I keep saying spring is approaching and I keep getting disappointed by the cold weather. But it’s going to happen soon, so we’ve been gearing up for tick season. There are a few new initiatives underway for tracking ticks and tickborne diseases in Canadian dogs and cats. Check out the recent post at PetsAndTicks.com for more information.
The snowfall we had on the weekend notwithstanding, spring is here. As the weather warms up in Ontario (and other regions), we have to once again think more about ticks. Once the temperature reaches ~4C, hungry ticks that didn’t feed in the fall will come out, looking for food. Accordingly, tick prevention for people and pets needs to be considered.
The return of ticks also means the return of pet tick preventative advertising, and that’s leading to confusion and questions. The “Lone Star Louie” ads, in particular, are leading to a rash (pardon the pun) of emails. They focus on the Lone Star tick (Amblyomma americanum), but also include some confusing, mixed and misleading messaging, talking about this tick in dogs, red meat allergy and Lyme disease.
First, the concern about the A. americanum…
The Lone Star tick is an aggressive tick that can spread a few different diseases. We’re paying more attention to it in Ontario now because we expect it to become a problem over time. We see small numbers every year, and so far we’ve assumed that these are ticks have been carried north by migrating birds. Established populations (i.e. finding all life stages of the tick at a particular location, typically over at least a two year period) have not been recognized in the province (yet). However, we’re on the look out for it through initiatives such as our Pet Tick Tracker.
Next… questions about the advertising
Red meat allergy
- This is a really interesting story but one that has no relevance to dogs and cats. Lone Star tick bites can result in an acquired red meat allergy in people. It’s uncommon, but bites from this tick can result in sensitization of peoples’ immune systems to a protein that’s found in red meat. People can get sensitized to it because it’s not a component of their bodies. In contrast, dogs and cats are made of that protein, so they can’t develop the same kind of red meat allergy (i.e. an allergy to themselves). So, while it’s a concern with this tick, it’s of no relevance to dogs and cats, and dogs and cats do not lead to people being exposed to the tick or developing the meat allergy.
- Lyme disease gets mentioned in the ad too, but this tick does not harbour the bacterium that causes Lyme disease (Borrelia burgdorferi). That particular pathogen is most often carried by black-legged ticks (e.g. Ixodes scapularis).
So, the Lone Star tick is a concern (albeit still a minimal one in Ontario). However, red meat allergy messaging is irrelevant to marketing tick preventives for dogs and cats, and Lyme disease is not a risk from this tick. Tick prevention is important in dogs (and to a lesser degree cats) and the use of tick preventative medicine is an easy and effective way of reducing the risks associated with ticks. The messaging needs to be better, though, to avoid confusion and misinformation.
Raw diets have been in the news a lot lately because of Salmonella contamination. It’s not surprising at all since bacteria like Salmonella, E. coli, Campylobacter and Listeria are expected to be found in raw meat (that’s why we cook it). We know that dogs and cats fed raw meat are at increased risk of shedding bacteria like Salmonella, sometimes with serious consequences to the animals or their owners.
Reducing the risk is a challenge when you know there’s a reasonable chance the food is contaminated, and when the preferred method of control (cooking) isn’t used. Irradiation is an alternative approach, but not something in which a lot of raw feeders are probably interested. High pressure pasteurization (HPP) is therefore increasingly being used to help control bacterial contamination of these products. HPP, as the name suggests, uses high pressure (with minimal increases in temperature) to reduce bacterial loads.
Notice I said reduce, not eliminate. That’s the problem.
A while ago, I used to go on the assumption that raw food products that underwent HPP were similar in risk to commercial cooked diets, with the disclaimer that we don’t really know for sure. We still don’t know a lot, but what we know now isn’t encouraging, so I’ve had to change that assumption.
I’ve talked to a few people who have done limited investigations of foods treated with HPP, and the results were disappointing. Unfortunately the studies were small and remain unpublished.
A 2016 research abstract gives us a bit more substance (although a proper research paper would be preferred). In that study (Hasty et al. 2016, Reciprocal Meat Conference – Meat and Poultry Safety), raw beef pet food was spiked with E. coli. (A harmless strain of E coli was used in place of a disease-causing strain or other bacteria like Salmonella, presumably because of biosafety concerns.) They used a HPP process that subjected the meat to a standard pressure (600 mpa) for 480 seconds. Then they checked to see if any viable bacteria were left in the meat.
The good news: There was a definite reduction in viable bacteria.
The bad news: It didn’t kill them all.
This doesn’t mean HPP is ineffective. It’s a matter of being aware of what it can do, and what it can’t. It can reduce the number of viable bacteria in the food, and that probably reduces the risk of disease in people and pets. But it does not eliminate all the bacteria, so it can’t eliminate the risk (only proper cooking and handling will do that).
If someone is going to feed a raw diet, I’d still recommend using a HPP-treated diet versus one that has bot been treated. However, people have to realize it’s not a panacea and that they still have to assume the food is contaminated.
Here’s a quick reminder of some basic take-home messages for raw meat feeding:
- There’s always some risk of bacterial contamination. We can reduce, but not eliminate, that risk.
- Careful handling is required to prevent cross-contamination of human foods, surfaces and environments. A little common sense when it comes to food handling can go a long way (but it’s amazing how uncommon “common sense” can be… check out Barfblog.com for annals of food safety stupidity).
- Raw meat diets should not be fed to dogs and cats at increased risk of serious disease (e.g. very young, elderly, pregnant, immunocompromised) or in households where people (or pets) fitting those categories are present.
- People who feed raw diets should make sure their veterinarian knows this, should their pet get sick. The same applies on the other side of the One Health spectrum – if someone is feeding raw meat to their pet and a person in the household has gastrointestinal disease, exposure to raw meat needs to be mentioned to the physician involved.
I guess we’re not the only ones dealing with Brucella canis issues lately. In February, we were dealing with B. canis in dogs imported into Ontario from South Korea. Currently, we’re dealing with a larger issue in commercial dog breeding facilities in Ontario.
Imported Brucella canis also appears to be an issue in the US at the moment. Two dogs from South Korea that went to Wisconsin were recently diagnosed with brucellosis. They originated from a larger shipment of dogs from South Korea, and I have to wonder whether they’re from the same batch that came to Canada in February in which we found infected dogs (maybe they were even tested in response to what we found). Regardless, the imported dogs and the dogs that were exposed to them (a total of ~100 dogs) are under quarantine at the moment. Owners of dogs from the exposed group that have already been adopted are being contacted by state public health officers to instruct them to quarantine (and presumably test) the dogs.
The article was picked up by ProMedMail, with the following moderator comments:
“The lax import regulations of rescue animals coming into the USA is on the verge of a serious problem. The USA has quarantine facilities at ports for cattle, horses and other livestock. It needs to be expanded to include dogs and likely other animals. Imported rescue dogs especially need to have their vaccinations for prevention of rabies, distemper, parvo virus and other diseases. While being held at a facility, they should be checked for other diseases such as canine influenza and zoonotic diseases such as brucellosis.
Rescue animals from other countries need to be quarantined, not put in foster homes where there could be exposure to other animals or immunosuppressed individuals until some of these vaccines and testing have been performed. These quarantine facilities should be inspected by knowledgeable individuals according to law.”
Great in theory but it’s never going to happen. All we can realistically do is educate to improve importation practices to reduce the risks, but the risk will never be eliminated completely so long as dogs are crossing the border.
Rabies vaccination of dogs is legally required in many areas. In most of those, it must be given by a veterinarian, unlike some other vaccines that can be purchased from a veterinarian or supplier and administered by owners.
Why does a veterinarian have to administer rabies vaccines? There are a few reasons.
- One is that it helps ensure that the vaccine is handled properly. In a vet clinic, where vaccine handling and storage is routine, there’s less chance of the vaccine being handled inappropriately (e.g. left out of the fridge for a prolonged time). Poor handling, especially failing to maintain “cold chain” (keeping the vaccine cool at all times until it’s administered) is a particular concern in other situations.
- Having a vet administer the vaccine also decreases the risk of problems caused by inappropriate administration (e.g. not getting the full dose into the animal).
- There can also be a greater assurance that if a vet signs a rabies certificate, that the animal was actually vaccinated, as opposed to if a person just says they vaccinated their own dog. Veterinary records are also presumably better at recording when the vaccine was given, what vaccine was given and the lot number, all things that can be relevant.
A recent case in Texas highlights this issue. A dog in El Paso County was diagnosed with rabies, and while the news article isn’t particularly detailed, it’s stated that the owner gave the dog a rabies vaccine. The health department was unable to confirm where the vaccine came from or who gave it (and I assume we have to wonder whether it was actually vaccinated… maybe they just said it was, or maybe they vaccinated the dog against something else and only thought they’d vaccinated it for rabies).
Rabies vaccine is a highly effective vaccine, so I doubt the dog was vaccinated properly (and currently) vaccinated given that it developed rabies. If it was, I wonder if it was a very poorly handled vaccine or a cheap vaccine purchased from a questionable source, versus a mainstream veterinary vaccine. Vaccine failure from a properly administered, adequate quality vaccine is exceptionally unlikely.
While rabies in dogs and cats is quite rare in Canada and the US (and most countries that don’t have endemic canine rabies variant circulating in the feral dog population), it’s an almost invariably fatal disease, so we take it very seriously. Vaccination of pets is important to protect pets and the public, and the cost of a vet administering the vaccine is a lot less than the cost, hassles and risk from inadequate vaccination resulting in exposed animals getting infected.
I’ve had a few discussions with people over the past week about geographic variation in disease risk. It’s a great subject because it’s an important and often overlooked issue. Whether it’s animals being imported, animals moving with their owners, animals accompanying owners on vacation or animals being moved between regions within the county, movement between regions can involve picking up or moving diseases at the same time.
From a veterinary standpoint, the challenge is identifying issues that you wouldn’t normally consider, because the disease is rare or non-existent in your practice area. The first step is querying travel history (which is done variably well). The next is figuring out what that means. We don’t have great resources that say “if you go here with your dog, this is what you need to be concerned about.” I get questions about travel risks all the time, and it’s taken a lot of effort to get up to speed with risks in different regions (and I still have a lot of gaps). We’ve published the odd (crude) map to help out, but getting good quality information, ideally based on surveillance data, and assimilating it into a central resource is a more significant challenge than one might think (a goal of ours, for sure, but a slow process given time and money limitations).
Regardless, we’re getting more information all the time and getting that out in the open is important. Dr. Michelle Evason wrote a post on her K9 Lifetime Study blog about the leptospirosis data we’re working on, and I thought that was worth putting up here too. It’s a fairly high level map of a few years of leptospirosis cases in dogs in Canada, based on data from IDEXX Laboratories. There are limitations with any dataset of this kind, so it’s not a perfect representation of this disease. However, it still provides some useful information. Lepto is a nasty disease and also a vaccine-preventable disease. So, understanding where it’s common is important for thinking about it when you have a sick dog (i.e. making a diagnosis) and discussing vaccination programs.
The incidence is adjusted for human population, on the assumption that dog ownership trends are similar across the country. We do that so that we don’t see bias towards big cities. If we just plot the number of cases, places with a big dog population but low incidence of disease could have more cases than a true high risk area with a lower population, thus hiding the real risk.
This bacterium lives in different wildlife hosts (e.g. raccoons, rodents), is passed in their urine, and survives well in moist, temperate climates. Unsurprisingly, we see lepto concentrated in much of Ontario and east of here, particularly in southern regions, as well as coastal British Columbia. Risks vary within those regions too, and lepto vaccination discussions require some assessment of other risk factors as well (although I consider lepto vaccination a core vaccine in most of the green (and all of the blue) regions on this map).
We’ve studied Clostridium difficile in my lab for years and we probably have one of the world’s most diverse collections of this important bacterium. We have thousands of isolates from people, pets, livestock and many different wildlife species (as well as from meat, vegetables and water). Most of the focus on C. difficile involves human disease, which makes sense because it’s a very important cause of serious gastrointestinal illness in people. It causes disease in some animal species, but in many, it doesn’t seem to ever cause a problem.
Looking at the genetic makeup of a bacterium, it’s possible to infer how old it is. C. difficile is pretty ancient. It’s been estimated that in emerged 1.5-85 million years ago (He et al. PNAS 2010). That’s well before humans (or potentially even mammals) emerged, so it’s clearly not a human-origin bacterium. Rather, it evolved in wildlife and certain strains have made their way into people.
That’s a long introduction for a paper we just published about C. difficile in polar bears (Weese et al. Anaerobe 2019).
Why polar bears?
Usually, we do “hypothesis driven research,” where we come up with a specific answerable question or problem and try to answer or solve it (or some small part of it).
Sometimes, we’re opportunistic and curious, with less of a real plan. Here, it was basically someone saying “we have polar bear poop… is there anything you’d like to do with it?” Sometimes these curiosity-driven studies are quite rewarding.
We got samples from a large study that was collecting feces from wild polar bears in the Canadian Arctic, bears temporarily housed in the Polar Bear Jail in Churchill, Manitoba (a facility to where nuisance bears get shipped for a while before being released back into the wild), and a few polar bears from a zoo.
Surprisingly, we found C. difficile in almost 17% of samples: 18/120 (15%) from wild bears, 4/7 (57%) from the polar bear jail and 2/16 (13%) from the zoo.
To be honest, my first thought when we had so many positive results was “crap, contamination” (pardon the pun). However, typing of the bacterium showed us this was not the case. We found a variety of C. diff strains, but none of the strains in the in the wild bears were the same as strains we’ve ever seen. Also, the strain distribution was different in bears from the M’Clintock Channel compared to those from Hudson Strait (two different bear populations), despite the fact that the samples were all processed together in the lab. (So it couldn’t have been contamination at the lab level – that made me feel a lot better.)
Were the polar bears sick?
It’s hard to say, but probably not. Fecal samples were collected off the ice or ground, not right from the bear (for pretty obvious reasons). Presumably, like most wildlife species, C. difficile can be present in the gut of polar bears without causing disease.
How do polar bears get this bacterium?
We’ve been able to find C. difficile in most species that we’ve studied. That includes most livestock species, pet species and a range of wildlife, from raccoons to bats. It’s also been found in seals (not in the Arctic, but I’m not aware of anyone looking there). Since seals are a common food source for polar bears, if the bacterium is present in seals in the Arctic, that’s a likely source of exposure.
Does C. difficile-shedding in polar bears pose a risk to people?
I guess. However, there are lots of ways that we can get exposed to this bacterium. It’s possible we get exposed to low levels of it most days. If you’re close enough to the polar bear to get C. difficile from it, you probably have bigger things to worry about.
I’m taking a Brucella break to post a few interesting rabies stories.
A rabies warning was issued to residents of Taloyoak, Nunavut in response to identification of rabies in “a number” of dogs and foxes (I’m not sure what that number is).
This isn’t really new, as Arctic fox rabies is an ongoing endemic concern in northern Canada, including all of the territories. But it’s also an issue for other areas in Canada, because dogs are periodically shipped from Nunavut to southern regions. Vaccination rates are more variable in remote communities due to accessibility and population control issues, increasing the risk that rabies in the wildlife population could spillover into the dogs. Multiple dogs with rabies have been moved out of Nunavut to multiple provinces in the past.
Skunks are a natural rabies reservoir in some regions, as an Arizona man found out recently. He was bitten by a skunk, which was subsequently determined to be rabid. Why, exactly, he was close enough to a skunk to be bitten is another question, and one that wasn’t evident in the news articles I saw. I don’t think people need a reason beyond getting sprayed to stay away from skunks, but rabies is another good one.
…depending on the type of car. A woman was bitten by a stray kitten she was trying to feed outside Everglades National Park (take home message #1: stay away from wildlife and stray animals). She underwent post-exposure prophylaxis at a local hospital, only to later recieve a rather shocking bill of $48 512 (no, I didn’t misplace a decimal point). $46,222 of that was for the single immunoglobulin (antibody) injection she received. I don’t understand the US healthcare system, but that seems more than a little crazy. It seems even crazier based on a statement that the cost would have “only” been $9900 if she was bitten a couple of months later, after the hospital lowered its price. I guess someone made a nice profit off her rabies exposure.
Goats aren’t at the forefront of species I think about when someone says rabies, but like any other mammal, it can happen. A big concern about rabies in goats is the fact that they sometimes get handled by a lot of people. Recently, a rabid goat was identified in South Carolina, resulting in potential exposure of 9 people.
Is there concern about Brucella canis in Ontario?
- Yes. We have been concerned about this bacterium for a while, particularly in imported dogs and commercial breeders (including “puppy mills”). I can’t comment on the current situation more than to say we are investigating and I’m concerned but far from panicked.
- That said, this is probably not a new issue. A recent study from Michigan reported a low (0.4%) infection rate with B. canis in pet dogs, but much higher rates in commercial breeding operations (Johnson et al. 2018) and a study of dogs is Mississippi shelters found Brucella rates ranging from 8-9% (Hubbard et al. 2018). We know very little about Brucella canis in Canada, but it’s been here for a while at some level.
Why is B. canis a concern?
- This bacterium can cause disease in dogs and people. In dogs, most of the problems are reproductive, such as abortions, stillbirths and reproductive failure. However, a variety of other consequences can occur as well, even in spayed and neutered dogs.
- Human infections seem to be rare but they may be underdiagnosed, as signs can be vague and brucellosis might not be considered by many physicians.
Is Brucella in dogs treatable?
- We can use antibiotics to treat infected dogs, but it’s difficult to be confident that the bacterium is actually gone at the end of the treatment course. We end up having to periodically re-test dogs to see if there are signs of infection coming back. So, we can rarely say “yes, the infection has been cured.”
Do all Brucella-infected dogs need to be euthanized?
- In kennels, euthanasia is most often performed because of the risks of continuing to produce infected puppies and the potential for animals to keep infecting each other. Spaying or neutering is an important part of treatment in intact animals (since the bacterium likes to live in reproductive tissues), and that doesn’t work for a breeding dog.
- For pet dogs, it’s a case-by-case situation, depending on the disease, the household situation, risk aversity, and sometimes Public Health requirements.
What can I do to protect myself, my family and my dog from Brucella?
- If you are getting a puppy, make sure you know the source. Puppies from large commercial breeders, puppy mills or poorly managed operations are the highest risk because of how the dogs are sourced, managed and tested (or, more accurately, not tested).
- If you have a dog from an unknown source, you could consider testing it. It’s hard to say that Brucella testing is needed for every pet dog, but it is reasonable to consider if the dog might have come from a higher risk area (Asia, Mexico, southern US) or a large commercial breeder.
Is testing straightforward?
- No. It’s a multi-step process. Usually, we start with a screening test. If that test is positive, we follow up with a more specific test that is less likely to have false positive results. Then, we ideally follow up with a final test such as trying to culture the bacterium or detect its DNA using PCR. If the first test is negative, that’s great. If the dog might have been recently exposed, we’d ideally re-test in a couple months because it can take time for a dog to test positive after exposure.
Can my dog pick up Brucella at the park?
- Odds of this are exceptionally low. They’re probably basically zero, but in the infectious disease world, we’re rarely brave enough to say “never.” Brucella canis is transmitted most often in kennel situations, through breeding and through infection of pups before birth. Transmission can occur in other situations (e.g. a dog living with an infected dog) but that likely requires long-term close contact. Transient, casual contact (such as at the park) poses little risk.
What about my dog?
- My dog Merlin came from a breeder that we know well. He’s exceptionally low risk in terms of infection with Brucella. He’s neutered, which reduces the risk further. He has regular casual contact with dogs at Heather’s workplace but I’m not worried about that type of contact. I don’t plan on testing him or losing any sleep over his Brucella status. If I had obtained him recently from a puppy mill in Ontario, from out of the country or from unknown sources, I’d consider testing.
Here are a couple of additional good resources on B. canis:
Echinococcus multilocularis (EM) is an important zoonotic tapeworm. The situation with this parasite in Canada (and probably the US) is unclear and evolving. It’s increasingly clear that EM is present in a high percentage of wild canids (e.g. coyotes, foxes) in some regions. What this means for human health isn’t clear yet.
This tiny tapeworm lives in the intestinal tracts of canids (both wild and domestic). People can become infected when they inadvertently ingest parasite eggs from canid feces (another good reason to not eat poop). In people, the parasite can migrate to tissues such as the liver and cause lesions very similar to a malignant tumour. This condition is called alveolar echinococcosis (AE). Treatment can be difficult and, untreated, mortality rates are high (approaching 100%). Also, the incubation period in people is long: it can take 5-15 years from exposure to development of disease.
As we find this parasite in new areas, inevitably the question is: what does this mean for people? Reporting of human cases is variable, and the long incubation period means that it takes a long time to identify changes to the risk to human health. So, if people are at higher risk of AE because the parasite is becoming more common in canids, we may not actually know for years. Lack of human cases is sometimes cited as a reason why it’s “not a big deal.” However, as is frequently argued, “absence of evidence” is not the same as “evidence of absence.”
A recent case report heightens these concerns. Alveolar echinococcosis was identified in a child in Quebec in the spring of 2018, and it’s believed the infection was acquired locally as the child had not travelled outside of Quebec, and the dog the family had previously owned was also from within the province. Foxes were a possible source since they were common in the area and exposure to fox feces in the outdoor environment was considered likely. However, differentiation of exposure from a pet dog or environmental exposure to canid feces is impossible.
One case does not make an epidemic, but it’s one more piece in the puzzle. Ongoing work looking for this parasite in pet dogs will help to better define the risk… more to come on that as the year progresses.
More information about Echinococcus multilocularis can be found on the Worms & Germs Resources – Pets page. Or check out the latest update to the EM infographic from the Ontario Animal Health Network.