Check out the new information sheets about Clostridium difficile now available on the Resources page!
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).
Tularemia Trouble
A case of pneumonic tularemia was recently reported in New York City.
Tularemia is a disease caused by the bacterium Francisella tularensis. It causes different signs of illness depending on how the bacteria enter the body. If the bacteria are inhaled, it tends to cause pneumonia (pneumonic tularemia). If the bacteria get in through a break in the skin, infection may cause the local lymph nodes (glands) to become very swollen, and in some cases the skin itself may become infected resulting in the formation of large sores (ulcers). Infection can also cause sores in the mouth and diarrhea. The earliest, most common signs are things like fever, headache, chills, sore muscles, and sore throat which often come on very abruptly. The infection can be treated with antibiotics, but it is important to see a doctor and start treatment as soon as possible.
Tularemia is also sometimes called "rabbit fever," because the bacteria are often carried by animals such as rabbits and hares. Rodents (including beavers, rats, mice, squirrels etc.) can also carry F. tularensis, and occasionally so can cats and dogs. Some biting insects like deerflies and certain species of ticks can carry the bacteria and transmit it when they bite. Francisella tularensis can also survive in water and soil for a long time. People can become infected by being bitten by an infected insect, handling an infected animal (dead or alive), or coming into contact with feces from an infected animal. Occasionally a person may inhale the bacteria if it is in the air, as may happen with disturbed, dusty, contaminated soil.
More information on tularemia can be found on the CDC's tularemia website.
Things you can do to avoid tularemia:
Avoid touching or handling wildlife (dead or alive), especially rabbits and rodents.
Don't let your pet touch or eat dead animals.
Always wash your hands if you have been working outside in the dirt/soil.
Wear insect repellent containing DEET (visit the Health Canada website for more safety tips)
Make sure you only wash food with and drink water that has been properly treated.
One of the reasons tularemia is such a big deal is it is very infectious - as few a ten bacteria can be enough to make even a healthy person sick! But it is still quite uncommon in North America - about 100-200 cases are reported in people in the USA every year. Between 2002-2004 there were 34 cases reported in Canada, most of which occurred in Quebec and in adults. However, infection can be fatal in a very small number of cases, especially if proper treatment is not given as soon as possible.
West Nile virus in dogs and cats
One thing that has become very clear around my house the past few days is that mosquito season has arrived. Along with the annoyance, buzzing and itching, mosquitoes are of concern because they can transmit various viruses, including West Nile virus. While West Nile season tends to be later in the summer and fall in most regions, West Nile virus awareness and mosquito bite avoidance should be considered whenever mosquitoes are around. 
Most of the attention about West Nile virus has been paid to humans, horses and birds, because of widespread illness and death in those species. Dogs and cats can certainly be exposed to West Nile virus if they are bitten by an infected mosquito; just like people and other animals. However, there are very few reports of West Nile virus infection in dogs, and even fewer in cats. Most dogs and cats that are infected do not develop signs of disease and simply develop antibodies against the virus.
Even if dogs or cats develop West Nile virus infection, there is no risk of transmission to other animals or human. This is because there is never a large enough amount of virus in the blood of these animals for a mosquito to pick it up and transmit it to another animal or person. The virus also can't be transmitted by direct contact with an infected dog or cat. West Nile virus is not found in saliva, so it is also unlikely to be transmitted by an animal (instead of an insect) bite.
There is no reason to be concerned about transmission of West Nile virus from your pets. If you live an area where West Nile virus is present, you should take precautions to avoid mosquito bites, such as avoiding mosquito-dense areas, wearing insect repellent with DEET, wearing long pants, long sleeves and socks when outside, avoiding peak mosquito hours (dusk and dawn) and eliminating any areas of standing water where mosquitoes can breed.
Pets and strep throat
Another question that I periodically get asked is about pets (mainly dogs) and strep throat. The usual situation is a household where there has been strep throat in multiple family members or where someone, usually a child, has had repeated bouts of strep throat. People ask whether their pet could be the source.
Strep throat is caused by Group A Streptococcus, a bacterium that can be found in the throat and on the skin of some healthy people. Strep throat and impetigo are the most common diseases caused by Group A Streptococcus, although severe (‘invasive’) infections can occur, including ‘flesh-eating disease’. Group A Streptococcus is typically spread between people, both from people that are sick and healthy carriers.
Group A Streptococcus carriage by dogs and cats is extremely rare, and it is unlikely that they are involved in transmission to people. There were some older studies implicating dogs in transmission of Group A Strep, however there were weaknesses in the methods used by those studies which probably lead them to misidentify other types of Streptococcus that are often found in dogs as Group A Streptococcus. There is currently no convincing evidence that pets are a source of strep throat infection, although the possibility cannot be completed dismissed.
I have had questions about treatment of pets when recurrent strep throat infections were present in a household, which is not supported by any evidence and could lead to problems like antibiotic resistance and side-effects from antibiotic use such as diarrhea. It’s hard to say whether there is any indication to test dogs or cats when recurrent strep throat is present in a household. Collection of a throat swab by a veterinarian and culture of the swab is fairly easy to do. It’s not unreasonable to consider that but a few things must be remembered:
- Even if Group A Streptococcus is found in a pet, it does not mean that the pet is spreading it. The pet might just be an ‘innocent bystander’ that was infected by a family member. It makes no sense to test the pet if the rest of the household is not being tested.
- Proper identification must be performed by the laboratory to differentiate Group A Strep from other strep. Just finding ‘Streptococcus’ is not useful.
- There are no guidelines for what to do in the unlikely event that a pet is identified as a carrier.
Overall, pets are not likely a major (or even minor) source of strep throat. If strep throat is circulating within a household, it's most likely being spread between people.
Parvovirus and Fifth Disease
Numerous outbreaks of Fifth Disease have been reported internationally. That, itself, is not particularly newsworthy because outbreaks are quite common and disease is typically mild. In children, Fifth Disease typically causes a rash on the face, trunk and limbs. The sa
me type of rash can occur in adults, as can joint point or swelling. Severe complications can develop in pregnant women. There is no vaccine. Fifth Disease is caused by Parvovirus B19, a fact that sometimes leads to questions about dogs because of peoples' awareness about canine parvovirus.
Canine parvovirus is a highly infectious cause of life-threatening diarrhea in dogs, mainly puppies. Canine parvovirus vaccination is a very important component of routine vaccines for dogs.
Questions often arise about whether dogs can be a source of Fifth Disease, or whether people with this disease can infect dogs. The parvovirus that causes Fifth Disease is not the same virus that causes disease in dogs. Human parvovirus cannot infect dogs, nor vice versa.
An interesting fact about Fifth Disease is the origin of its name. The name originates from a standard list of causes of rash from the early 1900s. This condition was the fifth on the list, and for some reason, it became known as ‘Fifth Disease’. None of the other disease were named by their ranking.
Public Domain image from Wikimedia.org
Camping with canines - tick tick not!
The warm weather is just about here, and that means the start of camping season. Lots of people love to spend time in the great outdoors during the summer, whether it’s at a summer cottage on the lake, trailer camping in a park with electricity and running water, or roughing it in a tent in the peace and solitude of a more remote wooded location. And many people bring along their faithful companions – their dogs – who enjoy the experience just as much, if not more, than we do.
But there are also dangers lurking in the forests – microscopic dangers carried by tiny insects and other bugs. Ticks in particular are problematic. Certain ticks can carry a number of diseases that can make dogs sick, including Lyme disease (caused by Borrelia burgdorferi) and Rocky Mountain Spotted Fever (RMSF)(caused by Rickettsia rickettsii ). Both Lyme disease and RMSF are more common in certain areas where the tick species that carry them are present. You can NOT catch these diseases from your dog, but both you and your dog can be infected by the ticks that carry them. People can also be exposed to these pathogens by accidentally crushing an infected tick while trying to remove it from their dog. Ticks must be removed very carefully to ensure that the entire tick is removed, including the head and mouth pieces, without crushing it. If you're not sure how, contact your veterinarian. Also, the sooner the tick is removed, the less likely it is to transmit certain diseases, so be sure to check your dog thoroughly for ticks when you come back from a walk in the bush.
The Minnesota Department of Health recently reported that the number of cases of (human) Lyme disease increased in that state in 2007. This could be because of spreading tick populations, more people participating in activities in tick-inhabited areas, or increasing awareness and diagnosis of the disease by physicians.
If you and your canine companion will be spending time in some of the wilder and woodier parts of the great outdoors, talk to your veterinarian about what you can do to protect your dog. There are vaccines available for Lyme disease and the bacterial infection leptospirosis (which is also transmissible to people). Flea and tick preventatives are also very important, and many of today’s products are very effective. People should always wear insect repellent when camping or hiking in the woods. Visit the Health Canada website for safety tips on using personal insect repellents. All dogs should be vaccinated for rabies, whether they go camping in the backwoods or they’re house-bound city-slickers.
HIV/AIDS and dogs
Here are a couple questions that I get periodically...
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.
Cats and avian influenza
The picture on the right is a Picasso painting entitled "Cat catching a bird". I often use this picture in presentations and ask "What if that bird was infected with avian flu?"
Avian flu is a tremendous concern at the moment. While it is not (currently) easily transmitted between people, bird-to-human infections have been reported in various countries. Mortality rates are very high, and the concern is that this strain could change to become easily transmitted between people, and lead to a pandemic (worldwide outbreak) not seen since the Spanish flu pandemic in the early 20th century. While birds and people are the focus, some attention has been paid to other species, such as cats.
Fatal avian flu developed in leopards and tigers in a zoo in Thailand during an avian flu outbreak. It was suspected that they ate infected chickens. Similarly, avian influenza in a pet cat was thought to have resulted from eating a dead pigeon (the pigeon presumably having died of avian flu). The potential role of cats in transmitting disease was highlighted by a study that reported that cats can become infected by eating infected birds, and can transmit avian flu to other cats.
While unproven, cats could theoretically play a role in transmitting this virus from birds to people. It's unlikely cats would be a major factor in a flu pandemic, but if such a situation were to arise, any possible source of transmission would need to be considered.
Should we worry about cats and avian flu right now? Worry....no. Be aware....yes. H5N1 avian influenza is not currently present in North America and it's hard to say if/when it will appear.
Should we think about cats when making plans for management of avian influenza if/when if reaches us? Absolutely. It's issues like this that get overlooked in outbreak planning.
Should I keep my cat inside? Yes. Outdoor cats are exposed to a large number of different infectious agents, including parasites and bacteria that can infect people. Outdoor cats can also get into fights, during which animals can transmit important diseases or cause nasty wounds. Also (obviously), an indoor cat isn't like to get hit by a cat...an important cause of premature death in cats.
Avian flu is just one more indication that our relationship with infectious diseases is much more complex than we've thought, and that broad (ecological) approaches to infectious disease control are required. We need to think about household pets when considering emerging infectious diseases because of the close and prolonged contact that millions of people have with their pets.
