappropriately. You should follow up with public health to make sure things are underway and the dog is quarantined.
Rabies associated with dog bites is extremely rare in Canada (and many other countries) but still kills tens of thousands of people every year, mainly in Asia and the Middle East. Considering it's almost invariably fatal and pretty much 100% preventable, you need to pay attention to the risks, no matter how small.
Horse bites
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As a vet, I've been bitten by a wide range of animal species. When people talk about animal bites, they usually think about dogs and cats. Horses can (and do) bite as well. Most horse bites are probably playful nips that hurt a little yet don't cause major problems, but some bites can cause serious injuries and infections can result.
A recent paper in the Journal of Agromedicine (Langley and Morris 2009), with the rather unwieldy title of "That Horse Bit Me: Zoonotic Infections of Equines to Consider after Exposure Through the Bite or the Oral/Nasal Secretions". Bites apparently account for 3-4.5% of the approximately 100 000 annual emergency room visits in the US that are associated with horses. The authors of the paper review infections associated with bites and contact with organisms in the mouth and nose of horses.
A large number of bacteria have been associated with horse bite infections in people, including Actinobacillus, Streptococcus, Psuedomonas and Staphylococcus species. Some viruses can theoretically be transmitted by bites, but there's little evidence that this actually happens.
Although viruses are not of as much of a concern overall, rabies needs to be considered in every bite from a mammal. We pay a lot of attention to rabies with dogs, cats and wildlife, but it often gets ignored with horses. While I'm not aware of any reports of rabies transmission from horses to humans by a bite, it could happen. Fortunately, rabies is rare in horses so the likelihood of exposure from this species is very low. However signs of rabies aren't always obvious initially, and rabies in horses may mimic other diseases. Sometimes, rabies looks like colic, and human exposure through bites or other contact is possible when handling, evaluating and treating affected horses.
Unlike with dogs and cats, there are no clearly defined protocols for dealing with bites from horses. Any dog or cat that bites a person is supposed to be quarantined for 10 days. The reason for this is if the animal is rabid and the disease is advanced enough for the animal to be capable of spreading rabies virus, it would invariably develop signs of rabies and die within this time period. We don't have similar guidelines for horses. I suspect the 10 day observation period would be adequate but we don't have good data. The paper states that in Kentucky, a 14 day observation period has been used by the state Department of Public Health.
At the conclusion of the paper, the authors make a few important general recommendations for reducing the risk of disease transmission from bites and oral or nasal secretions of horses:
- Use good general hygiene, especially hand hygiene, after any contact with horses.
- Use gloves and gown or lab coat when examining horses in a veterinary clinic or hospital. (This might be overkill for all horses. We don't require gloves for every horse contact, just contact with mucous membranes (e.g. mouth, nose), wounds, incision sites and other high-risk areas. I think bare hands are fine for general contact as long as there is good attention to handwashing after.)
- Consider mask and goggles if the horse is coughing or sneezing.
- Develop standard operating procedures for handling sick horses.
- Use isolation when needed.
I'd add a few more points:
- Avoid bites. Pay attention to what you are doing around horses to reduce the risk of being bitten. Do not encourage playful behaviours (e.g. nipping) that could lead to bites.
- If you are bitten and it breaks the skin, clean the site thoroughly with soap and water. If there is significant trauma, or if the bite is over a joint, hand, foot, or a prosthetic device, you should see a doctor immediately because antibiotics are most likely indicated. If you have a weakened immune system, you should be evaluated by a doctor after any bite.
- Avoid contact with the horse's mouth or nose if you have skin lesions. Cuts and scrapes can allow bacteria to enter your body and cause infections. If you have a cut on your hand, make sure it is covered with a glove or waterproof dressing if you are going to have contact with the horse's mouth or something that came from its mouth (e.g. a bit).
This Worms & Germs blog entry was originally posted on equIDblog on 02-Sep-09.
Comparing dog and cat bites
Animal bites are very common. Millions of people are bitten every year, and the resulting burden in terms of pain, infection and financial costs is astounding. Dog bites get the most press because they often cause significant trauma. Dogs have larger and stronger mouths, and can bite repeatedly and more aggressively in some attacks. Deaths attributed directly to pet bites pretty much exclusively involve dogs.
Cat bites are smaller and have less chance of causing significant injury to tissues, but they may be more severe in the long run. There's a scientific paper called "Cat bite infections: biological warfare amongst cats," which is a testament to the nasty populations of bacteria that live in cats' mouths. It's not just the presence of bacteria that's a problem (afterall, dogs' mouths are full of potentially nasty bacteria as well) - the nature of cat teeth and the resulting bite wounds is a major factor. Cat bites often result in small but deep puncture wounds. This pushes bacteria deep into the tissues, where they're harder to get rid of and which results in a much greater chance of causing an infection. Furthermore, cats tend to bite areas that are high risk for development of bad infections, especially hands, which have a complex and susceptible network of tendons, tendon sheaths, joints and nerves. Bites that appear to be minor can end up causing serious problems, often much worse that an initially more dramatic dog bite.
Really, you don't want to be bitten by either a dog or a cat (or an iguana, hamster, person or anything else). A large percentage of bites are avoidable, and knowing how to interact with animals and read signals of aggression or fear are critical. If you are bitten, prompt and proper care of bites is required to prevent serious, long-term complications.
More information on bites, including management of bites, is available on the Worms & Germs Resources page. The CDC has a podcast that includes information about bite-avoidance that can be accessed by clicking here.
Dog bites and MRSA
There's been a lot of talk (hype) in the press about pet bites and MRSA (methicillin-resistant Staphylococcus aureus). This relates to a paper in Lancet Infectious Diseases regarding infections associated with pet bites. Some press articles are more sensational than others, but most are taking the bite infection paper and building in unrelated comments about MRSA in animals to make it seem like there's a major MRSA dog bite epidemic underway.
I realize that MRSA is a hot topic that is easy for reporters to latch onto, but the problem is that the actual research related to MRSA is being taken out of context (and blown out of proportion). MRSA was certainly mentioned in the paper, but it was not the focus of the research nor do the authors play up concerns about pets as a source of MRSA infections. Nevertheless, the impression people are getting from many news articles is that there is rampant MRSA transmission by infected pets.
Is MRSA infection a potential concern after a dog bite?
- Yes, but more because of the bite itself than the particular dog. MRSA infections that occur after a dog bite are probably the result of contamination of the wound with MRSA from the person's own nose or from another person, for example during a visit to their physician/clinic/hospital. It's possible for MRSA to be in the mouth of the dog and for it to be transferred to the wound during the bite, but that's pretty unlikely. The person bitten or someone treating the wound is a more likely source of the bacterium. So, the bite was the ultimate "cause" of the MRSA infection, because the infection probably wouldn't have developed without that break to the body's normal defensive barriers (i.e. the skin), however the "source" of the infection was (in most cases) NOT the animal. The same kind of infection could have happened with any similar type of trauma.
What should I do if I'm worried about MRSA and dog bites?
- Worry more about dog bites than MRSA. Bites themselves are major problems, even if MRSA is not involved. The degree of trauma can be significant, and a variety of bacteria can cause serious bite infections, not just MRSA.
- Take measures to reduce the risk of being bitten, both in terms of how you handle and train your dog and how you interact with other dogs.
- If you are bitten, immediately clean the wound as thoroughly as possible. If the bite is over a joint, tendon (e.g. wrist/ankle), prosthesis or genitals, if there is significant trauma or if you have a weakened immune system, you need to see a physician. If you have any other concerns, get examined by a physician promptly.
More information on MRSA in animals can be found on the Worms & Germs Resources page.
Rabid rat attack
Cab drivers have to put up with a lot of risks, but attacks from marauding rats probably aren't high on their list of concerns. However, a Ukrainian cab driver was recently attacked by a rat, and the rat was subsequently killed and found to be positive for rabies. The cab driver is now undergoing post-exposure treatment, and authorities are vaccinating pets and trying to eliminate mice and rats in the nearby neighbourhoods.
This is another good example of why it's important not to ignore a bite from any mammal, because rabies can affect any mammal. People often don't consider rodents a concern when it comes to rabies transmission, because most rodents would die from an attack by a rabid animal, thus preventing them from becoming infected and passing on the virus. This is probably true in most circumstances, but there have been enough reports of rabies in rodents, and potential human exposure from contact with rabid rodents, that we have to pay attention to this risk. Overall, the likelihood of acquiring rabies from a rat bite is pretty minuscule, and much less than the risk of contracting other diseases such as rat bite fever, but it's not zero. Since rabies is almost invariably fatal, even seemingly low risk situations need to be carefully assessed. In the case of this cab driver, there was definitely a risk of rabies exposure. If the rat had not been caught and tested, the potential for rabies exposure might have been dismissed, which could have had catastrophic consequences for the cabbie.
More information about rabies can be found on the Worms & Germs Resources page.
Rat bite fever
Rats can be really interesting pets. They can be quite social and are interesting to watch. Being larger than hamsters and gerbils, they can also be more easily and safely handled. They can still bite, however, particularly if they are not properly socialized and/or they are handled by people who don't know how to do it properly. Even though rats have tiny teeth, bites can still cause problems. One concern is rat bite fever. This disease is actually caused by two completely separate bacteria. Streptobacillus moniliformis is the most common cause in North America and Europe, while Spirillum minus is the main cause in Asia.
I'll focus on Streptobacillus moniliformis today. This bacterium is very commonly found in the mouths of healthy rats. Up to 100% of rats can be carriers. It doesn't cause disease in the rats, but it can be transmitted to people by bites or scratches. It can also be spread simply by handling rats (especially if a person has any cuts or broken skin), and through close contact with rats' mouth, such as kissing and sharing food (yes, some people do).
In most people, rat bite fever causes a high fever, headache, chills, vomiting, joint and muscle pain and a rash, most commonly over the soles of the feet, palms of the hands and the extremities. While the disease will resolve on its own in many cases, treatment with antibiotics is indicated because severe complications such as inflammation of the heart, pneumonia and meningitis can also develop.
Common sense can help reduce the risk of rat bite fever.
- Assume all rats are carrying S. moniliformis in their mouths.
- Only handle rats if you know how to do so properly, and if you know the rat is amenable to being handled. Avoid contact with the rat's mouth (e.g. kissing).
- If you have open sores or cuts on your hands, avoid handling rats or wear gloves.
- Always wash your hands thoroughly after handling a rat or cleaning its cage.
- Thoroughly clean any bites from any rodent immediately with lots of soap and water.
- If you develop signs consistent with rat bite fever after being bitten, consult your physician as soon as possible, and be sure to let your physician know about the bite.
More information about the care of bites can be found in our bites archives and on the Cat Bites information sheet on the Worms&Germs Resources page.
European bat lyssavirus in cats
Some areas of the world are fortunate enough to be rabies-free. However, there's a closely related virus that is of concern in many of these areas: European bat lyssavirus (EBLV). This virus is present in bats in various countries and can occasionally be transmitted to other animals. A recent report in the journal Emerging Infectious Diseases describes EBLV infection in two cats in France. Both cats died, although the actual cause of death of one of them was uncertain (the animal was also infected with feline immunodeficiency virus (FIV)).
Infection with EBLV in domestic animals is very rare. The risk to dogs and cats is probably very low, but obviously not zero. Avoiding contact with bats is always a good idea. Even in rabies-free areas, measures should be undertaken to keep bats out of houses, and people or animals should never touch sick or injured bats.
The risk to humans from infected domestic animals is unclear. It is thought that dogs and cats pose little risk for further transmission. While susceptible to infection, they are unlikely to transmit EBLV, probably because they produce very low levels of virus. Although there are no clear data about using standard rabies prophylaxis for the prevention of EBLV, it is believed that it would be effective if the virus was transmitted from an infected animal to a person. One cat in this report bit a veterinarian, who received a rabies vaccine booster since he/she had previously been vaccinated against rabies. Fifteen people who were exposed to the second cat underwent the recommended rabies post-exposure series of shots as a precaution.
Even in rabies-free areas, bites from bats or other wild animals should be taken seriously. They should immediately be cleaned thoroughly with lots of soap and water, and medical attention should be sought.
A big problem with EBLV is that it can be very difficult to diagnose. In this Emerging Infectious Disease report, several different tests were used and results were inconsistent. Multiple tests are probably needed to make a diagnosis. It's possible, therefore, that without this kind of comprehensive testing cases could be missed.
Overall, EBLV is a minor concern for public health, but is yet another reason to just use common sense - avoid contact with bats and treat bite wounds carefully, even in rabies-free areas.
More information about rabies can be found on the Worms & Germs Resources page, and in our rabies archives.
Group B Streptococcus: Don't blame the dog
I received the following question from a reader the other day: "I'm currently pregnant and was bitten by my grandmother's German Shepherd. The bite was on my ankle and broke the skin in several places. I went to the doctor and was prescribed antibiotics and the wound has seemed to heal fine. This is my second pregnancy and I have been diagnosed as group B strep positive, which I wasn't with my first child. I know that dogs can't spread strep throat to humans, but is it possible that I picked up group B strep from the bite?"
The short answer is that it's extremely unlikely there's an association.
Group B Streptococcus is predominantly a problem in people. Most people that carry this bacterium have no problems, although it can cause infections in some situations. It is of particular concern in pregnant women, because in 1-2% of exposed newborn babies the bacterium can cause serious infections such as bloodstream infections, meningitis and pneumonia. That is why pregnant women are often screened for Group B Streptococcus shortly before their due date, by taking a swab from the vagina and rectum. Approximately 10-30% of pregnant women carry Group B Streptococcus. Pregnant women that are carriers are usually given antibiotics shortly before delivery to reduce the risk of infection of the baby.
What about the role of pets? Group B Streptococcus is mainly found in people, and is quite common in healthy people. It is rare in pets, although it can cause various types of infections in animals too. Group B Streptococcus infections in dogs might actually represent human-to-dog transmission, although this hasn't been proven. In the case described above, a dog bite on a person's leg would not be a high risk for transmitting this bacterium to the intestinal tract or vagina. If a dog was carrying this bacterium in its mouth, it could cause a bite wound infection, but it is very unlikely that the bacterium would spread to other parts of the body in a healthy person. Other bacteria in the dog's mouth would be more likely to infect such a wound, even if Group B Streptococcus was present. If dogs were common carriers of this bacterium (which they are not), the main risk of transmission would be from regular contact, not bites.
So don't blame the dog... at least not for the Group B Streptococcus. The bite itself is another issue.
Immunocompromised people and pets: testing for Bartonella
I did a presentation at a conference last week with a physician on the topic of "Pets and Immunocompromised Owners". It led to some interesting discussion. People with suboptimal immune systems are becoming more common in households and they often own pets. These individuals are susceptible to infections caused by microorganisms that would not typically cause disease in healthy people, and they are also more susceptible to severe (including fatal) disease caused by microorganisms that would only otherwise cause mild disease. Therefore, there's a lot of concern about pets transmitting infection to immunocompromised people. Rarely is removal of pets from households of immunocompromised people necessary, but precautions should be taken to reduce the risks of disease transmission.
One topic that comes up periodically is testing for Bartonella henselae. This bacterium is the cause of cat scratch disease, which is spread by cats through scratches (obviously) but also through bites and by fleas. Cats that carry Bartonella henselae hardly ever have any signs of disease. In healthy people, cat scratch disease typically causes fever, local lymph node swelling, headache and fatigue. Immunocompromised people, particularly people with HIV/AIDS, are at higher risk for severe disease, which can be fatal if it is not identified and treated promptly. Similar disease can also be caused by other species of Bartonella that are not carried by cats.
Tests for Bartonella are not 100% accurate. Some tests just indicate exposure which does not tell you whether the cat is still carrying Bartonella or if it was previously exposed but already eliminated the bacterium from its body. False negative tests (e.g. the cat has been exposed but the test comes back negative anyway) can also occur. When considering screening tests, or any diagnostic tests in general, only do a test if there's a reasonable chance that the results will affect what you do.
- If a cat is positive, I wouldn't recommend removing it from the house. It may or may not be shedding Bartonella, so the key points for avoiding cat scratch disease are reducing the risk of bites and scratches, and controlling fleas.
- If a cat is negative, it's probably (but not guaranteed to be) free of Bartonella, but it could be infected later in life, and the key points for avoiding cat scratch disease are reducing the risk of bites and scratches, and controlling fleas.
So, if the recommendations are exactly the same in both cases, save your money and spare the cat the blood sample. I don't recommend testing for Bartonella henselae. The Infectious Disease Society of America also does not recommend testing (or treating) cats for Bartonella in their guidelines for HIV/AIDS patients.
Dealing with pet bites
A recent article in Canadian Living talked about how to treat pet bites. Three main tips were provided. My comments follow in bold.
1) If the bite has punctured the skin, wash the wound thoroughly with hot water, then cover with a sterile bandage. Excellent advice. Immediate cleaning of the wound is very important.
2) If the wound/scratch appears to be swelling, soak the area in a warm bath of Epsom salts: If the wound appears to be swelling (a sign of potential infection) get thee to a physician. Actually, you should "get thee to a physician" before it gets to that point. A physician should be consulted promptly following any bite over the hand, over a joint or tendon sheath (such as on the wrist or ankle), over any kind of implant or prosthesis, or in the groin area, or any bite to person who has a weakened immune system, who has had their spleen removed, or who has any serious underlying chronic disease. A large percentage of bites occur over these high risk sites, particularly the hands.
3) If the wound continues to look inflamed, visit your doctor right away.You're better off getting this addressed proactively, before the site is swollen and persistently inflamed. It's much easier to prevent bite infections than treat them.
Another tip I'd add is make sure the animal's rabies vaccination status is known and report the bite to the appropriate Public Health authorities. There's a big difference in terms of consequences and what needs to be done if it's your pet versus some random animal you know nothing about.
The best information in this article was a very important point. "What is Dr. Conway's best advice when dealing with aggressive pets? Avoid a bite altogether by taking proper precautions." That's the key. Knowing how to interact with animals is a critical aspect of bite avoidance.
More information about bites can be found in our Bite Archives and on the Worms & Germs Resources page.
Cat Scratch Disease - Bartonella henselae
Bartonella henselae is a small, Gram-negative bacterium that is host-adapted to cats. It may rarely cause mild illness in cats, but most felines, from tiny house cats to the king of the beasts, carry the bacteria with no clinical signs whatsoever. Unfortunately, when B. henselae infects a person it can cause any of several serious conditions (most of which have very long names!). These include bacillary angiomatosis (formation of masses of abnormal blood and lymph vessels), endocarditis (infection of the lining of the heart), chronic lymphadomegally (enlarged lymph nodes), and pyogranulomatous lymphadenitis, better known as cat scratch disease. There are at least four Bartonella species (among many, many other Bartonella species) that can infect cats, but B. henselae is the most common. There are at least nine Bartonella species that can infect humans, seven of which are zoonotic.
Between 5% and 40% of cats in the USA have B. henselae in their bloodstream. It is most common in cats from temperate areas, and is much less common in Canada. Bartonella spp. live in the red blood cells of their host – quite a clever strategy really, because it makes the bacteria readily available to be picked up by vectors like blood-sucking fleas, it protects the bacteria from the hosts immune system so it can live there for a long time, and it may even partially protect the bacteria from antibiotics. Cats can maintain a waxing and waning infection for months or even years. The bacterium is transmitted between animals by the cat flea (Ctenocephalides felis felis). Studies have shown that transmission does not occur between cats kept in a flea-free environment. Some ticks may also be able to transmit the disease. Diagnosis in cats is difficult – blood culture is the most reliable means, but it is not always sensitive. Antibody production only confirms exposure but not active infection. Polymerase chain reaction is often faster but no more sensitive than blood culture. An effective treatment regimen to eliminate B. henselae infection in cats has yet to be determined.
Transmission of B. henselae from cats to humans is thought to occur through contamination of scratches and bites (broken skin) with flea dirt (i.e. partially digested blood from the infected animal that is excreted by fleas = flea poop). Infection in individuals with weakened immune systems can be extremely serious or even fatal. In otherwise healthy people, the infection tends to remain localized, but can still cause massive swelling and abscessation of local lymph nodes. The type of disease that occurs may depend on the strain of Bartonella involved.
There are a few simple steps people can take to decrease the risk of cat scratch disease. These are particularly important for individuals with compromised immune systems, in which infection can be much more severe:
- Keep your pets flea- and tick-free. Effective treatment and prevention products are available from your veterinarian.
- Avoid or prevent situations that may result in bites and scratches from your pet. There is more information about this on the Worms & Germs Resources page and in our archives. If you do accidentally get scratched or bitten, be sure to clean the wound thoroughly. Consider seeking medical attention for bites in particular.
- Be aware of where cats come from. Stray or shelter cats less than one year old are most likely to be infected with B. henselae.
It is also important to note that there is NO evidence that declawing cats decreases the risk of transmission of B. henselae to humans!
As a point of interest, Bartonella quintana (a human-adapted Bartonella species) was the cause of trench fever in World War I, and was transmitted by lice.
Cat attacks Santa: another reason to vaccinate indoor cats
I admit I was a little slow picking up this Christmas story, but it's still "entertaining" (for lack of a better word). I've never thought about it, but I guess there are certain risks associated with playing Santa for pet photos. I'm not one to take my pets for pictures with Santa, but many worthy groups raise funds this way. During one recent event, "Santa" was bitten by a less-than-cooperative feline named Benny, who apparently didn't appreciate being in the company of the dogs which had also come. To make things worse, Benny wasn't your average cat - he was a pixie-bob, a very large breed of cat that resembles the North American bobcat (but it is in fact an entirely domestic breed)(pictured at right, from NBC10). After the incident, Benny's owners apparently produced proof of rabies vaccination, and everyone seemed fine. Besides the rabies concern, cat bites are not necessarily innocuous and severe complications can occur. That's one aspect of the story which hopefully didn't develop.
My point in writing this is to reiterate (again) my frequent statement that people need to make sure that their pets are properly vaccinated, even those that stay indoors all the time. Indoor cats can still bite people that visit, they can be exposed to rabid bats, and they can (not infrequently) escape. In this incident, if the cat had not had proof of rabies vaccination, a long quarantine period or even euthanasia may have been required - certainly not what anyone expects from a Santa photo-op.
And... maybe it's not a good idea to take large cats into strange places surrounded by dogs and thrust them into the arms of a strange person...something to consider.
More information on rabies and cat bites can be found on the Worms & Germs Resources page and in our bites archives.
Dog Bite Septicemia - Capnocytophaga canimorsus
Lots of people have heard of cat scratch fever (an infection caused by Bartonella henselae, which is often transmitted by cat scratches and bites), but dog bite septicemia is a much less familiar condition, although it is equally if not more serious when it occurs. As the name suggests, the infection (caused by the bacterium Capnocytophaga canimorsus) is typically transmitted by dog bites, and causes an infection of the bloodstream, resulting in very serious body-wide illness. The bacteria can also cause other types of infection including meningitis, endocarditis (infection of the heart valves) and rarely ocular infections.
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One study reported that 16% of dogs carried C. canimorsus as part of the normal bacteria in their mouths. Compared to the number of dog bites that occur, C. canimorsus infection is relatively uncommon. Most of the people affected by this bacteria have some kind of predisposing factor, particularly having had their spleen removed (splenectomy), having a weakened immune system, or being an alcoholic. The majority of cases occur in people who have regular close contact with dogs or who were bitten by a dog. Septicemia with C. canimorsus is fatal in approximately 1/3 of cases.
Prompt attention and treatment of dog bites is the best defence against bite-associated infections, including C. canimorsus. The bacteria are typically susceptible to many different antibiotics, but if treatment is delayed too long, the damage to the body may be too severe for the patient to survive.
ALL bite wounds should be taken seriously, and immediately washed thoroughly with lots of soap and water. Consult a physician for any bite on the hand, over a joint or tendon sheath (such as on the wrist or ankle), over any kind of implant or prosthesis, or in the groin area. It is also very important to consult a physician regarding treatment of any bite to a person with a compromised immune system, who has had their spleen removed, or who has any serious underlying chronic disease. Animal bites should also be reported to the local public health department.
More information on bites, much of which is also applicable to dog bites, is available on the Worms & Germs Resources page on the cat bites information sheet.
Picture: Trained attack dog Samo leaps forward toward a decoy's arm wrap as Tech. Sgt. David Adcox restrains him. (USAF Photo archives)
Blastomycosis and dog bites
I just received this comment from a reader of an earlier post about blastomycosis:
What should be done if a person was bit by a dog with blasto? I was trying to pill a dog who has blasto and the dog just out of reflex shut her mouth on my finger. What are the chances of the blasto being transmitted to me?
It's a reasonable question and one that I get periodically. If the bite didn't break the skin, the risk is essential nil. If the bite broke the skin, the risk is still fairly low, but certainly not zero.
Simple contact with an infected dog cannot result in transmission of blastomycosis because Blastomyces is a dimorphic fungus, meaning it can take the form of either a mold or a yeast. The highly infectious mold form is found in soil at ambient temperatures, while the minimally transmissible yeast form is present in the body of an infected animal or person. However, bites can be a different story. A bite from a dog with advanced pulmonary blastomycosis (e.g. fungal pneumonia due to Blastomyces) can result in localized blastomycosis at the site of the bite (e.g. only the person's finger might get infected).
Considering the dog in this case was already being treated for the infection (and therefore hopefully was not shedding much of the fungus), and that there are very few reports of bite-associated blastomycosis, the risk is probably quite low. However, any bite that breaks the skin can result in infection from the multitude of bacteria in an animal's mouth. Any bite on the hand should be taken seriously because it's easy for sensitive structures like joints and tendon sheaths to become infected. Consulting your physician or getting medical attention is recommended.
More details about general issues regarding animal bites are available in our bites archives. Relevant information is also available in the Cat Bites information sheet on the Worms & Germs Resources page.
Photo: Light micrograph of the budding yeast form of a fungus.
Characteristics of dog bites
A study was recently published in the Veterinary Record (O'Sullivan et al, 2008, volume 163) describing 234 dog bites in people in Ireland. Dog owners and victims of dog bites were interviewed to characterize the incidents. Bites were divided into 2 categories: bites to the dogs' owner(s) and bites to someone who didn't own the dog. Here are some parts of the study that I found interesting:
- A large number of dog breeds were involved. The breeds most commonly involved in bites were also the most common breeds in the country, indicating that higher bite numbers for certain breeds were a reflection of the breed popularity, not a breed-associated propensity to bite.
- A large percentage of individuals that were bitten were adults, but children were more often involved when the bite was caused by a dog that was not owned by the family. The reason for this is unclear, but may relate to inadequate supervision of the interaction of children and "strange"/unfamiliar animals, or inadequate education of children about how to interact with such animals.
- Slightly over half of the bites from dogs not owned by the victim occurred off the dog's property, which demonstrates that exercising proper restraint of dogs (e.g. preventing roaming, maintining good control of dogs when walking, keeping dogs leashed when necessary) could potentially have a major impact on the number of bites.
- 27% of non-owners and 10% of owners suffered multiple bites or sustained attack from the dog involved. This is a serious concern, because multiple bites or attacks are presumably more likely to result in serious injury, and children are more often bitten by dogs not owned by their family.
- 13% of non-owners and 7% of owners were admitted to an emergency department as a result of the bite(s). Non-owners were more likely to be hospitalized and require major medical treatment.
- Bites to the hands were reported more frequently in the owner group. Bites to the hands may occur due to improper interaction with dogs, inadvertent bites when playing, or behavioural problems like dominance aggression, which can result in bites when a person tries to take away food or a toy from the dog. Proper training of pets - and owners - is critical.
- 70% of owners and 81% of non-owners described the bite as unprovoked. However, in 45% of bites to non-owners, the person was on or very near the dog's property, so territorial behaviour may have played a role. Also, some people who reported the bite as unprovoked simply may not have recognized (a) signal(s) from the dog that it was aggitated and may bite. Again, better education of people is very important, in combination with appropriate restraint and training of the animal.
- 24% of owners and 22% of non-owners were bitten on a Wednesday. I have no idea why. Do dogs get cranky in the middle of the work-week like some people???
More information on dog bites can be found under "bites" in the Worms & Germs Archive.
Woman pecked by magpie loses leg
A recent report in the Medical Journal of Australia described the case of a woman who was pecked in the leg by her daughter's pet magpie. The woman was otherwise healthy (i.e. she did not have a compromised immune system), but the wound became infected by the fungus Saksenaea vasiformis, which rarely causes disease in people or animals. The infection became so severe that the woman's leg had to be amputated.
Saksenaea vasiformis can be found in soil all over the world. There are a few possible routes by which the fungus may have infected the woman's leg in this case. The fungus could have been on the person's skin, and been carried into the deeper tissues by the pecking. It also could have been on the bird's beak. Alternatively, it could have contaminated the wound after the pecking, through contact with soil or dirty hands.
This is an example of an infection that would be difficult to anticipate, since it occurred in a healthy person as a result of contact with a healthy bird, and with minor trauma, but potentially could have been avoided. Although the bird may not have been the source of the fungus, the break in the protective barrier of the skin was the critical event. Basic wound care is always important, and any injury from an animal should be taken seriously and properly addressed. Wounds should be carefully cleaned and monitored for signs of infection. A physician should be consulted as soon as possible if there are any concerns. A physician should always be consulted for any wound that is:
- on the hands
- over a joint
- over a tendon (e.g. wrist, ankle)
- in the genital area
- over a prosthetic device
- sustained by a person with a compromised immune system (e.g. HIV/AIDS, transplant or cancer patient)
More information on bites can be found in the Cat Bites information sheet on the Worms & Germs Resources page). It's unclear whether any of these precautions would have prevented the serious fungal infection that occured in this case, but these measures can reduce the risks of infection.
Banning Bowser from the beach
Many dog owners love to take their canine companions to the beach with them during the summer. Unfortunately, other people (particularly non-dog owners) sometimes take exception to having Bowser on the beach. These individuals often cite potential infectious disease risks as a reason to ban dogs from the beach.
While there are some potential infectious disease risks associated with having pet dogs at the beach, they are minimal. Also, some simple, common-sense steps can greatly reduce the risks that do exist. The infectious disease risks from feral (wild) dogs and wildlife defecating in the sand are much greater.
- The biggest health risk is actually probably from dog bites. Bites can be avoided through proper handling and training of dogs that are brought to public beaches.
- Many different bacteria (e.g. Salmonella, Campylobacter) can be passed in the stool of even healthy dogs. Some of these can be harmful to people, but only under certain circumstances, such as if they are swallowed or if they contaminate an open wound.
- Promptly picking up any stool passed by a dog greatly reduces the risk of significant contamination of the sand. Also, sunlight is an excellent “disinfectant” and will help kill any residual bacteria left behind.
- Dogs can also have different kinds of zoonotic parasites in their stool.
- Some of these parasites (e.g. roundworms, hookworms) are passed in a form that takes days to become infectious to people. So promptly removing dog stool from the beach minimizes the risk of transmission.
- Other parasites, such as Giardia, are immediately infectious when passed in the stool, but must be swallowed to cause infection. Prompt removal of dog stool, good hand hygiene with soap and water or an alcohol-based hand sanitizer before eating, and avoiding sand contamination of food and drink should largely eliminate this risk as well.
Overall, the risks of having dogs on beaches are very low if people behave responsibly, specifically properly restraining their dogs and promptly picking up stool.
More information about zoonotic diseases associated with contamination of sand and Sandboxes is available on the Worms & Germs Resources page.
Old pet, new baby...new problems?
Arrival of a baby results in dramatic lifestyle changes. As we try to emphasize at Worms & Germs, pets are a part of the household, and they can also be affected by the new arrival. While most pets handle the transition well, there can be some concerns. Foremost is aggressive behaviour towards the baby, which may occur due to inadvertent rough play, anxiety at household changes, territoriality or other causes. Even previously "perfect" pets can develop (and cause) problems as the social structure of the household changes. The potential problems can also change over time, as the baby starts to crawl, and starts to try to touch the pet or its toys or food bowls. Bites and scratches can occur, sometimes with tragic results. General recommendations for introducing a baby to your pet are available, including "And Baby Makes Four" and "Preparing Your Pet For Baby's Arrival" from the Calgary Humane Society. The Calgary Humane Society offers a program call New Baby, Old Pet, which is designed to help families make the introduction of babies to pets safe and happy. If you are expecting a new arrival in your family, you should consider contacting your veterinarian, local humane society or public health unit to see if a similar program is available in your area.
Dog bites cost millions
liability claims that were paid in 2007 were due to dog bites. This represented a cost of over $356 million! The average cost per claim was an astounding $24 511.This is just one more piece of evidence indicating the importance of dog bite prevention. The $356 million cost is just insurance claims. Not all bites are associated with insurance claims but can still be associated with financial costs, in addition to the obvious pain and emotional costs. There were ~14 500 insurance claims in 2007, but it is estimated that 4.7 million people are bitten by dogs in the US each year, with 800 000 people requiring medical care.
In the US, dog owners are liable for injuries caused by their pets in the following circumstances:
- if the owner knew the dog had a tendency to bite
- if a state statute makes the owner liable, whether or not the owner knew the dog had a tendency to bite
- if the injury was caused by carelessness on the part of the owner
It is important that everyone, pet owners and non-pet owners alike, know how to reduce the risk of being bitten by a dog. More information on bites can be found in the bites archives or in the dog information sheets in the Resources section.
Cat bites - Why it's not "just a scratch"
Even the most well-natured, lovable cat has the potential to bite. Particularly if an animal is frightened or in pain, it may lash out with teeth and claws, even at its most trusted human companion. Many of us are used to sustaining small cuts and wounds in everyday life, and at times it hardly seems worthwhile to trouble a physician to look at a little cat bite. But 20-50% of cat bites become infected, compared to 4-20% of dog bites. The bacteria responsible are most often combinations of Pasteurella spp., Staphylococcus spp., Streptococcus spp. and others. In some cases, particularly when Pasteurella multocida is involved, the infection can develop very rapidly (within hours) and may become very serious, or even spread to the bloodstream. Cat scratch disease (Bartonella henselae infection), despite the name, can also be transmitted by cat bites. Cat bites can be very deep, even though they look very small at the level of the skin, which may lead to infection of things like joints and tendons under the skin, which are more serious.You should see a doctor about any cat bite on a hand, over a joint, over a tendon sheath (such as the wrist or ankle), over a prosthesis or implant, in the genital area, or that causes a deep tear. You should also see a doctor for any bite if you happen to have a weakened immune system for any reason (e.g. HIV/AIDS, cancer or transplant patients).
The best way to prevent infection is to prevent the cat from biting you in the first place!
- Use common sense – know how to handle a cat properly so that it is not frightened or uncomfortable. If a cat growls at you or tries to get away, let it go!
- Don’t let cats play with your hands, feet or hair. Use a nice cat toy instead.
- Don’t approach strange cats, especially strays. If you are bitten by a cat that may not have been vaccinated for rabies, it is very important to report the incident to you local public health department and your doctor, as you may need to receive rabies post-exposure prophylaxis (PEP).
Dog bite prevention week
Some key points to teach children:
- Never approach a strange dog
- Be careful and quite when approaching a dog - never make sudden movements or loud noises
- Do not play with a dog without adult permission and supervision
- Never disturb a dog that is eating, sleeping or taking care of puppies
- Never take something out of the mouth of a dog
- Avoid direct eye contact with strange or aggressive dogs
- "Be a tree": If confronted by a strange or aggressive dog, remain still and quiet
- If knocked over by a dog, curl into a ball and remain still
- Tell any adult about any bite. Try to remember as many details as possible about a dog that bites so that the owner can be found and the rabies vaccination status of the dog verified
HIV/AIDS and dogs
My dog licked someone with HIV/AIDS, and they had an open sore. Can my dog get HIV?
Can a dog that bites someone with HIV get infected?
If a dog bites someone with HIV then bites someone else right after, can it spread the virus?
The answers are no, no and it's very, very unlikely.
HIV (human immunodeficiency virus) does not infect dogs. Regardless of how a dog is exposed, it will not develop an infection. HIV is also a very fragile virus. It does not survive long in the environment and a dog's mouth is not a very hospitable location. It is theoretically possible that if a dog bit someone with HIV and then immediately bit someone else, it could transfer the virus, but this has not ever been identified and is very unlikely. In some countries, the source of all cases of HIV are investigated, and an animal bite has never been implicated as a potential cause.
Bottom line....don't worry about HIV and your pets.
Not-so-likable licks
Sometimes when you fall and scrape your knee, or cut your hand, your favourite furry friend, in an act of unhindered devotion, will do to you what they would do to their own cuts and scrapes – they will try to lick it clean. The story that is often cited is the one about dogs and cats having enzymes in their saliva that help clean the wound. While it can’t be denied that there are various enzymes in the slobber, when you consider what else is in your little friend’s mouth, you’d be better to pass on their touching offer to help you clean up your cuts.First of all, think about where that mouth has been, and what’s been in it! Does your cat hunt mice and birds around your house? Does your dog have a habit of eating unidentifiable bits of garbage or poop when out on walks? Or maybe your dog, like so many, enjoys a snack from the cat’s litter box every once in a while. You probably want to keep things like garbage and poop out of your cuts, and if your pet’s mouth has been there, it shouldn’t be near your wounds either.
Even dogs and cats that don’t have any distasteful eating habits have millions of bacteria of many different kinds in their mouths. Most of the time the bacteria don’t cause a problem, and the “good” bacteria help to keep the “bad” bacteria in check. But if the “bad” bacteria are put somewhere the body’s defense systems have already been breached – like an area of broken skin – those same bacteria suddenly have a prime opportunity to move in and start multiplying in their new home. Some bacteria like Pasteurella multocida can cause very serious infections in situations like this. This species of bacteria is one of the primary culprits in bite wound infections, which are especially common with cat bites.
So why do animals lick their wounds in nature? Well, “dirty” is in fact a relative term. An animal can use its tongue to get the worst of the dirt and debris out of a wound, and the wound will be cleaner. But compared to how clean you can make a cut by even just washing it with a lot of water and some soap, and maybe a little disinfectant, a lick from a cat or a dog is counterproductive to say the least. So the next time you have a boo-boo that Fifi or Fido wants to kiss better, say thanks, but no thanks.
Information Sheets for Pet Owners
INFORMATION SHEETS specifically for KIDS, for VETERINARIANS, for PHYSICIANS and for PUBLIC HEALTH PERSONNEL 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.
| Animals | Diseases | Other |
| Dogs | Rabies | Litter Boxes |
| Cats | Giardia | Sandboxes |
| Turtles | Toxoplasma | Cat Bites |
| Hamsters | Leptospira | Raw Meat |
| Rabbits | Clostridium difficile | Petting Zoos |
| Pet Birds | Cryptosporidium | Needlestick Injuries |
| Reptiles | MRSA | |
| MRSP | ||
| Salmonella | ||
| Ringworm | ||
| Campylobacter | ||
| Bartonella henselae | ||
Please Remember:
- 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.
