Although at times it may seem that winter is never-ending in parts of Canada, spring is actually only a couple of months away. Along with spring comes insect season, and along with insects comes more than a few viruses. One of these is the virus that causes equine infectious anemia (EIA). This pathogen is a retrovirus like the human immunodeficiency virus (HIV), but EIA only affects equids (e.g. horses, donkeys, mules). It's a very serious concern in the horse world, because horses become infected for life, and in Canada we have strict control measures to help prevent the spread of EIA into and within the country. Nonetheless, in 2013 cases were detected on numerous premises in BC, Alberta and Saskatchewan. Maps of the areas affected are available of the website of the Canadian Food Inspection Agency (CFIA).
To help horse owners understand more about this disease, the existing control program and the reasons behind it, as well as how they can help prevent the spread of EIA, we've created two new info sheets in collaboration with Equine Guelph and Equine Canada: a full-length version complete with references (9 pages) and a shorter summary version (4 pages). Both versions are now freely available for download from the Worms & Germs Resources - Horses page, along with our many other equine infectious disease info sheets.
When it comes to hand hygiene, there is an unfortunately all-too-common misconception that wearing gloves makes hand washing or using alcohol-based hand rub unnecessary. In veterinary and human medicine, gloves, like hand hygiene, are typically used for two reasons: to prevent spread of germs or chemicals from a patient/person/object/surface to a person’s hands, and/or to prevent the spread of germs or chemicals from a person’s hands to a patient/person/object/surface. However, gloves are not the infallible barrier to germs that many people would like to think they are. Here are a few reasons why:
- Even new gloves can have holes in them: The accepted quality control limit for defects in medical gloves large enough to leak water is 1.5%. That may seem relatively low, but when you consider the hundreds of gloves that may be used over time in a veterinary (or human) clinic, that can add up to a lot of potential hand-to-patient or patient-to-hand pathogen transmission.
- Gloves can be damaged during use: Glove tears or punctures during use can be extremely common, particularly for certain procedures involving anything pointy or sharp (e.g. equipment, teeth, claws) or long procedures. Studies have shown that glove punctures that may occur during surgical procedures are frequently undetected by the person wearing the gloves. Even though gloves may provide an added layer of protection for a time, proper hand hygiene before and after glove use helps reduce the risk of transmission when that barrier breaks down.
- Bacteria can multiply under gloves: Anyone who has ever had to wear any kind of rubber, latex or vinyl gloves for more than 5-10 minutes knows how sweaty and hot it can make your hands, so you can imagine the kind of sweaty soup that can accumulate when gloves need to be worn for even longer than this. That’s why hand hygiene before putting on gloves is so important for “clean” procedures like surgery, because it helps decrease the number of bacteria on the hands to start, and ultimately the amount that will grow back by the time the procedure is done. Hand hygiene after glove removal is important so the “soup” isn’t being spread to the next patient, person or object.
- We use gloves for the highest-risk procedures: Glove use is typically recommended for the cleanest procedures (i.e. surgery) and the dirtiest procedures (i.e. things with a high “ick” factor, like handling feces). A glove puncture in surgery could potentially lead to contamination of sterile tissues, resulting in a surgical site infection. A glove puncture (or contamination of the hands when removing gloves) when handling high-risk material like feces can lead to transmission of fecal pathogens to anyone or anything that person may touch afterward (including themselves). In a sense, hand hygiene is actually even more important in situations when gloves are typically worn!
Although proper glove use and hand hygiene applies primarily to veterinary and healthcare workers, there are times when glove use is also recommended at home (e.g. caring for pets with certain kinds of infections, higher-risk individuals performing certain tasks like cleaning up pet messes). Remember that gloves are not a substitute for hand hygiene - always wash your hands or use hand rub after taking gloves off. It is also important not to touch anything with your gloved hands that will later be touched by someone without gloves, and be sure to put used disposable gloves directly in the garbage.
We've just posted a new info sheet about Capnocytophaga. One member of this bacterial group in particular, Capnocytophaga canimorsus, makes the news periodically because it can cause devastating infection in some individuals, like the Ottawa woman who lost three limbs after one of her own dogs accidentally bit her. This kind of severe infection, which is also sometimes called dog bite septicemia, is actually quite rare, but people with certain risk factors such as diabetes, alcoholism, and particularly lack of a functional spleen are at much higher risk. The bacterium very commonly lives in the mouths of dogs and cats, and is considered a part of the normal oral microflora in these animals. People are therefore commonly exposed to Capnocytophaga, yet infection is rare, but because it can be so catastrophic it's important to know the facts, especially if you or someone you know may be at higher risk.
You can read more about Capnocytophaga on the new info sheet, which you can find along with all our other info sheets on the Worms & Germs Resources - Pets page. You can also read about Capnocytophaga in the posts in our archives.
One of our most frequent pieces of advice on W&GB when it comes to kids is to always make sure they are supervised when they are around pets. This is important for at least two major reasons, one being avoiding potential high-risk contacts when it comes to infectious disease transmission (e.g. face-to-mouth, hand-to-bum), and the other being reducing the risk of injury (and subsequent infection) from bites and scratches. Children often don't know or aren't aware of the signs that a pet is stressed or uncomfortable, essentially forcing the pet to take progressively more drastic measures to get its message across, potentially ending in a snap or a bite. The problem is a lot of the time the supervising adult also doesn't know these signs, and thus many a bite or scratch may happen even when a parent is watching carefully from only a few feet away.
Yesterday I came across an excellent post on this very topic on another blog written by Robin Bennett, a certified professional dog trainer (CPDT-KA) in Virginia. Her post was very aptly entitled "Why Supervising Dogs and Kids Doesn't Work." Click on the title to see the entire post, but here are a few of the great points she makes:
- Watch for inappropriate child behaviour. In Robin's words, "Don’t marvel that your dog has the patience of Job if he is willing to tolerate [being poked, prodded, yanked, pulled, pushed, etc]. And please don’t videotape it for YouTube! Be thankful your dog has good bite inhibition and intervene before it’s too late."
- Intervene early. If the dog loses that loose, wiggly body posture and starts to stiffen up, don't wait until the animal has to escalate its message to growling or snapping to step in.
- Support the dog's good choices. If the dog chooses to move away from a child because it is uncomfortable, support that choice and don't let the child continue to follow the animal. If the pet can't get away, it may scratch or bite to try to make the child go away instead. Don't force the dog to make that choice. (This applies equally to cats or any other pet!)
It's very important for pet owners to educate themselves about basic pet behaviour, whether they have dogs, cats or other animals, and to teach that same information to their children. Another great program that teaches kids how to behave around dogs, and unfamiliar dogs in particular, is the "Be a tree" program, details of which can be found on the Doggone Safe dog bite prevention website.
The latest Worms & Germs infosheets are all about some common and not-so-common members of a particular group of parasites: tapeworms. There are a number of different groups and species of tapeworms that can infect pets, people, and other domestic animals, and sorting through which is which can be tricky, so we created a Tapeworms infosheet to help sort out the details.
There is one group of tapeworms in pets that is a particular concern from a zoonotic disease perspective. These parasites belong to the genus Echinococcus. Normally these tapeworms circulate in the wildlife population, mostly in wild canids such as foxes and various prey species, but they can also affect domestic dogs (and sometimes cats) that scavenge or hunt the same prey. In most cases the pet does not become sick, but people who are exposed to the tapeworm eggs in the pet’s feces can develop slow-growing cysts known as hydatid cysts or alveolar hydatid cysts. Over time these cysts can become very large and difficult to treat. There is also now evidence that one Echinococcus species (E. multilocularis) may be spreading - in 2012 a dog in Ontario was found to be infected with the cystic form of E. multilocularis (which is unusual in itself), but the animal had no history of travel outside of the province, therefore it was most likely infected via local wildlife.
Because echinococcosis can be such a severe disease in people, we created an additional infosheet focused on just Echinococcus. Both infosheets can be found on the Worms & Germs Resources - Pets page.
Image: Dozens of Echinococcus granulosus tapeworms from the small intestine of a dog. Although these adult tapeworms are tiny compared to some other species, this species can cause significant problems in people through the formation of hydatid cysts. (Photo credit: Ontario Veterinary College)
I read an interesting article earlier this week that I felt was worth sharing. The article, which appeared in the Huffington Post, is entitled “7 common myths about pandemics and new diseases” written by Dr. William Karesh, executive VP for health and policy with the EcoHealth Alliance. It talks about several misconceptions a lot of people have when it comes to emerging diseases (including zoonoses) and the effects they can have at both local and global levels. Here are a few points from Dr. Karesh’s article (for more details click on the link above):
- Pandemics and new diseases are not just a public health problem, as they can have significant effects on many sectors of the economy. It’s been estimated that the SARS outbreak in 2003 cost the global economy $30-$50 billion. Even diseases that infect only animals and not people can have a huge impact on everyone - just ask anyone who’s lived through a Foot-and-Mouth Disease outbreak.
- There are a lot of infectious diseases out there already (i.e. they're not necessarily "new") about which we know little to nothing. As much as we would like to think that doctors can diagnose just about anything with the right test, the ~1400 infectious pathogens that we know about are really just the start. There’s a good chance that some of those fevers, pneumonias and other vague and not-so-vague illnesses are caused (or perhaps triggered) by pathogens that we are simple unable to detect at this time. The potential for "new" pathogens to reach the human population also continues to increase as we encroach more and more on previously untouched wilderness (and the animals living there) in various parts of the world.
- International organizations like the World Health Organization (WHO) and the World Organization for Animal Health (OIE) are extremely important for helping guide and coordinate infection control efforts in many countries, but they have limited resources and budgets. Furthermore, only the governments of the countries in which outbreaks occur have the ultimate authority to take action at ground zero where it’s needed most.
- Although globalization provides means for pathogens to get from one side of the world to another in only a matter of hours (as we’ve discussed several times on this blog before), the same phenomenon can also help us respond better to emerging disease threats - samples can be relatively rapidly transported to specific labs for testing, experts in almost any part of the world can be reached quickly for consultation, and test results and recommendations can be communicated to everyone involved almost immediately.
Remember that we all have a role to play in public health, both as “global citizens, as Dr. Karesh points out, and I would add also at our own local level. Public health personnel work hard to establish policies and regulations to help prevent infectious disease outbreaks and ensure a safe food supply, and to provide people with the necessary information to make sound decisions with regard to protecting themselves from illness. In the end, public health requires action by the public. The little things we each do can add up to have a huge impact, even things as simple as washing our hands regularly, cooking food thoroughly, picking up after our pets outside, properly training pets not to bite or scratch, keeping our animals (be they large, small, common or exotic) as healthy as possible, and being aware of the disease risks associated with keeping animals and how to minimize them. Every drop in the bucket counts, no matter how small it may seem, and by having these habits and practices in place in advance, we will (hopefully) all be better prepared to deal with the next emerging disease - from wherever (or whatever) it comes.
We've just posted a new info sheet about cat scratch disease (CSD), which is caused by a bacterium (Bartonella henselae) commonly carried in the bloodstream of healthy cats. Signs of CSD in people can be quite non-specific, so (as always) it's important to let your physician know if you've been bitten or scratched by a cat if you're feeling ill, so that CSD is considered. Other than proper training and handling of cats to avoid bites and scratches, the next most important component of CSD prevention is flea control.
You can read more about CSD and B. henselae on the new info sheet, which you can find along with all our other info sheets on the Worms & Germs Resources - Pets page. You can also read about CSD in the posts in our archives.
It's been quite a while since the last post about MRSA in horses, but rest assured, it's still out there! Not too surprisingly it's also spreading (or at least starting to be found) in new places. A recent report in Veterinary Microbiology (Schwaber et al, 2013) describes an MRSA outbreak at a large animal teaching hospital in Israel. It is the first report of MRSA colonization in horses in the Middle East, although it's possible (and quite likely) that there's more to be found.
The discovery of the problem had a pretty typical progression: there were two horses in the hospital with post-operative wound infections from which Staphylococcus aureus was cultured, and the isolates from both horses had similar antimicrobial resistance patterns, including resistance to all beta-lactam antimicrobials (= MRSA). Validly concerned about the potential for the MRSA to spread among horses and people in the hospital, an investigation ensued - in this case the National Center for Infection Control (NCIC) was actually called in to coordinate the operation.
- They found MRSA in 12/84 (14.3%) horses, of which 11 were in the hospital at the time of sampling, and 1 had recently been discharged from the hospital. Consider though that 44 of the horses sampled were simply from farms from which an MRSA-positive horse had come - so 11/40 horses in the hospital were positive - that's 27.5%!
- 16/139 (11.5%) of personnel at the teaching hospital were positive for MRSA. Fortunately there were no clinical MRSA infections reported in people.
- The MRSA strain that was found in all the horses and most of the people was a very rare type - not the usual sequence type 8 (ST8) we're used to finding in horses in various other parts of the world. This one was an ST5, spa-type t535, SCCmec type V, which is even rare in the human population.
- The primary action taken to get the outbreak under control: increased infection control measures, including isolation of infected and colonized horses which were then handled with contact precautions (e.g. gloves, gowns), discharging horses from hospital as soon as medically possible to decrease transmission pressure, and having a nurse from the NCIC come in to instruct personnel on the measures to be taken, including emphasis on hand hygiene and increased use of alcohol-based hand sanitizer.
- In this outbreak, decolonization therapy was prescribed for all colonized personnel.
The report does not mention whether or not personnel at the hospital were required to submit to being tested and undergoing decolonization therapy. This can be a very tricky issue to handle, and it depends on what the local laws are. In Canada, employees cannot be forced to undergo testing or treatment, but in some other countries MRSA-positive healthcare workers may not be allowed to even work until their carrier status is cleared.
Interestingly enough, just a year or two before this outbreak occurred a study (as yet unpublished) had been carried out in the same region, during which they found MRSA in 7.2% (6/83) of hospitalized horses and none in horses from local farms. There is no mention regarding whether or not the hospital had taken measures to eradicate MRSA from the facility before the clinical infections that triggered the outbreak investigation occurred.
This was a typical MRSA "iceberg" - a couple of clinical cases were triggers for an investigation that found a lot more horses and people were actually carriers. This is exactly why it's important to remain diligent about infection control measures like hand hygiene at all times, so that pathogens like MRSA don't move in "under the radar." The authors of the paper summed it up nicely (although I'd leave out the part about decolonization):
"Strict implementation of hand hygiene, isolation of colonized and infected horses, decolonization
of colonized personnel and above all, constant education of veterinary students and personnel about the importance of infection control measures are required in order to decrease the risk for colonization and infection of both horses and personnel by MRSA and other pathogens."
More information about MRSA in horses is available on the Worms & Germs Resource - Horses page.
This week an article on TheHorse.com discussed the current situation in the western provinces of Canada with regard to equine infectious anemia (EIA). The prairies are seeing the highest number of EIA cases in years, with more than 70 horses affected on 22 different properties.
Also commonly called "swamp fever," EIA is caused by a retrovirus, similar to the human HIV. There is currently no vaccine against virus, and once infected a horse carries the virus for the rest of its life. Although EIA can cause severe clinical signs (including high fever, weakness, swelling of the lower limbs and along the ventral abdomen, and even sudden death) most horses that are diagnosed are not showing any signs of illness at the time, or may show milder, non-specific signs such as exercise intolerance and intermittent fever. Affected horse of course also have varying degrees of anemia as the name suggests. Episodes of more severe signs can occur even years after the initial infection, and during these episodes an infected animal poses the greatest threat to other horses because the viral load in the bloodstream is very high. The virus cannot be transmitted directly between horses though - it is transmitted by blood, typically via blood-sucking insects like like deer flies, horse flies and stable flies (hence the association of the disease with swamps) or by reuse of needles for injections. Fortunately EIA does not affect humans or any other animal species. It has also not been shown to be transmitted by mosquitoes.
Because infection is life-long, in order to control the disease the only options for positive horses are euthanasia or life-long quarantine in a building with rigorous insect control to prevent spread.
The question is, why the sudden spike in the number of cases out west? There are a few possibilities:
- Possibility #1: There's been one, or a few, small local outbreaks that were initially caused by a very small number of positive horses that likely brought the virus back with them from somewhere to which they had traveled. Hopefully this is the case, and testing has identified all the horses that were subsequently infected so that the virus won't spread further. EIA testing is required prior to travel to many places and prior to participating in many competitions or shows. Regular testing of animals that travel frequently helps to identify infected animals more quickly.
- Possibility #2: For whatever reason, there are a bunch of horses being tested this year that have not been tested in the past, and they're coming up positive. This would be much more concerning, because there's no way to tell how long a horse has been infected if it has not been tested in the past. The longer an infected horse is around outside of a fly-proof quarantine, the greater the chance that an insect (or a needle) will transmit the virus to another horse.
- Possibility #3: There are number of infected horses across the prairies that have not been tested, and the virus has been slowly spreading from these index cases and has finally reached part of the horse population that does get tested regularly. This would be the worst case, as it would mean that there's a reservoir of infected horses that is still not being identified, and could continue to perpetuate the infection.
In the end, only time will tell which of these scenarios (or a combination of them) is playing out in western Canada. Although a relatively low population density (of horses as well as people) in provinces like Saskatchewan helps to decrease the transmission pressure (simply by making it harder for an insect carrying the virus in its mouth parts from one horse to find another horse to bite), gatherings of horses for shows, trail rides and the like (particularly when EIA testing is not required) still create prime opportunities for transmission of the virus.
There are also a few things you can do to help decrease the chances of your horse contracting EIA:
- Protect your horse from biting insects that transmit EIA (which will simultaneously help protect your horse from insects like mosquitoes that can transmit other viruses). Use fly repellants, fly sheets, and avoid turnout during times of peak insect activity (dusk and dawn).
- Never reuse needles, especially between different horses. Also ensure that any other equipment that may be used on your horse (e.g. mouth gags) are always properly cleaned between animals and free from any blood contamination.
- Avoid proximity to horses of unknown EIA status. This can be tough to do if your horse goes to shows where EIA testing is not mandatory, but particularly with the current problems out west (or anywhere else that EIA may be circulating) testing for EIA prior to any event where there will be a gathering of horses should be strongly promoted.
Testing for EIA can be done with a simple blood test. This used to be called a Coggins test, but now a more accurate ELISA-type test is used to test for the disease instead.
Image: Cross-section of the EIA retrovirus (source: USDA Animal and Plant Health Inspection Service)
I love my cats. But sometimes when Bonnie and Clyde are living up to their names, puking up hair balls twice a day, peeing on the guest bed (yes, contrary to popular belief even vets can't stop their own cats from doing this sometimes), caterwauling at 3 AM, or begging for food all afternoon, they do make me c-r-a-z-y crazy - but they're not making me suicidal.
In yet another example of how the media will present study results in the manner that will sell the most newspapers or magazines, rather than the way that helps people interpret the results in a logical manner, comes an article entitled "Is Your Cat Hosting a Human Suicide Parasite?" The article talks about a study recently published in the Archives of General Psychiatry (Pedersen et al. 2012) which looked at a cohort of 45 788 women in Denmark who gave birth between 1992-1995, and found a statistically significant association between self-directed violence (including suicide attempts) in these women and their antibody titre to Toxoplasma gondii at the time of birth. The risk in seropositive women was 1.53 times greater than the risk in seronegative women.
Toxoplasma gondii is a parasite that is shed in the feces of cats, which are the parasites definitive host. Most house cats only ever shed significant amounts of the parasite the first time they're exposed to the parasite (typically when they're young). Depending on where people live and various cultural practices, transmission of the parasite from scooping out litterboxes may actually be relatively uncommon compared to other possible sources including exposure from soil (e.g. working in the garden and then not washing one's hands), eating unwashed vegetables, or eating some types of undercooked meat.
The most glaring limitation of the Pedersen study is that they didn't control for any other factors that may have resulted in the women who committed acts of self-directed violence being more likely to be seropositive for Toxoplasma than others. For example, women with mental illness may be less likely to practice good hand hygiene (one of the most important factors for reducing the risk of parasite transmission), and therefore more likely to be exposed to Toxoplasma, or there may be other factors about their health or their lifestyle that make them more prone to infection. The point is the authors only found an association in a specific subset of the population (Danish women who had given birth to at least on child). This does not mean that the relationship is causative - they can't say that Toxoplasma infection makes people more prone to self-directed violence, only that women - in this particular group - who were seropositive for the parasite were also at increased risk for this kind of behaviour. It's a somewhat subtle but very important difference. The authors of the study clearly acknowledge the limitations of their work, but the news article does not do quite as good a job of pointing this out, until right at the very end where it does finally get mentioned.
Does Toxoplasma infection cause behavioural changes in rats that may make them more likely to wander into a cat's territory and be eaten? According to an experimental study it can, and it does make a certain amount of ecological sense that the parasite could have an effect on its intermediate host (the rat) that makes it more likely to be able to continue its life cycle (via being eaten by a cat) by reducing fear in the rat. Could infection of the brain in humans cause subtle behavioural changes? I can't deny the possibility, but humans are not rats and I would be very wary of extrapolating results from one species to the other. But is this parasite likely to "drive our brains off the highway" as the news article says? I'm not ready to buy that, certainly not based on this study. As the authors clearly state in the first line of the paper "Suicide is a tragic multifactorial outcome of mental illness, with complex biopsychosocial underpinning..." There are so many things that contribute to such an unfortunate outcome that a lot more work is needed before anyone can justifiably blame a "suicide parasite" in cats.
Whether you believe Toxoplasma infection can result in behavioural changes in people or not, there are some very simple steps everyone can take to help decrease the risk of becoming infected with this parasite regardless. These are particularly important for individuals who are immunosuppressed and women who are pregnant, because it is very well established that toxoplasmosis in these high-risk individuals certainly can have severe repercusions to either the individual or the unborn fetus. However, it is by no means necessary for such individuals to get rid of their cats if they take these simple precautions:
- Clean your cat’s litter box every day. The oocysts shed in cat feces usually take about 24 hours to become infective once they’ve been passed, so daily cleaning helps remove them before they reach this stage.
- Always wash your hands with soap and water after cleaning your cat’s litter box, after working in the garden or in any soil, and after handling raw meat.
- Keep your cat indoors. Outdoor cats are more likely to be exposed to Toxoplasma and shed oocysts in their stool.
- Keep sandboxes covered so outdoor cats don’t contaminate them with stool.
- Cook all meat, especially pork, lamb, mutton and wild game, to an internal temperature of 67ºC/153ºF or higher.
More information about Toxoplasma can be found on the info sheet on the Worms & Germs Resources page.