Scott Weese
Scott Weese is an Associate Professor in the Department of Pathobiology at the University of Guelph, and Public Health and Zoonotic Disease microbiologist for the University's Centre for Public Health and Zoonoses. After graduating with a Doctor of Veterinary Medicine degree and spending time in private practice, he completed an large animal internal medicine residency and Doctor of Veterinary Science graduate program. He is board certified in internal medicine by the American College of Veterinary Internal Medicine and is Chief of Infection Control at the Ontario Veterinary College Teaching Hospital. He has an active research program focusing on infectious diseases, particularly those that can be transmitted between animals and people. He lives outside of Guelph, Ontario with his family and a collection of pets, including a dog, cat, fish and a herd of rare-breed sheep.
Cold weather + iguanas = botulism in dogs??
The Associated Press is reporting a concern about botulism in dogs in Florida that might be linked to dead iguanas. The facts are pretty sparse at the moment and it sounds like both the diagnosis of botulism and the link with iguanas are hypothetical, but it's an interesting story.
Botulism is a very serious, hard to treat and rare disease in dogs. It's also very hard to definitively diagnose, which is one of the problems in a situation like this. It seems that a veterinary neurologist first raised concerns after seeing paralysed dogs (and no evidence of typical causes) and a common history of exposure to dead iguanas.
The recent and prolonged cold weather in south Florida has apparently resulted in widespread deaths of iguanas (who do not tolerate cold weather). The iguanas presumably didn't die of botulism, but if they had Clostridium botulinum, the bacterium that causes botulism, in their intestinal tract (something that can be common in some animal species), dogs could ingest the bacterium or (more likely) botulism toxins that were produced by the bacteria in the iguana carcasses after death. Botulinum toxin is extremely potent and ingestion of minuscule amounts is enough to cause serious (including fatal) disease.
Testing is pending on some of the affected dogs. It would be nice if someone would test some dead iguanas as well, to see if there is really a link. This type of outbreak, however, often passes without a definitive diagnosis because of the difficulties diagnosing the disease. Regardless, keeping your pets away from dead iguanas (and other dead critters) is a good general rule.
Watch out for rabbit pee
Urine from healthy animals is typically considered to be of little to no risk to people. This is generally true, at least for the otherwise healthy human population, but like with most things in infectious diseases, there are exceptions. An interesting one in rabbits is a bug called Encephalitozoon cuniculi. This microorganism (now classified as a fungus, but previously considered a protozoal parasite) is very common in healthy pet rabbits. In fact, the majority of rabbits have antibodies against E. cuniculi and may have it living in their bodies, particularly in the kidneys. It can cause infection of the brain, and is an important cause of neurological disease in rabbits, but more often than not it lives within the rabbit without causing any problems. Rabbits can shed spores of this organism is their urine, although they mainly do this only in the first few weeks after they've become infected, and shedding after that may be intermittent.
E. cuniculi is one of a group of microorganisms that became much more important when the HIV/AIDS epidemic hit. While rarely a cause of disease in people in the pre-HIV era, E. cuniculi is recognized as a potential cause of infection in people with compromised immune systems, particularly people with AIDS. Infections of people with normal immune systems are extremely rare.
It's always a challenge deciding what to do with a microorganism that can be shed by a large number of healthy animals. One reference "strongly advises" routine testing of rabbits, but that makes no sense to me. Here's why:
- Screening always comes down to a question of what you would do with the results. If you get a positive antibody test, it means that the rabbit has been exposed sometime in its life, but that does not mean that it is necessarily still infected or shedding spores - so it's not really convincing.
- Tests can be done to detect spore shedding but they are not particularly reliable. Since infected animals shed spores intermittently, a negative result here isn't convincing either.
- If the animal is positive, what would you do? If the household has no immunocompromised people, I'd say do what you've always done, and pay attention to good hygiene.
- If the animal was "negative," I'd say do what you've always done, and pay attention to good hygiene... same as for a positive rabbit.
- If there is an immunocompromised person in the house, I wouldn't say to get rid of the pet, since there's no evidence that's necessary. There is also no evidence that treatment is useful to eliminate E. cuniculi shedding rabbits. If the animal is positive, immunocompromised persons should avoid contact with urine and feces, and use good personal hygiene... just as they should do if the rabbit is negative!
More information about E. cuniculi in rabbits can be found in our archives.
Kissing a frog might get you more than a prince
The Hollywood effect is quite real when it comes to various trends, including pets (remember the glut of Dalmatians after 101 Dalmatians?). I can understand how seeing a cute puppy of some breed might lead to people wanting to get one. However, when Disney's The Princess and the Frog was released, I didn't really think a lot of people who watched this movie were going to start running around kissing frogs. I assumed that some degree of common sense would apply. Apparently, I was wrong.
Various news outlets are reporting that at least 50 children (mainly kids under the age of 10) have become sick in the US after copying the movie's Princess Tiana by kissing frogs. There's not a lot of information regarding what they contracted, whether the illnesses were all clearly linked to frogs, or whether these were truly associated with the movie, but there are certainly disease risks associated with kissing a frog. While we pay more attention to reptiles as a source of Salmonella, the risk is also present with frogs, and the best thing is to do is assume that all frogs are carrying this potentially harmful bacterium. Accordingly, high-risk people (e.g. kids less than 5 years of age, the elderly, people with compromised immune systems) should have no contact with frogs - they shouldn't even be in the same house. Hands should always be washed after touching a frog, and no one should ever kiss a frog. The chances of living happily ever after with a prince are much lower than the chances of a nasty bout of diarrhea (or worse)!
Autism/vaccine link study now fully retracted
The medical journal Lancet has fully retracted the flawed 1998 study that raised a link between MMR (measles, mumps, rubella) vaccination and autism in children. This study fueled incredible debate and was a driving force in the anti-vaccination movement, and subsequent declines in vaccination rates were a key reason for the resurgence of measles. It also fostered general anti-vaccination sentiment that has continued to affect decisions regarding vaccination of people and animals.
The study has come under fire for years and has been highly controversial, with strong opinions on both sides. In 2004, the journal issued a partial retraction based on a conflict of interest of Dr. Wakefield's (the lead researcher), since it was revealed that he was being paid by lawyers acting for parents who believed their children had been harmed by MMR vaccination. The new full retraction goes much beyond this, and is based on problems that have been revealed with the scientific method, reporting of what was done, plus ethical issues pertaining to ethical committee approval.
The UK's General Medical Council ruled last week that Dr. Wakefield had shown "callous disregard" for the children involved in the study and acted "dishonestly." He faces being stripped of the right to practice medicine in the UK. Accordingly, all of the findings of this study are considered invalid.
Image source: http://www.dailymail.co.uk
Reptiles and infants don't mix
A recent report in the Journal of Pediatrics (Tabarani et al 2010) describes a case of infection around the brain, at the site of a previous subdural hematoma, in a five-month-old child. Four reptiles (all bearded dragons) were present in the child's foster household, but the foster parent reported that the baby did not have any contact with them. Salmonella Houtenae was identified as the cause of the infection. The reptiles were an obvious potential source given what we know about Salmonella and reptiles, the unusual Salmonella strain that was isolated from the baby, and the lack of any other obvious risk factor. All previous human infections caused by this type of Salmonella have been associated with reptiles, and all occurred in young children. Unfortunately, the reptiles in this case were euthanized before they could be tested.
This report highlights a few important points.
- Direct contact with reptiles is not needed to cause an infection. There are many reports of people (especially infants) being infected by Salmonella from a pet reptile despite them having no direct contact with the animal. The common statement that 'there's no risk to my child because my child is never allowed to touch the animal' is completely false.
- Reptiles should not be in households with children less than five years of age. In this report, the child was in a foster home. In some jurisdictions, reptiles are banned from foster homes for this very reason.
- The majority of reptiles carry Salmonella. This is expected and impossible to prevent. That's why people at high risk of serious infection (e.g. young children) should not be around them. It's also why euthanasia of the reptiles in this case was highly questionable. Why kill the lizards for carrying a bug that we assume they (and most other reptiles) normally carry? Finding them a new home that doesn't have high risk people would be more appropriate.
Image: Central Bearded Dragon (Pogona vitticeps) (photo credit: Eigene Arbeit, 2007)
Antagonzing piranha... Maybe not a good idea
Pet bites are a big p
roblem. Dogs bites in particular are far too common and can result in serious injury or even death in a small percentage of cases. Bites from other pet species also happen, but the extent of the problem is not clear. A good general rule is if it has a mouth, it can bite.
Another good general rule is if it has numerous sharp teeth, is a carnivore and your as upsetting it, you should get your hand out of the way. Pet store owner Dave Brown found this out the hard way, although in this situation he has the dubious distinction of having been bitten by a fish.
It seems that Mr. Brown was trying to catch a piranha that he was selling. I would have thought the standard way of catching a fish, not to mention a six-inch-long carnivorous fish, would be to use a net. Apparently not. Mr. Brown used 
his bare hands, and after a couple unsuccessful attempts to catch the fish, the piranha fought back, sinking his teeth into the store owner's thumb. The bite was severe enough that stitches were needed. According to Mr. Brown "There was blood everywhere. Every time I had him in a plastic bag the fish would bite through it. He was quite a feisty one." Personally, I think if a carnivorous fish was repeatedly trying to attack me through the bag, I'd probably change my approach to catching it.
According to a local fish expert, "[Mr. Brown] was very unlucky as these fish normally just attack when they're hungry. It may have been a bit peckish."
Fortunately, apart from a sore thumb, it sounds like the biggest problem Mr. Brown will face is the harassment that I assume he's going to take from friends after being bitten by a fish.
2008 Australian Hendra virus recap
The latest edition of the journal Emerging Infectious Diseases contains a paper describing the 2008 Australian Hendra virus outbreak in horses and people.
In this outbreak, there were five horses infected and two humans infected. The horses predominantly had signs of neurological disease, not respiratory disease like some other reports describing this disease. Four horses died. One recovered but was euthanized for public health reasons.
Two people became infected after working with the sick horses, which represents 10% of the total veterinary staff that were exposed to the infected horses. Both people started off with influenza-like illness, which seemed to improve initially, but then signs of severe neurological disease developed. They were treated with ribavirin, an antiviral drug, as part of an experimental treatment. One of them died after 40 days of illness, the other person survived.
The authors stressed that the effectiveness of ribavirin could not be determined, but they recommend it nonetheless because of the severity of Hendra virus infection and lack of other options. Ribavirin was also used in the 2009 outbreak, but it is clearly not 100% effective since one person died there also.
A number of concerning activities occurred that put people at risk of infection, including a "percutaneous blood exposure while euthanizing an infected horses" (they didn't explain exactly what this was, but it could have been a needlestick), low use of personal protective equipment, and contact with potentially infectious body fluids. This is unfortunately not surprising since the approach to infection control (particularly in terms of zoonotic infections) is often lax in equine medicine. That certainly has to change, particularly in areas where Hendra virus may be present.
Much more information about how to control this potentially devastating virus is needed. Fortunately, infections are uncommon and it is restricted to a fairly small geographic range in Queensland, Australia.
Image source: http://animalphotos.info/
This Worms & Germs blog entry was originally posted on equIDblog on 27-Jan-10.
More rabid raccoons in Central Park
Eight more rabid raccoons have been found in New York's Central Park over the past two weeks. These, plus the 12 rabid raccoons reported in the park last year, represent a major increase in disease frequency since only 1 rabid raccoon was identified in Central Park from 2003-2008. That's a concerning development given the number of people that visit this 843 acre park in the heart of New York city every day.
In response, the city's Health Department has started an education campaign to alert people to the risk, and tell people to stay away from wildlife, report any sick animals and to keep their dogs on leashes. Every pet owner also needs to make sure their dog's rabies vaccine status is up-to-date, even if they always keep their dog on a leash, because you never know what a rabid raccoon will do (such as attacking a leashed dog that walks by). There are also plans to vaccinate raccoons in and around the Park, however I couldn't find details about what type of vaccination program will be used.
Musings about antibiotic therapy in dogs and cats
I recently attended a meeting to develop antibiotic use guidelines for dogs and cats. One recurring theme during the discussions was our paucity of scientific evidence about how to use antibiotics in certain situations. It's really interesting when you compare antibiotic treatment regimens that are used in humans and standard practices for dogs and cats. Almost invariably, we treat dogs and cats for much longer periods of time than people, even when very similar diseases are compared. Why is this?
One reason is a lack of people doing research and the difficulty performing (and funding) the large clinical trials that are needed to evaluate different treatment protocols. For example, we tend to treat urinary tract infections in dogs for 7-10 days, while in people, just 3 days of treatment is much more common. However, longer treatment courses were used in humans until various research studies showed that shorter treatment was as effective and had fewer side effects. It's likely that we could treat urinary tract infections in dogs for shorter periods of time but we don't have the data to support it at this point.
It's possible that longer treatments for certain conditions are indeed needed in dogs and cats compared to humans. An argument to this effect is that disease in pets can often be more advanced (and therefore potentially harder to treat) when first detected than similar disease in people. For example, if someone has a urinary tract infection, they are probably going to get to their physician quickly. Many owners may not notice the signs of an infection in their pets as early. More established infections may take longer to treat. Does that really happen? We don't know, but it's something we need to know to determine proper treatment durations.
"If it ain't broke, don't fix it". This isn't a very good philosophy when it comes to medicine but it's understandable. If a certain treatment plan usually works, people are hesitant to look at alternatives. The problems with longer term therapy, such as adverse effects of drugs and development of antibiotic resistance, are not necessarily considered (but they need to be).
Bottom line: We need good research to determine optimal treatment protocols for pets. It's very likely that we can greatly decrease the amount of antibiotics that we use while improving patient care, but without good evidence, it's hard to know what to do and where to start. Being too aggressive and dropping treatment times in the absence of evidence may not be a wise decision - too short a treatment period could result in treatment failures and ultimately more sick animals and overall more antibiotic use.
Staphylococcus (pseud)intermedius meningitis in a child
A paper in the International Journal of Infectious Diseases (Durdik et al 2010) describes a case of meningitis in an 11-month-old child caused by S. intermedius. (Presumably, the bacterium was actually S. pseudintermedius and they’re behind the times on identification of / nomenclature of this bacterium). This is the first report of this bacterium as a cause of meningitis in people, and obviously it’s a concern because of the potential severity of meningitis. Fortunately, the child made a full recovery with proper treatment.
S. pseudintermedius is a normal inhabitant of the skin and other body sites in dogs, and is found less commonly in cats. In this case, the child’s family owned a dog, but the dog lived outside and no direct contact was reported between the child and the dog. Indirect contact, such as someone bringing the bacterium in on their hands after touching the dog, would certainly be a possible route of transmission. Unfortunately, the authors of this study did not investigate the dog as the potential source and there was no attempt to isolate the same bacterium from the dog. The dog is certainly a likely source of infection here since S. pseudintermedius is not commonly found in people, and when it is, it is often associated with dog-contact.
There seems to have been an increase in reports of Staphylococcus intermedius/pseudintermedius infections in people lately. Reports are still very rare but there have been a couple in the past six months. That could be because there are more infections, but it could also be that people are just writing up the cases or that labs are getting better at identifying the organism. Overall, the number of apparent human infections caused by this dog-associated bacterium is very low. While it is clearly a bacterium that can infect people, the risks to people in contact with pets is also very low. “Low” doesn’t mean “no”, however, and the very low but not negligible risk of S. pseudintermedius infection is just one of many reasons to pay close attention to good hygiene practices around pets, and ensure that your physician knows if you have pets.
